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Static and dynamic analysis of inelastic frame structures

Porter, Frank L.; Powell, Graham H.

UCB/EERC-71/03, Earthquake Engineering Research Center, University of California, Berkeley, 1971-06, 119 pages (530/P66/1971)

A method is developed for the analysis of frame structures exhibiting both material and geometric nonlinearities and subjected to both static and dynamic loads. This method is applied to a variety of problems, with the use of two computer programs. It appears to be more general than previously reported analysis procedures. The frame members are assumed to yield at generalized hinges of zero length at the member ends. Hinge formation is governed by arbitrary yield surfaces composed of multidimensional planar facets. The material is assumed to be elastic-plastic, and loads are applied only at the joints. The tangent stiffness for an elasto-plastic member is first derived, and a consistent procedure is then presented for adding the geometric stiffness. A convenient technique for solving the equation of dynamic equilibrium for arbitrary support motions is developed, using a step-by-step method. The features of two computer programs are described. The first analyzes statically loaded plane frames, including determination of the post-collapse unloading behavior. The second performs a dynamic analysis on three dimensional piping systems assuming geometric nonlinearity can be ignored. Examples using both programs are presented.

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