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17 records – page 1 of 2.

Evaluating Rolling Shear Strength Properties of Cross Laminated Timber by Torsional Shear Tests and Bending Test

https://research.thinkwood.com/en/permalink/catalogue307
Year of Publication
2014
Topic
Mechanical Properties
Material
CLT (Cross-Laminated Timber)
Author
Li, Minghao
Lam, Frank
Li, Yuan
Year of Publication
2014
Format
Conference Paper
Material
CLT (Cross-Laminated Timber)
Topic
Mechanical Properties
Keywords
SPF
Polyurethane
Rolling Shear Strength
Torsional Shear Test
Bending Test
Conference
World Conference on Timber Engineering
Research Status
Complete
Notes
August 10-14, 2014, Quebec City, Canada
Summary
This paper presents a study on evaluating rolling shear (RS) strength properties of cross laminated timber (CLT) using torsional shear tests and bending tests. The CLT plates were manufactured with Spruce-Pine-Fir boards and glued with polyurethane adhesive. Two types of layups (3-layer and 5-layer) and two clamping pressures (0.1 MPa and 0.4 MPa) were studied. For the torsional shear tests, small shear block specimens were sampled from the CLT plates and the cross layers were processed to have an annular cross section. Strip specimens were simply sampled from the CLT plates for the bending tests. Based on the failure loads, RS strength properties were evaluated by torsional shear formula, composite beam formulae as well as detailed finite element models, respectively. It was found that the two different test methods yielded different average RS strength value for the same type of CLT specimens. The test results showed that the CLT specimens pressed with the higher clamping pressure had slightly higher average RS strength. The specimens with thinner cross layers also had higher RS strength than the specimens with thicker cross layers.
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Lateral Behaviour of Cross Laminated Timber Shear Walls under Reversed Cyclic Loads

https://research.thinkwood.com/en/permalink/catalogue198
Year of Publication
2015
Topic
Seismic
Connections
Material
CLT (Cross-Laminated Timber)
Application
Shear Walls
Author
Li, Minghao
Lam, Frank
Year of Publication
2015
Format
Conference Paper
Material
CLT (Cross-Laminated Timber)
Application
Shear Walls
Topic
Seismic
Connections
Keywords
Finite Element Model
Conference
Pacific Conference on Earthquake Engineering
Research Status
Complete
Notes
November 6-8, 2015, Sydney, Australia
Summary
Cross laminated timber (CLT) shear walls typically consist of solid engineered timber panels connected by metal hardware such as hold-downs, angle-brackets and others. Under seismic loads, the panel elements deform mainly in a rocking mode coupled with a sliding mode and small amount of in-plane bending/shear deformations. The connection system normally governs the lateral behaviour of CLT shear walls. This paper presents a finite element wall model CLTWALL2D to study CLT shear wall behaviour. The model consists of elastic orthotropic plate elements for the panels and nonlinear spring elements for the connections. Contact elements are also used for the panel-to-panel interactions. The nonlinear spring properties are represented by a subroutine called HYST that is able to model the strength and stiffness degradation and the pinching effect commonly observed in timber connections. The HYST parameters are calibrated by experimental data of CLT connections and embedded to the CLTWALL2D model. The wall model is validated against experimental data of a CLT shear wall test database. Parametric studies are then carried out to study the influence of gravity loads and vertical connection densities on the wall behaviour in terms of strength, stiffness, ductility, and energy dissipation.
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Torque Loading Tests on the Rolling Shear Strength of Cross-Laminated Timber

https://research.thinkwood.com/en/permalink/catalogue1416
Year of Publication
2016
Topic
Mechanical Properties
Material
CLT (Cross-Laminated Timber)
Author
Lam, Frank
Li, Yuan
Li, Minghao
Publisher
Springer Japan
Year of Publication
2016
Format
Journal Article
Material
CLT (Cross-Laminated Timber)
Topic
Mechanical Properties
Keywords
Rolling Shear Strength
Polyurethane
Mountain Pine Beetle
Torque Loading Tests
Failure Modes
Monte Carlo
Finite Element Model
Brittle Failure
Research Status
Complete
Series
Journal of Wood Science
Summary
In this study , torque loading tests on small shear blocks were performed to evaluate the rolling shear strength of cross-laminated timber (CLT). The CLT plates in the tests were manufactured with Mountain Pine Beetle-afflicted lumber boards and glued with polyurethane adhesive; two types of layups (five-layer and three-layer) with a clamping pressure 0.4 MPa were studied. The small block specimens were sampled from full-size CLT plates and the cross layers were processed to have an annular cross section. These specimens were tested under torque loading until brittle shear failure occurred in the middle cross layers. Based on the test results, the brittle shear failure in the specimens was evaluated by detailed finite element models to confirm the observed failure mode was rolling shear. Furthermore, a Monte Carlo simulation procedure was performed to investigate the occurrence probability of different shear failure modes in the tests considering the randomness of the rolling shear strength and longitudinal shear strength properties in the wood material. The result also suggested the probability of rolling shear failure is very high, which gives more confident proof that the specimens failed dominantly in rolling shear. It was also found that the torque loading test method yielded different rolling shear strength values compared to the previous research from short-span beam bending tests; such a difference may mainly be due to the different stressed volumes of material under different testing methods, which can be further investigated using the size effect theory in the future.
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Ductility and Overstrength of Dowelled LVL and CLT Connections Under Cyclic Loading

https://research.thinkwood.com/en/permalink/catalogue1504
Year of Publication
2016
Topic
Connections
Mechanical Properties
Material
CLT (Cross-Laminated Timber)
LVL (Laminated Veneer Lumber)
Author
Ottenhaus, Lisa-Mareike
Li, Minghao
Smith, Tobias
Quenneville, Pierre
Year of Publication
2016
Format
Conference Paper
Material
CLT (Cross-Laminated Timber)
LVL (Laminated Veneer Lumber)
Topic
Connections
Mechanical Properties
Keywords
Ductility
Overstrength
Cyclic Loading
Monotonic Loading
Dowels
Ductile Failure
Brittle Failure
Conference
World Conference on Timber Engineering
Research Status
Complete
Notes
August 22-25, 2016, Vienna, Austria p. 325-333
Summary
This paper presents an experimental study on ductility and overstrength of dowelled connections. Connection ductility and overstrength derived from monotonic testing are often used in timber connection design in the context of seismic loading, based on the assumption that these properties are similar under monotonic and cyclic loading. This assumption could possibly lead to non-conservative connection design. Therefore, it is necessary to quantify ductility and overstrength for cyclic loading and contrast them with their monotonic performance. For this purpose, monotonic and quasi-static cyclic experimental tests were performed on dowelled LVL and CLT connections. The experimental results were also compared with strength predictions from state-of-the-art analytical models in literature that were verified for ductile and brittle failure under monotonic loading. This work also allowed investigation into a generally applicable overstrength factor for push-pull loaded dowelled connections.
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Long-term Dynamic Characteristics of Pres-Lam Structures

https://research.thinkwood.com/en/permalink/catalogue1647
Year of Publication
2016
Topic
Design and Systems
Seismic
Material
LVL (Laminated Veneer Lumber)
Application
Wood Building Systems
Author
Smith, Tobias
Sarti, Francesco
Granello, Gabriele
Marshall, Jack
Buckton-Wishart, Victoria
Li, Minghao
Palermo, Alessandro
Pampanin, Stefano
Year of Publication
2016
Format
Conference Paper
Material
LVL (Laminated Veneer Lumber)
Application
Wood Building Systems
Topic
Design and Systems
Seismic
Keywords
Pres-Lam
Long-term
Dynamic Behaviour
Conference
World Conference on Timber Engineering
Research Status
Complete
Notes
August 22-25, 2016, Vienna, Austria p. 3462-3470
Summary
Pres-Lam timber structures are being adopted throughout New Zealand and around the world. This innovative method of timber construction combines the use of large engineered timber members with posttensioning cables/bars. The hybrid version of the Pres-Lam system improves seismic performance through the addition of external or internal steel reinforcing. While the post-tensioning provides re-centering properties, the steel increases energy dissipation from the system as well as increasing moment resistance. The design of these structures is performed to withstand high levels of seismic loading without damage to the structural system. Over time, the post-tensioning force being applied to the structural timber members causes them to reduce in length that has a subsequent impact on the quantity of force being applied. This paper looks at the dynamic characteristics of fundamental period and elastic damping of three recently constructed Pres-Lam buildings, investigating the influence of these losses on the dynamic characteristics. Following this a study of the performance under strong motion is performed. The paper concludes that although the losses in post-tensioning are clear they do not impact on the dynamic characteristics and have only a minor impact on strong motion response.
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Ductility of Large-scale Dowelled CLT Connections under Monotonic and Cyclic Loading

https://research.thinkwood.com/en/permalink/catalogue2254
Year of Publication
2017
Topic
Connections
Material
CLT (Cross-Laminated Timber)
LVL (Laminated Veneer Lumber)
Application
Shear Walls
Author
Ottenhaus, Lisa-Mareike
Li, Minghao
Smith, Tobias
Organization
University of Canterbury
Year of Publication
2017
Format
Conference Paper
Material
CLT (Cross-Laminated Timber)
LVL (Laminated Veneer Lumber)
Application
Shear Walls
Topic
Connections
Keywords
Dowel-Type Connections
Ductility
Particle Tracking Velocimetry
Tall Timber
Radiata Pine
Conference
Australian Earthquake Engineering Society Conference
Research Status
Complete
Summary
In the last decade, several tall timber buildings have been constructed in Europe, North America and Australasia. Often engineered wood products such as Cross Laminated Timber (CLT) are used in combination with strong connections to construct timber buildings exceeding 10 storeys. For tall timber buildings located in seismic areas it can be challenging to design strong yet ductile hold-downs in CLT shear walls. One common solution is to use dowelled connections with inserted steel plates. Design code calculation rules for timber connections are usually derived from smallscale testing assuming that strength and ductility properties can be extrapolated for larger connections in actual buildings. For CLT connections, fastener spacing requirements are derived in a similar manner under the general assumption that brittle failure modes can be prevented due to the reinforcing effect of cross-layers in CLT. In order to assess the validity of these assumptions, experiments were conducted on different layouts of small-scale and large-scale dowelled connections in CLT, Laminated Veneer Lumber (LVL) as well as a LVL-CLT hybrid, all made out of New Zealand Radiata pine. The tests comprised of 40 small and 12 large samples subjected to monotonic and cyclic loading. Strength and ductility were compared between the different connection sizes and layouts. For the large-scale connections, particle tracking velocimetry (PTV) was used for the first time to measure displacements.
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Evaluating Rolling Shear Strength Properties of Cross-Laminated Timber by Short-Span Bending Tests and Modified Planar Shear Tests

https://research.thinkwood.com/en/permalink/catalogue1403
Year of Publication
2017
Topic
Mechanical Properties
Material
CLT (Cross-Laminated Timber)
Author
Li, Minghao
Publisher
Springer Japan
Year of Publication
2017
Format
Journal Article
Material
CLT (Cross-Laminated Timber)
Topic
Mechanical Properties
Keywords
Rolling Shear Strength
Non-Edge-Glued
Pine
Thickness
Three Point Bending Test
Planar Shear Tests
Europe
Canada
Research Status
Complete
Series
Journal of Wood Science
Summary
This paper presents an experimental study on rolling shear (RS) strength properties of non-edge-glued cross-laminated timber (CLT) made out of New Zealand Radiata pine (Pinus radiata) structural timber. CLT specimens with 35 and 20 mm thick laminations were studied to evaluate the influence of lamination thickness on the RS strength of CLT. Short-span three-point bending tests were used to introduce high RS stresses in cross layers of CLT specimens and facilitate the RS failure mechanism. Modified planar shear tests from the conventional two-plate planar shear tests were also used to evaluate the RS strength properties. It was found that two test methods yielded comparable RS strength properties and the lamination thickness significantly affected RS strength of the CLT specimens. The test results also indicated that the recommended characteristic RS strength values of CLT products in Europe and Canada might be over conservative. Also, it might be more efficient to specify different RS strength values for CLT with different lamination thickness given the minimum width-to-depth ratio of laminations is satisfied.
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Application of Particle Tracking in Large Scale Timber Connection Testing

https://research.thinkwood.com/en/permalink/catalogue1943
Year of Publication
2018
Topic
Connections
Material
CLT (Cross-Laminated Timber)
Author
Ottenhaus, Lisa-Mareike
Li, Minghao
Nokes, Roger
Year of Publication
2018
Format
Conference Paper
Material
CLT (Cross-Laminated Timber)
Topic
Connections
Keywords
Particle Tracking Velocimetry
Digital Image Correlation
Conference
World Conference on Timber Engineering
Research Status
Complete
Notes
August 20-23, 2018, Seoul, Republic of Korea
Summary
Particle Tracking Velocimetry (PTV) is a quantitative field measuring technique originally designed to track individual particles in fluid flows. In this study, PTV was applied for the first time in the context of large scale timber connection testing. The suitability of PTV in structural applications was assessed by tracking the attachment points of string potentiometers and comparing the PTV displacements to those obtained by the potentiometers. Furthermore, it was found that PTV was able to capture crack growth and compute the resulting displacement field in the connection area.
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Mode Cross-Over and Ductility of Dowelled LVL and CLT Connections under Monotonic and Cyclic Loading

https://research.thinkwood.com/en/permalink/catalogue1228
Year of Publication
2018
Topic
Mechanical Properties
Connections
Material
CLT (Cross-Laminated Timber)
LVL (Laminated Veneer Lumber)
Author
Ottenhaus, Lisa-Mareike
Li, Minghao
Smith, Tobias
Quenneville, Pierre
Publisher
American Society of Civil Engineers
Year of Publication
2018
Format
Journal Article
Material
CLT (Cross-Laminated Timber)
LVL (Laminated Veneer Lumber)
Topic
Mechanical Properties
Connections
Keywords
Steel Dowels
Steel Plates
Ductility
Brittle
Monotonic Loading
Cyclic Loading
Research Status
Complete
Series
Journal of Structural Engineering
Summary
This paper presents an experimental study on dowelled connections in Cross Laminated Timber (CLT) and Laminated Veneer Lumber (LVL) using 20 mm mild steel dowels and internal steel plates. Connections designed to fail in brittle row shear and group tear-out were tested under monotonic loading to assess the validity of analytical models from literature and code provisions. Connections designed to provide non-linearity before failure and thus produce ductility were tested under both monotonic and cyclic loading to study the influence of cyclic loading on ductility and the possibility of mode cross-over. It was found that cross layers in CLT improve ductility. Furthermore, mode cross-over from ductile response to brittle failure was observed in both CLT and LVL connections. Nevertheless, a good amount of ductility was achieved in all layouts (except the LVL connections designed for group tear-out failure) before cross-over to brittle failure occurred.
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Seismic Performance Assessment of Steel Frame Infilled with Prefabricated Wood Shear Walls

https://research.thinkwood.com/en/permalink/catalogue1313
Year of Publication
2018
Topic
Seismic
Material
Light Frame (Lumber+Panels)
Application
Shear Walls
Hybrid Building Systems
Author
Li, Zheng
He, Minjuan
Wang, Xijun
Li, Minghao
Publisher
ScienceDirect
Year of Publication
2018
Format
Journal Article
Material
Light Frame (Lumber+Panels)
Application
Shear Walls
Hybrid Building Systems
Topic
Seismic
Keywords
Timber-Steel Hybrid
Seismic Performance
Multi-Story
Numerical Model
Damage
Stiffness
Nonlinear Time History Analysis
Research Status
Complete
Series
Journal of Constructional Steel Research
Summary
Steel-timber hybrid structural systems offer a modern solution for building multi-story structures with more environmentally-friendly features. This paper presents a comprehensive seismic performance assessment for a kind of multi-story steel-timber hybrid structure. In such a hybrid structure, steel moment resisting frames are infilled with prefabricated light wood frame shear walls to serve as the lateral load resisting system (LLRS). In this paper, drift-based performance objectives under various seismic hazard levels were proposed based on experimental observations. Then, a numerical model of the hybrid structure considering damage accumulation and stiffness degradation was developed and verified by experimental results, and nonlinear time-history analyses were conducted to establish a database of seismic responses. The numerical results further serve as a technical basis for estimating the structure's fundamental period and evaluating post-yielding behavior and failure probabilities of the hybrid structure under various seismic hazard levels. A load sharing parameter was defined to describe the wall-frame lateral force distribution, and a formula was proposed and calibrated by the time-history analytical results to estimate the load sharing parameter. Moreover, earthquake-induced non-structural damage and residual deformation were also evaluated, showing that if designed properly, desirable seismic performance with acceptable repair effort can be obtained for the proposed steel-timber hybrid structural system.
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17 records – page 1 of 2.