Stress redistribution of simply supported reinforced concrete beams under fire conditions

标准火灾下钢筋混凝土简支梁应力重分布研究（英文）

This study presents experimental and numerical investigations of simply supported steel reinforced concrete(RC)beams under fire.The temperature field of cross sections,the vertical deflection at mid-span,and specifically the axial expansion displacement at beam-ends were measured during the fire tests.A novel finite element(FE)model of a RC beam under fire was developed,in which the water loss in the heat transfer analysis and the concrete transient strain in the mechanical analysis were considered.Based on the validated FE model proposed in this study,parametric studies were conducted to investigate the effects of the beam type,the protective layer thickness,and the load ratio on the thermal and mechanical behavior of simply supported RC beams.It was found that greater fire resistance and fire performance of girder beams in comparison to secondary beams contributed to the non-structural reinforcements,which effectively compensated for the reduced tensile capacities of structural reinforcements because of the degradation of the material properties.In addition,the history of normal stress distributions of concrete under fire can be divided into three phases:expansion,stress redistribution and plateau phases.

本文对钢筋混凝土简支梁的抗火性能进行试验研究及数值分析。在火灾试验中,对梁截面温度分布、跨中挠度和轴向膨胀进行测试。建立考虑水蒸气转移对截面温度分布和混凝土瞬态热应变对结构受力性能影响的钢筋混凝土梁抗火分析模型。利用经试验验证的上述有限元模型,对梁的类型、保护层厚度和梁荷载比三个主要影响参数进行分析,分析结果表明:主梁的耐火性能及耐火极限优于次梁的主要原因是主梁的构造钢筋可以有效弥补因高温引起的纵筋承载能力的退化。最后,对火灾全过程中混凝土应力重分布规律进行划分并阐述。