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Driven by demand for sustainable buildings and a reduction in construction time, mass timber buildings, specifically cross-laminated timber (CLT), is being more widely used in mid-rise buildings in the US. Low damage post-tensioned self-centering (SC) CLT shear walls (SC-CLT walls) provide an opportunity to develop seismically resilient CLT buildings. Previous research focused primarily on the lateral-load response under unidirectional loading of isolated self-centering timber walls, without considering the interaction with the adjacent building structural components, i.e., the floor diaphragms, collector beams, and gravity load system. Buildings response under seismic loading is multidirectional and there are concerns that multidirectional loading may be more damaging to SC-CLT wall panels and the adjacent building structural components than unidirectional loading, which affects the potential seismic resilience of buildings with SC-CLT walls. A series of lateral-load tests of a 0.625-scale timber sub-assembly was conducted at the NHERI Lehigh Large-Scale Multi-Directional Hybrid Simulation Experimental Facility to investigate the the lateral-load response and damage of SC-CLT walls and the capability of the adjacent building structural components i.e., the floor diaphragms, collector beams, and gravity load system to accommodate the building response and the controlled-rocking of the SC-CLT walls under multidirectional lateral loading.
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Physical damage‐hysteretic response correlation for steel sheet sheathed cold‐formed steel‐framed wall‐lines
Abstract Use of cold‐formed steel (CFS) framing as load‐bearing system for gravity and lateral loads in buildings is becoming increasingly common in the North American construction industry, notably in high seismic regions where light‐weight construction is an attractive option. Buildings framed with closely spaced and repetitively placed CFS members can be detailed to develop lateral resistance using a variety of sheathing options. A relatively new option involves the use of steel sheet as sheathing. Steel sheet sheathed CFS shear walls offer high lateral strength and stiffness, and provide ductility courtesy of tension field action within the steel sheet. Despite their acceptance, gaps in the understanding of their behavior do exist, notably, behavior under dynamic loading, the contribution of nonstructural architectural finishes, and the behavior of wall‐lines: shear walls placed inline with gravity walls. To this end, a two‐phased experimental effort was undertaken to advance understanding of the lateral response of CFS‐framed wall‐line systems. Specifically, a suite of wall‐lines, detailed for mid‐rise buildings, were evaluated through simulated seismic loading imposed via shake table and quasi‐static cyclic tests. Damage to the wall‐lines was largely manifested in the form of damage to fastener connections used for attaching the sheathing and gypsum panels, and separation of exterior finish layer. This paper documents and quantifies the progressively incurred physical damage observed in the tested wall‐line assemblies, and correlates it with the evolution of dynamic characteristics and hysteretic energy dissipated across a spectrum of performance levels.
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- Award ID(s):
- 1663348
- PAR ID:
- 10481982
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Earthquake Engineering & Structural Dynamics
- Volume:
- 53
- Issue:
- 3
- ISSN:
- 0098-8847
- Format(s):
- Medium: X Size: p. 1195-1215
- Size(s):
- p. 1195-1215
- Sponsoring Org:
- National Science Foundation
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Driven by demand for sustainable buildings and reduction in construction time, mass timber, specifically cross-laminated timber (CLT), is being more widely used in mid-rise buildings in the US. In areas of the US with a significant seismic (i.e. earthquake) hazard, mass timber buildings that are seismically resilient are of significant interest. Low damage post-tensioned self-centering CLT shear walls (SC-CLT walls) provide an opportunity to develop seismically resilient CLT buildings. There is however insufficient knowledge of the lateral-load response and damage states of SC-CLT walls under multidirectional seismic loading conditions, which can have a pronounce effect on the seismic resilience of buildings with SC-CLT walls. In order to fill this knowledge gap, a series of lateral-load tests were performed at the NHERI Lehigh Large-Scale Multi-directional Hybrid Simulation Experimental Facility to investigate the multidirectional cyclic behavior of a low damage, resilient three-dimensional CLT building sub-assembly with SC-CLT coupled shear walls, CLT floor diaphragm, collector beams, and gravity load system. Comparisons are made between the lateral-load experimental response of the SC-CLT walls under unidirectional and multidirectional cyclic loading.more » « less
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To advance understanding of the multihazard performance of midrise cold-formed steel (CFS) construction, a unique multidisciplinary experimental program was conducted on the Large High-Performance Outdoor Shake Table (LHPOST) at the University of California, San Diego (UCSD). The centerpiece of this project involved earthquake and live fire testing of a full-scale 6-story CFS wall braced building. Initially, the building was subjected to seven earthquake tests of increasing motion intensity, sequentially targeting service, design, and maximum credible earthquake (MCE) demands. Subsequently, live fire tests were conducted on the earthquake-damaged building at two select floors. Finally, for the first time, the test building was subjected to two postfire earthquake tests, including a low-amplitude aftershock and an extreme near-fault target MCE-scaled motion. In addition, low-amplitude white noise and ambient vibration data were collected during construction and seismic testing phases to support identification of the dynamic state of the building system. This paper offers an overview of this unique multihazard test program and presents the system-level structural responses and physical damage features of the test building throughout the earthquake-fire-earthquake test phases, whereas the component-level seismic behavior of the shear walls and seismic design implications of CFS-framed building systems are discussed in a companion paper.more » « less
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Blass, Hans (Ed.)Wood buildings in North American has been predominantly constructed using light-framed wood systems since early 1900’s, with only limited exception of heavy timber construction in some non-residential applications. This situation is likely to change in the future with the growing acceptance of mass timber construction in the region. In fact, a number of mass timber buildings have been constructed in recent years in the U.S. and Canada, including low- to mid-rise mixed-use buildings (e.g. UMass Student Center, T3 building) and tall towers (e.g. Brocks Commons at UBC). Most of these buildings utilized cross laminated timber (CLT) or nail laminated timber (NLT) floors and heavy timber framing systems to support gravity loads, and a non-wood lateral system such as concrete shear walls or a braced steel frame to resist wind and seismic loads. Although CLT material and glulam products have been recognized in the U.S. and Canada (IBC (2018) and NBCC (2015), there is currently no mass timber lateral systems in the U.S. and only one system (platform style panelized CLT shear wall) in Canada that is currently recognized by the building codes. As a result, special design procedures and review/approval processes must be followed for any building intended to use a mass timber lateral system. There is a need to promote codification of mass timber lateral systems in order to help further develop mass timber building market in North American. At the time of this paper, there has been an on-going effort to devel-op seismic design parameters for panelized CLT shear walls in the U.S. (ref) following the FEMA P695 procedure for platform construction. The other lateral system that at-tracted significant attention and research resources is post-tensioned CLT rocking wall system, which has the potential to be applicable to balloon framed low-rise to tall wood buildings. This paper will focus on recent research development on CLT rocking wall system in the U.S. and the effort to develop a seismic design procedure for this system for inclusion in the NDS Special Design Provisions for Wind and Seismic (SPDWS)(2008). While the expensive and time consuming process of the FEMA P695 process would provide the ability to use the equivalent lateral force method for design purposes, this path is not part of the discussion included here.more » « less
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