Torsional Displacement Amplification Of Base-isolated Structures

Technology of isolation have got promoted in high intensity earthquake zone,base-isolation structure will be more and more. It is important to note that isolated structures instance by major earthquake test is still rare at currently,the security and stability of the isolation layer under major earthquake is still in doubt. In consideration of the size of isolation layer,it is very important to control the security and stability of structure reverse to the isolation system. It is important and urgent to carry out the influence factors of torsional displacement response and control index study about the isolated structures under the condition of the major earthquake.The parameters affecting of the structure torsion has carried on the statistics,and paper obtained torsional displacement amplification coefficient of isolation bearing and other key indicators under the current design code,on the basis of appraisal theoretical analysis of structures’ reverse,depended on earthquake isolated actual engineering. Concrete results are as follows.(1) The equivalent torsion translation period ratio isolated engineering was between 0.7~ 0.9;traverse equivalent damping ratio was between 0.08~0.16,with a mean of 0.11;reverse equivalent damping ratio was less than 0.25 generally;the range of eccentricity was between 0.01~0.05, with a mean of 0.03;isolation layer edge support distance to severity centre and radius of gyration ratio is between 1.3~1.9.(2) When the traverse equivalent damping ratio of 0.10,reverse equivalent damping ratio of 0.25, period ratio of 0.9 and eccentricity ratio range of 0.01~0.05,the range of layer boundary displacement amplification factor is between 1.030~1.207. Thus it can be seen,the provisions of torsion effect coefficient should not be less than 1.2 in seismic code is an old-fashioned.(3) The sensitivity analysis of effect of vibration isolated parameters reverse shows that,in the actual engineering parameter range(reverse equivalent damping ratio was between 0.05~0.30),the influence of the eccentricity of torsional effect was the most obvious than equivalent period ratio,followed by reverse equivalent damping ratio and traverse equivalent damping ratio.