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11 records – page 1 of 2.

Braced Frame System for Timber Buildings

https://research.thinkwood.com/en/permalink/catalogue2527
Year of Publication
2020
Topic
Design and Systems
Seismic
Material
Glulam (Glue-Laminated Timber)
Application
Hybrid Building Systems
Frames
Author
Iqbal, Asif
Organization
University of Northern British Columbia
Year of Publication
2020
Format
Report
Material
Glulam (Glue-Laminated Timber)
Application
Hybrid Building Systems
Frames
Topic
Design and Systems
Seismic
Keywords
Lateral Load Resisting Systems
Sustainability
Post-Tensioned
Connections
Braced Frame Model
Timber-Steel Hybrid
Research Status
Complete
Summary
Advanced sustainable lateral load resisting systems that combine ductile and recyclable materials offer a viable solution to resist seismic load effects in environmentally responsible ways. This paper presents the seismic response of a post-tensioned timber-steel hybrid braced frame. This hybrid system combines glulam frame with steel braces to improve lateral stiffness while providing self-centreing capability under seismic loads. The proposed system is first presented. A detailed numerical model of the proposed system is then developed with emphasis on the connections and inelastic response of bracing members. Various types of braced frames including diagonal, cross and chevron configurations are numerically examined to assess the viability of the proposed concept and to confirm the efficiency of the system. A summary of initial findings is presented to demonstrate usefulness of the hybrid system. The results demonstrate that the proposed system increases overall lateral stiffness and ductility while still being able to achieve self-centring. Some additional information on connection details are provided for implementation in practical structures. The braced-frame solution is expected to widen options for lateral load resisting systems for mid-to-high-rise buildings.
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Combination of Steel Plate Shear Walls and Timber Moment Frames for Improved Seismic Performance

https://research.thinkwood.com/en/permalink/catalogue2735
Year of Publication
2020
Topic
Seismic
Material
CLT (Cross-Laminated Timber)
Application
Shear Walls
Frames
Author
Iqbal, Asif
Todorov, Borislav
Billah, Muntasir
Year of Publication
2020
Format
Conference Paper
Material
CLT (Cross-Laminated Timber)
Application
Shear Walls
Frames
Topic
Seismic
Keywords
Timber Moment Frames
Steel Plate Shear Walls
Hybrid
Seismic Performance
Interstory Drifts
Conference
World Conference on Earthquake Engineering
Research Status
Complete
Summary
Recent interests in adopting sustainable materials and developments in construction technology have created a trend of aiming for greater heights with timber buildings. With the increased height these buildings are subjected to higher level of lateral load demand. A common and efficient way to increase capacity is to use shearwalls, which can resist significant part of the load on the structures. Prefabricated mass timber panels such as those made of Cross-Laminated Timber (CLT) can be used to form the shearwalls. But due to relatively low stiffness value of timber it is often difficult to keep the maximum drifts within acceptable limit prescribed by building codes. It becomes necessary to either increase wall sizes to beyond available panel dimensions or use multiple or groups of walls spread over different locations over the floor plan. Both of the options are problematic from the economic and functional point of view. One possible alternative is to adopt a Hybrid system, using Steel Plate Shear Walls (SPSW) with timber moment frames. The SPSW has much higher stiffness and combined with timber frames it can reduce overall building drifts significantly. Frames with prefabricated timber members have considerable lateral load capacity. For structures located in seismic regions the system possesses excellent energy dissipation ability with combination of ductile SPSW and yielding elements within the frames. This paper investigates combination of SPSW with timber frames for seismic applications. Numerical model of the system has been developed to examine the interaction between the frames and shear walls under extreme lateral load conditions. Arrangements of different geometries of frames and shear walls are evaluated to determine their compatibility and efficiency in sharing lateral loads. Recommendations are presented for optimum solutions as well as practical limits of applications.
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Developments in Tall Wood and Hybrid Buildings and Environmental Impacts

https://research.thinkwood.com/en/permalink/catalogue3005
Year of Publication
2021
Topic
Environmental Impact
Application
Wood Building Systems
Hybrid Building Systems
Author
Iqbal, Asif
Organization
University of Northern British Columbia
Editor
Gupta, Rishi
Publisher
MDPI
Year of Publication
2021
Format
Journal Article
Application
Wood Building Systems
Hybrid Building Systems
Topic
Environmental Impact
Keywords
Tall Wood Buildings
Hybrid Structures
Sustainable Construction
Research Status
Complete
Series
Sustainability
Summary
Wood has been gaining popularity as a building material over the last few decades. There has been significant progress in technology during this period to push the limits of wood construction. At the same time, it has become more economically competitive to build with wood beyond low-rises. As a result, there has been a noteworthy shift in public perception in terms of acceptance of wood as a material for high-rise buildings. There is a growing list of tall wood buildings that have been constructed in different continents over the last decade. With worldwide population growth and increased urbanization, the trend is expected to continue. Considerable urgency for using sustainable resources to tackle the threat of climate change has resulted in a surge in demand as well as applications in recent decades. This paper reviews the significant technical advances that have contributed to those achievements and are expected to facilitate further developments.
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Feasibility of Cross-Laminated Timber Cores for the UBC Tall Wood Building

https://research.thinkwood.com/en/permalink/catalogue1905
Year of Publication
2018
Topic
Design and Systems
Material
CLT (Cross-Laminated Timber)
Application
Shafts and Chases
Author
Connolly, Thomas
Moudgil, Manu
Loss, Christiano
Iqbal, Asif
Tannert, Thomas
Year of Publication
2018
Format
Conference Paper
Material
CLT (Cross-Laminated Timber)
Application
Shafts and Chases
Topic
Design and Systems
Keywords
Brock Commons
Hybrid
Environmental Footprint
Seismic Performance
Conference
World Conference on Timber Engineering
Research Status
Complete
Notes
August 20-23,2018. Seoul, Republic of Korea
Summary
The innovation in tall mass-timber buildings is illustrated by the Brock Commons student residence at the University of British Columbia also known as the UBC Tall Wood Building. It is amongst the world’s tallest timber hybrid building with 18 stories and 53 meters’ height. The building has 17 stories of mass-timber superstructure resting on a concrete podium with two concrete cores that act as a lateral force resisting system for earthquake and wind forces. Construction of the mass-timber superstructure took ten weeks whereas the concrete cores were built in fourteen weeks. There could have been a substantial reduction in the project timeline leading to cost savings, as well as a further reduction of environmental footprint if mass-timber had been used for the cores. The objective of this work was to evaluate the possibility to design the UBC Tall Wood Building using mass-timber cores. A validated numerical model was used to study the feasibility of replacing the concrete cores by cores made of Cross Laminated Timber (CLT). The results presented herein show that, with adjustments in the configuration, the structure can meet the seismic performance criteria as per the Canadian code with CLT cores.
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Feasibility Study of Mass-Timber Cores for the UBC Tall Wood Building

https://research.thinkwood.com/en/permalink/catalogue1895
Year of Publication
2018
Topic
Design and Systems
Environmental Impact
Seismic
Wind
Material
LVL (Laminated Veneer Lumber)
Application
Shafts and Chases
Author
Connolly, Thomas
Loss, Cristiano
Iqbal, Asif
Tannert, Thomas
Publisher
MDPI
Year of Publication
2018
Format
Journal Article
Material
LVL (Laminated Veneer Lumber)
Application
Shafts and Chases
Topic
Design and Systems
Environmental Impact
Seismic
Wind
Keywords
Student Residence
Inter-Storey Drift
Environmental Footprint
Building Codes
Research Status
Complete
Series
Buildings
Summary
The UBC Brock Commons building in Vancouver, which comprises of 18 stories and stands 53 m in height, was at the time of completion in 2016 the world’s tallest hybrid wood-based building. The building’s 17 stories of mass-timber superstructure, carrying all gravity loads, rest on a concrete podium with two concrete cores that act as both the wind and seismic lateral load-resisting systems. Whereas the construction of the concrete cores took fourteen weeks in time, the mass-timber superstructure took only ten weeks from initiation to completion. A substantial reduction in the project timeline could have been achieved if mass-timber had been used for the cores, leading to a further reduction of the building’s environmental footprint and potential cost savings. The objective of this research was to evaluate the possibility of designing the UBC Brock Commons building using mass-timber cores. The results from a validated numerical structural model indicate that applying a series of structural adjustments, that is, configuration and thickness of cores, solutions with mass-timber cores can meet the seismic and wind performance criteria as per the current National Building Code of Canada. Specifically, the findings suggest the adoption of laminated-veneer lumber cores with supplementary ‘C-shaped’ walls to reduce torsion and optimize section’s mechanical properties. Furthermore, a life cycle analysis showed the environmental benefit of these all-wood solutions.
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Mass Timber Rocking Panel Retrofit of a Four-Story Soft-Story Building with Full-Scale Shake Table Validation

https://research.thinkwood.com/en/permalink/catalogue833
Year of Publication
2017
Topic
Seismic
Material
CLT (Cross-Laminated Timber)
Light Frame (Lumber+Panels)
Application
Wood Building Systems
Author
Bahmani, Pouria
van de Lindt, John
Iqbal, Asif
Rammer, Douglas
Publisher
MDPI
Year of Publication
2017
Format
Journal Article
Material
CLT (Cross-Laminated Timber)
Light Frame (Lumber+Panels)
Application
Wood Building Systems
Topic
Seismic
Keywords
FEMA
Full Scale
Retrofit
Seismic
Shake Table Test
Soft-Story
US
Research Status
Complete
Series
Buildings
Summary
Soft-story wood-frame buildings have been recognized as a disaster preparedness problem for decades. There are tens of thousands of these multi-family three- and four-story structures throughout California and other cities in the United States. The majority were constructed between 1920 and 1970, with many being prevalent in the San Francisco Bay Area in California. The NEES-Soft project was a five-university multi-industry effort that culminated in a series of full-scale soft-story wood-frame building tests to validate retrofit philosophies proposed by (1) the Federal Emergency Management Agency (FEMA) P-807 guidelines and (2) a performance-based seismic retrofit (PBSR) approach developed within the project. Four different retrofit designs were developed and validated at full-scale, each with specified performance objectives, which were typically not the same. This paper focuses on the retrofit design using cross laminated timber (CLT) rocking panels and presents the experimental results of the full-scale shake table test of a four-story 370 m2 (4000 ft2) soft-story test building with that FEMA P-807 focused retrofit in place. The building was subjected to the 1989 Loma Prieta and 1992 Cape Mendocino ground motions scaled to 5% damped spectral accelerations ranging from 0.2 to 0.9 g.
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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
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
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.
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Performance and Design of LVL Walls Coupled with UFP Dissipaters

https://research.thinkwood.com/en/permalink/catalogue195
Year of Publication
2014
Topic
Seismic
Material
LVL (Laminated Veneer Lumber)
Application
Shear Walls
Author
Iqbal, Asif
Pampanin, Stefano
Palermo, Alessandro
Buchanan, Andrew
Publisher
Taylor&Francis Online
Year of Publication
2014
Format
Journal Article
Material
LVL (Laminated Veneer Lumber)
Application
Shear Walls
Topic
Seismic
Keywords
Cyclic
Energy Dissipation
Multi-Storey
Post-Tensioned
U-Shaped Flexural Plates
Quasi-Static
Pseudo-dynamic
Research Status
Complete
Series
Journal of Earthquake Engineering
Notes
http://dx.doi.org/10.1080/13632469.2014.987406
Summary
This article presents recent research on the seismic resistance of coupled post-tensioned timber walls for use in multi-story buildings. The walls are constructed from laminated veneer lumber (LVL), post-tensioned with unbonded vertical tendons, and coupled together with mild steel U-shaped flexural plates (UFPs) as energy dissipating elements. The timber wall design follows the same principles as used for post-tensioned precast concrete wall systems, using U-shaped plates to obtain a “hybrid” system, where energy is dissipated through yielding of the plates, while the vertical post-tensioning provides the restoring force. In this project, the same principles are applied to timber coupled walls. A series of quasi-static cyclic and pseudo-dynamic tests have been carried out to verify the applicability of the concept and the feasibility of the construction technology in timber buildings. The U-shaped plates showed stable energy dissipation characteristics and, in combination with the post-tensioning, desirable re-centering hysteretic behavior typically referred to as “flag-shape”. Because of the simplicity of these elements and the low cost of implementation, they have good prospects for practical application.
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Post-Tensioned Mass Timber Systems

https://research.thinkwood.com/en/permalink/catalogue1256
Year of Publication
2017
Topic
Design and Systems
Seismic
Application
Frames
Shear Walls
Author
Iqbal, Asif
Popovski, Marjan
Organization
Structures Congress
Publisher
American Society of Civil Engineers
Year of Publication
2017
Format
Conference Paper
Application
Frames
Shear Walls
Topic
Design and Systems
Seismic
Keywords
North America
New Zealand
Post-Tensioning Cables
Post-Tensioned
Multi-Story
Lateral Load Resisting Systems
High Seismic Regions
Conference
Structures Congress 2017
Research Status
Complete
Notes
April 6–8, 2017, Denver, Colorado
Summary
A new type of mass timber structural system has been developed in New Zealand over the last decade. Timber members made of engineered wood products are used in combination with post-tensioning cables to produce highly efficient structural components suitable for multi-story moment resisting frames or shear wall-based lateral load resisting systems. Both systems are particularly useful in structures designed in high seismic regions. The post-tensioning also ensures self-centering of the components and the structural systems after a seismic event. In addition to the post-tensioning, the systems can use energy dissipating devices within the connections that further enhance the ductility of the systems and make them good candidates for low damage structural applications. Extensive experimental and numerical studies have been conducted to determine the performance of these systems and design procedures have been developed for practical applications. In an effort to bring this system closer to the North American designers, this paper contains a summary of the evolution of the concept and the most important research projects and findings to date. In addition, a number of applications within and outside New Zealand are reviewed to demonstrate the applicability of the concept. Finally, potential and recent initiatives for adoption of the technology in North America are discussed.
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Response of Plywood-Coupled Post-Tensioned LVL Walls to Repeated Seismic Loading

https://research.thinkwood.com/en/permalink/catalogue1583
Year of Publication
2016
Topic
Connections
Mechanical Properties
Seismic
Material
LVL (Laminated Veneer Lumber)
Application
Walls
Author
Iqbal, Asif
Pampanin, Stefano
Fragiacomo, Massimo
Buchanan, Andrew
Year of Publication
2016
Format
Conference Paper
Material
LVL (Laminated Veneer Lumber)
Application
Walls
Topic
Connections
Mechanical Properties
Seismic
Keywords
Post-Tensioned
Quasi-Static
Cyclic Testing
Energy Dissipation
Nails
Cyclic Loading
Conference
World Conference on Timber Engineering
Research Status
Complete
Notes
August 22-25, 2016, Vienna, Austria p. 1807-1813
Summary
Laminated veneer lumber (LVL) structural members have recently been proposed for multi-storey timber buildings based on ongoing research at University of Canterbury, New Zealand. The members are designed with unbonded post-tensioning for recentering and energy dissipation through the ductile connections. This paper describes the experimental and numerical investigation of post-tensioned LVL walls coupled with plywood sheets, under quasistatic cyclic testing protocols. It is observed that energy is dissipated mostly through yielding of the nails, and the LVL walls return close to their initial position while remaining virtually undamaged. The same specimen has been tested under repeated cyclic loading to investigate the performance of the arrangement under more than one seismic event (a major earthquake followed by a significant aftershock). Different nail spacing and arrangements have been tested to compare their energy dissipation characteristics. The results indicate good seismic performance, characterized by negligible damage of the structural members and very small residual deformations. The only component significantly damaged is the nailed connection between the plywood sheet and the LVL walls. Although the nails yield and there is a reduction in stiffness the system exhibits a stable performance without any major degradation throughout the loading regime. The plywood can be easily removed and replaced with new sheets after an earthquake, which are reasonably cheap and easy to install, allowing for major reduction in downtime. With these additional benefits the concept has potential for consideration as an alternative solution for multi-storey timber buildings.
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11 records – page 1 of 2.