摘要
框剪结构以其广泛的适用性及良好的抗震性能被大量的应用于我国的高层建筑中。框剪结构中由于剪力墙刚度大,水平力将主要由剪力墙承受,框架一般仅承受20%左右的水平力。所以在框剪结构体系中,剪力墙刚度的大小在很大程度上决定了整个结构的刚度。在进行结构设计时,框剪结构中剪力墙刚度的确定,除了必须满足强度条件外,还必须使结构具有一定的侧向刚度,以免在地震作用下产生过大的变形。结构刚度过小,会因结构产生过大的变形而无法满足正常使用要求;结构刚度过大,则自振周期相应减小,地震作用相应增大,从经济上造成不必要的浪费。
目前国内的工程设计中,高层建筑的设计普遍偏于保守,像在深圳框剪结构为主的高层住宅,剪力墙的厚度过大(可达500～600mm),数量过多,柱截面也过大,计算的相对弹性层间位移角只有几千分之一。由于材料的利用率低,使得工程造价提高。随着设计理论的日臻完善,计算工具的不断改进,寻求剪力墙数量的优化问题显得非常必要。
近年来,国内外学者提出了许多确定剪力墙数量的方法,但大多数都是对剪力墙数量的定性分析,用于定量分析的文献采用的计算模型较为简单,未能考虑剪力墙与框架之间的空间相互作用。
遗传算法在结构工程中的应用主要集中在桁架和框架结构优化上,将遗传算法应用于框剪结构抗震墙数量的优化设计,在国内外尚属少见。本文采用遗传算法作为结构优化方法,用振型分解法计算地震作用,计算中采用框剪结构空间协同分析的离散化方法,用有限元思想将结构离散为杆单元,分析过程中考虑了结构整体工作性能的主要特征及剪力墙剪切变形的影响,计算和分析了剪力墙的合理数量。在此基础上沿高度又进行剪力墙厚度的二次优化,使其更接近实际最优剪力墙量。
本文提出用遗传算法对框剪结构抗震墙数量进行优化设计,是结构优化方面的一种新的尝试,拓宽了该方法在结构优化设计中的应用范围,具有很大的发展潜力。
结构设计时,框剪结构抗震墙刚度的确定一般是先通过经验公式进行初步假定,然后进行不断验算最终确定。本文优化程序的编制,可以在结构初步设计阶段,简捷、正确地确定框剪结构中抗震墙最优数量,避免了重复、烦琐的结构刚度调整计算,从而减轻了结构设计人员的工作强度。
Frame-shear wall structures are applied widely in high-rise buildings in our country for its good serviceability and well aseismatic capability. In this structure, the horizontal load is mainly supported by shear walls because of their large rigidity, and only about 20% of that is supported by frames, therefore, the rigidity of whole structure is mostly determined by that of shear walls. In structure design, the rigidity of shear walls should not only satisfy strength, but also have certain lateral rigidity to prevent excessive distortion. If the rigidity is too small, the structure may distorted excessively and can’t meet with the require of normal application, if it is too large, the natural period of vibration will decrease and seismic action will increase accordingly, and it is also a waste of material.
In our country, the design of high-rise buildings is generally too conservative, for example, in the high-rise apartments with frame-shear wall structure in Shen Zhen, its shear walls is too thick (can reach 500～600mm) and too much, the section of its column is too large, the maximum elastic displacement angle between floors calculated is very small. Its material is not sufficiently used, and the cost is highly increased. As the development of calculation theory and improvement of calculation tools, it is very necessary to find a way to optimize the quantity of shear walls.
Recently, scholars home or abroad advance many methods of calculating the quantity of shear walls, but most are qualitative analysis. The models, established in quantitative analysis and ignoring the spatial interaction between shear walls and frames, are comparatively simple.
Genetic algorithm is mostly focus on the optimizations of truss and frame structures, and we know a little about it in optimizing of quantity for shear walls in frame-shear structures. In this paper, the author calculates the optimum quantity of shear wall by adopting genetic algorithm. Adopting mode analysis method to calculate seismic action and breaking up the whole structure into bars with finite element method, the model established can deal with the spatial characteristics of the building and the shear deformation of shear walls. After that, the author carries out the second optimization on quantity of shear wall along the altitude, and makes the analysis results more close to the optimal one.
The application of genetic algorithm on optimum design of quantity for shear walls in frame shearstructures is carried out in this paper, this method is a new try
The application of genetic algorithm on optimum design of quantity for shear walls in frame shear structures in this paper is a new attempt in structure optimization, broadens its applying area, and has great developing potential in this area.
Generally, to ascertain the rigidity of shear wall, a value is assumed primarily according to the experimental formula, then the value is adjusted again and again until it is ascertained ultimately. The optimum program in this paper can ascertain the optimal quantity of shear wall in frame shear structure easily and correctly, avoid repeated and fussy adjustment of structure rigidity, therefore greatly alleviate the working intension of structure designer.
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