| For their characteristics of high flexibility and low damping, high-rise lattice structures are highly sensitive to wind load. Previous studies on stability of structural system under wind load mainly are focused on large-span space structures and shells, while the researches on wind-resistant optimization of tall lattice tower are relatively few. Therefore it is necessary to conduct the studies on the optimal design of high-rise lattice structures by considering its wind resisting stability. A 27m-height tall lattice tower is selected as a research example in this thesis. By considering the nominal critical load factors(such as first-order elastic critical load factor, first-order nonlinear critical load factor and second-order elastic critical load factor) under different solution procedure, the comprehensive analysis of wind resistant optimization design of this lattice structure was conducted by combining the genetic algorithm, MATLAB programming developing environment of Applied Program Interface(API) supplied by finite element software Mastan2. The total volume(weight) of the structure is selected as the objective function. The critical load factors are adopted as the constraint conditions, and the size of the structural elements is selected as optimized design variables for the structural optimization design procedure. The main content of this thesis are described and listed as the following:(1) Wind-induced dynamic response analysis is conducted by SRSS method in random vibration theory. Thus the equivalent static wind load was obtained by IWL-based algorithm..(2) The methodologies and detail procedures of nonlinear stability analysis of tall lattice tower are summarized in the thesis, and the advantages and disadvantages of each algorithmfor obtaining the critical load factor is compared. Accordingly, work control based incremental-iterative method is selected to calculate the second order elastic critical load factors of the lattice tower.(3) The basic theory of SGA and the shortcomings of SGA are summarized, and the improved algorithm is proposed in this paper. First the initial population is supplied by diversity evaluation function rather than in a random manner. This treatment could result in a series of advantages, which includes covering space with little uncertainties, expressing spatial information with minimal number of individuals. Secondly, the proposed improved self-adaption strategy offers suitable crossover rate and mutation rate to solve the problem of numerous individuals converging on the vicinity of average fitness. Thirdly, static penalty function is replaced by dynamic penalty function in the process of optimization. All these improvements will adjust the ratio of feasible and infeasible solution reasonably during the evolution periods.(4) Wind optimization design of lattice structure with different constraint conditions of first-order elastic critical load factor, first-order nonlinear elastic critical load and second-order critical load factor with geometrical nonlinear effect are conducted while updating in the equivalent static wind load are carried out during the optimization procedure.Optimization results with different constraint conditions in critical loads factors are analyzed.It shows that the optimization results with updated equivalent static wind loads are less than those optimized results with constant equivalent static wind loads. Through the comprehensive study in this thesis, wind-resistant optimization design of high-rise lattice structure by genetic algorithm and critical load factor is achieved. Meanwhile an integrated wind resistant optimization design system is proposed in this thesis, which contains the solution and updating equivalent static wind loads, structural stability analysis and the application of genetic algorithm. |
