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102
688

AX- .I\\'E€STICATION OF THE.
,S'Z'RESSES EN A PIN CONNECTED
PRATT TRL‘SS

.‘Z‘esis “(:2 *he chrte C! B. S.
TMCHICAN STATE COLLEGE
Kenneth A. Bollinger
1938

 

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PLACE IN RETURN BOX to remove this checkout from your record.
TO AVOID FINES return on or before date due.
MAY BE RECALLED with earlier due date if requested.

6/07 p:ICIRCIDaIeDue.indd-p.1

 

An Investigation of the Stresses

in a Pin Connected Pratt Truss

A Thalia Suhmitted to

The Faculty of
HICHIGAN STATE COLLEGE
of
AGRICULTURE AND APPLIED SCIENCE

by

Konnoth A. Bollinger
Candidate for the Degree of

Bachelor of Science

June 1938

4

THESIS

116394.

A C ERIC) ‘;'-.'LILI‘. GEE} L 1‘3 T

I wish to acknowledge the valuable aid and services
of Erofeaeer C. A. Killer 1n.mak1ng the oomyletion of

this thesis poeeible in its present form.

Investigation

The purpose of this thesis will be to determine the
stress in the various members of the bridge, such as the
stringers. floor beams, chord members, web members,
bracing, and lattice work.

The bridge is located about three miles west of
Lansing, Hichigan and crosses the Grand River at a point
near Dcepdale Cemetery. It was built in 1891 by R. D.
Wheaten & Co. of Chicago. 111..

The bridge is a pin connected Pratt truss composed
of eight sixteen foot panels making a clear span of
one hundred and twenty-eight feet. It also has two beam
approaches, the one on the north end being fourteen and
one half feet long and the one on the south end being
treaty-nine and one quarter feet long. making the total
length one hundred and seventy-one and three quarters
feet. The distance between trusses is fifteen feet.
center to center. The roadway is fourteen feet wide.
The distance between chords is twenty feet, center to
center.

This type of bridge is no longer used and at the
present time the County Road Commission is planning

to erect a more modern and safe structure.

SfECIFICATIUHS

These specifications are taken from the Standard
Specifications for Highway Bridges of the American
Association of Highnzy Officials and the American
Railway Engineering Association, and the Specifications
for Steel Highway Bridges of the American Society of Civil

Engineers.

Impact - Live load stresses, except those due to

sidewalk loads and centrifugal, tractive, and wind forces.
shall be increased by an allowance for dynamic. vibratory.
and impact effects. The amount of this allowance or incre-
ment is expressed as a fraction of the live load stresses
and shall be determined by the formula I ={_§Q__

where Iiis the impact fraction and l is the lenéig of the

loaded span in feet.

Lateral Forces - Spans of 150 feet and less shall be
designed to resist a lateral force of 300 pounds per linear
foot on the loaded chord and 150 pounds per linear foot on
the unloaded chord. For Span: of more than 150 feet, for
each additional 30 feet of span there shall be added 10
pounds per linear foot for the loaded chord and 5 pounds

per linear foot for the unloaded chord.

Allowable Stresses -

Tension. net section 16,000 %/sq. in.
Compression (one diameter) 16,000
Compression, gross section 15.000 - 50 l

r

l - length of the:mamber in inches
r - least radius of gyration in inches
but not to exceed 12.500

Bending in extreme fibers of rolled
shapes, built sections and girders.

net section 16,000
Bending in extreme fibers of pins 24,000
Shear in plate-girder and lobeam

webs. net section 12.000
Shear in pins and shop-driven rivets 2,000

Strength of Lattice-bars - Latticing of compression
members shall be proyorticned to resist shearing stress
normal to the member not.less than that calculated by the

formula: R :

P1

ecOOy

R — normal shearing stress, in pounds

P —-strength of column as a compression member, in pounds
1 -length of column, in inches

y -distance from.neutral axis to extreme fiber, in inches

End Stiffeners -0ver the end bearings of plate girders,

there shall he stiffener angles, the outstanding legs of which
shall extend as nearly as practicable to the outer edge of

the flange angles. End stiffeners shell be proportioned

for bearing on the outstanding legs of the flange angles,

no allowance being.made for the portions of the legs fitted

to the fillets of the flange angles. End stiffeners shall

be arranged, and shall be a sufficient number of rivets in
their connection to the web, to transmit the entire end
reaction to the bearings. They shall not be crimped.

(ail a

 

Intermediate Stiffenera -

Webs shall be stiffened by angles riveted thereto in
pairs on opposite sides, with outstanding legs not exceed-
ing sixteen times their thickness, nor less than twe xnches
plus one-thirtieth of the depth of the girder. Intermediate
stiffenera shall be placed at points of concentrated loading
and at intervals not exceeding the depth of the web, nor

six feet.

HOTE 3

As I we: unable to obtain the glans for this bridge
all measurements were made by myself.

Kat knowing what loading this bridge was designed
for I need the H u 15 lending. The bridge evidently
was not intended for such a heavy leading an it is

badly stressed in some members.

Live loading

This bridge shall be considered a Class A bridge -
One carrying normally heavy traffic unite and the
occasional paeeege of specially heavy loads.

For a class A bridge the H-15 loading should be
used.

Wheel loads for h-ls loading

 

fooa‘fd: /21000#::_T_
#10” J 6’

34¢
3000 Eb /J,aao #:F:_L

 

 

flquivelent leading for egana over 60 feet

”U/r /
(0/5 C 66 fie/eq/ A5,, {00 o [ha/’6,”

/’(J 04/ /9} 5‘00 ’6 «(5/ S/C’df

 

 

Vflz'fo7/77IM-_/04a/ 750 [65///

Floor Lien of the entire bridge

A ‘8 .Z a" 27 27' .57 LET’ EU IE? C a

    

an M]. [£37 kg?” ME? Arc. [£2 use M?

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Floor System

Planks
The planks are 2" x 4' and are placed side by
side with the two inch side down.

The fraction of a wheel load to each stringer
is found by dividing the spacing of the stringers by
4.0 - This formula found in the Specifications for
Steel Highway Bridges.

The width of distribution 2 6.7(23 kW)

D =the distance in feet from the center of the near
support to the center of the wheel.
WWzthe iidth of the wheel or tire in feet.

cl
1‘7.ng

 

§—. x 12.000 1 2335 x 12,000 I 7050 if; E : 07(2D 993;)
4 4

E :- .7(2035 *1o?5)

E: 2.52 ft.
Live load B. Me
795 1.235 x 12: 5610 in. 1b. 12 000 : 795 lb.
2 2 . a x 6
/
Impact E. ii. éoo/ 0‘” 5 fl/M/{s

50 x 5610 12244 in. lb.
1+125

Deed Load B. h.

i;§_fl4%212x12 ~69 in. 1b.
3x6

Total 3. E.

arl~2§ld
o‘c" 6
Z
792:5 ,3): (4‘.-
l “ 6

I :1490 gin/sq. in. Allowable 2800 lb./sq. in.

The planks are C. K.

Stringere Panel VIII

The stringers in panel eight are composed of four
R. I. B. 12": 5" - 35 fl/Tt. Section modulus - 57.8 inJ3'
and two channels 12" x 3“ - 25 g/Tt. Section modulud - 23.9
The spacing of the stringer is variable but the maximum
is three feet.
Interior stringers
Fraction of a wheel load to each stringer is
3/4 = 3/4 : .75
haximum live sherr
12,000 x .75 : 9.000 §
maximum.deed sheer
3.00 x l/S x 4.5 x 8-L35 x 8 : 516 e
Impact sheer

5O 1 9.000 t 3.190 3
ldt+125

Total shear 12,506 5
Stress

12,5206 : 2,440. igl/aq. in.

.2 X. o 23

Allowable 2,0C? fi/sq. in.
Maximum live B. LI.
& x 9,000 x 16 x 12 2 432,000 in. lb.

Eeximum dead 3. E.

1 35‘ C/dé/ie/
l/B x 59.5 x (16) x 12 :|15,2CO in. lb. ‘~15”.A%afi

—————-—0

Impact B. M. 32 6“
45¢,000 x 59 : 123,0rr in. lb.

 

Total Bending Kement
569,900 in. 1b.

Section modulus required

569 200 2 35.6 xx’
“$33066 .

The beam used has a section modulus of 37.8_pu3

so the stringer is 0. K.

Outside stringers punel eight
Deed load on outside stringers

lexinum deed sneer

D

‘.25 x 8 +25 x 3 :1213 E

l‘

Eeximum live sheer - outside foot considered not leaded

s o - . x 12,000 : 8,000 ,j-f
3.0

Impact shear

3,000 x 50 : 2.340 7:!

Totsl shear 11,058 g
stress

11,058 :2.;;:30 iii/sq. in.
12 x .307

Allowable 12,000 n/BQ. in.
maximum live B. k.
i x 3,000 x 16 x 12 : 334,00C lb. in.
Esximum deed B. K. -
1/3 x 27.25 2: (16:12: 12 : 10.500 lb. In.
Inpuct B. L1.

59 x 384,COO :. 136,000 1b. in.
141

Total Bending nomsnt
530,500 lb. in.
Section modulus required

530.500 : 33.2 ,'..3
16.000

The channels used have a section modulus of 23.9 but
it isn't likely they are landed as calculated.

Stringers ~ Beam.sgprosch at the South end

This approach is 29.25 feet long and is composed
of six R. I. B. l?" x 5' - 35 fi/Tt. Section modulus - 57.3/53
and two channels 12“ x 3" - 25 fi/ft. Section modulus - 23.9
Spacing

They are spaced no feet. center to center.
Interior‘stringers

Fraction of 0 wheel load to each at inger

2‘0

.0 : .5
.C

-\
~

I

able)

g.

Elfirfimum live sheer
12,000 x .5 26,000 3%
Maximum dead shear

2 x.l/3 x 4.5 x g9,25 4.35 I 29,25 1: 555.9
2 2

Impact sheer

c x 6.000 : 1950 54'
29.25325

Total sheer 8,505.9 #
Stress

I§.§Q§;g_ :llaoo fl/sq. in.

2 x .438
Allowable 12,000 fi/sq. in.

Maximum live 3. 1:1.

:3 x 6,000 x 20.25 x 12 :. 527,?00 lb. in.
Heximum.dead B. M.

1/3 x 33.00 2: (29.2.5)" 3: 12 : 43,700 lb. in.
Impact 3. H.

50 3.527.000 : 171,000 lb. in.
$54.25

Total Bending homent
746,700 lb. in.
Section hodulus reluired

746.700 : 46.7/5,3

16,000

. , 3
.R. I. 3. sections have a section modulus of 37.8/%

Outside stringers - beem.upgr020h at the south end.
Lead load

1.0 x 1/3 x 4.5 I 1.5 LT/ft.

Maximum dead shear

1.5 1.29.25 +.25 x 29,25 ::388 g
2 2

Maximum live sheer

2,0 - 1.9 x 12,000 : 6,000 5
2.0

Imgoct shear

6,000 1.59 :1950 J
154.25

Total sheer 3,333 #
Stress

8.333 : 1790 fi/sq. in.
IS I .387

Maximum live B. L.
i x 6.000 x 29.25 x 12 2 527,000 lb. in.

Maximum dead 3. 31:.

2.
L/B I 26.5 x (29.25) x 12 2:34.100 lb.in.

Imp {.31 C t B. M.
.50 I 527,000 2:171'C00

154.25
Total Bending Homent 752,100 lb. in.

Section modulus required

739 109 3 45.3 in.3
16.000

The channels used have s modulus of 23.9 . Again the
channels are seeningly over-stressed but it isn't
likely that a.whecl will come as close to the edge as

I have figured.

stringers AB, panel I, panel II, panel III, panel IV,
Panel V, panel VI, panel VII.
These stringers are continuous over two panels,
AB & panel I, etc.
The five interior stringers are R. I. 3.3!.
They rare 6" x 3-3/3" - 12.5 5,17: . Section modulus 7.5 111.5
The outside stringers are channels, 6" x 2' -
10.5 #/ft. Section modulus 5.0 in.3.
fisabné
i ,

,e' xz’

>

 

 

 

 

 

Fraction of a wheel load to each stringer

S n 233§ =‘.537
3‘4
.537 x 12.000 2 7050 #

The maximum shear end bending moment occur when a
wheel load is in the middle of one span.
From Pocket Consenion - page 179

maximum live shes-.1- : .5921 s --.594 x 7050 1 4190 59‘

I

neximum.live B. E. : .205 W1 :.2C$ x 7050 x 192

274,800 in. lb.

‘1

Maximum deed shear
2.55 x 1/5 x 1/6 x 4.5 x 6 x s +1255 x s a 123.2 :54
Impact sheer

50 x 4190 : 1490 #

‘I'EI

Total sheer : 5808.2

Stress

5308.2 3 4210 f/sq. in.
6 x .23 ‘
Allowable 12,000 f/sq. in.

“312.5 {2.35 X 1.5 I 16.03

Deed Bending moment
The reactions for a uniform load ere as shown.

 

3 I / —7j;: /'“_”{2
§' 5’5’ 8
3/3 x. 16.03 x 15 x :3 .. 16.05 x 8 x4 :755 ft. lb.

 

 

256 x 12 I 3080 in. 1b.

Impact B. H.

I41
Totsl Bending homent 378,440 in. ID.

Section modulus required

375,330 : 23.5 in.
16,000

a section modulus of 7.5 in.

' C.‘

The beam used h;.

This is very severely over-stressed.

Stringera - Outside

Dead load on outside stringers
1.1! x l/S x 4.5 t 1.76 %/ft.
Maximum dead shear

1.76.: 8 +-10.5 x 8 :‘93 22¢"~

’aximum live shear

‘Wheel load 2g.1 - 319 x 12,0oc :35,78C g-
2.3 '

From Pocket Companion
maximum live sheer :.594 w 2,594 x 5,730 : 4035.;

Maximum live :3. 1:. =.2os 1'1 2.2m x 6,780 x 192

‘b

: 261,C°C in. 1b.

Ixnpac t shear

~53- }: 4025 z 141-28 2?-

141
Total aheer I 5551 #
Stress

_§§§1_, e 2950 fi/eq. 1n.
6 x .314

Allowable 12,050 fi/eq. 1n.
Maximim defid B. E.

3/8 x 12.26 x 16 x 8 ~ 12.26 x 3 x4 3 2550 in. 1b.

264,000 x so -93,eco in. lb.
; .ifil
Total Bending Moment .359.950 in. 19.

Section mmdulus required

I6.000

.3
The channels used have e section mooulus of 5.0 in. They
are very badly over-stressed.

Floor Beams Nos. 5. 4, 5, 6, 7.
‘3131) EL. Flange 3%" x 2%“ x 3/82
16
inch leg horizontal. End atiffeners 2" x 2” x %'.

Three and one half

 

 

 

 

 

 

 

L, ,ézé“ n
F 1
1_ I / ’
,2 ___
/
[4‘¥23’/1L 6’ -%25“ ‘J
'\ . T v1 2’. "
29x22 ?.707
/§fo 30.60 : ¢77
2x3r? ".___., 6:3?
Dead load from stringers car? 33
Interior stringers ,/¢Ia3 x,Ag : £752:
Outside stringers /92.2¢ X /é : /5?6 /7C
.25"/-"\ ”6 ’5“ 9 G are 2 6 25‘: , (.25’
I 23’ 235’ 235“l.2&;’ —z&¢l 23 |
c??( .994
Cf? 33- %%
Dead Sheer : 836 " “‘““—i-~-~-‘ : //657 67
Dead B. hi. ~‘ X36 x 7251/7gx2—25‘gfl1712357)ytéf:i¥x_C/:$l

3- 7&7??? /W< /%3.

ldve load from.atringero

For Shear
2,3 - 1,0 x (12,000 11%;: 3.000) 7,000 1'"

5,575

N

12,375 - 7.000

n
‘

12,375

I

12,000 +- 375

 

7600 {[75— /2, 5725-

 

 

231], -%7’ J, 225’
- ’r ’l‘

 

 

Mien 2
Maximum Live Shear

12 375 x 7 2 +5 37 §;11.95 17,000 x 14.25:;17,5og #
- 14.5

 

Impact Shear

17,500 x 50 ::5.570 #
32 +125

Total Shear
l7.5004~5,570~#1165.7 :224,255.7 #
Stress
24,235,? 16480 al/sq. in.
12 x Q5
1 Allowed 12.000 fi/nq. in.

Live load from stringers for B. E.

 

12.575 x 65 =:3.4eo .
2.35

12,575 - 5.420 : 8.955
3,720 5795; 58?;5
235’ 23y’l 235’1 235’],

/¢$”

3" 420

 

 

r

 

 

49,325“
liaximm live B. 11.

A?) 376‘

12.375 x 7.25 - 8,955 x 2.55 - 3,420 x 4.7.: 52,550 ft. #
Impact B. M.

52,550 x 50 ;-16,700 ft. lbs.
32 +125

Total B. m.
52,550-116,7oo +4.079 : 75.329 zffl /é3

Tension Flange
y for 33‘3” x 2%” x 5/8" 2 .66 A 22.11

fir" 24-2x.66:22.63

A 273.329 x 12 : 2.42 sq. in.
16,000 x 22.63

 

Area needed 2.42 -' 1/8 :1 web area

2.42 - 23. 1 5(16 :l.48 sq. in.
8 ,

 

 

Area supplied 2 x 2.11 - 2 J: 1 x 3/3 :3.“ sq. in.

Compression Flange
Allowable stress 16,000 - 150 %

16.000 "' 150 1435 x 12 : 12.450 TE/BQC in.
7.51

A: 73 329 x 12 2 3.12 sq. in.
12,430 x 22.68 .
' ‘ 2?/%?.$fh Ifl.
Area needed 3.12 - 24 1: 5(16 2-3-7414?
' 8

Area supplied 2 x 2.11 _-; 4.22 sq. in.

Pitch of Flange rivets

P 2 .121, h - allowable bearing stress
V 11 - dist. between C. 683.
V - liaximum sheer

6060 x 22.63 I? 5.66
24,255.?

P

’1

Five inches was used so the pitch is O. K.

End stitfeners 2" x 2" x 2" were used.
Intermediate stiffener:

No intermediate stiffeners were used. Hewever they
should have been used at points of concentrated loading

and at intervals not to exceed two feet.

Floor Beam 65 2.

 

 

 

 

 

 

6.x
k / , w.
"”' I ——’-3ax22 32/6
2’ _/__/5‘x:?0-C:‘7.5‘7
*5' % c’ >Jl< 4{’ 4”. 3‘8”

 

 

Dead load from stringers same as I,“ 3, 4, 5, 6, '7.

Dead Shear 836 +681 :58 : 1175.7 {,4
""2"" '

Dead 13. 3.1.
836 x 7.5 - 196 x 7 - 256(4.712.55) 681 33 x (213.1)2
*‘f—s a
3 4570 ft. lbfle

\

Live load from stringers for Shear

 

 

7000 {375‘- MWK
1 L23’ J, 17’ . i. 25"
F . T T

 

Laximum live shear

124.312 1 75 x 12.2 #70002 g 14.5 : 17,527 g;
2 15 15

Impact shear
, 17,327 x §Q -= 5.520 7‘?
57

Total Shear
17,327 ,1 5,520 +1,1713.7 : 24,023 g;

Stress

24 023 '7 1 6400 {jg/sq. in.
12 x 5716

Allowable 12.000 gig/sq. in.

Love load from stringers for B. H. 490
542a 2,753" ssfif 3’

,2afli 235’ zar’ zarfil
/3“’

 

 

 

\

 

 

A4375~
Maximum live B. M. #387;

12,375 x 7.5 -— 8.955 x 2.35 - 3,420 x 4.7=55,650 rt. #
MPH-Ct Bo ‘Mc

55,650 x 59 2 17,750 ft. lbs.
157

Tatal B. M. '
Tension Flange

A. = 77 770 x 12 : 2.58 IQ. in.
6,000 X 22.63

Area needed 2.58 - .94 21.64 eg. in.
Are: supplied 2 x 2.11 - 2 x l x 3/8 : 3.47 sq. in.

Compression,Ftange

Allowable etreee 16,000 - 150 l
b

16,000 "' 150 15 I 12 2 12.300 {If/Sq. in.
7.51

A: 77.779 x 12 = 3.55 sq." in.
12.300 x 22.68

Area needed 3.35 - .94 : 2.41 sq. in.

Area supplied 2 x 2.11 : 4.2? sq. in.

Floor Beam #8. ,

 

 

 

 

 

 

 

 

 

L. /J’ \
I‘”
-_ _ _ / I
\ 2 I /_
4f’ I, 6 ’ 4f ’
1‘ ’r
Dead load from stringer.
Interior stringers 16.C3 x 8 = 128
2.8
(35 +1.5 xfi) 8 tr 313.6
Outside stringers 12.26; 8 :- 98
(25 +1.5 1: 1.4) 8 : 216.8
Dead Shear ' .
l,762+~631,33 ==2,102.69 #
, 2 . .
-%‘ /26’ 0" ”.3 fly A7? 7?
“:11 . um 11ml 1.43.4 l H”
Dead B. E. /742 /7:2

1762 x 7.5 - 216.4% x 7 - 98 x 6.75 - 128 x 4.7

' 2
- 313.6 x 4.2 - 128 x 2.55 - 313.6 x 1.4 +§81,33 x (1;)
. 5 8

2: 9,643 ft. lbs.
159me live shear .. same as {f 2.
17,827“ lbs.
Impact Sheer - eame as # 2.
5.520 1.. lbs.
Total Shear
17,327 +5.520 +2102.69 = 24,949.? #

Stress

24 949 '7 =6,550 #/sq. in. .
12 x 5716 Allowable 12.00:” #/sq. in.

Maximum live B. E. - seme as # 2.
55,650 ft. lbs.
Impact 3. R.
17,750 ft. lbs.
Total B. K.
55,650-117,750 49,643 C'85,043 ft. lbs.

Tension Flange

 
 

A z 85 045

12 : 2.75 8d. 1!}.
1 .

.060 x 22.68
2.75 - .94 : 1.81 sq. in. - ares needed
Area supplied::2 x 2.11 ~ 2 x l x 8/8 : 3.47 sq. in.

Compression Flange
Allowable stress - same eszgfif
12,300 f/sq. in.

A 283,043 x 12 ':3.57 sq. in.
12.500 x 22.68

Area needed ; 3.57 - .94.: 2.63 sq. in.

Area supplied2—2 x 2.11 z 4.22 sq. in.

Floor Bean 6‘ l.

 

 

 

 

 

L. Aid“
6 >1
2/
w#.
J7x22-‘/7¢

Dead load from stringers same as # 3, 4, 5, 6, 7. /R;necrgv3

' {Kg/7"“ //f
Dead Shear 836.661938 2 1145.9 # .1. -

2 5/25
Dead. B. M. K 2
/£5
856 x 6. 75 - 196 x 7 - 256(4. 7+2.35)4 619.3 1: eggs
13.5

:3525 ft. lbs.

Live load from stringers for Shear
7600 53.? A§37K‘
4’7

2:3” /
/‘ é7f/ r T
Maximum live shear

12.676 §37§1 x 1 45 +7999”. {13.75 - 7000 2 10. 887 #

 

 

 

 

Impact Shear

10,887 x 50 :3460 .53
I57

Total Shear
10.687 +3460 111146 = 15,493 1%
Stress
5 493 :2070 xii/sq. in.

24 x 5 6
Allowable l2,COC #/sq. in.

Love load from stringers for B. M.

.93 we 1 5: raj: 5’; #41 3 7261

Aff’

 

 

 

 

/),376‘ .
Maximum live B. L1. Lay/f

12,375 x 6.75 - 8,955 x 2.35 - 3.5120 x 4.7 1: 46,400 ft. #
Impact 3. H.

46,4C0 I so : 14,360 ft. lbs.
T57

TOtal B. E.
46,400 +14,800‘#3525 :~64,725 ft. lbs.

Tension Flange

A: 641725 ‘ 12 :- 2014 Bq. in.
16,000 x 22.68

Area needed : 2.14 - .94 21.20 sq. in.
Area supplied: 2 x 2.11 - 2 x l x 3/3:3.47 sq. in.

Compression Flange

Allowable stress 16,000 -- 159 l
b

= 16,000 - lac-13,5 x 12 :-12,636 %/sq. in.
7.61

A 2 64.725 X 12 = 2.70 .q. in.
12,630 I 22.68

Area needed 22.70 - ..94 : 1.76 sq. in.

Area supplied =2 1: 2.11 : 4.22mi. in.

Floor Bean ,1} 9.

 

 

 

 

 

 

 

\ /5’.’6’
2!
Dead load from stringers
Interior stringers 39.2 x 8 :315.6
(55 +1.5 1 2) 29.25 : 557
----2 .
Outside stringers 27.1 x 8 : 216.8,
(25 11.5 x 1) 29,25 : 687
y/"X 235"” 'C 29’ 3/“ 22.4” ‘7/‘6 23"? "23’ 2/6,;
”7‘ [WW/za’57 7' {f7 2’ d” Z’f 72’ “7A 7’ x357

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Dead Shear 2 902

2

335:de B. E Q
2902 x 6.75 - 216.8 x 7 - 337 x 6.9 - 557(5+3*2)

- 313.6(4.2+-1.4) 4.619.8 x (13,5) ::9890 Ft. lbs.
13.5 8

Live Shear- same 38 § 1.
10,887 #
In“act Shear - same as f l
3460 6
Total Shear
10,887-+346O +~2608 :116.953 #
Stress

16 953 z 2260 $764. in.
24 x 57l6

Allowable 12,000 55/81.}. in.

Eaximum live B. k. - ssme as E 1
46,400 ft. lbs.
mysot B. 3-2. - 81163 as 53 1.
14,800 ft. lbs.
Total B. Ll.
46,400+l~;,*360 +9890 : 71,090 ft. lbs.
Tension Flange

A: 711099 x 12 I 2.35 Sq. in.
l6,COL x 22.63

Ares needed 2.55 - .94 : 1.41 sq. in.

Area supglied 2 x 2.11 — 2 x l x.5/B : 5.47 sq. in.

Compression Flange
Allowable stress - svme as f 1.

712,680 {iii/sq. in.

-\

A“: 71 090 x 12 1. 2.96 sq. in.
12,630 x 22.63

Area needed '2.96 - .94 : 2.02 sq. in.

Area supplied 2 x 2.11 z 4.22 sq. in.

Trusses

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Number Dead Stress Live Stress Impact Stress Total
Lou, ‘- 20,200 '-—— 2.3.100 —— 5.550 ~53.850
LOL, r 11,800 + 17,600 + 3.480 + 32,880
u,L, +3.000 + 13,590 H.320 +2o.910
U/UZ — 21,600 — 26,480 -- 5,240 253,320
U/Lz +14.~;oo 52:: + £6777“: +51.670
L/Lz +11,800 + 17,600 7: 3,480 #152,880
UZLZ - 3,250 Lé'jjo: _ £22770 -37.:54o
U113 + 8.650 71/2202: ;§::§: 749,080
02 U5, — 27.000 - 33.200 - 3.560 ~66,760
1321.3 + 21,600 + 26,480 +5.24o + 53,520
uju‘y —2a,aoo -35.4oo -— 7.000 —-71,200
031.4 + 2,300 +11.9oo H.000 747,700
§3U7 -—-~- + 7,850 +.2,160 4.10.010
L31? + 27,000 +sa.2oo + 6,560 #66,760
1’ng - 5.750 I 325:: 1 31375: 752 3::
HM - 1.500 3:3??? 5 3:: 743: :77”. :3:

Loads
The dead load will be determined b, the use of the
formula wc:;gL+- l w,- load brought to each
9 truss per foot
1 - span in feet
w - weight of each truss

per foot in pounds

‘1’: (19.500 +240x8x16)(l + 50 )+-l28 x 7 x l x 4.5
2 128 725 3

{-12.5 x 128 x 3.5+620 x 9 r: 58,253

2
W I 53 253 + _
l23 x 9 128
' r 182 1b..
ft.
The live load used shall be the equivalent H-15
lOEsdlng.

Deed panel weight due to truss equals 182 x 16 = 2910 lbs.
Deed panel loads Upper chord 1450 ”
lower chord 122C+~l450 .: 2670 ”

Assume upper 15CO lbs. and lower 3000 lbs.

 

Dead Stresses
/5‘ao /5~oo “~00 if” /ioa 4T0 /5‘do

¢

 

 

 

 

 

 

 

 

 

T_l i 1; ¢ l LT

 

 

 

/5: 76” 3000 3000 3000 3006 . 3650 3040 3606
T /5‘ 75‘0
‘L‘oUl ~ _“ ’
15,750 x kiquzof :20.26c :i"
20
Lol’ /
15,750 1 ;§ ::11,800#
2
0 /5‘00
U/L/ J/
3000 g < -
\
\
\
\
% _ _ .. 5
U U i
/ Z /§;15\0 3000

15,750 x 2 - 4500 x 1 = s x‘g s-z21,6ro s
4

u/L2
(15.750 - 4500) 25.6 : 14.4C0 d
20
L L

/ 2.

11.800 #

/§00

Dead Stresses

 

 

/5’,‘ 71‘0 T i’ J/

UZLZ 3060 7°00
/§o 0‘, “7%,

l'

 

\
\

 

 

A

‘\
_r ___

 

4’;er 3000 3000

(15, 750 - QCCO) 2L. 6 - 3, 650 :2?
20

quj

Ulug .

15,750 :05 - 4500 x 2 - 4500 x 1 2-3.1‘5 3 :-27.000 #
4

LzL

3
15,750 x 2 - 4500 x l 2.8 x; S : 21,600 #

.9
4
/g‘oa (foo lit,

 

<

\
\
\
;-_\

 

 

 

 

wl
K2752} 3000 3000 360:)

U3U7
15, 750 x 4 - 4500 x 6 = S x‘g s : 23,800 5
4
UJL7
(15.750 - 9000 - 4500) 256 :: 2.800 s
n 20
JEJL

715, 750 x 3 - 4500 x 5 =~S x g s 3 27,000 g
,sio ,gso 4

 

 

 

 

¢ l W"

U /‘8 750 , 3000 3000 3000
3‘53 .,
15.750 - QOFO - 3000 2 3,750 fl

Dead Stresses
/5‘do

 

 

U4 L7
1500 #

IEFLUENCS LINES

 

 

Shear kernel I 533
Sheer Panel 11 ‘73

\Q

8

Sheer Panel III

“4%

 

\L

She er Panel IV ‘7'

_g
/\
\\é.
8

Bending moment at 1 '7

N \

Bending Easement st 2.3.2,

  

 

Bending lioment at 3

 

Bending Moment at 4

Live Stresses

LOU, from shear panel I

(19.500 x 1 11 x 128 x 240) 25.5 2 -28.100

2 3
LL,

(19.500 x '7
2 3

UL,

/

19,300 1 16 x 240

U U from B. it. at 2
[.2

(13500le g;
"'4?" ’5" s

8 2 20
+ 7 l. 1233 x 211.0) _l_§ 2 +17,600
s "'2'" 0
128 x 240) g 2' “26,480
2 5

U/Lz from sheer panel II

+_l_ X (lg ‘f‘ .].'..6.) X 240) g5: :‘1,93C‘
8 2 2x7 20

(9.5011
2

.140: ml

(19,500 x
2

1.930 x 20

50.500 x

93M

(1le from she

25.5
2

6
+ g 1(96 +16 xj‘) 240) 230.6: +450.500
‘t

5.
r

6
panel III

2

: + 17,600

3-“ + 1,510

2
(19,500 x _1_ +3.. (52 +16 x‘j) 240) 25,6 ;-4,550
2 4 .1 2 .

20

(19.500 x g + 5 (80 +16 pg) 240) 25,6 :- +16.600
2 s s 2 20

I ’33 from B. H. at 3

7
(13.590 x _1_5, ,_ _1_5_ x 128 x 240) g : 415,200
2 8 8 2

(3

1.02153 from B. M. {it 2
Same as U/UZ : #265,480
qu7 from B. H. at 4
(w x a +- 13 x 128 x 24.0) g : 455,400
2 2 5

{3311.7 from Shear panel IV

(19.300 x 32: +15 1: 54+ 72:): 16 x 240) 22556 : +11.900

U113 from Shear panel IV
/
.2

(19:5 09 x gfg 1: 48+ 2 x 16 x 240) 25,6 : +7.850
2 8 8 2 20
1.31.7 from 13. 11.3.1; 3
Same as {1ng ' : + 53,200

U31). liethod of joints, upper

11,900 x 20 : 49,3200
25.6
7.850 x 2 : +6.140
25.
U7L7 nethod of Jaints, upper
9.300 x 2 r + 18.600

6.140 x 2 : -12’280

Impact Stresses

LOU]
23,100 x 50
123 +125

1 950 x 5
' $3.3 4 E91. 5

30,500 x as
116 +125
L L

I 2

17,600 x 50

53

4,530 x. 59
36.6 + 25

16.600 x 5
91.5.;125

//

’5’ 550

' I

-+3,430

' I

+ 4,520

: '5,240

’1

«675

: + 3,430

.2
255
1.21.}
53
03114
55,400 I 50 1‘ -7003
253
1131.7
11.9130 1 50 :- 7‘3.0CC
U L
7 3 ngo 2 160
W2; 50 :- + ,
54.9 is $25
1.31.7
33.200 x 50 : +6,500
253
U31“?
9 500 x 50 2 ~2,35O
’ 75.1 +125
6 140 3 5g 2 +1,’71n
' 54.9 +125
UYL?
: 4 'FCC'
153 600 X. 50 + O
. 75.1+I§35
12,280 x. 50 ~ 3 45,420

 

54.9 +125

L U

0 /

A compression mamber com.osed of two channels
P
8" 1.2%" - i“ , seven inches back to back and a cover

plate 12' 1.5" riveted together every five inches.

Load 53,850 J compieasion

Area
Channels 2 X 3.56 = 6072 Sq. ‘ino
cover plate 3‘75 .
10.27 sq. 1”.

Stress 55 850
10.27 § 5.150 {/ch 1n.

___ 667 1f:/)
._ z : /é flfgz II
2 /&. 77m¥dfl ‘ /77

 

 

___—___.—

 

 

 

 

__J ..___..
I about horizontal ins .2
.4 'J:)3 gno
n v X -—-— :3
‘vo I). /.2 /o2 x//6_ +l/6 flé‘) 26.é0

 

 

 

Channels 2/3223 + £26/2M)2) .~ // 5:54

./77&..2

/f= a? 6g
1 about vertical axis
_4 gf‘ 3 1
C. P. ,AZ x /a K [2/ : 573.cmo
chznnels 57% /fl? ._-Z;§_.
~ - 6’74,

,/: 5.2:“ ; i} Q- --.. / 37
/f x7 " /e~77‘ ‘ ‘Z‘/ .
Allowable stress 2 15,000 - 50(25,6 x12) :: 7,800 .é/aq. in.

Z.

This member 1| 0. K. and will stand a load of
7,800 X 10.47 2:81.600 #
L L
A tension member bomposed of two eye-bars 2" x 3"
Load 32,830 § tension
Stress ‘5218§Q_ 1 1.10.960#/bq. 1n.
Eli a 2.5- Allowablo 16.000 fi/nq. in.

This member 13 O. K. and will stand a Iced of

16,0CO x 3 : 48,000 #

U/L,
A tension member composed of two one inch square bers.
Load 23,910 # tension
Stress 20,210 I'lO,455 é/eq. in.
‘ Allowable 16.000 fi/sq. in.
This member is O. K. and will stand a load of
16.000 x 2 :52,000 5%
U,UZ
A compression member the same as LOU,except that
it is of different length.
Load 53,320 # comp.

Stress 53.320 2'5100 fi/oq. in.
10.47

Allowable stress 15,000 - 50(16 x 12) : 11.500 fi/eq. in.
2.13

This member is 0. K. and will stand a load of

11,500.: 10.47 =1129.300 g

U/Lz

A. tension member composed of two, one inch by one and
three quarter inches, bars.

Load 51,670 § tension

Stress 51.570 ..lé,9CO fi/eq. in.
exlxl;

3H

Lilowable 16'0C0 ;;/8q. in.
This_membcr is C. K. and will stand a load of
16,0 0 x 3.5 =256.oco g

L L

/ 2

A tension member composed of two eye-bar8 2a 1 an

i, O

Loud 32,880 § tension

Stress 32.830 1310,960 fi/bq. in.
2x2x:
Allowable 16,0 0 i/sq. in.
This member is O. K. and will stand a load of

16,060 x 3 : 43,000 ;

UJLj-A congression member combosed of four 3" x 2;" x ,

Q.
16
six and one half inches back to back - the three inch

leg outstanding — and Bastened together with lacing bars.

Load 37.54? g compression

Stress 37.349 : 5 760 fl 3 . in.
X 1.62 , / q

 

 

 

 

I about horizontal axis 2) _
5777+,A42/szngg) - 4337
_ ,FE?“’L /7%??7—‘
#4 1'7“//?9§~267
I about vertical axis
7/?7+/;m/?f+g ): /32/ ‘_

~ /337

‘ 61'78 =./‘7§

Allowable stress 15,000 - 50(2o x 12) 26,600 n/sq.
1.45
This member is 0. K. and will stand a stress or

load of 6,600 x 6.43 : 42.800 fi

Uzlj
A tension member composed of two bars, one and
three quarters inches by three qucrters inches.
Load 29,080 J tension
Stress 2 §%i%§% : 11,100 fi/sq. in.
Allowable 16,0(0 fi/sq. in.
This member is 0, K. and will at nd a load of

16,060 x 2.62 : 41,900 }

Uéuj
A compression member the same as U/Uz.
Load 66,760 # congression

Stress 2-66.760 :z6,590 fi/Bq. in.
IC. ‘4 "v,

Allowable stress 11,500 fi/sq. in.
This member is 0. K. and will st nd a load of

11,500 x 10.47 : 120.500 #

L L3

1
A tension member comyosed of two eye-bars. three
inches by three quarters inches.
Load 53.320 } tension
Stress - 95: 320 3: 11.900 Tg/Bq. in.
QxEEE" .
Allowable 16,000 g/sq. 1n.

This member will stand a load of 16.CLC x 4.5: 72.6?

in.

mun

 

I.
r‘. .
\‘ N

Q?U7
A comgreseion memberthe some as U/Uz.
Load 71.200 § compression
Stress 71,2Q3=:6,800 fi/sq. in.
0.3, Allowable 11,580 fi/sq. in.
This member is O. K. and will stand a load of

#
L31!7 '

This member is a counter member designed to take

 

the reversal of stress in E3L73nd acts as a tension
member. It is a seven eighths inch round bar.

load 10,010 5 tension
Stress 10.010 2.15.700 iii/sq. in.

0
000 :5

Allowable 16,0CC f/Sq. in.
This member is slightly overstressed but will not
fail due to the factor of safety.

Q3L7
A tension member comgosed of two, three and one half
inch by one inch eye-bars.
Load 66,760 J tension
Stress 66,760 2 9,550 #/eq. in.
2x5%xl .
.Allowable 15,C""" ,:‘/3\rls in.

This member is 0. K. and will st nd a lOed of

16,000 x 7 = 112.000 if

U L
3 7'
A tension member composed of two one and one half
inch by one half inch bars.

Load 17.700 # tension
StreSi": 17 700 2 11.800 fig/3C1. we

211‘EX‘5
Allowable 16,000 3/80,. in.

This member is O. K. and will stand a stress
of 16.000 x 1.5 : 24.000 #
QBLB»

This member has a reversal of stress but was designed

as a compression member. It is composed the same as Usz

#é
Load 15,400 compression 4,100 # tension

Stress 15.409 :2,380 #/sq. in.
n 6.4;} Allowable 6,600 #/'Qo in.

4 10 2 777 #/8q. in.
3.48-%.2 Allowable 16,000 #/sq. in.

This member is O. K. and will stand a load of
6.600 x 6.48 : 42.800 # compression and 16.000 x 5.28
= 84.500 # tension.

QyLfi;

This member has a reversal of stress. It is composed
the some as U2L2.
Load 21,800 § tension 17.200 # compression

Stress 21,800 a 4,130 fi/sq. in. H
6.48-l.2 Allowable 16,0C-O {if/sq. in.

£7.20Q 2 2,660 #/8Qo- in. ‘
6.48 _ Allowable 6,600 fi/sq. in.

I..I'M‘..‘A?. . .3. VI

 

 

_‘isv .4

4__._.--—

A A -ndt. 1|”.

T04: 1.9353515

These are designed to resist n moving load of

15C 11)?) s/ft.

Diagnnlls

These are tension members and are 3/4“ round bars.
The mpximum.stressed will be those in the first panel
and will be due to shear.
Load per panel 15 x 15C : 2400 #

Shear 2.5 x 2400 :'6000 #

600° 3‘ [“5 L 16)Z : 8300 ,J:
15

Stress act-o :- 19,900 iii/sq. in.
.4413
Allowable 16,005 fi/sq. in.
The diagonals are slightly over-stressed but they

will not fail due to the factor of safety.

Latera Strut

Takes no computed stress. Composed of four angles,
2%“ x 2" - 5/16“, 2;” leg outstanding. Eight inches
back to back. Connected by lacing bars riveted every
foot.

For HUSUngTth length of 15' the radius of

gyration should egu l 1 : 15 x 12 : 1.29.
540 $40

0. . 2
I about horizontal axis - 4(.45 +1.31(3.4e) ) : 63.3

r: 63,5‘:3.5~ 0.4%
5.24

BQTTOJ LATERALS

These ere designed for a moving load of 300 K/Tt. The
diagonals are one inch square bars. The maximum
stressed will be those in the first panel and will be
due to shear.

Load per panel 3116 x 3C0 :24800 #
Shea: 5.5 x 4800 _: 16,300

16.200 x (15 1 16)1 : 24,600 §
15

Stress 24,600 224,600 af"/sq. in.
l
Allowable 16.000 g/sq. in.
These are over-stressed quite a little but they

W111 net fail.

’ ”rt-.1: v A 5-,) r '

 

. ;.__...._.. .-'.

0‘.-

For LOUI, U,U2, 0233, ugu .

Bars used are 2" x. 5/16“.

R: 21 : i1.5eo x 1g.47 x 16 x 12 : 1050 #
4000 x y 4000 x 5.49 -
Stress 1050 1‘ 1680 i?/su_. in.

2 x 5716
Allowable 12,000 31780. in.
For usz, u3L5. 07.7.
Bars used are 12" x 5/16”.

E : p1 : 6.600 x 6.43 x 20 5 lg : 790 #
4000y 4000 x 5.25

Stress 790 :14250 zit/sq. in.
1i15716
Allowable 12,001: 733/33. in.
For upyer cross members.

Bars used are l” x 6/16".

8 :g; :15,000 - 50(15 1 12) : 7,740 xii/sq. in.
A 1.24

R : r1 : 1.740 x 5.24 x 15 x 12 : 520 #
4oooy 4090 x 5.5

2 166-0 ifi/sq. in.
Allowable 12,000 gig/sq. in.

-.".—."_B:'."-IL.'} WflgyA‘u‘z .“- --‘ L“:

 

l' 1273

The pins used are all of the same size, 12' in
diameter. The maximum allowable Bending Loment
is 12,600 in.-1bs.

The pin which is the worst stressed has a load

of 71,200 # placed as shown.5.

 

 

 

 

g)», goo * ‘353‘”
_l
6.5—”
35/600 3;)600

 

 

Bending; Element :3 35,600 x 5.75 . 55.600 I 3025

17,sco in. lbs.

N

This psrticulsr pin is over-stressed but most

of them are not because they are not loaded so heevy.

PORTAL BEACIKG

lcrtnl bracing is used to strengthen the
bridge and also for spgenrcnce. The stresses encoantered
are too small to be calculated. The portal bracing

used is 5" x 2%“ - 5/16" angles.

cororssxoss

l- The stringers are not strong enough for the H - 15
loading.

2- The Truss members are 0. K.

3- Both the top and bottom laterals are over-stressed.
4- The Lecing burs are 0. K.

5- A fee of the pins are over-stressed.

6- This type of structure gives one the false

impression of great strength.

 

 

RGDM USE

 

 

I

116394

 

umnmnmuumummumlugnmuIfififim'ififili ES

5134