双层混凝土箱梁设计及抗弯承载性能分析

Design of Double-layer Concrete Box Girder and Analysis of Flexural Bearing Capacity

双层混凝土箱梁通过取消横隔板,创造性地同时利用顶、底板作为桥面系来实现双层交通,可以充分发挥主体结构的能力。为研究双层混凝土箱梁的抗弯承载性能,根据其结构特点设计了双层混凝土箱梁模型,采用数值模拟方法对箱梁在跨中四点弯曲集中荷载作用下的受弯过程进行非线性分析,研究结构的破坏模式、荷载-挠度曲线、关键截面上的混凝土及纵筋应力变化等。研究结果表明:双层混凝土箱梁的破坏模式为弯曲破坏,其受弯破坏过程可以分为弹性阶段、弹塑性阶段、屈服破坏阶段。在跨中荷载作用下,箱梁顶板混凝土呈现出较为明显的剪力滞效应。跨中截面中腹板混凝土纵向应变沿梁高的分布基本呈线性,随着荷载的增加,截面中性轴有向上偏移的趋势。

Double layer concrete box girders can fully utilize the capacity of the main structure by eliminating diaphragms and creatively utilizing both the top and bottom plates as bridge deck systems to achieve double layer traffic.In order to study the flexural bearing capacity of double-layer concrete box girder,a double-layer concrete box girder model was designed according to its structural characteristics.The bending process of the box girder under the concentrated load of four-point bending in the midspan was analyzed by using the numerical simulation method.The failure mode,load-deflection curve,stress change of concrete and longitudinal reinforcement on key sections of the structure were obtained.The results show that the failure mode of double-layer concrete box girder is bending failure,and its bending failure process can be divided into the three phases,i.e.,elastic,elastic-plastic and yield destruction phases.Under the action of mid-span load,the concrete of box girder roof presents shear lag effect obviously.The longitudinal strain distribution of the web concrete in the midspan section is basically linear along the beam height.With the increase of load,the neutral axis of the section tends to shift upward.