型钢混凝土框架结构耐火性能有限元分析

为了研究型钢混凝土框架整体结构的耐火性能，为其抗火设计提供参考，采用受火楼层建立精细化有限元计算模型、非受火楼层建立梁单元计算模型的方法，建立了型钢混凝土框架整体结构的耐火性能计算模型。考虑火灾位置、荷载分布形式、柱轴压比等参数的影响，对火灾下型钢混凝土框架整体结构的变形规律、承载机制、破坏形态以及耐火极限进行参数分析。分析结果表明：火灾下框架结构出现了整体破坏和局部破坏两种典型的破坏形态，受火构件受到的约束作用对其耐火性能有较大的影响；在局部破坏形态中，由于受热膨胀，火灾下框架梁首先出现了较大的轴压力，受火框架梁处于压弯受力状态；之后，框架梁出现了悬链线效应，轴力对框架梁的受力状态有较大影响；在整体破坏形态中，根据轴压比及荷载分布形式的不同，框架出现了中柱破坏和边柱破坏两种典型破坏形态，同时，随楼层受火位置的升高，柱的轴压比减小，框架结构的耐火极限增加。

Finite element analysis of fire resistance of steel reinforced concrete frame structures

In order to study the fire resistance of a global steel reinforced concrete(SRC)-reinforced concrete(RC)frame structures and to give a guideline for the design of the SRC frame structures,a finite element(FE)model for the fire performance of SRC frame structures was established.In the FE model,the fire floor was simulated with continuum elements,while the floor at ambient temperature was simulated with beam elements.The deformation,working mechanism,failure mode and the fire resistance duration of the SRC frame structures were studied by using the FE model,where the parameters such as fire floor,load distribution and axial compression ratio of columns were considered.The analysis results show that there are two typical failure modes of frame structures under fire,i.e.,global frame failure mode and local frame failure mode,and the restraint of the heated members plays an important role in the fire resistance of the SRC frame structures.For the local frame failure mode,an axial compressive force occurs in the heated frame beams in the first stage of the fire,and then the axial compressive force changes into a tensile force.The axial force,which is induced by thermal expansion,has an important effect on the fire resistance of the heated frame beams.Catenary action arises in the later stage of the fire.For the global frame failure mode,two failure modes,i.e.,side frame column failure and middle column failure,occur depending on the load distribution and axial compression ratio of the columns.In the two global frame failure modes,the fire resistance increases with the increase of the height of the floor in fire and the decrease of the axial compression ratio of the columns.