This paper describes the structural design of low-rise multi-storey timber buildings using a new and exciting structural system. This system, originally developed for use with pre-cast concrete, combines un-bonded post-tensioning and additional energy dissipaters, providing a recentering capability after the earthquake, while greatly reducing the structural damage. This new structural system can be used in multi-storey buildings, with large structural timber members made from laminated veneer lumber (LVL) or glulam timber, with lateral loads resisted by prestressed timber frames or walls, separately or in combination. A case study of a six storey timber office building in a moderate seismic area is analysed and a virtual design is carried out, allowing investigation of different methods of structural analysis, and development of many construction and connection details for rapid construction. Total building cost is compared to equivalent steel and reinforced concrete options.
This building is a typical one-storey commercial building located in Vancouver, BC. The plan dimensions are 30.5 m x 12.2 m (100’ x 40’), with a building height of 5 m. The walls are wood-based shear walls, with a wood diaphragm roof and a steel moment frame at the storefront. The roof plan is shown in Figure 1. The site is Seismic Class ‘C’. Wind, snow and seismic figures specific to the project location are taken from the current version of the British Columbia Building Code (2012). Roof dead load is assumed to be 1.0 kPa and the wall weight is 0.5 kPa. The weight of non-structural items including mechanical equipment and the storefront façade has not been included in this example for simplicity.
Multi-storey platform cross laminated timber (CLT) structures are becoming progressively desirable for engineers and owners. This is because they offer many significant advantages such as speed of fabrication, ease of construction, and excellent strength to weight ratio. With platform construction, stories are fixed together in a way that each floor bears into load bearing walls, therewith creating a platform for the next level. The latest research findings have shown that CLT platform buildings constructed with traditional fasteners can experience a high level of damage especially in those cases where the walls have adopted hold-down brackets and shear connectors with nails, rivets or screws. Thus, the current construction method for platform CLT structures is less than ideal in terms of damage avoidance. The main objective of this study is to develop a low damage platform timber panelised structural system using a new configuration of slip friction devices in lieu of traditional connectors. A numerical model of such a system is developed for a low rise CLT building and then is subjected to reversed cyclic load simulations in order to investigate its seismic performance. The result of these quasi-static simulations demonstrated that the system maintained the strength through numerous cycles of loading and unloading. In addition to this, the system is capable of absorbing significant amount of energy. The findings of this study demonstrate the proposed concept has the potential to be developed as a low damage seismic solution for CLT platform buildings.
The use of CLT has been increasing the last decade, and a subsequently focus on documentation of the accompanying indoor climate and exposed wooden surfaces on human well-being. This study presents the results of a measurement campaign conducted over one year of a CLT apartment building in Grimstad, Norway. The apartment building consists of three floors with 35 apartments and comply with the Norwegian passive house standard and energy grade A. Measurements of the relative humidity (RH), indoor air temperature and wood moisture content (MC) were performed in the exposed CLT spruce panels in three apartments in two different floors. The results from the three apartments show a relatively small variation in the MC values regardless the residents behavior measured as RH variation through a complete year. Selected periods from a cold period (winter) and a warm period (summer) show the variation in relative humidity (RH) and moisture content in the CLT element. However, results from control measurements showed higher MC values. The gap between the measurements and methods are discussed.
The research aimed to obtain new data to inform opportunities to further improve the thermal efficiency of light-weight, timber framed, small to medium scaled buildings. The principle task of this project was to complete an empirical study assessing the measured thermal performance of mass-timber.
This empirical study, within real buildings, could then be used to corroborate previous published building heating and cooling energy simulations, which had shown significant thermal performance benefit when mass-timber was substituted with standard framed systems, and concrete and clay brick thermal mass systems.
In the evolving world of increased building regulation and an increasing market expectation for low energy homes there is a need to clearly and simply show how the renewable Australian timber resource can be used to provide thermally comfortable housing, whether they be located in the hot and humid climates of the North or the cooler Southern temperate climates.
This thesis explores the challenges and potential of mass timber as a paradigm shifting technology for the building industry through the application of parametric modeling technology to the design of office buildings. By testing building configurations in three zoning envelopes—low-rise suburban, mid-rise urban, and high-rise urban—optimization strategies for mass timber office buildings were developed. Facades and floor slabs were identified as the primary contributors to building cost and environmental impacts and therefore the easiest targets for optimization. The primary method for optimizing facades is replacing curtain wall with solid cross laminated timber (CLT) walls, this method runs counter to developer driven standards of fully glazed facades making short term adoption of this strategy unlikely without major shifts in building developer and owner expectations. Slabs and floor systems can be optimized through the implementation of novel solutions that take advantage of composite action between glulam, CLT, and concrete elements. Additionally, zoning height incentives could be used to make timber construction competitive with steel and concrete systems despite increased floor-to-floor heights. Finally, future research opportunities and needs, both architectural and technical, are identified.
This thesis presents a numerical study of a novel rocking cross-laminated timber (CLT) shear wall system for low- to mid-rise constructions. The system takes advantage of the high in-plane stiffness of CLT coupled with low-yield steel dampers to control the rocking motion of the CLT shear walls during earthquakes. The low-yield steel dampers connected between two rigid CLT wall panels provide the mechanism needed to dissipate the earthquake energy. This concentrates the damage in the dampers, allowing the system to be repaired efficiently after major earthquakes. Numerical models of the CLT shear wall system have been developed using both OpenSees Navigator and ABAQUS software. Models of low-yield steel damper systems were calibrated using available experimental results. With the rigid floor/roof assumption, a simplified OpenSees model of the CLT shear wall system was demonstrated to be effective and reasonably accurate in predicting the response of the system under large excitations. Therefore, it is efficient and reliable to apply the OpenSees model to study the seismic response of CLT shear wall buildings. A case study of a six-storey CLT shear wall building located in Vancouver, Canada was studied; and, detailed parameteric studies were conducted to investigate the influences of the damper type (damper shear strength), number of dampers, damper location, different earthquake records versus target earthquake design response spectrum, and earthquake peak ground acceleration (PGA) on the building response. It was determined that an optimized damper design with comprehensive consideration of these five factors can provide a building with a small roof drift ratio, as well as minor damages on the dampers. Concepts and examples for connection design are also provided.
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