huangyhg

asce 7, wind loads
colleagues;
i have never used this spec. and have a few stpuid questions as follows;
a. section 6.4.2 requires to calculate appropriate pressure or force coefficients per provisions of 6.7.
b. section 6.7 says look at figs 6-3 thru 6-8 for pressure coefficients & table 6-4 thru 6-8 for force coefficients (include gust factor).

questions
1. for outside piping should we use both pressure & force coefficients? if yes, then the pressure coefficients are not defined in fig. 6-3 thru 6-8 for outside "non structure" piping. my guess is that we should only use the force coef. per table 6-7. which leads me to believe that we only need to calculate the forece on the system per expressions given in table 6-1.

2. table 6-1 if the fundamental frequency of the system is <1 hz, then to calculate force on a pipiing system we also need to calculate gf (the gust factor) by rational analysis. what they mean by rational analysis? how is that done?

thanks in advance,

providing that you are only looking at wind loads to provide support for the pipe. you don't need to be concerend with internal pressures since your pipe should be a closed system. using asce7-98, consider this an open structure to determine the wind force. then all you need is the velocity pressure, 6.5.10, gust factor, 6.5.8, and net force coefficient, table 6-10. this should give you the loads you are looking for.
agree...your pipe would be classified in asce 7 as "other structures" and would be comparable to a sign or other similar structure, so a force coefficient is appropriate.
i also agree. section 6.7.1 tells where to find the force coefficients and where to find the pressure coefficients. the pressure coefficients are intended for use with buildings, the force coefficients are intended for use with other types of structures, e.g. pipe racks, equipment support structures in an industrial plant, equipment itself, etc. these all are examples of structures that have no cladding or skin.
you use either force coefficients or pressure coefficients. what you have described, looks like it should use the force coefficients for open signs and lattice structures for the supports and probably the ones from table 6-7 for the piping.
regards,
chichuck

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