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Steel energy dissipators can be combined with mass timber in integrated seismic lateral force–resisting systems to achieve designs with enhanced seismic performance and sustainability benefits. Examples of such integration include the use of mass timber post-tensioned rocking walls equipped with steel energy dissipation devices. This study proposes a solution using buckling-restrained boundary elements (BRBs) with mass timber walls detailed to pivot about a pinned base. This design allows the walls to rotate with minimal flexural restraint, distributing drift demands more uniformly with building height and reducing crushing damage at the wall base. Experimental quasi-static cyclic tests and numerical simulations were used to characterize the first- and higher-mode behavior of a full-scale three-story building featuring a mass timber gravity system and the proposed mass timber-BRB system. Under first-mode loading, the specimen reached 4% roof drift ratio with stable hysteretic behavior and a nearly uniform story drift profile. While residual drifts were nonnegligible due to the lack of self-centering, analytical estimates indicate realignment is likely feasible at the design earthquake level. Under second-mode loading, the specimen exhibited near-linear behavior with high stiffness. Experimental results were corroborated with numerical simulations for the isolated gravity frame, first-mode-like, and second-mode-like loading protocols. It is expected that results from this study will facilitate greater use of mass timber seismic lateral force–resisting systems. 

Unmanned aerial vehicle (UAV) vision-based sensing has become an emerging technology for structural health monitoring (SHM) and post-disaster damage assessment of civil infrastructure. This article proposes a framework for monitoring structural displacement under earthquakes by reprojecting image points obtained courtesy of UAV-captured videos to the 3-D world space based on the world-to-image point correspondences. To identify optimal features in the UAV imagery, geo-reference targets with various patterns were installed on a test building specimen, which was then subjected to earthquake shaking. A feature point tracking-based algorithm for square checkerboard patterns and a Hough Transform-based algorithm for concentric circular patterns are developed to ensure reliable detection and tracking of image features. Photogrammetry techniques are applied to reconstruct the 3-D world points and extract structural displacements. The proposed methodology is validated by monitoring the displacements of a full-scale 6-story mass timber building during a series of shake table tests. Reasonable accuracy is achieved in that the overall root-mean-square errors of the tracking results are at the millimeter level compared to ground truth measurements from analog sensors. Insights on optimal features for monitoring structural dynamic response are discussed based on statistical analysis of the error characteristics for the various reference target patterns used to track the structural displacements. 

Abstract The utilization of mass timber engineered wood products has increased for new buildings aiming to reduce environmental impacts. Whole-building life-cycle assessment (WBLCA) has been used to quantify the environmental impacts for a building’s lifespan. While mechanisms for calculating the cradle-to-grave impacts of a single building are well established, there are few examples of WBLCA applied for buildings in their first and second life that can be used to inform perspectives and pathways related to the circular economy and lead to informed decision making. This work presents a case study WBLCA to examine the effect of overlapping system boundaries and alternative end-of-life pathways for a building structure in its first and second life. This case study analyzed a ten-story mass timber shake-table specimen that was partially deconstructed and reused as a six-story shake-table building structure. Environmental impacts were analyzed in terms of global warming potential (GWP) calculated as the sum of fossil carbon, biogenic carbon, and avoided impacts. When examining reuse and landfill pathway alternatives using current standards and practices, results show that reusing material causes a positive GWP trend in the first system boundary and negative GWP trend in the second boundary. These results could indicate that it is not advantageous to reuse the ten-story building structure, running against principles of waste hierarchy, although the interpretation should be considered with caution. Future analyses could be improved by considering additional criteria such as demand on forest stocks, economic incentives, and even social impacts for a more complete representation of sustainability. 

Mass timber solutions are becoming more and more viable for high-seismic regions while remaining sustainable, efficient, and affordable. The industry is driving innovation leading to the development of resilient hybrid steel-mass timber solutions that can minimize post-earthquake losses and downtime. A resilient six-story hybrid mass timber structure with: [i] laminated veneer lumber (LVL) beams and columns, [ii] a cross-laminated timber (CLT) selfcentering rocking wall (SCRW) in one direction, and [iii] a steel moment frame/concentric braced frame (MF/CBF) in the other direction was tested at the University of California, San Diego (UCSD) large high-performance outdoor shaketable facility. The dynamic testing included uni-, bi-, and tri-directional ground motion time histories applied at increasing intensities, including 43- and 225-year hazard levels, design earthquake (DE) level, and risk-targeted maximum considered earthquake (MCER) level per ASCE 7-16 for a location in Seattle, Washington. Four (4) design earthquakes and two (2) risk-targeted maximum considered tri-directional earthquakes were applied to the structure. Testing resulted in peak story drift ratios of 2.4% and 1.4% in the SCRW and MF/CBF directions, respectively. Even at MCER levels of shaking, the performance-based seismic design allowed for (1) the CLT-SCRW to remain essentially undamaged and (2) the MF to remain essentially elastic, providing elastic restoring forces, while the CBF provided stable and controlled hysteretic energy dissipation. After testing, residual drifts were smaller than 1.6 mm (1/16 inch) at the roof, indicating that resilient hybrid mass timber-steel structures are viable. This paper presents the specimen design and summarizes the preliminary results from the shake-table testing. 

A full-scale, six-story, mass timber building including Mass Ply Panel (MPP) self-centering rocking walls with Buckling-Restrained Boundary Elements (BRBs) was tested at the Large High-Performance Outdoor Shake Table (LHPOST6) at the University of California, San Diego (UCSD). Measured sensor and derived data included global responses, such as floor displacements and accelerations, along with local responses, such as post-tensioning (PT) forces and uplift displacements, among others. The three-dimensional shake table testing program included 23 ground motion records with intensities of shaking ranging from Service (SLE) up to Risk-Targeted Maximum Considered Earthquake (MCER) levels. Results highlighted that: [i] the drift response was near uniform along the height of the building, [ii] the acceleration response included large contributions from the higher modes, [iii] the PT rods remained elastic and had stable post-tensioning force throughout the test program, and [iv] the self-centering system resulted in negligible residual drifts. Qualitative observations from construction and testing were also cataloged to further support the feasibility of implementation in practice. By combining steel BRBs and post-tensioning rods with MPP rocking elements, the system was able to meet the enhanced seismic performance goals targeted for the project. Future work will seek to define both resilience and sustainability targets for designs incorporating multiple performance objectives. 

Advancements in materials, components, and building systems over the past decade have enabled the construction of taller mass timber structures, creating new opportunities for seismic design in mid- and high-rise buildings. This paper presents a systematic comparison of two full-scale shake table test programs-the 10-story NHERT TallWood and the 6-story NHERT Converging Design both conducted at the University of California, San Diego (UCSD) Large High-Performance Outdoor Shake Table (LHPOST). These projects aimed to develop and validate seismic design approaches for wood buildings in high seismic regions. Both structures employed a self-centering mass timber rocking wall system with distributed energy dissipation provided by U-shaped Flexural Plates (UFPs), enabling direct comparison of structural response and design considerations across different building heights. Despite ongoing innovations, many tall timber buildings still rely on concrete cores or steel braced frames for lateral resistance due to a limited number of code- approved timber systems and an industry preference for traditional solutions. This comparative study highlights the performance of timber-based lateral systems under seismic loading and supports their broader adoption in resilient, mid-and high-rise construction. 

A veneer-based engineered wood product known as Mass Ply Panels (MPP) was recently introduced and certified per ANSI-PRG 320. A full-scale three-story mass timber building structure was constructed and tested at Oregon State University to demonstrate the potential of MPP in the design of resilient, structural lateral force-resisting systems. The building structure comprised MPP diaphragms, laminated veneer lumber (LVL) beams and columns, and an MPP rocking wall design. Two opportunistic vibration tests were performed to charac-terize the dynamic properties of the structure. First, an implosion of a stadium within 600 m of the building location was used as the main excitation source, during which bi-directional horizontal acceleration data were collected for approximately 18 seconds. Second, an ambient vibration test was conducted to collect horizontal acceleration data for one hour. In both tests, sixteen accelerometers were used to measure the response of the structure. Modal features were extracted using an output-only method and compared with the estimates from a finite element model. Lessons learned can be used to inform future modeling efforts of a mass timber building to be tested on the Natural Hazards Engineering Research Infrastructure (NHERI) Experimental Facility at the University of California San Diego high-performance outdoor shake table. 

Fragility functions and recovery models are often used to assess lifeline systems subjected to extreme hazards. However, even though many databases for fragility and recovery models exist for essential buildings and transportation systems, fragility and recovery models for other lifelines are fragmented across the literature. This article provides a comprehensive review of the state-of-the-art seismic fragility functions and recovery models for energy (power, liquid fuel, and gas), water, and wastewater systems that can be applied in hazard risk and resiliency assessments of communities. The review focuses on fragility and recovery model parameters and summarizes the methods and validation used in developing the models. In addition, the reviewed fragility functions are compiled in an open-source database with a graphical user interface. Critical gaps in the literature are discussed to guide future research endeavors. 

Numerical analyses can aid design exploration, but there are several computational approaches available to consider design options. These range from “brute-force” search to optimization. However, the implementation of optimization can be challenging for the complex, time-intensive analyses required to assess seismic performance. In response to this challenge, this study tests several optimization strategies for the direct displacement-based design of a lateral force-resisting system (LFRS) using mass timber panels with U-shaped flexural plates (UFPs) and post-tensioning high-strength steel rods. The study compares two approaches: (1) a brute-force sampling of designs and data filtering to determine acceptable solutions; and (2) various automated optimization algorithms. The differential evolution algorithm was found to be the most efficient and robust approach, saving 90% of computational cost compared to bruteforce sampling while producing comparable solutions. However, every optimization formulation did not return best range of design options, often requiring reformulation or hyperparameter tuning to ensure effectiveness.