To meet the increasing demand for high strength and non-combustible shear wall systems in mid-rise cold-formed steel (CFS) constructions, this paper investigates the seismic performance and design method of an innovative CFS shear wall system with in-frame corrugated steel sheathing based on previous studies. Shear wall and bearing wall specimens with in-frame corrugated steel sheathing are tested under combined lateral and gravity loading. Simplified numerical models of whole archetype buildings are established. The seismic performance evaluation is performed using methodology recommended in FEMA P695 and the seismic performance factors are examined. The test results show that the shear strength of the innovative shear wall is much higher than currently code certified wood-based shear walls in AISI S400. Also, the shear strength of bearing walls is approximately one-third of the shear strength of shear walls, which proves that bearing walls also contribute significant shear resistance in a structure. The seismic performance evaluation results verified that the existing seismic performance factors (R = Cd = 6.5 and [Formula: see text] = 3.0) for CFS shear walls with flat steel sheathings can also be used for the innovative shear wall system. The innovative CFS shear wall system with in-frame corrugated steel sheathing could be employed for mid-rise buildings in areas that are prone to high seismic and wind loads.
The objective of this paper is to present incremental dynamic analysis (IDA) and seismic performance evaluation results for a two‐story cold‐formed steel (CFS)–framed building. The archetype building was designed to current U.S. standards and then subjected to full‐scale shake table tests under the U.S. National Science Foundation Network for Earthquake Engineering Simulation (NEES) program. Test results showed that the building's stiffness and capacity were considerably higher than expected and the building suffered only nonstructural damage even at excitations in excess of Maximum Considered Earthquake levels for a high seismic zone. For the archetype building, three‐dimensional finite element models at different modeling fidelity levels were created using OpenSees. The models are subjected to IDA using the far‐field ground motion records prescribed in Federal Emergency Management Agency (FEMA) P695. Seismic performance quantification following the FEMA P695 procedure shows that if the modeling fidelity only follows the state‐of‐the‐practice, ie, only includes shear walls, unsafe collapse margin ratios are predicted. State‐of‐the‐art models that account for participation from CFS gravity walls and architectural sheathing have overall performance that are consistent with testing, and IDA results indicate acceptable collapse margin ratios, predicated primarily on large system overstrength. Neglecting the lateral force resistance of the gravity system and nonstructural components, as done in current design, renders a safe design in the studied archetype, but largely divorced from actual system behavior. The modeling protocols established here provide a means to analyze a future suite of CFS‐framed archetype buildings for developing further insight on the seismic response modification coefficients for CFS‐framed buildings.
more » « less- NSF-PAR ID:
- 10458271
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Earthquake Engineering & Structural Dynamics
- Volume:
- 49
- Issue:
- 4
- ISSN:
- 0098-8847
- Page Range / eLocation ID:
- p. 394-412
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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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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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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Summary Robust estimation of collapse risk should consider the uncertainty in modeling of structures as well as variability in earthquake ground motions. In this paper, we illustrate incorporation of the uncertainty in structural model parameters in nonlinear dynamic analyses to probabilistically assess story drifts and collapse risk of buildings. Monte Carlo simulations with Latin hypercube sampling are performed on ductile and non‐ductile reinforced concrete building archetypes to quantify the influence of modeling uncertainties and how it is affected by the ductility and collapse modes of the structures. Inclusion of modeling uncertainty is shown to increase the mean annual frequency of collapse by approximately 1.8 times, as compared with analyses neglecting modeling uncertainty, for a high‐seismic site. Modeling uncertainty has a smaller effect on drift demands at levels usually considered in building codes; for the same buildings, modeling uncertainty increases the mean annual frequency of exceeding story drift ratios of 0.03 by 1.2 times. A novel method is introduced to relate drift demands at maximum considered earthquake intensities to collapse safety through a joint distribution of deformation demand and capacity. This framework enables linking seismic performance goals specified in building codes to drift limits and other acceptance criteria. The distributions of drift demand at maximum considered earthquake and capacity of selected archetype structures enable comparisons with the proposed seismic criteria for the next edition (2016) of ASCE 7. Subject to the scope of our study, the proposed drift limits are found to be unconservative, relative to the target collapse safety in ASCE 7. Copyright © 2016 John Wiley & Sons, Ltd.
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