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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 dynamic 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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It's generally perceived that creating time history cases is time consuming with a steep learning curve, another factor which may have nudged engineers to use DLF. CSiPlant's ability to import time history data from text files with automatic consideration of scientific notation is straightforward, and can save a ton of time as compared to manually entering time history load data. CSiPlant can import time history data from most commercial piping fluid transient software programs, and most seismic ground motion records as-is with little additional effort. For cyclic dynamic loads, CSiPlant has built-in features to automatically generate sine and cosine time history functions for different machine speeds. Once time history load functions have been imported, a CSiPlant time history load case can be defined in only a few minutes.
In a few some scenarios, DLF can be unconservative if the dynamic excitations match the resonant frequency of the piping. A major disadvantage of DLF is that it ignores the frequency of the dynamic excitations.
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