Prestress force and moving force identification in prestressed concrete bridges via Lagrangian polynomial-based load shape function approach

Precise determination of prestress force in prestressed concrete bridges (PCBs) is essential for estimating the bridge’s load-carrying capacity to ensure the safety of the bridge and its users. Similarly, identifying moving forces is equally important for determining the outcome of overloading traffic and risk assessment of the PCBs. The implementation of prestress force and moving force identification in real-world PCBs using existing methods continues to face challenges. These include errors arising from the incorporation of practical uncertainties, requirement for substantial computational effort, and the need for many sensors. This paper introduces a time-domain inverse force identification method for prestress force and moving force, utilizing limited sensors to address these challenges. It relies exclusively on displacement responses for input, requiring the measurement (translational and rotational displacements) from three locations. A novel approach employing a Lagrangian polynomial-based Hermitian interpolation function is proposed to construct the load shape function from a limited number of responses, reducing computational effort and improving the accuracy. The approach incorporates changes in flexural rigidity resulting from strengthening or deterioration, which eliminates the need to reconstruct the prestressed bridge-vehicle system matrix during every step of force identification. To validate the proposed approach, an experimental study was conducted on a simply supported short-span box-girder bridge model, incorporating vehicle excitation. In addition, a numerical medium-span PCB was employed, featuring moving force, to verify the proposed prestress force and moving force identification method. Experimental and numerical results demonstrate the effectiveness of the proposed method for identifying the prestress force and moving force in PCBs with good accuracy using the responses from three locations. In the end, this study will assist bridge managers in evaluating the performance of PCBs to ensure the safety of bridge users, leading to substantial cost savings in bridge maintenance.