This thesis was initiated by a project planing the world's tallest timber building in Bergen, Norway, (the VHT project). The concept of the building is based on a load baring glulam frame with building modules stacked inside to create the residential area of the building. Calculation done by Sweco showed that more damping was needed to lower the accelerations in the top floor of the building. Since little was known about the dynamic properties of building modules and whether these could be used to increase the damping of the building, a survey was wanted.
In this master thesis the dynamic properties of the building modules have been evaluated. This has been done by preforming dynamic test on building modules similar to those planed for the VHT project. Two test protocols were used to test the modules, an experimental modal analysis method using a modal hammer and a system identification method. The goal of the tests was to identify the modal frequencies, damping ratios and mode shapes of the building modules.The tested modules were modeled in a finite element (FE) method program and scaled to fit the size of the VHT modules. This way the dynamic properties of the VHT modules could be estimated. Simple shear frame models of the VHT modules were made to be implemented in a larger model of the VHT building to evaluate the effect of the modules on the entire structure. Several detailed FE models were made to evaluate how the separate parts of the modules influenced the dynamic response of the modules. An evaluation of the dynamic properties of the sound reducing material Stepisol was also done by dynamic testing in the lab and FE modeling.
It was found that the tested modules had two translational modes and one torsional mode. The overall damping ratio of the modules was found to be roughly 3%. From the numerical tests the stiffness of the module walls were found to be more or less constant per meter wall. The walls can therefor easily be scaled for similar modules with different dimensions to predict the dynamic properties of the new modules.The Stepisol was found to influence the dynamic properties of the stacked building modules severely. The lab tests showed that Stepisol has a high material damping that helps increasing the damping in the modules. The FE models showed that layers of Stepisol makes the stacked modules a lot less stiff and it is a key feature that can be used to alter the dynamic behavior of stacked modules.
Over the past several years, a number of tall wood projects have been completed around the world, demonstrating successful applications of mass timber technologies. A survey of ten tall wood building projects in several countries was undertaken to present some common lessons learned from the experiences of four key stakeholder groups involved in the projects.
The survey was focused on the experiences of each project’s Developer/Owner, Design Team, Authorities Having Jurisdiction (AHJ), and Construction Team. It also examined the topics of project insurance, project financing and building operations and performance.
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.
This study explores the use of Cross Laminated Timber (CLT) in a 10-story residential building as an alternative building method to concrete and steel construction. The study is not meant to be exhaustive, rather a preliminary investigation to test the economic viability of utilizing this new material to increase density, walkability and sustainable responsiveness in our built environment.
Based on international precedent, CLT is an applicable material for low-rise, as well as mid-rise to high-rise construction and has a lighter environmental footprint than traditional concrete and steel construction systems. Cross-laminated timber is a large format solid wood panel building system originating from central Europe. As a construction system it is similar to precast concrete in which large prefabricated panels are lifted by crane and installed using either a balloon frame or platform frame system. The advantages to using CLT are many, but the main benefits include: shorter construction times, fewer skilled laborers, better tolerances and quality, safer work environment, utilization of regional, sustainable materials, and reduction of carbon footprint of buildings. As a new, unproven material in the Pacific Northwest, this study investigates the cost competitiveness of CLT versus traditional materials for “low high-rise” buildings.
Working in collaboration with the Canadian Wood Council and FPInnovations and in partnership with Natural Resources Canada and the governments of Ontario, Quebec and British Columbia, the National Research Council conducted a comprehensive research project, Research Consortium for Wood and Wood-Hybrid Mid-rise Buildings. This consortium project aimed to develop technical information that could be used to support acceptable solutions that meet the NBC’s objectives for fire safety, acoustics, and building envelope performance, in order to facilitate the use of wood-based structural materials in mid-rise buildings. The objectives of the Wood and Wood-Hybrid Midrise Buildings research project were to develop performance data and technical solutions in the areas of fire safety, acoustics and building envelope pertinent to the use of wood-based structural materials in mid-rise buildings, i.e. to develop an alternative solution to meet the 2010 NBC requirements for non-combustible construction for 5-6 storey (and taller) buildings. This project was intended to address the immediate needs for technical solutions for mid-rise wood buildings that do not compromise the minimum levels of safety and performance required by the 2010 NBC in the areas of fire safety and fire protection, acoustics, and building envelope performance.
This paper summarises the experimental and numerical investigation conducted on the main connection of a novel steel-timber hybrid system called FFTT. The component behaviour of the hybrid system was investigated using quasi-static monotonic and reversed cyclic tests. Different steel profiles (wide flange I-sections and hollow rectangular sections) and embedment approaches for the steel profiles (partial and full embedment) were tested. The results demonstrated that when using an appropriate connection layout, the desired strong-column weak-beam failure mechanism was initiated and excessive wood crushing was avoided. A numerical model was developed that reasonably reflected the real component behaviour and can subsequently be used for numerical sensitivity studies and parameter optimization. The research presented herein serves as a precursor for providing design guidance for the FFTT system as an option for tall wood-hybrid buildings in seismic regions.
The advantages of using timber as the primary construction material in mid- and high-rise buildings are undisputed. Timber is sustainable, renewable, and has a very good strength-toweight ratio, which makes it an efficient building material. However, perceived shortcomings with respect to its ductility and system level behavior; along with lack of appropriate design guidance currently limits the use of timber in taller structures. Overcoming these obstacles will allow timber, and its wood product derivatives, to further expand into the multi-storey construction sector - most likely in hybrid-type structures.
The -Finding the Forest Through the Trees (FFTT) system is an innovative timber-steel hybrid system that may allow high-rise timber construction, even in highly seismic regions. The FFTT system utilizes engineered timber products to resist gravity and lateral loads with interconnecting steel members to provide the necessary ductility and predictability for seismic demands.
For a novel hybrid system, such as the FFTT, to gain recognition, experimental data must be gathered and supported by computational modeling and analysis in order to prove its component- and system-level performance. This thesis presents research utilizing nonlinear dynamic analysis of finite element (FE) models of the FFTT system, with properties calibrated to physical component tests, to capture the response under significant wind and seismic loads. From the results presented herein, it appears that the FFTT system can meet the design performance requirements required for seismic loading; however, due to its relatively low weight, may be susceptible to wind induced vibrations. All results are based on Vancouver, BC loading as specified by 2010 the National Building Code of Canada.
April 3-5, 2014, Boston, Massachusetts, United States
The goal of this research was to develop a structural system for tall buildings using mass-timber as the main structural material that reduces the carbon dioxide emissions associated with the structure. The structural system research was applied to a prototypical building based on an existing concrete benchmark for comparison.
This paper discusses key design issues associated with tall mass-timber buildings along with potential solutions. It is believed that the system proposed in the research and discussed in the paper could mitigate many of these design issues. The main structural mass-timber elements are connected by steel reinforcing through cast-in-place concrete at the connection joints. This system plays to the strengths of both materials and allows the designer to apply sound tall building engineering fundamentals. The result is believed to be an efficient structure that could compete with reinforced concrete and structural steel while reducing the associated carbon emissions by 60 to 75%.
A major concern with tall wood buildings is fire during or after an earthquake. Through a survey of factors including reliability of systems, reliability of water supplies, availability of professional and civilian fire fighting, the paper will examine the overall reliability of sprinkler systems in including assessment of the ability untrained fire fighters to suppress fires in a timber high-rise in the absence of professional fire fighters. A probability based fault tree analysis will provide guidance designers of tall wood buildings in providing acceptable fire safety after a seismic event.