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

Abstract

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.