Fast hybrid simulation with geographically distributed substructures

A distributed control strategy is presented that supports the implementation of hybrid (pseudodynamic) testing with geographically distributed substructures. The objectives of the distributed controller are: (1) to provide a scalable framework for multiple substructure testing at distributed sites and (2) to improve the reliability of the test results by minimizing strain-rate and force relaxation errors in the remote experimental substructures. The control strategy is based on a multi-threaded simulation coordinator combined with an event-driven controller at the remote experimental sites. The multi-threaded coordinator is applied to simultaneously load multiple remote substructures at different sites. The event-driven remote site controller allows for the implementation of continuous hybrid simulation algorithms on distributed models where computation, network communication and other tasks may have random completion times. The advantage of this approach is that the hold phase in conventional ramp-hold pseudodynamic testing is minimized, if not eliminated. The effectiveness of this procedure is demonstrated by computing the earthquake response of a six-span bridge model with five remote experimental and numerical column substructures distributed within NEES facilities. Further, the distributed control strategy was implemented on NEESGrid to provide a secure network link between the distributed NEES equipment sites. Results from these simulations are presented, including a summary of the tasks times.