A novel extraction method for the actual influence line of bridge structures

Abstract

This paper presents a novel numerical method for accurately extracting bridge influence line (IL) from dynamic responses of general bridge structures. In this method, the IL is approximated by a multi-segment basis function, and a normalized vehicle-induced bridge response is employed as initial IL. Subsequently, an iterative fitting calculation method is proposed to eliminate fluctuation interference in the initial IL curve such that highly accurate actual bridge IL with quasi-static characteristics can be extracted. The feasibility and accuracy of the proposed IL extraction approach for bridges are validated through numerical and experimental studies. Based on which, a parametric study is conducted to identify key parameters affecting the deflection IL extraction performance. The results show that the proposed method can extract the actual bridge IL accurately and efficiently when the segment length is in the range 1/32–1/16 of the bridge span. Compared with conventional methods, the proposed method can extract the actual IL under more flexible testing conditions. Hence, the presented numerical approach is promising for IL-based bridge structure applications.