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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. 

The Natural Hazards Engineering Research Infrastructure (NHERI) Converging Design project is a collaborative effort between multiple universities and industry entities with the goal of creating a new design paradigm in structural engineering that employs multi-objective optimization to maximize functional recovery while integrating sustainability principles in the design process. The structural design approaches were validated through full-scale shake table testing of a 6-story mass timber structure at the at the Englekirk Structural Engineering Center at University of California, San Diego (NHERI@UCSD) Large High-Performance Outdoor Shake Table (LHPOST6) facility for eventual inclusion in a multi-objective design optimization framework. The shake table testing included three phases. Phase one consisted of a mass timber self-centering rocking wall (SCRW) system with U-shaped flexural plates (UFPs) in both building horizontal directions. Phase two replaced the SCRWs in one principal direction with SCRWs with buckling restrained boundary elements (BRBs) at the first story. Phase three replaced the newer walls from phase two with a resilient steel moment frame and concentric braced-frame (MF/CBF). The data shared includes reports summarizing the testing program, structural drawings, instrumentation setups, and raw data for the series of shake table tests performed during each phase. The data include building responses due to shake table motions simulating scaled historical ground motions and white noise (WN) tests. 

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. 

This paper describes the lateral force resisting system (LFRS) design in a full-scale six-story shake-table test building and presents a comparative cradle-to-grave life-cycle assessment of alternative LFRSs. The test building features the reuse of material from a ten-story shake-table structure comprised of engineered mass timber (MT) products. These include MT floors (cross-, glue-, nail-, and dowel-laminated timber [CLT], [GLT], [NLT], [DLT]); MT posttensioned rocking walls (CLT and mass ply panels [MPP]); and a gravity system consisting of laminated-veneer lumber (LVL) beams and columns. Shake-table testing will benchmark innovative, low-damage design solutions for the LFRSs. To supplement this test, the environmental impact of a MT LFRS is determined relative to design alternatives that use conventional materials. The Athena Impact Estimator for Buildings was used to perform a comparative, cradle-to-grave life-cycle assessment (LCA) of the prototype MT LFRS with respect to an alternative, functionally equivalent reinforced concrete (RC) shear wall design. The LCA results showed reduced environmental impacts across some impact metrics, with a significant reduction in Global Warming Potential for the MT LFRS when accounting for biogenic carbon.