Method For Calculating Critical Separation Distance Between Nonlinear Adjacent Structures Based On Seismic Pounding Risk

The damage of non-structural members and structural members caused by collision of adjacent structures under earthquake action is a common seismic damage phenomenon.Setting enough adjacent structure distance is the main means to avoid and reduce earthquake collision damage.However,the minimum level of structural safety of each country is unknown.In order to adapt to the development needs of performance-based seismic engineering,it is urgent to propose a critical separation distance calculation method based on reliability.However,the probability calculation method for the critical separation distance of adjacent structures is limited to linear structures.Therefore,this paper considers the nonlinear characteristics of adjacent structures and studies the calculation method of the critical separation distance of adjacent structures based on seismic collision risk.The main work and conclusions of this paper are as follows:(1)A method for calculating the critical separation distance of nonlinear adjacent structures based on seismic collision risk is proposed.The basic idea of the method is that the risk of seismic collision of adjacent structures is solved as the reliability problem,and the corresponding critical structure to avoid the collision is the inverse reliability problem under the given collision risk condition,that is,the zero point.The problem can make the adjacent structures have consistent target failure probability.The seismic collision risk analysis method based on subset simulation is introduced to analyze the seismic collision risk,so that the proposed method can consider the nonlinear characteristics of adjacent structures.Firstly,the critical separation distance of linear adjacent single-degree-of-freedom structures is calculated,and the accuracy of the proposed method is verified.The effects of different period ratios and different site hazards on critical separation distance are analyzed.Secondly,the critical separation distance of nonlinear adjacent multi-degree-of-freedom structures is analyzed by the proposed method.The effects of adjacent structure mass ratio,interlayer stiffness ratio and inter-layer yield load ratio on critical separation distance are studied.The research shows that with the increase of the adjacent structure mass ratio,the critical separation distance first increases and then fluctuates;as the stiffness ratio increases,the critical separation distance decreases gradually;as the inter-layer yield load ratio increases,the critical separation distance increases rapidly and then remains unchanged.(2)Using the proposed method,the critical separation distance of adjacent reinforced concrete frame structures designed according to the current seismic code is calculated.The critical separation distances of adjacent six-and five-layer,adjacent six-and four-layer,adjacent six-and three-layer frame structures are calculated separately,and combined with the minimum anti-seismic joint width of the seismic code and the relative displacement of different adjacent structures.The structural distance values obtained by the rules are compared.The results show that the critical separation distance is related to the adjacent structure period ratio and the collision position simultaneously;and when the collision height and the period ratio reach equilibrium,that is,adjacent six-layer and four-layer frame structures,the critical separation distance is the largest and less than the specification limit.(3)The calculation method of seismic collision vulnerability is an important factor affecting the critical separation distance of adjacent structures based on seismic collision risk.In this paper,the incremental dynamic analysis(IDA)of single-structure seismic vulnerability analysis is extended for the calculation of seismic damage of adjacent structures.Taking adjacent six and five layers,adjacent six and four layers,adjacent six and three layer frame structures as examples,using frequency statistics method(exact solution),linear regression method,two-parameter regression method,bilinear regression method and the moment estimation method respectively calculate the vulnerability curve.The results show that the vulnerability curve obtained by the bilinear regression method is the closest to the exact solution.When the actual number of seismic waves used is limited,the fitting effect is best,and the smaller the dynamic characteristics of adjacent structures,the peak ground acceleration.The larger the distance between adjacent structures,the better the anastomosis effect.