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50 records – page 2 of 5.

Novel Internally LVL-Reinforced Glued Laminated Timber Beams with Large Holes

https://research.thinkwood.com/en/permalink/catalogue1303
Year of Publication
2018
Topic
Design and Systems
Mechanical Properties
Material
LVL (Laminated Veneer Lumber)
Glulam (Glue-Laminated Timber)
Application
Beams
Author
Aicher, Simon
Tapia, Cristóbal
Publisher
ScienceDirect
Year of Publication
2018
Format
Journal Article
Material
LVL (Laminated Veneer Lumber)
Glulam (Glue-Laminated Timber)
Application
Beams
Topic
Design and Systems
Mechanical Properties
Keywords
Holes
Reinforcement
Beech
Load Capacity
Research Status
Complete
Series
Construction and Building Materials
Summary
A novel timber composite is presented, consisting of glued laminated timber (GLT) from softwoods and intercalated cross-layered plates of laminated veneer lumber (LVL) made of hardwood species, specifically beech. The structure is especially suited for beams with multiple, large rectangular holes, where the LVL acts as a highly efficient internal reinforcement and contributes to a damage-tolerant ultimate load behavior. The load capacity of the composite beam is not induced by the stress concentrations at the corners of the hole, which, in contrast to generic GLT, lead to a sudden propagation of cracks and brittle failure. It is shown that the structure, including the holes, can be designed analytically in a transparent manner by using beam theory, a parallel system approach, and modifications from FEM analysis for the verification of tensile forces at the hole periphery. The composite, firstly used in a recent multi-story building in Australia, significantly improves the competitiveness of timber in building works, which have been limited to steel and reinforced concrete structures.
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Flexural Behavior of FRP and Steel Reinforced Glulam Beams: Experimental and Theoretical Evaluation

https://research.thinkwood.com/en/permalink/catalogue171
Year of Publication
2016
Topic
Design and Systems
Mechanical Properties
Material
Glulam (Glue-Laminated Timber)
Application
Beams
Author
Yang, Huifeng
Liu, Weiqing
Lu, Weidong
Zhu, Shijun
Geng, Qifan
Publisher
ScienceDirect
Year of Publication
2016
Format
Journal Article
Material
Glulam (Glue-Laminated Timber)
Application
Beams
Topic
Design and Systems
Mechanical Properties
Keywords
Four Point Bending Test
Failure Mode
Fiber Reinforced Polymer
Flexural
Modulus of Rupture
Reinforcement
Research Status
Complete
Series
Construction and Building Materials
Notes
https://doi.org/10.1016/j.conbuildmat.2015.12.135
Summary
This paper describes an experimental test program and theoretical analysis which examines the reinforcing in flexure of glued laminated timber (glulam) beams using fiber reinforced polymer (FRP) and steel materials. A series of four-point bending tests were conducted till failure on both unreinforced and reinforced Douglas fir glulam beams in a simply-supported scheme. The focus of this research was to evaluate the effects of reinforcing materials, reinforcement ratio and arrangement on the flexural behavior. Test results showed that the flexural capacity, flexural global stiffness and timber tensile strain at failure were all improved considerably for reinforced timber beams when compared to the unreinforced control beams, in which the average improvement reached 56.3%, 27.5% and 49.4%, respectively. On the bases of the experimental results, a theoretical model was proposed to predict the flexural capacity and flexural stiffness of the reinforced timber beams. Most of the differences between theoretical and experimental results for both flexural capacity and flexural stiffness were within 10.0%, which showed a high accuracy of the proposed model. Subsequently a parametric analysis, which includes the axial stiffness ratio of reinforcement to timber, the relative location of tensile reinforcement, and the strength ratio of reinforced timber between flexural tension and compression, was undertaken to investigate the effects of the influential factors for both flexural capacity and flexural stiffness.
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Fully Reversible Reinforcement of Softwood Beams with Unbonded Composite Plates

https://research.thinkwood.com/en/permalink/catalogue210
Year of Publication
2016
Topic
Design and Systems
Mechanical Properties
Material
Glulam (Glue-Laminated Timber)
Application
Beams
Author
Borri, Antonio
Speranzini, Emanuela
Castori, Giulio
Corradi, Marco
Publisher
ScienceDirect
Year of Publication
2016
Format
Journal Article
Material
Glulam (Glue-Laminated Timber)
Application
Beams
Topic
Design and Systems
Mechanical Properties
Keywords
Failure
Flexural Tests
Glass Fiber Reinforced Polymer
Modulus of Rupture
Reinforcement
Softwood
finite element method
Numerical model
Research Status
Complete
Series
Composite Structures
Summary
In this paper, results of flexure tests aimed at improving the structural behavior of softwood beams reinforced with unglued composite plates and at developing an effective alternative to the use of organic resins are presented. The addition of modest ratios of GFRP (Glass Fiber Reinforced Polymer) composite strengthening can prevent tension failure in timber beams. However the application of organic matrices presents problems of reversibility, compatibility and durability with timber and poor performance at high temperatures. The increment in capacity and stiffness and the analysis of the failure modes is the central focus of this paper. The experimental campaign is dealing with a significant number of un-reinforced and reinforced beams strengthened with unbonded GFRP plates. A 3-dimensional finite element model is also presented for simulating the non-linear behavior of GFRP-reinforced softwood beams. The ability of the numerical model to reproduce experimental results for the load–deflection curves is validated.
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Static and Dynamic Properties of Retrofitted Timber Beams Using Glass Fiber Reinforced Polymers

https://research.thinkwood.com/en/permalink/catalogue797
Year of Publication
2016
Topic
Design and Systems
Mechanical Properties
Material
Solid-sawn Heavy Timber
Application
Beams
Author
Bru, David
Baeza, Francisco Javier
Varona, Francisco
García-Barba, Javier
Ivorra, Salvador
Publisher
Springer Netherlands
Year of Publication
2016
Format
Journal Article
Material
Solid-sawn Heavy Timber
Application
Beams
Topic
Design and Systems
Mechanical Properties
Keywords
Damping Ratio
Ductility
Natural Frequency
Glass Fiber Reinforced Polymer
Pine
Reinforcement
Static Properties
Dynamic Properties
Modal Analysis
Four Point Bending Test
Bending Strength
Research Status
Complete
Series
Materials and Structures
Summary
A study on the static and dynamic properties of sawn timber beams reinforced with glass fiber-reinforced polymer (GFRP) is reported in this paper. The experimental program is focused on the behavior of unidirectional wooden slabs, and the main objective is to fulfill the service state limit upon vibrations using GFRP when an architectonical retrofitting project is necessary. Two different typologies of reinforcement were evaluated on pine wood beams: one applied the composite only on the lower side of the beams, while the other also covered half of the beams depth. For the dynamic characterization, the natural frequency, damping ratio, and dynamic elastic modulus were measured using two different techniques: experimental modal analysis upon the whole beams; and bandwidth method using smaller samples of the same material. The static characterization consisted on four point bending tests, where elastic modulus, bending strength and ductility were assessed. The lower composite had better ductility and bending strength. On the other hand, the U-shaped laminate showed higher stiffness but also at a higher material cost. However, it allowed some ductility, i.e. compressive plasticity, even in the presence of hidden knots. Both dynamic techniques gave similar results and were capable of measuring the structure stiffness, even if short samples were used. Finally, the changes on dynamic properties because of the GFRP did not jeopardize the dynamic performance of the reinforced timber beams.
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Numerical Modelling of Glulam Beams Externally Reinforced with CFRP Plates

https://research.thinkwood.com/en/permalink/catalogue1624
Year of Publication
2016
Topic
Mechanical Properties
Material
Glulam (Glue-Laminated Timber)
Application
Beams
Author
Glišovic, Ivan
Pavlovic, Marko
Stevanovic, Boško
Todorovic, Marija
Year of Publication
2016
Format
Conference Paper
Material
Glulam (Glue-Laminated Timber)
Application
Beams
Topic
Mechanical Properties
Keywords
Bending Behaviour
CFRP
Finite Element Model
Load Deflection
Stiffness
Load Carrying Capacity
Strain
Reinforcement
Conference
World Conference on Timber Engineering
Research Status
Complete
Notes
August 22-25, 2016, Vienna, Austria p. 2634-2641
Summary
Timber beams can effectively be reinforced using externally bonded fibre reinforced polymer (FRP) composites. This paper describes a nonlinear 3-dimensional finite element model which was developed in order to accurately simulate the bending behaviour of unreinforced and carbon FRP plate reinforced glulam beams. The model incorporates suitable constitutive relationship for each material and utilises anisotropic plasticity theory for timber in compression. Failure of beams was modelled based on the maximum stress criterion. The results of the finite element analysis showed a good agreement with experimental findings for load-deflection behaviour, stiffness, ultimate load carrying capacity and strain profile distribution of unreinforced and reinforced beams. The proposed model can be used to examine the effect of different geometries or materials on the mechanical performance of reinforced system.
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Performance of Self-Tapping Screws and Threaded Steel Rods in Shear Reinforcement of Glulam Beams

https://research.thinkwood.com/en/permalink/catalogue1628
Year of Publication
2016
Topic
Connections
Mechanical Properties
Material
Glulam (Glue-Laminated Timber)
Application
Beams
Author
Jockwer, Robert
Steiger, René
Year of Publication
2016
Format
Conference Paper
Material
Glulam (Glue-Laminated Timber)
Application
Beams
Topic
Connections
Mechanical Properties
Keywords
Norway Spruce
Reinforcement
Self-Tapping Screws
Threaded Steel Rod
Stiffness
Strength
Load Carrying Capacity
Conference
World Conference on Timber Engineering
Research Status
Complete
Notes
August 22-25, 2016, Vienna, Austria p. 2813-2822
Summary
Norway spruce glulam beams with artificial horizontal slits of different length and depth were reinforced using self-tapping screws and threaded steel rods in order to restore their load-carrying capacity and stiffness. The study aimed at evaluating the effects of strength and stiffness of the applied reinforcing elements on the load-carrying capacity and stiffness of glulam beams after retrofitting. Self-tapping screws and threaded steel rods of different diameter have been evaluated in the study and different numbers of reinforcing elements have been applied. Shear failure of the beams with artificial slits of different depth was provoked in loading cycles with stepwise installation of the reinforcing elements in the beam parts failed in the preceding test. The reinforcing effect of the tested self-tapping screws and threaded steel rods reached and partly exceeded the estimated level calculated with selected analytical models. Unfavourable structural behaviour arose in some cases from crack opening during installation of the rods causing a very low initial stiffness. Comparison of test results to calculations of stiffness and load-carrying capacity of the reinforced beams applying the -method, the shear analogy method and a truss model revealed that the -method and the shear analogy method provided the best estimates of strength / stiffness of the reinforced beams.
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Viscoelastic Creep in Reinforced Glulam

https://research.thinkwood.com/en/permalink/catalogue1629
Year of Publication
2016
Topic
Mechanical Properties
Serviceability
Material
Glulam (Glue-Laminated Timber)
Application
Beams
Author
O’Ceallaigh, Conan
Sikora, Karol
McPolin, Daniel
Harte, Annette
Year of Publication
2016
Format
Conference Paper
Material
Glulam (Glue-Laminated Timber)
Application
Beams
Topic
Mechanical Properties
Serviceability
Keywords
Long-term
Loading
Climate
Spruce
Ireland
Reinforcement
BFRP
Stiffness
Flexural Testing
Creep
Conference
World Conference on Timber Engineering
Research Status
Complete
Notes
August 22-25, 2016, Vienna, Austria p. 2823-2831
Summary
The reinforcement of timber elements using fibre reinforced polymer (FRP) rods or plates is widely accepted as an effective method of increasing the strength and stiffness of members. The short-term behaviour of these reinforced members is relatively well understood, however, the long-term or creep behaviour of such members has received less attention. The objectives of the present work are to determine the long-term performance of reinforced timber beams under sustained loading and constant climate conditions. Timber is a viscoelastic material so its deformation response is a combination of both elastic and viscous components. This viscous creep component is defined as a deformation with time at constant stress and at constant environmental conditions. Sitka spruce is the most widely grown specie in Ireland and is the focus of this study. Glued Laminated (Glulam) beams were manufactured from Sitka spruce and a selected portion of them were reinforced with basalt-fibre reinforced polymer (BFRP) rods. The short-term flexural testing of these beams in their unreinforced and reinforced state demonstrated a significant increase in stiffness with a modest percentage reinforcement ratio. The long-term flexural testing required the design of a creep test frame to implement a constant stress of 8 MPa on the compression face of an equal proportion of unreinforced and reinforced beams. The long-term strain and deflection results for the first 52 weeks of testing are presented. The reinforcement was found to have an insignificant impact on the creep deflection but the maximum tensile creep strain was significantly reduced.
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Experimental Study on Lateral Resistance of Reinforced Glued-Laminated Timber Post and Beam Structures

https://research.thinkwood.com/en/permalink/catalogue1648
Year of Publication
2016
Topic
Seismic
Mechanical Properties
Material
Glulam (Glue-Laminated Timber)
Application
Beams
Author
Xiong, Haibei
Liu, Yingyang
Lam, Frank
Year of Publication
2016
Format
Conference Paper
Material
Glulam (Glue-Laminated Timber)
Application
Beams
Topic
Seismic
Mechanical Properties
Keywords
Cyclic Tests
Full Scale
Reinforcement
Lateral Resistance
Strength
Stiffness
Energy Dissipation
Self-Tapping Screws
FRP
Conference
World Conference on Timber Engineering
Research Status
Complete
Notes
August 22-25, 2016, Vienna, Austria p. 3471-3478
Summary
In order to study the lateral resistance of reinforced glued-laminated timber post and beam structures, nine cyclic tests on full-scale one-storey, one-bay timber post and beam construction specimens were carried out. Two reinforcement methods (wrapping fiber reinforced polymer (FRP) and implanting self-tapping screws) and two structural systems (simple frame and knee-braced frame) were considered in the experimental tests. Based on the experimental phenomena and test results, feasibility of the reinforcement was discussed, contribution between different methods was evaluated, and the seismic performances of the specimens were studied. Results showed that both the two reinforcement methods could restrain the development of crack, and recover the strength, stiffness and energy dissipation capacity. It also showed that the lateral resistance could be improved significantly when the failed simple frame retrofitted by reinforcing the joint and adding knee-brace, and this approach can be very practical in engineering.
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Holes in Glulam – Orientation and Design of Internal Reinforcements

https://research.thinkwood.com/en/permalink/catalogue1704
Year of Publication
2016
Topic
Mechanical Properties
Material
Glulam (Glue-Laminated Timber)
LVL (Laminated Veneer Lumber)
Author
Tapia, Cristóbal
Aicher, Simon
Year of Publication
2016
Format
Conference Paper
Material
Glulam (Glue-Laminated Timber)
LVL (Laminated Veneer Lumber)
Topic
Mechanical Properties
Keywords
Holes
Steel Rods
Reinforcement
Tensile Stresses
Shear Stresses
Eurocode 5
Conference
World Conference on Timber Engineering
Research Status
Complete
Notes
August 22-25, 2016, Vienna, Austria p. 4404-4411
Summary
The usage of holes in glulam and LVL beams is a common practice in timber constructions and requires in many cases the application of reinforcement. At present, Eurocode 5 does not contain design rules for holes, nor for their reinforcement, which are, however, regulated in the German National Annex to EC5. Although it has been proven that internal rod-like reinforcements improve the shear force capacity of a beam with holes, several problems still remain, particularly the inability to successfully reduce peak stresses at the periphery of the hole, especially shear stresses. Inclined internal steel rod reinforcements were studied and compared with vertically oriented rods, which is currently the only regulated application. The analysis revealed a reduction of both perpendicular to grain tensile stresses and shear stresses, which for the case of vertical rods are not reduced at all. A first attempt at the design of such inclined reinforcements was made by deriving an equation based on the results from FEM simulations. The design approach was then applied to an example case. Experimental verification of the theoretical observations is still necessary and ongoing, though a very promising approach for an improved internal reinforcement and its respective design can already be observed.
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Comparison of Verification and Reinforcement Concepts for Timber Beams with Large Round Holes

https://research.thinkwood.com/en/permalink/catalogue1714
Year of Publication
2016
Topic
Mechanical Properties
Material
CLT (Cross-Laminated Timber)
Glulam (Glue-Laminated Timber)
Application
Beams
Author
Dröscher, Julia
Augustin, Manfred
Schickhofer, Gerhard
Year of Publication
2016
Format
Conference Paper
Material
CLT (Cross-Laminated Timber)
Glulam (Glue-Laminated Timber)
Application
Beams
Topic
Mechanical Properties
Keywords
Reinforcement
Shear Stresses
Tensile Stresses
Load Carrying Capacity
Numerical Investigation
Analytical Investigation
Conference
World Conference on Timber Engineering
Research Status
Complete
Notes
August 22-25, 2016, Vienna, Austria p. 4529-4538
Summary
Within this paper a comparison of different reinforcement concepts for timber beams with round holes is carried out. Therefore currently applied standardized methods and two recently developed approaches are considered. By means of numerical and analytical investigations it becomes apparent that the analysed reinforcement methods divergent to those given in current standards have great potential: shear stresses as well as tensile stresses perpendicular to the grain in the critical areas around the beam opening can be reduced significantly. Hence, the maximum load carrying capacities of the new reinforcement concepts supposedly exceed the standardized ones considerably. For verification of the results experimental investigations on beams with different reinforcement methods are planned.
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50 records – page 2 of 5.