Recent earthquakes in many parts of the world have resulted in
damage to the civil infrastructure, resulting in fatalities and economic loss. This
experience has resulted in stake holders demanding a more resilient infrastructure
and the mitigation of earthquake hazards to minimize their impact on
society. Researchers have developed concepts for structural steel systems to
promote resilient performance. Real-time hybrid simulation (RTHS) provides an
experimental technique to meet the need to validate new concepts. RTHS
enables a complete structural system, including the soil and foundation to be
considered in a simulation, interaction effects and rate dependency in component
and system response to be accounted for, and realistic demand imposed onto the
system for prescribed hazard levels. This paper presents the concept of RTHS
and developments achieved at the Lehigh NHERI Experimental Facility that
have advanced RTHS to enable accurate large-scale, multidirectional simulations
involving multi-natural hazards to be performed. The role that hybrid
simulation has played in these developments and how its use has enabled a
deeper understanding of structural system behavior under seismic and wind
loading will be discussed. Examples include self-centering steel moment
resisting frame systems, braced frame systems with nonlinear viscous, and tall
buildings with outriggers that are outfitted with nonlinear viscous.
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Natural Hazards Research Summit 2022: Multi-Directional Cyber-Physical Experimental Testing to Establish Multi-natural Hazard Resiliency of Structural Systems and Building Content Hazard Mitigation
Protecting both the essential building contents and the structural system—as well as facilitating and accelerating the post-event functionality of business operations—is a major concern during natural hazards. Floor isolation systems (FIS) with rolling pendulum bearings along with nonlinear fluid viscous dampers (NFVD) have been proposed to mitigate damage and enhance the resiliency of non-structural and structural systems, respectively. These devices are designed to decrease vibrations under dynamic loading conditions. In this poster, we introduce research using tridimensional nonlinear cyber-physical experimental testing (i.e., real-time hybrid simulations) to validate the performance of these response modification devices placed in structural systems under wind and earthquake loading conditions. The effects of soil-structure-foundation and fluid-structure interactions were also accounted for. The novelty of the project is the use of multi-directional large-scale real-time hybrid simulations of complex nonlinear systems under wind and earthquake demands to combine experimental structural modification passive devices with analytical multi-story buildings considering soil-foundation interaction via neural network. Results show that the FIS and NFVD can significantly reduce the demand on non-structural and structural systems of buildings subjected to natural hazards whose response can be also significantly affected by soil-foundation-structure interaction. A product of this research is the data (which is linked in Related Works), which can be used to compare with new studies using the same experimental techniques and structural modification devices or with alternative approaches. Researchers interested in multi-natural hazards resilience and mitigation, state-of-the-art structural experimental techniques, and the use of machine learning as a tool to improve modeling efficiency will benefit from its results. Also, companies dedicated to the commercial development of structural response modification devices, as well as policymakers working or with interest in economic and social resilience.
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- NSF-PAR ID:
- 10410705
- Publisher / Repository:
- Designsafe-CI
- Date Published:
- Subject(s) / Keyword(s):
- ["Lehigh University NHERI Experimental Facility","real-time hybrid simulation","critical non-structural equipment","seismic isolation","non-linear fluid viscous dampers","soil-foundation-structure interaction","physics-based machine learning neural network"]
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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The system under investigation is a 40 story building. Real-time hybrid simulations (RTHSs) were performed on the building, where the structure is separately subjected to multi-natural hazards consisting of a 110 mph sustained wind storm and 43 second earthquake. Nonlinear viscous dampers between the outrigger truss and perimeter columns are placed at stories 20th and 30th. The outcome of the tests was to assess the ability of the damped outrigger system to suppress undesirable floor wind accelerations and reduce earthquake story drift and damage. The data collected from the tests can be reused by replaying the real-time hybrid simulation offline, where all of the response quantities of the building can be retrieved. The data can be reused to study the response of tall buildings with outriggers and passive dampers subjected to wind and earthquake natural hazards.more » « less
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Design code-based “life-safety” requirements for structural earthquake and tsunami design offer reasonable guidelines to construct buildings that will remain standing during a tsunami or seismic event. Much less consideration has been given to assessing structural resilience during sequential earthquake and tsunami multi-hazard events. Such events present a series of extreme loading scenarios, where damage sustained during the earthquake influences structural performance during the subsequent inundation. Similar difficulties exist with respect to damage sustained during tropical events, as wind and fluid loading may vary with structural response or accumulated damage. To help ensure critical structures meet a “life-safety” level of performance during such multi-hazard events, analysis software capable of simulating simultaneous structural and fluid dynamics must be developed. To address this gap in understanding of non-linear fluid-structure-interaction (FSI), an open-source tool (FOAMySees) was developed for simulation of tsunami and wave impact analysis of post-earthquake non-linear structural response of buildings. The tool is comprised of the Open-source Field Operation And Manipulation software package and OpenSeesPy, a Python 3 interpreter of OpenSees. The programs are coupled
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Abstract Damage caused by earthquakes to buildings and their contents (e.g., sensitive equipment) can impact life safety and disrupt business operations following an event. Floor isolation systems (FISs) are a promising retrofit strategy for protecting vital building contents. In this study, real‐time hybrid simulation (RTHS) is utilized to experimentally incorporate multi‐scale (building–FIS–equipment) interactions. For this, an experimental setup representing one bearing of a rolling pendulum (RP) based FIS is studied—first through characterization tests and then through RTHS. A series of tests was conducted at the Natural Hazards Engineering Research Infrastructure (NHERI) Experimental Facility at Lehigh University. Multiple excitations were used to study the experimental setup under uni‐axial loading. Details of the experimental testbed and test protocols for the characterization and RTHS tests are presented, along with results from these tests, which focused on the effect of different rolling surface treatments for supplemental damping, the FIS–equipment and building–FIS interactions, and rigorous evaluation of different RP isolation bearing designs through RTHS.
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null (Ed.)Floor isolation systems (FISs) are used to mitigate earthquake-induced damage to sensitive building contents and equipment. Traditionally, the isolated floor and the primary building structure (PS) are analyzed independently, assuming the PS response is uncoupled from the FIS response. Dynamic coupling may be non-negligible when nonlinearities are present under large deflections at strong disturbance levels. This study investigates a multi-functional FIS that functions primarily as an isolator (i.e., attenuating total acceleration sustained by the isolated equipment) at low-to-moderate disturbance levels, and then passively adapt under strong disturbances to function as a nonlinear (vibro-impact) dynamic vibration absorbers to protect the PS (i.e., reducing inter-story drifts). The FIS, therefore, functions as a dual-model vibration isolator/absorber system, with displacement dependent response adaptation. A scale experimental model—consisting of a three-story frame and an isolated mass—is used to demonstrate and evaluate the design methodology via shake table tests. The properties of the 3D-printed rolling pendulum (RP) bearing, the seismic gap, and the impact mechanism are optimized to achieve the desired dual-mode performance. A suite of four ground motions with varying spectral qualities are used, and their amplitudes are scaled to represent various hazards—from service level earthquake (SLE), to design basis earthquake (DBE), and even maximum considered earthquake (MCE). The performance of the multi-functional FIS is established and is described in this paper.more » « less
