预应力组合网架结构抗火性能数值分析

为了考察预应力组合网架结构在火灾下的力学性能和影响因素,结合实际工程对预应力组合网架结构的抗火性能进行了数值分析.介绍了采用的破坏准则、基本假定及有限元模型,考虑了边界条件、拉索布置、涂层厚度及节点刚度对其整体抗火性能的影响.通过分析,发现预应力组合网架具有良好的抗火性能;边界法向约束条件对于结构耐火时间具有显著影响;采用预应力索从下弦杆中穿过的方案,使得拉索受到了下弦杆的保护,延缓了升温速度;为达到规范规定的耐火时间,所需的防火保护层厚度低于规范规定的要求;模型中采用刚接或铰接节点,计算得到的耐火时间基本相同.

Numerical Analysis of the Fire-Resistance of Pre-Stressed Composite Space Truss System

In order to reveal the mechanical performance and influencing factors of pre-stressed composite space truss under the fire condition,the fire resistance of pre-stressed composite space truss was studied by numerical analysis with a practical project.The destruction rules,the basic assumptions and the finite element models which are used in the analysis were introduced.The influences of the border support condition,the position of the cable,the thickness of the fire-resistant paint and the joint rigidity on the fire resistance of the pre-stressed composite space truss were considered.Numerical results showed that pre-stressed composite space truss had good performance of fire-resistance.The normal support condition greatly influenced its fire resistant perfor-mance.When the pre-stressed cable was laid through the bottom chord,the cable was protected by the tube,and then its temperature rise rate was reduced.In order to satisfy the fire-resistant time in the currently valid stan-dard,the thickness of the paint was thinner than specified thickness in the standard.The analysis results of the models using hinged nodes or rigid nodes were basically the same.