连续宽箱梁的偏载增大系数的讨论

Discussion on Eccentric Load Enhancement Coefficient of Continuous Wide Box Girder

预应力混凝土连续宽箱梁桥在城市桥梁中广泛应用,由于其宽跨比较大,偏载作用引起的空间效应不可忽视,采用梁单元设计计算时,需引入偏载增大系数来考虑荷载放大效应。提出用实体有限元法计算宽箱梁偏载作用下偏载增大效应的方法。并结合杭州某工程实例,建立其预应力混凝土宽箱梁的实体有限元模型,在模型上施加车辆荷载,通过计算分析荷载作用下结构不同位置的应力、位移,得到偏载增大系数。并对比分析实体有限元法和其他简化偏载增大系数算法的计算结果。结果表明:实体有限元法更能真实反映结构的实际受力状态,且适用性更广;宽箱梁的偏载效应明显,采用传统的经验值是偏不安全的,有必要进行详细的分析计算。

Prestressed concrete continuous wide box girder bridge is widely used in urban bridges. Because of its large width-span ratio, eccentric load induced spatial effects cannot be ignored. When the bridge is analyzed by beam element system, the amplification coefficient of eccentric load should be used for load amplification effect. The way of calculating the enhancing effect of wide box girder under eccentric load with solid finite element method is introduced. Combining with a project example in Hangzhou, the solid finite element model of a PC concrete wide box girder is built. Through analyzing the stress and displacement at different positions of the girder under traffic load, the amplification coefficient of eccentric load is calculated, which is compared with the calculation result obtained by other simplified calculation methods. It shows that （1） the solid element method could reflect the actual stress state of the structure better, it is more applicable ; （2） the eccentric load effect of wide box girder is obvious, thus it is unsafe to use the traditional experience value for design, and the value should be calculated more accurately.