Mass-timber is an emerging building technology created by using structural adhesives to laminate layers of dimensional lumber together to create large ‘timber’ panels. These panels can be used as structural building elements in floors and walls. However, due to relatively large stiffness-to-mass ratios and low inherent damping, optimized timber floors can be vibration controlled even at spans of 3 m. There are several current North American vibration standards that can be applied to timber floors. The goal of this research is twofold: (1) investigate floor performance under various North American vibration criteria for various boundary conditions and (2) address general methods of optimizing floor performance. The impact of support compliance for CLT floors is presented in span-to-depth and span-to-frequency charts intended to assist practitioners with preliminary floor design. The results indicate that existing evaluation methods provide wide-ranging and sometimes conflicting results. However, for all criteria surveyed, it is shown that increasing rotational restraint results in up to 35% thinner floor panels.

It is seemingly inevitable that one day humans will land on the surface of Mars. Between the Apollo lunar missions, International Space Station, and Martian rovers and landers, much of the technology required to transport astronauts to Mars already exists; however, how those humans will live and sustain themselves on the Martian surface is yet to be clearly defined. Since at least the 1980s, researchers have envisioned what a Martian habitat may look like and what its inhabitants will require. Spanning from domed cities to lava tube shelters, the bases of conceived designs are vast. Through NASA's 3D-Printed Habitat Challenge, the American space agency has put large-scale 3D-printing technology at the forefront of this endeavor. This paper presents the rationale for the Martian habitat designed by Northwestern University, in partnership with Skidmore, Owings and Merrill, for submission in NASA's 3D-Printing Habitat Challenge Virtual Design Levels. The habitat includes housing for four astronauts, room for one year of supplies, 93 m(2) living space, and various prescribed volumes of equipment, to name a few. Defined by a unique outer-parabolic and inner-hemispherical shell, the proposed habitat takes a 3D-printing-centered approach for its architecture and fabrication. (C) 2021 American Society of Civil Engineers.

Extreme environmental conditions, unusual loadings, and most importantly, the availability of novel construction techniques will likely dictate the form of any extraterrestrial habitat built on Mars. While a habitat could be constructed by astronauts, it is highly preferred for such a structure to already exist when the first humans land on the Martian surface. Thus, automated structure fabrication equipped with 3D-printing technologies that use in situ resources is an intriguing approach to consider. This paper presents an overview of the design and analysis of a dome-shaped Martian habitat that was designed at Northwestern University in collaboration with Skidmore, Owings & Merrill (SOM) as part of NASA's 3D-Printed Habitat Challenge. The structure has a novel composite hemispheric-parabolic dome that is optimized to sustain self-weight and environmental loads, and to be 3D-printed on an inflatable pressure vessel with Marscrete, a Martian concrete manufactured primarily with local Martian regolith and sulfur. This study examines the structural performance of such a habitat under expected Martian loading conditions, including wind, regolith deposition from storms, and gravity. Furthermore, the habitat performance is assessed under meteorite impact of varying masses and velocities. Finally, a construction scheme, potential internal layout, and functional usability of spaces are also envisioned for a four people unit.

Mass-timber provides numerous benefits in reducing structural material impact on the environment by limiting building embodied carbon. Mass timber from sustainably harvested farms is a renewable material and considered a sink from wood carbon sequestration, and the reduced weight of mass timber framed buildings results in less lateral system and foundation materials.Timber’s limited ductility and traditional connections limit applications in high-seismic regions, but a series of novel connections can reliably provide ductility by using friction to dissipate energy, protecting timber elements as they remain essentially elastic. The bolted connections are designed to be easily replaceable after an earthquake and can re-center the building under any residual drift. In these systems, the seemingly incompatible concepts of resilient and sustainable design can be achieved concurrently, using a renewable material for the base material and connections which specifically target faster recovery times.The Pin-Fuse® Joint and Link-Fuse™ Joint systems, used in moment resisting timber frames and cross- laminated timber shear walls systems, rely on slipping of pre-tensioned bolts across friction surfaces to simulate material yielding. This paper will review the theory behind the systems, application of the devices in timber structures, and compare enhanced seismic design to conventional design timber buildings.

Previous tests of structural walls have routinely used continuous reinforcement extending from the foundation to the top of the specimen. This detailing is consistently different from that of multistory walls in the field, which incorporate splices in the wall longitudinal reinforcement above the wall-foundation interface. As a result, the performance of walls incorporating continuous reinforcement in the laboratory may not be representative of walls in the field that use lap splices or mechanical couplers near the wall base. This paper investigates lateral load behavior of three nominally identical structural walls with continuous reinforcement, lap splices, and mechanical couplers in the plastic hinge region, and quantifies the differences in their responses using force-displacement response, lateral deformation components, and energy dissipation estimated using equivalent viscous damping. (C) 2013 American Society of Civil Engineers.

A collaborative research project is underway at the University of Minnesota Multi-Axial Subassemblage Testing (MAST) Laboratory regarding the behavior of structural wall systems. The investigation included tests and numerical simulations of three rectangular reinforced concrete wall systems to investigate the effect of continuous, spliced, and mechanically connected longitudinal reinforcement at the wall-foundation interface. It was anticipated that the different reinforcement details would have an effect on the plastic hinge length, local strain demands, and consequent flexural (deformation) response including the damage state of the wall systems. The walls were instrumented to investigate the overall behavior and to isolate the individual deformation components attributed to flexure and shear. Understanding the sources of deformation and correlation of the results with models that can be used to predict the behavior is important for development of performance-based seismic design procedures. The project was funded by the National Science Foundation (NSF) grants CMS0324504 and CMS0324559. BACKGROUND