Cross-laminated timber (CLT) is well known as an interesting technical and economical product for modern wood structures. The use of CLT for modern construction industry has become increasingly popular in particular for residential timber buildings. Analyzing the CLT behavior in high thermal environment has attracted scholars’ attention. Thermal environment greatly influences the CLT properties and load bearing capacity of CLT, and the investigation can form the basis for predicting the structural response of such CLT-based structures. In the present work, the finite element method (FEM) is employed to analyze the thermal influence on the deformation of CLT. Furthermore, several factors were taken into consideration, including board layer number, hole conformation, and hole position, respectively. In order to determine the influence, several numerical models for different calculation were established. The calculation process was validated by comparing with published data. The performance is quantified by demonstrating the temperature distribution and structural deformation.
The main objective of this preliminary study is to evaluate the heat release rate and fire growth contribution due to heat delamination characteristics of CLT manufactured with current certified ANSI/APA PRG-320 adhesives used for face bonding, when exposed to a constant radiant heat flux. The evaluation is performed using the principles of ISO 5660-1 “Reaction-to-fire tests - Heat release, smoke production and mass loss rate – Part 1: Heat release rate (cone calorimeter method)” . The American version of this test method is ASTM E1354 « Standard Test Method for Heat and Visible Smoke Release Rates for Materials and Products Using an Oxygen Consumption Calorimeter » .
The long-term objective is to determine which currently accepted test methods allow for a better evaluation of heat delamination characteristics of adhesives used in structural engineered wood products, based on their actual end-use applications (e.g. bending, compression, combined stress, cross-plies, etc.)
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.
Recent architectural trends include the design and construction of increasingly tall buildings with structural components comprised of engineered wood referred to by names including; cross laminated timber (CLT), laminated veneer lumber (LVL), or glued laminated timber (Glulam). These buildings are cited for their advantages in sustainability resulting from the use of wood as a renewable construction material. Previous research has shown that timber elements contribute to the fuel load in buildings and can increase the initial fire growth rate – potentially overwhelming fire protection system and creating more severe conditions for occupants, emergency responders, and nearby properties.
The overarching goal of this project Fire Safety Challenges of Tall Wood Buildings Phase 2 (involving five tasks) is to quantify the contribution of CLT building elements (wall and/or floor-ceiling assemblies) in compartment fires and provide data to allow comparison of the performance of CLT systems against other building systems commonly used in tall buildings.
Cross-laminated timber (CLT) is a popular construction material for low and medium-rise construction. However an architectural aspiration exists for tall mass timber buildings, and this is currently hindered by knowledge gaps and perceptions regarding the fire behaviour of mass timber buildings. To begin to address some of the important questions regarding the structural response of fire-exposed CLT structures in real fires, this paper presents a series of novel fire tests on CLT beams subjected to sustained flexural loading, coincident with non-standard heating using an incident heat flux sufficient to cause continuous flaming combustion. The load bearing capacities and measured time histories of deflection during heating are compared against predicted responses wherein the experimentally measured char depths are used, along with the Eurocode recommended reduced cross section method and zero-strength layer thickness. The results confirm that the current zero-strength layer value (indeed the zero-strength concept) fails to capture the necessary physics for robust prediction of structural response under non-standard heating. It is recommended that more detailed thermo-mechanical cross-sectional analyses, which allow the structural implications of real fire exposures to be properly considered, should be developed and that the zero-strength layer concept should be discarded in these situations. Such a novel approach, once developed and suitably validated, could offer more realistic and robust structural fire safety design.
Consolidated knowledge of CLT properties under in-plane shear is crucial for typical structural applications such as wall and floor diaphragms, cantilevered CLT walls and CLT used as (deep) beams, in all cases potentially featuring holes or notches. The current technical approvals for CLT products contain differing regulations to determine their load-carrying capacities in-plane. Generally they imply a verification of the torsional stresses in the cross-section of the cross-wise glued elements as well as a verification of the shear stresses proportionally assigned to the boards of the top and cross layers. The basis of theoretical and practical considerations are the following three basic failure scenarios for a CLT-element under in-plane shear: (i) gross-shear (longitudinal shearing in all layers), (ii) net-shear (transverse shearing in all layers in weak direction), and (iii) torsion failure in the gluing interfaces between the layers
Concrete is the most widely used construction material in the world. This material causes formation and release of CO2 and high energy consumption during manufacturing. One way to decrease concrete consumption negative consequences is to replace it with lower needed primary energy materials, like timber. The engineered wood products such as laminated veneer lumber (LVL)...