Advanced Technology for Large Structural Systems
A National Engineering Research Center

Visiting Researcher from University of Oklahoma Conducts Tests at NHERI Lehigh

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From L to R: P. Scott Harvey, Associate Professor in the School of Civil Engineering and Environmental Science at the University of Oklahoma; Braulio Covarrubias Vargas, graduate student; James Ricles, Bruce G. Johnston Professor of Structural Engineering and Director of Lehigh’s Real-Time Multi-directional Earthquake Simulation Facility.

In August, P. Scott Harvey, Associate Professor in the School of Civil Engineering and Environmental Science at the University of Oklahoma, spent five weeks conducting research at Lehigh’s Natural Hazards Engineering Research Infrastructure (NHERI) Experimental Facility. The facility operates within I-CPIE’s Advanced Technology for Large Structural Systems (ATLSS) Engineering Research Center. Preceded by Lehigh’s Network for Earthquake Engineering Simulation NEES Real-time Multi-directional facility, the NHERI facility was established in 2016 under funding from the National Science Foundation (NSF) to help meet the grand challenge of community resilience to natural hazards.

The research Harvey conducted was related to enhancing the resilience of essential facilities, like hospitals or power plants, to seismic hazards by protecting sensitive, critical equipment through floor isolation systems (FISs), which decouple the motion of the floor from the response of the object during an earthquake. “By reducing or eliminating downtime in the wake of an earthquake,” Harvey noted, “FISs are a promising retrofit strategy for protecting vital building contents.”

While at NHERI Lehigh, Harvey and a graduate student conducted tests to characterize and evaluate a FIS configured with a rolling pendulum isolation bearing and augmented rolling resistance. Using NHERI Lehigh’s state-of-the-art real-time hybrid simulation (RTHS) capabilities, they performed an extensive series of cyber-physical tests that incorporated multi-scale (FIS-equipment and building-FIS) interactions. The research is supported by the NSF through the Established Program to Stimulate Competitive Research (EPSCoR) RII Track-4 (award no. OIA-1929151), a fellowship program that furthers individual research potential through extended collaborative visits to premier academic research centers like NHERI Lehigh.

Harvey said that as a researcher in the field of earthquake engineering, he has known about NHERI Lehigh, “since its inception…because of the renowned research conducted at ATLSS over the years.” He found that the Lehigh personnel’s expertise in RTHS eased the development of the test protocol and expedited the setup time for testing, which allowed for a greater breadth of tests to be conducted. Harvey and the graduate student also received training in RTHS from the leaders in the field, NHERI Lehigh, which was a criterion for the fellowship program.

Lehigh’s Real-Time Multi-directional Earthquake Simulation Facility is under the direction of James Ricles, Bruce G. Johnston Professor of Structural Engineering. Referring to NHERI Lehigh’s portfolio of equipment, instrumentation, infrastructure, testbeds, experimental simulation control protocols, large-scale simulation and testing experience, Ricles said, “we are an open-access facility within the NHERI network and as a leader in RTHS, provide a unique opportunity for visiting researchers like Dr. Harvey to conduct their research requiring accurate, large-scale, multi-degree-of-freedom and multi-directional simulations of the effects of natural hazard events on civil infrastructure systems.”

After meeting at an NSF-sponsored workshop in Japan in 2015, Ricles and Harvey kept in touch about Harvey using NHERI Lehigh as the host site for the EPSCoR RII Track 4 fellowship program. Ricles invited Harvey to the annual NHERI Researcher’s Workshop, which allows researchers to learn about the capabilities of NHERI facilities at Lehigh, UC San Diego, and the UC Berkeley SimCenter. The workshop provided Harvey an opportunity to see first-hand the facilities at NHERI Lehigh. While working on his proposal over the next two years, Harvey stayed in touch with Ricles, who worked closely with Harvey to incorporate NHERI Lehigh as the host site.

The five-week visit in August constituted Phase 1 of Harvey’s research. Because of the COVID-19 pandemic, the visit included a 14-day quarantine prior to the research starting, as well as masks, social distancing, and other COVID-19 safety protocols, per Lehigh University policy. Phase 2 is planned for three months during summer 2021 and will include the development of an experimental testbed for multi-directional RTHS testing of FISs.

Ultimately, this research will help advance understanding of these devices’ complicated nonlinear dynamics. The data collected during the Phase 1 visit will be used to calibrate and validate physics-based mathematical models of the rolling pendulum bearings. The research Harvey is conducting at NHERI Lehigh builds on years of research related to equipment isolation by his group at the University of Oklahoma.

“To date, tests conducted at the University of Oklahoma’s Fears Structural Engineering Lab have primarily involved shake-table tests of FISs, but these tests have been limited by payload and dimension capacities of our facilities,” he said, “…furthermore, building-FIS interactions cannot be incorporated using a shake table.” NHERI Lehigh’s RTHS capabilities allowed Harvey to overcame these limitations and constitute the first ever RTHS tests of FISs. Harvey also said that the RTHS capabilities permitted him to investigate an FIS’s performance at mitigating vibrations from wind loading on a 40-story building, which is a potential new direction for these devices.