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Similarly, in seismic zones, design results using a static seismic load approach are not usually compared with results using time history dynamic analysis. However, unlike the use of DLF, at least the static seismic loads are usually based on codified values which have some justification. Time history analysis would offer a more realistic distribution of seismic loads because mass is typically not evenly distributed in a piperack structure, particularly rack structures supporting heavy equipment and with piping.
Most piping stress models have nonlinear boundary conditions (gaps, friction, one-way supports, etc.) for nonlinear static analysis, yet most legacy piping stress programs are incapable of nonlinear time history analysis. That means that in order to run time history cases, engineers have traditionally had to linearize all nonlinear supports for the dynamic analysis, which is a dubious approach. This limitation likely helped push engineers toward the DLF alternative. CSiPlant can easily account for nonlinear boundary conditions in nonlinear time history cases.
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