大空间建筑火灾中网架结构的失效机理研究

Grid structures would come into local buckling and succeed to global collapse exposed to large space fires. Structural failure can damage to property and life. At present, the research of grid structural fire-resistance focuses on single member exposed to a standard fire, and takes no account of the effect of axial restraint among adjoining members caused by structural conjunction exposed to a non-uniform temperature field. There is a little achievement of the behaviour and failure mechanism of global structures in fire. All over the world, there is no test of the grid structure model exposed to fire yet. This project focuses on the fire-resistant of axially compressed restraint members after buckling, and the loading-bearing capacity mechanism of global structures subjected to local buckling in large space fires. The technology to track the limited fire bearing capacity of grid structures would be developed. The theory derived from the research mention above can be checked by the test of six specimens with the axially compressing restraint member and a single global grid structure fire test. Based on the theoretical and experimental studies, the track technology derived from nonlinear finit element theory would be developed, and indicate the ultimate fire loading-bearing mechanical and the failure criteria of space structure exposed to fire .The theory of nonlinear finit element applied to analyse the global structure subjected to fire would be integrited. Based on the idea of performance of structural fire-resistance, these results which come out of this project can be referenced by the chinese technical code for fire safety of steel structure in buildings.

大空间建筑火灾对网架结构会造成局部杆件破坏乃至整体结构的倒塌，引起较大的经济损失和人员伤亡。目前国内外对网架结构抗火性能研究主要是针对独立杆件抗火性能的分析，未考虑在大空间建筑火灾非均匀升温条件下，由于结构连续性导致的杆件间相互约束效应对构件抗火性能的影响，网架整体结构的抗火性能及失效机理也鲜有系统的理论分析，网架模型受火试验在国内外还是空白。本项目将研究火灾下网架结构中轴向约束压杆屈曲后的承载性能，以及构件屈曲后剩余承载力对网架整体结构抗火性能的贡献，建立网架结构受火反应全过程追踪方法；并通过6个轴向约束单杆试件和一个整体网架的受火试验对理论分析进行验证。通过本项目试验和理论研究，可揭示网架结构受火失效机理，丰富基于非线性有限元方法的火灾下网架整体结构力学反应分析理论，凝练出基于结构抗火性能化设计思想的网架结构受火失效判别准则，为我国建筑钢结构抗火设计规范相关条款的编制提供理论依据。

国家自然科学基金面上项目“大空间建筑火灾中网架结构的失效机理的研究”历经四年的研究，在局部火灾下网架结构的轴向约束杆件屈曲后承载性能、结构局部屈曲后承载性能、受火失效判别准则以及杆件和结构模型的受火试验等方面取得了一系列原创性的成果。该项目对基于结构连续性的网架结构受火承载性能这一关键科学问题上实现了理论突破。. 该项目的理论和试验研究表明，局部火灾下，由于温度场的非均匀性，网架结构中低温部分的杆件对高温部分杆件的热膨胀有约束作用，这种约束作用使受约束杆件高温下屈曲后仍具有一定的承载力。基于结构的连续性，在网架结构受火反应全过程分析中，应考虑杆件屈曲后承载力对网架结构抗火性能的贡献。基于结构性能化设计思想及结构连续性倒塌特征提出的网架结构受火失效两阶段判别准则，显著提高了网架结构抗火设计的科学性、经济性和安全性。