Deflection Limits

[TimmyH76]

In the IBC table 1604.3 the allowable deflection limits are given for diffrent types of members and the coverings. Footnote f says that for WL and SL the load can be taken as 0.7* Componet and cladding. This seems simple but I've never heard of that before. So does this mean that I can use the MWFRS for strength design and the 0.7*CC for deflection design?

 

[UcfSE]

The 0.7 factor for deflection is based on using the 10-year return period of the wind load instead of the 50-year return period. You can find information on adjusting the wind speed for different return periods in the ASCE.

Whether you use MWFRS or C&C is an unrelated matter relative to the 0.7 factor.

 

[Taro]

Table 1604.3 sets deflection limits for components of buildings. Therefore, the wind load on the member is a component & cladding pressure. This C&C pressure may be reduced to 70% when checking deflection because it is a serviceability criterion. Therefore, a service-level (10 year return period) wind may be used instead of a 50-year wind.

A similar reduction for the MWFRS drift is discussed in the commentary to ASCE-7.