Deflection Field Identification of Bridges under Goal Load Based on Mode Expansion Method with Sparse Test Points

Abstract

A mode expansion method combined with a sparse point impact test strategy that establishes the relationship between the sparse flexibility matrix and the static response field of a bridge under a distributed load is proposed to efficiently identify the deflection field of a bridge under a goal load. The traditional full bridge test is converted into a dynamic test with a small number of points, which is more flexible and significantly reduces the cost of field testing while producing the same test results as the full bridge test. The proposed method is divided into three key steps. First, a mode weighted superposition model of the bridge deflection field is established, and the key modes are determined based on the modal change pattern after structural degradation. Then, the test points are optimized with the minimum number of points and the highest accuracy of generalized mode coordinate identification. Finally, an impact test is carried out on the optimized sparse test points to identify the corresponding modal flexibility, and the deflection field is reconstructed through the virtual loading method. A numerical example and a field test example are used to validate the proposed method.