基于系统可靠度优化的施工成本控制

建筑项目的质量控制,时间控制,成本控制是建筑监理的三大控制目标,在保证按时完成建筑项目的前提下,使质量和成本达到均衡最优,是每个项目经理追求的目标。本文把建筑项目作为一个系统来看,在保证各个子项目的质量的前提下,根据系统优化理论用蚁群算法对整个系统的可靠度进行优化,近而求出整个项目的成本。蚁群算法是第一次应用在建筑系统可靠度优化中,通过算例分析,证实了蚁群算法在建筑系统成本控制中的可行性,有效性。     

基于可靠度的桥梁结构优化设计

围绕基于可靠度的公路桥梁结构优化设计进行探讨,阐述其设计流程,并结合某简支T梁桥工程的结构优化设计展开分析,以改善桥梁的整体品质.     

输电线路杆塔结构及基础系统可靠度的优化分配

输电线路结构系统可靠度在各子系统之间的合理分配,是输电线路结构系统可靠度研究的热点问题之一.根据某±800kV同塔双回路输电线路的工程实例,在对输电线路杆塔结构及基础可靠度进行计算分析的基础上,建立了输电线路杆塔结构、基础的成本与相应结构可靠度之间的函数关系;基于经济指标的约束条件,对输电线路杆塔结构及基础系统可靠度的...     

基于可靠度的桥梁结构优化研究

介绍了确定性设计与概率设计,进行了基于可靠度的桥梁结构优化研究,给出了基于可靠度的桥梁结构优化模型,指出只有采用以结构可靠度概率为依据的概率设计方法,才能得到真正符合客观实际的设计方案。     

基于Matlab优化工具箱的工程结构可靠度计算

将服从任意概率分布的随机变量Xi映射为标准正态随机变量Yi.从正态空间中可靠度指标β的几何意义出发,建立了求解可靠度指标β的优化模型.利用Matlab的强大优化功能求解该模型,得到可靠度指标β及验算点Y*,并讨论了该模型解的存在条件.最后给出了算例及结果比较.     

基于可靠度的结构优化方法综述

基于可靠度的结构优化是将可靠度计算与优化方法二者结合起来的一种技术,其不仅能使资源得到合理利用降低工程造价,而且还可以保证结构的安全性。介绍国内外基于可靠度的结构优化研究现状,分析其存在的主要问题和解决方法,指出未来研究的方向。     

桥梁结构体系可靠度优化分析探讨

简要介绍了桥梁结构优化设计现状和结构体系可靠度的基本理论,给出以可靠度为约束条件,以一定准则为目标函数的优化模型,从整体到局部逐级分析构件合理可靠度,再从构件到体系验算整体可靠度及目标函数的思路,对桥梁结构体系进行优化分析,为工程实践提供参考。     

基于可靠度的桥梁结构优化设计

桥梁结构设计有两大任务：一是保证可靠即安全,适用,耐久;二是追求经济合理。而基于可靠度的结构优化设计就是一个很好的方法。现以简支梁桥为例,简要介绍桥梁结构基于可靠度的优化设计方法。     

结构体系可靠度计算的一种近似方法

本文提出结构体系可靠度计算的一种新方法,这种方法的基木思想是,对多元正态函数的高维积分运算,通过随机变量的变换转化为一维或二维积分,变换后被积函数中的一些参数通过优化的方法确定。经过大量实例的计算表明,本文方法精度很高,且计算形式单一。     

基于系统可靠度的空间网格结构优化分析

以空间网格结构的杆件截面为基本变量,提出了以结构的最小重量为目标函数,把结构系统的可靠度作为约束条件,采用改进的遗传算法的空间网格优化理论,从而避免了对结构系统可靠度进行复杂的敏度分析,降低了系统可靠度约束下的结构优化的难度。通过算例表明,优化结果令人满意,且收敛性较好,表明了该方法的可行性。     

巨-子型有控结构体系的可靠度分析及其优化

采用首次超越破坏机制,定义结构层间位移为极限状态控制指标,确定了基于概率密度演化方法的巨-子型有控结构体系的抗震动力可靠度的计算方法;基于可靠度并结合"等可靠度准则"对其进行优化。编制SAP2000与MATLAB接口程序将SAP2000中的分析结果带入到MATLAB中进行概率密度演化分析。结果表明:巨-子型有控结构在弹塑性阶段依然有很好的响应控制效果;巨–子型有控结构比巨型框架结构具有更高的抗震可靠度;经过优化后MSCSS的响应控制能力及可靠度都得到了显著提高。     

Structural system reliability analysis of SWATH ships

In this paper the structural system reliability method is applied to a built SWATH ship. Firstly, a typical transverse frame in the SWATH is idealized by a one-dimensional model through a series of finite element analyses. The safety margins are automatically generated by computer and the interaction of bending moment and axial force, including buckling effect, is taken into account. The significant failure modes of the structure are identified by an extended β-unzipping method, and the system reliability index is then evaluated by Ditlevsen's bounds. It is found that the most critical section is in the haunch area, and all the critical sections included in the significant failure paths are in the haunch area.     

结构安全性等级的实用计算

本文首先简要介绍了基于结构系统可靠性的结构安全性等级划分的基本思路,进而利用泰勒展开法推导了结构安全性等级的实用计算公式,通过算例验证了该方法的可行性。此外,将本文计算方法与现行鉴定标准中基于经验的方法进行了对照比较,证明定量与定性可以很好地结合。     

悬吊结构体系优化设计及减震性能研究

对悬吊摆隔震系统组成的悬吊结构体系进行研究,建立了该体系的两自由度分析模型。根据拉格朗日方程建立了系统的运动方程,并给出了地震作用下上下部子结构位移响应均方值理论表达式。通过引入性能指数,综合考虑上下部子结构位移响应,定义了悬吊结构体系性能目标函数。以性能目标函数最小为优化目标,推导了悬吊结构体系最优设计参数理论解,并通过不同性能指数下体系参数分析验证了理论解的正确性。最后,以某两层剪切型框架结构作为工程算例,对结构体系的减震性能进行数值分析。结果表明:最优参数均随性能指数的增大而增大,最优阻尼比与质量比呈正相关关系,最优频率比与质量比呈负相关关系; 增大性能指数,上部子结构位移响应峰值减震率增大,而下部子结构位移响应峰值减震率减小; 只要性能指数取值合理,悬吊隔震体系能同时有效控制上部子结构与下部子结构地震位移响应; 性能指数为1时,结构体系上下部子结构位移响应峰值减震率分别可达67.45%和25.16%以上。     

Reliability-based optimisation design of post-tensioned concrete box girder bridges considering pitting corrosion attack

Since the mid-twentieth century, prestressed concrete (PC) bridges have been significantly developed to become the most important type of bridge in the world. However, only a few studies have dealt with the reliability-based design optimisation (RBDO) of PC bridges despite the fact that RBDO demonstrates the real behaviour of structures. Moreover, the corrosion of post-tensioned tendon in PC bridges seriously caused sudden failures which have been recorded in the world. Since then, this study presents the probabilistic model and approach to formulate and analyse the RBDO of PC box girder bridges which consider the pitting corrosion phenomenon of shear, torsion reinforcements and post-tensioned tendon. A practical example of a typical PC box girder bridge is presented and discussed. Sensitive analyses are performed to evaluate the influence of ultimate target reliability index on the optimal solution. For the simple support PC box girder bridge, the ultimate target reliability index should be in the range of β_ult: 3.5–5 in order to produce the optimal design.     

基于可靠度的结构抗震优化设计

介绍了结构抗震设计的目的与目标,并对基于概率可靠度的结构抗震设计方法进行了阐述,根据“投资—效益”准则,提出了基于功能的结构体系目标可靠度优化决策的三种模型,从而为结构抗震优化设计的进一步研究奠定了理论基础。     

用模糊分析决策理论优选中高层住宅结构体系

中高层住宅结构体系的优选是一个综合性的多目标决策问题。通过简要介绍中高层住宅常用的钢筋混凝土结构体系及其优缺点 ,给出中高层住宅结构体系优选影响因素关系图 ,并提出如何利用模糊集分析单元系统理论计算影响因素的权重分配系数和评价矩阵 ,最后以具体实例阐述优化选择中高层住宅结构体系的全过程。方法可供关注工程决策的读者参考     

主动变刚度结构体系(AVS)多模态优化控制研究

依据原有状态控制律对AVS结构体系进行结构控制时 ,会出现高频响应失效问题 ,为此本文提出基于单步状态预测的控制律。借助结构模态控制技术 ,经推演而得出具有普遍工程应用意义的多自由度AVS结构体系的多模态优化控制律。通过仿真分析 ,可以看出本文方法较好地解决了高频控制响应失效问题 ,在取得与瞬时最优控制相当控制效果的同时 ,大大缩短了在线计算时间     

Structural system reliability considerations with frame instability

An approximate method for structural system reliability analysis is presented for framed structures when instability failure modes are considered. Deterministic rigid-plastic and stability analysis techniques are reviewed. An efficient analytical procedure is combined with Monte Carlo simulation to obtain an estimate for the system reliability of structural frames when frame instability is considered. Examples are presented to illustrate the technique.     

Reliability-based design of medium mast lighting structural supports

Rural intersections and interchanges often require lighting for driver safety. Although high mast lighting supports, sometimes as tall as 50 m have been installed in many locations, it is becoming apparent that light pollution to nearby residences is an issue. As a response to this problem, the Colorado Department of Transportation is moving towards the use of medium mast lights which are typically 15–20 m in height. This article presents the results of a numerical investigation to develop reliability-based design charts as a function of several key design variables and the mean wind velocity at a site. These medium-mast structures are less than 1 m in diameter at the base and are quite flexible relative to many civil engineering structures. The limit state function is formulated in terms of fatigue life and is computed based on the moments at the base that are produced during multi-mode dynamic excitation as a result of the wind loading. Morison's equation, which provides relative force for slender bodies as a function of flow velocity, was applied within a dynamic finite element framework in order to account for the relative motion between the wind and the motion of the structure. Then, a well-known random vibrations approach was coupled with Miner's rule to estimate the fatigue life of the structural support. Reliability-based design charts for several different design variables such as wall thickness and outside diameter are presented.