Section 2.4.1 of ASCE 7-02 clearly states that increases in allowable stress shall not be used with the load combinations, except where the material strength is time dependant, which it is not for steel.
The 0.75 load combination factor is only to be applied where TWO or more loads act...
Wind loads are at stress level (ASD) not strength level (LRFD), therefore they must be increased when used in strength design. Conversely, seismic loads are at strength level and must be reduced for stress design.
Shera is seldom a problem for compact shapes. However, bearing at the supports should be checked in accordance with ASIC LRFD K1.4, K1.5, and K1.6. These equations are already solved in the AISC beam chapter for all standard shapes.
If I'm not mistaken the ACI commentary states that the equations for rebar spacing are intented to limit average crack widths to 0.016-in. Cracks of this size have not been found to cause corrosion problems. To estimate other crack sizes review the references on the crack control provisions...
FFIELD is correct. It is NOT a 'composite' beam if all members' ybars coincide. It is a 'load sharing' situation. The connection only needs to be designed to transfer sufficient vertical load between the members. Deflection compatibility must be maintained between members by proportioning...
ASCE 7 allows for two or more transient live loads to be reduced by 0.75, with no reduction in live load. For example D+L+S can be considered as D+0.75(L+S). It is important to consider the effects of load duration when using these combinations if you are designing with timber. What you'll...
I conducted research on this matter albeit related to the development of hooked stirrups (see ACI Structural Journal vol. 99, no. 5, doc 99-S57). My research validated the equations for hook bar development length--meaning that hooked bars will develope yield when the hook development length...
Review the DTI manufacturer's installation instructions. If the instructions were not followed exactly, the installation is wrong. It is unwise to put your neck on the line and recommend that a product be used in a manner inconsistent with what the manufacturer recommends.
