Kizahn Blodgett Welding Design This text is much easier to understand and use. Miller is a recognized authority on the weoded of welded connections. AWS D14 standards are used to support the engineering principles presented in the course. For over 60 years, Lincoln Electric has hosted design seminars that have provided the attendees with ideas of how to make welded products more dependable, lower in cost, and welded in a safe manner. Then you can start reading Kindle books on your smartphone, tablet, or computer — no Kindle device required.
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T hese examples are not meant to show that the standard of weld quality should be lowered. However, they are striking evidence of how easy it is to make full-strength welds, welds stronger than the plate.
Welding is the only process that produces a unitized, or one-piece, construction. The we lded plate is so sound, strong, and ductile as to permit some testing procedures that frequent ly are impossible or impractical to perform with other connection metho ds.
Apparently because it is possible to do so, bend tests are often required. Unfortunately, U-bend test resu lts do no t correlate we ll with actual service performance. Because it is possible to examine a we lde d join t by radiographic inspection, some engineers feel thi s must be done. Most radiographic inspection is based on responsible standards. These specifications assure th e qu ality required, yet are realistic.
Frequently, however , local decisions are made to require mo re perfect radiographic soun dness th an th e specifications dem and. Weld 2 shows perfect. In both cases the weld was stronger than the plate. Specimens broke in the plate at approximately 60 , psi. Normally, porosity if it should exist is not a problem, because each void is spherical. It does not represent a notch. Even with a slight loss in section because of the void, its spherical shape allows a smooth flow of stress around the void without any measurable loss in strength.
Tests have shown that a weld can contain a large amount of porosity without materially changing the tensile or impact strength and ductility of the weld. These charts consider size, distribution, and alignment of voids, versus plate thickness. This is defined as "gas pockets and any similar generally globular type voids. For porosity above JiG" in void size, a table shows minimum clearance between voids and maximum size of void for any given plate thickness.
If a welded girder, FIG. The use of only one flange plate with a reasonable number of butt welded splices, at points where the plate thickness can be reduced, is usually adequate and also gives improved fatigue resistance. The selection of a connecting system should be made at the design level; for some types of structures, may even influence the architectural concept itself.
Welding provides the unencumbered simplicity of form essential to the modern look in architecture, typified in this showcase building. In fact, th e full advantages of using steel in compe tition with other materials will only b e rea lized wh en th e structure is ere cted as a welded d esign , and when fabricat ors and ere ctors use modem techniques of weld ing, production scheduling, and mater ials handling.
A weld ed office building in Dallas , Texas, is an example of th e economies possibl e in structural w elding. Th e building is feet high , has 34 floors, and contains , square feet of usable floor sp ace.
The savings are impressive. Th e contractor states that by FIG. Semi-automatic welding, using self-shielding cored electrode, speeded completion of 80 beam-to-column connections per floor. Futhermore, approximately six months in construction tim e will be saved as a result of using a weld ed steel frame. Comparative exp erience has proved that had this type structure involved weld ed connections that were simply converted from another type of conne ction, th ere still would have been savings but substantially less than wh en designing sp ecifically for welding.
This applies to th e shop fabrication of columns and oth er stru ctura ls, and also to the field welding associated with erection. A majority of the more recently built skyscrapers are of welded design. These are found in all sections of th e country, including earthquake-prone San Francisco. Expanded open-web b eams and girders-fabricated from standard rolled b eams-are providing gr eat savings in both bridge and building design.
In multi-story buildings, wh ere utility supply lines can be run through th ese beams and girders rather than suspended below, th e overall building height is substantially shortened. This results in significant savings in material costs-for columns, facia , stairs, etc. The ease with which tapered beams and girders can be fabricated from standard rolled beams p ermits an endless variety of savings in building design. Tapered spandrel beams ar e oft en made deep enough at the column end to reduce th e bending forc e and eliminate need for column stiffen ers.
The spandrel beam is shop welded to th e column for lowest cost and shipped to th e site. Th e new look in building design-esp ecially research centers , office buildings, libraries and museums -calls for a heavy use of exposed steels, including th e corrosion-resistant steels such as ASTM A The clean trim lin es which are demanded with this use of exposed steel can be achi eved only by welding.
Light, airy roof supporting space fram es-threedim ensional truss systems-ar e b eing shop -fabricated in sections, final assembled on th e ground at th e site and lift ed into pl ace. Plastic design does not use the conventional allowable stresses, but rather the calculated ultimate loadcarrying capacity of the structure. In the case of rigid framing, plastic design requires less engineering time than does conventional elastic design and, in most cases, results in significant savings in steel over the use of elastic design.
Welding is the most practical method of making connections for plastic design. This is because the connection must allow the members to reach their full plastic moments with sufficient strength, adequate rotational ability, and proper stiffness.
Because there are no limitations placed on welding, the bridge engineer is not limited or restricted in his thinking. Due to this new freedom of design effected by welding, some rather unusual and unique bridges have appeared in recent years. The State of Connecticut has favored welding design for its highway bridges for over 20 years. The Turnpike has 28 all-welded bridges, the largest of which is the span, foot Mianus River Bridge at Greenwich.
The experience of the States of Connecticut, New York, Texas, California and Kansas has clearly shown that substantial savings are possible in properly designed welded bridges. Bridge girders of variable depth enhance the appearance of the structure, while placing the metal where needed and taking it away where shallower section depth is permissible-thereby saving tons of steel. The Thruway at this point is on both a vertical grade and a horizontal curve, requiring superelevation.
In both building and bridge construction, the development of welded shear connectors and specialized welding equipment for attaching such connectors has accelerated the use of composite floor construction -where the concrete and steel act together with a strength greater than either component, resulting in large savings.
Orthotropic bridge design, long accepted in Europe, is coming into prominence in America as a major approach to reduction of bridge costs.
This concept calls FIG. This lowers erection costs and compresses the project timetable. Orthotropic de sign could not be executed with out weld ing. Even water towers have taken on a b eau ty th at complements adjacent archite cture.
Stadiums for big-league sports clubs and for bigname colleges are leaning heavil y on welding. A very unique feature of th e mod em stadium resulting from weld ed steel design is th e cantilevered roof which remov es column s as obstructions to spectator vision and pl easure. Towers, space needles, huge radi o telescopes, rad ar antennas, off-shore drilling rigs , ore unl oad ers, and many oth er structures are being design ed for welded construction. The trend is to build the structure on a sub-assembly basis, doing as much work as possible under ideal shop conditions where mass-production techniques can be fully employed.
The progress made in recent years in automatic and semi-automatic welding equipment and in positioners and manipulators has made shop fabrication of special girders, knees, and built-up columns extremely attractive. In many cases, the ingenious designer can make tremendous savings through the design of special structural members. This includes members having complex cross-sectional configuration and hybrid members that are a mix of steels having different analyses. Welding developments in the past few years have greatly increased welding speeds, while assuring high quality welds.
Continuous wire processes for semi-mechanized welding for both shop and field applications have substantially increased productivity. Much progress has been made in automatic manipulators, enabling the welding head to be put into proper alignment with the joint of the member in a matter of seconds.
This alignment is automatically maintained along the length of the joint during welding. These manipulators represent a major cost reduction possibility. As the size of the structure increases, the total arc time on a welded job becomes a decreasingly smaller percentage of the total fabricating time.
Thus savings in handling time and increasing manufacturing cycle efficiency are the major potentials for cost reduction. Semi-automatic field welding is speeding up erection and lowering costs. Submerged-arc has long been used in the field for fiat welding.
Recently the use of self-shielding cored electrode wire, automatically fed, has greatly extended the speed and uniform quality inherent with semi-automatic welding. This process is rapidly winning general acceptance. It is not affected by rather severe wind and other adverse climatic conditions. Both submerged-arc and certain cored electrode processes are considered low hydrogen.
Get to Know Us. AmazonGlobal Ship Orders Internationally. Get fast, free shipping with Amazon Prime. Design of Welded Structures Miller is a recognized authority on the design of welded connections. Attendees typically include structural engineers and others associated with welded structures, such as fabricators, erectors and inspectors. Amazon Advertising Find, attract, and engage customers.
Design Of Welded Structures
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