Optimal Design And Seismic Mitigation Performance Of Suspension Structural System

Suspension structure system is a new type of structure system with good development prospect.The suspension pendulum isolation system is to install the entire upper structure on the suspension pendulum,but there are few studies on the suspension device located in the middle of the floor.When the suspension device is located on the top of the structure,it is similar to the suspension pendulum tuned mass damper(PTMD).The damping component in PTMD generally adopts a separate design,which moves in one direction and produces a deflection angle in engineering.This paper investigates the work mechanism of suspension structure system with the suspension device at different positions of structures.A new optimization design method is proposed and its damping performance is verified in the structure,which enriched the application range of suspension structures.The effects of nonlinear factors and damper deflection angle factors on the response of structure-PTMD system under different structural parameters are studied,and the optimal design method is proposed.The problem of neglecting the deflection angle of damping element in the original design is improved,which provides a certain theoretical basis for practical engineering.The main contents are as follows:(1)The complex mode method is used to analyze the dynamic characteristics and control mechanism of the two-degree-of-freedom model of the suspension structure.The feasibility of the suspension structure system being simplified to two-degree-of-freedom analysis is verified by analyzing the modal and mode participation coefficient of a multi-particle inter-story shear model.The energy method is used to analyze the influence of the suspension position,the length of the pendulum and the periodic changes of the lower substructure on the dynamic response of the structure to further explain the work mechanism of the suspension structure.When a suspension device with a certain length is installed in the structure,the dynamic response of the upper substructure can be greatly reduced,but the response of the lower substructure may be amplified,so it is necessary to optimize the design of the suspension structure system.(2)An optimization method that comprehensively considers the displacement response of the overall structure is proposed by introducing the weight coefficient.The theoretical solution of the optimal design parameters with high accuracy and good stability is derived.Through the analysis of system parameters under different weight coefficients,the results show that the optimal damping and frequency ratio of the suspension structural system are positively and negatively correlated with its mass ratio,respectively.The optimal parameters all increase with the increase of weight coefficient.The optimized method makes the weight coefficient iterate from a very small value,which can minimize the seismic response of the lower substructure under the premise of linearization requirements for the swing displacement of the suspension device.(3)The control strength of the suspended structure system on the upper substructure increases with the increase of the weight coefficient.When the building is located on a soft site,the displacement attenuation rate of the lower substructure decreases more;while the displacement attenuation rate of the upper substructure increases less,and its rising speed is less than the falling rate of the displacement attenuation rate of the lower substructure.The suspension structure system can effectively control the seismic displacement response of the upper and lower substructure at the same time,when the weight coefficient is within a reasonable range.The pendulum device can still control the acceleration response of the structure and the control effect of the upper substructure is better under this optimization objective.The acceleration attenuation rate of the upper substructure reaches about 50% under the different site conditions,and decreases with the increase of weight coefficient.(4)According to the actual force of damper,the motion equation of the structure-PTMD system is derived.The effects of nonlinearity and damper deflection angle under different structural parameters on the frequency domain response of the structure-PTMD system are numerically analyzed under the condition of Gerges optimal parameters.The results show that the pendulum angle of PTMD is slightly larger than 30°and the damper deflection angle is greater than 7 °,the damper deflection angle cannot be ignored when the pendulum angle is the research object.The critical value above can be appropriately enlarged with the increase of the compressible length of the damper.Considering the influence of the deflection angle of the damper,the pendulum angle of PTMD and the critical value of the deflection angle of the damper can be enlarged a little when the displacement of the main structure is taken as the research object.(5)The optimization of the nonlinear PTMD considering the deflection angle of the damper based on the H_∞ criterion can better exert the energy dissipation performance of the damper.From the analysis of the engineering structure in this study,it can be seen that after optimization by H_∞ criterion,compared with optimization by Gerges parameters,the energy dissipation capacity of the damper is increased by nearly half,it is increased by 46.79% in the minor earthquake and 46.91% in the moderate earthquake.When the response of the main structure is reduced,the stroke of PTMD is reduced more,and the peak response of the pendulum angle of PTMD is reduced by more than 20%.At the same time,the greater the seismic load on the structure,the better the control effect of the damper.