Abstract
In order to improve the current knowledge on structural behavior subject to extreme dynamic loading and mitigate the existing threats against civil infrastructures, embracing the new technologies in experimental evaluation of civil structures are necessary. As civil structures evolve to achieve the needs of future generations, they need to achieve more robustness and resilience under an extremely wide range of operating conditions and hazards, for their design, implementation, validation, and evaluation. Thus, civil engineers are working to develop novel smart structures that are resilient to natural hazards and demonstrate the effectiveness of performance-based design. These challenges justify the need for more experimental capabilities in evaluating structural performances in a suitable and cost-effective manner. Hybrid simulation attempts to combine the realism of shake table testing with the economy and convenience of quasi-static testing. In hybrid simulation, the structure under investigation (i.e., the reference structure) is partitioned into two substructures, (1) numerical (or analytical) substructure, which usually includes well-studied components and (2) physical (or experimental) substructure, which usually includes more complex components while the coupling between the two substructures is achieved by enforcing equilibrium and compatibility at the interface. Real-time hybrid simulation (RTHS) provides the most advanced experimental technique to evaluate the performance of rate-dependent civil structures in laboratories. In RTHS, the interface interaction between the substructures is enforced by a transfer system which includes servo-hydraulic actuator(s) and/or shake table. To implement RTHS, there is a continuous exchange of information between the cyber and physical components. Due to the dynamics of the transfer system, communication and computation delays, the feedback force signals are dependent on the system state subject to delay. In RTHS, communication delays vary from almost negligible for an RTHS using a single processor (no network) to more than a hundred milliseconds for geographically distributed testing. Geographically distributed RTHS presents a challenge in which the required communication over the Internet results in random delays. In this paper, we propose a technique to enable researchers to conduct real-time hybrid simulations at unprecedented scales of size, timing, and complexity using a series of xPC target systems. xPC target system is a real-time software environment from MathWorks enabling researchers to execute Simulink and Stateflow models on a target computer for hardware-in-the-loop (HIL) simulation, rapid control prototyping, and other real-time testing applications. Herein, a simulation tool has been developed and published on the NEEShub (nees.org), a public collaboration platform developed for earthquake engineering research. Finally, an example of a distributed RTHS will be provided in which a four-story structure will be partitioned into two numerical substructures and a physical substructure. And results of (i) a pure simulation and (ii) a distributed RTHS will be shown and the integrity of numerical models and performance of the developed simulation tool will be evaluated.