Contribución al estudio de cargas sísmicas sobre edificios

Abstract

According to usual formulae to estímate seismic charges on buildings, strains and stress- es become infinite when resonance is reached. In many buildings proper periods are of the same order as those of the ground during an earthquake. It is to be expected therefore that they inevitably will break down, and there is no rule to dimensión their resisting structures. As these results do not seem satisfactory, the whole question is reviewed and it is shown that assuming for the ground a transient sinus movement with finite acceleration, and that the building is at rest at the beginning of the quake, strains become infinite when resonance is reached, only if duration of earthmovement is infinite too. Strains may be infinite, buildings being or not in resonance, when earthmovement acceleration is infinite. Since none of this cases is real, strains and stresses to be expected are finite. New formulas are given to calcúlate them. To do this, not only a reasonable period and an amplitude of the earthmovement must be given, but a reasonable finite duration too. Strains on damped buildings can be determined with formulae (54) and (66); on no damp- ed ones when there is resonance with formulae (59) and (68) and with formulae (55) and (67), when resonance is not reached.