The seismic behaviour of wood buildings is often one of their best features. However, despite this inherent advantage, seismic design must be based on the most recent data and techniques; otherwise, substantial structural damage could occur during powerful earthquakes.
The considerable losses sustained during recent large earthquakes have shifted the philosophy of seismic design towards so-called “resilient” or “low damage” structural systems. These innovative systems aim to reduce structural damage, while providing occupants with the same or even a higher degree of safety.
This session will serve as an opportunity to present the work accomplished, share the results and build on recent knowledge and experience.
Moderators: Marjan Popovski (FPInnovations, Canada) & Thomas Catterou (FCBA, France)
Cross-Laminated Timber Rocking Shear Wall with Replaceable Fuses: Validation Through Full-Scale Shake Table Testing
Speaker: Hans-Erik Bloomgren, Katerra, USA
Through collaboration with the NHERI TallWood Project funded by the National Science Foundation in the United States, an alternative non-prestressed cross-laminated timber rocking wall system with replaceable fuse components was developed by Katerra engineers and tested at the outdoor shake table at the University of California San Diego. The objective of this specific design and testing is to prove a concept for a new high-performance seismic lateral system that is easy to modularize and install, and can be rapidly repaired after major earthquakes.
This presentation highlights the results from 13 shaking table tests conducted on the proposed system, including several repairs after major shaking. The test results showed that the structural system was damage-free under service level ground motions, and experienced repairable damage at designated connection locations for design basis earthquakes and maximum considered earthquakes. Overall, the system was able to limit residual drift to an acceptable level and provide a high-load displacement capacity for the building.
How Tall Can We Build Using Mass Timber: A Wind Engineering Perspective
Speaker: Girma Bitsuamlak, Western University, Canada
The past two decades have seen continuing global recognition of tall wood buildings as sustainable alternatives in addressing issues related to urban densification and sprawl. Recent design strategies are using mass timber as the primary construction material for tall buildings.
A structure’s wind response is governed by its aerodynamic features (shape) and dynamic properties (weight, stiffness, and damping), as well as the wind speed and direction (microclimate). The use of mass timber panels to construct the lateral and gravity systems of tall wood buildings results in the buildings being lightweight and usually less stiff than those made from other conventional construction materials. Frequent exposure to wind-induced oscillations can cause discomfort to occupants and lead to deflection-related serviceability problems. In this regard, there has been a long-overdue question among the practising structural engineers and architects as to what height tall wood buildings can go.
To answer this question from a wind engineering perspective, a coordinated research program was launched in January 2016 by the University of Western Ontario, the University of British Columbia, and FPInnovations. The research program includes aerodynamic and aeroelastic investigations on 11 tall wood building model case studies. This talk summarizes the main findings of the research program. Based on the case studies, tall wood buildings exceeding 90 metres in height would require either supplemental damping or “wind bracing” through different hybridization techniques to satisfy the serviceability criteria of the 2015 National Building Code of Canada.
Seismic experiments on reduced scale models based on similitude theory
Speaker: Thomas Catterou, FCBA, France
Mechanical testing on high-rise buildings is often impossible to perform due to the limited dimensions of the testing bed and the high costs involved. Reduced-scale models are needed for static or seismic testing. A similitude law links the parameters of the scale model with the prototype at the real scale. The choice of the most appropriate law is driven by physical experimental constraints and the need for good representation. The formulation of this law is complex because of the inhomogeneity and nonlinearity of wood and connections. The behaviour of the model will change with its scale.
FCBA, the French Institute of Technology for Forest-based and Furniture Sectors, performed seismic testing on a scale model of the Silva tower in 2017. This presentation will summarize the results and conclusion of this study, and cover the ongoing work on making a more accurate similitude law specific to wood structures and the evaluation of uncertainties.
Title to be confirmed
Speaker: Xanier Estrella
At Katerra, Hans-Erik Blomgren is a director of mass timber systems and product development for commercial markets. This includes qualification testing at Washington State University (USA) of the company’s cross-laminated timber product line, which will be manufactured at a new factory in Spokane, WA, starting in 2019. He has led Katerra’s efforts to technically justify new cross-laminated timber panels for code compliant fire, structural, and acoustic use. These efforts include designing and testing advanced cross-laminated timber floor assemblies for vibration and acoustic performance, as well as developing a new ductile seismic CLT shear wall system which was validated in July 2017 on the largest outdoor shake table in the world, at the University of California, San Diego.
Girma Bitsuamlak is a Canadian Research Chair in Wind Engineering at Western University (WU), London, Ontario. He serves as the Director (Research) for both the Boundary Layer Wind Tunnel Laboratory and WindEEE Research Institute, and is the site leader for the SHARCNET computing centre at WU. His team is actively working on modelling microclimate effects to enhance the performance of sustainable buildings and cities in extreme wind conditions (e.g. hurricane and tornado safety). He uses utilize computational fluid dynamics and physical experiments to develop optimal building design methods for wind. Dr. Bitsuamlak has executed aeroelastic analysis of super-tall buildings, such as the Freedom Tower in New York and Burj Khalifa in Dubai. His current research interests include development of performance-based wind design of tall mass-timber buildings. He is a Fellow of the Canadian Society for Civil Engineering (CSCE) and member of the expert panel for wind engineering at the Council on Tall Buildings and Urban Habitat (CTBUH).
Marjan Popovski is Principal Scientist in the Building Systems Group at FPInnovations. He is also an Adjunct Professor at the Department of Wood Science, at the University of British Columbia (UBC), and at the Centre for Integrated Wood Design, at the University of Northern British Columbia. He has 30 years of research and technical experience in the seismic performance of buildings, and is one of the leading researchers in the area of seismic performance of wood structures. He is an author and co-author of over 180 scientific and technical publications, including textbooks chapters, the Canadian Technical Guide for the Design of Tall Wood Buildings, the Canadian and the U.S. CLT Handbooks, and the Canadian Technical Guide for Mid-rise Wood Frame Construction. Mr. Popovski is part of the technical team that is developing the Seismic Design Factors for platform-type CLT buildings in Canada and the U.S. He is a member of the Technical Committee of the Canadian Standard for Engineering Design in Wood (CSAO86) and various Canadian, U.S. and ISO Subcommittees and Task Groups. He also served as a member of the National Building Code of Canada, Standing Committee on Earthquake Design (2009–2014).
Xavier Estrella is a PhD student in the Collaborative Doctoral Research Program (the Pontificia Universidad Católica de Chile and the University of Technology, Sydney). He graduated in Civil Engineering at the Universidad del Azuay, Ecuador, in 2015. His research is related to “Quantification of seismic performance factors for wood frame timber buildings in Chile”, a joint initiative of the Chilean government and private industry to boost timber construction in that country. He was awarded first place in the 2018 Timber Engineering Contest for his work on evaluating the seismic behaviour of mid-height wood frame buildings in seismic countries. His research interests lie in the development of nonlinear models to study the dynamic behaviour of timber buildings, improving structural design guidelines for mid-height wood frame buildings, and the development of wood-based resilient structural systems. His work has contributed to a better understanding of the response of timber buildings during strong subduction earthquakes and developing strategies to improve the cost-benefit balance in seismic design regulations.