冷弯薄壁型钢楼板的耐火性能是决定其作为装配式结构能否推广的重要因素，目前可供借鉴的足尺火灾试验数量有限，且大部分数值模拟局限于用二维传热模型开展温度场分析，或基于简化的线性温度分布开展三维模型的热–力耦合分析。由于冷弯薄壁型钢楼板构造的复杂性，利用二维传热模型以及简化线性温度分布假定开展的热–力耦合分析，由于未考虑三维结构在受火时真实的非线性传热机制，其所反映的结构抗火性能与真实情况可能存在显著差异。为更准确地描述这类结构的耐火性能，针对由冷弯薄壁型钢骨架、结构胶合板和石膏板、岩棉等材料组成的楼板体系建立了三维传热模型，按照ISO-834标准升温环境模拟火灾情境，进行非线性传热过程和热–力耦合的分析，描述了三维非线性传热机制和具有热–力耦合特征的结构行为；提出了更为准确的接触行为建模方法，以反映自攻螺钉、板材、轻钢构件之间接触传力关系和变形协调特征。在与两组足尺楼板体系火灾试验数据对比的基础上，给出了由数值模拟得到的结构行为机理解释。研究表明：提出的三维传热和三维热–力耦合分析数值模型能准确反映火灾条件下结构的力学行为，模拟的结构非线性温度分布特征、托梁的变形演化机制以及最终破坏形态与试验结果吻合较好。

Cold-formed light gauge steel framing (LSF) structure is a new type of fabricated steel structure. Fire resisting performance of LSF structure is the key factor for promoting related practical application. However, for the LSF floor as one of the main load–bearing systems in LSF structures, the available fire testing data are limited. Most of the published numerical investigations of LSF floors are carried out by using two-dimensional heat transfer analysis to study the temperature rise and distribution, or simplified linear temperature distributions. The difference between the analysis results of two-dimension and three-dimension structural members could accumulate and evolve into the essential discrepancy in force transfer when the structural scale is large and the system is complex. To determine the mechanism of the fire resistance, the model describing a floor system consists of LSF, structural plywood, and fire-resistant panel such as gypsum board or rock wool was built up in this article. According to the ISO-834 standard, the nonlinear heat process and coupled thermo-mechanical analyses were carried out. Hence, the influence of the three-dimensional thermal field and the coupling mechanical behaviors were demonstrated. In addition, a simplified modeling approach was presented to accurately describe the contact relationship, force transfer, and the deformation coordination between self-tapping screws, structural plates, and light steel members. After comparing with two sets of fire testing data for the full-scale floor slab systems, the mechanism drawn from the numerical simulation above mentioned was verified. In general, this model based on three-dimensional heat conduction and thermal-mechanical coupling can effectively describe the LSF spatial mechanical behavior under fire conditions. The results about nonlinear temperature distribution, the deformation evolution of the joists, and the final destruction mode are consistent with those of fire testing. The proposed modeling strategy can be utilized to predict the fire resistance of LSF floor systems and evaluate the effective factors on structural high-temperature behaviors via parametric analysis.

TU392.1

国家自然科学基金（51778537、51878578）；国家重点研发计划项目（2016YFC0802205、2019YFD1101001）；四川省科技计划（2019YFS0064）