Basalt Fibre Reinforcement of Bent Heterogeneous Glued Laminated Beams
Abstract
:1. Introduction
2. Materials and Methods
2.1. Specifications of Materials Used in Glulam Beams
2.2. Preparation of BFRP Reinforcement
2.3. Tests
2.4. Analytical Procedure
- the moduli of wood elasticity along the fibres in compression and in tension were distinguished,
- the modulus of elasticity of wood under tension was reduced to the modulus of elasticity of wood compressed along the fibres with the coefficient:
- the modulus of elasticity of the BFRP fibres in tension was reduced to the modulus of elasticity of the wood compressed along the fibres using the coefficient:
- —modulus of elasticity of BFRP fibres in tension,
- —the average modulus of wood elasticity when tensioned along the fibres,
- —the average modulus of wood elasticity in compression along the fibres.
- —adjustment value for reinforcement in tension zone,
- —adjustment value for bumper layer in tension zone,
- —the height of the glued beam,
- —distance of the neutral axis to the beam top before correction for reinforcement,
- —BFRP fibre diameter,
- —thickness of the “cover” of the BFRP fibre,
- —BFRP reinforcement distance to the lower edge of the beam,
- —distance of the neutral axis after reinforcement to the upper edge of the beam,
- —distance of the neutral axis to the lower edge of the beam.
2.5. Numerical Procedure
- wood quality class KS: T13 (C22),
- KG wood quality class: T8 (C14).
3. Results
3.1. Force-Bending Relation
3.2. Analysis of Normal Stresses
3.3. Modes of Failure
3.4. Comparison of Theoretical and Numerical Analysis with Laboratory Tests
4. Conclusions
- It was noted that the failure load significantly increased with an increase in the reinforcement ratio, while maximum bending was slightly reduced. Based on the test result analysis, it was concluded that the load capacity of the WR-A and WR-B was increased by, respectively, 13% and 20%, while their rigidity grew by 9.99% and 17.13%, when compared with reference beams. The tests also demonstrated that application of BFRP reduced variation in the bending strength.
- In the tests, it was found that basalt fibres perfectly compensated for the heterogeneous timber structure, being an ideal application to timber of poor and average quality. BFRP fibres inhibit or limit the propagation of cracks, neutralizing local defects in the wood. An important conclusion is that glulam beams made mostly of sawn timber of poor and average quality and reinforced with basalt fibres have better strength and rigidity parameters, and their failure modes show an increase in the elastic phase.
- It should be remembered that BFRP reinforcement in glulam beams can be applied both on-site and in the beam manufacturing process. Timber gluing is an effective method that allows for obtaining more uniform stress distribution between reinforcement and timber. The 2 mm thick epoxy layer, located directly between reinforcement and timber, maintained good quality during the entire test period. No premature delamination between the FRP composite material and timber was detected before complete timber failure.
- Theoretical analysis is important for the designer to select the appropriate type of reinforcement when designing new reinforcement techniques. For the adopted computational model of BFRP fibre composites reinforced beams in bending, the values of normal stresses of BFRP fibres were slightly higher than in laboratory or numerical tests.
- Displacements, normal stresses of wood and BFRP basalt fibres were determined with reasonable accuracy. A three-dimensional FE model was consistent with the experimental studies. The findings can be useful for further analysis of the reinforcement and repair system employing BFRP fibres. The numerical analysis can be applied to reinforced elements when designing various reinforcement schemes, with particular emphasis put on the configuration of wood quality classes. However, it is necessary to carry out material tests of the analysed elements on individual basis, and to determine the mean values for each quality class of structural timber. The determination of Poisson’s ratios for particular strength classes would allow for conducting analysis of structures with advanced computational systems at the stage of structure design.
Funding
Institutional Review Board Statement
Informed Consent Statement
Data Availability Statement
Conflicts of Interest
References
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Properties | According to PN-EN 14080:2013-07 | According to PN-EN 408 + A1:2012 |
---|---|---|
Bending strength (MPa) | 20 | 23.31 |
Tensile strength (MPa) | ||
along the fibres | 15 | - |
across the fibres | 0.5 | - |
Compressive strength (MPa) | ||
along the fibres | 18.5 | - |
across the fibres | 2.5 | - |
Modulus of elasticity (MPa) | ||
along the fibres | 10,400 | 10,300 |
Shear-modulus (MPa) | 650 | - |
Density (kg/m3) | 355 | 420.09 |
Beam Type | Description |
---|---|
NWR | non-reinforced beams made of glulam timber of average (KS) and poor (KG) quality |
WR–A | reinforced beams made of glulam timber of average (KS) and poor quality (KG), reinforced with BFRP, reinforcement ratio: 1.18% |
WR–B | reinforced beams made of glulam timber of average (KS) and poor quality (KG), reinforced with BFRP, reinforcement ratio: 1.76% |
Feature | BFRP | Epoxy Glue |
---|---|---|
Materials properties | anisotropic | - |
Density | 1.9 ÷ 2.10 g/cm3 | - |
Tensile strength | do 1.45 GPa | - |
Flexural strength | - | 0.11 ÷ 0.12 GPa |
Modulus of elasticity | do 78 GPa | 2.7 ÷ 3.3 GPa |
Linear expansion coefficient | 2.2% | - |
Material Parameters | Young’s Modulus (GPa) | Poisson’s Ratio | Shear Modulus (GPa) | ||||||
---|---|---|---|---|---|---|---|---|---|
X Axis (the Longitudinal Direction) | Y Axis (the Radial Direction) | Z Axis (the Tangential Direction) | XY Axis (for a Radial Surface) | YZ Axis (for the Face) | XZ Axis (for the Tangent Surface) | XY Axis (for a Radial Surface) | YZ Axis (for the Face) | XZ Axis (for a Radial Surface) | |
Lamella KS | 10 | 0.33 | 0.33 | 0.54 | 0.027 | 0.54 | 0.63 | 0.063 | 0.63 |
Lamella KG | 7 | 0.23 | 0.23 | 0.54 | 0.027 | 0.54 | 0.44 | 0.044 | 0.44 |
BFRP | 56.30 | 9.38 | 9.38 | 0.26 | 0.026 | 0.26 | 1.9 | 0.19 | 1.9 |
Material Parameters | Young’s Modulus (GPa) | Poisson’s Ratio |
---|---|---|
Epoxy glue | 3 | 0.30 |
BEAM | F/2 [kN] | Compressive Stresses σc [MPa] | Tensile Stresses σt [MPa] | Stresses in BFRP Fibres σBFRP [MPa] | Displacements u [mm] |
---|---|---|---|---|---|
NWR-A1 | 5 | −13.12 | 8.54 | - | 13.42 |
NWR-A2 | 5 | −10.63 | 15.97 | - | 13.92 |
NWR-A3 | 5 | −8.34 | 10.22 | - | 13.64 |
Mean | −10.70 | 11.58 | - | 13.66 | |
Standard deviation | 2.39 | 3.90 | - | 0.25 | |
WR-A1 | 5 | −12.00 | 13.07 | 58.74 | 12.89 |
WR-A2 | 5 | −6.92 | 11.60 | 44.88 | 11.91 |
WR-A3 | 5 | −11.90 | 13.38 | 55.69 | 12.09 |
Mean | −10.27 | 12.68 | 53.10 | 12.30 | |
Standard deviation | 2.90 | 0.95 | 7.28 | 0.52 | |
WR-A1 | 10 | −26.60 | 26.65 | 117.75 | 28.05 |
WR-A2 | 10 | −17.95 | 22.68 | 97.53 | 27.7 |
WR-A3 | 10 | −25.85 | 28.48 | 126.62 | 29.06 |
Mean | −23.47 | 25.94 | 113.97 | 28.27 | |
Standard deviation | 4.79 | 2.97 | 14.91 | 0.70 |
Beam | F/2 [kN] | Experimental Results | Theoretical Results | Numerical Results | ||||||
---|---|---|---|---|---|---|---|---|---|---|
σc [MPa] | σt [MPa] | σBFRP [MPa] | u [mm] | σBFRP [MPa] | σc [MPa] | σt [MPa] | σBFRP [MPa] | u [mm] | ||
NWR (Mean) | 5 | −10.70 | 11.58 | - | 13.66 | - | −9.86 | 10.57 | - | 16.30 |
WR-A (Mean) | 5 | −10.27 | 12.68 | 53.10 | 12.30 | 82.34 | −8.55 | 8.65 | 48.83 | 15.10 |
WR-A (Mean) | 10 | −23.47 | 25.94 | 113.97 | 28.27 | 164.68 | −18.49 | 17.00 | 100.04 | 30.21 |
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Wdowiak-Postulak, A. Basalt Fibre Reinforcement of Bent Heterogeneous Glued Laminated Beams. Materials 2021, 14, 51. https://doi.org/10.3390/ma14010051
Wdowiak-Postulak A. Basalt Fibre Reinforcement of Bent Heterogeneous Glued Laminated Beams. Materials. 2021; 14(1):51. https://doi.org/10.3390/ma14010051
Chicago/Turabian StyleWdowiak-Postulak, Agnieszka. 2021. "Basalt Fibre Reinforcement of Bent Heterogeneous Glued Laminated Beams" Materials 14, no. 1: 51. https://doi.org/10.3390/ma14010051