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针对火灾下预应力混凝土T(PCT)型梁桥顶板的开裂,利用热力耦合方法分析了爆燃火灾下4片预应力混凝土T梁桥的温度场和剪力滞时程演变规律。研究结果表明:火温全程T型梁翼缘板连接部位温度值高于翼缘板根部,呈现出以腹板与顶板交合部位为中心逐渐向翼缘板边缘部位呈稀疏温度带间隔梯度过渡的“V”状分布云;火温初时,恒载作用下顶板最大压应力位于两边肋顶部,最小压应力位于两边梁外侧悬臂板端部,单片梁体顶板呈负剪力滞状态,4片梁体顶板剪力滞呈“W”状,其峰值之比接近1.0;随火温时间延增,两中肋的应力峰值点出现在半悬臂板宽度处,应力变化幅值大于两边肋与四肋同时受火的顶板应力变化幅值,顶板部分出现拉应力;随火温时间延增,各片T梁顶板处于负剪力滞状态;研究可为预应力桥梁实用抗火设计提供依据。
Aiming at the cracking of roof of prestressed concrete T (PCT) beam bridge under fire, the evolution law of temperature field and shear lag time of four prestressed concrete T beam bridges under deflagration fire was analyzed by the method of thermal coupling. The results show that the temperature of the connecting part of the T-Beam flange plate is higher than that of the flange plate at the whole temperature, showing a transitional gradient with a sparse temperature gradient at the edge of the flange plate centering on the intersection of the web and the top plate. The maximum compressive stress of the roof is located on the top of both sides of the rib under the action of constant load. The minimum compressive stress is located at the end of the cantilever plate outside the two side beams. The top of the monolithic beam body shows negative shear lag state, The shear lag of the beam body is “W” shaped and the ratio of its peak value is close to 1.0. With the increase of the temperature time, the peak stress of the two ribs appears at the width of the semi-cantilever plate, and the variation of stress is larger than that of the two ribs And four ribs at the same time by the roof stress changes in the amplitude of the roof, the roof part of the tensile stress; with the fire temperature time delay, each T-beam roof in negative shear lag state; research can provide a basis for practical fire-resistant design of prestressed bridges .