i g 3 2 5—44.; W W Ioo nmpoo , ARC-WRONG OPPORTUNIT'IS FOR TH! CIVIL ENGlNEER Mhflnbc'udll ummmmrmnomum Frederick L. Fish!» .1949. THESIS s .I,. O. «.1',‘ If'. ArcéWelding Opportunities for the Civil Engineer A Thesis Submitted to The Faculty of MICHIGAN STATE COLLEGE of AGRICULEURE AND APPLIED SCIENCE by Frederick L. Fichter Candidate for the Degree of Bachelor of Science march 1949 Chapter I INTRODUCTION One of the distinct objectives of any engineer is to obtain the most and the best possible for the least cost to his client. The only way that this objective may be approached is for the engineer to be able to apply his knowledge to the particular task with which he is confronted and to choose a method best suited to this type of problem. _ ‘ \‘ To do this, all information which is available must be within reach and any new process cannot be omitted. These methods must be brought to the atten- tion of the persons involved so that they may be used ‘to obtain the best at the lowest possible cost. It seems to the author that since welding is a-proven art and has in the past shown many deginite advantages over other more standard methods that additional work should be made available in the regular curriculum for those interested. Because of many technical develop- ments during the past few years, arc welding has be- come an accepted engineering procedure and a standard practice in many industries. It is used in the pro- duction of a great many metal products, in construction / 216981 and in maintenance of equipment and structures through- out the industry. As the adoption and use of welding has increased, ways and means of applying the process to obtain maximum benefits have received increased study. During the last‘World‘War many advances have been made---new designs resulting in better machines built--- lighter and stronger structures developed. It is the purpose of this paper to bring out some of the facts concerning the uses of arc welding as might be applied by the Civil Engineer. Special emphasis will be de- voted to structures, especially bridges and buildings. With this information brought to the attention of the reader, another possible solution will become avail- able to the engineer and new ideas may result which will save both time and money and money for the client and be made safer and more pleasant for the workers. Since our present economy is built around the idea of getting the most for our money, it is well worth the effort to be able to discover and apply a possible better solut- ion. Arc welding with its wide applications will an- swer in several situations proving advantageous. Chapter II ADVANTAGES OF STRUCTURAL'WELDING Arc welding possesses many advantages that may be used in structural construction. Several of the situations where it can be used and should be ser- iously condidered as a possible means to a solution are listed below and will be discussed in detail in following chapters. 1. Arc welding decreased weight and cost of most istructural members. ‘Welding saves material in structural connections by making them more compact, and in some cases, by eliminating connection material altogether through the direct welding together of members or structural elements. Saves cost in fabrication, fitting, and assembling by eliminating operations of punching, drilling, countersinking, etc., and by reducing the amount of handling of heavy pieces in the shop and also provides greater flexibility to keep pace with other fabrication and erection operations. Provides greater freedom in architectural and struc- tural assign, and better appearance when steel work is exposed because of smoother surfaces and out- lines. Ediminatee noise often accompanied by other methods especially riveting, which is objection- able and disturbing to occupants of nearby build- ings and is confusing to workmen in the shOp and in the field. Facilitates economical and convenient alterations and additions to existing structures with.a min- imum need for removal of existing walls, partitions, floors, or other members and without field drilling of holes for connections to existing members. It also results in a minimum of noise and other in- convenience to occupants. \ Reduces corrosion and cost of cleaning, painting and maintenance of exposed steel work because of the smooth surfaces provided by welding construc- tion which prevent the accumulation of corrosive dust and other matter in the framing of power plants and industrial buildings, and which dis- courages corrosion in coal bunkers and other coal handling equipment. Corrosion is generally greater in rivets than in base metal, but welds are more corrosion resistant than the base metal. 8. Eliminates leakage at Joints in storage tanks, boats, piping, etc. This is one of the reasons for welding having supplanted riveting to such a large extent in this class of construction. Chapter III SAVING IN WEIGHT Perhaps the most striking single advantage held by welding is the fact that a tremendious saving can be realized over other types of connecting steel. Any reduction in the weight of the material going into construction has a definite effect on the cost---in- variably a saving. Arc welding cannot be overlooked in this respect. Initially the design of a.we1ded str- ucture requires less beam weights because of the cont- inuity possessed of are welded joints which results in smaller moments in the beam. To carry the equivalent load a smaller beam.may therefore be used. ‘Welding is synonymous with continuity---its very process of fusion makes for natural continuity. This continuity is never considered in riveted structures because of the uncerte ainty of the ability of rivets to transfer moments into the adjoining beam. This is the crux of the difference between a riveted and a welded rigid frame. Since the weld may be designed to be just as strong as the beam itself and can take full moments, this continuity is present and a redesign for a lighter beam is advisable for economy primarily. The continuity is economical as it tends to reduce the moments and forces acting on the component parts of the load-bearing structural system. Lighter weight beams may be used resulting in lower costs. A lighter weight system, such as an are welded design, will reduce the cost in one or more of several ‘ways. The initial cost of steel is usually by the pound so any reduction in weight will reduce the cost. The average percentages realized by the saving in this *weight range from 15% to 30% or even more depending on the class of structure. During the last world‘War, while costs were not of prime consideration, economies followed naturally in the wake of speed threugh.welding. Our Navy Dep- artment, generally conservative, reached out boldly, threw aside tradition, changed from riveted to all- welded construction, saved 33% in weight of steel, reduced time of fabrication one-third, and made for added strength and stability. They built some 70,000 ships which were stronger and more durable that the riveted ships could not even compare. welding made a war record that could not have been made without it. At the present time and probably as much or even more in the future, transportation will result in a large portion of the construction costs. Since freight rates are dependent upon weight, here again is a chance for a saving in cost of handling with lighter weight members offered by welded systems. When the steel reaches the fabricators, it must then be removed from the rail and taken to the shOps where it is fabricated. The shops rehandle each piece and form it into units to be transferred to the site. If the number of pieces in each unit can be reduced or made lighter, the cost will be proportionally reduced. Riveted joints require gusset plates and extra pieces to handle. welding eliminates these entirely and as before, members of welded design are lighter in themselves. If weight is a consideration when a structure is designed, the engineer is forced immediately to at least consider welded construction. ‘Welding not only affords the best means of reducing weight, but it does so with- out affecting its strength or rigidity. ‘When the fabricator sends the units out to the site any lese weight which can be achieved in any of the movement means less handling costs. The contractor in handling this steel during its erection requires equipment of such size to sufficiently care for the weights of the members which he is erecting. Naturally the heavier members used require heavier pieces of equipment for erection which means that overhead charges being dependent on the cost of plant equipment and initial cost will be less for the lighter equipment that is sufficient for the lighter welded members. The contractor charges off the overhead in the cost of the project and are therefore kept at a minimum by using the lighter members. Foundations are designed according to the weight which it must support. The lighter the structure, the smaller may the footings or foundations or load-bearing members be designed. This statement goes without exphin- ation and need not be discussed further. The use of arc welding has a definite effect on the choice of section to be used. The shape and method of making the Joints usually is the controlling factor in this choice. This is also true of riveted structures, but a wider variety of shapes are possible with a welded connection. A large portion of the economy due to the saving in weight is because of the elimination of certain plates or parts of the connections. This economy is obtained by reducing the amount of material used as well as the elimination of punching, drilling, or machining which reduces the net area and therefore requires larger sizes to start with. Each connection throughout the structure must be designed to take the entire stress to which each of the members is subjected. Therefore, if rivets are used, allowance must be made for holes for the rivets. In welding there are no holes and, therefore, the net section need not be increased for this allowance. In other words, the connection will take 100% of the load to which it is subjected. Towering structures stand testimony to their time-proved strength. Welding unites the entire structure into a homogenious unit. It eliminates the concentration of stresses at rivet holes and permits the full strength of the metal section at the Joint. It eliminates the lap and seals all joints against corrosion. It is usual pracitce to add a fraction of an inch to the plate thickness to care for the rapid corrosion around rivet heads. This is unnecessary in welded construction. We can make the most of our opportunity to con- serve steel by welding at a time when its supply is critically short. The welded frame will result in a stronger body,will possess less weaving and will be longer-lived. It is clear that welding in comparison with riveting shows a remarkable saving in weight and cost, but in comparing welded high tensile steel with riveted mild steel, the weight economy is still more accentuated. The saving in cost however is somewhat smaller due to the higher price of the high tensile steel. The carrying capacity of structures is greater for an equal dead load and may in many cases result in greater financial advantages. Chapter IV FABRICATION AND ERECTION The process of fabrication includes cutting members and processing apart from the erection site, out to size land shape for a particular place in the assembly. A whole unit may be fabricated such as a tank or container which is completed in a shOp and hauled to the erection site. Truly, any saving in fabrication means a lower cost to the completed unit. 'When the pieces are to be riveted, the holes must be accurately punched or drilled so that they will fit together when they are riveted. welding does away'with the necessity of the accurate template work entirely. Holes do need to be punched for erection purposes, but these holes can be placed with less refine- ment and with a great saving in fabrication costs. When punched or drilled holes are used in a welded structure, the shOp and field connections should be detailed as to require the punching and drilling of as few parts as possible. Such fabrication operations should be avoided for long or heavy members because of the greater cost of handling them in the shop. Holes should be avoided or held to a minimum in main material. Where feasible, riveting and preferably punching and drilling as well, should be avoided on members that must be welded. Steel which is to be welded requires somewhat less handling and shearing. To fit during erection, the pieces must come together in such a way that all of the holes will line up. With.welding, a slight var- iation in lengths can be taken up by the welded connection, whether it be over-size or under-size within fairly large limits. Steel to be fabricated by welding is held in place while the weld is made by means of Jigs or clamps. Jigs should be used whenever possible where any amount of the same type of welded connection is employed. Often, however, they can Just be laid together and welded. Other times a tack weld will be sufficient to hold the pieces together while being welded. The entire process is therefore quite simple. For the sake of economy, Joints and connections should be so detailed as to make as much of the welded connection as practicable as possible to be done in the shops where there is a better Opportunity for the efficient use of Jigs and clamping devices, and where the work can be positioned to the best advantage for welding, even though the work is planned so as to min- imize or eliminate the expense of providing and moving heavy platforms or staging. Scaffolding is required at almost all points and this must be of a more substantial nature for a riveting gang than for a welder. much of the field welding can be done by Operators seated or Courtesy Lincoln Electric Co. Cleveland, Ohio 'Welding on Main Avenue Bridge, Cleveland, Ohio. Joining girder frame to column on one of two 122 ft. over-pass spans. Note the simple scaffolding as used by each of the welders. It can be easily moved by one or two men to a new location. standing on the steel frame, or on very light staging or seats supported by steel hangers or stirrups of such size that they can be moved by one man. This item represents an appreciable cost due to the large number of points which require riveting and the small number of rivets at each point. Field welding should be arranged to require a minimum.of shifting around on the part of the welding operators. The quality of the weld depends greatly upon the skill of the Operators. Consequently, by designing the structure to permit fabrication of large portions in the shop under favorable and controlled conditions, shOp welding is more economical than field welding. Most welders are concentenious workers and take a great interest in his ability to make good Joints and obviously wants to prove that he is as good a workman as any of the others on the project. Too, there is the difficulty of inspection except for certain errors which are visible or can be detected ' by gauges. No suitable, positive, inexpensive method exists for checking the soundness of welds. Inspection and supervision are important, perhaps more than in any other construction, for the reason that flaws are diff- icult to detect in welded construction. Good inspection during building is Of ever increasing importance, having a direct bearing of cost of work, expediency of accomp- lishment and quality Of the final product. ‘Welding involves more sciences than practically any known industrial manufacturing process, and has therefore been made to appear rather complicated. However,when a good welded structure is designed, the sciences are considered and allowances made for the changes which take place and the forces which are brought about during its use. Arc welded construction presents a simple assemble of steel plates and shapes which many times result in configurations that are extremely rigid and contain concentrations of welding and structural discontinuities that act as severe stress raisers. One of the obstacles that the designer faces is the difficulty of getting test data on large, full scale welded structures which may be used in perfecting his designs. Tests of such structures are very expensive and require facilities which usually are not available. There thus Often remains a doubt as to whether data obtained from small- scale laboratory tests can be applied directly to the design of large structures. It has been found by tests conducted at the University of California that the str- ength of steel when fabricated into large structures may be considerably less than when determined by ordinary 0.505 inch tensile tests or from tests of smaller stru- ctures. It is practically impossible for the average field inspector to have knowledge of all of the sciences in- volved. Inasmuch as the designer takes these into consideration it should then appear that the field inspector to follow closely the work as it progresses without deviation from the plans and specifications. Strict adherence to the approved plans, or authorized changes by the designer, will minimize difficulties. Exacting requirements for inspection and testing also affect psychological factors. Since the operator knows that his work has to be inspected, supervised, and possibly, tested (especially the important welds) he will realize that the welds will be sound before they are accepted. Only in the shops can these checks on the welds be made with great satisfaction. There- fore, again we see that the greater number of welds possible which are completed in the shape leaves less for the field Operator working under unsatisfactory conditions. Time and labor saving seems to the author to be the untangible factors for which we strive to cut down on for any type of work in progress. The most expen- sive portion is usually that which requires a greater number of man-hours, therefore, any shortening Of this time is definetly saving costs on the whole project. Many methods have been devised to save labor in the past and many are to be discovered for our use in the future. For instance a gang of riveters consist of four men---a heater, one to toss the heated rivet to a third who inserts it in the rivet hole, and a fourth tO back the rivet up. Arc welding requires a single laborer, therefore arc welding will perform well and will continue to perform to acheive a saving in labor costs. There is no limit to the possibilities of welding in the design field for cutting down on the high cost of labor. Because of the flexibility of arc welding, there are infinite number of ways that may be deveIOped to reduce this expense. Indirectly, time which is reduced on a project reduces labor costs. A recent example is shown by the Naval Forces during‘World‘Wars I and II. During World War I a ship of riveted construction required 243 days on the average to build. During‘World'War II a ship of compartive size, the Liberty Ship, of welded construction could be built in 51 days. One of the reasons for the fast completion was that parts of the ships were fabricated at different points and were transported to the launching docks for final assembly. In this way the work was not concentrated and huge sources of power were not required at one point and labor is at the same time distributed over a wider area. Another example of the speed at which an are welded unit can be completed is when the Unites States Army was faced with transporting heavy loads of military supplies over a sandy western desert. The Army ordered a BOO-ton, 64 wheel trailer for this purpose. Made of welded construction it was completed in 30 days. When time is an important flactor it is plain that arc welding has great potentialities. Welded structures in general can in most cases be completed and put into Operation in a shorter period of time than if it were riveted. If in case the costs were greater at the sacrifice of saving time the finincial betterment many times is ofset by an earlier completion date. A further advantage of fabricated structural is that construction can proceed regardless of adverse weather conditions. Ice and snow, for instance, do little to delay the raising of a steel frame building or bridge. A small canvai shelter can often be used to shield the wind, rain, or snow from a welder whereas quite an elaborate shelter would be necessary for the proper prOtection for a rivet gang of four men plus a large heater which must also be prOtected from spread- Or starting fires. One of the leading advantages of arc welding is that it is economically adaptable to the alteration of existing steel structures for new purposes. many construction projects are additions to existing frame- work or are connected to same. If this existing steel is out of plumb or alignment, it would be almost impossible to prefabricate members to be erected with any great amount of satisfaction for connecting the old with the new. Prefabrication in this case would be met with serious difficulty. Also, some conbtractcrs use old steel which is not to dimension specified on the plans. Here, too, prefabrication is practically impossible. The flexibility which welding possesses would meet these situations with great success in that the members could be out and welded to the exist- ing steel work to any dimension. A more complete discussion on this will be taken up in a later chapter on the maintenance of structures. Another first cost saving has been effected by the use of many welded structures or units instead of steel or iron castings. Machine and die set up charges are entirely eliminated along with the extra handling due to the punching and shearing Operations. Several years ago it was decided that the truss in the arm and head of the Statue of Liberty be strength- ened. The plans having been lost, it would have been a huge task to draw up a new set so that the strengthen- ing plates could be cut to size. Prefabrication was practically impossible due to the crampled quarters inside the structure. With the use of welding, the parts were brought in and put together in place simply in the small space provided. Some of the reinforce- ment was too long to be brought intact so it was cut \ and then welded when put into place. This could not have been accomplished if it were riveted.- Also, it was desirable to have the structure Open to the public during the repair. Had it been riveted, the noise inside of the hollow shell would have been so intense that this would have been made impossible. And to the workers themselves, the noise would have been so teriffic as to be unbearable for them. 'With.welding, the sight-seers enjoyed the sights offered by the structure and the workers were able to work comfort- ably. Chapter V STRUCTURAL AND ARCHITECTURAI.EESIGN If welding is to be economically applied to modern fabrication processes and to be competitive with other available methods, it is necessary that the techniques and procedures developed shall be capable of evaluation as to the actual performance and serviceability capable of being produced. There is increasing need for better engineering data which.will permit the simple calcula- tion of required dimensions and of the loads that can safely be carried by a large number of different types of designs. Many conditions enter into the selection of design, materials, and method of fabrication, henee ‘many tests are generally essential before intelligent decisions may be made by the designing engineers. The causes of defects in welding are usually preventable faults in welding technique and procedure. Economical production of a weld depends on economi- cal design plus economical shop practice Or field prac- tice. Poor shop practice may offset the merits of good design, or poor design may affect the merits of good shOp practice. As an example, the use Of a butt weld is most economical for developing strength and presents direct stress flow between the parts connected and is one of the easiest types of welds to perform. Engin- eering is the process by which a suitable structure for a particular use is Obtained and is the most econ- Omical in both first cost and in maintenance. In the past, an alldwelded design has saved approximately 19% to 40% in the amount of steel used over riveted construction. The closest approach to ideal planning for economy is a reasonable compromise between minimum weight and greatest simplicity. Arc welded design shows considerable advantages vwhen applied to steel structures. Specialized design of the Joints is almost always necessary because a welded Joint is rigid and stress distrubution through it is different from that occurring in joints resulting from other methods of construction. In the engineering field, improvements in design of welded Joints to in- crease Joint efficiency and economy of fabrication have marked an important step in the phase of endavor. Before the war there were a number of welded steel framed buildings and bridges, but the war years saw many develOpments in design, fabrication and erection of welded structures. In the design of rigid frame welded steel structures, it is preferable where possible to employ standard rolled steel sections, but when necessary, sections can be fabricated by welding steel plates together, or rolled steel sections can be strengthened or altered in dimensions by the addition of welded plates or gussets. The designer who is de- signing a product for welded fabrication may be ex- tremely flexible in his choice of materials and shapes. The use of welding for structural steel work has with- out doubt progressed rapidly. The typical welded structure is a rigid frame, a homogenious unit in which columns, beams and girders are rigidly connected. In this sense it is similar to reinforced concrete design. The work involved in rigid frame analysis is to determine the maximum stresses occurring at the joints under all reasonable conditions of loading. The extra work required has discouraged the general use of this type of construction except where the framing system is comparatively simple even though a considerable saving in material can be achieved through the continuity of the joints. There strongly remains the tendency for designers to think in terms Of riveted construction, hence full economies and full structural advantages are not always obtained. A load placed anywhere on any one member of the frame will influence other girders and columns. Columns are thus subjected to bending as well as compression and girders cannot be considered as simple supported. More accurate strength evaluation and better balanced design results. The advantages gained by welding will offset the additional cost of the design work required to solve for the stresses involved in the more complex analysis of the rigid frame. The completely welded structure is not an assembly of independent structural elements Joined together with intermediate connecting pieces, but is a homOgenious unit. Today, through the American‘Welding Society and the American Institute of Steel Construction, ample information is easily available to every architect and engineer. In addition, many fabricators acquired valu- able experience and technical data during the last war. Furthermore, research has yielded welding equipment, such as automatic welders, stud welders and squirt welders, that has decreased the importance of the Opera- tor element in obtaining sound welds and increases the efficiency and reliability of structural welding. Savings are due not only to the characteristics Of the rigid frame and reduction of midspan moments of gir- ders, but also, in both rigid column-beam framing, to the simplicity of welded connections which contributes to the reduction of handling and fabricating costs. The reduCtion in the quantity of steel has indirect implica- tions in additional savings in other materials---the lesser weight of the structure can be reflected in lighter foundations and other load-bearing members. The lightness of the structure results in reduced height of framing members---girders, beams. floor construction. This may mean a considerable saving in outside walls of tall buildings as well as in total space in cubic volume for a given area. The reduction is due mainly to the lower moments to which continuous beams are subjected, as compared to simply supported beams. ‘With construction of continuous beams made more economical by welding, thickness of the over-all floor construction can be reduced by approximately 10% in comparison with simply supported beam construCtion. in nearly every design, cost is the most important factor. In most instances, welded construCtion is the less costly. There are examples, however, where welds ing is a more costly means of fabrication than some of the other methods of production, however welding may prove to be the most satisfactory means of fabrication. If the product in question is of a complicated nature but only a few are to be made, welding is generally the more economical. The same is true of units where minor changes frequently occur. Several examples may be cited where welding is the only possible means of connecting parts together. Other methods such as riveting and bolting would be impobsible or impracticle. Noteithe plate on the following page which shows a 750-foot are welded radio tower. Arc welding makes this type of vertical solid rod antenna possible since bolted or riveted connections cannot be made with rod or tubing. l&12654 - The 104,740 pound weight of the tower rests on this ceramic insulator which is designed to allow.movement in the guyed antenna. ' __W912655 -.A completed 750-foot welded radio tower at Buena Park, Calif. seen through the wreckage of the old bolted, T type tower. Arc welding makes this type of vertical solid rod antenna possible since bolted or riveted connections cannot be made with rod or tubing. For arc welding, the work of Joining must be done following blueprint as there is no mark on the steel indicating the length, location, and the size of welds. On the other hand, the rivet heater has to measure the depth of holes at each point to determine the number and length of rivets to be heated. weldings shows a con- siderable economy in this respect when many points re- quire Joining with a small amount of work required at each point. The welder can get to the point and complete his work quickly. Further savings result all along the line. In the drawing room, drawings are made cheaper, the drawing room burden or overhead is prOportionally lower for welded work. Note the included blueprint on the next page which shows how extreme detail is necessary for a simple welded connection of a girder plate. The time required to compute the stresses and design the detail is several time over the alternate method of a welded design. Detail drawings such as this are entirely eliminated and unnecessary. Also, the time to compute the size of weld to use is much shorter. Drawings can be made more rapidly which gets the details to the shOp more quickly. An example to illustrate this point is brought out by the problem taken from a textbook "Design of‘Modern Steel Structures" by Linton E. Grinter, which states: "Design the lower chord ofla Fink roof truss for a stress of 62,000 lb. using AICS specifications. Design the connection of the member to the end gusset plate. Use two angles placed on opposite sides of a 5/16 inch gusset plate." The computations for the above problem follow and will show without a doubt that the welded design is much the simpler method of design. Besides this factor a definite and measurable saving in weight is outstanding. RIVETED DESIGN Use 3/4 inch rivets. i; Gaunt 2, ._ '_ 5—- _¢ I :t 1:711 l ' I 1' 62w an I , '._J__