Analysis of the dynamic response of a base isolated building during an earthquake with an intensity of 7 points on the MSK-64 scale

Abstract

Introduction. The problem is considered and the relevance of studying the behavior of buildings and structures with seismic isolation systems using lead rubber bearing under real seismic impact, as well as assessing their technical condition after the earthquake, is emphasized. The experience of studying the behavior of base isolated buildings under real seismic impact abroad and in Russia is given.
 Materials and methods. The dynamic parameters seismic isolation of a reinforced concrete building using lead rubber bearing are investigated. Registration of seismic vibrations of the building was performed by a stationary station for dynamic monitoring. The results of processing the records were obtained based on the interpretation of monitoring data, including harmonic analysis, determination of the power spectral density, as well as the application of wavelet transform methods.
 Results. The results of dynamic monitoring of a base isolated building of a sea terminal located in Petropavlovsk-Kamchatsky city during an earthquake of 04/03/2023 with a magnitude of Mw =6.6 and an intensity at the site of the building equal to 7 points on the MSK-64 scale are presented. An analysis of the response and dynamic parameters of the building was performed, as well as a visual inspection of structures, as well as the building's seismic isolation systems.
 Conclusions. Analysis of the dynamic monitoring results made it possible to identify the natural vibration frequencies of the building, as well as to trace their changes during seismic impact. The maximum displacements of the building indicate minor shear deformations of the lead rubber bearing corresponding to the zone of their elastic operation. Both the rigidity of lead rubber bearing and the dynamic parameters of the building (frequencies (periods) of natural vibrations and the logarithmic damping decrement of the building) change depending on the intensity of the seismic impact and the shear deformation of the bearings, respectively. After the earthquake, widespread cracks and peeling of the plaster wall were observed with partial exposure of the layer of insulating material in the zone of filling with elastic elements the gaps between the strapping beams of the seismic isolation system and the structures of the building partitions at the level of the seismic isolating layer, which did not affect the operational reliability of the building. The study presented in this article shows that with the help of dynamic monitoring of buildings and structures, one can get a more complete and detailed understanding of their dynamic behavior, identify damage in the structural system of a building, and detect their undesirable or specific reactions that could not be taken into account when designing.