Mass-timber has gained popularity in the construction of mid-rise buildings in the last decade. The innovation of constructing tall buildings with mass-timber can be seen in the student residence at Brock Commons built in 2016 at the University of British Columbia. It is the world’s tallest timber hybrid building with 18 stories and 53 meters’ height above the ground level. 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. The mass-timber superstructure of 17 stories 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, if mass-timber was used for the cores. The motivation for concrete cores was driven by the sole purpose of easier approval procedure. The objective of this thesis was to evaluate the possibility to design the Brock Commons building using mass-timber cores. First, the procedure for the approvals for tall timber buildings by understanding the code compliance for Brock Commons is discussed. Then, the actual building with concrete cores is modeled, with the model being calibrated with the results from the structural engineers of record. These concrete cores are then replaced by the same configuration using Cross Laminated Timber (CLT) cores to investigate the structural feasibility of Brock Commons with a mass-timber core. The results presented herein show that Brock Commons with CLT core having the same dimensions and configuration is unstable under seismic loading for Vancouver, BC, as specified by National Building of Canada 2015. However, when the configuration and thickness of CLT cores are changed, the structure can meet the seismic performance criteria as per the code.
Wood has seen a resurgence recently as a construction material driven by technological advances and a growing concern for the environment. Although an increasing amount of mass timber high-rises are being built all around the world, lack of information and outdated preconceptions are some of the obstacles that are keeping mass timber products from increasing their market share in high-rise construction. Academia and industry leaders must keep track of the progress that is being made and inform the general public as innovation and technological advances continue to take place. In this context, the University of British Columbia has recently completed the construction of the Brock Commons Tallwood House. This 18-story residence building employs two reinforced concrete cores and a mass timber structure composed of cross laminated timber panels, glued-laminated columns, and parallel strand lumber columns. With this, the building is currently the tallest wood building in the world and a testament to the suitability of engineered wood elements for high-rise construction. Aiming to address the lack of information surrounding mass timber high rise construction, this thesis documents the quality assurance (QA) and quality control (QC) practices that were put in place during the delivery of the building. The main objective of this research was to identify and present lessons learned from the application of these QA/QC practices. To do this, various QA/QC practices were identified and analyzed by reviewing the project specifications and other project documents, reviewing recognized industry standards, and interviewing various members of the project team. This study found a series of comprehensive and well-planned QA/QC practices that were put in place by the project team and that were appropriate to comply with the project requirements. This study concluded that most of these practices are replicable and advisable for future projects. The different QA/QC practices that were identified and the lessons learned from their application are presented in this thesis.
In this paper, we discuss the structural design of one of the tallest timber-based hybrid buildings in the world: the 18 storey, 53 meter tall student residence on the campus of the University of British Columbia in Vancouver. The building is of hybrid construction: 17 storeys of mass wood construction on top of one storey of concrete construction. Two concrete cores containing vertical circulation provide the required lateral resistance. The timber system is comprised of cross-laminated timber panels, which are point supported on glued-laminated timber columns and steel connections between levels. In addition to providing more than 400 beds for students, the building will serve as an academic site to monitor and study its structural performance, specifically horizontal building vibration and vertical shrinkage considerations. We present the challenges relating to the approval process of the building and discuss building code compliance issues.
Cross Laminated Timber (CLT, XLAM) is a product extremely well suited for multi-storey buildings because of its versatility. With lengths up to 16 meters and the possibility of extending with mechanical joints or glued connections, widths of up to 2.5 meters depending on manufacturer and thicknesses up to 500 mm, almost any necessary shape can be found on the market today. Developments are still going on rapidly and new possibilities and new applications far from being exhausted. One such new possibility is the use of CLT elements in a combination with a concrete core and structural outriggers in very high buildings, a ´wood-concrete skyscraper. CLT has already been shown to be very efficient in multi-storey buildings up to 10 storeys. In this paper, an analysis is given of how a concrete core and CLT walls can be used to design very tall buildings in the range of up to 150 meters, but for more than 80% made of timber products. Timber can become an alternative in rapidly expanding cities, where there is a need for high apartment buildings. The building layout uses outriggers at certain intervals, integrated tension cables and CLT structural wall elements in the facades. The design makes optimal use of the advantages of light-weight building elements with comparable structural performance as traditional concrete elements. Savings during the erection stage in terms of money and time are highlighted as well as the CO2 emissions of such a building in comparison with concrete. A concept of the building has been analysed for the location of Shanghai according to the Chinese wind load specifications.