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44 records – page 1 of 5.

Moisture Induced Stresses in Glulam: Effect of Cross Section Geometry and Screw Reinforcement

https://research.thinkwood.com/en/permalink/catalogue176
Year of Publication
2012
Topic
Mechanical Properties
Moisture
Material
Glulam (Glue-Laminated Timber)
Application
Beams
Author
Angst-Nicollier, Vanessa
Organization
Norwegian University of Science and Technology
Year of Publication
2012
Format
Thesis
Material
Glulam (Glue-Laminated Timber)
Application
Beams
Topic
Mechanical Properties
Moisture
Keywords
Moisture Induced Stress
Mechanosorption
Numerical model
Tensile Strength
Tensile Stress
Load Bearing Capacity
Self-Tapping Screws
Climate
Research Status
Complete
Summary
This thesis presents a state of the art on moisture induced stresses in glulam, complemented with own findings. These are covered in detail in the appended papers. The first objective was to find a suitable model to describe moisture induced stresses, in particular with respect to mechanosorption. A review of existing models led to the conclusion that the selection of correct material parameters is more critical to obtain reliable results than the formulation of the mechanosorption model. A series of laboratory tests was thus performed in order to determine the parameters required for the model and to experimentally measure moisture induced stresses in glulam subjected to one dimensional wetting/drying. Special attention was paid to using glulam from the same batch for all the experimental measurements in order to calibrate the numerical model reliably. The results of the experiments confirmed that moisture induced stresses are larger during wetting than during drying, and that the tensile stresses could clearly exceed the characteristic tensile strength perpendicular to grain.
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In-Plane Stiffness of Cross-Laminated Timber Floors

https://research.thinkwood.com/en/permalink/catalogue1263
Year of Publication
2012
Topic
Mechanical Properties
Material
CLT (Cross-Laminated Timber)
Application
Floors
Shear Walls
Author
Ashtari, Sepideh
Organization
University of British Columbia
Year of Publication
2012
Format
Thesis
Material
CLT (Cross-Laminated Timber)
Application
Floors
Shear Walls
Topic
Mechanical Properties
Keywords
In-Plane Stiffness
Numerical Model
Self-Tapping Screws
Panel-to-Panel
In-Plane Shear Modulus
Stiffness
Research Status
Complete
Summary
This study investigates the in-plane stiffness of CLT floor diaphragms and addresses the lateral load distribution within buildings containing CLT floors. In practice, it is common to assume the floor diaphragm as either flexible or rigid, and distribute the lateral load according to simple hand calculations methods. Here, the applicability of theses assumption to CLT floor diaphragms is investigated. There is limited number of studies on the subject of in-plane behaviour of CLT diaphragms in the literature. Many of these studies involve testing of the panels or the connections utilized in CLT diaphragms. This study employs numerical modeling as a tool to address the in-plane behaviour of CLT diaphragms. The approach taken to develop the numerical models in this thesis has not been applied so far to CLT floor diaphragms. Detailed 2D finite element models of selective CLT floor diaphragm configurations are generated and analysed in ANSYS. The models contain a smeared panel-to-panel connection model, which is calibrated with test data of a special type of CLT connection with self-tapping wood screws. The floor models are then extended to building models by adding shearwalls, and the lateral load distribution is studied for each building model. A design flowchart is also developed to aid engineers in finding the lateral load distribution for any type of building in a systematic approach. By a parametric study, the most influential parameters affecting the in-plane behaviour of CLT floor diaphragm and the lateral load distribution are identified. The main parameters include the response of the CLT panel-to-panel connections, the in-plane shear modulus of CLT panels, the stiffness of shearwalls, and the floor diaphragm configuration. It was found that the applicability of flexible or rigid diaphragm assumptions is primarily dependent on the relative stiffness of the CLT floor diaphragm and the shearwalls.
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Seismic Retrofit of Soft-Story Woodframe Buildings using Cross Laminated Timbers

https://research.thinkwood.com/en/permalink/catalogue215
Year of Publication
2013
Topic
Seismic
Material
CLT (Cross-Laminated Timber)
Light Frame (Lumber+Panels)
Application
Wood Building Systems
Author
van de Lindt, John
Bahmani, Pouria
Gershfeld, Mikhail
Kandukuri, Giraj
Rammer, Douglas
Pei, Shiling
Year of Publication
2013
Format
Journal Article
Material
CLT (Cross-Laminated Timber)
Light Frame (Lumber+Panels)
Application
Wood Building Systems
Topic
Seismic
Keywords
Retrofit
Soft-Story
Numerical model
US
Full Scale
Conference
International Structural Engineering and Construction Conference
Research Status
Complete
Notes
June 18-23 2013, Hononlulu, Hawaii, USA
Summary
Woodframe construction in the United States has, by and large, performed well with regard to life-safety over the decades. However, older woodframe buildings, typically two- to four-stories in Northern and Southern California (as well as elsewhere), may have a soft and weak story which makes them susceptible to collapse during even moderate shaking. These buildings often have parking and/or open fronts and very few interior walls resulting in first story stiffness that is sometimes as low as 30% to 40% of the story above. Figure 1 shows a photo of a soft-story building undergoing retrofit in San Francisco. Most local jurisdictions recognize this as a disaster preparedness problem and have beenactively developing various ordinances and mitigation plans to address this threat. Some of the most visible efforts are taking place in San Francisco, Los Angeles, San Jose and other major metropolitan areas in the United States that have high seismic vulnerability. In 2008, the San Francisco Department of Building Inspection and the Applied Technology Council initiated the Community Action Plan for Seismic Safety (CAPSS) project with the main goal of identifying possible action plans for reducing earthquake risks in existing buildings. According to the CAPSS study, 43 to 80 percent of the multistory woodframe buildings in San Francisco will be deemed unsafe after a magnitude 7.2 earthquake and a quarter of these buildings would be expected to collapse.
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FE Analysis of CLT Panel Subjected to Torsion and Verified by DIC

https://research.thinkwood.com/en/permalink/catalogue485
Year of Publication
2013
Topic
Mechanical Properties
Material
CLT (Cross-Laminated Timber)
Author
Sebera, Václav
Muszynski, Lech
Tippner, Jan
Noyel, Melanie
Pisaneschi, Thomas
Sundberg, Benjamin
Publisher
Springer Netherlands
Year of Publication
2013
Format
Journal Article
Material
CLT (Cross-Laminated Timber)
Topic
Mechanical Properties
Keywords
Finite Element Model
Torsion
Numerical model
Digital Image Correlation
Research Status
Complete
Series
Materials and Structures
Summary
The goal of this study was to analyze behavior of the cross-laminated timber (CLT) panel subjected to torsion and develop an efficient procedure for quick verification of numerical model of CLT that subsequently may be used for virtual prototyping of non-standard CLT products. Study used both experiments based on optical measurement using digital image correlation (DIC) and numerical modeling by means of finite element method (FEM). A physical torsion test of the CLT panel was first analyzed in terms of a displacement field that was computed on its surface. The FE simulation of the torsion test followed real boundary conditions and was carried out with use of 2 geometrically different FE models of the CLT. The first FE model did not take into account edgebonding of the lamellas, the second one demonstrated alternative manufacturing option by considering the lamellas’ edge-bonding. The experiment and FE simulations were mutually compared based on displacement paths created on the panel surface. Results showed that the presented procedure offers relatively easy way of verification of FE analyses of CLT. FE model with edge-bonding of lamellas exhibited higher stiffness and higher relative error to DIC measurement than FE model without edge-bonding. Edge-bonding of lamellas introduces influential factor in FE modeling of CLT and should be omitted for accurate and realistic FE analyses of their behavior. Study also showed that lack of orthotropic properties of Oregon hybrid poplar can be in FEA sufficiently substituted by using cottonwood properties. Combining the DIC measurement and FEM in the analysis of the CLT is favorable since it offers an full-field validation of numerical models, which can be subsequently used for virtual prototyping.
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Experimental and Numerical Analyses of New Massive Wooden Shear-Wall Systems

https://research.thinkwood.com/en/permalink/catalogue93
Year of Publication
2014
Topic
Seismic
Material
CLT (Cross-Laminated Timber)
Application
Shear Walls
Author
Pozza, Luca
Scotta, Roberto
Trutalli, Davide
Pinna, Mario
Polastri, Andrea
Bertoni, Paolo
Publisher
MDPI
Year of Publication
2014
Format
Journal Article
Material
CLT (Cross-Laminated Timber)
Application
Shear Walls
Topic
Seismic
Keywords
Quasi-Static
Cyclic Loading Tests
Numerical model
Ductility
Eurocode 8
Behaviour Factor
Dissipative Capacity
Research Status
Complete
Series
Buildings
Summary
Three innovative massive wooden shear-wall systems (Cross-Laminated-Glued Wall, Cross-Laminated-Stapled Wall, Layered Wall with dovetail inserts) were tested and their structural behaviour under seismic action was assessed with numerical simulations. The wall specimens differ mainly in the method used to assemble the layers of timber boards composing them. Quasi-static cyclic loading tests were carried out and then reproduced with a non-linear numerical model calibrated on the test results to estimate the most appropriate behaviour factor for each system. Non-linear dynamic simulations of 15 artificially generated seismic shocks showed that these systems have good dissipative capacity when correctly designed and that they can be assigned to the medium ductility class of Eurocode 8. This work also shows the influence of deformations in wooden panels and base connectors on the behaviour factor and dissipative capacity of the system.
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Numerical Simulation for the Seismic Behaviour of Mid-Rise CLT Shear Walls with Coupling Beams

https://research.thinkwood.com/en/permalink/catalogue200
Year of Publication
2014
Topic
Seismic
Material
CLT (Cross-Laminated Timber)
Application
Shear Walls
Wood Building Systems
Author
Liu, Jingjing
Lam, Frank
Year of Publication
2014
Format
Conference Paper
Material
CLT (Cross-Laminated Timber)
Application
Shear Walls
Wood Building Systems
Topic
Seismic
Keywords
Deflection
Degradation
Energy Dissipation
Force
Resistance
Stiffness
Strength
Numerical model
Conference
World Conference on Timber Engineering
Research Status
Complete
Notes
August 10-14, 2014, Quebec City, Canada
Summary
In this paper, an innovative type of mid-rise Cross Laminated Timber shear walls with coupling beams was designed. The 5-layer CLT panels were continuous along the height. Hold-downs and angle brackets were installed at the bottom of the panels. Coupling beams with energy dissipation devices were used to decrease the deformation and internal forces of the walls, providing adequate stiffness and strength. A numerical model was developed in OpenSees for a six storey prototype to investigate its seismic behaviour with different configurations. Strength degradation, stiffness degradation, and pinching effect were considered in the connection models. The structural performance was evaluated through a series of static and transient analyses. The simulation results indicated adequate lateral resistance and deformation capacity of this structural type. This study will lead to more application of large size CLT panels in multi-storey CLT buildings as lateral resistant systems.
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Glulam Beams with Holes

https://research.thinkwood.com/en/permalink/catalogue211
Year of Publication
2014
Topic
Mechanical Properties
Material
Glulam (Glue-Laminated Timber)
Application
Beams
Author
Jelec, Mario
Varevac, Damir
Zovkic, Jurko
Organization
University of Osijek
Year of Publication
2014
Format
Journal Article
Material
Glulam (Glue-Laminated Timber)
Application
Beams
Topic
Mechanical Properties
Keywords
Finite Element Model
Openings
Numerical model
Stress Distribution
Research Status
Complete
Series
e-GFOS
Summary
This paper provides a systematic review of research on glued laminated timber beams with circular and rectangular openings. Experiments on girders with unreinforced openings varied several parameters, including the girder span and shape, opening position and shape, and the relationship between the stress state near the opening and the ratio of opening size to girder size. We compare experimental results with recommendations given by DIN 1052:2004-08, DIN EN 1995-1-1/NA: 2010, prEN 1995-1-1: Final Draft, analytical expressions, and other relevant standards, as well as with the results of numerical models using the finite element method. Because of its myriad complexities and uncertainties, this area remains open for further research and for implementation of that research into practical design guidelines and rules.
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Investigation on Elements Presenting Cracks in Timber Structures

https://research.thinkwood.com/en/permalink/catalogue477
Year of Publication
2014
Topic
Mechanical Properties
Material
Glulam (Glue-Laminated Timber)
Author
Franke, Steffen
Magnière, Noëlie
Year of Publication
2014
Format
Conference Paper
Material
Glulam (Glue-Laminated Timber)
Topic
Mechanical Properties
Keywords
Cracks
Numerical Model
Stiffness
Load Carrying Capacity
Conference
World Conference on Timber Engineering
Research Status
Complete
Notes
August 10-14, 2014, Quebec City, Canada
Summary
Cracks in timber members influence the stiffness and load-carrying behaviour but only rudimentary rules are given to evaluate cracked members. Therefore, an investigation to gather information about the most frequent characteristics of cracked timber structures has been carried out. This investigation provides the main characteristics of both the timber elements and the crack distributions encountered. These main characteristics have then been used to define a numerical model in order to investigate the impact of cracks on the stiffness and load-carrying capacity of timber beams. Based on these results, the existing rules considering cracks in timber beams can be evaluated and new rules can be developed.
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Structural Characterization of Multi-Storey Buildings with CLT Cores

https://research.thinkwood.com/en/permalink/catalogue496
Year of Publication
2014
Topic
Seismic
Material
CLT (Cross-Laminated Timber)
Application
Wood Building Systems
Shear Walls
Author
Polastri, Andrea
Pozza, Luca
Trutalli, Davide
Scotta, Roberto
Smith, Ian
Year of Publication
2014
Format
Conference Paper
Material
CLT (Cross-Laminated Timber)
Application
Wood Building Systems
Shear Walls
Topic
Seismic
Keywords
Multi-Storey
Numerical model
Building Cores
Conference
World Conference on Timber Engineering
Research Status
Complete
Notes
August 10-14, 2014, Quebec City, Canada
Summary
The behaviour of multi-storey buildings braced with Cross-Laminated-Timber (CLT) cores and additional shear walls is examined based on numerical analyses of various 3-dimensional configurations. Two ways of calibrating numerical model are proposed according to codes and experimental test data respectively, including calibration of parameters that characterise connections between CLT panels in building cores and shear walls. Results of analyses of entire buildings are presented in terms of principal elastic periods, and base shear and up-lift forces. Discussion addresses primary issues associated with behaviour of such systems and modelling them.
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Performance of Semirigid Timber Frame with Lagscrewbolt Connections: Experimental, Analytical, and Numerical Model Results

https://research.thinkwood.com/en/permalink/catalogue201
Year of Publication
2015
Topic
Connections
Mechanical Properties
Material
Glulam (Glue-Laminated Timber)
Application
Beams
Author
Mori, Takuro
Nakatani, Makoto
Tesfamariam, Solomon
Publisher
Springer Berlin Heidelberg
Year of Publication
2015
Format
Journal Article
Material
Glulam (Glue-Laminated Timber)
Application
Beams
Topic
Connections
Mechanical Properties
Keywords
Lag Screws
Beam-to-Column
Moment Resistance
Stiffness
Finite Element Model
Analytical Model
Numerical Model
Research Status
Complete
Series
International Journal of Advanced Structural Engineering
Summary
This paper presents analytical and numerical models for semirigid timber frame with Lagscrewbolt (LSB) connections. A series of static and reverse cyclic experimental tests were carried out for different beam sizes (400, 500, and 600 mm depth) and column–base connections with different numbers of LSBs (4, 5, 8). For the beam–column connections, with increase in beam depth, moment resistance and stiffness values increased, and ductility factor reduced. For the column–base connection, with increase in the number of LSBs, the strength, stiffness, and ductility values increased. A material model available in OpenSees, Pinching4 hysteretic model, was calibrated for all connection test results. Finally, analytical model of the portal frame was developed and compared with the experimental test results. Overall, there was good agreement with the experimental test results, and the Pinching4 hysteretic model can readily be used for full-scale structural model.
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44 records – page 1 of 5.