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Self-Tapping Screws and Threaded Rods as Reinforcement for Structural Timber Elements - A State-Of-The-Art Report

https://research.thinkwood.com/en/permalink/catalogue448
Year of Publication
2015
Topic
Connections
Serviceability
Material
CLT (Cross-Laminated Timber)
Glulam (Glue-Laminated Timber)
Author
Dietsch, Philipp
Brandner, Reinhard
Publisher
ScienceDirect
Year of Publication
2015
Country of Publication
Netherlands
Format
Journal Article
Material
CLT (Cross-Laminated Timber)
Glulam (Glue-Laminated Timber)
Topic
Connections
Serviceability
Keywords
Reinforcement
Threaded Rods
Self-Tapping Screws
Shear Stress
Europe
Language
English
Research Status
Complete
Series
Construction and Building Materials
Summary
In timber engineering, self-tapping screws, optimized primarily for axial loading, represent the state-of-the-art in fastener and reinforcement technology. Their economic advantages and comparatively easy handling make them one of the first choices for application in both domains. This paper focuses on self-tapping screws and threaded rods applied as reinforcement, illustrating the state-of-the-art in application and design approaches in Europe, in conjunction with numerous references for background information. With regard to medium to large span timber structures which are predominately erected by using linear timber members, from e.g. glued laminated timber, the focus of this paper is on their reinforcement against stresses perpendicular to grain as well as shear. However, latest findings with respect to cross laminated timber are included as well.
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Cross-Laminated Timber Failure Modes for Fire Conditions

https://research.thinkwood.com/en/permalink/catalogue188
Year of Publication
2015
Topic
Fire
Material
CLT (Cross-Laminated Timber)
Author
Emberley, Richard
Torero, José
Year of Publication
2015
Country of Publication
Australia
Format
Conference Paper
Material
CLT (Cross-Laminated Timber)
Topic
Fire
Keywords
Adhesives
Charring Rate
Delamination
Codes
Failure Modes
Language
English
Conference
International Conference on Performance-based and Life-cycle Structural Engineering
Research Status
Complete
Notes
December 9-11, 2015, Brisbane, Australia
Summary
Tall timber building designs have utilized cross-laminated timber (CLT) significantly over the past decade due the sustainable nature of timber and the many advantages of using an engineered mass timber product. Several design methods have been established to account for the composite action between the orthogonally adhered timber plies. These methods assume perfect bonding of the adjacent plies by the adhesive. CLT designs methods for timber in fire have also been formulated. These methods rely on the relatively constant charring rate of timber to calculate a sacrificial layer to be added onto the cross-sectional area. While these methods focus on the timber failure mode of reduced cross section by charring, the failure mode of ply delamination is often overlooked and understudied. Due to the reduction of shear and normal strength in the adhesive, the perfect bond assumption can be questioned and a deeper look into the mechanics of CLT composite action and interfacial stress needs be conducted. This paper seeks to highlight the various design methods for CLT design and identify the failure mode of delamination not present in the current design codes.
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New Design Approach for Controlling Brittle Failure Modes of Small-Dowel-Type Connections in Cross-Laminated Timber (CLT)

https://research.thinkwood.com/en/permalink/catalogue155
Year of Publication
2015
Topic
Connections
Design and Systems
Material
CLT (Cross-Laminated Timber)
Author
Zarnani, Pouyan
Quenneville, Pierre
Publisher
ScienceDirect
Year of Publication
2015
Country of Publication
Netherlands
Format
Journal Article
Material
CLT (Cross-Laminated Timber)
Topic
Connections
Design and Systems
Keywords
Brittle Failure Mode
Fasteners
Stiffness
Language
English
Research Status
Complete
Series
Construction and Building Materials
Summary
The introduction of Cross-laminated Timber (CLT) as an engineered timber product has played a significant role in considerable progress of timber construction in recent years. Extensive research has been conducted in Europe and more recently in Canada to evaluate the fastening capacity of different types of fasteners in CLT. While ductile capacities calculated using the yield limit equations are quite reliable for fastener resistance in connections, however, they do not take into account the possible brittle failure mode of the connection which could be the governing failure mode in multi-fastener joints. Therefore, a stiffness-based design approach which has already been developed by the authors and verified in LVL, glulam and lumber has been adapted to determine the block-tear out resistance of connections in CLT by considering the effect of perpendicular layers. The comparison between the test results on riveted connections conducted at the University of Auckland (UoA) and the Karlsruhe Institute of Technology (KIT) and the predictions using the new model and the one developed for uniformly layered timber products show that the proposed model provides higher predictive accuracy and can be used as a design provision to control the brittle failure of wood in CLT connections.
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Repair and Reinforcement of Timber Columns and Shear Walls - A Review

https://research.thinkwood.com/en/permalink/catalogue867
Year of Publication
2015
Topic
Serviceability
Material
Solid-sawn Heavy Timber
Application
Shear Walls
Columns
Author
Chang, Wen-Shao
Publisher
ScienceDirect
Year of Publication
2015
Country of Publication
Netherlands
Format
Journal Article
Material
Solid-sawn Heavy Timber
Application
Shear Walls
Columns
Topic
Serviceability
Keywords
Reinforcement
Repair
Long-term
Language
English
Research Status
Complete
Series
Construction and Building Materials
Summary
Although it was found that most of the research foci were on reinforcement of timber connections and flexural members, columns and shear walls play a crucial role in the prevention of structural collapse. Recent trends to build taller timber structures, a demand for structures with larger span, and re-use of existing structures for different purposes have made reinforcement of timber columns and shear walls increasingly important. In addition, repair of damaged timber columns and shear walls so as to prevent further damage to the structures and elongate the life span of existing structures is also important. This paper provides an overview of techniques available to repair and strengthen timber columns and shear walls in both research and practice.
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Failure Mechanism of Rolling Shear Failure in Cross-Laminated Timber

https://research.thinkwood.com/en/permalink/catalogue1172
Year of Publication
2015
Topic
Mechanical Properties
Material
CLT (Cross-Laminated Timber)
Author
Nie, Xin
Organization
University of British Columbia
Year of Publication
2015
Country of Publication
Canada
Format
Thesis
Material
CLT (Cross-Laminated Timber)
Topic
Mechanical Properties
Keywords
Failure Mechanisms
Rolling Shear
Finite Element Model
Failure Modes
Tension Perpendicular to Grain
Center Point Bending Test
Language
English
Research Status
Complete
Summary
Wood as building material is gaining more and more attention in the 21st century due to its positive attributes such as light weight, renewability, low carbon footprint and fast construction period. Cross-laminated timber (CLT), as one of the new engineered wood products, requires more research emphasis since its mechanical performance can allow CLT to be utilized in massive timber structures. This thesis focuses on revealing one of the key failure mechanisms of CLT, which is usually referred to as the rolling shear failure. The scientific research conducted in this thesis combined both analytical modelling and experimental material testing. The stresses in CLT cross-layers obtained from a finite-element model were analyzed to differentiate various failure modes possible. Tension perpendicular to grain stress was found to cause cross-layer failure in combined with the rolling shear stress. Experimentally, specimens prepared from 5-layer CLT panels were tested under center-point bending condition. Detailed failure mechanism of CLT cross-layers were recorded with high speed camera to capture the instant when initial failure happened. It is evident that some of the specimens failed in tension perpendicular to grain which verified the modelling results. Variables such as the rate of loading and the manufacturing clamping pressure were designed in experiments to compare their influence to the failure of CLT specimens. In this research, the failure of CLT cross-layer was updated to a combined consequence of both rolling shear stress and tension perpendicular to grain stress. Future research topics and product improvement potentials were given by the end of this thesis.
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Experimental Testing of Glued Laminated Timber Members using Ultrasonic and Stress Wave Techniques

https://research.thinkwood.com/en/permalink/catalogue151
Year of Publication
2015
Topic
Mechanical Properties
Material
Glulam (Glue-Laminated Timber)
Author
Nowak, Tomasz
Hamrol-Bielecka, Katarzyna
Jasienko, Jerzy
Organization
Structural Health Assessment of Timber Structures
Year of Publication
2015
Country of Publication
Poland
Format
Conference Paper
Material
Glulam (Glue-Laminated Timber)
Topic
Mechanical Properties
Keywords
Non-Destructive
Physical Properties
Spruce
Stress
Ultrasonic
Wave Propagation
Wave Techniques
Language
English
Conference
Structural Health Assessment of Timber Structures 15
Research Status
Complete
Notes
September 9-11, 2015, Wroclaw, Poland
Summary
The paper presents the application of ultrasonic and stress wave techniques in testing the physical and mechanical properties of timber. One of the non-destructive methods for testing timber in construction involves measuring the velocity of ultrasonic and stress wave propagation. The research was carried out using a portable Sylvatest Trio device, which uses ultrasonic technology and a Fakopp Microsecond Timer device, which employs the stress wave technique. The devices measure the wave transition time along a given length of the material, providing qualitative (the extent of possible degradation, structural discontinuities etc.) and quantitative results (density, strength, modulus of elasticity) relating to the state of the timber under study. The paper reports on research on the correlation between wood properties and parameters of ultrasonic and stress wave propagation. The study focused on glued laminated spruce wood of strength class GL24h. Testing involved application of two methods of setting up transducers: directly where the device heads are located on the opposite planes of the test specimens, and where the device heads are located in parallel to or perpendicular to the grain.
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State-Of-The-Art Review on Cyclic Behaviour of Connections Used in CLT Multi-Storey Buildings: Test Results and Modelling

https://research.thinkwood.com/en/permalink/catalogue472
Year of Publication
2015
Topic
Connections
Mechanical Properties
Material
CLT (Cross-Laminated Timber)
Application
Wood Building Systems
Author
Branco, Jorge
Sousa, Hélder
Lourenço, Paulo
Ahvenainen, Julia
Aranha, Chrysl
Publisher
Dolnoslaskie Wydawnictwo Edukacyjne (DWE)
Year of Publication
2015
Country of Publication
Poland
Format
Conference Paper
Material
CLT (Cross-Laminated Timber)
Application
Wood Building Systems
Topic
Connections
Mechanical Properties
Keywords
Monotonic Tests
Cyclic Tests
Strength
Damping Ratios
Language
English
Conference
International Conference on Structural Health Assessment of Timber Structures
Research Status
Complete
Notes
September 9-11, 2015, Wroclaw, Poland
Summary
A timber building made of cross-laminated timber (CLT) panels is a modular system where all panels are pre-cut in factory. On site, the single components are then assembled connecting the panels with mechanical fasteners, mainly angle brackets with nails and/or screws, hold-downs, metal plates and self-tapping screws. CLT wall panels are very rigid in comparison to its connections. Thus, connections play an essential role in maintaining the integrity of the structure providing the necessary strength, stiffness and ductility, and consequently, they need close attention by designers. However, there is still a lack of proper design rules for these connections, in particular under cyclic loads, mainly due to a large variety of connectors and connection systems. In this paper, the different properties of connections for CLT buildings, on both monotonic and cyclic behaviour, are described using recent works from different authors. From the bibliography, it is clear that experimental data, regarding both monotonic and cyclic tests, is required for the assessment of the performance of the CLT structural system attending to the interaction between rigid panels and connections. This work evidences results from experimental campaigns and numerical analysis regarding definition and quantification of the cyclic response of CLT connections. Examples regarding monotonic and cyclic tests aimed to evaluate cyclic behaviour of connections through physical parameters, such as the impairment of strength and the damping ratio, are presented and discussed.
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Dynamic Effects in Reinforced Timber Beams at Time of Timber Fracture

https://research.thinkwood.com/en/permalink/catalogue2303
Year of Publication
2015
Topic
Design and Systems
Application
Beams

Modeling of Barrier Failure and Fire Spread in Curisk

https://research.thinkwood.com/en/permalink/catalogue300
Year of Publication
2015
Topic
Fire
Material
CLT (Cross-Laminated Timber)
Light Frame (Lumber+Panels)
Application
Wood Building Systems
Author
Li, Xiao
Organization
Carleton University
Year of Publication
2015
Country of Publication
Canada
Format
Thesis
Material
CLT (Cross-Laminated Timber)
Light Frame (Lumber+Panels)
Application
Wood Building Systems
Topic
Fire
Keywords
CUrisk
Fire Spread
Residential
Full Scale
Barrier Failure
Language
English
Research Status
Complete
Summary
To better evaluate failure of building elements and spread of fire beyond the room of fire origin, this thesis developed and integrated into CUrisk a barrier failure model and a fire spread model. The role and position of the Fire Spread submodel were analyzed and changes to the system model and some other submodels were undertaken. With these modifications, CUrisk can employ the Fire Spread submodel to predict the fire hazard conditions in a building fire, and to use the results to predict the life risk and fire damages. Through a comprehensive case study of fire risk assessment of a six-storey residential building using the improved CUrisk, the Fire Spread submodel demonstrated the impacts of fire spread level on building occupant safety and fire losses. The model performance was verified by comparing with the fire test measurements, which demonstrated good agreements. Comparable results are also predicted regarding the fall-off behaviour of the fire-exposed gypsum board as well as the charring behaviour. In addition, an example calculation was made using the probabilistic barrier failure model. Finally, a fire risk analysis case study was conducted on a six-storey apartment building with the purpose of showing the effect of wall barriers on fire risk. Results indicated that CUrisk can evaluate the impact of fire barriers on the fire risk with the new Barrie Failure submodel.
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Makerjoint, a New Concept for Joining Members in Timber Engineering – Strength Test and Failure Analyses

https://research.thinkwood.com/en/permalink/catalogue260
Year of Publication
2015
Topic
Connections
Mechanical Properties
Material
LVL (Laminated Veneer Lumber)
Author
Rebstock, Florian
Bomark, Peter
Sandberg, Dick
Year of Publication
2015
Country of Publication
Romania
Format
Journal Article
Material
LVL (Laminated Veneer Lumber)
Topic
Connections
Mechanical Properties
Keywords
CNC
Prefabrication
Failure Modes
Tensile Strength
Compressive Strength
Joints
Language
English
Research Status
Complete
Series
Pro Ligno
ISSN
2069-7430
Summary
The wood construction industries are becoming more focused on climate change and resource depletion, and individual and industrial consumption must reflect a greater degree of concern for the climate and environmental wellbeing. This paper presents a new concept for timber engineering, the purpose being to acquire information about the failure modes and the tensile and compressive strengths of two types of joint, the Simple Gooseneck and Thick Gooseneck, that can be used in a new concept for joining members in timber structures. This Makerjoint concept uses laminated veneer lumber (LVL) as nodes in regions with a pronounced non-uniform stress distribution and sawn timber in regions with a more uniform stress distribution. No metal fasteners or adhesives are used in the joint between timber and LVL. The concept is intended for joints using 3-axis CNC machinery and to be a system for on-site- and pre-fabrication of e.g. small houses, emergency shelters and exhibition stands. The joints have a higher compressive than tensile strength. The joints exhibited brittle failure in tension (beam and/or node failure) and buckling occurred in compression around the thinnest cross section of the beams. Suggestions are made for how the mechanical properties of the joints can be improved.
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10 records – page 1 of 1.