不等高双薄壁墩结构参数对连续刚构桥力学行为影响分析

Analysis of Influence of Structural Parameters of Unequal Height Double Thin-Walled Piers on Mechanical Behavior of Continuous Rigid Frame Bridge

对于因地形和地貌原因而使双薄壁墩连续刚构桥相邻桥墩高度相差较大的情况,设计常采用不等高双薄壁墩。相比常规双薄壁墩,不等高双薄壁墩结构设计及优化可供借鉴和参考的成果不多。以某不等高、不等厚双薄壁墩预应力混凝土连续刚构桥为工程依托,基于有限元数值分析方法,改变低墩壁厚和墩间距,针对结构恒载作用、最大悬臂状态稳定及结构自振,采用单因素分析方法研究薄壁墩结构参数对连续刚构桥结构力学行为影响。结果表明:恒载作用下,低墩壁厚对主梁根部弯矩影响很小,对跨中弯矩影响相对较大;增大双肢间距可明显降低主跨跨中、根部弯矩。低墩稳定安全系数对壁厚更敏感;墩参数变化不改变失稳模态。随着低墩壁厚和间距增加,结构自振频率增大,壁厚、双肢间距影响结构一阶振动模态,且壁厚对一阶自振影响最显著。分析结论可供不等高双薄壁墩连续刚构桥结构设计和优化参考。

When the height difference between adjacent piers of a continuous rigid frame bridge with double thin-walled piers is significant due to terrain and geomorphic reasons,unequal height double thin-walled piers are often used in the design.Compared with conventional double thin-walled piers,there are few experiences and conclusions available for reference in the design and optimization of unequal height double thin-walled piers.In order to clarify the influence of structural parameters of unequal height and double thin-walled piers on the mechanical behavior of continuous rigid frame bridges,a prestressed concrete continuous rigid frame bridge with unequal height and thickness of double thin-walled piers is taken as the background.By changing the wall thickness and spacing of low piers,and adopting single factor analysis method,the finite element numerical analysis method is used to analyze the influence of pier structural parameters on the mechanical behavior of continuous rigid frame bridge structure in view of the dead load effect of the structure,the stability of the maximum cantilever state and the natural vibration of the structure.The results show that under the action of dead load,the wall thickness of the low pier has little influence on the bending moment at the root of the main beam but has a relatively large influence on the bending moment at the middle of each span.Increasing the distance between the two legs can significantly reduce the bending moment at the middle and root of the main span.The stability safety factor of low pier is more sensitive to the wall thickness.The unstable mode is not affected by the pier parameters.As the wall thickness and spacing of low piers increase,the natural frequency of the structure increases.The wall thickness and spacing between two legs affect the first-order vibration mode of the structure,with wall thickness having the most significant impact on the first-order natural vibration.The research conclusions of this article can provide a reference for the structural design and optimization of continuous rigid frame bridges with unequal height double thin-walled piers.