Evaluation of bearing capacity of single-span suspension bridge under load Test

Abstract

Suspension bridge is the main bridge type of modern long-span bridge, which has the characteristics of large span capacity, low material consumption and small dead weight. As the structure of suspension bridge is complex, it is difficult to evaluate its performance and bearing capacity accurately. Under the Shangri-La's Shangjiang Grand Bridge project, based on load tests, including static load test and dynamic load test, in order to identify whether the suspension bridge has the original designed working performance and bearing capacity, thereby provide guidance for the repair and reinforcement of the bridge opinion. Through static load tests, certain control sections are selected for the main bridge and approach bridge respectively, and the strain and deflection of each control section of the structure under normal and eccentric load conditions, the maximum horizontal displacement of the top of the tower in the longitudinal direction of the bridge, and the cable of the suspender are tested. At the same time, the impact coefficient is tested based on the dynamic response test, and the vibration mode, natural frequency, and damping ratio of the suspension bridge are obtained by the environmental random pulsation method. Finally, the measured results are compared with the theoretical analysis results. The results show that the strain and deflection calibration coefficients of the bridge under the static load test are both less than 1, which meets the requirements of the specification, indicating that the overall rigidity of the bridge span structure tested is good under the test load; under dynamic load, when there is an obstacle, the driving speed reaches 5 km/h, the impact coefficient reaches the maximum value of 0.318. In the dynamic characteristic test, the measured natural frequency and damping ratio are within the normal range. The load test results of Shangjiang Grand Bridge show that load test is a feasible method to evaluate the bearing capacity of single-span suspension bridge.