Seismic Response And Design Method Of Sliding Base Structures

Sliding base(SB)systems are efficient for protecting low-rise buildings in high-seismicity rural areas,especially for western areas in China.It has become a kind of mature base-isolated technique.Many scholars have carried out many studies on the response mechanism of sliding base structures under earthquake excitations.But the focuses of existing researches were on the verification of the effectiveness of sliding base systems,most scholars only employed very few(no more than 3)ground motion records,so comprehensive mechanism of seismic response and simplified equation have not been proposed.The seismic response of sliding base system under three-dimensional earthquake excitation are investigated herein.The main results are as followed:(1)The normalized peak pseudo-acceleration(NPPA)of one-story SB structures under three-component earthquake excitation and its dependency on various structural and ground motion characteristics are investigated herein.The relationships between the NPPA and the normalized peak ground acceleration(PGA)are basically identical for both orthogonal horizontal directions.The vertical earthquake component can either increase or reduce the horizontal superstructure response,and for most cases,its effect is negligible.The ratio of the natural periods in the two orthogonal horizontal directions and the difference between the static and dynamic friction coefficients,as well as the earthquake magnitude and source-to-site distance affect the superstructure responses of SB structures little.Local site conditions affect the superstructure response,sites on softer soils display larger NPPAs.However,this effect decreases rapidly as the normalized PGA increases.For a given site class,mass ratio and normalized PGA,the NPPA probability distribution approximately follows a normal distribution.And simplified equations with associated regression coefficients were proposed to estimate the mean values and coefficients of variation(COVs)of NPPAs.(2)The normalized peak sliding displacements(NPSD)of one-story SB structures under three-component earthquake excitation and its dependency on various structural and ground motion characteristics are investigated herein.Compared with the peak ground acceleration(PGA)and peak ground displacement(PGD),the peak ground velocity(PGV)and the sliding displacements of SB structures have the best correlation.The relationships between the NPSDs and the normalized peak ground velocity(PGV)are basically identical for both orthogonal horizontal directions.The vertical earthquake component and the ratio of the natural periods in the two orthogonal horizontal directions have little influence on the sliding displacements of SB structures.Sliding displacements under pulse-like earthquakes are different from it under non-pulse-like earthquakes.And finally,a simplified formulation for the sliding probability and the geometric mean and the geometric standard deviation of normalized peak sliding displacement under sliding were proposed for non-pulse-like and pulse-like earthquakes,respectively.