高温下张弦梁结构力学特征解析解

MATHEMATICAL CALCULATIONS FOR THE CHARACTERISTICS OF BEAM SRTING STRUCTURE IN FIRE

在实腹钢梁或钢桁架下部张拉预应力高强钢索形成预应力张弦梁结构,然而钢索的预应力对温度变化敏感,因此火灾是危及张弦梁结构安全性的重要灾害,求解高温下结构的力学特征解析解是进一步研究其火灾安全性能的理论基础。考虑高温下钢材材性的衰减、非线性热应变以及几何形变的耦合,建立张弦梁结构高温下梁单元与索单元建立基本平衡微分方程,分别推导出在均布荷载作用下张弦梁结构在均匀温度场及非均匀温度场中,结构跨中挠度、预应力索水平张力和撑杆轴力的解析解;并且基于张弦梁结构力学特征解析解,对比分析了张弦梁结构热力耦合数值分析模型的可靠性,可为后继设计张弦梁受火试验方案及研究其受火破坏机理提供参考。

A beam string structure is formed by tensioning the prestressed high strength cable in the low part of a solid web steel beam or a steel truss. However, the prestress of the cable is sensitive to temperature change. Therefore, fire is an important disaster for the safety of a beam string structure. The analytical calculations of mechanics characteristics are a theoretical basis to further study the fire safety performance. Considering the geometric distortion with thermal stress coupling temperature distribution and the non-linear temperature-dependent material properties for a steel beam and its cable, the equilibrium differential equations of the beam and cable at high temperature are established, and formulas are developed for the calculation of mid-span deflections, the horizontal tension in the cable, and axial forces of the struts subjected to fire under linear load. Additionally based on the analytical calculations of mechanics characteristics, the reliability of the nonlinear numerical model for the fire safety performance of a beam string structure is compared. This study can provide a reference for subsequent fire -resistance tests and studying the failure mechanism of beam string structures subjected to fire.