Performance Assessment of RCC Structure Using Nonlinear Analysis

Abstract

In general, the performance of the structure under earthquake vibrations is not limited to linear analysis. Linear analysis can be done to identify the preliminary parameters like natural frequency and damping ratio of the structure. To understand the structural behaviour beyond the linear elastic region, non-linear analysis is mandatory. Nonlinear analysis reveals the structural performance under the elasto-plastic state. A large deformation in the plastic region alarms the system sustainability under random motions. The quality of ductility is considered for the ratio of yield strength of the linear system to the maximum strength of the elasto-plastic system. The ductility demand versus response reduction factor of the structure is plotted. Design modifications can be done based on the ductility demands for various response reduction factors. Two structures of uniform and non-uniform varying cross-sections are considered in the study. Modal analysis is performed based on approximate and analytical methods to find the fundamental frequencies of the structures. Both the structures are identified at a linear curve of yielding to the ultimate capacity in the pushover curve. Linear time history analysis is performed to identify the performance point of the structure in the pushover curve. Non-linear dynamic analysis is performed to find the response of the structures using the Newmark method of non-linear time history analysis. The results arrived at the linear response which is validated with the linear time history analysis using ETABS. To have the response decay in the structure, peak strength in the elastoplastic range is assumed as the normalized yield strength factor. Based on the yield strength factors, ductility demand in the structure is identified.