【作者】 白音；

【导师】 石永久；

【作者基本信息】 清华大学 ， 土木工程， 2008， 博士

【摘要】 大空间钢结构以其宏伟的建筑造型、巨大开敞的内部空间等优点在我国得到了广泛的应用。由于钢材本身耐火性能较差,且造型美观等要求使得防火保护费用惊人,大空间钢结构往往不能直接按照普通钢结构的方法进行结构抗火设计。目前我国关于大空间钢结构抗火设计的研究还相当薄弱,现行规范的相关规定也少有涉及,因此,深入开展大空间钢结构火灾下的受力性能和抗火计算方法研究具有十分重要的理论意义和工程实用价值。本文结合理论分析、数值计算等多种手段,对大空间钢结构火灾下不均匀温度场分布以及典型结构类型的受力性能进行了较系统的研究,充分考虑结构的几何、材料非线性等参数影响,提出了相应的抗火计算方法。本文主要完成以下几方面工作:(1)通过与试验数据对比,确定了大空间结构数值模拟中火源模型等简化方法。系统研究了影响大空间结构内不均匀温度场分布的主要因素,并对几种温度场计算方法是否适用于大空间钢结构屋面附近空气温度场的计算进行了分析和讨论。(2)对大空间钢结构火灾升温过程中受力性能的计算方法进行了探讨,通过对比分析确定了结构钢材和高强度钢索在火灾高温下的材料属性,并以门式刚架钢结构为例,对此计算方法的有效性进行了进一步阐明。(3)提出了四角锥网架火灾下中心点位移的计算方法——修正拟夹层板法,并结合火灾下受力性能影响因素分析,得到了考虑不均匀温度场分布的临界温度计算表。在对单层网壳火灾下弹塑性承载力研究的基础上,提出了单层网壳火灾下弹塑性稳定承载力的简化计算公式。(4)推导了索桁架结构和鞍形索网结构火灾下竖向位移和预应力变化的计算公式。利用有限元计算分析方法对张弦梁结构火灾下受力特点进行了研究。给出了单层索网玻璃幕墙临界温度的取值方法,计算得到了适用于单层索网玻璃幕墙结构不同跨度、网格尺寸、钢索直径下的临界温度计算表。更多还原

【Abstract】 Large-space steel structures have been widely used in China by its virtue of magnificent shape and enormous interious space etc. However, the steel material is weak in fire resisting, and the aesthetic demand always leads to numerous cost. Moreover, large-space steel structure could not adopt the fire-resistance design method for common steel structures. The research on its fire-resistant behavior and calculation method is still inadequate, in addition, the relevant provisions covered in current code has little involved. Therefore, it is of vital importance in theory and engineering practice to further understand the fire-resistance performance and calculation methods of large-space steel structures. Theoretical analysis and numerical simulation have been carried out hereby to investigate the temperature distribution and structural behavior under fire conditions. The geometric and material nonlinear properties are extensively considered. Practical fire-resistant calculation methods for several types of large-space steel structures have also been proposed in this paper. The main research work covered in this paper includes:(1) The simplified method of establishing fire model in large-space structure numerial simulation is given in terms of comparisons with experimental results. The main influencing factors of non-uniform temperature distribution are systematically analyzed. Whether several calculation methods can be applied for calculations of air temperautre around roof has also been studied.(2) The calculation methods for large-space steel structures’performances under fire conditions have been discussed. Material properties of structural steel and high-strength steel cables enduring high temperature are determined by contrasting analysis. The validity of this method has been extensively explained by studying structural performances of gable frames considering fire influences.(3) The modified equivalent sandwich plate method calculation method for calculating vertical displacement of quadrangular pyramid grid structures under fire conditions is given. Based on studying influcnce factors, critical temperature tables are given taking account of non-uniform temperature distribution. The simplified calculation formula for single-layer reticulated domes including temperature rise effects is obtained by researches on their elasto-plasticity bearing capacities.(4) The calculation formulae for vertical displacement and prestressed force variation of cable truss and cable nets are deduced in theory. Fire-resistance characteristics are obtained of beam string structure relying on finite element analysis. The critical temperatures determining principles for monolayer cable net of glass facades have been proposed. The critical temprature tables are obtained applicable to different spans, grid dimentions and cable diameters of monolayer cable net.更多还原