超大跨径斜拉桥纵向极限风荷载作用下约束体系研究北大核心

为研究超大跨径斜拉桥在纵向极限风荷载作用下的合理约束体系,以某主跨1176 m斜拉桥为背景,采用BNLAS非线性有限元软件建立该桥整体结构模型,分析半飘浮体系、单侧纵向约束体系、两侧纵向约束体系及弹性索体系在纵向极限风荷载作用下的纵向位移和内力效应。结果表明:主梁上没有纵向约束的半飘浮体系结构,作用于梁上的纵向极限风荷载通过斜拉索全部传递到桥塔上斜拉索锚固处;主梁上增加纵向约束后,作用于主梁上的纵向极限风荷载大部分通过纵向约束直接传递给桥塔,大大降低了纵向极限风荷载在桥塔上的作用高度,有效减小了结构纵向位移和塔底面内弯矩;在桥塔处设固定支座或弹性下拉索,将主梁与塔连接,主梁上的纵向极限风荷载直接传给桥塔或桥墩,是减小超大跨径斜拉桥纵向极限风荷载作用效应的有效途径。

Study of Restraint Systems for Super-Long-Span Cable-Stayed Bridge to Resist Extreme Longitudinal Wind Load

The appropriate restraint systems for the super-long-span cable-stayed bridge to resist extreme longitudinal wind load are studied.Based on a cable-stayed bridge with a main span of 1176 m,a non-linear finite element model was established by BNLAS to analyze the longitudinal displacement and internal force effect of the semi-floating system,one-side longitudinal restraint system,two-side longitudinal restraint system and elastic cable system under the action of extreme longitudinal wind load.As per the study,for the semi-floating system where there is no longitudinal restraint on the main girder,all the extreme longitudinal wind loads acting on the main girder can be transmitted to the stay cable anchorage zones in the pylons via stay cables.When the main girder is fitted with longitudinal restraints,a large portion of the extreme longitudinal wind loads acting on main girder can be directly shifted to the pylons via the longitudinal restraints,which greatly lowers the acting height of extreme longitudinal wind loads on the pylons,thereby restricting the longitudinal displacement of the structure and the in-plane bending moment in the pylon base.But when the main girder and pylons are connected by permanent bearings and downward-tensioning elastic cables,the extreme longitudinal wind loads acting on the main girder can be directly transmitted to the pylons or piers,which is considered an effective means to mitigate the effect of extreme longitudinal wind loads on the super-long-span cable-stayed bridge.