火灾高温下钢框架承载力及等效荷载分析

基于对火灾场钢结构框架梁极限抗弯、抗剪承载力和框架柱承载能力及稳定性的变化分析,提出采用等效楼面活荷载的增大来描述火灾高温对钢结构框架极限承载能力的削弱.建立火灾高温作用下钢结构框架梁极限抗剪承载力,框架柱承载能力和平面内、外稳定性以及结构等效楼面活荷载的计算表达式.通过具体算例分析火灾条件下,具有不同保护层厚度的钢框架梁、柱极限承载力以及结构等效楼面活荷载的变化规律,并将等效楼面活荷载计算方法与现有计算方法进行实例对比分析.分析结果表明:对于火灾高温作用下具有不同保护涂层厚度的钢结构框架,可根据火灾的燃烧时间和结构构件温度的变化,采用不同的等效楼面活荷载来分析火灾高温对结构受力性能的影响,简化结构的受力计算,判断其极限承载能力的变化.

Analysis of bearing capacity and equivalent load of steel frame subjected to high temperature due to fire

On the basis of analysis of the variation of limit bearing capacity on bending and shearing of steel framed beams and the bearing capacity as well as the stability of steel framed columns in the case of fire,it was suggested that the weakening of limit bearing capacity of steel structural frame due to the high temperature resulted from fire should be described as due to the increase in the equivalent floor live-load.The computational expressions of the limit bearing capacity of steel framed beams on shearing,bearing capacity and stability inside and outside the plane of loading of framed columns,and structural equivalent floor live-load were set up for the case of high temperature due to fire.The variation pattern of limit bearing capacity of steel framed beams and columns covered with protectional layers different in their thickness as well as the structural equivalent floor live-load was analyzed in the condition of fire by means of concrete computational example.The evaluation method of equivalent floor live-load was analyzed and compared to the one available by using an actual example.It was shown by the result of analysis that,as for the steel structural frames covered with protection layers different in their thickness and subjected to high temperature due to fire,the influence of fire's high temperature on the force bearing performance of the structure could be analyzed by means of employing different equivalent floor live-load according to the duration of the fire and temperature variation of the structural components,so that the evaluation of forces and judgement on the variation of limit bearing capacity were simplified.