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* Weld size need not exceed the thickness of the thinner part joined, but AISC and AWS D1.5 require that care be taken to provide sufficient preheat to ensure weld soundness.

f When low-hydrogen welding is employed, AWS D1.1 permits the thinner part joined to be used to determine the minimum size of fillet weld.

Smaller fillet welds may be approved by the engineer based on applied stress and use of appropriate preheat.

§ Plate thickness is the thickness of the thicker part joined.

^ Minimum weld size for structures subjected to dynamic loads is 3/16 in.

* Weld size need not exceed the thickness of the thinner part joined, but AISC and AWS D1.5 require that care be taken to provide sufficient preheat to ensure weld soundness.

f When low-hydrogen welding is employed, AWS D1.1 permits the thinner part joined to be used to determine the minimum size of fillet weld.

Smaller fillet welds may be approved by the engineer based on applied stress and use of appropriate preheat.

§ Plate thickness is the thickness of the thicker part joined.

^ Minimum weld size for structures subjected to dynamic loads is 3/16 in.

FIGURE 5.18 Welds on two sides of a plate induce stresses in it.

The capacity of a fillet weld per inch of length, with 21.0-ksi allowable stress, can be computed conveniently by multiplying the weld size in sixteenths of an inch by 0.928, since 0.707 X 21/i6 = 0.928. For example, the capacity of 1 in of 5/i6-in fillet weld is 0.928 X 5 = 4.64, as in the preceding example.

A limitation also is 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. Another reason is that if weld size and plate thickness are nearly equal, the plate corner may melt into the weld, reducing the length of weld leg and the throat. Hence standard specifications require the following: Along edges of material less than V4 in thick, maximum size of fillet weld may equal material thickness. But along edges of material Vi in or more thick, the maximum size should be Vi6 in less than the material thickness.

Weld size may exceed this, however, if drawings definitely show that the weld is to be built out to obtain full throat thickness. AWS D1.1 requires that the minimum effective length of a fillet weld be at least four times the nominal size, or else the weld must be considered not to exceed 25% of the effective length. AWS D1.5 requires that the minimum effective length of a fillet weld be at least four times the nominal size or 1V2 in, whichever is greater.

Suppose, for example, a V2-in weld is only 1V2 in long. Its effective size is 11/2/4 = 3/8 in.

Subject to the preceding requirements, intermittent fillet welds may be 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. But such welds are prohibited in bridges, in general, because of the requirements for sealing edges to prevent penetration of moisture and to avoid fatigue failures.

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).

Weld lengths specified on drawings are effective weld lengths. They do not include distances needed for start and stop of welding.

To avoid the adverse effects of starting or stopping a fillet weld at a corner, welds extending to corners should be returned continuously around the corners in the same plane for a distance of at least twice the weld size. This applies to side and top fillet welds connecting brackets, beam seats, and similar connections, on the plane about which bending moments are computed. 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.

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. The transverse spacing of longitudinal fillet welds in end connections should not exceed 8 in unless the design otherwise prevents excessive transverse bending in the connections.

Renewable Energy 101

Renewable Energy 101

Renewable energy is energy that is generated from sunlight, rain, tides, geothermal heat and wind. These sources are naturally and constantly replenished, which is why they are deemed as renewable. The usage of renewable energy sources is very important when considering the sustainability of the existing energy usage of the world. While there is currently an abundance of non-renewable energy sources, such as nuclear fuels, these energy sources are depleting. In addition to being a non-renewable supply, the non-renewable energy sources release emissions into the air, which has an adverse effect on the environment.

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