Wind-Resistant Structural Optimization Of Tall Buildings Considering Parameter Uncertainties

Super-tall buildings are typical wind-sensitive structures which have the characteristics of large flexibility,small damping,etc.wind load is one of the horizontal controlling loads for this type of structures.Based on the rigid model synchronization pressure test,the international CAARC standard model is used as the research object.The structure of the total cost is the objective function,at the same time,using displacement,story drift and natural frequency as constraint conditions.From the point of view of probability,the reliability theory is used to analyze the influence of wind on the structure,and the research on the wind-resistance structure optimization design method for parameter uncertainties of tall buildings.The major work and innovations include:(1)By means of the relationship between Rayleign Quotient and the Work-Energy transformation principle,the acceleration constraint at the top of the structure is transformed into the natural frequency constraint and further converted to the strain energy constraint.The expression of the strain energy constrained function is established.One structural design optimization of 21-story frame structure which has variety of sections is taken as an example to consider different constraint conditions: displacement constraints(limit the horizontal displacement and story drift),the natural frequencies constraints of structure(limit structure acceleration)and displacement constraints and the natural frequencies constraints of structure.The results show that the design method with displacement constraint and the natural frequencies constraints of structure is reasonable,the optimization results also illustrate the correctness of the expression of natural frequency constraint and the reliability of windresistance structural design optimization method with OC optimization algorithm.(2)Through two different methods to solve the structure frequency limit,namely,the comparison between the constraint of modal acceleration and the actual acceleration.The Complete Quadratic Combination method(CQC)is used to calculate the wind-induced vibration response and most unfavorable wind direction is selected for optimal design of windresistance structural design optimization.Under the same deterministic parameters,the difference between the two results obtained after optimization is analyzed.The results show that modal acceleration constraints can achieve larger optimization space.(3)Considering some uncertain parameters of the building structure in the design process,such as: structural natural frequency,damping ratio and design wind speed,the influence of these parameters on the structural wind-induced response and wind-resistance optimization design results are analyzed.Based on reliability theory,the formulas for calculating the failure probability and the reliability index of the structure using the equivalent normalization method(JC method),reflection transformation method,and the Monte Carlo method combined with the design point method are deduced.At the same time,the limit state equation of parameter uncertainties is established by random variables with certain distribution.The limitation of structural natural frequency is calculated by means of the known reliability index,thus the structural comfort problem is expressed by the structural natural frequency,wind-resistant structural optimization is researched through displacement constraint and the natural frequencies constraints of structure.Compared with the results of deterministic parameter,greater optimization space is obtained after considering parameter uncertainties.(4)Introducing the wind directional factors model under wind climate in Guangzhou,this chapter shows the wind-resistance structural optimization of tall building considering the wind directional factors.After considering the wind directional factors,the most unfavorable wind direction angles of the top displacement and acceleration have all changed.Combining the reliability calculation formula to solve the structural failure probability and the limit of natural frequency,the wind-resistant structural optimization of CAARC standard model is studied.The results show that: after considering wind directional factors,a larger optimization space is obtained,the overestimation of wind load is avoided and the construction cost is reduced,so it is very necessary to consider Wind directional factors.