火灾下防屈曲支撑最小填充层厚度简化计算方法

Simplified Calculation Method for Minimum Infill Layer Thickness of Buckling-Restrained Braces Exposed to Fire

为防止火灾下防屈曲支撑的抗震性能降低,需确保在给定的耐火时间内,防屈曲支撑的芯材温度不高于临界温度和防屈曲支撑的弯曲刚度不低于最小需求刚度。通过增加防屈曲支撑填充层厚度,一方面可以降低火灾下支撑芯材的温度,另一方面可以增加火灾下防屈曲支撑的刚度。通过对芯材截面形状为十字形的防屈曲支撑火灾升温的有限元分析,研究了填充层厚度对支撑芯材温度和火灾下支撑刚度的影响。随着填充层厚度的增大,芯材温度降低,支撑刚度增大。根据火灾下防屈曲支撑强度和刚度均不降低的条件,给出了填充层最小厚度和防屈曲支撑套管最小尺寸的简化计算方法,并通过算例介绍了防屈曲支撑的抗火设计方法。

In order to prevent the reduction of seismic performance of buckling-restrained brace in a fire,the temperature of the core plate should be lower than the critical temperature and the bending stiffness of the brace should be not less than the required stiffness.By increasing the thickness of infill layer,the temperature of core plate is reduced and the brace bending stiffness is also increased.In this paper,the temperature elevation of a buckling-restrained brace with cross section is investigated using finite element simulation.The effects of infill layer thickness on the temperature elevation of core plate and on the bending stiffness increment are presented.With increase of infill layer thickness,the core plate temperature is reduced and the brace bending stiffness increases.Based on the assumption that the yield strength of core plate and the bending stiffness of brace do not reduce in a fire,a simplified calculation method for the minimum infill layer is proposed.An example is also presented to explain the detailed design procedure.