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Time domain substructural condition assessment method is actively researched in recent years to avoid the problem with uncertainties in the different components of the structure, boundary conditions and with an improved effort in the inverse computation. Since the interface force between substructures would vary with the existence of local damages and excitation in the substructures, existing condition assessment method for a full structure cannot be applied directly to the substructures. Also, most existing approaches adopt the state space method in the response prediction. However, the state space method can be shown in this paper inaccurate in the forward substructural dynamic analysis due to the discretization error, and therefore identification based on this method cannot give satisfactory result for a substructure. The force identification for a full structure based on the explicit Newmark-β method has been shown superior to the state space method [K. Liu et al., J. Sound Vibr.33(3) (2014) 730–744]. This method is extended in this paper for substructural interface force identification. The variation of interface forces between substructures with variation in the substructural condition is illustrated with a plane truss structure. Subsequent condition assessment based on substructural response sensitivity is proposed with the analytical derivation of the sensitivity taking into account the interface force sensitivity which is not small to be ignored. The new damage detection method based on the explicit Newmark-β method and the substructural response sensitivity is verified numerically with different damage scenarios in a plane truss structure giving satisfactory results.

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