Degradation of Dynamic Parameters of Reinforced Concrete Buildings during an Earthquake

Abstract

The article presents the results of a numerical study of the effect of local damage to load-bearing structures on the dynamic characteristics during an earthquake. The studies were carried out in the LS-DYNA software package, which implemented the nonlinear concrete model, Continuous Surface Cap Model (CSCM). The computational model of the building uses solid finite elements for concrete and bar elements for reinforcing bars. As the object of modelling, a 1-storey building with a frame structural layout was chosen. Studies have shown that during an earthquake with an intensity of 7 points, specified by the corresponding accelerogram, there is no change in natural frequencies, that is, the damage resulting from this earthquake is insignificant. During an earthquake with an intensity of 8 points, a significant (up to 55 %) reduction in natural frequencies occurs. This suggests that the structure is damaged, and the overall stiffness of the building is reduced. Analysis of the results shows that the most intense decrease in natural frequencies occurs in the active phase of an earthquake. After the end of the active phase, the frequencies stabilize and stop falling. The LS-DYNA software package enables to perform studies of the effect of local damage of the load-bearing structures on the dynamic characteristics during an earthquake with the direct reinforcement of concrete with reinforcing bars and can be used in the calculations and the design of buildings and structures.