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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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Bending properties of deconstructable cross-laminated timber-concrete composite floor elements

https://research.thinkwood.com/en/permalink/catalogue3275
Year of Publication
2022
Topic
Mechanical Properties
Material
Timber-Concrete Composite
Application
Floors
Author
Derikvand, Mohammad
Fink, Gerhard
Organization
Aalto University
Publisher
Taylor&Francis Online
Year of Publication
2022
Format
Journal Article
Material
Timber-Concrete Composite
Application
Floors
Topic
Mechanical Properties
Keywords
Self-Tapping Screws
Vibration
Stiffness
Disassembly
Research Status
Complete
Series
Wood Material Science & Engineering
Summary
Design for disassembly using deconstructable connections facilitates recycling and reusing of building materials and, therefore, reduces waste management problems at the end of service life. In this regard, a deconstructable timber-concrete composite connector using self-tapping screws has been developed at Aalto University. In the presented research, an experimental investigation was performed to further evaluate the effectiveness of this connector in fabricating deconstructable cross-laminated timber (CLT)-concrete composite floors. For this purpose, several CLT-concrete composite beams were fabricated using 5-layer CLT and low-shrinkage concrete. Each beam contained one row of connectors to represent a strip of a full-scale floor. The vibration performance, bending properties, interface slip, failure modes, and ease of disassembly of the beams were investigated. The results were compared with the ones from a reference group of beams fabricated with regular screws. Overall, the deconstructable beams performed exceptionally well by attaining 98.5% of the average bending stiffness of the regular beams. The load-carrying capacity was also similar but governed by the CLT plate. The vibration characteristics were comparable in both groups. After the bending test, the deconstructable beams were disassembled. Although the beams had been exposed to unproportionally large deformations under the bending load, the disassembly process was performed successfully.
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Shear stiffness of notched connectors in glue laminated timber-concrete composite beams under fire conditions

https://research.thinkwood.com/en/permalink/catalogue3375
Year of Publication
2022
Topic
Mechanical Properties
Material
Timber-Concrete Composite
Glulam (Glue-Laminated Timber)
Application
Beams
Author
Shi, D.
Hu, X.
Zhang, J.
Du, H.
Organization
Nanjing Tech University
Year of Publication
2022
Format
Journal Article
Material
Timber-Concrete Composite
Glulam (Glue-Laminated Timber)
Application
Beams
Topic
Mechanical Properties
Keywords
Notched Connection
Shear Stiffness
ISO Fire
Research Status
Complete
Series
BioResources
Summary
Shear connectors ensure effective interaction between wood beams and concrete slabs of composite beams, and their properties noticeably affect the fire resistance of timber-concrete composite beams. To investigate the shear stiffness of notched connectors in glued laminated timber (GLT)-concrete composite beams under fire conditions, 16 shear tests were conducted. The effects of fire duration and notch length on shear properties of the connectors for a given spacing were studied. The fire tests indicated that the reduction of the notch length from 200 mm to 150 mm remarkably affected the failure mode of the shear specimens, changing from compression failure of notched wood to shear failure of notched concrete. The increase in fire duration reduced effective width of the notched wood, negatively affected the shear stiffness and shear capacity of the connectors, and the shear stiffness decreased more rapidly. The notch length did not have a substantial effect on the shear stiffness of connectors. Based on the experimental results, an analytical model to estimate the shear stiffness of notched connectors in GLT-concrete beam under fire conditions was established.
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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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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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Strengthening of Full-Scale Laminated Veneer Lumber Beams with CFRP Sheets

https://research.thinkwood.com/en/permalink/catalogue3212
Year of Publication
2022
Topic
Mechanical Properties
Material
LVL (Laminated Veneer Lumber)
Application
Beams
Author
Bakalarz, Michal Marcin
Kossakowski, Pawel Grzegorz
Organization
Kielce University of Technology
Editor
Marcello, Angelo
Benzarti, Karim
Publisher
MDPI
Year of Publication
2022
Format
Journal Article
Material
LVL (Laminated Veneer Lumber)
Application
Beams
Topic
Mechanical Properties
Keywords
Composites
Carbon Fiber
Load-Bearing Capacity
Reinforcement
Stiffness
Research Status
Complete
Series
Materials
Summary
This paper presents the results of experimental research on full-size laminated veneer lumber (LVL) beams unreinforced and reinforced with CFRP sheets. The nominal dimensions of the tested beams were 45 mm × 200 mm × 3400 mm. The beams were reinforced using the so-called U-type reinforcement in three configurations, differing from each other in the thickness of the reinforcement and the side surface coverage. An epoxy resin adhesive was used to bond all the components together. A four-point static bending test was performed according to the guidelines in the relevant European standards. The effectiveness of the reinforcement increased with the level of coverage of the side surface and the level of reinforcement. The average increases of bending resistance were 42%, 51% and 58% for configurations B, C and D, respectively. The average value of bending stiffness increased for the beams of series B, C and D by 15%, 31% and 43%, respectively. Their failure mode changed from brittle fracture initiated in the tensile zone for unreinforced beams to more ductile fracture, initiated in the compression zone. The influence of the coverage of the side surface by the CFRP sheet and reinforcement ratio on the mechanism of failure and effectiveness of strengthening was studied in the article.
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Investigation of Thermal Effects on Nailed Connection of Mass Ply Panels

https://research.thinkwood.com/en/permalink/catalogue3320
Year of Publication
2022
Topic
Mechanical Properties
Connections
Material
MPP (Mass Plywood Panel)
Author
Ho, Tu X.
Laughery, Detlef C.
Sinha, Arijit
Organization
Oregon State University
Year of Publication
2022
Format
Journal Article
Material
MPP (Mass Plywood Panel)
Topic
Mechanical Properties
Connections
Keywords
Elevated Temperature
Exposure Duration
Stiffness Degradation
Strength Degradation
Research Status
Complete
Series
Forest Products Journal
Summary
Mass ply panels (MPP), a relatively new mass timber product, has been utilized in several construction projects as diaphragm and wall panels. Connection for MPP is a crucial structural component that requires a better understanding. This article presents an experimental investigation into elevated temperature exposure–driven property degradation of MPP nailed connections, which is important for both the design of new structures in terms of fire resistance and the rehabilitation of structures partially damaged by fire. One control group and 32 exposure groups, which were combinations of eight elevated temperatures and four exposure durations, were investigated. The failure modes and yield strength of the nailed connection were analyzed as a function of elevated temperature and exposure time and compared with the prediction from the National Design Specification and existing literature. The results show a decrease of up to 45 percent in initial stiffness and ultimate load; meanwhile, there was no statistical evidence for the change in yield load in the majority of testing groups. Two analytical models, namely, multilinear regression and first-order kinetics model, were proposed to model the degradation of initial stiffness and ultimate strength. The kinetics model provided a better prediction and suggested that the initial stiffness and ultimate strength of the nail connection degraded over time at rates depending on the exposure temperature.
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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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216 records – page 1 of 22.