Numerical analysis and field load testing of a suspension bridge with a root pile anchorage

Abstract

The Qiupu River Bridge is the first suspension bridge with the application of a novel anchorage of root pile foundation. The static behaviors of the bridge were studied in this paper. Before the bridge was opened to traffic, the statically loaded field tests of the bridge have been carried out to check its load-carrying capacity. Then, a finite element (FE) model of the bridge was developed and calibrated to the measured initial equilibrium configuration. The efficiency of the FE model has been verified by comparing the calculated results of the model to the measured ones under the live loads, which indicates that calibration of the FE model to the initial equilibrium configuration is crucial to the construction of a baseline FE model. Based on the verified FE model, the influences of anchorage displacements on the bridge loading behavior were studied. Furthermore, a simplified analytical method was proposed to analyze the mechanism of structural responses under the anchorage horizontal displacements. The comparison of analytical results with FE results revealed a good agreement. It is demonstrated that the horizontal displacement of the anchorage of suspension bridges affects the structural responses more obviously than the vertical displacement, while the pylon is sensitive to the anchorage displacement. The deflection of the bridge deck results from the pylon displacement, which is caused by the unbalanced main cable force between the main span and side span. It is reasonable to take the internal force of pylons as the controlling condition of anchorage displacements. Finally, based on the analytical method, the parametric studies reveal that increasing the sag-to-span ratio and side-to-center span ratio can reduce the displacement and internal force of pylons caused by the anchorage displacement.