Comportement et performance plastique de structures multi-étagées et multi-travées.

Abstract

The present thesis has for object the study of the effect of the simulation of the vertical loads and the influence of the ratio, ɑ = V/H (where ɑ varies from 0.1 to 15), between the vertical concentrated loadings, V, and the horizontal concentrated loadings, H, applied at the junctions column-beam, to the collapse mechanisms and the collapse loads of a reference frame (two storeys, two bays). For this type of structures, the determination of the true collapse mechanism can be done by the various methods existing in the plastic analysis of the structures, namely by the method of limit analysis by combining the different elementary mechanisms, m, (m = p - r, where p represents the number of critical sections and r the degree of redundancy) until the obtention of the smallest load factor, ʎ, or by the method step by step until the obtention of the (r+1)th plastic hinge. The last two methods are extremely hard for a frame exceeding a storey and a bay (degree of redundancy, r, high, increase in the number of critical sections), because part of the work should be done manually. For that, it was considered necessary to choose another nonlinear static method known as pushover by using software SAP2000. The latter deals with the phenomenon of redistribution of the moments, and facilitates the obtention of the true collapse mechanisms and in fact the determination of the true collapse loads. The analysis of the results allowed the construction of interaction diagrams similar to those for simple frames and this for different values of the ratio, ɑ, and for the three simulations of vertical concentrated loads selected. This construction being given in the literature only for simple frame (single storey, single bay). Moreover, the analysis also made it possible to identify the modes of collapse of the reference frame and this for different ranges for the ratio, ɑ.