Study On Critical Distance Of Adjacent Structures Based On Seismic Pounding Fragility

When the strong earthquake happens,there are many cases showing that a high probability of collision between adjacent structures exists because of the response differences caused by their various dynamic characteristics.Poundings always generate structural or architectural damages,even collapse of the whole buildings,endangering the safety of human life and property and bringing great economic risks.In recent years,much emphasis is given to the performance-based seismic design which makes it necessary to reduce the pounding risks through a more advanced,accurate and efficient assessment method based on reliability theory.In view of this,it has great theoretical significance and engineering application value to do performance evaluation on the critical distance between adjacent buildings in China which is one of the most earthquake-prone countries.In this study,the performance-based seismic design theory is applied to seismic performance evaluation of adjacent structures.With the reliability theory,the seismic pounding fragility of adjacent structures is proposed,and the calculation of critical distance is expressed as an inverse reliability problem,then the value corresponding to a specific pounding probability can be derived by an error-actuated iterative procedure.Finally,the shaking table tests are conducted to investigate the pounding responses of two multiple-storey steel framed model structures and to verify the correctness and validity of the theory mentioned above.The main results of this study are as follows:(1)By means of the random vibration theory,the non-geometric spectral characteristics,time-variant bandwidth parameter and failure probability of random response processes of linear elastic systems are derived,then the seismic fragility of single building is calculated.(2)With the reliability theory and considering a continuum of site hazard levels,the mean annual frequency and exceeding probability over 50 years of the relative displacement at potential pounding location of adjacent buildings exceeding a fixedcritical distance are obtained,and then the critical distance corresponding to a specific pounding probability can be calculated.(3)A series of shaking table tests of two multiple-storey steel framed model structures are conducted,one two-storey and another three-storey steel frame models whose added mass is placed symmetrically are designed with a 1/3 scale.The relative displacement responses of pounding storey of the frames under various earthquake intensities and critical distances are measured to verify the correctness and validity of the theory mentioned above.