Deck Flexibility Identification of Bridges through a Submode Shape Combination Screening Method without a Reference Point

To achieve a high-efficiency impact test for deck flexibility identification of bridges, a reference-free substructuring test strategy with a two-stage integration method is proposed, which can be adopted to integrate the isolated parameters extracted from the measured data of each substructure divided from the entire bridge deck. As full-structural testing is fragmented into several small-scale independent substructuring tests without overlapping transitional areas, testing becomes more flexible, and experimental costs are greatly reduced while obtaining the same flexibility identification results as traditional full structural testing. Three crucial steps are addressed in this study. In the first phase, the combined deterministic-stochastic subspace identification algorithm is adopted in order to extract the modal parameters of each substructure. Subsequently, the stiffness matrix weighted orthogonality of the mode shapes is employed as the index of the parameter integration to preliminarily screen the submode shape combinations. Finally, the mode surface polynomial degree index is constructed to further screen the correct combination for the entire structural flexibility integration. Two simulation examples and an experimental example are finally considered to verify both the feasibility and the effectiveness of the proposed method.