Non linear structural analysis: application for evaluating seismic safety.

J. C. VIELMA; A. BARBAT; S. OLLER

Structural Analysis

Nova Science Pub Inc

Año: 2010; p. 101 - 128

Performance-Based Design is currently accepted commonly as the most advanced design and evaluation approach. However, successful application of this procedure depends largely on the ability to accurately estimate the parameters of structural response. Determination of these parameters requires application of analysis procedures where the main non-linear behavior features (constitutive and geometrical) of structures are included. This chapter presents and discusses these features of non-linear behavior and how they are incorporated in the process of static or dynamic structural analyses. Non-linear analysis leads to determination of significant structural response parameters whenever estimating seismic responses such as ductility, overstrength, response reduction factor and damage thresholds; being these the main response parameters for evaluating the seismic safety of structures. In order to illustrate application of the non-linear procedure being described, a set of concrete-reinforced moment-resisting framed buildings with various numbers of levels was selected. These buildings were designed according to ACI-318 [1] for high and very high level of seismic hazard. Seismic safety of regular concrete-reinforced framed buildings is studied using both the static and dynamic non-linear analyses. Static analysis consists in using the pushover procedure and dynamic analysis is done by using the incremental dynamic analysis (IDA). Analysis was performed using the PLCd computer code [2] which allows incorporation of the main characteristics of reinforcement and confinement provided to the cross sections of structural elements (beams and columns). A set of 16 concrete-reinforced framed buildings with plane and elevation regularity was designed according to ACI-318 [1] and for loads prescribed by the ASCE7-05 [3]. Results obtained from static and dynamic non-linear analyses allowed calculation of global ductility, overstrength and behavior factors. Behavior factors are compared with design values prescribed by the ASCE7-05, in order to verify validity of design values obtained from the capacity curve, computed for normalized roof displacements corresponding to performance point. Additionally, five damage thresholds are defined using the values of inter-story drifts associated with several Limit States. Damage thresholds lead to obtain fragility curves and damage probability matrices, used in order to evaluate the seismic safety of the code designed buildings under study.