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There are 4,, views in videos for Roblox. Read more. While the strength of a fillet weld varies with size, the volume of metal varies with the square of the size. In general, a smaller but longer fillet weld costs less than a larger but shorter weld of the same capacity. Furthermore, small welds can be deposited in a single pass.
Large welds require multiple passes. They take longer, absorb more weld metal, and cost more. As a guide in selecting welds, Table 1. This table is only approximate. The actual number of passes can vary depending on the welding process used.
Figure 1. It can be seen that cost, which is proportional to the number of passes increases much faster than strength. Double-V and double-bevel groove welds contain about half as much weld metal as single-V and single-bevel groove welds, respectively deducting effects of root spacing. Cost of edge preparation and added labor of gouging for the back pass, however, should be considered.
Also, for thin material, for which a single weld pass may be sufficient, it is uneconomical to use smaller electrodes to weld from two sides. Furthermore, poor accessibility or less favorable welding position Sec. When bevel or V grooves can be flame-cut, they cost less than J and U grooves, which require planning or arc-air gouging. For a given size of fillet weld, the cooling rate is faster and the restraint is greater with thick plates than with thin plates. A limitation is also placed on the maximum size of fillet welds along edges.
One reason is that edges of rolled shapes are rounded, and weld thickness consequently is less than the nominal thickness of the part.
Weld size may exceed this, however, if drawings definitely show that the weld is to be built out to obtain full throat thickness. AWS D1. Subject to the preceding requirements, intermittent fillet welds maybe used in buildings to transfer calculated stress across a joint or faying surfaces when the strength required is less than that developed by a continuous fillet weld of the smallest permitted size.
Intermittent fillet welds also may be used to join components of built-up members in buildings. Intermittent welds are advantageous with light members where excessive welding can result in straightening costs greater than the cost of welding.
Intermittent welds often are sufficient and less costly than continuous welds except girder fillet welds made with automatic welding equipment. For groove welds, the weld lengths specified on drawings are effective weld lengths. They do not include distances needed for start and stop of welding. These welds must be started or stopped on run-off pads beyond the effective length.
The effective length of straight fillet welds is the overall length of the full size fillet. No reduction in effective length need be taken in design calculations to allow for the start or stop weld crater. The AISC Specification requires fillet weld terminations to be detailed in a manner that does not result in a notch in the base metal subject to applied tension loads.
An accepted practice to avoid notches in base metal is to stop fillet welds short of the edge of the base metal by a length approximately equal to the size of the weld. In most welds the effect of stopping short can be neglected in strength calculations. A weld that is not stopped short of the edge is not cause for rejection unless the welding results in a harmful notch. The AISC Specification also requires welds to allow deformation to accommodate assumed design conditions.
End returns should be indicated on design and detail drawings. Fillet welds deposited on opposite sides of a common plane of contact between two parts must be interrupted at a corner common to both welds. An exception to this requirement must be made when seal welding parts prior to hot-dipped galvanizing. If longitudinal fillet welds are used alone in end connections of flat-bar tension members, the length of each fillet weld should at least equal the perpendicular distance between the welds.
Plug welds may not be spaced closer center-to-center than 4 times the hole diameter. The length of the slot for a slot weld should not exceed 10 times the thickness of the weld. Slot welds may be spaced no closer than 4 times their width in a direction transverse to the slot length. In the longitudinal direction, center-to-center spacing should be at least twice the slot length. The basic parts of a weld symbol are a horizontal line and an arrow: Extending from either end of the line, the arrow should point to the joint in the same manner as the electrode would be held to do the welding.
Welding symbols should clearly convey the intent of the designer. For this purpose, sections or enlarged details may have to be drawn to show the symbols, or notes may be added. Notes may be given as part of welding symbols or separately. When part of a symbol, the note should be placed inside a tail at the opposite end of the line from the arrow: The type and length of weld are indicated above or below the line.
If noted below the line, the symbol applies to a weld on the arrow side of the point, the side to which the arrow points. If noted above the line, the symbol indicates that the other side, the side opposite the one to which the arrow points not the far side of the assembly , is to be welded.
A fillet weld is represented by a right triangle extending above or below the line to indicate the side on which the weld is to be made. The vertical leg of the triangle is always on the left. For connection angles at the end of a beam, far-side welds generally are assumed: The length of the weld is not shown on the symbol in this case because the connection requires a continuous weld for the full length of each angle on both sides of the angle.
Care must be taken not to omit the length unless a continuous full-length weld is wanted. In general, a tail note is advisable to specify welds on the far side, even when the welds are the same size. For many members, a stitch or intermittent weld is sufficient. Each weld is to be 2 in long. Spacing of welds is to be 10 in center-to-center. If the welds are to be staggered on the arrow and other sides, they can be shown as Usually, intermittent welds are started and finished with a weld at least twice as long as the length of the stitch welds.
This is the notation recommended by AWS, but it can lead to confusion on shop drawings, where dimensions are given in feet and inches as for instance, 2 ft, with no inch symbol.
Therefore, on a weld symbol could be mistaken as 2 ft, 10 in rather than 2 in at 10 in. Then the weld symbol would read 2 10, which is unambiguous. When the welding is to be done in the field rather than in the shop, a triangular flag should be placed at the intersection of arrow and line: This is important in ensuring that the weld will be made as required.
Often, a tail note is advisable for specifying field welds. A continuous weld all around a joint is indicated by a small circle around the intersection of line and arrow: Such a symbol would be used, for example, to specify a weld joining a pipe column to a base plate. The all-around symbol, however, should not be used as a substitute for computation of the actual weld length required.
Note that the type of weld is indicated below the line in the all-around symbol, regardless of shape or extent of joint. The preceding devices for providing information with fillet welds also apply to groove welds. In addition, groove-weld symbols must designate material preparation required. This often is best shown on a cross section of the joint. A square-groove weld made in thin material without root opening is indicated by Length is not shown on the welding symbol for groove welds because these welds almost always extend the full length of the joint.
A short curved line below a square-groove symbol indicates weld contour. A short straight line in that position represents a flush weld surface. If the weld is not to be ground, however, that part of the symbol is usually omitted. When the arrow has this significance, the intention often is emphasized by an extra break in the arrow.
In preparing a weld symbol, insert size, weld-type symbol, length of weld, and spacing, in that order from left to right. The perpendicular leg of the symbol for fillet, bevel, J, and flare-bevel welds should be on the left of the symbol. Bear in mind also that arrow-side and otherside welds are the same size unless otherwise noted.
When billing of detail material discloses the identity of the far side with the near side, the welding shown for the near side also will be duplicated on the far side. Symbols apply between abrupt changes in direction of welding unless governed by the all-around symbol or dimensioning shown. Where groove preparation is not symmetrical and complete, additional information should be given on the symbol.
Also it may be necessary to give weld-penetration information, as in Fig. For the weld shown, penetration from either side must be a minimum of in. The second side should be back-gouged before the weld there is made. Penetration must be at least in. Second side must be back-gouged before the weld on that side is made. Welds also may be a combination of different groove and fillet welds. While symbols can be developed for these, designers will save time by supplying a sketch or enlarged cross section.
It is important to convey the required information accurately and completely to the workers who will do the job. Matching electrodes are given in AWS D1. The basic welding positions are as follows: Flat with the face of the weld nearly horizontal.
The electrode is nearly vertical, and welding is performed from above the joint. Horizontal with the axis of the weld horizontal. For groove welds, the face of the weld is nearly vertical. Vertical with the axis of the weld nearly vertical.
Welds are made upward. Overhead with the face of the weld nearly horizontal. The electrode is nearly vertical, and welding is performed from below the joint.
Where possible, welds should be made in the flat position. Weld metal can be deposited faster and more easily and generally the best and most economical welds are obtained. In a shop, the work usually is positioned to allow flat or horizontal welding. With care in design, the expense of this positioning can be kept to a minimum. In the field, vertical and overhead welding sometimes may be necessary. The best assurance of good welds in these positions is use of proper electrodes by experienced welders.
Other positions are prohibited. When groove-welded joints can be welded in the flat position, submerged-arc and gas metal-arc processes usually are more economical than the manual shielded metal-arc process. Designers and detailers should detail connections to ensure that welders have ample space for positioning and manipulating electrodes and for observing the operation with a protective hood in place.
In addition, adequate space must be provided for deposition of the required size of the fillet weld. For example, to provide an adequate landing c, in, for the fillet weld of size D, in, in Fig. Also, surfaces at and near welds should be free from loose scale, slag, rust, grease, moisture, and other material that may prevent proper welding.
AWS specifications, however, permit mill scale that withstands vigorous wire brushing, a light film of drying oil, or antispatter compound to remain. But the specifications require all mill scale to be removed from surfaces on which flange-to-web welds are to be made by submerged-arc welding or shielded metal-arc welding with low-hydrogen electrodes.
Parts to be fillet-welded should be in close contact. The gap between parts should not exceed in. If it is more than in, the fillet weld size should be increased by the amount of separation. Parts to be joined at butt joints should be carefully aligned. For permissible welding positions, see Sec. Work should be positioned for flat welding whenever practicable.
In general, welding procedures and sequences should avoid needless distortion and should minimize shrinkage stresses. As welding progresses, welds should be deposited so as to balance the applied heat. Welding of a member should progress from points where parts are relatively fixed in position toward points where parts have greater relative freedom of movement. Where it is impossible to avoid high residual stresses in the closing welds of a rigid assembly, these welds should be made in compression elements.
Joints expected to have significant shrinkage should be welded before joints expected to have lesser shrinkage, and restraint should be kept to a minimum. If severe external restraint against shrinkage is present, welding should be carried continuously to completion or to a point that will ensure freedom from cracking before the joint is allowed to cool below the minimum specified preheat and interpass temperatures.
In shop fabrication of cover-plated beams and built-up members, each component requiring splices should be spliced before it is welded to other parts of the member. Up to three subsections may be spliced to form a long girder or girder section. With too rapid cooling, cracks might form in a weld. Possible causes are shrinkage of weld and heat- affected zone, austenite-martensite transformation, and entrapped hydrogen.
Preheating the base metal can eliminate the first two causes. Preheating reduces the temperature gradient between weld and adjacent base metal, thus decreasing the cooling rate and resulting stresses.
Also, if hydrogen is present, preheating allows more time for this gas to escape. Use of low-hydrogen electrodes, with suitable moisture control, is also advantageous in controlling hydrogen content. High cooling rates occur at arc strikes that do not deposit weld metal. Hence strikes outside the area of permanent welds should be avoided. Cracks or blemishes resulting from arc strikes should be ground to a smooth contour and checked for soundness.
To avoid cracks and for other reasons, AWS specifications require that under certain conditions, before a weld is made the base metal must be preheated. Table 1. The table recognizes that as plate thickness, carbon content, or alloy content increases, higher preheats are necessary to lower cooling rates and to avoid microcracks or brittle heat-affected zones.
This temperature should be maintained as a minimum interpass temperature while welding progresses. Preheat and interpass temperatures should be sufficient to prevent crack formation. Temperatures above the minimums in Table 1. Peening sometimes is used on intermediate weld layers for control of shrinkage stresses in thick welds to prevent cracking.
It should be done with a round-nose tool and light blows from a power hammer after the weld has cooled to a temperature warm to the hand. The root or surface layer of the weld or the base metal at the edges of the weld should not be peened. Care should be taken to prevent scaling or flaking of weld and base metal from overpeening.
When required by plans and specifications, welded assemblies should be stress-relieved by heat treating. See AWS D1. Finish machining should be done after stress relieving. Tack and other temporary welds are subject to the same quality requirements as final welds. For tack welds, however, preheat is not mandatory for single-pass welds that are remelted and incorporated into continuous submerged-arc welds. Also, defects such as undercut, unfilled craters, and porosity need not be removed before final submerged-arc welding.
Welds not incorporated into final welds should be removed after they have served their purpose, and the surface should be made flush with the original surface. Before a weld is made over previously deposited weld metal, all slag should be removed, and the weld and adjacent material should be brushed clean.
Groove welds should be terminated at the ends of a joint in a manner that will ensure sound welds. Where possible, this should be done with the aid of weld tabs or runoff plates. The ends of the welds then should be made smooth and flush with the edges of the abutting parts. After welds have been completed, slag should be removed from them.
The metal should not be painted until all welded joints have been completed, inspected, and accepted. Before paint is applied, spatter, rust, loose scale, oil, and dirt should be removed. These techniques include handling of electrodes and fluxes. In addition, welds should not be handicapped by craters, undercutting, overlap, porosity, or cracks.
If craters, excessive concavity, or undersized welds occur in the effective length of a weld, they should be cleaned and filled to the full cross section of the weld. Generally, all undercutting removal of base metal at the toe of a weld should be repaired by depositing weld metal to restore the original surface.
Overlap a rolling over of the weld surface with lack of fusion at an edge , which may cause stress concentrations, and excessive convexity should be reduced by grinding away of excess material Figs. If excessive porosity, excessive slag inclusions, or incomplete fusion occur, the defective portions should be removed and rewelded.
If cracks are present, their extent should be determined by acid etching, magnetic-particle inspection, or other equally positive means. Not only the cracks but also sound metal 2 in beyond their ends should be removed and replaced with the weld metal.
Use of a small electrode for this purpose reduces the chances of further defects due to shrinkage. An electrode not more than in in diameter is desirable for depositing weld metal to compensate for size deficiencies. Excessive requirements are uneconomical. Size, length, and penetration are always important for a stress-carrying weld and should completely meet design requirements.
Undercutting, on the other hand, should not be permitted in main connections, such as those in trusses and bracing, but small amounts might be permitted in less important connections, such as those in platform framing for an industrial building. Type of electrode, similarly, is important for stress-carrying welds but not so critical for many miscellaneous welds.
Again, poor appearance of a weld is objectionable if it indicates a bad weld or if the weld will be exposed where aesthetics is a design consideration, but for many types of structures, such as factories, warehouses, and incinerators, the appearance of a good weld is not critical. A sound weld is important, but a weld entirely free of porosity or small slag inclusions should be required only when the type of loading actually requires this perfection.
Welds may be inspected by one or more methods: visual inspection; nondestructive tests, such as ultrasonic, x-ray, dye penetration, magnetic particle, and cutting of samples from finished welds. Designers should specify which welds are to be examined, extent of the examination, and methods to be used. In such case the welds attaching the connection material to the support must be designed to accommodate this skew.
There are two ways to do this. The AWS D1. The AISC method is simpler, and simply increases the weld size on the obtuse side by the amount of the gap, as is shown in Fig. Both methods can be shown to provide a strength equal to or greater than the required orthogonal weld size of W.
The main difference with regard to strength is that the AWS method, as given by the formulas in Fig. Relationship of weld size to effective throat, te. Note how the skewed fillet welds are to be measured. The contact leg length is not the weld size. It should be noted that the gap, g, is limited to a maximum value of in for both methods.
The effects of the skew on the effective throat of a fillet weld can be very significant as shown in Fig. Welds that are loaded in their longitudinal direction have a design strength of 0.
In such cases, deformation compatibility must also be satisfied. Since the transversely loaded welds are considerably less ductile than the longitudinally loaded welds, the transversely loaded welds will fracture before the longitudinally loaded welds reach their full capacity.
This can easily be seen by examining Fig. A weld loaded transverse to its longitudinal direction will fracture at a deformation equal to approximately 0. At this same deformation the longitudinally loaded weld has only reached about 83 percent of its maximum strength.
For example, to find the strength of the concentrically loaded weld group shown in Fig. In this case it is the transversely loaded weld. By drawing a vertical line from the point of fracture, the strength increase or decrease for the remaining elements can be determined. In this case the strength of the weld group of Fig. There are literally an infinite number of possible connection configurations, and only a very small number of these have been subjected to physical testing.
This chapter provides design approaches to connections based on test data, when available, supplemented by rational design or art and science in the form of equilibrium admissible force states , limit states, and ductility considerations. The science involves equilibrium, limit states, load paths, and the lower bound theorem of limit analysis. The art involves the determination of the most efficient load paths for the connection, and this is necessary because most connections are statically indeterminate.
The lower bound theorem of limit analysis states: If a distribution of forces within a structure or connection, which is a localized structure can be found, which is in equilibrium with the external load and which satisfies the limit states, then the externally applied load is less than or at most equal to the load that would cause connection failure.
In other words, any solution for a connection that satisfies equilibrium and the limit states yields a safe connection. This is the science of connection design. The art involves finding the internal force distribution or load paths that maximizes the external load at which a connection fails. This maximized external load is also the true failure load when the internal force distribution results in satisfaction of compatibility no gaps and tears within the connection in addition to satisfying equilibrium and the limit states.
It should be noted that, strictly speaking, the lower bound theorem applies only to yield limit states in structures that are ductile. Therefore, in applying it to connections, limit states involving stability and fracture lack of ductility must be considered to preclude these modes of failure.
Make a preliminary layout, preferably to scale. The connection should be as compact as possible to conserve material and to minimize interferences with utilities, equipment, and access, and to facilitate shipping and handling. Decide on where bolts and welds will be used and select bolt type and size.
Decide on a load path through the connection. For a statically determinate connection, there is only one possibility, but for indeterminate connections, there are many possibilities.
Use judgment, experience, and published information to arrive at the best load path. Now provide sufficient strength, stiffness, and ductility, using the limit states identified for each part of the load path, to give the connection sufficient design strength, that is, to make the connection adequate to carry the given loads.
Complete the preliminary layout, check specification-required spacings, and finally check to ensure that the connection can be fabricated and erected. The examples of this chapter will demonstrate this procedure. Where there is a possibility of using bolts or welds, let the economics of fabrication and erection play a role in the choice.
Different fabricators and erectors in different parts of the country have their preferred ways of working, and as long as the principles of connection design are followed to achieve a safe connection, local preferences should be accepted.
Some additional considerations that will result in more economical connections Thornton, b are: 1. Do not specify full-depth connections or rely on the AISC uniform load tables.
For moment connections, provide the actual moments and the actual shears. This is needed to do a proper check for column web doubler plates. If stiffeners are required, allow the use of fillet welds in place of complete joint penetration welds.
To avoid the use of stiffeners, consider redesigning with a heavier column to eliminate them. For bracing connections, in addition to providing the brace force, also provide the beam shear and axial transfer force. The transfer force is the axial force that must be transferred to the opposite side of the column. The transfer force is not necessarily the beam axial force that is obtained from a computer analysis of the structure.
See Thornton b and Muir and Thornton for a discussion of this. A misunderstanding of transfer forces can lead to both uneconomic and unsafe connections. These are axial force, shear force, and moment. Many connections are subject to two or more of these simultaneously.
Connections are usually classified according to the major load type to be carried, such as shear connections, which carry primarily shear; moment connections, which carry primarily moment; and axial force connections, such as splices, bracing and truss connections, and hangers, which carry primarily axial force.
Subsequent sections of this chapter will deal with these three basic types of connections. This is done to emphasize the ideas of load paths, limit states, and the lower bound theorem, which except for limit states are less obviously necessary to consider for the simpler connections. The determination of loads, that is, required strengths, is dependent upon the specific building code required for the project, based on location, local laws, and so forth.
At this time , there is much transition taking place in the determination of seismic loads and connection requirements. Chapter 5 deals with connections in high seismic regions and covers these additional requirements.
The lateral force-resisting system in buildings may consist of a vertical truss. This is referred to as a braced frame and the connections of the diagonal braces to the beams and columns are the bracing connections.
Figure 2. For the bracing system to be a true truss, the bracing connections should be concentric, that is, the gravity axes of all members at any joint should intersect at a single point. If the gravity axes are not concentric, the resulting couples must be considered in the design of the members. Consider the bracing connection of Fig. The brace load is kips, the beam shear is 10 kips, and the beam axial force is kips. The design of this connection involves the design of four separate connections.
These are 1 the brace-to-gusset connection, 2 the gusset-to-column connection, 3 the gusset-to-beam connection, and 4 the beam-to-column connection. A fifth connection is the connection on the other side of the column, which will not be considered here. Brace-to-gusset: This part of the connection is designed first because it provides a minimum size for the gusset plate which is then used to design the gusset-to-column and gusset-to-beam connections. Providing an adequate load path involves the following limit states: a.
E, Monson E. Alexander B. Anderson J. Cagle GL. Fox G. Hill L. Holdren W. Kinney, Chair J. Kinsey, Vice Chair M. E, Guse, 2 Vice Chair S. E, Anderson U. W, Aschemeier R. Clarke JA. Cochran IM. Davis PA. Furr H. Gilmer C. Hayes: PT. Hilton N. Lindell G. Manin E. Mattficld JE, Mellinger I. Pearson, Jr E, Pennington R. Stachel K. Dunn J. J, Edwards G. Hill R. Holbert JH. Kiefer CA, Mankenberg. Houston, Chair U. Campbell A. D'Amico B. C, Hobson LW.
Houston I. E, Koski D. Luciani CW. Makar S. Moran P. Wirtz P. B, Champney 3. Guili R. Schraft M. Grieeo, Vice Chair E.
Bickford N. Choy R. Clarke D. Ferrell R. Fletcher P. Huckabee L. Kloiber C. Long P. Marslender J. Olson ILA. Edwards V. Kurwvilla MJ. Mayes R. Medlock TL. Niemann A. Caroti Arcelor Mittal C. Haven Hobart Brothers Company D. Koch Washington State Universtiy V.
Kurwilla Lexicon, Incorporated R. Finnigan Arcelor Mittal C. Hoitomt Consultant J. Phillips Retired LW. Post J. Rees-Evans Steel Dynamics A. It was revised in and under the same title, It was revised again in and given the designation DI. The edition Published an amended version in , and the edition published an amended version in The cade was com- bined with D2. A second printing of D1.
From to , the DI.
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