Change of Axial Forces in Layered Rubber–Steel Base Isolators of High-Rise Buildings at Earthquake Impact

Abstract

Seismic isolation technology makes buildings more capable of withstanding earthquakes, protecting them from major damages or collapse. The same methods of analyses are not suitable for all types of buildings. The isolation system used Armenia, unlike foreign countries ones, cannot take any tension forces since the system doesn't have structural connections to superstructure and substructure of a building. The consequence of this fact can be the occurrence of additional stresses after the redistribution of axial forces in rubber base isolations in high-rise buildings during a seismic action. The stress-strain state analyses of rubber base seismic isolation systems in reinforced concrete dual frame-wall buildings with application of a finite element method carried out in the manuscript. An increase of the stresses during seismic action is discussed and investigated using both Fast-nonlinear time history analysis (FNTHA) and Direct-integration nonlinear time-history analysis (DINTHA). Analysis of the results of the study shows that the axial forces after their redistribution during horizontal earthquake loads in most seismic isolators of high-rise building do not exceed 8%, but for some isolators this difference varies within the range of 12-18%. Taking into account the vertical component, the difference does not exceed 20%, with the exception of three isolators, where it can reach up to 23%. An average increase of the compressive axial forces in the seismic isolation bearing systems of the tall building as a result of redistribution can be taken about 10%. In this case, the displacements and the axial forces of the seismic isolators during analysis of their bearing capacity must be considered simultaneously, but not separately from each other.

Keywords

• base isolation
• high-rise building
• earthquake
• nonlinear analyses