By Ron Haupt, P.E. on October 29, 2013
When performing a piping analysis, if a seismic analysis is performed, is it also necessary to perform a wind load analysis?
In a high seismic zone, earthquake is likely to control the short-term sustained load design of piping. However, in low seismic zones, wind might be expected to control the short-term design of piping. Wind might seldom actually fail pipe, but wind can certainly cause piping to disengage from its supports, or wind deflections could be deemed excessive, or wind could potentially cause unacceptable equipment or tank nozzle loads, or wind could possibly, although probably not, cause pipe stresses to exceed B31 simplified short-term allowable stresses. You may judge that a wind analysis is not necessary based on piping location and environment, but if wind is judged to be a credible short-term load, then analysis whether simplified (hand calculations) or more rigorous (computer aided) would be considered as required by the ASME B31 codes. If the piping is on a pipe rack, the problem is more complicated by the size of pipe, the exposed area of the pipe rack, and the connection of the piping to the pipe rack, but the same reasons above that would result in doing a wind analysis would also suggest a wind load analysis of piping on a pipe rack must be considered. In moderate seismic zones where the piping is also exposed to wind loads, both an earthquake analysis and a wind load analysis might be necessary to determine which short-term loading controls. But, the ASME B31 codes do not require earthquake and wind to be considered at the same time.
Mr. Ron Haupt, P. E., of Pressure Piping Engineering (www.ppea.net) is a member of several piping code committees (BPTCS, B31, B31.1, B31.3, and others). He has served with us in the capacity of Nuclear QA Manager.