Simplified Method for Predicting the Lateral-Vertical Deflection of Steel-Box Girders with Large Cantilevers in a Cable-Stayed Bridge

The steel-box girder with large cantilevers (named here as a cantilever steel-box girder), an innovative girder of a cable-stayed bridge, offers a unique solution by accommodating both highway and railway on the same deck. The width of the innovative girder is large, with the cantilever part constituting a significant portion of the entire cross section. The lateral-vertical deflection resulting from this large cantilever could not be ignored. Predicting the lateral-vertical deflection of the girder is crucial in ensuring the serviceability requirement during the operation. To address this issue, this study conducted a 1∶4.5 scale model test of the cantilever steel-box girder. The lateral-vertical deflection of the girder under the action of the vehicle and train load was investigated based on the model test. Furthermore, based on the lateral-vertical deflection patterns of the girder obtained by the model test, a simplified analysis model was developed to analyze the lateral-vertical deflection of the cantilever steel-box girder. The rationality of the simplified analysis model was validated by comparing it with the results of the model test. Moreover, the calculation technique for assessing the lateral-vertical deflection was derived based on the simplified analysis model. The calculation technique was categorized into three different situations in terms of the different positions of the live load. Finally, a parametric study was performed to understand the impact of the structural parameters on the lateral-vertical deflection of the girder using the calculation technique. The findings of this study could serve as a reference in the design of cantilever steel-box girders for cable-stayed bridges.