中文摘要：

运用虚功原理，推导建立了高温下钢筋混凝土的梁单元模型，编制了钢筋混凝土结构高温反应的全过程分析程序，考虑了高温下结构的几何非线性效应，程序的有效性得到了其他学者试验结果的验证．利用该程序对某轴力作用下的钢筋混凝土梁进行了高温反应分析，研究结果表明：（1）进行高温下结构反应的全过程分析时，有必要考虑几何非线性的影响；（2）轴力不变时，随着梁所承担的竖向荷载的增加，梁的跨中挠度逐渐增大，同时，随着竖向荷载的增加，几何非线性效应对梁跨中挠度的影响程度差别不明显；（3）竖向荷载不变时，随着梁所承担的轴力的增加，几何非线性效应使梁的跨中挠度逐渐增大；（4）是否考虑几何非线性对梁的耐火极限计算结果影响较大．

英文摘要：

Based on the virtual work principle, a beam-element model of the reinforced concrete and a computer program for analysis of reinforced concrete frames subjected to elevated temperature are proposed, and the geometrical nonlinear behavior is considered. The reliability of the proposed program is then validated according to the test results provided by other researchers. Moreover, a reinforced concrete beam subjected to axial force is selected to make the fire response analysis via the program. The simulated results show that： （a） it is necessary to consider the geometrical nonlinear behavior during the fire response analysis ; （b） the mid-span deflection of the beam increases with the increase in vertical loads while the axial force keeps constant, and with an increase in vertical loads, the influence of geometrical nonlinear behavior on the mid-span deflection hardly changes ; （c） in the condition of a constant vertical load, the mid-span deflection of the beam gradually increases with the axial force due to the geometrical nonlinear behavior; and （d） the geometrical nonlinear behavior greatly influences the calculated results of fire resistance of the beam.