Investigation Of Seismic Performability Of RC Structures

Abstract

The main shortcoming of the seismic design is that the seismic performability of the RC structure is calculated without allowance for the basic properties of materials and to the previous loading history of the element. The concrete, the reinforcement and the section of the element as a whole in bending are analyzed on the basis of the three-curve, a two-curve and four-curve diagram respectively. In term of limit elastic stress in concrete, the design compression strength is equaled to half of its characteristic bending strength. It was assumed that the gravitational compression stress of the RC section must not be more then that level. Taking into consideration the damage of the overreinforced section the theoretical based maximal reinforcement sections for the compressive and tensile zones of the RC section are given. The method for tensile reinforcement ultimate deformation definition is given. The problem of the symmetrical reinforced structure for the seismic zone is analyzed. The theoretically based stress – strain relations of the RC section components for the cyclic loading are applied. For each “loading – unloading” half cycles, the energy dissipation level is accounted. It is shown that the accumulated section energy dissipation under cyclic loading significantly differs from the static one. The definition of the RC structure seismic performability is formulated. It includes the traditional strength analysis as a necessary condition and energy dissipation control as a sufficient one. The design procedure of the seismic performability of the RC structures is given. The proposed approach is conveniently demonstrated via numerical examples for simple RC sections of columns and beams. The results of the study may be used as basis of new seismic design codes.