Limitation of displacements of frame buildings under seismic impacts

Abstract

Plastic strains develop in constructions of reinforced concrete frame buildings under seismic effects. In the design of buildings using the spectral method they are taken into account implicitly during the determination of seismic loads by the introduction of reducing factor of allowed damage. But their values must be limited in order to prevent the destruction or to eliminate the development of unacceptable damage of bearing constructions. The experimental two concentrated force test of 15 hinged beams has been conducted. The first series reference beams were tested by the monotonously increasing load up to destruction. The beams of the rest six series were loaded until the specified value of plasticity coefficient by reinforcement strains was reached. Then the beams were turned over and were loaded according to the same scheme up to destruction. According to the results of experiment it was established that the maximum plastic strains value in the tensile reinforcement influences sufficiently on the stress-strain state, bearing capacity and destruction mechanism of reinforced concrete bending elements when changing the sign of internal forces. The limit values of coefficient of plasticity preventing the formation of through unclosed cracks under seismic loads are determined. A simplified method of determination of the limit value of maximum displacements of reinforced concrete frames under seismic impacts has been suggested.