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.
Technical Guide for Evaluation of Seismic Force Resisting Systems and Their Force Modification Factors for Use in the National Building Code of Canada with Concepts Illustrated Using a Cantilevered Wood CLT Shear Wall Example
The objective of this guideline is to provide a simple, systematic, and sufficient procedure for evaluating the performance of Seismic Force Resisting Systems (SFRSs) and to determine the appropriate ductilityrelated (Rd) and over-strength related (Ro) force modification factors for implementation in the National Building Code of Canada (NBC). The procedure relies on the application of non-linear dynamic analysis for quantification of the seismic performance of the SFRS. Note that the procedure is also suitable for assessing force modification factors (RdRo values) of systems already implemented in the NBC.
The audience for this guideline are those (called the “project study team” in this document) who submit proposals for new SFRSs with defined RdRo values to the NBC for inclusion in Subsection 4.1.8., Earthquake Loads and Effects, of Division B of the NBC. This guideline can also be used by a team performing an alternative design solution for a specific project and seeking acceptance from authority having jurisdiction. In such cases, not all aspects of this guideline (e.g., having different archetypes) will be needed.
Second European Conference on Earthquake Engineering and Seismology
August 25-29, 2014, Istanbul, Turkey
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.
In this paper, to supplement the Canadian building code for a timber-steel hybrid structure, over-strength, and ductility-related force modification factors are developed and validated using a collapse risk assessment approach. The hybrid structure incorporates cross-laminated timber (CLT) infill walls within steel moment resisting frames. Following the FEMA P695 procedure, archetype buildings of 3-story, 6-story, and 9-story height with middle bay infilled with CLT were developed. Subsequently, a nonlinear static pushover analysis was performed to quantify the actual over-strength factors of the hybrid archetype buildings. To check the FEMA P695 acceptable collapse probabilities and adjusted collapse margin ratios (ACMRs), incremental dynamic analysis was carried out using 60 ground motion records that were selected to regional seismic hazard characteristics in southwestern British Columbia, Canada. Considering the total system uncertainty, comparison of the calculated ACMRs with the FEMA P695 requirement indicates the acceptability of the proposed over-strength and ductility factors
In this paper, over-strength and ductility-related force modification factors are developed and validated using a collapse risk assessment approach for a timber-steel hybrid structure. The hybrid structure incorporates Cross Laminated Timber (CLT) infill walls within steel moment resisting frames. Following the FEMA P695 procedure...
Cross-Laminated Timber (CLT), has increased the possibilities of building with wood. CLT consists of multi-layer panels, manufactured with lumber boards that are glued together, alternating the direction of their fibers for each layer. The successful introduction of CLT into the Canadian market indicates that there is potential for further market penetration in North America, and more specifically the United States. To increase the understanding of the market potential for CLT in the U.S., this dissertation aimed at identifying the critical factors influencing the willingness of U.S. construction professionals to adopt innovative wood-based construction materials, such as CLT. The overall objective was achieved by: (a) investigating the level of awareness, perceptions, and willingness to adopt CLT among structural engineers and construction firms; (b) developing a conceptual model including the most critical factors that influence the adoption of innovate wood-based construction materials among structural engineers and construction firms; and (c) identifying distinct market segments for CLT adoption in the U.S. The outcomes from this research help fill the gap in the knowledge about the market adoption process for innovative wood-based materials in the construction industry. This study also contributes to advance the development of the CLT industry in the U.S. by increasing the demand of wood-based construction materials and supporting the creation of employment in a sector of critical importance to the U.S. economy. Findings from this thesis provide useful information that will help these actors accelerate the adoption of CLT through well-designed educational programs, demonstration projects, marketing strategies, and policy incentives.
This research was conducted to discover how the U.S. building construction and forest products sectors could benefit from the development of tall, cross-laminated (CLT) and mass timber buildings. Barriers that may restrict such development were also investigated. The primary benefits were discovered to be eco-performance and job creation. Code restrictions and material performance misconceptions were found to be the largest obstacles. Case studies of Treet, Tamedia, and the WIDC were conducted to demonstrate the benefits of tall wood buildings and the various paths around potential barriers. Opportunities for tall wood buildings in the U.S. are also discussed. This research discovered that a tall wood movement is gathering momentum in the U.S. To fully realize this potential, accurate information regarding the use of wood and the performance capacities of mass timber systems needs to be disseminated. Co-operation between academia and industry will also be necessary.
A collaborative project between the Forest Products Laboratory and Colorado State University to develop seismic performance factors for cross laminated timber is underway. The project requires application of the FEMA P-695 methodology, which is purposely robust and detailed and requires that the project team follow specific procedures. Failure to develop these seismic performance factors would severely limit the acceptance of the CLT building systems in the United States, underscoring the need for application of the FEMA P-695. The FEMA P-695 document, “Quantification of Building Seismic Performance Factors,” was published in 2009 and defines a number of steps, all of which will be taken to develop the seismic performance factors for seismic design of CLT buildings.
The objectives of this research are (1) to develop seismic performance factors for CLT subject to a peer review panel process that includes an independent peer review committee report and (2) to have the resulting seismic performance factors recognized in ASCE 7 Minimum Design Loads for Buildings and Other Structures.
Using the subject of material culture as a lens through which Japanese urban architectural history and political debates are brought into sharper relief, this thesis argues that manufactured engineered wood products like cross laminated timber (CLT) are a part of the larger ongoing discussion on how to solve urban problems and offer the ability to connect sustainable and resilient building design agendas in cities. In addition, if CLT and other wood-based materials are domestically grown and responsibly manufactured on a larger scale than exists presently in Japan, industrial productivity of wood from local forests will recover after long periods of stagnant development, a move heavily invested by the present Prime Minister Shinzo Abe and his administration.