摘要
综合考虑火灾高温下影响钢筋混凝土结构性能的参数,利用数值模拟程序分析火灾高温下钢筋混凝土矩形截面梁的温度分布,研究了保护层厚度对ISO834标准火灾升温过程中钢筋混凝土矩形截面梁极限弯矩的时变效应规律。在此基础上,建立了钢筋混凝土梁桥火灾高温安全评价模型,提供了相应的计算方法,分析了不同温度下钢筋和混凝土的弹性模量损伤度及强度损伤度,对火灾高温下不同时间钢筋混凝土梁桥安全指标实现了量化归类。结果表明:在火灾高温作用下混凝土弹性模量比其相应强度更容易损伤,损伤速率大;火灾时间和保护层厚度对钢筋混凝土梁极限弯矩和安全等级有较大影响;火灾高温超过40min后,梁的极限弯矩直线下降,100min左右,可达严重损伤;钢筋混凝土梁极限弯矩随保护层厚度的增加呈线性递增关系;提高混凝土保护层厚度,可有效提高火灾场钢筋混凝土梁的耐火极限和安全等级。
This paper is aimed at presenting our safety evaluation model for the high temperature of the reinforced concrete beam bridge experienced in a fire accident. Since a lot of influential factors are to be considered when a fire accident takes place, such as moisture and local concrete heat conductions, etc. The corresponding structures are to be subjected to the transient fire temperature influence in correspondence with the time-dependent law of ultimate moment for the beams exposed to the ISO 834 fire level. Thus, the model we have proposed is by nature a simulated one for measuring the rectangle section beam and determine the response to the thermal and mechanical load, including the eventual damage likely to be caused by the fire. We have also studied the damage of elastic modulus and the strength loss of the steel and concrete elements. As the result of our study, we have put forward a series of safety evaluation regularities of time variation for the reinforcement pieces exposed to the fire. The study results also indicate that： （1） The damage velocity for the concrete elastic modulus tends to be bigger than its own strength, as the result of being exposed to the fire; （2） The protective layer thickness is likely to be more seriously affected due to the fire resistance to the concrete beam bridge; （3） the ultimate moment for reinforcement concrete beam tends to decrease linearly after 40 min fire, with the fire resistance of the reinforced concrete beam bridge increased linearly with the increase of the protective layer thickness; Therefore, the increment of concrete protective thickness would be effective for the concrete beam to resist the fire spreading. And in turn it may help to increase the safety grade for the reinforcement concrete beam.
出处
《安全与环境学报》
CAS
CSCD
2008年第3期153-157,共5页
Journal of Safety and Environment
基金
国家交通部西部交通建设科技项目(200531881215)
关键词
桥梁工程
安全评价
钢筋混凝土梁桥
耐火极限
标准火灾
极限弯矩
bridge engineering
safety evaluation
reinforcement concrete beam
resistance of fire
standard fire
ultimate bearing moment
