RESPONSE OF LONG CONCRETE STRUCTURES IN PLAN IN SEISMIC REGIONS

The dynamic analysis of structures which the length in plan is commensurable with the length of the seismic wave presented in this paper, is based on the energy conservation principle.In this type of structures, it is necessary to take into account the influence of the higher modes of the structure under consideration.The modeling of the structure as well as the arbitrary choice of a deformation shape play a capital role in the real distribution of masses for the evaluation of the design seismic load.The determination of the dynamics characteristics of this category of structures, compared with the existing seismic building codes ; seems however very appreciable. The influence of the higher modes remain remarkable, and this depends on the seismic norms of each country.For long structures in plan, the influence of higher modes determined by the energy of Raleigh’s method is a direct function of local norms and recommendations of the country concerned (macro-zoning and micro-zoning maps of the region ).The result obtained in the evaluation of the seismic load varies according to the nature and the characteristics of the structure (e.g. Results are very impressive for structures presenting a high flexibility ).