Identification of prestress force from measured structural responses

A method for the identification of prestress force of a prestressed concrete bridge deck is presented using the measured structural dynamic responses. A Euler–Bernoulli beam finite element model is used to represent the bridge deck, and the prestress force is modelled as the axial prestress force in each beam element. The state-space approach is used to calculate the dynamic responses of the structure and the sensitivities of dynamic responses with respect to the structural parameters, such as the prestress force, flexural rigidity, etc. The prestress force in each beam element is taken to be a system parameter, and it is expressed explicitly in the system equation for forward analysis. The prestress force in each element is identified using a sensitivity-based finite element model updating method in the inverse analysis. Data obtained from a single or multiple accelerometers or strain gauges are used in the identification. Both sinusoidal and impulsive excitations are illustrated to give very good results. Two numerical simulations are presented to illustrate the effectiveness and robustness of the proposed method. Laboratory work on an axially prestressed concrete beam is also included as a practical application.