This study investigates the structural response of a partially restrained, partially composite steel floor beam to a realistic or “natural” fire, which includes a rapid ramp-up to peak intensity followed by a decay phase to burnout. Thermo-structural finite element models are validated against a pair of experiments that were performed on the same unprotected specimen, which remained in place and undisturbed following the first test for 8 years until the second test. The tested specimen showed minimal damage after having been subjected to two natural fire curves and provides a novel validation opportunity for predicting the residual post-fire state of these assemblies. The validated models are then used to evaluate the prototype assembly (with and without fire protection) for its resistance to the ASTM E119 standard fire curve as well as its robustness to several natural fires with varying intensity and duration. Progressive levels of structural damage based on peak and residual response to natural fire exposure are proposed as a means to quantitatively and qualitatively evaluate the effectiveness of various fire protection strategies. These damage levels can also be used as the initial condition for determining the resilience of composite floor systems to fire (i.e. to evaluate the time and cost of recovery and repair based on the fire-induced loss of functionality). To complement this resilience-based approach, a standard fire resistance rating would essentially represent a collapse prevention benchmark and could be used to validate performance-based structural-fire calculations if the level of superimposed loading and the times needed to reach both the thermal and deflection limit criteria were reported.

这项研究调查了部分约束，部分复合的钢地板梁对真实或“自然”火灾的结构响应，其中包括迅速增加到峰值强度，然后是衰减阶段到燃尽。热结构有限元模型是针对在同一未受保护的试样上进行的一对实验进行验证的，该试样在第一次测试8年后一直保持原位且不受干扰，直到第二次测试为止。被测样品在经历两条自然燃烧曲线后显示出最小的损坏，并为预测这些组件的剩余燃烧后状态提供了新的验证机会。然后将经过验证的模型用于评估原型组件（带或不带防火保护），以证明其对ASTM E119标准防火曲线的抵抗力以及对强度和持续时间不同的几种自然火灾的耐受性。提出了基于对自然火暴露的峰值和残余响应的渐进式结构破坏水平，作为一种定量和定性评估各种有效性的方法消防策略。这些损坏程度也可以用作确定复合地板系统着火的弹性的初始条件（即，基于着火引起的功能丧失来评估恢复和维修的时间和成本）。为了补充这种基于弹性的方法，标准耐火等级实质上代表了防塌基准，并且如果叠加载荷的水平以及达到热力和挠度所需的时间，则可以用来验证基于性能的结构火力计算。报告了极限标准。