Secondly , a non - linear mapping function from multiple inputs ( design variables ) to output ( maximum dynamic stress ) is constructed within bp neural networks , in order to obtain the constraint function values that are necessary in optimum design of structures using genetic algorithms and get the optimum solutions . the generation ability of the bp network after training can be used to replace the calculation of fem , which makes the constrained optimization to be possible 其次,由于动应力的有限元法计算过程复杂,计算量巨大,在应用优化算法时,需要反复计算,为了使优化过程可行,设计了bp神经网络,利用有限元计算的样本数据建立起结构设计参数(输入)与动应力(输出)的非线性映射关系,从而代替有限元法,快速计算结构动应力。
For spatial , ideal elasto - plastic girder - pane structure system , using the stochastic finite element method , the static response of structural system is analyzed . taking redistribution of internal forces into account , safety margin functions of failure modes are established . using the advanced branch - and - bound method , the significant failure modes are identified , and the reliability of structural system is evaluated by pnet method 对空间理想弹塑性梁板体系结构,采用随机有限元计算结构系统的响应量;考虑内力重新分配,建立失效模式的安全余量方程,用验算点法计算失效模式安全余量的可靠性指标;用改进的分枝限界法,寻找主要失效模式:然后用pnet法计算结构系统的可靠性指标(或失效概率) 。
The main work and achievements are summarized as follows : according to the spectrum analysis theory , the simple formula of the power spectrum between the excitation and the response is obtained . then the time - domain statistical properties of the structural response are acquired through fourier inverse transform , and cauchy ' s residue theorem is applied to solving the integral of fourier inverse transform , the structural dynamic reliability is calculated in terms of possion hypothesis based on first passage failure 主要研究内容如下:从谱分析理论出发,得到了激励与响应功率谱之间的简明关系式,由fourier逆变换得到响应的时域特征,利用cauchy留数理论处理fourier逆变换的积分式,基于首超破坏的possion假设计算结构系统的动力可靠性,并在此基础上进行结构优化设计,奠定了确定性模型的基础。
The number of modes should be selected according to the participant coefficient of mode when calculating the internal force by the response spectrum method ; ( 4 ) the roof plate of large base which connect the towers together should be thick enough but not exceeding the proper scope that the towers and the large base can vibrate together , ( 5 ) in structures with large base and muti - towers , with increasing of the capacity of the large base , the inter - story shear force will increase while the inter - story displacement will decrease as to fulfill the ductility request to avoid the large base becoming weak story , but meanwhile , the upper story will turn into weak story , thus the coefficient r s should be within 2 . 0 ~ 3 . 0 采用振型分解反应谱法计算结构内力时应根据振型参与系数选择振型避免漏选;大底盘多塔楼结构连接各塔楼的裙房屋面刚度应做得大些,以保证底部裙房与上部塔楼共同振动,但也不能过刚;大底盘多塔楼结构底盘承载力的加强将使底盘层剪力增大、层间变形减小,但易于满足延性要求,在一定程度上可避免底盘成为薄弱层。但底部加强会导致薄弱层的上移,因此采取提高底盘承载力的措施的效果是有限度的,承载力系数s宜取为2 . 0 3 . 0之间。
The earthquake fortification level and the seismic performance level of structure are introduced in the thesis ; in the push - over method and quasi - static test analysis , basic concepts , development histories , the present state and their future of development ; several computing methods of structure damage and judging the grade of structure damage are simply introduced 介绍了包括地震设防水准、结构抗震性能水准等基本概念;介绍了静力弹塑性分析方法( push - over方法)和拟静力循环往复加载分析方法的概念、发展历史、现状与研究前景;并简要阐述了计算结构损伤和判断结构损伤等级的一些方法。
The cable - strut tensile structures are the self - stress equilibrium systems composed by tensional cables and struts . in this paper , the basic concept of the structures was described . the analysis methods of the structural characteristics ( statically and kinematically determinate or indeterminate ) and the geometrical stability were presented . it is indicated that the cable - strut tensile structures are in stable equilibrium with first - order infinitesimal mechanisms . the ranks of equilibrium matrix were calculated by employing the singular value decomposition , and the independent modes of inextensional mechanisms and the states of self - stress were also obtained in the same way . this paper contains some typical examples which illustrate all of the main points of the work 索杆张力结构是指由张力索和压杆组成的、具有预应力自平衡的新颖结构体系.本文详细阐述这种结构的基本概念和结构特征,讨论结构静动定体系特性和几何稳定性判定分析方法,指出索杆张力结构应具有一阶无穷小机构的几何稳定体系.文中采用奇异值分解方法计算结构平衡矩阵的秩,并计算独立机构位移模态和自应力模态.最后,对几种典型的索杆张力结构进行了算例分析
The dynamic design of the foundation of the specific 12 , 000kw steam turbine - generator set is carried out . the style of the foundation is confirmed as framed foundation . according to the model of foundation dynamic responses are calculated by large - scale analysis software , sap90 , finally , multiple designs of the foundation are compared to gain some useful conclusions 包括确定该基础的结构型式,建立基础的计算模型,利用有限元分析软件sap90对其进行固有特性和动力响应计算,并对计算结构进行分析后又进行了多方案的比较,从中得出?些有意义的结论。