IDENTIFICATION OF GEOMETRIC NONLINEARITY FORMULATIONS AND THE INFLUENCES ON STRUCTURAL DYNAMIC RESPONSES
Kevin K. Wong
Both ASCE/SEI 7-16 and ASCE/SEI 41-17 design standards require that P-D effects be included in the nonlinear dynamic analysis procedure for designing new and existing structures. However, software packages that perform nonlinear dynamic analysis typically only allow users to either turn on or turn off the effect of geometric nonlinearity without informing users what type of nonlinear effect is being included, such as whether both large P-D and small P-d effects are included. Coupling this geometric nonlinearity effect with material nonlinearity of the structure can lead to significant differences in the predicted responses, especially when the structure is at near-collapse. Therefore, study on how geometric nonlinearity can affect structural performance is important to performance-based seismic engineering. In this paper, a detailed formulation of the nonlinear stiffness matrices taking into consideration both geometric and material nonlinearities is derived for a column member. It is followed by a study on how different software packages implement different geometric nonlinearity formulations and identify whether such formulation include both large P-D and small P-d effects in the analysis. Finally, examples are presented to demonstrate how different formulations of geometric nonlinearity affect the nonlinear responses of framed structures.
Proceedings of the 17th World Conference on Earthquake Engineering
September 13-18, 2020
17th World Conference on Earthquake Engineering
Geometric nonlinearity, Material nonlinearity, Large P-D effect, Small P-d effect, Displacement