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为研究单箱双室箱梁在对称竖向荷载作用下的受力特征,基于横截面的荷载等效原理与荷载分解,分析了单箱双室箱梁对称弯曲时的局部扭转效应。基于截面的剪力流平衡和箱室受力分解,得到了局部扭转的等效荷载及应力计算式。通过与有机玻璃模型试验和有限元模拟结果的对比,验证了局部扭转效应计算式的正确性,并获得了单箱双室简支箱梁的局部扭转效应下的应力分布规律。研究表明,单箱双室箱梁在仅中腹板作用竖向荷载及两边腹板作用相等竖向荷载时,均存在纵向弯曲和局部扭转的组合变形模式。局部扭转由约束扭转、畸变和横向弯曲效应组成,在截面引起纵向应力和横向应力。局部扭转效应的理论计算结果与模型试验和板壳有限元分析结果吻合良好,表明基于截面剪力流等效的局部扭转荷载求解方法对双室箱梁是适用的;单箱双室箱梁的局部扭转效应在荷载作用点附近截面最为突出,截面上、下缘纵向应力和横向应力以中腹板为拐点呈折线分布,其应力分布和大小与荷载在横截面上作用的部位紧密关联;对算例箱梁,局部扭转效应产生的纵向应力可达初等梁弯曲应力的25%。
In order to study the force characteristics of single-box double-chamber box girder under symmetrical vertical load, the local torsional effect of single-box double-chamber box girder is analyzed based on the equivalent principle of cross-section load and load decomposition. Based on the cross-sectional shear flow balance and box-chamber force decomposition, the equivalent torsional load and stress formulas are obtained. The correctness of the calculation formula of local torsional effect was verified by comparison with the model experiment of plexiglass and the result of finite element simulation, and the stress distribution under the local torsional effect of single box double chamber simply supported box girder was obtained. The results show that the combination of longitudinal bending and local torsional deformation exists in the single box double-chamber box girder with only vertical load acting on the middle web and equal vertical load acting on both webs. Local torsion consists of restrained torsion, distortion and lateral bending effects that cause longitudinal and lateral stresses in the cross-section. The theoretical calculation results of local torsion effect are in good agreement with the results of model test and the finite element analysis of plate and shell. It shows that the method of local torsional load based on cross-section shear flow is suitable for double-chamber box girder. The local torsional effect is most prominent near the load acting point. The longitudinal stress and lateral stress at the upper and lower edges of the cross section are distributed in a meandering line with the mid-web as the inflection point. The stress distribution and size are closely related to the load acting on the cross-section. In case of box girder, the longitudinal stress produced by the local torsional effect can reach 25% of the bending stress of the primary beam.