BETHLEHEM, PA, Sept. 24, 2021 — In September 2021, the NHERI Lehigh University Experimental Facility unveiled expanded lab space and new equipment for conducting cyber-physical experiments. The enlarged facility opens the door wide for natural hazards researchers to explore structural mitigation solutions for windstorms and earthquakes.

Part of the NSF-funded Natural Hazards Engineering Research Infrastructure, the NHERI Lehigh Experimental Facility specializes in cyber-physical testing, a broad term that encompasses hybrid simulation, including real-time, multi-directional hybrid simulation experiments.

More space, more research opportunities

The new Real-time Cyber-Physical Structural Systems testing laboratory, RCPSS, consists of 2,000 additional square feet of of lab space, new testbeds, and a multi-directional shake table dedicated to cyber-physical testing.

Cyber-physical tests are ideal for large-scale structures that are impractical – or impossible – to test in a normal laboratory. Now, the expanded NHERI Lehigh Experimental Facility can accommodate more users and a broader range of hybrid testing applications.

The NHERI Lehigh RCPSS features five test beds, each with a dedicated dynamic actuator that can be linked to a multi-directional shake table.

“These dedicated test beds exist independently from, but parallel to, our current laboratory setup,” said Jim Ricles, principal investigator and director of the NHERI Lehigh Experimental Facility. “We can now support additional concurrent users in the NHERI Lehigh Experimental Facility, and we can easily link these new testbeds with our existing setup.”

Multi-directional shake table

A real-time integrated control system links the test beds to the multi-directional shake table. This allows users to conduct concurrent tests that are synchronized in real-time by simultaneously engaging the various test beds and the shake table. With efficiency and accuracy, researchers can test multiple structural designs, and multiple design solutions, at once.

“We constructed our shake table in response to user requests, and it has significantly expanded the types of experiments we can run,” said Ricles. “For example, as it moves in the horizontal directions along an X-Y axis, the shake table can mimic the twisting, torsional effects of a structure’s floor under windstorm or earthquake loading.”

Specifications and use-case scenarios for the RCPSS shake table, testbeds and computational controls are available on the NHERI Lehigh Experimental Facility’s website.

Pioneering hybrid experimentation

For more than a decade, the team at NHERI’s Lehigh Experimental Facility has trained and supported natural hazards researchers in cyber-physical testing.

"Our facility is unique in the nation. We are one of the few labs in the U.S. dedicated to supporting large-scale, real-time, 3D cyber-physical testing, and we now provide a greater variety of options for researchers,” said Ricles. “For instance, our new multidirectional shake table can realistically emulate twisting motions that structures sometimes demonstrate under extreme 3-D wind loading due to non-uniform wind pressures acting over the façade of the building along with possible vortex shedding. Further, our new shake table can be deployed in quasi-static testing as well as hybrid simulation experiments.”

Researchers rely on the NHERI Lehigh Experimental Facility to help them design hybrid simulation experiments that combine computer simulations of large structures with physical protective devices. By combining the number-crunching power and accuracy of computer simulations with the physical muscle of hazard mitigation devices, researchers can discover the best ways to protect our civil infrastructure – structures such as industrial and manufacturing facilities, power transmission towers and skyscrapers – from the effects of earthquakes and windstorms.

The real-time integrated control system includes tools for creating complex nonlinear computational models (both with material and geometric nonlinearities) that can be used for numerical simulation or real-time hybrid simulation. Users of the RCPSS can readily perform 3-D real-time hybrid simulations consisting of multiple experimental substructures and nonlinear analytical substructures.

An example real-time hybrid simulation might consist of multiple experimental substructures comprised of structural-response modification devices, devices such as passive or semi-active controlled dampers, tuned mass dampers, or isolation systems. The devices can be placed in the test beds and on the shake table. Then, these experimental substructures, i.e., the physical assemblies, are linked to the analytical substructure, a computational model of the remaining parts of the system, to define the complete system subjected a natural hazard such as an earthquake or wind storm.

Tools are available to include the effects of soil-foundation-structural system interaction in experiments by modeling the soil and foundation numerically as part of an analytical substructure, or by creating another experimental substructure using the facility’s soil boxes.

Benefits of cyber-physical testing

Traditionally, cyber-physical testing has been used to explore performance in large-scale structures. But the hybrid method is valuable for a wide range of experimental programs. Inexpensively and efficiently, hybrid testing can help researchers define and fine-tune the design of hazard mitigation measures. By enabling early investigations to hone in on specific technical challenges, hybrid tests can help researchers advance their investigations faster and with greater accuracy. For example, the RCPSS is available for users to perform pilot studies for generating data to include in their NSF-sponsored research proposals.

Fall training workshops. The staff at the NHERI Lehigh Experimental Facility encourage users of all experience levels to explore the RCPSS. On-site training workshops, which begin at the NHERI Lehigh Experimental Facility this fall, will enable participants to discover how cyber-physical testing can benefit their particular field of investigation. The workshops will demonstrate how hybrid simulation tests work – as both real-time simulations and as quasi-static simulations. Participants will perform hands-on exercises that use the RCPSS test beds, shake table, and 3-D nonlinear modeling resources.

As specialists in cyber-physical testing, the NHERI Lehigh Experimental Facility team is dedicated to educating researchers about ways hybrid experimentation can enhance research programs in natural hazards engineering. The group encourages inquiries from researchers curious about ways cyber-physical testing can advance their work. Please contact NHERI Lehigh research engineer Dr. Liang Cao or facility director Professor James Ricles.

Find details about cyber-physical testing, including the new Real-time Cyber Physical Structural Systems lab, on the NHERI Lehigh Experimental Facility website.

 

Related Links

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Real-Time Cyber-Physical Structural Systems Laboratory

NHERI Lehigh Experimental Facility

NHERI Experimental Facilities