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171 records – page 1 of 18.

Analysis and enhancement of the new Eurocode 5 formulations for the lateral elastic deformation of LTF and CLT walls

https://research.thinkwood.com/en/permalink/catalogue3311
Year of Publication
2023
Topic
Mechanical Properties
Design and Systems
Material
CLT (Cross-Laminated Timber)
Author
Aloisio, Angelo
Boggian, Francesco
Sævareid, Håkon Østraat
Bjørkedal, Johan
Tomasi, Roberto
Organization
Norwegian University of Life Sciences
Università degli Studi di Trento
Università degli Studi dell’Aquila
Publisher
Elsevier
Year of Publication
2023
Format
Journal Article
Material
CLT (Cross-Laminated Timber)
Topic
Mechanical Properties
Design and Systems
Keywords
Light Timber Frames
Lateral Deformation
Shear Walls
Eurocode 5
Finite Element Modelling
Research Status
Complete
Series
Structures
Summary
This paper analyses the analytical formulations for the lateral elastic deformation of Light Timber Framed (LTF) and Cross-Laminated Timber (CLT) shear walls according to the new Eurocode 5 (EC5) proposal. Finite Element (FE) models and the Standard predictions are compared by emphasizing the role of each deformation contribution. A total of 1830 comparisons between analytical and numerical estimations are carried out by exploiting the Application Programming Interface of SAP2000 to modify the FE model parameters automatically. The parametric analyses proved that the numerical and analytical predictions are pretty consistent. Furthermore, in both LTF and CLT shear walls, the estimates for in-plane shear and rigid body sliding are in excellent agreement. Conversely, the analytical formulas for kinematic rocking are generally conservative for LTF and monolithic CLT shear walls, with an approximate 18%–19% discrepancy. The analytical expressions of the upcoming EC5 perfectly match the numerical model for segmented CLT shear walls under lateral forces and no vertical load. However, the presence of the vertical load determines a significant bias. Additionally, the predictions for bending deformations are not in good agreement. Therefore, the paper discusses possible enhancements for the equations proposed in the next generation of Eurocodes for the rocking deformation of segmented CLT walls to better conform with FE predictions.
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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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Dynamic testing and numerical modelling of a pedestrian timber bridge at different construction stages

https://research.thinkwood.com/en/permalink/catalogue3344
Year of Publication
2023
Topic
Acoustics and Vibration
Material
Glulam (Glue-Laminated Timber)
Application
Bridges and Spans
Author
Bergenudd, Jens
Battini, Jean-Marc
Crocetti, Roberto
Pacoste, Costin
Organization
KTH royal institute of technology
Publisher
Elsevier
Year of Publication
2023
Format
Journal Article
Material
Glulam (Glue-Laminated Timber)
Application
Bridges and Spans
Topic
Acoustics and Vibration
Keywords
Pedestrian Bridge
Railings
Asphalt
Dynamic Analysis
Finite Element Modelling
Research Status
Complete
Series
Engineering Structures
Summary
This article studies the dynamic properties of a single span pedestrian timber bridge by in-situ testing and numerical modelling. The in-situ dynamic tests are performed at four different construction stages: (1) on only the timber structure, (2) on the timber structure with the railings, (3) on the timber structure with railings and an asphalt layer during warm conditions and (4) same as stage 3 but during cold conditions. Finite element models for the four construction stages are thereafter implemented and calibrated against the experimental results. The purpose of the study is to better understand how the different parts of the bridge contribute to the overall dynamic properties. The finite element analysis at stage 1 shows that longitudinal springs must be introduced at the supports of the bridge to get accurate results. The experimental results at stage 2 show that the railings contributes to 10% of both the stiffness and mass of the bridge. A shell model of the railings is implemented and calibrated in order to fit with the experimental results. The resonance frequencies decrease with 10–20% at stage 3 compared to stage 2. At stage 3 it is sufficient to introduce the asphalt as an additional mass in the finite element model. For that, a shell layer with surface elements is the best approach. The resonance frequencies increase with 15–30% between warm (stage 3) and cold conditions (stage 4). The stiffness of the asphalt therefore needs to be considered at stage 4. The continuity of the asphalt layer could also increase the overall stiffness of the bridge. The damping ratios increase at all construction stages. They are around 2% at warm conditions and around 2.5% at cold conditions for the finished bridge.
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Birch plywood as gusset plates in glulam frame via mechanical connectors: A combined experimental and numerical study

https://research.thinkwood.com/en/permalink/catalogue3348
Year of Publication
2023
Topic
Connections
Mechanical Properties
Material
Glulam (Glue-Laminated Timber)
Author
Wang, Yue
Wang, Tianxiang
Persson, Pontus
Hedlund, Patrik
Crocetti, Roberto
Wålinder, Magnus
Organization
KTH royal institute of technology
Publisher
Elsevier
Year of Publication
2023
Format
Journal Article
Material
Glulam (Glue-Laminated Timber)
Topic
Connections
Mechanical Properties
Keywords
Birch Plywood
Gusset Plate
Finite Element Method
Research Status
Complete
Series
Journal of Building Engineering
Summary
Birch is a short-lived hardwood species widespread in the Northern Hemisphere. Plywood made from birch has superior mechanical properties compared with that made from most softwoods, which makes it suitable for structural application. In this study, the feasibility of using birch plywood as gusset plates in timber-timber connections is presented. Test frames consisting of birch plywood gussets and glulam beams connected by nails were built and tested. A 2D analytical model based on truss theory and a 3D finite element model were proposed and constructed. Both models showed satisfactory agreements with the test results in terms of stiffness and strength. Tensile failure on the birch plywood gussets along the outermost row of nail holes was observed in the experiment. The observed failure modes and the stress distributions in the 3D numerical model suggest that the spreading angle (Whitmore effective width) theory should be considered in the design phase of birch plywood gusset plates. Besides, a modified spreading angle theory is proposed to both approximate the stress distribution and predict the load-bearing capacity.
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Structural Behaviour of Aluminium–Timber Composite Beams with Partial Shear Connections

https://research.thinkwood.com/en/permalink/catalogue3388
Year of Publication
2023
Topic
Mechanical Properties
Material
LVL (Laminated Veneer Lumber)
Application
Beams
Author
Chybinski, Marcin
Polus, Lukasz
Organization
Poznan University of Technology
Publisher
MDPI
Year of Publication
2023
Format
Journal Article
Material
LVL (Laminated Veneer Lumber)
Application
Beams
Topic
Mechanical Properties
Keywords
Aluminium-Timber Composite Beams
Partial Shear Connection
Screws
Bending Test
Finite Element Method
Research Status
Complete
Series
Applied Sciences
Summary
In this paper, the short-term behaviour of innovative aluminium–timber composite beams was investigated. Laminated veneer lumber panels were attached to aluminium beams with screws. Recently conducted theoretical, experimental, and numerical investigations have focused on aluminium–timber composite beams with almost full shear connections. However, no experiments on aluminium–timber composite beams with partial shear connections have yet been conducted. For this reason, composite action in composite beams with different screw spacing was studied in this paper. Four-point bending tests were performed on aluminium–timber composite beams with different screw spacing to study their structural behaviour (ultimate load, mode of failure, load versus deflection response, load versus slip response, and short-term stiffness). The method used for steel–concrete composite beams with partial shear connection was adopted to estimate the load bearing capacity of the investigated aluminium–timber composite beams. The resistance to sagging bending of the aluminium–timber composite beams with partial shear connections from the theoretical analyses differed by 6–16% from the resistance in the laboratory tests. In addition, four 2D numerical models of the composite beams were developed. One model reflected the behaviour of the composite beam with full shear connection. The remaining models represented the composite beams with partial shear connections and were verified against the laboratory test results. Laminated veneer lumber was modelled as an orthotropic material and its failure was captured using the Hashin damage model. The resistance to sagging bending of the aluminium–timber composite beams with partial shear connections from the numerical analyses were only 3–6% lower than the one from the experiments.
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Modeling approach to estimate the bending strength and failure mechanisms of glued laminated timber beams

https://research.thinkwood.com/en/permalink/catalogue2939
Year of Publication
2022
Topic
Mechanical Properties
Material
Glulam (Glue-Laminated Timber)
Application
Beams
Author
Vida, Christoffer
Lukacevic, Markus
Eberhardsteiner, Josef
Füssl, Josef
Organization
TU Wien
Publisher
Elsevier
Year of Publication
2022
Format
Journal Article
Material
Glulam (Glue-Laminated Timber)
Application
Beams
Topic
Mechanical Properties
Keywords
Extended Finite Element Method
Bending Strength
Size Effect
Laminating Effect
Failure Mechanism
Research Status
Complete
Series
Engineering Structures
Summary
The numerical simulation of four-point bending tests on glued laminated timber (GLT) beams requires an adequate description of the material behavior and of relevant failure mechanisms. The wooden lamellas, building up the GLT element, include knots, as a result of the natural tree growth process, which significantly affect the mechanical behavior. The variability of the morphology and arrangement of these knots lead to a large fluctuation, especially of strength properties, along the wooden lamellas. This leads to complex and, in general, quite brittle structural failure mechanisms of the GLT element. Such failure mechanisms can numerically be described with discrete cracks, using the framework of the extended finite element method (XFEM) for cracks without predefined positions or cohesive surfaces for cracks with predefined positions. In this work, a modeling approach to reliably estimate the bending strength and failure mechanisms of GLT beams subjected to four-point bending tests is proposed. Herein, the approach is validated by simulating replications of experimentally tested GLT beams of two beam sizes and strength classes, where each knot group is considered as a section with reduced individual stiffness and strength in exactly the same position as in the real beam. The results show that the application of quasi-brittle material failure may still result in a brittle global failure of GLT beams. The present study exemplarily shows how valuable insight into progressive failure processes can be gained by allowing the formation of continuous crack patterns. Moreover, a refined consideration of the knot geometries with such sophisticated realizations of discrete cracks may be able to simulate the actual failure mechanisms even more precisely.
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Study on the strength of glued laminated timber beams with round holes: proposal of the design formula for the splitting strength

https://research.thinkwood.com/en/permalink/catalogue2946
Year of Publication
2022
Topic
Mechanical Properties
Material
Glulam (Glue-Laminated Timber)
Application
Beams
Author
Okamoto, Shigefumi
Akiyama, Nobuhiko
Araki, Yasuhiro
Aoki, Kenji
Inayama, Masahiro
Organization
Osaka City University
Publisher
Springer
Year of Publication
2022
Format
Journal Article
Material
Glulam (Glue-Laminated Timber)
Application
Beams
Topic
Mechanical Properties
Keywords
Round Hole
Splitting
Finite Element Method (FEM)
Design Formula
Research Status
Complete
Series
Journal of Wood Science
Summary
When a glued laminated timber (GLT) beam with a round hole is subjected to a shear force and bending moment, the hole will crack and fail due to a large tensile stress perpendicular to the grain and shear stresses. If the stresses acting on the hole are known, it is possible to estimate the fracture load. However, it is necessary to obtain the stresses acting on the hole by finite element analysis, which is very time consuming. In this study, to easily estimate the fracture load, we proposed a formula to estimate the bearing capacity at the time of a hole fracture by obtaining the stress acting on the hole through fnite element analysis and an approximate formula. The validity of the proposed formula was verifed using the existing experimental data of a GLT beam. As a result, it was confrmed that the proposed equation can estimate the fracture load of GLT beams in Japan and that the proposed equation can estimate the fracture load of GLT beams in countries other than Japan with some accuracy.
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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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Effect of Layer Arrangement on Bending Strength of Cross-Laminated Timber (CLT) Manufactured from Poplar (Populus deltoides L.)

https://research.thinkwood.com/en/permalink/catalogue3019
Year of Publication
2022
Topic
Mechanical Properties
Material
CLT (Cross-Laminated Timber)
Author
Haftkhani, Akbar Rostampour
Hematabadi, Hojat
Organization
University of Mohaghegh Ardabili
University of Technical & Vocational
Editor
Zhou, Binzhong
Publisher
MDPI
Year of Publication
2022
Format
Journal Article
Material
CLT (Cross-Laminated Timber)
Topic
Mechanical Properties
Keywords
Poplar
Bending Properties
Layer Configuration
Shear Analogy Method
Finite Element Method (FEM)
Research Status
Complete
Series
Buildings
Summary
This study aimed to investigate the effect of layer arrangement on bending properties of CLT panels made from poplar (Populus deltoides L.). A total of 20 three-layer CLT panels with the same dimensions of 1300 × 360 × 48 mm3 (Length, Width, Thickness) were fabricated in five configurations: 0/30/0, 0/45/0, 0/90/0, 45/0/45, and 45/45/45. The apparent modulus of elasticity (MOEapp), modulus of rupture (MOR) and apparent bending stiffness (EIapp) values in major and minor axes of CLT panels were calculated using experimental bending testing. In the major axis, the highest values of MOR, MOEapp, and EIapp were obtained from the 0/30/0 arrangement, while the least values resulted from the arrangements of 90/60/90 and 90/45/90 in the minor axis. Besides, in all arrangements, the average of the experimental apparent bending stiffness values (EIapp,exp) of specimens was higher than that of the shear analogy apparent bending stiffness values (EIapp,shear). The bending and shear stress distribution values over the cross section of samples were also estimated using the finite element method. Moreover, the numerical apparent bending stiffness (EIapp,fem) values of samples were compared to experimental apparent bending stiffness (EIapp,exp) values. Based on experimental and finite element method results, in all groups of layer arrangements, the EIapp,fem values concurred well with the EIapp,exp values.
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Seismic performance evaluation of innovative balloon type CLT rocking shear walls

https://research.thinkwood.com/en/permalink/catalogue3133
Year of Publication
2022
Topic
Seismic
Material
CLT (Cross-Laminated Timber)
Application
Shear Walls
Author
Yang, T.Y.
Lepine-Lacroix, S.
Guerrero, J.A. Ramos
McFadden, J.B.W.
Al-Janabi, M.A.Q.
Organization
The University of British Columbia
National Research Council Canada
Al-Nahrain University
Publisher
Elsevier
Year of Publication
2022
Format
Journal Article
Material
CLT (Cross-Laminated Timber)
Application
Shear Walls
Topic
Seismic
Keywords
Rocking Shear Walls
CLT Shear Walls
Seismic Performance
Nonlinear Finite Element Model
Research Status
Complete
Series
Resilient Cities and Structures
Summary
Balloon type cross laminated timber (CLT) rocking shear walls are a novel seismic force resisting system. In this paper, the seismic performance of four 12-story balloon type CLT rocking shear walls, designed by a structural engineering firm located in Vancouver (Canada) using the performance-based design procedure outlined in the technical guideline published by the Canadian Construction Materials center (CCMC)/National Research Council Canada (NRC), is assessed. The seismic performance of the prototype CLT rocking shear walls was investigated using nonlinear time history analyses. Robust nonlinear finite element models were developed using OpenSees and the nonlinear behavior of the displacement-controlled components was calibrated using available experimental data. A detailed site-specific hazard analysis was conducted and sets of ground motions suitable for the prototype buildings were selected. The ground motions were used in a series of incremental dynamic analyses (IDAs) to quantify the adjustable collapse margin ratio (ACMR) of the prototype balloon type CLT rocking shear walls. The results show that the prototype balloon type CLT rocking shear walls designed using the performance-based design procedure outlined in the CCMC/NRC technical guideline have sufficient ACMR when compared to the acceptable limits recommended by FEMA P695.
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171 records – page 1 of 18.