【正文】 法采用容許應力。 概率方法，這種方法采用極限狀態(tài)。 至少在理論上，概率法的主要優(yōu)點是可以科學的考慮所有隨機安全系數，然后將這些隨機安全系數組合成確定的安全系數。概率法取 決于： （ 1）制作和安裝過程中材料強度的隨機分布（整個結構的力學性能數值的分散性）； （ 2）截面和結構幾何尺寸的不確定性（由結構制作和安裝造成的誤差和缺陷而引起的）； 對作用在結構上的活載和恒載的預測的不確定性； 所采用的近似計算方法有關的不精確性（實際應力與計算應力的偏差）。 此外，概率理論意味著可以基于下面幾個因素來確定允許的危險率，例如： 建筑物的重要性和建筑物破壞造成的危害性； （ 2）由于建筑物破壞使生活受到威脅的人數； （ 3）修復建筑的可能性； 5 （ 4）建筑物的預期壽命。 所有這些因素均與經濟和社會 條件有關，例如： （ 1）建筑物的初始建設費； （ 2）建筑物使用期限內的折舊費； （ 3）由于建筑物破壞而造成的物質和材料損失費； （ 4）在社會上造成的不良影響； （ 5）精神和心理上的考慮。 就給定的安全系數而論，所有這些參數的確定都是以建筑物的最佳成本為依據的。但是，應該考慮到進行全概率分析的困難。對于這種分析來說，應該了解活載及其所引起的盈利的分布規(guī)律、材料的力學性能的分散性和截面的結構幾何尺寸的分散性。此外，由于強度的分布規(guī)律和應力的分布規(guī)律之間的相互關系是困難的。這些實際困難可以采用兩種方法來克服。第一 種方法對材料和荷載采用不同的安全系數，而不需要采用概率準則；第二種方法是引入一些而簡化假設的近似概率方法（半概率方法）。 6 2 外文翻譯 Abstract:To study the application of continuum structural topology optimization methods to real engineering structures,an optimization method for an optimal topology design of multistory steel frame bracing systems is a sensitivity analysis,an element removal criterion for continuum structures with stress and multidisplacement constraints under multiple lateral loading conditions is concept of mean thickness of a design domain is provided to ensure the reasonableness of optimal the proposed optimization method,the optimal design of an unbraced steel frame without displacement constraints is performed firstly,and then the optimal topology of a bracing system for the multistory steel frame considering displacement constraints is obtained by using evolutionary structural optimization and the given removal criterion,and finally the optima layout of the bracing system is interpreted as bracing example of 3bay 12story plane steel frame shows that it is effective for the given optimization method in the optimal design of bracing systems for multistory steel frames. Key words:steel frame。bracing system。continuum。topology optimization。evolutionary structural optimization Reinforced Concrete Plain concrete is formed from a hardened mixture of cement ,water ,fine aggregate, coarse aggregate (crushed stone or gravel),air, and often other admixtures. The plastic mix is placed and consolidated in the formwork, then cured to facilitate the acceleration of the chemical hydration reaction lf the cement/water mix, resulting in hardened concrete. The finished product has high pressive strength, and low resistance to tension, such that its tensile strength is approximately one tenth lf its pressive strength. Consequently, tensile and shear reinforcement in the tensile regions of sections has to be provided to pensate for the weak tension regions in the reinforced concrete element. It is this deviation in the position of a reinforces concrete section from the homogeneity of standard wood or steel sections that requires a modified approach to the basic principles of structural design. The two ponents of the heterogeneous reinforced concrete section are to be so arranged and proportioned that optimal use is made of the materials involved. This is possible because concrete can easily be given any desired shape by placing and pacting the wet mixture of the constituent ingredients are properly proportioned, the finished product bees strong, durable, and, in bination with the reinforcing bars, adaptable for use as main members of any 7 structural system. The techniques necessary for placing concrete depend on the type of member to be cast: that is, whether it is a column, a bean, a wall, a slab, a foundation. a mass columns, or an extension of previously placed and hardened concrete. For beams, columns, and walls, the forms should be well oiled after cleaning them, and the reinforcement should be cleared of rust and other harmful materials. In foundations, the earth should be pacted and thoroughly moistened to about 6 in. in depth to avoid absorption of the moisture present in the wet concrete. Concrete should always be placed in horizontal layers which are pacted by means of high frequency powerd