高强轻集料混凝土连续刚构桥应力分析

Stress Analysis of a Continuous Rigid-frame Bridge with High Strength Light-weight Concrete

基于高强轻集料混凝土连续刚构桥的结构与设计特点,考虑施工阶段累积效应和混凝土的收缩、蠕变效应,采用有限元理论对成桥后不同荷载组合作用下的箱梁腹板主应力进行了计算分析,得出高强轻集料砼在桥梁上的局部应用有利于抑制箱梁腹板斜裂缝的结论:(1)恒载作用下,各关键截面计算点均有σ′1<σ1,高强轻集料混凝土在连续刚构桥上部结构的使用,降低了主跨3/8截面腹板上端和质心高度处的主拉应力;其他各选取计算点处,普遍不同程度地加大了主压应力储备;(2)考虑偏载和温度作用的正常使用极限状态短期荷载组合下,轻砼桥腹板σ′1满足现行公路桥规要求,且均比普砼桥第一主应力降低;(3)上述荷载组合下,左边跨现浇段中间截面第一主应力受高强轻集料混凝土影响不大;左边跨现浇段外和主跨的各关键截面,轻砼桥不同高度计算点σ′1较普砼桥明显减小,且沿同一截面竖向,自腹板上端、质心到下端,减小幅度依次变小;沿桥轴线方向,愈接近主1#墩,σ′1减小得越多,最大减小值为0.54MPa.

According to the design and structure characteristic of a prestressed high strength light-weight concrete continuous rigid-frame bridge, principal stress of the abdomen board about the bridge are calculated and analyzed with FEM theory, with considering constructing cumulative effect , shrink and creep effect of the concrete. Conclusions are drawn as follows. （1）σ1〈σ1 comes into existence at each reckon point on key sections with effect of deadweight, that means principal stress of upper and cen tric abdomen at 3/8 section of main stride is depressed with application of high strength light-weight concrete on super structure of the continuous rigid-frame, and principal compress stresses at other points are enlarged with different degree; （2） With considering eccentric loading and temperature grads effects, under short term load combination of serviceability limited state,σ1 on abdomen of light-weight concrete bridge satisfied roadway and bridge criterion, which are smaller than those of common concrete bridge; （3） With considering and temperature grads effects, under short term load combination of serviceability limited state, first principal stress at middle section of left Cast-in-situ concrete stride is influenced lightly by high strength light-weight concrete; at other sections, σ1 of light-weight concrete bridge minish obviously compared to common concrete bridge, and depressing extent lessening take turns from upper, centric to board abdomen at a same section vertically; and at longitude, σ1 minish more near 1 # pier, of which the most depressing value is 0.54 MPa.