Nonlinear static and linear dynamic analyses of RC buildings - Comparison of various modelling approaches

Abstract

In the past years buildings designed in Albania suffered from lack of seismic resistance and this is shown by the number of destroyed buildings due to effects of earthquakes. Thus, evaluating the seismic performance of the buildings, is an urgent matter as part of the steps in handling the impact of earthquakes. The present thesis is concerned with methods of nonlinear static and linear dynamic analysis of structures,particularly for application to geometrically nonlinear space frames. Non-linear static analysis, such as pushover-based ones, have been continuously refined and improved along the past few years as a complement or even as an alternative to dynamic time-history analysis. It, has become a popular practice for performance-based building seismic design and many Codes have adopted this method in Seismic Retrofitting to evaluate structure seismic capacity. This is mostly due to its ability to identify design limit states of structure piers and failure modes and also ensure the progressive collapse sequence of damaged structures subjected to major earthquakes. This analysis includes certain simplifications and approximations that some amount of variation is always expected to exist in seismic demand prediction of pushover analysis. In this thesis modal pushover analysis were performed since modal deformed shape is closer to the real deformed shape during a real earthquake. Different modelling approaches were used and discussed such as lumped-plasticity approach wuth plastic hinge and fiber element approach. Every approach has its approximations and an evaluation of their accurancy of the results has been made which is related to the approximations involved in the theory of the procedures, structural properties and ground motion characteristics. Differnet models of the building were studied and evaluated in terms of earthquake resistance, redunancy, ductility etc. Analysis results show that plastic hinges model shows a greater plasticity,although it is a design method widely used in Albania due to its lower economic cost compared to the fiber elemet model.