Analysis Of The Performance Of Steel Reinforced Concrete Long Cantilever Structures Under Vertical Seismic Action

Steel reinforced concrete long cantilever structures have a pivotal position in high-rise modern complex buildings for its numerous advantages,and at the same time,its mass and stiffness distribution in a building with long cantilever structures is not uniform,and also its internal forces are complex,resulting in the higher difficulties in its seismic performance analysis.A large number of seismic records,however,have indicated that in high intensity areas the effect of vertical acceleration component of the ground motion is considerably significant.It is necessary,Therefore,to investing the seismic performance under the vertical earthquake action for the steel reinforced concrete long cantilever structure.In this paper,the steel reinforced concrete long cantilever corridor of a high-rise building has been investigated by using ETABS2015 software to construct the finite element model of the structure.First,the modal analysis was conducted,its results show that the effect of high-order modes is significant in the seismic analysis involving vertical ground motion.Then by adopting mode-superposition response spectrum method calculation was carried out for the seismic response of the structure respectively under the horizontal bidirectional earthquake and three direction earthquake.Results show that vertical seismic earthquake hardly has effect on horizontal displacement of the structure,but vertical seismic earthquake has a significant influence on vertical displacements of joint and mid-span of frame beams,axial forces of frame columns and diagonal braces,mid-span moments of beams and moments at beam ends.Further the elastic time-history seismic analysis of the structure was carried out by selecting three earthquake waves to investigate the seismic response of the structure in the case of two and three directions earthquake and their results were compared.The results show that response spectrum method and time history method reach similar conclusions that the horizontal displacement curve of the joint and the horizontal displacement curve of the beam in the two analytical methods almost coincide each other,the vertical seismic action has little effect on the horizontal displacements of the joints and mid-span of the beams,while the effect on increasing the vertical displacement of nodes and spans are obvious;the vertical earthquake has a great influence on the internal forces of the structure,the axial forces of the frame column increase severely under vertical seismic action,and also the effect is gettingsmaller with the increase in height,and also the greater the beam spans,the more significant the vertical seismic action.Both elastic response spectrum analysis and time-history analysis show that for a steel reinforced concrete long cantilever structure,the effect of vertical seismic action is significant and hence great attention should be paid to it so as to ensure the safety and serviceability of the structure.The research results in this paper,therefore,can provide reference to the design and construction of such structures.