大跨径预应力混凝土箱梁桥底板破坏数值分析

Numerical Analysis of Failure Mechanism of Bottom Slabs in Long-span Pre-stressed Concrete Box Girder Bridges

为减小大跨径预应力混凝土桥梁变形、控制裂缝发生,设计中常在变高度连续箱梁中跨曲线底板内施加足够的纵向预加应力.这种情况下,箱梁底板将处于高开孔率、高应力状态,在近几年预应力混凝土箱形连续梁(刚构)桥施工中,经常出现箱梁底板在合龙束张拉过程中发生沿底板孔道上下层混凝土整体破坏的工程事故.文中对某典型破坏事故进行考虑材料非线性的箱梁底板破坏机理精细化数值分析,重现了破坏全过程,并根据箱梁底板在施工过程中所处状态和受力特点,分析了底板裂缝出现的机理、破坏路径以及底板不同类型普通钢筋的作用机理.

To control cracks and large deflection in long-span concrete bridges,sufficient large-tonnage pre-stressing forces are usually applied in curved bottom slabs.In this case,curved bottom slabs in box girders are under state of high stress and duct opening ratio.Consequently,more serious accidents like concrete near pre-stressing ducts completely damaged and bursts into two parts during the process of closure in main span happen frequently in recent years.In the paper,the whole process of typical burst failure of curved bottom slab in a pre-stressed concrete bridge is reappeared by using facilitated numerical computation analysis in consideration of nonlinear characteristic of materials.The mechanism of crack arises,damage course and actions of different types of reinforcements in bottom slab is quantitatively studied during the construction process.