Wind-resistant Structural Optimization Of Super-tall Buildings Base On The Wind-tunnel Test Of High Frequency Force Balance

Super-tall buildings,with the characteristics of large flexibility,small damping,etc,are typical wind-sensitive structures,and wind load is one of the horizontal controlling loads for this type of structures.The main way to acquire the wind loads acting on super-tall buildings and to assess the wind effects on structures is wind tunnel test.Based on the wind-tunnel test of high-frequency force balance(HFFB),this paper carried out an intensive study on several key issues of the wind effects on super-tall buildings and wind-resistant structural optimal design.The major work and inovations include:(1)Based on the principle of Rayleign Quotient and the Work-Energy transformation principle,the internal strain energy functions of three kinds of cross-section types including the concrete-filled steel tube section,box section and I-section were formulated and then the function of natural frequency constraint on structure was established.A tall building with a 21-story frame structure was taken as an example to illustrate the correctness of the structural natural frequency constraint and the feasibility of wind-resistant structural optimal design method.(2)The HFFB wind tunnel test was carried to study the wind effects on the CAARC building model.Two methods are respectively used for analyzing the wind-induced response of the structure and the results show that it will lead to the response calculation error without considering the correlation of background and resonant response.Therefore,it is necessary to consider the correlation of background and resonant response when computing the wind-induced structural response.A method was studied on computing the equivalent static wind load(ESWL)based on the HFFB wind tunnel test.One example was used to show the necessity and correctness of the method.(3)A super-tall building,46-story frame structure,was used to conduct wind-resistant optimal design based on the HFFB wind tunnel test.The mathematical model of super-tall building using for wind-resistant design optimization and the relationship between power spectral desity of aerodynamic bending moment and natural frequency was established.With the acceleration being explicitly formulated,the acceleration constraint can be transformed into the structural natural frequency constraint.Optimization results show that the structure can meet the requirements of safety and serviceability and the structural total cost reaches minimum after design optimization while the initial structure can not meet the requirements,which means it is meaningful for super-tall buildings to conduct wind-resistant design optimization.Moreover,in order to study the influence of different wind climate on total cost after optimization,the structural optimal design was carried out under different wind climate.Finally,the relationship between the reference wind pressures and total cost after optimization was established.(4)In order to consider the influence of wind directional factors and to determine more reasonable wind load for design,a super-tall building with a 46-story frame structure was used to conduct wind-resistant design optimization based on the HFFB wind tunnel test,using the wind climate model in Guangzhou provided by the third-party consulting company.Optimization results indicate that considering wind directional factors could broaden the optimization space,and at the same time,the objective function is lower under the condition of satisfying all constraints than that under single wind direction without considering the wind directional factors,indicating the necessity and significance of considering the effect of wind directional factors.In addition,the displacement response was explicitly formulated with respect to the structural natural frequency based on HFFB technique.Then the displacement constraint was transformed into the structural natural frequency constraint in the structural design optimization.At last,compared to the optimization result of using virtual work principle to establish displacement constraint,the optimization result of using natural frequency to establish displacement constraint is reasonable,and the total costs of two kinds of methods after optimization only have a difference of 0.7%,which shows that the method is correct and feasible.