钢框架梁抗火的非线性有限元分析-结构工程专业论文.docxVIP

摘 摘 要 耐火性能差是钢结构的一个致命缺点，钢材的强度、弹性模量等基本力学 性能指标在高温下急剧下降，一旦发生火灾钢结构就有可能发生严重的破坏甚 至过早地整体倒塌。目前国内的钢结构抗火设计主要采用基于试验的构件抗火 设计方法，这种方法很难模拟构件在整体结构中的荷载分布、大小以及端部约 束情况的影响，而通过计算来确定钢结构的抗火极限承载力，则可以更加合理 地确定钢结构的防火保护措施。因此，对基于计算的钢结构抗火设计方法进行 深入的研究具有重要的理论意义和工程实用价值。 本文基于钢结构抗火设计中存在的一些问题，完成了如下的工作。考虑静 力荷载和温度应力的影响，采用有限元法对钢框架中的工字钢梁进行了特征值 屈曲分析，判断其火灾下的失稳模态；在特征值屈曲分析的基础上，考虑材料 非线性和几何非线性，对工字钢梁作了火荷载下的非线性屈曲计算，并比较了 初始缺陷、不同约束和不同荷载水平对其抗火极限温度的影响；分析了火灾下 由于梁挠度的增长而产生的悬链力对工字钢梁抗火承载力的影响；按照传热学 的原理，对平面框架进行了热．结构耦合计算，判断了火灾下结构的薄弱环节， 并考察了受火构件与非受火构件的相互影响，更加真实地反映出结构的抗火性 能。 关键词：钢结构抗火，悬链力，工字钢梁，整体屈盐，局部屈曲，钢框架，热 ．结构耦合分析 ABSTRACTThe ABSTRACT The poor fire—resistance ability is the main weakness of steel structure m that its mechanical property such as strength and elastic modulus decrease severely in high temperature．When t fire OCCllr$，severe damage or global collapse will happen tO the steel structure，In ehina，test—based fire resistance design method is the prevailing fare resistance design method for steel structures，However,using the test-based fire resistance design method，it is hard to simulate the magnitude and distribution of loads and the end restriction conditions of the specimens in the structure．The ultimate fire resistance of the steel structure and the fire protection measures can be determined throbgh calculation·based fire resistance design method．Therefore，a thorough study of the calculation—based fire resistance design method has great theoretical sigrfiflcance and practical value． In this paper,based on the problems on the fire safety design of steel structures， the following researches have been accompfished．Considering the effects ofs诅tic load and thermal stresses，eigenvalue buckling analysis is applied to the I-section girder in the steel frames based on the finite element method，and the gkder’s buckling modes in the fire are determined；On file basis of the eigenvalue buckling analysis．considering the material nolinearities and geometical nolinearities，nolinear buckling analysis is applied to the g矾er in fire