eee | ae a | fama es Ln ae | ca << | ae Riba) MYT Tr im ea i WE) 0 0918s eS LIBRARY Michigan State University PLACE IN RETURN BOX toremove this checkout from your record. TO AVOID FINES return on or before date due. MAY BE RECALLED with earlier due date if requested. DATE DUE DATE DUE DATE DUE 6/01 c:/CIRC/DateDue.p65-p. 15 it mt eae Or A NIKCTY FOOT RPINFORCED CONCRETE GIRDTP BRIDGE/ A Thesis Respectfully submitted tO The Faculty of Michizgan Azricultural Cclleze Ny Yj rraest Le ranekiley A caniidinate for B. =. De .ree in Civil Engineerirs Jume, 1922. Foreword In pesparirge this werk the author is sreatly indebted to .r. *.M.Orand, Anst.rridze “nolneer cf the :ichlia: State “jrhwey Lepartrent, ani Associate Prcefesasor C.L.Aiien of Civil Tngineering Pepartrent cf Michigan Agricultural Colles. The author is also under cblizaticn to ir. C. A. Relick, Sridce Engineer of Lichigan State Uichway vepartner.t, for hia kird assiasatarce in obtainirs certain copies and Juplicat:s3 of raterial herein containet. Thea author has aleo drawn rust freely for his au- therity from tha Concrete Frzineer's Mardbock, ool x Johnaon, tezether with inforraticn from Ketchum's Eridjs Ergineer's rai 2ocok, Hool & Whitney's Concrete Dealzener's tarual, sark'sa Mechanical Fusineer's Handook,Carnazie's Packet Cor ,anicn, -errinan & Jaooty's Reofs and Pridgee, Parts I &@ III, serrizants Anerican Civil Snginesr's Hardbocr ag Foyi's Strensth of sa- terials. 102705 Table of Contents Foreword Tabse c° Contenta Intrciuction ctandard Notation in Flexure ror:.ulae Analyaisa of Stress38 on Floor Slab Forrulae for analysis of rectangular coars, As designed Ase a new design Acalysia of the Girdor Computation «f loading Corputationa of ard eeactiona Corputaticn of beniing morent at the center Computationa for fo acd fa at the crnter. Corputation of berndins moment at critical section Corputation Yor fa and fo at critical section Conclusions The Appendix One copy of Fichigsn State Highvay Bridge fpecifica- tious --1920 Sheet 1 = General Details Sheet < = Par Li-t and Detaiia n 3 = FaiserorK n fete ——SSS SS Tntrosiustiens tTh@ origua, ths anslysia of which ia herein containei, ia & Ce foot ruinforocel conereste cirder ortidce of ats .fsrd Avedon rscerntay eaucrptsid cy tre eleorndiocsn “bate Hilposay Losurtsent. nCaseaacd, 1t Ls exvected to C8 ubei On ail Concrete Uria.za COLUULUStLES C¥ Ble isparteunt, over ov fast din lensthe Thiea pursticusar orisoce bare enalyrtai da nuow © Jurg,do--, in tie crocesa Gf sonoptruction. It ia Enown as Trunk Ulina Pritllg obo v,oe",ereseins the Leorl Claga Piver on Trunk Ling Paselt oatweon Laosinw asd Cr forn. The nite isa sbout ora an. tirssefourt 3s milea northeart cf Petit, Taa.et, Tu Ne FT OM, eaeat) Tosnehipc, Clinton Ceourzty, Pichioar. Toad ear tventa are rainfcroal concreta, Boad Cver We... silos a: i arg 24 fret faep fren the croren cf the roadwsy. 11.48 pial evantuaily pereit the dreaiviiz, cf the river to @ gerth CF tan Teoat below the preeert river tes. The abuts e.to ere cele tai with thea aid of o CLdat of «cod aecerding te sp efivean in the river vet. It ia re eiboice torres cr five pouringae a" wh Chpeiedi roaivuny,ts the oe cour@i firat. This dy axcepting «a t.g@ jirégecr corrreseton Feces which olfer ghre end eac itself is recuired to necifications,over wecdon guirel thet it de wurst tar |i h 2»utre e OS poured in a formscru widies an cn poured in tnree,one 4 aur trea reudwsy,ise over tne winicws in rai after the ond o = Sac nt ds pours. ~~ sirder ani section of the roadway *a3 been pourei. When five pourinze are rade, the briize ia poured in quarters, tne joints bein: rade thru the canter line of the roaiway and transversely “et the center. As te the bride itself, it isa virtually an crizinal ie- Bion aeveloped principally by Mr. Melick, forserly a Professor in the Civil Engineering Department of Michisan Asricultural Colle-e. It is believei that the concention of the deatian of thia triise, or more truly this cirder,for the floor is a re- irforcei concrete slahb,crew from such reasonirz an follows; Concrete beav~s under uniform loadinz, are designed of uniform cro33 section for maxirus. vanding roranta at the center,and hence grow 2x0essivzey heavy and uneconomical towrds the enis. The graph of the banding moments of a bear uniformly loaded, Closely approximate a parabolic curve. If the compression face of the beam can be designed to closely follow the line of a paraticin, it should be both safe ani economical. Such a beam or girder would be nearly straight on the tensile face and hence would nive greater stream clearaace. Also it could be designed by the formulae ki.own as the Straight Line Theory and any arch action that misht be engendered by rea- gon cf the ourve of the compression face of girder woud Gil ce or the siie of safety. The theoretical difficulty that had to be met was the va- risgtle dead loads due to the varyite depth cf bear, and the prac- tical difficulty of awaying the staid and settled ideas of the Clder heads in conatructiohn. Vr. Kelick overoare both these these obstacles and a criize of this type has been carryinz, traf- fico for sevral rontha at this time in June, 1355. Standard Notation for use in Flexure Forrulae. Rectangular bears. Ean 6s ~@ Ea ' Ee += jogs fede ne- Co’ § {4 t am tensile unit satress in steal cerpressicn unit stress in concrets rodulus of elasticity of ateel rmcdulus of eiasticity of concrete 1.8 EG mprert of resisatarce,or bending monent in ,sneral eteel erea creaith of ear depth cf besm to center cf steel ratio c& depth of neutral axis to depth "d" depth below tor to resultant of the corpressive atresses ratio cf lever arm of resisatinz coupls to depth nan d=- @ arm of reaisting coupie - 6tesl ratio As bd Shear,Bond and Web Reinforcement a2noed< total shear shearing unit stress bond streee r-r unit area of bar cirdumferehoe cr perimeter of bar horizontal spacing of reinforcing members Beans. Reinfaced for Compression area of compressive steel steel ratio for compressive steel cornpressive unit in steal total compressive stresa in conorete total compressive stresa in stecl devth to center of compressive steel depth to resultant C and C! Analysis of Stresses in Flocr Slab. "The sunration of the moments of all the external forces abcut any point on a beam is calied the cending ronment." The idea of bending moment foum above and the flexure formiae made standard by the joint cormittee ahd based on the straight line theory of stress distribution, comprise the principal nears used for the analyaia. These forrulae as they apply to rectangular bears are grouped here. Loading requirements and limitations of stresses will pe found of 19380 in the apperdix. Rectangular Bears k= Pepa tea)? - pn - a7 = pn Po) pon= 13s + j= 1-1/3 % WS nfo 4 fs P=Ae = fs (fn4 1 - Tea Ye Feb 2) = gig 2 : 3 = 3oM or fo = 3 Mo - i fo k3 ba) fo kj, “Fk jod® ba - a2 a i 8@=- p fs j (oa )- Pp fe j, or fs = As ja fo = _2fa p or f3k K n{(l = k) C AAs /e Aaa Bat Ss k a : 1 peo oS X0- Fie, Wats 43ad CBB f= yawo7 44 eee aT? a} 5 Lf i SAE TAAL a 59/0006] As Designed 12 tons live load pilus 25, impact - 15 tons per truck rear axle or 15000 lbs per truck rear wheel concentration live load = L.L. Longitudinal distribution cf L.L. = l'.o SU" of span (. ecient Spec.) 1'.5 #& .6 X 2u'.0 = 13'.5 distribution in sirection of center line of roadway. 215000 lba - 1110 lba.rer lingal foot ef britce 13'.5 Nead Load = D.L. Bt.of 1' of alab = 1.'8° (svernve "a") ¥ 71'.% X 150 lw - 4105 less wearing surfsce «= 22 lhsa.per square ft.of1" thickness = i" los Total D. Le. 48¢uU lLbe. D.Le. = 1/6 wi%= 4330 lbs X 21.'2 Yo = 14,510 ft. Lbs. v1. Totel Moos 24,640 " t n- 12 (¥.S.H.Speco) P As gieo sq in - .vuss bd iz" x 14° kK Vax 12> X 20095 # (.0So X 18)A -.00835 X12 = 2377 = x = for 2 X¥ 24840 X Le - 773 ~o77 X B74 XK (ip X le fa - 584810 X 12 = 15290 oe??? KX 6574 X 14 Vax.V.-_ GocO ft.loa. Ve V- 3000 . | ~ bjd 12X14 X 0674 2 17.5 No “eo reintercenent : eedead. floor Slao Corcuted as 4 Yew Desig: under 1 .8.h.Spec. Tota. V.-as fount - e460 ft.Los. using levov lt.steesl - fa n= 12 612 los. = 35.5, of 35u0 los. -fe k = nfc = 12 X¥ &12 = 9744 = ew tk ntcée felt KX tle % leuvu =2744 5 Pefek - S22 X 2678 2 wuts ° fs 83080 x ap fe j - .O0f6 X¥ 15000 X .f74 - .134 ; XM; — | }- fre 0134 KX 13 Adiin:z 3 arbitrarily - 1.4 in. #12.¢ in. 6 14" »v0S6 X¥ 12% 14 = 1.51 aq.in.steal 144 rcdie 1 in.sq.spaced in 90 ft.- 1.6 aq.in.rer ft Biade Max Ve 3500 ft.loe. v = _2urYd -~ 17.5 Yo ved reinforcesent nezae Vv Qi: - bid i> X 24 X.€74 Anal. ia o1 is Girder The uniforr loaxis on the sirier consist cf the loai derived from the flocr slab, the load of a section in the girder con- taining the tensile atee:, ard a uniform live load cf 100 lbs. per square foot of roadway. This live load is found to be greater than the maxirum loadin: possible by the use of lines cf 1@ ton motor trucks. The area of cross secticn on concrete containing the tensile eteel ie: 3 #t.7 in. X 2 ft - 7.16 aq. ft. 242 =" X 1Gz in -l.ce 8 i Tcetal 2 ee tt G&.°4 X lou lus. = ic?o lvs.per lineyfal foot. et.of 1 ft of slab plua wearing surface for 4 bridge - 4GE0 its _ te dLo bO8ep Sr dine rt. 3 Total uniformly @fatrinetion DL = 2115 $— 1565 - [441 lbs per lin.ft. The weicht of the remainder cf the girder was obtained by dividing it into sections. The area of each section was then four end multiplied by the thickness of certain parts. Ynen these re- Bults vere aided and rultirplied by the welzht per cubic foot of concrete, the weisht of the section was closely approxiratei. Con- siderinz this weizht concentrated at its center of gravity per- mitte: ins assumption cf a series cf concentrated loadsa on the cirder. Following this,the r’sht and left end reaction® were obtained as for a tenr rith both uniform arid concentrated ic.13. Solution of the bending moment at the center and critical section taken about one foot towards the center fron the inner end cf the coroal is next taken ahd the tests nude “or streag“3. Computation for weight of section of Girder. “tedieht of Secticn A concentrated at 1 ft. ¢$ in. fros cer.ter line of zirder.. 1v a .o aX ‘ = 4463 ad e ° 3 ge hee aed Gg ae GaP S f 93:83 tt a”°" 3" X¥ 2" oO" KY" 48 we = teu * " Total 34.08 cu.ft. 34.08 ¥ 150 lba.per cu.ft. = 5114 lts.at 1 ft.3 in. left oc? center. Waitcht of Section B. 1Q ft.7 gn.¥ of x ~ * 4 in. = + 7. oy.ft. garg weed Oo i *o' Bea 2+ i: "oof Totai 70.0 " * 70.Q ¥ 150 - 10,500 lbos.at do» ft left cf center. Veleht of fection C. ft .8in. x DS ft 7 in 9 f Xlft4in- # 71.c ou ft on" 6 ff &XF¥ 5S*# P? W*F¥ QO *F BG 8 mw gf YS02 * * 1" 3" X¥ 4X0 *" ¥ LT" 4 We = 7.4 +" #9" Total 77.5 Cu Ft 77.5 X¥ 150 — 11,525 lta.at lu ft 4 in left of center. Telgsht cf Secticen D. ft. " C2 © in X " xX mmo ft.C dn.X 1 ft 4 in + £5.53 cu ft rou" XO "ER 418.07 #*" * Totaz 104.00 " n 1U4 X 150 = 15,00 lbs.at 17 ft 1 in left of center. qi oy Waight of Section E. 2 ft.4 in.X 9 ft O in.X 1 ft 4 ins 2 cae ae yeh om KON EF = 1 Total 73 ~=*°" " 7973 ¥ 150 - 11f8O lbvs.at 25 ft 7 in laft of center. ft. f 22 cu.ft » O- wel set ef Section =. 4 it.eo in. X¥ 5 ft.C ing ¥ o Ft ob in. = fF 47.9 cu ft R™ a: ™ ¥ 8 $ " e = +172" 7" re GUM Kl o CUed vYel XK id = 7,025 lds.at 3° ft & in left of center. Df} Lin ¥2 ft Cir YE ft 4 in - 55.69 cu ft 3" Gg" XB" CO ™ KE" 4" SF Siz om Total 107.¢ 407.2 ¥ 150 = 15,185 lia.at co ft & in left of center. Usain, luv isa. per sq.ft.incluiins inp: ct,trhese resulta @ live loai - 10 Left Reaction W B= 4441 lds. X 32 aol€&5 " X f{- SOl5 "* X e- LLEFO 7 x d\|} 15,0600 * X Ce ll,ods * x f- 1,500 " x a- J,ila " X alt= o,113 " xX b' © Lle,ovuuo " xX cf = li,svs " X d - 15,000 *® x c' 2 i1,€50 * X f' - 3,vls x 3! = iv, LES x BS y0G7 099 se? 7 67 Right Reaction - 273,580 lbs.because X 1U0 = &7.07 ft X 43.835 ft &3.5 75258 6° ..43 50.62 54.17 48 ,F3 45.08 42.58 48.63 43.9 200679 18.695 11.08 4.17 10CO los.pur iin.ft.of zirdar. doe detedegedeqedegededetegets - 273,3€0 lbs. of COO, S42 €24,472 $50,04C 638,449 ols, 400 £30,901 217,771 407,000 5£6,438 417,300 Alo,&10 LOC , 067 67,490 $3,957,655 symmetry. 17,054,840 ft 1,351,446 "t " " zs 37 @322323232 232 «232 23 elisa. fi " " " " " n " n n " " ff 0 " Comrutationa for the Feniin:; 273,380 los. X 43,83 ft. = 14,085,850 ¥inus 4441 los. X 45'10" ¥ el! YL"- 4,463,760 oll2 * X a or - 6,950 iUSuUO * X of or = 33,9000 dlofo " X¥ Jdut 4" = Lis ,480 15c00 * X 17' 4" - 265,448 LLEEOQ " X eo! 7" - 503,890 VUls" X¥ 35? On - A535 ,940 Lol&5" X 3' BN - 541.9060 5,049,670 11,983,250 m 5,049,570 6,053,540 ft.loa.&.M. at center or t WOR art i Ae A le @ b-f =,9t ‘wrers OUI ELYT PoOT satel MOYIC ¥ : & ’ - GE « «Gl / . J. 47 66° " GIO6 =. Z 756 » «OZ81/ = lil o 60 OOIG/ = P O57 os « S65// s ? IAG »« » OOF: F ~ | Fee wee,l Pm 2 GIIS = » rf -uy aed $41 [yyy = Me Mm WOOT a a / 7 T a] PPT Ty o At center of Girder d - 14' OF = G2" - 152,59 k = 1 1 | l*#f3 = 1#16000 = .357¢ nfc 12 X €13 ki = depth cf neutral axis - .979 X¥ 159.5 = 52.6" No. Dau Unit Total Lever * of total stre>s Stress Streas Arr. Adout the tir 1 oa" KX LO" - £54 aq in .w° ?fe 7o.éefc 57" TvVLl.e fe 1 €34 0a: 1s 4a7fo E94 ,fF%¢e LE" 25 Uu.2 fo 5 4XOxes = 686 cere Lou.lfe ob" Sidc.afe 2 vjo sq in Solfc_135.°efs 14" 'CC.o feo 706 .Ofc i*¢4i.5fe NN xX 2 = Tummation P'x 13941.5 fo ~ «~ ~ z2 7UC fe 7. aie fo yous 1€.3 S om Loo .o® - 18.3 = 141.2" = ja 159.5 The stresses at the center of the girder vere then sciveal oy the formulae cf the straight line theory."d"*,"k" ard "kd" are firet found in order. Then on the theory that the total etreas in the concrete multiplied by a distance will balance the moment of total stress ahout the top,a method was found fer deterrinin: the distance "7". The area of certain sections waa taken and rultiplied by the unit atress for the sectior. Ti:is gave a total stress and when rultiplied by its lever arr about the top, projuced the moment of the total streas about the tor. Then when this was completed for all the sections,tve num ation of total stresses times "2" mornents of total stresses. The solution follows: fo - 3 02,950 = " 923 fa - 75,402,950 - 1¢,4C0 j1.55 141.2 W&s "7 £28 tren founid abd tran equated to the sur-aeticn cf 8 A % es > av Neulra ie ik Computation *or Girdjer at Critical Section. At the critioal section,the area cf steel in beth tensiis and corpression face was taken into acccunt ard hence Aes ard A's were obtained first. Then by entertaini:: the facter "ki," an equation was obtained balancing the stresses in the teusile race. Solving the resulting quadratic equation gave a vaiuse for "kd" ana the use cf the straight line formulae trouzht the rest of the re- sults. A's 31.25 aqein. A's 14.06 Cne "n*" of concrete taken by steel in compressicn face. As to concrete - 1lé X 3l.eS = S75 S75 (57.5 = kd) = 1bi.cd (kd-6) @ kd X 24 X kD 12 kd2 1 530.66 kd = 37490 -- O 2 Fd = 53.66 + osu cute ze X37 220 a4 rd = 913.2 = 37.9" R4 kK - 37 .c" _ ee o7.5 3 - sa4- kK & —C7L 3 For Fending Morent at Critical Bection 873380 X 14875 = 4,038,555 Minus cyudd loa.X lea'?o % 7' 45 = 4€G,700 16,155 ioe.X 1OL7" = 171,237 vVy¥lo ats. ctecn 65,006 631,743 4,033,355 = 601,745 = 3,340,612 ft.lbe. -OF 40,057 344 ii.ats. fa-_M == 40,067,244 = 15,100 AS ja 21.25 K £4.92 fos fok - 15100 _X .389 = 805 ~ TaCiek) 1s X oll Max.vertical shear et the support - 3S735% lets. V= —_V = 773350 =- 164 ide. oja ax X JO v(¥.c.4.Sped)—- 12% of compressive strength of concrete,- 13% of 2500 lbs. =- 300 lbs. In this caes "ja" is purely a matter of experience,out consultation with the designer of this bridse disclosed the fact that "jd" taken equal to 7Q inches wae considered very con= gervative indeed. Conclusion Extensive study and consultation with the desizner, com- puter, c.cstructicn angineer, inepeotor, and constructor of the oridge mentioned as constructed near Tecumseh, has convinced the author of the entire applicability of ths structure. Comparison Frith other concrete jiesigne for the save span and clearance has proven concluaively the econoery cf the itesign. At no point in the structure are the stresses in the concrets exceeded. The etress in the steel never excedéds 1:,400 ard it has beooma common practice in many canes to perr.it the stress of 16,000 and sv, GUL pounds ror steéi preperly bedicd in concrete. Hence under the @scunption of a satisfactery inspeotcr in charge, it 1s a very sutiafactory bridge. Ani last but not to be disregarded, is the strong appeal to the esthetic sense derived from the gentle curve cf the top of the girder. Kone can deny the supreme beauty Of the weil designed arch and a near approach is here made to that curve. It stands the test of analysic, it has an appeal to the senses, am above all it has been built,and stande the test of utility. GENERAL SPECIFICATIONS for STEEL AND CONCRETE HIGHWAY BRIDGES and SPECIFICATIONS FOR MOVABLE BRIDGES FOURTH EDITION 1920 MICHIGAN STATE HIGHWAY DEPARTMENT | LANSING, MICHIGAN Contract No................. CONTRACTORS FOR BRIDGE CROSSING SECTION..... 0.0... ceccceceee, TOWN... .... cc cecececeecee. N RANGE... eee. W bbb bebe cb cnenes TOWNSHIP : eeneeeeae. ooo cee cee ceesee..e. COUNTY GENERAL SPECIFICATIONS for STEEL AND CONCRETE HIGHWAY. BRIDGES and SPECIFICATIONS FOR MOVABLE BRIDGES FOURTH EDITION 1920 MICHIGAN STATE HIGHWAY DEPARTMENT LANSING, MICHIGAN FRANK F. ROGERS, C. E., State Highway Commissioner. C. V. DEWART, Bridge Engineer. C. A. MELICK, Consulting Bridge Engineer. General Clauses. 1. Blank Forms.—Al! contracts, proposals, bonds, etc., must be made out on blanks furnished by the | State Highway Department. Additional blanks or blue prints may be had by Contractors upon request. 2. Familiarity with Conditions.—The Contractor shall make himself familiar with all details shown on the plans and conditions at the site, and shall refigure all bills of material or estimates:‘of quantities shown thereon before submitting his proposal. D> Concrete Bridges.—All concrete work will be designed and detailed by the Michigan State Highway epartment, 4. Stress Diagram for Steel Bridges.— Bidders on steel bridges will submit proposals accompanied by stress diagrams and general drawings, showing live and dead loads and other forces used in calculations, material, shape, size and all other characteristics of the structure; the make up and gross and net cross sectional area of each member, and the maximum stress therein, total, and due to each class of load separately, being careful to show lateral and sway systems and the stresses therein, floor beams and stringers and their connections, make up, gross and net flange and web areas and the stresses therein due to each class of load separately. The stress diagram shall also show enough details to indicate the general intent of the work. 5. Engineer’s Drawings.— When stress sheets and general drawings are furnished by the Michigan State Highway Department, they shall be followed in detail except in so far as the details governing method of erec- tion are concerned. Any substitutions of details shall be subject to the approval of the State Highway Com- missioner. : 6. Drawings for Steel Bridges.—Upon the acceptance of the proposal and the signing of the contract for steel bridges, the Contractor shall submit two (2) complete sets of blueprints of working drawings for the- approval of the State Highway Commissioner and no. work shall be commenced or material ordered until the- ' working drawings are thus approved. If the State Highway Commissioner retains such drawings more than one (1) week from date of their receipt it shall entitle the Contractor to an equivalent extension of time for. completing the work, provided the Contractor notifies the State Highway Commissioner of the delay. The- Contractor will be expected to furnish free of cost to the State Highway Commissioner complete sets of approved working drawings and stress sheets as the State Highway Commissioner may require. In addition, the Con-- tractor shall, upon the fulfillment of the contract furnish the State Highway Department with a complete set. of all tracings pertaining to their contract. | 7. Name Plates.—For concrete bridges the Contractor will be furnished with a plate to be set in the con-— ctete in two conspicuous places as he may be directed. The Contractor’s name will appear on this plate and the use of any other name plate or advertisement is forbidden. | 8. For steel bridges one or more cast iron name plates of an approved design shall be furnished by the Contractor and bolted to the superstructure at the point or points specified. For trunk line bridges these shall bear the inscription ‘‘Trunk Line Bridge, built by State Highway Department, Frank F. Rogers, Commissioner,’’ also the number of the bridge, the date of construction and the name and address of the Con- tractor. Details of Reward Bridge” name plates will be furnished by the State Highway Commissioner. 9. Liabilities of Contractors.—The Contractor shall maintain sufficient guards by day and night to pre- vent accidents from travel or by any other cause incident to the performance of the contract and shall be liable for any damage which may arise from his neglect to do so, or from any omission on his part or on the part of his agents. : | | 10. The Contractor must construct barricades and guards to prevent accidents to travel as he may be direct- ed, provide proper detour signs, and also hang out red lights by night all of which must be left in place or main- tained until permission is given to remove. Barricades and lights shall be placed not less than 50 ft. away from points of imminent danger to vehicular traffic. In addition to red lights the premises shall be kept. illuminated by carbide lights so disposed as to cover the entire work from barricade to barricade or such danger zone limits as the Engineer may designate. | 11. Patterns.—It is understood that all patterns shall become the property of the State Highway Depart- ment upon request of the State Highway Commissioner. } ‘12. Special Erection.—Special permission shall be secured from the State Highway Commissioner in writing when it is proposed to erect a structure in such a manner as to bring upon it concentrated loads other than those for which it has been designed—such as might be due to floating to position, or erection by canti- lever method. This is particularly to insure against applying load to a structure in such a manner as to reverse tension members. | 13. Commencing Work.—He is to commence and prosecute work on the bridge as he may be directed to by the State Highway Commissioner within ten days from and after signing the contract, and shall prosecute the work rapidly and continuously in accordance with the best modern practice unless delayed by orders from the State Highway Commissioner. | | 14. Time of Completion.—He further agrees to complete the work on or before the date specified in the contract and to allow the liquidated damages to be deducted from moneys which may be due him. Provided‘ however, that the State Highway Commissioner may extend the time limit for the completion of this contract upon the recommendation of the Engineer in charge, giving satisfactory reasons for such extension. (3) 4 GENERAL CLAUSES & 15. Force.—The Contractor shal] begin work as specified in the contract, and he shall at all times thereafter employ such force and outfit as will, in the opinion of the Engineer, be necessary to complete the work within the contract time; and if he fails to begin work at the proper time or to furnish materials or execute the work in accordance with the plans and specifications, or fails to proceed with the same as rapidly or in as workmanlike & manner as the State Highway Commissioner shall deeem necessary in order to complete the same within ‘the time limit; then in any such.case, upon ten days’ written notice to Contractor, the State Highway Commis- :-sioner shall have the right to annul and determine such contract and enter upon and take possession of the work and complete the same either by reletting or directly under the charge of the State Highway Commis- ‘sioner, and if the cost of completing the work in such manner shall exceed what it would have cost under the contract, such increased cost shall be paid from any money on hand for work under this contract, and if that ‘be not sufficient then such increased cost shall be met by the Contractor and the sureties on his bond given to ‘guarantee the faithful performance of this contract. . 16. Stakes and Monuments.—The Contactor shall be required to preserve all stakes and monuments established on the line of the work until duly authorized by the Engineer to remove the same. If any monu- ments or stakes marking the boundaries of property along the line of work have to be removed in the process of the work, the Contractor will promptly notify the Engineer in charge so that he can properly locate and reset the same after the grading is complete. | 17. Maintaining Travel.—The Contractor shall preserve the roadway on which he is working from meedless obstructions, and also in case of a bridge crossing a stream or thoroughfare of any kind he shall conduct his operations in a manner which will not in any way interfere with or jeopardize the safety of the travel. He whall have the right, however, to close that part of the road on which he is working to travel whenever other woads can be traveled without serious inconvenience to the public if given the written permission by the State Highway Commissioner. 18. For temporary traffic the contractor shall provide a width of roadway not less than 10 ft. in the clear. En the case of embankments or stream crossings, said roadway shall be protected by an exceptionally strong wailing or hub guard. The roadway is to be maintained in good traveling condition at all times for as long as the need exists. | 19. All designs or schemes for maintaining travel must be submitted to the State Highway Commissioner for alterations or approval. | 20. Accidents.—The Contractor shall so conduct his operations as not to interfere with the work of other Contractors working on the same or adjacent work. The Contractor shall assume all risks of accident to men, material, or structure in place prior to the acceptance of the finished structure. 21. Payments.— Payments will be made once a month on the basis of 80 per cent of the Engineer’s estimate for work done and material delivered. For steel bridges a payment of 75 per cent will be made on delivery sand the balance paid when bridge is erected and accepted. : 22. Proposals.—aAll proposals which contain bids not asked for or that other-wise are not in conformity with the specifications will be rejected. Each proposal must be accompanied by a certified check drawn to the order of Frank F. Rogers, The State Highway Commissioner, in the amount of the specified lump sum or un the sum of five per cent of the proposal, conditioned, that if the bidder or bidders to whom the contract is awarded should refuse or neglect to execute the contract or furnish security the adequacy and sufficiency of which shal] be approved by the State Highway Commissioner within ten days, then in either such case all or that portion of said check which shall be necessary to compensate for the liquidated damages caused by such refusal or neglect shall be retained by the State Highway Commissioner and become the property of the State of Michigan. 23. Checks Returned.—Checks shall be returned to the unsuccessful bidders after the award of the contract, and to the successful bidder after the execution of the contract. 24. Right of Rejection.—The State Highway Commissioner reserves the right to reject any or all proposals or award the contract as he deems advisable for the best interests of the State of Michigan. 235. Bonds.—Two bonds furnished by a surety company doing business in Michigan shall be required of of the Contractor. One in a sum equal to the consideration to be paid under this contract, guaranteeing the faithful performance of the work in accordance with the terms herein, and the other in a sum equal to the ‘consideration to be paid under this contract, provided that said bond shall be for a minimum sum of $5,000, ‘Zuaranteeing the payment of indebtedness incurred for labor, materials, or any cause whatsoever in fulfilling this contract, it being expressly understood that the latter bond is to include any liability of the Contractor, ‘through the execution of this contract, arising from the provisions of Act No. 10 of the Public Acts of 1912 ‘extra session), as passed or thereafter amended. 26. Subletting.—The Contractor agrees to give his personal attention to this contract and not to sublet the same or any portion thereo ’, without the written consent of, and subject to the conditions stipulated by the State Highway Commissioner. . 27. Instructions to Foremen.—The superintendent or foreman of any particular portion of the work . shall receive and obey the instructions of the Engineer referring to that particular part of the work in case the Contractor himself is not present. : . GENERAL CLAUSES S- 28. Incompetent or Disorderly Workmen.—Any foreman or workman employed by the Contractor or by any sub-contractor who, in the opinion of the Engineer or his authorized assistant, should not perform: his work in a skillful manner, or should be disrespectful, intemperate, disorderly or otherwise objectionable, shall at the written request of the Engineer, be forthwith discharged by the Contractor or sub-contractor employing such foreman or workman, and shall not be employed again on any portion of the work provided for by these plans and specifications without the written consent of the Engineer. 29. Imperfect Work or Material.—All insufficient, imperfect or damaged work or material when pointed out at any time to the Contractor by the Engineer, or his authorized assistant, shall be remedied immediately and made good, or removed and rebuilt, or placed to conform to the plans and specifications, and any omission by the Engineer or his authorized assistant to disapprove of or reject any such defective work or material during construction shall not be deemed an acceptance of such work or material, nor shall such omission om the part of the Engineer be construed as in any way releasing the Contractor from remedying, replacing or making good any defective work or material so as to conform to the plans and specifications. 30. Changes in Plans.—The right is reserved to make such minor changes in the plans and specifications as are not otherwise herein provided for, as may from time to time appear necessary or desirable, and such changes shall in no wise invalidate this contract and shall be paid for at the unit price as quoted. Should such changes or any other changes be productive of increased or decreased cost to the Contractor for which there is no price quoted in the contract, a fair and equitable sum therefore, to be agreed upon in writing before such changed work shall be started shall be added to the contract price and in like manner deductions shall be made. 31. Extras.—It should be thoroughly understood by the Contractor that extras shall be allowed for only when granted in writing by the State Highway Conmissioner. | 32. Extra Foundation Work.—Should it be found necessary in the judgment of the Engineer to increase or decrease the depth of the foundation not more than three feet from that shown on the plans, the thickness: of the wall, where said wall joins the footing, shall be increased or decreased the same amount per foot as the main wall increases per foot of its height as shown on the plans. This shall not be understood however to apply to arch abutments. For this latter type of construction special instructions shall be furnished by the State Highway Commissioner for modifying footing designs. _ 33. Lines and Grades.—Lines and grades will be given, when requested, by the State Highway Com- missioner. 34. The Contractor will be held responsible for the line and grade of all bridges, elevation of bridge seats. and accuracy of camber and arch curves. He shall satisfy himself, by test piles if need be, of the value and stability of his piling. Deviations from line, grade, or cambers or arch curves greater than one inch shall be- deemed sufficient cause for rejection of the work. 35. Clearing Up.—The Contractor shall leave the bridge and premises in a neat and presentable condition. and remove and clear up all rubbish and surplus material and leave the waterway unobstructed; and where it has been necessary to remove an old structure, the material from the same shall be neatly piled on the bank,, where it may readily be loaded on wagons; it being understood that said material may be used by the Contrac- tor in the erection of the new structure and that any material removed from the old structure and not used in the construction of the new bridge shall remain the property of the original owners unless otherwise specified. 36. Channel Changes.—Channel changes whenever shown on the plans or made necessary by the loca- tion of the new bridge must be done by the Contractor out to the full width of the right of way, but any changes: extending beyond the right of way will be done by the township or county or be handled as an extra to the contract. The channel must be cleared out to the full width and depth under the new bridge. 37. Backfilling.—In all cases after the masonry is built up the remaining openings of the excavation shalF be backfilled up to the original contour of the ground with good material well rammed into place. Any surplus material shall be placed in back of the abutments where it may be covered by the embankment. All new bridges must be restored to travel however, before final payment. This may be accomplished by a temporary approach span, by restoring the old bridge as approach spans for the new bridge or by making enough of the back fill to provide a 16 ft. width of shoulder and not greater than 4% grade. In arch construction the Contrac— tor shall make the back fill, depositing same in 8-inch layers, carefully rammed according to the instructions of the Engineer. He shall place the material in such places and in such order as required by the Engineer. Said backfill to extend to full roadway grade set by Engineer for a length of roadway extending between tip of ex— treme widths of abutments whether of flaring or straight design. The fill may slope away from said extreme limits on a slope of 1) horizontal to one vertical. 38. Removal of Existing Structures.— Removing existing structures, if any shall be done by the Contrac~ tor and included in the contract price. 39. In removing existing structures the Contractor shall carefully and clearly mark all members of the structures before dismantling. Upstream trusses shall be marked using symbols U, M and L for upper, middle and lower panel points respectively; Downstream trusses shall be marked T, C, and B for the top, center amd bottom panel points respectively. Panel points shall be numbered consecutively from one end to the other end of the bridge... Marks shall be both painted and stamped with steel dies. All pins, nuts, fillers, pin rings: etc. shall be clearly marked and all loose parts shall be either strung on wire and attached to connected parts or they shall be neatly packed in a box. All pin holes and machine parts and surfaces shall be painted with a mixture of white lead and tallow. oe 6 FOUNDATIONS 40. Load Tests.—Load tests on portions of finished concrete work shall be made where there is reasonable suspicion that the work has not been properly performed, or that, through influences of some kind, the strength has been impaired. Loading shall be carried to such a point that one and one-half the calculated working stresses in critical parts are reached, and such loads shall cause no permanent deformations. Load tests shall not be made until after sixty days of hardening, 41. Engineer as Referee.—It is agreed by both parties to this contract that the Engineer shall act as referee in all questions arising under the terms of this contract between the parties thereto, and that the decision of the Engineer in all such cases shall be final and binding upon both alike. 42. Definitions.— Whenever the words ‘‘State Highway Commissioner’ are used in the contract it is understood to mean the party of the first part to this contract, or other authorized representative limited to the particular duties intrusted to him. 43.— Whenever the word ‘‘Contractor’ is used, it is understood to mean the person or persons who have entered into this contract as party or parties of the second part or his or their heirs, executors, administrators, successors or assignees. . 44. Whenever the word ‘‘Engineer” is used, it is understood to mean the Engineer for the Michigan State Highway Commissioner or his authorized representative. 45. Whenever the word ‘Inspector’ is used, it is understood to mean the person employed to perform such duties as are herein described as duties of the Inspector. Foundations. 46. Character of Bottom.—The material of the bottom upon which piers and abutments must be founded, may, for the purpose of these specifications, be divided into the following classes: a. Roc b. Hard ground; as hard-pan, gravel, compact sand held laterally, or hard dry clay. ce. Soft ground; as soft or wet clay, silt or mud whose sustaining power must largely depend upon the frictional resistance of piles or upon piles driven through the soft material to an underlying material of a harder character. 47. Rock.—Where the site of the foundation is on rock, it shall be cleared of all overlying soil or other material, all the loose and distintegrated portions of the rock removed and the resulting surface roughened to a depth of six inches. When the surface is inclined it shall be levelled in steps to prevent any tendency of the foundation to slip. | 48. Hard Bottom.—lIn hard ground the material shall be excavated to a depth below the action of frost or scour by surface currents, with a minimum depth of 4 ft., if above the water. For foundations in the water the excavation shall extend a sufficient depth below any possible scour by the river currents to give the piers sufficient foothold to resist displacement by the shoving action of floods, ice or floating material. Inno case, however, shall the foundation extend less than three feet below the bed of the stream. 49. Where the foundatons are on or near the banks of streams or on sloping strata they shall be carried deep enough to insure them from slippng by the sliding of this underlying material. 50. Where the material is liable to be softened, scoured or undermined by water, or where foundations cannot be carried deep enough to be beyond any possibility of beng affected by scour the bottom shall be piled. 51. Soft Ground.— Where the foundation is in soft ground, the material shall be excavated to a stratum of hard material or else it must be excavated to a depth where the soil is permanently wet. if on land, and below possible scour, if in the water, piles may then be driven as shown on the plans. 52. Timber Work.—WNo piles or timber shall be used as an essential part of any foundation above the water line or in ground which is not permanently wet. 53. When the Contractor, in order to faciliate construction, uses timber in such a way that it can not be removed, it shall not be paid for nor shall it be allowed to be so placed as to occupy space for which concrete is shown on the plans—nor shall it be considered as concrete. 54. Steel Work.—No iron or steel work shall be used as an essential part of any foundation i in direct con- tact with any kind of earth or soil or in any position inaccessible for painting and cleaning except where imbedded in concrete. (55. 4 Piers.—The tops of trestle or viaduct piers on land must be at least 18 inches above the surface of the groun 56. Pedestals.— Pedestal tops shall not be less than 18 inches square. 57. Anchors.— When sepcified on the plans all anchor blots and anchors shall be properly placed and built in by the masonry Contractor, the material for the same being furnished by the Contractor for the metal work. 58. Piles.—Piles shall be of any sound hard timber that will stand driving, free from loose or rotten knots or other defects which would impair their strength or durability. They shall be at least 6 inches in diameter at the point and not less than 10 inches at the butt. 59. Driving Piles.—Piles shall be of sufficient strength to allow being driven until the penetration under 1,500 lb. hammer falling freely twelve (12) feet is not more than three-fourths (34) of an inch, or its equivalent CONCRETE MATERIALS 7 for the last three blows. No hammer weighing less than 1,500 lb. will be permitted. The pilesin no case, shall be driven less than ten (10) feet. The heads of the piles, while driving, shall be protected by iron rings to prevent brooming. 60. Test Piles.—If requested by the Engineer, the Contractor shall test loadings of one or more piles as he may select to verify the capacity of piles as stipulated on the plans. In case such a test is required, it will be paid for as an extra at the cost value of the labor involved plus ten per cent (10%). 61. Cut Off.—After the piles are driven they shall be sawed off square at a level not more than one foot above the bottom of the footing. 62. Drainage.—Provision shall be made in abutment and retaining walls and in the fills between spandrels of earth-filled arches, for the drainage of water behind the walls, by weep holes or other means as may be shown on the plans or called for by the Engineer. 63. Adherence to Plans.—The Contractor shall, during construction, adhere strictly to the plans and the inspector shall not ‘be allowed to make any change therein without the written authority of the State Highway Commissioner or his Engineer of Bridges. 64. The Contractor shall check all leading dimensions and clearances as a whole and in detail, and become responsible for the exact position and elevation of all parts of the work. 65. Surface Treatment of Concrete Roadway.—The surface of the concrete roadwaysshall be thoroughly cleaned and coal tar, heated to from 250° to 350° Fahr., shall be evenly spread over the surface, using not less than \ gallon per square yard of surface. Immediately after application of tar, and while tar is still hot, the surface shall be evenly covered with 14” of clean, coarse, sharp sand. The application of tar must not ‘be made when the surface of the concrete is damp. 66. Bridge Camber.—Bridges consisting of more than one (1) span shall be built with their bearings at such an elevation that ponts over each bearing on a nominally straight grade from abutment to abutment shall be raised so as to lie on a vertical circular curve having a ratio of chord, from abutment to abutment, to the middle ordinate equal to the ratio of span to camber allowances for the type of structure under considera- ton. For all practical purposes the said curve may be considered as a parabola. See 341, 347, 351. Concrete Materials. 67. Cement.—A standard brand of Portland cement shall be used. No cement shall be used which the State Highway Commissioner deems unfit for the work. The Contractor shall notify the State Highway Commissioner in writing what brand or brands he intends to use and before ordering the cement shall receive the written approval of the State Highway Commissioner as to the selection of the brand, but the cement itself may be rejected if it fails to meet the requirements herein specified. 68. Chemical Limits.—The following limits shall not be exceeded: Loss on ignition, FH... ee ee ee nee eee eee eens 4.00 Insoluble residue, %..... 0... ccc eee eee eee eee eee teen eee .85 Sulphuric Anhydride, (SO3), %........ 0c ccc ce ee eee eee eens 2.00 Magnesia (MgO), %...... ccc ccc ce ee cee te tee eet ee teen e nee e nee etens 5.00 69. Specific Gravity.—The specific gravity of Cement shall be not less than 3.10. Should the test of cement as received fall below this requirement a second test may be made upon an ignited sample. The specific gravity test will not be made unless specifically ordered. : 70. Fineness.—The residue on a standard No. 200 sieve shall not exced 22% by weight. 71. Soundness.—A pat of neat cement shall remain firm and hard, and show no signs of distortion, cracking, checking or disintegration in the steam test for soundness. 72. Time of Setting.—The cement shall not develop initial set in less than 45 minutes when the Vicat needle is used or 60 minutes when the Gillmore needle is used. Final set shall be attained in not more than ten ours. 73. Tensile Strength.—The average tensile strength in pounds per square inch of not less than three standard mortar briquettes composed of one part cement and three parts standard sand, by weight, shall be equal to or higher than the following: Age at test, Tensible strength, days. Storage of briquettes. Ibs. per sq. inch. 7?—1 day in moist air, 6 days in water.............------+0-- beets 200 28—1 day in moist air, 27 daysin water........... ccc. cece eee eee ees 300 The average tensile strength of standard mortar at 28 days shall be higher than the strength at seven days. 74. Packages and marking.—The cement shall be delivered in suitable bags or barrels with the brand and name of the manufacturer plainly marked thereon, unless shipped in bulk. A ‘bag shall contain 94 pounds net. A barrel shall contain 376 pounds net. 8 CONCRETE MATERIALS 75. Storage.—lIn order to allow ample time for inspection and testing, the cement shall be stored in a suit- able weather-tight building having the floors properly blocked or raised from the ground. The cement shal! be stored in such a manner as to provide easy access for proper identification and inspection of each shipment. 76. Inspection and Tests.—All cement shall be inspected. Every facility shall be provided by the Contractor and when cement is to be tested after delivery a period of at least twelve days shall be allowed for the inspection and necessary tests. Cement failing to meet the seven day requirements may be held awaiting the results of the twenty eight day tests before rejection. All sampling and tests shall be made in accordance with the methods proposed by the American Society for Testing Materials as adopted September first, 1916, and with all subsequent amendments thereto. 77. Rejection of Cement.—No cement shall be used until tested, except by special permit in writing from the State Highway Commissioner, and all lumpy, caked, dirty or damaged cement shall be rejected. All re- jected cement shall at once be removed from the site of work. 78. Fine Aggregate.—Fine aggregate shall consist of hard silicious material, clean, free from dust, soft particles, vegetable loam or other deleterious matter. The run of the pit shall be fairly uniform and in alt cases shall meet the following requirements: Passing one quarter (34) inch screen..............-. 0 see ee eee eee eee 100% Passing twenty (20)mesh sieve, between the limits........................ 40% and 80% Passing fifty (50) mesh sieve, not more than. . Dee e ee eee eee eee ee ee eens 20% Passing one hundred (100) mesh sieve, not more than............ .....-.... 4% Clay or Silt adhering to the grains, not over................ 0.0 cece eee, 2% 79. Fine aggregate shall be of such quality that mortar composed of one part Portland cement and three parts fine aggregate by weight, when made into briquettes, shall show a tensile strength at least equal to the strength of 1:3 mortar of the same consistency made with the same cement and standard Ottawa sand. 80. Coarse Aggregate.—Coarse aggregate shall consist of hard, sound, durable particles of stone, clean, free from dust, soft particles, vegetable loam or other deleterious matter. The stone shall be fairly spherical in shape, being practically free from elongated or flat particles. The run of the pit shall be fairly uniform and shall meet the following requirements: a. For one and one-half (114) inch aggregate Passing one and one-half (134) inch screen........... 0.0... cece cee eee tees 100% Passing one (1) inch screen, between the limits........................... 36% and 83% Passing three-quarter (84) inch screen, between the limits.................. 16% and 64% Passing one-half (14) inch screen, between the limits...................... 4% and 36% Passing three-eighths (3%) inch screen, between the limits.................. 0% and 19% Retained on one-fourth (34) inch screen................ 0.0.00. eee eee eee 95% b. For one (1) inch aggregate , Passing one (1) inch screen........... 0.0... c ccc cence eee eee nae 100% Passing three-quarters (84) inch screen, between the limits................. 45% and 89% Passing one-half (14) inch screen, between the limits. . veceeeceeeesis.. 16% and 64% Passing three-eighths (3) inch screen, between the limits.................. 3% and 31% Retained on one-fourth (34) inch screen................ 0000.0 e eee eee 5% c. For three-quarter (34) inch aggregate Passing three-quarter (84) inch screen..............00.00b ccc e cece ee eee 100% Passing one-half (4) inch screen, between the limits...................... 36% and 84% Passing three-eighths (34) inch screen, between the limits.................. 16% and 64% Retained on one-fourth (44) inch screen.............0 0.00... c eee ee ee 95% d. For one-half (44) inch aggregate Passing one-half (44) inch screen...........00.0.00 0000 cee ee eee eee 100% Passing three-eighths (34) inch screen, between the limits.................. 45% and 89% Retained on one-fourth (34) inch screen............ 0.0.0.0. 0c cece eee 5% 81. Aggregate passing any of the preceding gradation tests may be used and will be considered as ‘‘Accep- table Aggregates” provided however, that the following requirements are met: a. For spindles, rails, pilasters and in reinforced concrete sections not thicker than eight (8) inches, the aggregate shall not exceed three-quarter (34) inch. b. For all other reinforced concrete work the aggregate shall not exceed one (1) inch. c. For plain concrete, the aggregate shall not exceed one and one-half (114) inch except as hereinafter provided for under the heading ‘“‘Plums’’. 143. 82. Inferior Aggregates.— When aggregates are submitted for use which in any way do not come up to these specifications they may be either rejected entirely or used with a sufficient increase of cement to give the requisite strength as hereinafter provided for in 105. It should be understood that an increase of cement will not be allowed for as an extra tothe contract price. CONCRETE MATERIALS 0 83. Bank-run Gravel.—Concrete made of cement and unscreened gravel shall not in any case be used for reinforced concrete. In case of a well graded gravel, however, an unscreened mixture may be permitted for plain concrete in large masses upon receiving written permission of the State Highway Commissioner after examination of a sample sent in by the inspector. 84. Rubble Concrete.— When the concrete is to be deposited in massive work, clean stones may be used, thoroughly imbedded and entirely surrounded by at least three inches of concrete. Stones to be acceptable must be as hard in themselves as the resultant concrete. Rubble concrete shall not be deposited in water. This concrete shall be further governed by the requirements of 143. 85. Water.—The water used in mixing concrete shall be free from acid, oil, strong alkalies, vegetable matter or other materials detrimental to the strength of concrete. 86. Concrete Reinforcement Bars.—All reinforcement bars shall be designed for a stress not greater than 16,000 pounds per square inch, shall be of the structural steel grade and shall conform to “Standard Specifications for Billet Steel Concrete Reinforcement Bars’’ as adopted by the American Society for Testing Materials in 1914 or any subsequent revisions therein with exceptions as may be hereinafter specified. 87. Manufacture.—Steel may be made by either the open-hearth or Bessemer process. Bars shall be rolled from standard new billets and no rerolled material will be accepted. The use of twisted bars will not be permitted except in heavy concrete sections involving little or no bending and relatively free from impact or vibration and in no case shall they be used without written permission from the State Highway Commissioner. 88. Chemical and Physical Properties.—The chemical and physical properties shall conform to the following units: Structural Steel Grade Properties considered Plain Bars Deformed Bars Phosphorus, maximum: Bessemer........0.0.0.0. 0. ccc eee eens .10 .10 Open-hearth....... ee nen een eee tent n ee nees 05 05 Ultimate tensile strength, lbs. per sq. inch................ 55/70 ,000 55/70 ,000 Yield point, minimum Ibs. per sq. inch................... 33 ,000 33 ,000 Elongation, per cent in 8 inches, minimum............... 1,400 ,000 1 ,250 ,000 T. S. T. 8. Cold bend without fracture: Bars under 84 inch in diameter or thickness................ 180° d=t 180° d=t Bars 84 inch in diameter or thickness and over............. 180° d=t 180° d=2t 89. Chemical Determinations.—In order to determine if the material conforms to the chemical limita- tions prescribed in 88 herein, analysis shall be made by the manufacturer from a test ingot taken at the time of the pouring of each melt or blow of steel, and a correct copy of such analysis shall be furnished to the Engineer or his inspector. | 90. Yield Point.—For the purposes of these specifications, the yield point shall be determined by careful observation of the drop of the beam of the testing machine, or by other equally accurate method. 91. Form of Specimens.—Tensile and bending test specimens may be cut from the bars as rolled, but tensile and bending test specimens of deformed bars may be planed or turned for a length of at least 9 inches if deemed necessary by the manufacturer in order to obtain uniform cross-section. 92. Number of Tests.—At least one tensile and one bending test shall be made from each melt of open-hearth steel rolled, and from each blow or lot of ten tons of Bessemer steel rolled. In case bars differing $% inch and more in diameter or thickness are rolled from one melt or blow, a test shall be made from the thickest and thinnest material rolled. Should either of these test specimens develop flaws, or should the tensile test specimen break outside of the middle third of its gauged length, it may be discarded and another test specimen substituted therefor. In case a tensile test specimen does not meet the specifications, an additional | test may be made. 93. The bending test may be made by pressure or by light blows. 94. Modifications in Elongation for Thin and Thick Material.—For bars less than , inch and more than 34 inch nominal diameter or thickness, the following modifications shall be made in the require- ments for elongation: 95. For each increase of 1% inch in diameter or thickness above 34 inch, a deduction of 1 shall be made from the specified percentage of elongation. . 96. For each decrease of 75 inch in diameter or thickness below ;', inch, a deduction of 1 shall be made from the specified percentage of elongation. 97. Finish.— Material must be free from injurious seams, flaws or cracks, and have a workmanlike finish. 98. Variation in Weight.—Bars for reinforcement are subject to rejection if the actual weight of any lot ‘varies more than 5% over or under the theoretical weight of that lot. - 10 CONCRETE MATERIALS 99. Unit of Measure.—The unit of measure shall be the cubic foot; a bag of cement containing ninety- four (94) pounds shall be considered as the equivalent of one cubic foot by loose volume. 100. Measure of Fine and Coarse Aggregates.—The measurement of fine and coarse aggregates shall be by loose volume. 101. Proportioning Acceptable Aggregates.—The fine and coarse aggregates shall be used in such relative proportion as will insure the maximum density. The inspector shall, as soon as convenient, mix five (5) specimens of concrete using twenty-three and one-half (23.5) pounds of cement in each sample (4 bag) and the corresponding total aggregate as called for on the plans, but using ratios of fine to coarse aggregate of 30, 40, 50, 60, and 70% respectively, all of the consistency prescribed for reinforced concrete mixtures. These specimens of concrete shall in turn then.be carefully placed and puddled with a three-fourths (34) inch diameter bar in a box, one foot square by two feet deep and the height of the resulting solid content carefully noted. The inspector shall then send to the Testing Laboratory of the State Highway Deparment, one sack of cement, one (1) cement sack of fine aggregate, and one (1) cement sack of coarse aggregate, all of accepted materials, these materials to be used by the laboratory primarily in making two (2) standard eight (8) inch by (16) inch cylinders of each ratio of fine to coarse aggregate above mentioned. Accompanying this shipment will be a statement of the recorded heights of the field specimens with proper identification. The inspector may per- mit the use of that ratio of fine to coarse aggregate which resulted in the smallest solid content subject to acceptance of the cement and the fine and coarse aggregates themselves, until he shall receive from the laboratory the results of a seven (7) day crushing test on one (1) of the two (2) sets of standard cylinders. He shall then, if necessary, modify the ratio to agree with the strongest compression test until he shall receive the results of the twenty eight (28) day crushing test on the other set of standard cylinders at which time further revision based on strength shall be made if necessary. In no case shall less than one (1) volume of fine aggregate be used for one (1) volume cement. . 102. Proportioning for Poor Aggregates.—In case either fine or coarse aggregates or both, fail to meet the requirements of these specifications, they may, on the recommendation of the Engineer, be used providing the units of total aggregate be reduced one and one-half units below that called for on the plans and the ratio of fine to coarse aggregates be determined as described for acceptable aggregates. In no case however shall less than one volume of fine aggregate be used for one volume of cement. 103. Relation of Cement to Aggregate.—The amount of cement to be used shall be expressed as the ratio of the number of bags of cement to the sums of the corresponding number of cubic feet of fine and coarse aggregate required. A1:9ratioof cement to total aggregate shall in general be used for footings. When footings are reinforced with steel, however, a 1:74 ratio shall be used. A 1:71 ratio of cement to total aggregate shallin general be used for all plain concrete above footings unless otherwise specified. A 1:6 ratio of cement to total aggregate shall in general be used for all reinforced concrete sections, excepting those requiring a rela- tively large amount of surface detail. A 1:4) ratio of cement to total aggregate shall be used for precast railing posts, and in general for sections of less thickness than eight (8) inches and in all sections where waterproof construction is required. Exception to the above shall be made when specifically called for on the ns. 104. The above proportions shall, however, be subject to the condition that the strengths of the 8” cylinder at twenty-eight days shall not be less than the following; for 1:44 use 2,500, for 1:6 use 2,000, for 1:74 use 1,600, for 1:9 use 1,300 pounds per square inch. The corresponding values for seven day tests shall not be less than 50% of the above. In case the given proportions will not furnish the above compressive strength the relative amount of aggregate shall be decreased until the strength conditions are guaranteed. | 105. Mixing.—The ingredients shall be thoroughly mixed and the mixing continue until the cement is uniformily distributed and the mass is uniform in color and homogeneous. 106. Measuring Ingredients.—Methods of measurement of the proportions of the various ingredients shall be used, which will insure separate and uniform measurements of the cement, fine aggregate, coarse aggregate and water at all times. 107. Mixer.—-A batch mixer shall be used unless written permission is given to the contrary. 108. Machine Mixing.—When conditions will permit, a machine mixer shall be used of a type which insures the uniform proportioning of the material throughout the mass. 109. The mixing shall continue for a minimum time of at least one minute after all the ingredients are assembled in the mixer. . 110. Hand Mixing.— Mixing by hand will only be permitted on small jobs when necessary and the follow- ing directions carefully followed: (a) Water tight platforms shall be provided of sufficient size to accommodate men and materials for the progressive and rapid mixing of at least two batches of concrete at the same time. Batches shall not exceed one-half cubic yard each, and smaller batches are preferable. (b) Spread the sand evenly upon the platform, then the cement upon the sand (which must be dry enough to be granular and mix readily), make a thin mortar and spread again; add the gravel if used (which must be free from sand), and finally the broken stone, both of which, if dry, should be thoroughly wet down. Turn the mass with shovels or hoes until thoroughly incorporated, and all the gravel and stone is covered with mortar; this will probably require the mass to be turned four times. CONCRETE MATERIALS it 111. Consistency. —The materials should be mixed wet enough to produce a concrete of such consistency as will flow into the forms and about the metal reinforcement when used, and which at the same time can be conveyed from the mixer to the forms without separation of the coarse aggregate from the mortar. Under no circumstances, however, shall water be permitted to stand in the forms, such surplus, as soon as apparent being immediately taken up by a dry batch thoroughly rehandled intheforms. Itisimportant that the amount of water used be the very minimum consistent with the above requirements. 112. Retempering.— Mortar or concrete shal] not be remixed with water after it has partly set. 113. Water-Proof Concrete.—The use of water-proofing compounds or other foreign material added for the purpose of making the concrete water-proof will not be permitted. Sole reliance for water-proofing shall be placed upon the use of a 1” thickness of a water side facing mixture, composed of one unit of cement to one unit of fine aggregate, deposited in 8’’ layers and immediately backed by a 1:4.5 mixture of maximum density mixed of driest possible consistency and well puddled. The use of a vibrator for compacting the concrete shall not be permitted but careful puddling with a 1’’ diameter bar shall be relied on for securing a dense mixture. The facing mixture shall at all times be kept at least 3’’ above the concrete backing. All water-proof concrete shall ke reinforced and the reinforcement shall be designed so as to interfere with puddling operations as little as possible. 114.. Placing Concrete.—Concrete, after the completion of the mixing shall be handled rapidly, and in as small masses as is practical from the place of mixing to the place of final deposit, and under no circumstances shall concrete be used that hag partly set. . 115. The use of spouting systems for placing concrete is not to be permitted without special permission in writing from the State Highway Commissioner. When this system is used great care shall be taken to avoid too wet a mix, with consequent weakening of concrete and danger of laitance. The slope of spouting shall be such as to avoid the separation of materials. Under no condition shall this system be used with any but smooth gravel aggregates. 116. Compacting.—Concrete shall be deposited in such a manner as will permit the most thorough com- pactness, such as can be obtained by working with a straight shovel or slicing tool kept moving up and down until all the ingredients have settled in their proper places by gravity and the surplus water forced to the sur-. ace. | 117. Laitance.—Special care shall be exercised to prevent the formation of laitance. To fulfill this con-- dition it is important that the amount of water used shall be as small as is consistent with the requirements of’ 111. In case laitance has formed despite these precautions, it shall be removed in a manner satisfactory to- the Engineer. : : 118. Securing Reinforcement.—Before depositing concrete the reinforcement shall be carefully placedi in accordance with the plans, and adequate means provided to hold it in its proper position until the concrete has been deposited and compacted. 119. Design of Forms and Surface Finish.—Forms shall be substantial and unyielding so that the con- crete shall conform to the design, dimemsions and contours shown on plans, and they shall be tight in order to prevent the leakage of water. 120. All knot holes, cracks and irregularities on the inside of forms for exposed surface of concrete shall be stopped up with clay or other suitable material. 121. All exposed edges of concrete including grooved panels shall be beveled with a 34” triangular molding. 122. Bracing for forms shall be arranged with wedges so that any notion may be corrected by means of the wedges. 123. In order to detect this motion plumb lines shall be hung at suitable points and observed during the time the concrete is being placed. 124. For all important work, the lumber used for face work shall be one and one-half (14) inch matched tongue and groove, dressed to a uniform thickness, sound and free from knots and secured to the studdings or uprights in horizontal lines. : 125. If approved in writing by the State Highway Commissioner, the Contractor may usesome other type of form if supplemented by an acceptable carborundum brick treatment. The greatest of care must however, be exercised to prevent the warping of timbers, forms must be absolutely tight to prevent loss and separation of cement, and the formation of “‘lap siding’”’ effect entirely eliminated. 126. Incase a carborundum brick treatment is permitted, the surfaces to be rubbed shall receive the treat- ment not later than three (3) days in warm weather nor six (6) days in cold weather after the placing of the oldest concrete in the section. All holes and imperfections in the surface shall first be thoroughly wet, scrubbed: with a wire brush, and compactly filled with a mortar composed of one (1) unit of cement to two (2) of sand. The entire surface is then to be thoroughly wet down and kept moist and a grout composed of one (1) unit of cement to two (2) of sand is to be swabbed on the surface in small patches and ground in vigorously with a. carborundum brick or similar abrasive block until all hollows, lines, markings, and surplus material have- been removed from the surface. The surface is then to be washed clean with clean water and thereafter n@ further surface treatment is to be permitted. 127. Cleaning Forms.—Immediately before placing concrete, the forms shall be thoroughly cleaned of all foreign accumulation. The stability of the forms shall be inspected, wedges tightened up and dimensions checked throughout. 12 CONCRETE MATERIALS 128. Wetting Forms.—Care shall be taken to see that the forms are substantial and thoroughly wetted (except in freezing weather), or oiled, and that the space to be occupied by the concrete is free from debris. 129. When oil or other form surface treatment is used, care shall be taken to see that the material used is of such a nature as will not discolor or otherwise injuriously affect the concrete surface. Preference shall be given to the use of Paraffine Oils or a soap treatment. 130. When the placing of concrete is suspended, all necessary grooves for joining future work shall be made before the concrete has had time to set. 131. Resuming Work.— When work is resumed, concrete previously placed shall be roughened, thoroughly cleansed of all foreign material and laitance, thoroughly wetted and then slushed with a mortar consisting of one part Portland Cement and not more than two parts of fine aggregate. 132. Freezing Weather.—Concrete for reinforced structures or for plain concrete to be left above the surface of the ground shall not be constructed in freezing weather except by the written consent of the State Highway Commissioner, and it shall be protected in the manner in which the State Highway Commissioner directs. In this case the water and the fine and coarse aggregate shall be heated; and in severe cold, salt shall be added in the proportion of about two pounds per cubic yard but no salt shall be used for reinforced concrete. Effective means shall be provided to protect the concrete from freezing until it has thoroughly hardened. It is understood, however, that any concrete laid during freezing weather shall be entirely at the risk of the Con- tractor and concrete showing injury by frost shall be removed and replaced at expense of Contractor. 133. Placing Under Water.—No concrete shall be placed under water without the written consent of the Engineer in charge. In placing concrete under water a tremie of an approved design shall be used. 134. The concrete shall be mixed very wet (more so than is ordinarily permissible) so that it will flow readily through the tremie and into place with practically a level surface. 135. The coarse aggregate shall be smaller than usual and never more than 1” in diameter. . 136. The mouth of the tremie shall be buried in the concrete so far that it is at all times entirely sealed, and the surrounding water prevented from forcing itself into the tremie. 137. The tremie shall be suspended so that it can be lowered quickly when necessary, either to choke off or to prevent too rapid flow. 138. Rubble concrete shall not be permissible under water. 139. All concrete placed through the water shall be not leaner than 1:6 or as stipulated by the Engineer and the extra cement added at the expense of the Contractor. 140. Top Finish.—Where a top finish is called for on the plans, it shall be “struck” with a straight edge until all coarse aggregates have been forced below the surface and then troweled down to a smooth surface. This finish work shall be done immediately after the concrete is poured. 141. Protecting Concrete While Curing.—Concrete floors on steel bridges and reinforced bridge tops of all descriptions and all other surfaces exposed to premature drying shall be protected from the direct rays of the sun, by means of canvas, straw, sand or other means and shall be kept continually wet for a period of at least seven days, after placing. 142. Plain Concrete.—For plain concrete abutments, retaining walls, etc., the following instructions shall be followed: , (a) Each layer shall be left somewhat rough to insure bonding with next layer, above; and if it be already set, shall be thoroughly cleaned and scrubbed with coarse brushes and water before the next layer is placed upon it. : (b) Concrete shall be deposited in the forms in layers of such thickness and position as shall be specified by the Engineer in charge. (ce) Temporary planking shall be placed at ends of partial layers so that none shall run out to a thin edge. In general, except in arch work, all plain concrete must be deposited in horizontal layers throughout. (d) The work shall be carried up in sections of convenient length and each section completed without intermission. . (e) Inno case shall work on a section stop within 18 inches of the top. 143. Plums.—Plums shall be permitted in plain concrete structures provided that their size is not greater than one-quarter of the least width of the concrete section. The concrete shall not be poured in around the plum. Plums shall be clean, hard and dense and shall be deposited by hoist into a bed of fresh concrete of such consistency as to envelop the plum to one-half its depth. . 144. Arch Construction.—In arch construction the prevention of high stresses in the spandrel walls due to the distortion of the arch ring under dead load shall be taken care of by providing a one-half inch tar felt keyed joint at about one-third span intervals. The lowering of wedges shall be forbidden inside of a 28 day interval since the placing of the last batch of concrete in the arch ring. In addition to the above joints one-half inch tar felt keyed expansion joints shall be provided in the spandrel walls over the springing points of the arch. The arch ring shall be poured in longitudinal strips each strip being poured in one continuous operation. When necessary to prevent distortion of the arch ring while pouring concrete the forms shall be weighted down at the crown. When convenient to do so splices in the reinforcement shall be at the quarter span points. 145. Gravity Spandrels.—Spandrel walls for earth filled arches shall be of gravity section in order to reduce the combined stresses in the arch ring. DETAILS OF CONCRETE CONSTRUCTION 18 146. Thickness of Gravity Walls.—Gravity walls retaining earth fills with or without highway loading shall have a thickness not less than 0.45 of the superimposed height of wall. If the fill back of the wall is surcharged or if it carries an electric or steam railway loading this thickness shall not be less than 0.5 of said height and in case of railways carrying E50 loadings or heavier the factor shall be increased to 0.55 as a mini- mum. | 147. Cantilevered Wings.—The wings of abutments shall extend not less than 2’ into the natural soil even when partially covered by a fill flowing around the outside. No reliance is to be placed on this outside fill. The cantilevering of wings from arch spandrels is not to be permitted. 148. Reinforced Concrete.—For reinforced concrete it is desirable to cast the structure at one operation. Whenever this is not possible on account of the size of the structure, points shall be selected in such a manner as to have the least possible effect on the strength of the structure. See 153-160 inclusive. Sections which are to be water tight shall either be poured in one continuous operation or shall be joined by a continuous water- proof membrane at all points of discontinuity in pouring operations. In this latter type of construction water- proof membrane shall always be kept available so that a complete ring of water proofing may be placed in case of tie up or discontinuity of pouring operations. Not over forty-five minutes shall elapse between plac- ing of successive layers of concrete at any portion of a structure which is to be waterproof. 149. Finishing.—After the forms are removed, which should generally be as soon as possible after the concrete is sufficiently set, any small cavities or openings in the face shall be neatly filled with mortar. Any ridges due to cracks or points in the lumber may be rubbed down with a chisel or composition brick. The sooner the above operations are performed, the better will be the result. 130. Removal of Forms.—Forms for reinforced concrete shall remain in place longer than for plain or massive concrete, and forms for floors, beams and similar horizontal structures shall remain in place much longer than for vertical walls. . 151. The following minimum time for the removal of forms (not the supporting shores) shall be as follows: For bottom of slab four days for spans 4 ft. or less plus 1 day extra for each additional foot of span. For sides of beams and girders 7 days. For columns and piers 4 days. For bridge arches 28 days. For monolithic piers and abutments 36 hours. The minimum time for the removal of shores shall be as follows: . oon nt For bottoms of beams and girders 21 days for spans of 10 ft. or less plus 114 days for each additional oot of span. mn char The original shores must in no case be taken down, replaced or disturbed until permitted by the Engineer m charge. , 4 i. When frosty weather occurs during the above periods an extension of time shall be made equal to its uration. j. In special cases written permission may be given by the State Highway Commissioner to decrease the above duration of time for removal of forms. : 152. Travel on Concrete Floors.—Travel shall not be allowed on concrete bridge floors until at least ten days have elapsed after pouring the last batch of concrete. Details of Concrete Construction. RS Ao oP 133. Joints.—Concrete construction shall, when possible, be cast in one operation. 154. When joints are necessary, they shall be so located as to have the least possible effect on the strength of the structure. 135. Joints in columns shall be made flush with the lower side of the girders. - 156. Joints in girders shall be made at a point midway between supports, but should a beam intersect a girder at this point the joint shall be offset a distance equal to twice the width of the beam. 157. Joints in the members of a floor system shall in general be made at or near the center of the span. 158. Joints in columns shall be perpendicular to the axis of the column and in girders, beams and floor slabs perpendicular to the plane of their surfaces. 159. Girders shall not be constructed over freshly formed columns without permitting a period of at least two hours to elapse, thus providing for settlement or shrinkage in the columns. 160. All construction joints shall however be formed with a key of sufficient strength to take the entire maximum possible shear that may come upon the section. 161. Contraction Joints.—In massive work such as retaining walls, abutments, etc., built without rein- forcement keyed contraction joints shall be provided at intervals of from 25 to 50 feet, and with reinforcement from 50 to 80 feet (the smaller the height and thickness, the closer the spacing) throughout the length of the structure. 162. Contraction joints shall be lubricated by an application of petroleum residuum oil or a similar material, 80 as to permit a free movement at the joints when the concrete expands or contracts. 163. Splices in Reinforcement. Whenever it is necessary to splice tension reinforcement the length of lap shall be determined on the basis of the safe working bond stress, the working strength of the bar, and the 14 DETAILS OF CONCRETE CONSTRUCTION shearing resistance of the concrete at the point of splice; or a connection shall be made between the bars of sufficient strength to develop the full strength of the bar. All laps shall be wired for their full length with No. 12 wire or equivalent and in addition all lapping bars shall be finished with standard hooks. 164. Splices at points of maximum stress shall be avoided. 165. In columns, bars more than 34” diameter, not subject to tension shall be properly squared and butted in a suitable sleeve, smaller bars may be treated as indicated for tension reinforcement or the stress may be cared for by embedment in large masses of concrete. ; 166. At foundations, bearing plates shall be provided for supporting the bars, or the bars shall be carried into the footing a sufficient distance to transmit thestress of the steel to the concrete by means of the bearing and bond resistance; in no case shall the ends of the bars be permitted merely to rest on the concrete. 167. Lengths of Beams and Columns.—The span lengths for beams and slabs simply supported should be taken as the distance from center to center of supports, but need not be taken to exceed the clear span plus the depth of beam or slab. For continuous beams the span shall be considered as the distance from center to center of supports. Inno case shall any reduction of span be allowed for the effect of brackets. 168. The length of columns shall be taken as the clear, unsupported length. 169. Calculations.—Calculations shall be made with reference to working stresses and safe loads, rather than with reference to ultimate strength and ultimate loads. 170. Initial Stress.—Initial stress in reinforcement due to contraction or expansion shall be neglected. 171. Tee Beams.—In beam and slab construction an effective bond shall be provided at the juncture of the beam and slab. . | 172. When the principal slab reinforcement is parallel to the beam, transverse reinforcement shall be used, extending over the beam and well into the slab. 173. Where adequate bond and shearing resistance between slab and web of beam is provided, this slab may be considered as an integral part of the beam, but its width shall be determined by the following rules: a. Itshall not exceed one-fourth of the span length of the beam. | b. Its overhanging width on either side of the web shall not exceed six times the thickness of theslab. 174, Proportions of Tee Beams.—Beams in which the tee form is used only for the purpose of providing additional area of concrete shall have a width of flange not more than three times the width of the stem, and a thickness of flange not less than one-third of the depth of the beam. . 175. Continuous Tee Beams.—In the design of tee beams acting as continuous beams, due consideration shall be given to the tensile and compressive stresses at the supports. 176. Floor Slabs.—Floor slabs shall, in general, be designed and reinforced as continuous over the supports and shall be designed for a bending moment equal to eight-tenths of the maximum value when considered as simply supported. A sufficient amount of steel at supports shall be placed at both upper and lower fibres to rep the bond stress within allowable limits should the slab action be either continuous or simply supported. If the length of the slab exceeds 1.5 times its width, the entire load shall be carried by the transverse reinforce- ment. 177. Concrete for Bridge Floors.—Concrete for bridge floors shall be mixed in the proportions of one part of cement to four and one-half parts total aggregate. When a concrete wearing surface is called for it shall be of the same proportion as the floor and shall have carefully embedded in it at mid depth the metal fabric specified to insure toughness, prevent temperature and contraction cracks and insure the supporting slab - against wear by traffic. The top surface of the supporting slab shall receive a coat of hot tar before the pouring of the wearing surface is undertaken. 178. Square Slabs.—Square slabs supported on all four sides shall be reinforced in both directions. _ ‘179. Continuous Beams and Slabs.— When the beam or slab is continuous over its supports, reinforce- - ment shall be fully provided at points of negative moment, and the stresses given in 238 shall not be exceeded. 180. In computing the positive and negative moments in beams and slabs continuous over several sup- ports due to uniformly distributed loads, the following rules shall be followed: 13 s. That for floor slabs the Dending moments at center and at supports shall be taken as 5 for both dead and live loads, where w represents the load per lineal foot and 1 the span length. b. That for beams the bending moment at the center and at supports for interior spans, shall be taken ast and for end span + for center and adjoining supports, for both dead and live loads. c. In case of beams and slabs continuous for two spans only, the bending moment at the central support shall be taken as x and near the middle of span as. | d. At the end of continuous beams the amount of negative bending moment will be left to the judgment of the designer, but it must be provided for. e. Continuous beams and slabs designed for concentrated loads shall have their moments calculated as if they were simply supported and the resulting moment shall then be multiplied by the factor eight-twelfths or eight-tenths to give the designing moment; the factor eight-twelfths shall be used where the coefficient of w } for uniform loading is one-twelfth, and the factor eight-tenths shall be used where the coefficient of w }* for uniform loading is one-tenth. DETAILS OF CONCRETE CONSTRUCTION 15 181. Unusual Span Lengths.—For spans of unusual lengths more exact calculations shall be made, and special consideration shall be given to concentrated loads. 182. Compression Reinforcement.— Where beams are reinforced on the compressive side, the steel shall be assumed to carry its proportion of stress in accordance with the provisions of 243. 183. Cantilever Beams.—In the case of cantilever and continuous beams tensile and compressive rein- forcement must extend sufficiently beyond the support and beyond the point of inflection to develop the re- quisite bond strength. . 184. Bond Strength and Spacing of Reinforcement.—Adequate bond strength shall be provided. The formulas herein-after given for bond stresses in beams is for straight longitudinal bars. Care shall be taken to provide sufficient bars at supports in both top and bottom fibres of beams and slabs to provide for the greatest bond stresses under possible extreme conditions of loading and continuity. 185. Restrained Beams.—lIn restrained and cantilever beams full tensile stress exists in the reinforcing bars at the point of support, and the bars must be anchored in the support sufficiently to develop this stress. All such bars shall have hookedends. See192._— - 186. Anchorage of Bars.—Bars ending theoretically at a point where the shearing stresses are high and the bars are in tension, but the tensile stress is small, may be simply extended into the concrete 50 diameters beyond the theoretical point of ending of said bar. Bars ending theoretically at a point where the tension in the bar is large or a maximum shal] be extended into the concrete 50 diameters and in addition shall be finished with a standard hook. See 192. Bars in Compression may transfer theirstress by a 50 diameter embedment and in case of a small member transferring to a large member, the compressive steel shall be flared or splayed so as to distribute the stress rapidly. No sharp bends in compressive steel shall be permitted inside of the 50 diameter limit. When stress is to be transferred by lapping of bars, the bar shall be tightly wired by not less than No. 12 wire wound spirally for a length of lap of not less than 50 diameters. 187. High Bond Resistance.— Where a high bond resistance is required the deformed bar shall be used. 188. Minimum Slab Thickness.—The total thickness of a slab shall be not less than one-thirtieth of the slab span in the direction of the principal reinforcement nor less than 4 inches. 189. Minimum Width of Beams and Girders.—The minimum width of web, in beams or girders, shall not be less than one-twenty-fourth (1/24) of the span. 190. Internal Stresses.—The internal stresses shall be calculated upon the basis of the following assumptions: a. A plane section before bending remains plane after bending. b. The distribution of compressive stresses in members subject to bending is rectilinear. c. ‘The tensile stresses in the concrete are neglected in calculating the moment of resistance of beams. d. The depth of a beam is the distance from the compressive face to the centroid of the tension reinforce- ment. e. The effective depth of a beam at any section is the distance from the centroid of the compressive stresses to the centroid of the tension reinforcement f. The maximum shearing unit stress in beams is the total shear at the section divided by the product of the width of the section and the effective depth at the section considered. This maximum shearing unit stress is to be used in place of the diagonal tension stress in calculations for web stresses. g. The bond unit stress is equal to the vertical shear divided by the product of the total perimeter of the reinforcement in the tension side of the beam and the effective depth at the section considered. 191. Reinforcement for Shrinkage and Temperature Stresses.— When areas of concrete too large to expand or contract freely as a whole are exposed to atmospheric conditions, the concrete shall be reinforced with not less than one-fourth of one per cent of steel. When the concrete is required to be water tight this shall be increased to one-third of one per cent. This reinforcement shall be placed near the exposed surface and be of a high bond resistance. 192. Standard Hooks.—Standard hooks on reinforcing bars shall be formed by bending 180° on a radius of three diameters of the bar and a final tangent length of four diameters of the bar. 193. Anchorage of Deformed Bars.—The length of embedment for deformed bars may be taken as forty diameters instead of fifty. Otherwise deformed bar anchorages are to be subject to the same specifica- tions as for plain bars above. 194. Lateral Spacing.—The lateral spacing of parallel bars shall not be less than three diameters from center to center, nor shall the distance from side of beam to nearest bar be less than two diameters. 195. Spacing Between Layers of Bars.—The clear spacing between two layers of bars shall not be less than 1” and the distance center to center of layers shall be not less than 3d, where d is the diameter of the bar. 196. Number of Layers Permitted.—The use of more than two layers will not be allowed, unless the layers are tied together by adequate metal connections, particularly at or near points where bars are bent up ordown. Inno case will more than three layers be permitted. 197. Spacing of Small Bars,—The spacing of small bars shall not be so close as to prevent the passing of the concrete between the bars. Bars in slabs shall not be placed closer than three inches center to center. 198. Crossing Layers.—Two layers of bars crossing each other may be in contact, and in this case the bars forming the main reinforcement shall be placed outermost. 16 SHEAR IN CONCRETE CONSTRUCTION Shear in Concrete Construction. _ 199. Maximum Vertical Shear.—The maximum vertical shearing stress in any section shall be used as 8 means of comparison of the resistance to diagonal tensile stress developed in the concrete in beams not having web reinforcement. | 200. Reinforced Webs.—For reinforced webs five-sixths of the average vertical shear shall be considered as being taken by the stirrups, diagonal web pieces and bent up bars. 201. Vertical Web Reinforcement.—Web reinforcement, if vertical, shall be looped around the hori- zontal reinforcement. 202. Inclined Web Reinforcement.—lIf the reinforcement is inclined it shall be securely attached to the longitudinal rods to prevent slipping. - 203. Free Ends of Stirrups.—The free ends of stirrups at points where. the beam has no top reinforcement shall be turned closely through 360° to give additional bond. 204. At points where top reinforcement exists the free ends of stirrups shall be wound around the bars approximately 11% times. 05. Shear Allowance on Web.—Properly reinforced webs will be allowed an average shearing stress from vertical shear three times as high as a plain, unreinforced web. 206. Distribution of Points of Bend.— Where the longitudinal bars are bent up, the points of bending of the several bars shall when possible without detriment to the bond or flexural strength of the beams, be distri- buted along the length of beam in such a way as to give as effective a web reinforcement as possible over the portion of the length of the beam in which it is most needed. 207. In connection with the bent up rods, and in addition to them, vertical stirrups shall be used to act in combination with the bent up rods. . 208. Spacing of Stirrups.—The longitudinal spacing of stirrups or diagonal members, or the distribution of the points of bending of adjacent bent up bars when considered as web reinforcement, shall not exceed three-fourths of the depth of the beam. 209. Stirrups at Points of Negative Moment.—Where negative moment exists as in the case of a continuous beam at the supports, web reinforcement shall be looped over or wrapped around or be connected with the longitudinal reinforcing bars at the top of the beam. In all cases stirrups shall be looped around the tension steel. 210. Straight Shearing, and Punching Shear.— Where pure shearing stress occurs, or shearing stress combined with but a small amount of tensile stress in the concrete, as when a concentrated load rests upon a slab, or other forms of punching shear are produced, or, as in the case of such compression pieces as arch rings or arch ribs, the element of tension will not need consideration, the permissible limit of the shearing stress will be higher than the allowable limit where thisstress is used as a means of comparing the diagonal tensile stress. 9 211.—The allowable unit stress for the above condition is given under the heading ‘Punching Shear’’ in 39g. 212. Maximum footing Projection.—When plain concrete footings are used, they shall not project farther than one-half of the height of the projecting step. " Concrete Columns. 213. Definition of Columns.—By columns are meant compression members of which the ratio of un- supported lengths to least width exceeds six, and which are provided with reinforcement of one of the forms hereinafter described. 214. Slenderness Ratio.—The ratio of unsupported length of column to its least core width shall not exceed fifteen. . 215. Effective Area.—The effective area of a column shall be taken as the area within the protective covering. This shall be known as the core area. 216. Pedestal Proportions.—No plain concrete pedestals shall have a Jess area under coping than twice the area of the corresponding masonry plate. 217. Composite Columns.—Composite columns of structural steel and concrete in which the steel forms a column by itself shall not be classified as a reinforced concrete column. 218.— When this type of column is used the concrete shall not be relied upon to tie the steel units together, or to transmit stresses from one unit to another. : 219. Working Stresses.—The following working stresses shall be used for the different types of columns: a. Columns with longitudinal reinforcement only, to the extent of not less than one per cent, and not more than four per cent, the unit of stress for axial compression shall be as given in 235. b. Columns with reinforcement of bands, hoops or spirals as hereinafter specified, 20% higher than given for ‘“‘a,” provided the ratio of the unsupported length of the column to diameter of the hooped core is not more than ten. 7 c. Columns reinforced with not less than 1% and not more than 4% of longitudinal bars, and with bands, hoops or spirals, as hereinafter specified; stresses 45% higher than given for a, provided the ratio of the un- supported length of the column to the diameter of the hooped core is not more than 8. The values of the above working stresses for various classes of concrete are shown in the diagram of 245. CONCRETE COLUMNS 1T 220. Working Stresses for Arch Rings and Ribs.—For earth filled archesthe arch rings are to havea longi- tudinal reinforcement of not less than one percent of the crown section. At the springing points this steel shall be increased if necessary in order to provide not less than one-fourth per cent of reinforcement in each face of the rib. Continuous radial stirrups are to be provided between the skew backs and the one quarter points. For arch ribs carrying the roadway loadings through the spandrels the above specifications for reinforcement shall hold with the exception that the radial stirrups are to be radial bands extending around all longitudianl steel and spaced at intervals not greater than one-half the smallest core dimension of the rib, said bands being used throughout the entire length of arch rib. For such arch rings or ribs the allowable unit stress shall not exceed 25% of the compressive strength of the concrete when temperature and rib shortening stresses are neglected, nor shall they exceed 32.5% when such stresses are included. 221. Longitudinal Reinforcement.—In all cases longitudinal reinforcement shall be assumed to carry jts proportion of stress in accordance with 243, 244 and 222. | 222. The hoops or bands shall not be counted on directly as adding to the strength of the column. 223. Fastening of Reinforcement.—Bars composing longitudinal reinforcement shall be straight and shall have sufficient lateral support to be securely held in place until the concrete has set. 224. Amount of Hooping.— Where hooping is used the total amount of such reinforcement shall be not less than 1% of the volume of the column so enclosed. : 225. Spacing of Hooping.—The clear spacing of such hoops shall not be greater than 1/10 of the diameter of enclosed column with a maximum of not more than 214”. 226. Shape and Splicing of Hooping.—Hooping shall be circular and the ends of bands united in such a way as to develop their full strength. | 227. Securing of Hooping.—Adequate means must be provided to hold bands or hoops in place so as to form a column, the core of which will be straight and well centered. 228. Eccentric Loads.—Bending stresses due to eccentric loads and lateral forces must be provided for by increasing the section until the maximum stress does not exceed the values given in 219-220 and where tension is possible in the longitudinal bars adequate connection between the bars must be provided to take this tension. ; 229. Stirrups and Bands in Arch Rings and Ribs.—No stirrups or bands shall have a smaller diameter than one-fourth inch and the volume of the steel in stirrups shall not be less than one-half per cent of the vol- ume of the corresponding core concrete. Unit Stresses for Concrete Bridges. 230. Allowable working Stresses.—The allowable working stresses are given as a percentage of the ultimate compressive strength of the concrete. 231. The ultimate compressive strength is to be considered as that developed by the laboratory cylinders described in 104 at an age of 28 days. . 232. For the purposes of design, in general five such ultimate units will be used as given in 106 and 107. Special values may, however, be used when the character of the materials to be used warrant, providing com- plete data on this material is in the hands of designer before preparing plans. 233. The values of permissible unit stresses for various strengths of concrete are given in the diagram of 245. 7 234. Bearing.— When compression is applied to a surface of concrete of at least twice the loaded area, a stress of 32.5% of the compressive strength will be allowed. 235. Axial Compression.—For concentric compression on a plain concrete column or pier the length of which does not exceed 12 diameters, 22.5% of the compressive strength will be allowed. 236. For other forms of columns the stresses obtained from the ratios given in 219 will be allowed. 237. Compression on Extreme Fiber.—The extreme fiber stress of a beam calculated on the assumption of a constant modulus of elasticity for concrete under working stresses will be allowed to reach 32.5% of the compressive strength. 238. Adjacent to the support of continuous beams, stresses 15% higher may be used. 239. Shear and Diagonal Tension.—In calculations on beams in which a maximum shearing stress in a@ section is used as a means of measuring the resistance to diagonal tension stress, the following allowable values for the maximum vertical shearing stress will be allowed: . a. For beams with longitudinal rods only, and without web reinforcement 2% of the compressive strength. b. The shearing stress per square inch to be calculated by dividing the total shear at the section by the product of the breath of beam and the lever arm of the resisting couple. | c. For beams thoroughly reinforced with web reinforcement with value of the shearing stress calculated ' asin b, the maximum vertical shearing stress must not exceed 12% of the compressive stress. d. The web reinforcement exclusive of bent up bars in this case shall be proportioned to resist 5/6 of the external vertical shear, this amount to be obtained by multiplying total vertical shears by the distance center to center of stirrups, and dividing this product by the lever arm of the resisting couple. e. Ifthestirrups are inclined at 45 degrees the above amount given for f, shall be multiplied by 0.7. f. For beams in which parts of the longitudinal reinforcement is used in the form of bent up bars distri. 18 UNIT STRESSES FOR CONCRETE BRIDGES buted over a portion of the beam in a way covering the requirements for this type of web reinforcement, the limit of maximum vertical shearing stress, calculated as for b, shall not exceed 3% of the compressive strength. g. Where punching shear occurs, that is, shearing stress uncombined with compression normal to the shearing surface, and with all tension normal to the shearing plane provided for by reinforcement, a shearing stress of 12% of the compressive strength will be allowed. 240. Bond.—A bond stress between concrete and plain reinforcing bars shall not exceed 4% of the com- pressive strength. 41. The bond stress between concrete and drawn wire shall not exceed 2% of the compressive strength. 242. The bond stress between concrete and deformed bars of high carbon steel shall not exceed 5% of the compressive strength. Stress in Reinforcing Steel.—The tensile stress in reinforcing steel shall not exceed 16,000 Ibs. persquare inch. The compressive stress in reinforcing steel shall not be considered greater than the stress in the immediately surrounding concrete times the ratio of the moduli of the elasticity of steel to concrete. The values of this ratio to be used for concretes of various strength is given in 244. 244, Modulus of Elasticity of Concrete.—The value of the modulus of elasticity shall be taken as follows: a. 1/15 of that of steel when the strength of the concrete is taken as 2,200 lbs. per square inch or less. b. 1/12 of that of steel when the strength of the concrete is taken as greater than 2,200 and less than 2,900 Ibs. per square inch. e 1/10 of that of steel when the strength of the concrete is taken as greater than 2,900 lbs. per square inch. d. For deflections of beams which are free to move longitudinally at the supports, in using formulas for deflections which do not take into account the tensile strength developed in the concrete, a modulus of 4 of that steel may be used. 245. ‘Diagram of Permissible Unit Stresses.—For convenience in design the following diagram has been prepared showing the allowable unit stresses in concretes of various strengths when considered for the various purposes heretofore mentioned. The common compressive values used in designare shown by heavy lines and the corresponding numerical values of permissible unit stresses are given. x. et 6: : ; is 7 of eo” oon a 0 iH (0 ae 0 oy a! oF 0 ne f J gor ¢ oe (2 Utirnate Corrpressive Allowable Stresses CLEARANCES AND GENERAL PROPORTIONS FOR BRIDGES Clearances and General Proportions for Bridges. 246. Clearance.—For bridges no part of the structure shall encroach on the space indicated;by the clearance diagram following and labelled ‘“‘Clearance for Bridges’’. _ Wd a 247. For under-crossings no part of the structure shall encroach on the space indicated by-the"clearance: diagram following and labelled ‘‘Clearance for Under-Crossings.”’ 5-6" _ 6-0"... 5-6" 3-6" 6-0" , 7-6" j d & Q . st * ‘ & ® 8 X s . g ays Crown of Rowy4 Gren of Pralvy ad ow SX of qv 6 16-O Chor Foy 6’ 6.||_ (2-9 Clear Ss Gurbh fo Curb a Curb 7#o Cur. 17-9" | /2-0 CLEARANCE FOR GIRIOGES CLEARANCE FOR UNDER CROSSINGS 4 -6” of Seoce whih rriay be consmerse/ os occuom” Sy ore rruck, 18 TON TRUCK LOADING Note:- For /2 Tarn Truék consider space and spacings as shown, aNd concenrrations as Proportiono, x 248. General Proportions.—The width center to center of girders or trusses shallfin™no case’ be Jess. than one-twentieth of the effective span, nor less than is necessary to prevent overturning under the assumed lateral loading. The depth of trusses or girders shall preferably be not less than the following: For rolled beams, use for I-beam spans, one-twentieth the span. For plate girders, one-twelfth the span. . For riveted trusses, one-tenth the span. For rolled beams, used as stringers or floor beams, one-fifteenth the span. For pin-connected trusses, one-eighth the span. oo Of ~0 LOADS FOR STEEL AND CONCRETE BRIDGES f. For truss bridges the inclination of the diagonals with the vertical shall be preferably 45 degrees or less. g. If shallower trusses, girders or beams are used, the section shall be increased so that the maximum deflection will not be greater than if the above limiting ratios had not been exceeded. 249. Standard Depths.—The distance from top of masonry to crown of road shall be three feet for all - spans under eighty feet and five feet for all spans eighty feet or more, allowing six inches from the crown of road to top of stringers for spans under eighty feet, and eight inches for spans over eighty feet except in special eases a8 may be called for on plans. Loads for Steel and Concrete Bridges. 250. Dead Load.—The dead load shall be estimated as clearly as possible and properly proportioned to ‘the panel points. 251. When closed gutters are used an additional allowance of ten pounds per square foot shall be made ‘for dirt or ice covering the entire roadway. " 252. Live Load.—The live loads, whether uniform or concentrated, shall be considered as moving and ~ .ghall be placed in position which will give the maximum stresses for each member considered. 253. The loading for the floor system and its supports shall consist of 18 ton trucks concentrated as showd in sketch and distributed to the various parts of the structure as described in 258. 254. The loading for the chord members of trusses shall consist of a floor load of 100 pounds per square ‘Foot. For spans greater than 130 feet the uniform live load may be reduced one pound for each additional 5 ¥eet of span with a minimum of 80 pounds per square foot for spans of, or more than 230 feet. For the web ‘members of trusses, a floor load of 115 lbs. per square foot shall be used. This may be reduced as described