基于拉压杆的独柱墩抗倾覆加固结构及设计方法研究

Study on Anti-overturning Reinforcement Structure and Design Method of Single-pillar Pier Based on Strut-and-tie

独柱墩桥梁倾覆过程的最主要表现形式是主梁刚体转动,而汽车荷载偏载产生的倾覆力矩和主梁自重产生的抗倾覆力矩分别是杠杆的动力和阻力。为提高独柱墩桥梁结构的抗倾覆稳定性,确保独柱墩桥梁在运营过程中具有足够的抗倾覆安全储备,避免主梁的横桥向倾覆,使梁体达到静止的平衡状态,抗倾覆力矩应具有足够的抵抗效应。在杠杆原理基础上,提出了基于拉压杆的独柱墩抗倾覆加固新型结构,该新型加固结构是将主梁腹板两侧与桥墩通过钢拉杆连接,当主梁有倾覆的趋势时,产生拉压杆效应,为有倾覆趋势的主梁提供了一个附加的反向力矩,以抵抗主梁的倾覆力矩,同时提高了主梁的抗倾覆能力。基于拉压杆效应的力学原理,在现行规范公式基础上建立了该类结构的抗倾覆稳定系数计算方法。该新型加固结构构造简单、受力明确、加固效果好、设计与施工方便。工程应用实例表明:该加固结构能将桥梁抗倾覆稳定系数提高1. 5倍以上,抗倾覆稳定系数大幅增加,加固效果显著;实桥监测期间未见明显位移突变导致支座脱空,左右侧梁体位移并未出现较大的反差,并且呈现一致的变化规律。监测结果也验证了该加固结构的有效性和可行性,该加固结构及其设计方法可为类似桥梁结构加固提供借鉴和参考。

The main manifestation of the overturning process of the bridge is the rigid body rotation of the main girder,and the roll moment generated by the vehicle partial load and the anti-overturning moment generated by dead weight of the main girder are the power and resistance of the lever.In order to improve the anti-overturning stability of the single-pillar pier bridge structure and ensure that the bridge has sufficient anti-overturning safety reserve in operation process,to avoid the main girder lateral overturning,and make the girder reach a static equilibrium state,the anti-overturning moment should have sufficient resistance effect.Based on the principle of leverage,a new type of anti-overturning reinforcement structure for single-pillar pier based on strut-and-tie is proposed.This new type of reinforcement structure connects both sides of the main girder web with bridge piers through steel tie rods.When the main girder tends to overturn,the strut-and-tie effect is generated,which provides an additional reverse moment for the main girder with overturning tendency to resist the overturning moment of the main girder,and improves the anti-overturning ability of the main girder is improved.Based on the mechanical principle of strut-and-tie effect,the calculation method of anti-overturning stability coefficient of this structure type is established based on the current code formula.The new reinforced structure has simple structure,clear stress,good reinforcement effect and convenient design and construction.The engineering application examples show that(1)the reinforced structure can increase the bridge anti-overturning stability factor by more than 1.5 times,the anti-overturning stability coefficient is greatly increased,and the reinforcement effect is significant;(2)during the real bridge monitoring,there is no obvious displacement mutation that caused the support to vacate,and the displacements of the of the girder at both sides have not show a large contrast,and shows a consistent change pattern.The monitoring result also verified the effectiveness and feasibility of the reinforced structure.The reinforced structure and its design method can provide a reference for the reinforcement of similar bridge structures.