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Abstract This study investigates the experimental response of a hybrid shape memory alloy (SMA) cable-friction damping device with a specific focus on the failure behavior and reparability of the damper when tested at extreme deformations. The superelastic friction damper (SFD) is a hybrid seismic protection device that combines the high tensile strength and re-centering capability of superelastic SMA cables with stable, repeatable energy dissipation of a friction-based damping system. In this paper, the fabrication of a prototype damper and its experimental testing are discussed. The response of the SFD’s friction and self-centering mechanisms were separately evaluated considering design level deformations, cyclic loading, and large deformations up to failure. The performance of the device after the repair of failed components was also investigated. Findings from the study show that the SFD reached failure at a deformation level that exceeded the design displacement by a factor of 2.2. The force capacity of the SFD at the failure stage was 46% higher than the maximum force at the design deformations. After replacing the failed SMA cables, the damper’s mechanical response was identical to the pre-failure response, illustrating the device’s ability to be restored without hindering performance. 

ABSTRACT This data paper presents data obtained from E‐Defense shake‐table tests of a full‐scale, steel moment‐resisting frame (MRF) supplemented with Spines. Herein, the Spines were pin‐based columns with sufficient stiffness and strength to distribute plastic deformation evenly over the height of the MRF. The specimen was tested under two configurations: first, with the Spine rigidly connected to the MRF; second, with the Spine connected to the MRF through force‐limiting connections (FLCs). Each specimen configuration underwent earthquake simulations using ground motions with two scale factors. The tests demonstrated the expected benefits of Spines as well as the disadvantage of inducing large floor accelerations in the structure and large shear forces in the Spines. The tests also demonstrated how the FLCs can mitigate these disadvantages. This data paper reports an overview of the tests, data archive structure, and potential use of the data. The data can be used, for example, to reproduce the observations presented by the authors, to compare the dynamic response of the specimen with building specimens tested in other shake‐table test programs, to validate numerical models against the measured specimen response, or to formulate classroom exercises on system identification of linear and nonlinear systems. 

Abstract Real‐time hybrid simulation (RTHS) involves dividing a structural system into numerical and experimental substructures. The experimental substructure is challenging to model analytically and is therefore modeled physically in the laboratory. Analytical substructures are conventionally modeled using the finite element method. The two substructures are kinematically linked, and the governing equations of motion are solved in real‐time. Thus, the state determination of the analytical substructure needs to occur within the timestep, which is of the order of a few milliseconds. All structural systems are supported by a soil‐foundation system and any evaluation of the efficacy of response modification devices placed in the structure should consider soil‐foundation structure interaction (SFSI) effects. SFSI adds compliance to a structural system, thereby altering the natural frequencies. Additionally, nonlinear behavior in the soil can result in residual deformations in the foundation and structure, as well as provide added damping. These effects can occur under both wind and earthquake loading. To overcome the barrier of the large computational effort required to model SFSI effects in real‐time using the conventional finite element approach, a neural network (NN) model is combined with an explicit‐based analytical substructure and experimental substructure with dampers to create a framework for performing RTHS with SFSI effects. The framework includes a block of long‐short term memory (LSTM) layers that is combined with a parallel rectified linear unit (ReLU) to form a NN model of the soil‐foundation system. RTHS of a tall 40‐story steel building equipped with nonlinear viscous dampers and subjected to a windstorm are performed to illustrate the framework. It was found that a number of factors have an effect on the quality of RTHS results. These include: (i) the discretization of the wind loading into bins of basic wind speed; (ii) the extent of the NN model training as determined by the root mean square error (RMSE); (iii) noise in the restoring forces produced by the NN model and its interaction with the integration algorithm; and, (iv) the bounding of outliers of the NN model's output. Guidelines for extending the framework for the RTHS of structures subjected to seismic loading are provided. 

Abstract In light of the significant damage observed after earthquakes in Japan and New Zealand, enhanced performing seismic force‐resisting systems and energy dissipation devices are increasingly being utilized in buildings. Numerical models are needed to estimate the seismic response of these systems for seismic design or assessment. While there have been studies on modeling uncertainty, selecting the model features most important to response can remain ambiguous, especially if the structure employs less well‐established lateral force‐resisting systems and components. Herein, a global sensitivity analysis was used to address modeling uncertainty in specimens with elastic spines and force‐limiting connections (FLCs) physically tested at full‐scale at the E‐Defense shake table in Japan. Modeling uncertainty was addressed for both model class and model parameter uncertainty by varying primary models to develop several secondary models according to pre‐established uncertainty groups. Numerical estimates of peak story drift ratio and floor acceleration were compared to the results from the experimental testing program using confidence intervals and root‐mean‐square error. Metrics such as the coefficient of variation, variance, linear Pearson correlation coefficient, and Sobol index were used to gain intuition about each model feature's contribution to the dispersion in estimates of the engineering demands. Peak floor acceleration was found to be more sensitive to modeling uncertainty compared to story drift ratio. Assumptions for the spine‐to‐frame connection significantly impacted estimates of peak floor accelerations, which could influence future design methods for spines and FLC in enhanced lateral‐force resisting systems. 

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. 

Abstract Near‐fault pulse‐type ground motions have characteristics that are substantially different from ordinary far‐field ground motions. It is essential to understand the unique effects of pulse‐type ground motions on structures and include the effects in seismic design. This paper investigates the effects of near‐fault pulse‐type ground motions on the structural response of a 3‐story steel structure with nonlinear viscous dampers using the real‐time hybrid simulation (RTHS) testing method. The structure is designed for 75% of the code‐specified design base shear strength. In the RTHS, the loop of action and reaction between the experimental and numerical partitions are executed in real time, accurately capturing the velocity pulse effects of pulse‐type ground motions. A set of 10 unscaled pulse‐type ground motions at the design basis earthquake (DBE) level is used for the RTHS. The test results validated that RTHS is a viable method for experimentally investigating the complicated structural behavior of structures with rate‐dependent damping devices, and showed that the dampers are essentially effective in earthquake hazard mitigation effects involving pulse‐type ground motions. The average peak story drift ratio under the set of pulse‐type ground motions is 1.08% radians with a COV value less than 0.3, which indicated that structural system would achieve the ASCE 7–10 seismic performance objective for Occupancy Category III structures under the DBE level pulse‐type ground motions. Additionally, a nonlinear Maxwell model for the nonlinear viscous dampers is validated for future structural reliability numerical studies involving pulse‐type ground motions. 

This paper presents an experimental study on the multidirectional cyclic lateral-load response of repaired post-tensioned self-centering (SC) controlled-rocking cross-laminated timber (CLT) shear walls (SC-CLT walls). Three SC-CLT wall specimens were investigated: an initially undamaged SC-CLT wall with unreinforced wall panels, a repaired SC-CLT wall with steel-plate reinforcement, and a repaired SC-CLT wall with steel-plate reinforcement and steel bearing plates on the foundation. An evaluation of the experimental response of SC-CLT walls (with and without steel-plate reinforcement) under multidirectional cyclic lateral loading is presented, with emphasis on changes in lateral stiffness and strength caused by damage. Steel-plate wall panel reinforcement is investigated as a repair approach to restore the lateral stiffness and strength of damaged SC-CLT walls. Steel bearing plates are used to repair (or avoid) localized damage to a concrete foundation when a steel plate–reinforced SC-CLT wall rocks on the foundation. The damage mechanisms affecting the changes in lateral stiffness and strength of each SC-CLT wall specimen are discussed. Assessment of the experimental results demonstrate that these repair methods are effective in restoring the lateral stiffness and strength of a damaged SC-CLT wall 

Real-time Hybrid Simulation (RTHS) is a technique wherein a structural system is divided into an analytical and an experimental substructure. The former is modeled numerically while the latter is physically present in the laboratory. The two substructures are kinematically linked together at their interface degrees of freedom (DOFs) and the equations of motion are solved in real-time to determine the structure’s response. One of the main challenges of RTHS is to include the effects of soil–foundation–structure interaction (SFSI), which can have a substantial effect on the overall response. The soil domain cannot be modeled experimentally due to the large payload size. On the other hand, modeling the soil domain numerically, using a continuum-based approach, in real-time is challenging due to the associated computational cost. To address these issues, this paper presents a framework for seismic RTHS of SFSI systems using a Neural Network (NN)-based macroelement model of the soil–foundation system. A coupled SFSI model is used to train the NN model and the loss function is based on dynamic equilibrium at the interface between the foundation and the structure. The framework is demonstrated using a three-story building with the lateral load resisting system comprised of moment resisting and damped brace frames. The proposed framework ensures a stable and accurate RTHS, accounting for SFSI by incorporating: (a) spring elements at the output DOFs of the NN model to remove rigid body modes; (b) dashpot elements at the output DOFs of the NN model to mitigate spurious higher frequencies of vibration; and (c) regularization in the NN model’s architecture with data augmentation to reduce overfitting. 

Natural hazards, including hurricanes and earthquakes, can escalate into catastrophic societal events due to the destruction of the built environment. To minimize the impact of such hazards on vulnerable communities, civil infrastructure must be designed with performance criteria that prioritize public safety and ensure continuous operation. The National Science Foundation funded Natural Hazards Engineering Research Infrastructure (NHERI) program focuses on advancing the development of resilient infrastructure. The NHERI Lehigh Real-time Multi-directional Simulation Experimental Facility (EF) is one of the facilities within this program. The facility serves as an open-access research hub, offering advanced technologies and engineering tools to develop innovative solutions for natural hazard mitigation. It is uniquely equipped to perform large-scale, multi-directional structural testing in real-time using a cyber-physical simulation technique known as real-time hybrid simulation. This technique enables researchers to model entire systems subjected to dynamic loads at a full scale, allowing for realistic assessments of infrastructure responses to specific hazard scenarios and the development of effective mitigation strategies. This paper explores how cyber-physical simulation has revolutionized research in natural hazards engineering and its influence on engineering practices. It highlights several ongoing projects at the NHERI Lehigh EF aimed at enhancing community resilience in hazard-prone regions. The paper also discusses the planned expansion of the EF, which aims to broaden its focus to include a wider range of natural hazards, and infrastructure systems. This expansion will incorporate both physical and computational resources to enhance the understanding of fluid interactions in combined natural hazards and climate change impacts on coastal and offshore infrastructure. The NHERI Lehigh EF represents a transformative facility that is reshaping natural hazards research and will continue to play a pivotal role in the development of risk management strategies for more resilient communities. 

This dataset contains data from E-Defense shake-table tests of a full-scale, steel moment-resisting frame (MRF) supplemented with spines. Herein, the spines were pin-based columns with sufficient stiffness and strength to distribute plastic deformation evenly over the height of the MRF. The specimen was tested under two configurations: first, with the spine rigidly connected to the MRF; and second, with the spine connected to the MRF through Force-Limiting Connections (FLCs). The two structural systems were subjected to two ground motions adjusted to two different scales. The tests highlighted the expected benefits of spines as well as their drawbacks of inducing large floor acceleration in the MRF and large shear forces in the spines themselves. The tests also highlighted how the FLCs can mitigate such drawbacks of spines. The data may be used, for example, to reproduce the observations presented by the authors, to compare the dynamic response of the specimen with building specimens tested in other shake-table test programs, to validate numerical models against the measured specimen response, or to formulate classroom exercises on system identification of linear and nonlinear systems.