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Force Modification Factors for Cross Laminated Timber Buildings

https://research.thinkwood.com/en/permalink/catalogue363
Year of Publication
2012
Topic
Seismic
Market and Adoption
Material
CLT (Cross-Laminated Timber)
Application
Wood Building Systems
Author
Pei, Shiling
Popovski, Marjan
van de Lindt, John
Organization
FPInnovations
Year of Publication
2012
Format
Report
Material
CLT (Cross-Laminated Timber)
Application
Wood Building Systems
Topic
Seismic
Market and Adoption
Keywords
Performance-Based Seismic Design
Canada
US
Force Modification Factors
Mid-Rise
Research Status
Complete
Summary
European experience shows that Cross-Laminated Timber (CLT) can be competitive in mid-rise and high-rise buildings. Although this system has not been used to the same extent so far in North America, it can be viable wood structural solution for the shift towards sustainable densification of urban and suburban centers. For these reasons FPInnovations has undertaken a multi-disciplinary project on determining the performance of a typical CLT construction, including quantifying the seismic resistance and force modification factors for CLT buildings in Canada and the US. In this report, a performance-based seismic design (PBSD) of a CLT building was conducted and the seismic response of the CLT building was compared to that of a wood-frame structure tested during the NEESWood project. A suitable force modification factors (R-factors) for CLT mid-rise buildings with different fasteners were recommended for seismic design in Canada and the US. The six-storey NEESWood Capstone building was redesigned as a CLT building using the PBSD procedure developed during the NEESWood project. The results from the quasi-static tests on CLT walls performed at FPInnovations were used as input information for modeling of the main load resisting elements of the structure, the CLT walls. Once the satisfactory design of the CLT mid-rise structure was established through PBSD, a force-based design was developed with varying R-factors and that design was compared to the PBSD result. In this way, suitable R-factors were calibrated so that they can yield equivalent seismic performance of the CLT building when designed using the traditional force-based design methods. Based on the results of this study it is recommended that a value of Rd=2.5 and Ro=1.5 can be assigned for structures with symmetrical floor plans according to NBCC. In the US an R=4.5 can be used for symmetrical CLT structures designed according to ASCE7. These values can be assigned provided that the design values for CLT walls considered (and implemented in the material design standards) are similar to the values determined in this study using the kinematics model developed that includes the influence of the hold-downs in the CLT wall resistance. Design of the CLT building with those R-factors using the equivalent static procedures in the US and Canada will result in the CLT building having similar seismic performance to that of the tested wood-frame NEESWood building, which had only minor non-structural damage during a rare earthquake event.
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Performance Based Design and Force Modification Factors for CLT Structures

https://research.thinkwood.com/en/permalink/catalogue928
Year of Publication
2012
Topic
Seismic
Design and Systems
Material
CLT (Cross-Laminated Timber)
Application
Wood Building Systems
Walls
Author
Pei, Shiling
Popovski, Marjan
van de Lindt, John
Year of Publication
2012
Format
Conference Paper
Material
CLT (Cross-Laminated Timber)
Application
Wood Building Systems
Walls
Topic
Seismic
Design and Systems
Keywords
Quasi-Static Tests
R-factors
Performance-Based Seismic Design
US
Canada
Conference
CIB-W18 Meeting
Research Status
Complete
Notes
August 27-30, 2012, Växjö, Sweden p.293-304
Summary
In this paper, a performance-based seismic design (PBSD) of a CLT building was conducted and the seismic response of the CLT building was compared to that of a wood-frame structure tested during the NEESWood project. The results from the quasi-static tests on CLT walls performed at FPInnovations were used as input information for modelling of the CLT walls, the main lateral load resisting elements of the structure. Once the satisfactory design of the CLT mid-rise structure was established through PBSD, a force-based design was developed with varying R-factors and that design was compared to the PBSD result. In this way, suitable R-factors were calibrated so that they can yield equivalent seismic performance of the CLT building when designed using the traditional force-based design methods. Based on the results of this study it is recommended that a value of Rd=2.5 and Ro=1.5 can be assigned for structures with symmetrical floor plans in the National Building Code of Canada (NBCC). In the US an R=4.3 can be used for symmetrical CLT structures designed according to ASCE 7. These values can be assigned provided that the design values for CLT walls considered (and implemented in the material design standards) are similar to the values determined in this study using the kinematics model developed that includes the influence of the hold-downs in the CLT wall resistance. Design of the CLT building with those R-factors using the equivalent static procedures in the US and Canada will result in the CLT building having similar seismic performance to that of the tested wood-frame NEESWood building, which had only minor non-structural damage during a rare earthquake event.
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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
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
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.
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Progress on the Development of Strong Seismic Resilient Tall CLT Buildings in the Pacific Northwest

https://research.thinkwood.com/en/permalink/catalogue1881
Year of Publication
2014
Topic
Seismic
Material
CLT (Cross-Laminated Timber)
Application
Wood Building Systems
Author
Pei, Shiling
Berman, Jeffrey
Dolan, Daniel
van de Lindt, John
Ricles, James
Sause, Richard
Blomgren, Hans-Erik
Popovski, Marjan
Rammer, Douglas
Year of Publication
2014
Format
Conference Paper
Material
CLT (Cross-Laminated Timber)
Application
Wood Building Systems
Topic
Seismic
Keywords
Tall Wood
Seismic Performance
Resilience-Based Seismic Design
Conference
World Conference on Timber Engineering
Research Status
Complete
Summary
As urban densification occurs in U.S. regions of high seismicity, there is a natural demand for seismically resilient tall buildings that are reliable, economically viable, and can be rapidly constructed. In urban regions on the west coast of the U.S., specifically the Pacific Northwest, there is significant interest in utilizing CLT in 8-20 story residential and commercial buildings due to its appeal as a potential locally sourced, sustainable and economically competitive building material. In this study, results from a multi-disciplinary discussion on the feasibility and challenges in enabling tall CLT building for the U.S. market were summarized. A three-tiered seismic performance expectations that can be implemented for tall CLT buildings was proposed to encourage the adoption of the system at a practical level. A road map for building tall CLT building in the U.S. was developed, together with three innovative conceptual CLT systems that can help reaching resiliency goals. This study is part of an on-going multi-institution research project funded by National Science Foundation.
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Free
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Cross-Laminated Timber for Seismic Regions: Progress and Challenges for Research and Implementation

https://research.thinkwood.com/en/permalink/catalogue162
Year of Publication
2014
Topic
Seismic
Material
CLT (Cross-Laminated Timber)
Application
Shear Walls
Author
Pei, Shiling
van de Lindt, John
Popovski, Marjan
Berman, Jeffrey
Dolan, Daniel
Ricles, James
Sause, Richard
Blomgren, Hans-Erik
Rammer, Douglas
Publisher
American Society of Civil Engineers
Year of Publication
2014
Format
Journal Article
Material
CLT (Cross-Laminated Timber)
Application
Shear Walls
Topic
Seismic
Keywords
Lateral Loads
Prefabrication
US
Research Status
Complete
Series
Journal of Structural Engineering
Summary
Compared to light-frame wood shear walls, it is relatively difficult for panelized CLT shear walls to achieve similar levels of lateral deflection without paying special attention to design details, i.e., connections. A design lacking ductility or energy dissipating mechanism will result in high acceleration amplifications and excessive global overturning demands for multistory buildings, and even more so for tall wood buildings. Although a number of studies have been conducted on CLT shear walls and building assemblies since the 1990s, the wood design community’s understanding of the seismic behavior of panelized CLT systems is still in the learning phase, hence the impetus for this article and the tall CLT building workshop, which will be introduced herein. For example, there has been a recent trend in engineering to improve resiliency, which seeks to design a building system such that it can be restored to normal functionality sooner after an earthquake than previously possible, i.e., it is a resilient system. While various resilient lateral system concepts have been explored for concrete and steel construction, this concept has not yet been realized for multistory CLT systems. This forum article presents a review of past research developments on CLT as a lateral force-resisting system, the current trend toward design and construction of tall buildings with CLT worldwide, and attempts to summarize the societal needs and challenges in developing resilient CLT construction in regions of high seismicity in the United States.
Online Access
Free
Resource Link
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Progress on the Development of Seismic Resilient Tall CLT Buildings in the Pacific Northwest

https://research.thinkwood.com/en/permalink/catalogue178
Year of Publication
2014
Topic
Seismic
Market and Adoption
Material
CLT (Cross-Laminated Timber)
Application
Wood Building Systems
Author
Pei, Shiling
Berman, Jeffrey
Dolan, Daniel
van de Lindt, John
Ricles, James
Sause, Richard
Blomgren, Hans-Erik
Popovski, Marjan
Rammer, Douglas
Year of Publication
2014
Format
Conference Paper
Material
CLT (Cross-Laminated Timber)
Application
Wood Building Systems
Topic
Seismic
Market and Adoption
Keywords
Commercial
High-Rise
Residential
US Market
Economical
Sustainable
Conference
World Conference on Timber Engineering
Research Status
Complete
Notes
August 10-14, 2014, Quebec City, Canada
Summary
As urban densification occurs in U.S. regions of high seismicity, there is a natural demand for seismically resilient tall buildings that are reliable, economically viable, and can be rapidly constructed. In urban regions on the west coast of the U.S., specifically the Pacific Northwest, there is significant interest in utilizing CLT in 8-20 story residential and commercial buildings due to its appeal as a potential locally sourced, sustainable and economically competitive building material. In this study, results from a multi-disciplinary discussion on the feasibility and challenges in enabling tall CLT building for the U.S. market were summarized. A three-tiered seismic performance expectations that can be implemented for tall CLT buildings was proposed to encourage the adoption of the system at a practical level. A road map for building tall CLT building in the U.S. was developed, together with three innovative conceptual CLT systems that can help reaching resiliency goals. This study is part of an on-going multi-institution research project funded by National Science Foundation.
Online Access
Free
Resource Link
Less detail

Ductility Based Force Reduction Factors for Symmetrical Cross-Laminated Timber Structures

https://research.thinkwood.com/en/permalink/catalogue446
Year of Publication
2014
Topic
Mechanical Properties
Seismic
Material
CLT (Cross-Laminated Timber)
Application
Wood Building Systems
Walls
Author
Popovski, Marjan
Pei, Shiling
van de Lindt, John
Karacabeyli, Erol
Organization
European Association of Earthquake Engineering
Year of Publication
2014
Format
Conference Paper
Material
CLT (Cross-Laminated Timber)
Application
Wood Building Systems
Walls
Topic
Mechanical Properties
Seismic
Keywords
Force Modification Factors
Ductility
National Building Code of Canada
Fasteners
Seismic Performance
Conference
Second European Conference on Earthquake Engineering and Seismology
Research Status
Complete
Notes
August 25-29, 2014, Istanbul, Turkey
Summary
Cross-laminated timber (CLT) as a structural system has not been fully introduced in European or North American building codes. One of the most important issues for designers of CLT structures in earthquake prone regions when equivalent static design procedure is used, are the values for the force modification factors (R-factors) for this structural system. Consequently, the objective of this study was to derive suitable ductility-based force modification factors (Rd-factors) for seismic design of CLT buildings for the National Building Code of Canada (NBCC). For that purpose, the six-storey NEESWood Capstone wood-frame building was redesigned as a CLT structure and was used as a reference symmetrical structure for the analyses. The same floor plan was used to develop models for ten and fifteen storey buildings. Non-linear analytical models of the buildings designed with different Rd-factors were developed using the SAPWood computer program. CLT walls were modelled using the output from mechanics models developed in Matlab that were verified against CLT wall tests conducted at FPInnovations. Two design methodologies for determining the CLT wall design resistance (to include and exclude the influence of the hold-downs), were used. To study the effects of fastener behaviour on the R-factors, three different fasteners (16d nails, 4x70mm and 5x90mm screws) used to connect the CLT walls, were used in the analyses. Each of the 3-D building models was subjected to a series of 22 bi-axial input earthquake motions suggested in the FEMA P-695 procedure. Based on the results, the fragility curves were developed for the analysed buildings. Results showed that an Rd-factor of 2.0 is appropriate conservative estimate for the symmetrical CLT buildings studied, for the chosen level of seismic performance.
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Free
Resource Link
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Tall Cross-Laminated Timber Building: Design and Performance Session WW300 Experimental and Modeling Studies on Wood Frame Buildings

https://research.thinkwood.com/en/permalink/catalogue618
Year of Publication
2014
Topic
Design and Systems
Seismic
Material
CLT (Cross-Laminated Timber)
Application
Walls
Wood Building Systems
Author
Dolan, Daniel
Bordry, Vincent
Pei, Shiling
van de Lindt, John
Organization
Structures Congress
Publisher
American Society of Civil Engineers
Year of Publication
2014
Format
Conference Paper
Material
CLT (Cross-Laminated Timber)
Application
Walls
Wood Building Systems
Topic
Design and Systems
Seismic
Keywords
Damping
Multi-Story
Ductility
Cost
Fire Resistance
Conference
Structures Congress 2014
Research Status
Complete
Notes
April 3-5, 2014, Boston, Massachusetts, United States
Summary
Cross-laminated timber (CLT) is widely perceived as the most promising option for building high-rise wood structures due to its structural robustness and good fire resistance. While gravity load design of a tall CLT building is relatively easy to address because all CLT walls can be utilized as bearing walls, design for significant lateral loads (earthquake and wind) can be challenging due to the lack of ductility in current CLT construction methods that utilize wall panels with low aspect ratios (height to length). Keeping the wall panels at high aspect ratios can provide a more ductile response, but it will inevitably increase the material and labor costs associated with the structure. In this study, a solution to this dilemma is proposed by introducing damping and elastic restoring devices in a multi-story CLT building to achieve ductile response, while keeping the integrity of low aspect ratio walls to reduce the cost of construction and improve fire resistance. The design methodology for incorporating the response modification devices is proposed and the performance of the as-designed structure under seismic is evaluated.
Online Access
Payment Required
Resource Link
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Developing Seismic Performance Factors for Cross Laminated Timber in the United States

https://research.thinkwood.com/en/permalink/catalogue124
Year of Publication
2015
Topic
Seismic
Mechanical Properties
Connections
Material
CLT (Cross-Laminated Timber)
Application
Walls
Author
van de Lindt, John
Amini, M. Omar
Rammer, Douglas
Line, Philip
Pei, Shiling
Popovski, Marjan
Organization
Canadian Association for Earthquake Engineering
Year of Publication
2015
Format
Conference Paper
Material
CLT (Cross-Laminated Timber)
Application
Walls
Topic
Seismic
Mechanical Properties
Connections
Keywords
Angle Bracket
Shear Test
Strength
Stiffness
Uplift Test
US
Conference
The 11th Canadian Conference on Earthquake Engineering
Research Status
Complete
Notes
July 21-24, 2015, Victoria, BC, Canada
Summary
This paper presents recent progress in the development of seismic performance factors for cross-laminated timber (CLT) systems in the United States. A brief overview of some of other systematic studies conducted in Europe, North America, and Japan is also provided. The FEMA P695 methodology is briefly described and selected results from connector testing and CLT wall testing are discussed. Shear and uplift tests were performed on generic angle brackets to quantify their behavior. CLT walls with these connectors were then tested investigate the influence of various parameters on wall component performance. The influential factors considered include boundary condition, gravity loading, CLT grade, panel thickness, and panel aspect ratio (height:length). Results indicate that boundary condition and gravity loading have beneficial effect on strength and stiffness of the CLT panels. CLT grade is an important parameter while CLT panel thickness only has a minimal influence on wall behavior. Higher aspect ratio (4:1) panels demonstrated less stiffness but considerably more ductility than the panels with lower aspect ratio (2:1). This paper also provides details on some ongoing efforts including additional tests planned, index buildings from which P-695 archetypes will be extracted, and nonlinear modeling for this project.
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Free
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Energy Consumption Analysis of Multistory Cross-Laminated Timber Residential Buildings: A Comparative Study

https://research.thinkwood.com/en/permalink/catalogue695
Year of Publication
2016
Topic
Energy Performance
Material
CLT (Cross-Laminated Timber)
Application
Wood Building Systems
Author
Khavari, Ali
Pei, Shiling
Tabares-Velasco, Paulo
Publisher
American Society of Civil Engineers
Year of Publication
2016
Format
Journal Article
Material
CLT (Cross-Laminated Timber)
Application
Wood Building Systems
Topic
Energy Performance
Keywords
Energy Consumption
Energy Efficiency
Residential
Sensitivity Analysis
Research Status
Complete
Series
Journal of Architectural Engineering
Summary
Cross-laminated timber (CLT) is a new panelized mass timber product that is suitable for building tall wood buildings (higher than eight stories) because of its structural robustness and superior fire resistance as compared with traditional light-framed wood systems. A number of tall CLT buildings have been constructed around the world in the past decade, and taller projects are being planned. The energy efficiency of this emerging building type was evaluated numerically in this comparative study with the use of a building energy simulation program. A 10-story multiunit residential building model constructed using CLT was simulated and compared with a light-frame metal construction model with the same floor plan. A sensitivity analysis was also conducted to study the impact of different weather profiles, building types, and internal load conditions on building energy consumption performance. It was concluded that CLT generally provides significant improvement on heating energy efficiency as a heavy and air-tight envelope, but its energy performance efficiency can be affected by weather, building size, internal loading, and HVAC control.
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Free
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38 records – page 1 of 4.