Reliabilility Assessment of Model error of Reinforced Concrete Framed Structures

Abstract

The past earthquakes in which many concrete structures are severely damaged have indicated the need for evaluating the seismic adequacy of existing buildings. In which particular, the seismic rehabilitation of older concrete structures in high seismicity areas is a matter of growing concern, since structures vulnerable to damage must be identified and an acceptable level of safety must be determined. To make such assessment, simplified linear-elastic methods are not adequate. Thus, the structural engineering community has developed a new generation of design and seismic procedures that incorporate performance based design of structures. This approach moves away from simplified linear elastic methods and towards a more non-linear technique. Recent interests in the development of performance based codes for the design or rehabilitation of buildings in seismically active areas show that an inelastic procedure commonly referred to as nonlinear  analysis is a viable method to assess damage vulnerability of buildings.

The main focus of the present work is to carry out the analysis on bare rigid reinforced

concrete frames of 10 and 15 storey of two bays. The objective is to understand

the non-linear behavior of reinforced concrete frames under earthquake loadings of much

higher magnitude that takes the structural frame to a level beyond the elastic limit and upto

failure stage. For this purpose incremental lateral load is applied to the frame and the

curves are plotted which indicate the positions of capacity curve of the frame and

seismic demand curve depending on magnitude of shaking. This graph can suggest the

seismic performance of a system and its adequacy against the design earthquake. In this study an attempt was made to understand the seismic capability of frames designed it for different zones of earthquake  for maximum considered earthquake. Capacity-demand spectrums were plotted for frames with different number of storey and bays.

The uncertainties in loads, strength and geometry of structure are accounted in the reliability analysis. There are two types of uncertainties namely aleatory and epistemic. If model error equal to 1, then the model is perfect. Otherwise the model has to be improved based on the location hinges in the beams and column. We have used in this study a generalized beta distribution to

analyze the model error.