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216 records – page 1 of 22.

Behavior of cross-laminated timber panels during and after an ISO-fire: An experimental analysis

https://research.thinkwood.com/en/permalink/catalogue3343
Year of Publication
2023
Topic
Fire
Material
CLT (Cross-Laminated Timber)
Author
Vairo, Maurizio
Silva, Valdir Pignatta
Icimoto, Felipe Hideyoshi
Organization
University of Sao Paulo
Publisher
Elsevier
Year of Publication
2023
Format
Journal Article
Material
CLT (Cross-Laminated Timber)
Topic
Fire
Keywords
Charring
ISO-fire
Post-fire Stiffness Reduction
Cooling Phase
Finite Element Analysis
Research Status
Complete
Series
Results in Engineering
Summary
Cross-laminated timber has been used in buildings since the 1990s. In the last years, there has been a growing interest in the use of this technology, especially with the adoption of the product in increasingly taller buildings. Considering that the product is manufactured from a combustible material, wood, authorities that regulate the fire safety in buildings and the scientific community have carried out numerous research and fire tests, aiming to elaborate codes which contemplate the use of cross-laminated timber in tall buildings. This paper discusses the main results obtained from the fire resistance test of a cross-laminated timber slab carried out in the horizontal gas furnace (3.0 m × 4.0 m x 1.5 m) from the University of Sao Paulo. A vertical load of 3 kN/m2 was applied over the slab and the specimens were exposed to the standard fire curve for 30 min. In addition to the 30-min test, the research also evaluated the thermal behavior of the samples during the 24 h after the burners were turned off. Throughout the test, the slab maintained the integrity and the thermal insulation, and no falling-off of the charred layer was observed. However, the 24-h test indicated that it is mandatory to consider the loss of stiffness and strength of timber caused by the thermal wave observed during the decay phase.
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Bending Properties and Vibration Characteristics of Dowel-Laminated Timber Panels Made with Short Salvaged Timber Elements

https://research.thinkwood.com/en/permalink/catalogue3359
Year of Publication
2023
Topic
Mechanical Properties
Material
DLT (Dowel Laminated Timber)
Author
Giordano, Lorenzo
Derikvand, Mohammad
Fink, Gerhard
Organization
Aalto University
Publisher
MDPI
Year of Publication
2023
Format
Journal Article
Material
DLT (Dowel Laminated Timber)
Topic
Mechanical Properties
Keywords
Bending Stiffness
Eigenfrequency
Damping Ratio
Salvaged Plywood
Wooden Connectors
Reuse
Circular Economy
Research Status
Complete
Series
Buildings
Summary
Salvaged timber elements often have length limitations, and therefore, their reuse in structural products normally would require additional processing and end-to-end joining. This increases the costs of reusing such materials, which makes them even less attractive to the timber sector. In the presented research, a new approach is proposed for reusing short, salvaged timber elements combined with new (full-scale) timber boards to fabricate dowel-laminated timber (DLT) panels without significant processing or end-to-end joining or gluing. In this approach, salvaged timber elements are pressed in the system in such a way that they can contribute to the bending performance of the DLT panels by resisting compression stress. In order to evaluate the effectiveness, several small-scale and large-scale DLT panels were fabricated. Salvaged plywood tenons were used as connectors. The bending stiffness of the small-scale DLT panels and the first eigenfrequency, damping ratio, bending properties, and failure modes of the large-scale DLT panels were evaluated. The results exhibited that by using the proposed approach, the short, salvaged timber elements can contribute substantially to the bending stiffness of the DLT panels without requiring end-to-end joining or gluing. On average, about a 40% increase in the bending stiffness could be achieved by pressing in the salvaged timber elements, which results in relatively similar stiffness properties compared to conventional DLT panels. One further characteristic is that the failure of the panels, and therefore the panel’s strength, is mainly governed by the quality of the full-scale timber boards instead of the salvaged ones. This can be beneficial for practical use as the qualitative assessment of the strength properties of salvaged timber becomes less critical.
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Experimental investigations of a new highly ductile hold-down with adaptive stiffness for timber seismic bracing walls

https://research.thinkwood.com/en/permalink/catalogue3370
Year of Publication
2023
Topic
Seismic
Material
CLT (Cross-Laminated Timber)
Application
Shear Walls
Author
Maître, K.
Lestuzzi, P.
Geiser, M.
Organization
Bern University of Applied Sciences
École Polytechnique Fédérale de Lausanne
Publisher
Springer
Year of Publication
2023
Format
Journal Article
Material
CLT (Cross-Laminated Timber)
Application
Shear Walls
Topic
Seismic
Keywords
Hold-Down
Adaptative Stiffness
Buckling Restrained Brace
Capacity Design
CLT Shear Wall
High Ductility
Research Status
Complete
Series
Bulletin of Earthquake Engineering
Summary
An efficient implementation of the capacity design requires high ductility combined with a low overstrength of the critical regions. Conventional timber connections do not generally offer such ideal combination, resulting in modest behaviour and relatively high overstrength factors. Inspired by the Buckling Restrained Brace a new hold-down has been developed where the timber wall directly acts as a casing. The new hold-down has been given an adaptive stiffness allowing the structure to be stiff in the wind, while becoming more flexible in the case of an earthquake. Furthermore, local crushing of the timber members is completely avoided, and the new hold-down could be replaced after an earthquake. Experimental investigations were performed on hold-down specimens. The results show ultimate displacement values vu,c of more than 30 mm in a cyclic test according to EN12512. Eleven Cross Laminated Timber shear walls, in which the new hold-down has been implemented, were tested following monotonic and static-cyclic tests procedures, with and without vertical load. A very high ductility has been achieved with almost no strength degradation, little pinching and limited overstrength.
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Reduced and test-data correlated FE-models of a large timber truss with dowel-type connections aimed for dynamic analyses at serviceability level

https://research.thinkwood.com/en/permalink/catalogue3004
Year of Publication
2022
Topic
Mechanical Properties
Serviceability
Acoustics and Vibration
Material
Glulam (Glue-Laminated Timber)
Application
Trusses
Author
Landel, Pierre
Linderholt, Andreas
Organization
RISE Research Institutes of Sweden
Linnaeus University
Publisher
Elsevier
Year of Publication
2022
Format
Journal Article
Material
Glulam (Glue-Laminated Timber)
Application
Trusses
Topic
Mechanical Properties
Serviceability
Acoustics and Vibration
Keywords
Tall Timber Structures
Mechanical Connection
Dowel-type Fastener
Wind-induced Vibration
Modal Testing Properties
Connection Stiffness
FE-Model Reduction
Research Status
Complete
Series
Engineering Structures
Summary
The rise of wood buildings in the skylines of cities forces structural dynamic and timber experts to team up to solve one of the new civil-engineering challenges, namely comfort at the higher levels, in light weight buildings, with respect to wind-induced vibrations. Large laminated timber structures with mechanical joints are exposed to turbulent horizontal excitation with most of the wind energy blowing around the lowest resonance frequencies of 50 to 150 m tall buildings. Good knowledge of the spatial distribution of mass, stiffness and damping is needed to predict and mitigate the sway in lighter, flexible buildings. This paper presents vibration tests and reductions of a detailed FE-model of a truss with dowel-type connections leading to models that will be useful for structural engineers. The models also enable further investigations about the parameters of the slotted-in steel plates and dowels connections governing the dynamical response of timber trusses.
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Experimental and numerical study on the bending response of a prefabricated composite CLT-steel floor module

https://research.thinkwood.com/en/permalink/catalogue3047
Year of Publication
2022
Topic
Mechanical Properties
Material
CLT (Cross-Laminated Timber)
Steel-Timber Composite
Application
Floors
Author
Owolabi, David
Loss, Cristiano
Organization
University of British Columbia
Publisher
Elsevier
Year of Publication
2022
Format
Journal Article
Material
CLT (Cross-Laminated Timber)
Steel-Timber Composite
Application
Floors
Topic
Mechanical Properties
Keywords
Composite Floors
Hybrid Construction
Mass Timber
Cross-laminated Timber
Prefabricated Construction
Low-Carbon Structures
Bending Stiffness
Research Status
Complete
Series
Engineering Structures
Summary
Cross-laminated timber (CLT) is one of the most widely utilized mass timber products for floor construction given its sustainability, widespread availability, ease of fabrication and installation. Composite CLT-based assemblies are emerging alternatives to provide flooring systems with efficient design and optimal structural performance. In this paper, a novel prefabricated CLT-steel composite floor module is investigated. Its structural response to out-of-plane static loads is assessed via 6-point bending tests and 3D finite-element computational analysis. For simply supported conditions, the results of the investigation demonstrate that the floor attains a high level of composite efficiency (98%), and its bending stiffness is about 2.5 times those of its components combined. Within the design load range, the strain diagrams are linear and not affected by the discontinuous arrangement and variable spacing of the shear connectors. The composite floor module can reach large deflection without premature failure in the elements or shear connectors, with plasticity developed in the cold-formed steel beams and a maximum attained load 3.8 times its ultimate limit state design load. The gravity design of the composite module is shown to be governed by its serviceability deflection requirements. However, knowledge gaps still exist on the vibration, fire, and long-term behaviour of this composite CLT-steel floor system.
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Analytical Procedure for Timber-Concrete Composite (TCC) System with Mechanical Connectors

https://research.thinkwood.com/en/permalink/catalogue3119
Year of Publication
2022
Topic
Design and Systems
Material
Timber-Concrete Composite
Application
Floors
Author
Mirdad, Md Abdul Hamid
Khan, Rafid
Chui, Ying Hei
Organization
University of Illinois at Urbana-Champaign
University of Alberta
Editor
Tullini, Nerio
Publisher
MDPI
Year of Publication
2022
Format
Journal Article
Material
Timber-Concrete Composite
Application
Floors
Topic
Design and Systems
Keywords
Mechanical Connectors
Progressive Yielding
Effective Bending Stiffness
Deflection
Vibration
Research Status
Complete
Series
Buildings
Summary
In the construction of modern multi-storey mass timber structures, a composite floor system commonly specified by structural engineers is the timber–concrete composite (TCC) system, where a mass timber beam or mass timber panel (MTP) is connected to a concrete slab with mechanical connectors. The design of TCC floor systems has not been addressed in timber design standards due to a lack of suitable analytical models for predicting the serviceability and safety performance of these systems. Moreover, the interlayer connection properties have a large influence on the structural performance of a TCC system. These connection properties are often generated by testing. In this paper, an analytical approach for designing a TCC floor system is proposed that incorporates connection models to predict connection properties from basic connection component properties such as embedment and withdrawal strength/stiffness of the connector, thereby circumventing the need to perform connection tests. The analytical approach leads to the calculation of effective bending stiffness, forces in the connectors, and extreme stresses in concrete and timber of the TCC system, and can be used in design to evaluate allowable floor spans under specific design loads and criteria. An extensive parametric analysis was also conducted following the analytical procedure to investigate the TCC connection and system behaviour. It was observed that the screw spacing and timber thickness remain the most important parameters which significantly influence the TCC system behaviour.
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Structural Performance of Mass Timber Panel-Concrete Composite Floors with Notched Connections

https://research.thinkwood.com/en/permalink/catalogue3122
Year of Publication
2022
Topic
Mechanical Properties
Material
Timber-Concrete Composite
Application
Floors
Author
Zhang, Lei
Organization
University of Alberta
Year of Publication
2022
Format
Thesis
Material
Timber-Concrete Composite
Application
Floors
Topic
Mechanical Properties
Keywords
Notched Connection
Discrete Bond Composite Beam Model
Mass Timber Panel
Connection Stiffness
Effective Bending Stiffness
Load-Carrying Capacity
Research Status
Complete
Summary
This thesis focuses on the structural performance of mass timber panel-concrete composite floors with notches. Mass timber panels (MTPs) such as cross-laminated timber, glue-laminated timber, and nail-laminated timber, are emerging construction materials in the building industry due to their high strength, great dimensional stability, and prefabrication. The combination of MTPs and concrete in the floor system offers many structural, economic, and ecological benefits. The structural performance of MTP-concrete composite floors is governed by the shear connection system between timber and concrete. The notched connections made by cutting grooves on timber and filling them with concrete are considered as a structurally efficient and cost-saving connecting solution for resisting shear forces and restricting relative slips between timber and concrete. However, the notched connection design in the composite floors is not standardized and the existing design guidelines are inadequate for MTP-concrete composite floors. To study the structural performance of notched connections and notch-connected composite floors, this thesis presented experimental, numerical, and analytical investigations. Push-out tests were conducted on the notched connections first, and then bending tests and vibration tests were conducted on full-scale composite floors. Finite element models were built for the notched connections to derive the connection shear stiffness. Finally, analytical solutions were developed to predict the internal actions of the composite floors under external loads. This study shows that the structural performance of notched connections is affected by the geometry of the connections and material properties of timber and concrete. The notch-connected MTP-concrete composite floors showed high bending stiffness but were not fully composite. The floors with shallow notches tended to fail in a ductile manner but had lower bending stiffness than floors with deep notches. The composite floors with deep notches, however, often fail abruptly in the concrete notches. By reinforcing the notched connections with steel fasteners, the composite floor can achieve high bending stiffness, high load-carrying capacity, and controlled failure pattern. The proper number and locations of notched connections in the composite floors can be determined from the proposed composite beam model. This thesis presented promising results in terms of the static and dynamic structural performance of notch-connected MTP-concrete composite floors. The test investigations added additional data to the current research body and prompted further evolvement of timber-concrete composite floors. The proposed empirical equations for estimating the connection stiffness and strength and composite beam model for predicting the serviceability and ultimate structural performance of composite floors provide useful tools to analyze the notch-connected MTP-concrete composite floors. The design recommendations for MTP-concrete composite floors with notches are provided in the thesis.
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Moment-resisting beam-to-column timber connections with inclined threaded rods: Structural concept and analysis by use of the component method

https://research.thinkwood.com/en/permalink/catalogue3132
Year of Publication
2022
Topic
Connections
Author
Stamatopoulos, Haris
Malo, Kjell Arne
Vilguts, Aivars
Organization
Norwegian University of Science and Technology
Publisher
Elsevier
Year of Publication
2022
Format
Journal Article
Topic
Connections
Keywords
Moment-resisting Connection
Threaded Rod
Rotational Stiffness
Research Status
Complete
Series
Construction and Building Materials
Summary
The use of moment-resisting frames with semi-rigid connections as a lateral load-carrying system in timber buildings can reduce the need for bracing with diagonal members or walls and allow for more open and flexible architecture. The overall performance of moment-resisting frames depends largely on the properties of their connections. Screwed-in threaded rods with wood screw thread feature high axial stiffness and capacity and they may be used as fasteners in beam-to-column, moment-resisting timber connections. In the present paper, a structural concept for a beam–to-column, moment-resisting timber connection based on threaded rods is presented and explained. Analytical expressions for the estimation of the rotational stiffness and the forces in the rods were derived based on a component-method approach. The analytical predictions for stiffness were compared to experimental results from full scale tests and the agreement was good.
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An experimental study of the stiffness and strength of cross-laminated timber wall-to-floor connections under compression perpendicular to the grain

https://research.thinkwood.com/en/permalink/catalogue3197
Year of Publication
2022
Topic
Connections
Material
CLT (Cross-Laminated Timber)
Application
Floors
Walls
Author
Schweigler, Michael
Akter, Shaheda T.
Sabaa, Stephen
Bader, Thomas K.
Organization
Linnaeus University
Publisher
Elsevier
Year of Publication
2022
Format
Journal Article
Material
CLT (Cross-Laminated Timber)
Application
Floors
Walls
Topic
Connections
Keywords
Compression Perpendicular To Grain
Stress Dispersion
Nominal Stiffness
Nominal Strength
Digital Image Correlation
Research Status
Complete
Series
Engineering Structures
Summary
In platform-type multi-story cross-laminated timber (CLT) buildings, gravity loads from upper floors, and vertical reaction forces from horizontal actions, like wind loads, cause substantial compressive forces in the CLT-floor elements. The combination of these high forces with a comparable low compression stiffness and strength perpendicular to the grain of timber, makes the compression perpendicular to the grain (CPG) verification of CLT an important design criterion. In this experimental study, CPG of CLT was investigated by means of typical wall-to-floor connections in CLT platform-type structures. CLT-wall elements were used for load application to transmit forces through the CLT-floor element by CPG. Compared to load application by steel elements, as it commonly is done in experiments, lower stiffness but similar strength were found for CLT walls. The study of different connection types showed the highest stiffness and strength for connections assembled with screws, followed by pure wood-to-wood contact, while connections with acoustic layers between the floor and wall elements showed the lowest stiffness and strength. In addition, these connections were tested for center and edge load position on the CLT-floor element. The strength for center and edge position compared to full surface loaded specimens increased linearly with the activated material volume, as determined by earlier proposed stress dispersion models. The stress dispersion effect was visualized by surface strain measurements using digital image correlation technique. Also, the stiffness increased with the activated material volume. Stress dispersion in the CLT-floor allowed to explain the increase in stiffness and strength with decreasing CLT-wall thickness. Strength values at different strain levels, and stiffness and strength increase factors suitable for the engineering design of CLT structures are provided.
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Numerical and Experimental Analysis of the Load-Carrying Capacity of a Timber Semi-Rigid Dowel-Type Connection

https://research.thinkwood.com/en/permalink/catalogue3208
Year of Publication
2022
Topic
Mechanical Properties
Connections
Material
Glulam (Glue-Laminated Timber)
Author
Johanides, Marek
Lokaj, Antonin
Dobes, Pavel
Mikolasek, David
Organization
VSB-Technical University of Ostrava
Editor
Mirshi, Radoslaw
Landolfo, Raffaele
Publisher
MDPI
Year of Publication
2022
Format
Journal Article
Material
Glulam (Glue-Laminated Timber)
Topic
Mechanical Properties
Connections
Keywords
Bolts and Dowels
Dowel-type Fasteners
FEM
Frame Connection
Fully Threaded Screws
Numerical Model
Rotational Stiffness
Research Status
Complete
Series
Materials
Summary
The paper deals with the analysis of the load-carrying capacity of a timber semi-rigid connection created from a system of two stands and a rung. The connection was made from glued laminated timber with metal mechanical dowel-type fasteners. Not only a common combination of bolts and dowels, but also fully threaded screws were used for the connection. The aim of the research and its motivation was to replace these commonly used fasteners with more modern ones, to shorten and simplify the assembly time, and to improve the load-carrying capacity of this type of connection. Each of these two types of connections was loaded statically, with a slow increase in force until failure. The paper presents results of the experimental testing. Three specimens were made and tested for each type of the connection. Experimental results were subsequently compared with numerical models. The achieved results were also compared with the assumption according to the currently valid standard. The results indicate that a connection using fully threaded screws provides a better load-carrying capacity.
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216 records – page 1 of 22.