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Full-Scale Experimental Verification of Soft-Story-Only Retrofits of Wood-Frame Buildings Using Hybrid Testing

https://research.thinkwood.com/en/permalink/catalogue172
Year of Publication
2015
Topic
Seismic
Material
CLT (Cross-Laminated Timber)
Light Frame (Lumber+Panels)
Application
Wood Building Systems
Author
Jennings, Elaina
van de Lindt, John
Ziaei, Ershad
Bahmani, Pouria
Park, Sangki
Shao, Xiaoyun
Pang, Weichiang
Rammer, Douglas
Mochizuki, Gary
Gershfeld, Mikhail
Publisher
Taylor&Francis Online
Year of Publication
2015
Country of Publication
United States
Format
Journal Article
Material
CLT (Cross-Laminated Timber)
Light Frame (Lumber+Panels)
Application
Wood Building Systems
Topic
Seismic
Keywords
Full Scale
Retrofit
Soft-Story
Language
English
Research Status
Complete
Series
Journal of Earthquake Engineering
Notes
https://doi.org/10.1080/13632469.2014.975896
Summary
The FEMA P-807 Guidelines were developed for retrofitting soft-story wood-frame buildings based on existing data, and the method had not been verified through full-scale experimental testing. This article presents two different retrofit designs based directly on the FEMA P-807 Guidelines that were examined at several different seismic intensity levels. The effects of the retrofits on damage to the upper stories were investigated. The results from the hybrid testing verify that designs following the FEMA P-807 Guidelines meet specified performance levels and appear to successfully prevent collapse at significantly higher seismic intensity levels well beyond for which they were designed. Based on the test results presented in this article, it is recommended that the soft-story-only retrofit procedure can be followed when financial or other constraints limit the retrofit from bringing the soft-story building up to current code or applying performance-based procedures.
Online Access
Free
Resource Link
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Observed Performance of Soft-Story Woodframe Building Retrofitted with CLT Rocking Walls

https://research.thinkwood.com/en/permalink/catalogue1002
Year of Publication
2014
Topic
Seismic
Material
CLT (Cross-Laminated Timber)
Light Frame (Lumber+Panels)
Application
Wood Building Systems
Author
van de Lindt, John
Bahmani, Pouria
Mochizuki, Gary
Gershfeld, Mikhail
Iqbal, Asif
Year of Publication
2014
Country of Publication
Canada
Format
Conference Paper
Material
CLT (Cross-Laminated Timber)
Light Frame (Lumber+Panels)
Application
Wood Building Systems
Topic
Seismic
Keywords
Soft-Story
Retrofit
Shake Table Tests
Seismic Resistance
Language
English
Conference
World Conference on Timber Engineering
Research Status
Complete
Notes
August 10-14, 2014, Quebec City, Canada
Summary
Many of the woodframe buildings in United States, particularly along the pacific coast, have more than one story with the first floor used either for parking or commercial space which require large openings and few partition walls at that level. This open space condition results in the earthquake resistance of the first story being significantly lower than the upper stories thus creating first stories that are both “weak” (low strength) and “soft” (low stiffness) in nature. This feature has the potential to allow formation of the soft first story mechanism during earthquakes. The United States National Science Foundation (NSF) – funded NEES-Soft project has been undertaken to develop and validate economical retrofit concepts for these types of buildings. Shake table tests on a four-story full scale model building were performed with different retrofit schemes as part of the experimental investigation. One of the retrofit measures investigated was addition of cross laminated timber rocking walls at the first floor level for increased seismic resistance. This paper focuses on the experimental performance of soft-story buildings retrofitted with cross laminated timber rocking walls. Moderate damage was observed at the first story level of the building while theupper three stories exhibited very little signs of distress. The focus of this paper is to establish correlation between the observed damage and drift. The Cross laminated timber (CLT) rocking walls were designed as per FEMA P-807 guidelines to satisfy the San Francisco mandatory softstory retrofit ordinance requirements. The tests confirmed the efficiency of CLT retrofit with expected levels of drifts throughout the structure.
Online Access
Free
Resource Link
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Performance-Based Seismic Retrofit of Soft-Story Woodframe Buildings

https://research.thinkwood.com/en/permalink/catalogue674
Year of Publication
2014
Topic
Seismic
Application
Wood Building Systems
Author
Bahmani, Pouria
van de Lindt, John
Pryor, Steven
Mochizuki, Gary
Gershfeld, Mikhail
Rammer, Douglas
Tian, Jingjing
Symans, Michael
Publisher
C3 Ink
Year of Publication
2014
Country of Publication
United States
Format
Magazine Article
Application
Wood Building Systems
Topic
Seismic
Keywords
Retrofit
Soft-Story
Performance Based Seismic Retrofit
Shake Table Test
Language
English
Research Status
Complete
Series
STRUCTURE
Summary
This article presents the first generation of Performance-based seismic retrofit (PBSR) and resulting retrofit design using a combination of wood structural panel sheathing and Simpson Strong-Tie® Strong Frame® steel special moment frames. PBSR is essentially the same as performance-based seismic design (PBSD) with the exception of additional constraints on the design due to existing structural and non-structural assemblies. The PBSD method is a design methodology that seeks to ensure that structures meet prescribed performance criteria under seismic loads. In the PBSR, retrofits were installed such that the building meets the performance criteria at the DBE and MCE level and its torsional response reduces to an acceptable range. In this retrofit design methodology, retrofits are not limited to the bottom story (like those of the FEMA P-807 retrofit methodology). They can also be applied to the upper stories to increase the strength of the building, leading to better overall performance of the structure.
Online Access
Free
Resource Link
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Seismic Retrofit of Soft-Story Woodframe Buildings using Cross Laminated Timbers

https://research.thinkwood.com/en/permalink/catalogue215
Year of Publication
2013
Topic
Seismic
Material
CLT (Cross-Laminated Timber)
Light Frame (Lumber+Panels)
Application
Wood Building Systems
Author
van de Lindt, John
Bahmani, Pouria
Gershfeld, Mikhail
Kandukuri, Giraj
Rammer, Douglas
Pei, Shiling
Year of Publication
2013
Country of Publication
United States
Format
Journal Article
Material
CLT (Cross-Laminated Timber)
Light Frame (Lumber+Panels)
Application
Wood Building Systems
Topic
Seismic
Keywords
Retrofit
Soft-Story
Numerical model
US
Full Scale
Language
English
Conference
International Structural Engineering and Construction Conference
Research Status
Complete
Notes
June 18-23 2013, Hononlulu, Hawaii, USA
Summary
Woodframe construction in the United States has, by and large, performed well with regard to life-safety over the decades. However, older woodframe buildings, typically two- to four-stories in Northern and Southern California (as well as elsewhere), may have a soft and weak story which makes them susceptible to collapse during even moderate shaking. These buildings often have parking and/or open fronts and very few interior walls resulting in first story stiffness that is sometimes as low as 30% to 40% of the story above. Figure 1 shows a photo of a soft-story building undergoing retrofit in San Francisco. Most local jurisdictions recognize this as a disaster preparedness problem and have beenactively developing various ordinances and mitigation plans to address this threat. Some of the most visible efforts are taking place in San Francisco, Los Angeles, San Jose and other major metropolitan areas in the United States that have high seismic vulnerability. In 2008, the San Francisco Department of Building Inspection and the Applied Technology Council initiated the Community Action Plan for Seismic Safety (CAPSS) project with the main goal of identifying possible action plans for reducing earthquake risks in existing buildings. According to the CAPSS study, 43 to 80 percent of the multistory woodframe buildings in San Francisco will be deemed unsafe after a magnitude 7.2 earthquake and a quarter of these buildings would be expected to collapse.
Online Access
Free
Resource Link
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