RC刚架拱桥的板桁组合加固及动力特性

钢筋混凝土（RC）刚架拱桥常见的加固方法大多属于局部加强而非整体改造，因此对于改善结构受力性能的作用极其有限，难以满足我国现阶段公路交通荷载日益增大的需求。针对以上问题，文中首先提出了一种新型加固方法——板桁组合加固法，该加固方法在主梁两侧架设钢桁架，通过植筋、焊接、铺设钢筋网和浇筑混凝土等措施使钢桁架与主梁牢固连接，形成板桁组合结构，从而使结构受力从主梁受力体系转变成板桁组合受力体系，实现对结构受力的优化；然后，利用该方法对某刚架拱桥进行加固改造，通过有限元仿真模拟与桥梁动载试验，对该新型加固方法的有效性和实用性进行验证。结果表明：加固后结构自振频率有效提高；竖向刚度和承载力显著增大；结构一阶面内竖弯频率理论值较加固前提高80.5%，公路-I级荷载作用下加固后结构下挠值较加固前减小56.8%，混凝土构件应力水平较加固前减小10.9%～69.8%；该加固方法对结构的动力特性具有改善作用，加固后结构的竖向振动效应小于加固前且实测冲击系数远小于现行规范值，结构动力性能良好。

Dynamic Characteristics of RC Rigid Frame Arch Bridge Strengthened by Plate-Truss Combination

The common strengthening methods of reinforced concrete (RC) rigid frame arch bridges mostly belong to local strengthening rather than overall reconstruction. Therefore, the improvement of structural mechanical properties is extremely limited, making it difficult to meet the increasing demands of highway traffic loads in China’s current stage. In view of the above problems, this paper firstly proposed a new strengthening method, the Method of Plate-truss Combination Strengthening. This strengthening method involves erecting steel trusses on both sides of the main beam, and uses measures such as planting rebars, welding, laying steel mesh, and pouring concrete to firmly connect the steel trusses with the main beam, forming a composite structure of a plate and truss. This transforms the structural load-bearing system from the main beam to the plate-truss composite system, achieving optimization of the structural load-bearing. Then, the above method was used to reinforce a rigid frame arch bridge. Through finite element simulation and bridge dynamic load test, the effectiveness and practicability of the new strengthening method were verified. The results show that after strengthening, the natural frequency of the structure is effectively improved, and the vertical stiffness, the bearing capacity is significantly increased. The theoretical value of vertical bending frequency in the first-order of the structure is increased by 80.5% compared to before reinforcement, and the deflection value of the structure under Highway Class-I load is reduced by 56.8% after reinforcement compared to before. The stress level of the concrete components is reduced by 10.9% to 69.8% compared to before reinforcement. The strengthening method can improve the dynamic characteristics of the structure. The vertical vibration effect of the structure after reinforcement is less than that before reinforcement. The measured impact coefficient is much smaller than the current normative value, and the dynamic performance of the structure is good.