Fire-resistance analysis of unbonded post-tensioned concrete simply-supported sabs

Abstract

预应力混凝土板因具备自重轻、跨度大等特点,广泛应用于建筑结构和桥梁结构中.但是,当这种结构受到火灾荷载作用时,其承载能力就会大幅下降.在高温下,混凝土和预应力筋的力学性能都会劣化,进而造成板的大挠度变形甚至破坏.本文对后张无粘结简支预应力板建立了数值分析模型,其中混凝土和预应力筋采用实体单元模拟,受力筋和分布钢筋采用桁架单元模拟.模型中材料的力学特性和热工特性参数取自文献[15].采用文献中的试验结果验证了该数值模型的可靠性,并进一步研究了混凝土受热膨胀系数、板的不同区域受火和不同的火灾场景等因素对火灾荷载作用下后张无粘结预应力混凝土简支板的挠度以及预应力的影响,得出了初步结论. Post-tensioned concrete slabs have been used in building and bridge structures throughout the world for several decades for the advantages of increased structural spans and reduced self-weight.However, its deformation and load carrying capacity will deteriorate once they are subjected to fire.Despite various experimental and theoretical investigations,there is relatively little work on fire-resistance parametric analyses for this kind of structures.This paper describes a detailed finite element analysis of unbonded post-tensioned simply-supported concrete slabs unde fire using the package ABAQUS. All the structural components are modelled by solid elements with the exception of the reinforing steel which is modelled by truss elements. The thermal and mechanical properties of the components of the model are taken from Eurocode EN 1992-1-2. The model is verified by comparing the numerical results of temperature field and deformation with available experimental results from the literature. The parameters of concrete expansion coefficient, different areas of slab subjected to fire, and different fire scenarios are taken into account to determine the deflection of slabs and tensile force of prestressing strands. The conclusions obtained can be referred to understand the behaviors of slabs under fire and conduct fire-resistant design.