首页|碳氢火灾下钢桁-混凝土组合梁耐火试验研究

碳氢火灾下钢桁-混凝土组合梁耐火试验研究

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为研究钢桁-混凝土组合结构桥梁的耐火性能,开展了三榀简支下承式钢桁-混凝土组合模型梁的碳氢火灾试验.采集测点的时变温度,获得模型梁的温度场和传热模式;分析关键断面挠度变化规律和模型梁的破坏模式,揭示热-力耦合作用下的结构响应和破坏机理.研究结果表明:热-力耦合作用会使混凝土桥面板产生大量裂缝,并从中释放水蒸气,在裂缝较少的区域则会出现由于混凝土内部水蒸气压力过大导致的混凝土爆裂现象;混凝土板的隔火作用会使模型梁的温度场呈现出显著的分层现象,并在主桁斜杆高度方向上引起显著的温度梯度效应;横、纵梁下翼板会阻隔部分火焰,形成热辐射盲区,呈现出干扰式传热效应;模型梁的挠度历程可分为初增、缓增和急增3个阶段,当跨中挠度达到L/28后,难以持荷,可认为模型梁达到极限状态,表现为大挠度破坏;当外荷载水平降低10％、模型梁桁架高度增大25％时,分别可将耐火时间提高44.7％和33.3％.建立了经耐火试验验证的热-力-结构耦合数值分析模型,提出了针对钢桁-混凝土组合梁的四阶段损伤-破坏路径及其特征.
Experimental study on fire resistance of steel truss-concrete composite bridge girder under HC fire conditions
To investigate fire resistance of steel truss-concrete composite bridges,three sets of HC fire tests were carried out on simply supported model girders.The temperature field and heat transfer mode were obtained by collecting time-varying temperatures at measuring points.The failure mode of model girders and the structural response and failure mechanism under thermal-mechanical coupling were investigated by analyzing the deflection variation in critical sections.The test results indicate that the thermal-mechanical coupling causes numerous cracks in concrete,leading to water vapor overflowing from these cracks.In areas with fewer cracks,concrete bursting occurs due to excessive water vapor pressure inside.The fire-resistant properties of concrete lead to a distinct stratification phenomenon in the temperature field of model girders,resulting in a significant thermal gradient effect along the diagonal web member.The lower wing plate of transverse and longitudinal bracings block part of the flame and form the blind section of thermal radiation,showing an interfering heat transfer effect.The deflection course of model girders is divided into three stages,namely,initial increase stage,slow increase stage and rapid increase stage.When the mid-span deflection reaches L/28,it becomes challenging to sustain the load,and the structure can be considered to have reached its limit state with significant deflection failure.By reducing load level by 10％and increasing truss height by 25％,it is possible to enhance fire resistance time by 44.7％and 33.3％,respectively.The finite element analysis model of thermal-force-structure coupling validated by a fire resistance test was established,and a four-stage damage-destruction path and its characteristics for steel truss-concrete composite bridge girder were proposed.

steel truss-concrete composite bridge girderHC fire conditionfire resistance testnumerical simulationfire resistance

汤陈皓、张岗、李徐阳、陆泽磊、宋超杰、王世超

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长安大学公路学院,陕西西安 710064

钢桁-混凝土组合梁 碳氢火灾 耐火试验 数值模拟 耐火性能

国家自然科学基金项目国家自然科学基金项目陕西省自然科学基础研究计划资助项目陕西省创新能力支撑计划资助项目

52378476520780432022JC-232023-CX-TD-38

2024

10.14006/j.jzjgxb.2022.0902

建筑结构学报
中国建筑学会

建筑结构学报

CSTPCD北大核心
影响因子：1.546
ISSN：1000-6869
年,卷(期)：2024.45(3)
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