Damage Identification and Safety Threshold During the Construction and Operation Phases of Cast-in-Place Continuous Rigid Frame Bridges

This paper presents an analysis of the mechanical characteristics of bridge structures during both construction and operation phases, with a focus on stress distribution patterns and the impact of vehicle loads on structural safety. The monitoring during the construction phase indicates that the compressive stress of the main beam segments is mainly controlled by prestress, and the maximum compressive stress meets the specification requirements; the maximum tensile stress of the main beam occurs in the stage when the tension reinforcement of the top pier is under stress, and the tensile stress value is within the allowable range of the specification. Under the negative bending moment of the pier top, the tensile stress at the upper edge reaches the peak simultaneously with the pre-pressurization stress. In contrast, the tensile stress at the mid-span joint transfers to the lower edge, and the corresponding bending moment significantly decreases. Based on the maximum tensile stress theory, when the stress of the structure caused by the earthquake wave reaches the ultimate tensile strength of the concrete, it is prone to cause structural damage. Therefore, it is necessary to limit the vehicle weight and driving speed to reduce the vibration impact. According to the “Regulations on the Management of Over-limit Transport Vehicles on Highways” issued by the Ministry of Transport (the total designed load shall not exceed 55 tons), after calculation, it is known that the maximum allowable driving speed of a 60-ton vehicle is 81.4 km per hour, which exceeds the safety limit of the specification. The research shows that in actual operation, the driving speed needs to be dynamically controlled according to the vehicle weight to ensure the long-term safety and durability of the bridge structure.