SUMMARYIn order to predict the dynamic response of a complex system decomposed by computational or physical considerations, partitioned procedures of coupled dynamical systems are needed. This paper presents the convergence analysis of a novel parallel interfield procedure for time-integrating heterogeneous (numerical/physical) subsystems typical of hardware-in-the-loop and pseudo-dynamic tests. The partitioned method is an extension of the method originally proposed by Gravouil and Combescure which utilizes a domain decomposition enforcing the continuity of the velocity at interfaces. In particular, the merits of the new method which can couple arbitrary Newmark schemes with different time steps in different subdomains and advance all the substructure states simultaneously are analysed in terms of accuracy and stability. All theoretical results are derived for single-and two-degrees-of-freedom systems, as a multi-degree-of-freedom system is too difficult to analyse mathematically. However, the insight gained from the analysis of these coupled problems and the conclusions drawn are confirmed by means of the numerical simulation on a four-degrees-of-freedom system.

SUMMARYThis paper presents novel predictor-corrector time-integration algorithms based on the Generalizedmethod to perform pseudo-dynamic tests with substructuring. The implicit Generalized-algorithm was implemented in a predictor-one corrector form giving rise to the implicit IPC-∞ method, able to avoid expensive iterative corrections in view of high-speed applications. Moreover, the scheme embodies a secant sti ness formula that can closely approximate the actual sti ness of a structure. Also an explicit algorithm endowed with user-controlled dissipation properties, the EPC-b method, was implemented. The resulting schemes were tested experimentally both on a two-and on a six-degrees-of-freedom system, using substructuring. The tests indicated that the numerical strategies enhance the ÿdelity of the pseudo-dynamic test results even in an environment characterized by considerable experimental errors. Moreover, the schemes were tested numerically on severe non-linear substructured multiple-degrees-offreedom systems reproduced with the Bouc-Wen model, showing the reliability of the seismic tests under these conditions.

This paper focuses on the formulation and implementation of explicit predictor} multicorrector Time Discontinuous Galerkin methods for linear structural dynamics. The formulation of the schemes is based on piecewise linear functions in time that approximate displacements and momenta. Both the predictors and correctors are designed to inherit third order accuracy from the exact parent implicit Time Discontinuous Galerkin method. Moreover, they are endowed with large stability limits and controllable numerical dissipation by means of an algorithmic parameter. Thereby, the resulting algorithms appear to be competitive with standard explicit algorithms for structural dynamics. Representative numerical simulations are presented illustrating the performance of the proposed numerical schemes and con"rming the analytical results.

SUMMARYA variant of the Rosenbrock-W integration method is proposed for real-time dynamic substructuring and pseudo-dynamic testing. In this variant, an approximation of the Jacobian matrix that accounts for the properties of both the physical and numerical substructures is used throughout the analysis process. Only an initial estimate of the stiffness and damping properties of the physical components is required. It is demonstrated that the method is unconditionally stable provided that specific conditions are fulfilled and that the order accuracy can be maintained in the nonlinear regime without involving any matrix inversion while testing. The method also features controllable numerical energy dissipation characteristics and explicit expression of the target displacement and velocity vectors. The stability and accuracy of the proposed integration scheme are examined in the paper. The method has also been verified through hybrid testing performed of SDOF and MDOF structures with linear and highly nonlinear physical substructures. The results are compared with those obtained from the operator splitting method. An approach based on the modal decomposition principle is presented to predict the potential effect of experimental errors on the overall response during testing.

In a comprehensive experimental campaign, we investigated the capabilities of Fiber Bragg Grating (FBG) sensors in monitoring the inelastic response of new circular concrete tunnel linings, subjected to seismic events. The FBG sensors measured the strains of steel reinforcement to be treated by a decision support system (DSS). First, a set of four‐point bending tests was performed on tunnel substructures, with the aim of characterizing the cross‐section under cyclic loading and of designing an FBG sensor package for use in a unique full‐scale test on a structure, which represented a complete circular section of the tunnel lining. Several types of FBG packages, to be embedded in and applied externally to the tunnel section, were tested to find the best solution. For comparison purposes, some standard devices were also used. The results of the experimental campaign are presented in detail, highlighting the performance of FBG sensors in reliable inelastic strain measurement of ductile concrete sections in seismic zones. Finally, the use of these data by a DSS allowed for the estimate of current structural conditions and damage at the monitored sections.