Most of the timber used in the Australian built environment is presently for low-rise residential construction. This market share is under constant erosion from competitive systems; therefore, entry into non-traditional sectors would benefit the industry through a wider market portfolio of building type applications, and a higher value product system development.
The project analysed building designs in order to estimate the size and value of the market sector in commercial and high-rise residential buildings; established the major building systems used in these sectors, and why these systems are popular (major attractiveness of current systems) and scoped two current timber systems (Cassette Flooring and Access floors) that have the opportunity to increase timber volumes in these markets.
The number of occupant complaints received about annoying low-frequency footstep impact sound transmission through wood floor-ceiling assemblies has been increasing in proportion with the increase in the number of multi-family wood buildings built. Little work has been conducted to develop solutions to control the low-frequency footstep impact sound transmission. There are no code provisions or sound solutions in the codes. Current construction practices are based on a trial and error approach. This two-years project was conducted to remove this barrier and to successfully expand the use of wood in the multi-family and mid- to high-rise building markets. The key objective was to build a framework for the development of thorough solutions to control low-frequency footstep sound transmission through wood floor-ceiling assemblies.
Field acoustic tests and case studies were conducted in collaboration with acoustics researchers, builders, developers, architects, design engineers and producers of wood building components.
The field study found that:
1. With proper design of the base wood-joisted floors and sound details of the ceiling:
With no topping on the floor, the floor-ceiling assembly did not provide sufficient impact sound insulation for low- to high-frequency sound components ;
Use of a 13-mm thick wood composite topping along with the ceiling did not ensure satisfactory impact sound insulation;
Even if there was the ceiling, use of a 38-mm thick concrete topping without a proper insulation layer to float the topping did not ensure satisfactory impact sound insulation ;
A topping system having a mass over 20 kg/m2 and composed of composite panels and an insulation layer with proper thickness achieved satisfactory impact sound insulation.
2. The proper design of the base wood-joisted floors was achieved by the correct combination of floor mass and stiffness. The heaviest wood-joisted floors did not necessarily ensure satisfactory impact insulation.
3. Proper sound ceiling details were found to be achieved through:
Use of two layers of gypsum board;
Use of sound absorption materials filling at least 50% of the cavity ;
Installation of resilient channels to the bottom of the joists through anchoring acoustic system resulted in improved impact sound insulation than directly attaching the resilient channels to the bottom of the joists.
A four-task research plan was developed to thoroughly address the issue of poor low-frequency footstep impact insulation of current lightweight wood floor-ceiling assemblies and to correct prejudice against wood. The tasks include: 1) fundamental work to develop code provisions; 2) expansion of FPInnovations’ material testing laboratory to include tests to characterize the acoustic properties of materials; 3) development of control strategies; and 4) implementation.
The laboratory acoustic research facility built includes a mock-up field floor-ceiling assembly with adjustable span and room height, a testing system and a building acoustic simulation software.
The preliminary study on the effects of flooring, topping and underlayment on FIIC of the mock-up of the filed floor-ceiling assembly in FPInnovations’ acoustic chamber confirmed some findings from the field study. The laboratory study found that:
A topping was necessary to ensure the satisfactory impact sound insulation;
The topping should be floated on proper underlayment;
Topping mass affects impact sound insulation of wood framed floors;
A floating flooring enhanced the impact sound insulation of wood framed floors along with the floating topping.
It is concluded that:
1. even if the studies only touched the tip of the iceberg of the footstep impact sound insulation of lightweight wood-joisted floor systems, the proposed solutions are promising but still need verification ;
2. with proper design of the base wood floor structure, the proper combination of flooring, and sound ceiling details along with proper installation, the lightweight wood floor-ceiling assembly can achieve satisfactory impact sound insulation ;
3. this study establishes a framework for thoroughly solving low-frequency footstep impact sound insulation problem in lightweight wood-joisted floor systems.
Solutions will be developed in the next phase of this study as planned and the study will be conducted under NRCan Transformative Technology program with a project dedicated to “Serviceability of next generation wood building systems”.
During this MSc thesis it has been carried out an extensive literature review on fire safety engineering, on timber behaviour on fire and on fire safety regulations in different countries. A preliminary design for a high rise cross laminated timber building (CLT) has been carried out in order to obtain a minimum thickness of the structural elements needed for the load bearing structure. This thickness has been verified according to prescriptive fire regulations. Furthermore, fire safety analyses have been performed to evaluate a more realistic fire behaviour of exposed timber structures. The finite element program SAFIR and the fire model OZone have been used in the advance calculations. Finally, it is shown that timber buildings should be designed according to advance fire safety approach and suggestions are given for developing a timber fire model.
It is not surprising to see a rapid growth in the demand for mid- to high-rise buildings. Traditionally, these types of buildings have been dominated by steel and concrete. This trend creates a great opportunity for wood to expand its traditional single and low-rise multi-family building market to the growing mid- to high-rise building market. The significance and importance of wood construction to environmental conservation and the Canadian economy has been recognized by governments, the building industry, architects, design engineers, builders and clients. It is expected that more and more tall wood frame buildings of 6- to 8-storeys (or taller) will be constructed in Canada. Before we can push for use of wood in such applications, however, several barriers to wood success in its traditional and potential market places have to be removed. Lack of knowledge of the dynamic properties of mid- to high-rise wood and hybrid wood buildings and their responses to wind, and absence of current guidelines for wind vibration design of mid- to high-rise wood and hybrid wood buildings are examples of such barriers.
This thesis investigated light-frame wood/concrete hybrid construction as part of the NSERC Strategic Network on Innovative Wood products and Building Systems (NEWBuildS). A review of eight wood/concrete niche areas identified three with potential to be used in mid- to high-rise structures. Light-frame wood structures of seven or more storeys with wood/concrete hybrid flooring seem to have little feasibility unless a concrete lateral-load-resisting system is provided and material incompatibilities are solved. Non-load-bearing light-frame wood infill walls in reinforced concrete frame structures were recognized to have potential feasibility in mid- to high-rise structures. A full-scale, single frame test apparatus was successfully designed and constructed at the Insurance Research Lab for Better Homes. The frame is statically loaded to accurately replicates realistic horizontal sway and vertical racking deformations of a typical eight storey reinforced concrete frame structure at SLS and ULS. A linear-elastic analysis of the test apparatus was generally able to predict the results during testing. The 2.4m x 4.8m (8 ft. x 16 ft.) infill wall specimen did not satisfy serviceability deflection limitations of L/360 when subjected to representative out-of-plane wind pressures of +1.44/-0.9 kPa. The out-of-plane response was not significantly affected by horizontal sway deflections of +/-7.2mm or vertical racking deflections of +9.6mm. Although a nominal 20mm gap was provided to isolate the wall from the surrounding frame, insulation foam sprayed in the gap facilitated load transfer between them.
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.
Although the benefits of using timber in mid- and high-rise construction are undisputed, there are perceived shortcomings with respect to the ductility needed to provide seismic resistance and a corresponding lack of appropriate design guidance. Overcoming these perceived shortcomings will allow timber, and its wood product derivatives, to further expand into the multi-storey construction sector, also in the context of hybrid structures that integrate different materials. The “Finding the Forest Through the Trees” (FFTT) system is a new hybrid system for high rise structures which combines the advantages of timber and steel as building materials. This paper presents research utilizing finite element models to capture the seismic response of the FFTT system and help developing design guidance. From the results presented herein, it appears that the FFTT system can meet the design performance requirements required for seismic loading: inter-storey drifts were lower than required and local plastic deformations were within a reasonable range for life safety 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.
Cross laminated timber (CLT) has been rapidly developed and utilized for multi-rise constructions in recent years, even high-rise CLT buildings with 40 stories have been proposed and designed. A use of unbonded post-tensioning (PT) steel bars through over CLT walls of the high-rise CLT buildings to take up the tensile forces produced by wind load has been considered, following the regulations of unbonded post-tensioned (UPT) concrete walls. This paper introduces a finite element model to simulate the nonlinear lateral load behavior of the UPT high-rise CLT buildings with elastic connections between the CLT elements. The analysis results indicate that the unbonded PT bars can effectively reduce the lateral displacement of the high-rise CLT building. While compared with a theoretical full rigid CLT model, the advanced model is found to be more accurate for estimating the response of UPT high-rise CLT building under horizontal load.
Architects, engineers and researchers alike often cite practical reasons for building with wood. Since the development of curved glulam beams and columns over a century ago, the widespread use of massive structural timber elements has allowed architects and engineers to design and build in wood with unprecedented speed and scale. Moreover, rising concerns of climate change and the carbon-dioxide emissions associated with construction encourage the use of wood as a viable alternative to steel and concrete, due to CO2 sequestration in trees.
In mid- and high-rise buildings, the current shift from steel and concrete towards massive structural timber elements like glulam, laminated-veneer lumber (LVL) and cross-laminated timber (CLT) is evident in a number of recently completed timber buildings in Europe, ranging from seven to nine storeys. Several speculative design proposals have also been made for ‘timber towers’ of thirty, fortytwo and even sixty-five storeys, recognising that designing with massive structural timber elements in high-rise buildings is still in its infancy. This paper offers a new perspective on building with wood at this scale, beyond carbon sequestrationand construction.
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