Experimental Investigation of Cross Laminated Timber Elements with Holes or Notches at In-Plane Beam Loading Conditions
Abstract
:1. Introduction
2. Analytical Model
2.1. Background and Limitations
2.2. Failure Modes
2.3. Stress Calculation
2.3.1. Bending
2.3.2. Tension Perpendicular to Beam Axis
2.3.3. Shear Mode I
2.3.4. Shear Mode II
2.3.5. Shear Mode III
2.4. Design Verification
3. Experimental Tests
3.1. Test Setups and Materials
3.2. Test Procedure and Measurements
4. Test Results
4.1. Beam with a Hole
4.2. Beam with an End-Notch
5. Discussion
6. Conclusions and Outlook
- The experimental results on CLT beams with holes or end-notches indicate two predominant failure modes, i.e., bending failure at the holes or notches, which is mostly initiated at the finger joints; and shear failure in the crossing areas (mode III), which is indicated by significant sliding between the adjacent longitudinal laminations in the beam height direction;
- The experimental results indicate that none of the test series failed, at least as a primary failure mode, due to gross (mode I) and net shear (mode II) or due to tensile stresses perpendicular to the beam axis;
- Based on the assumed strength values proposed in the literature for shear failure in crossing areas (mode III), i.e., the rolling shear strength fR and torsional shear strength fv,tor, the reviewed analytical model is slightly conservative by underestimating the shear capacity;
- Experimental results indicate a relatively small influence on the beam strength for reduced longitudinal and transversal lamination widths near the hole or notch edges;
- Parametric studies show that, in most of the considered cases, net shear (mode II) and tensile failure perpendicular to the beam axis are the critical failure modes in design verification using the analytical model for CLT beams with holes or notches, indicating their strong underestimations;
- A consistent design approach for CLT beams with holes or notches is missing and not included in the draft of the revised version of EC 5 (CEN/TC 250/SC5) [8]. It is therefore advisable to adapt the design proposals presented in [16,17,20] also for the cases where holes or notches are introduced in CLT beams;
- Further experimental validation on CLT 5s and 7s beam elements, including also inverted layer orientation with outermost layers oriented transversally, should preferably be conducted.
Author Contributions
Funding
Institutional Review Board Statement
Informed Consent Statement
Data Availability Statement
Acknowledgments
Conflicts of Interest
References
- Jeleč, M.; Varevac, D.; Rajčić, V. Cross laminated timber (CLT): A state of the art report. Građevinar 2018, 70, 75–95. [Google Scholar]
- Brandner, R.; Flatscher, G.; Ringhofer, A.; Schickhofer, G.; Thiel, A. Cross laminated timber (CLT): Overview and development. Eur. J. Wood Wood Prod. 2016, 74, 331–351. [Google Scholar] [CrossRef]
- Brandner, R.; Dietsch, P.; Dröscher, J.; Schulte-Wrede, M.; Kreuzinger, H.; Sieder, M. Cross laminated timber (CLT) diaphragms under shear: Test configuration, properties and design. Constrution Build. Mater. 2017, 147, 312–327. [Google Scholar] [CrossRef]
- Blass, H.J.; Flaig, M. Stabförmige Bauteile aus Brettsperrholz; KIT: Karlsruhe, Germany, 2012. [Google Scholar]
- Bejtka, I. Cross (CLT) and Diagonal (DLT) Laminated Timber as Innovative Material for Beam Elements; KIT: Karlsruhe, Germany, 2011. [Google Scholar]
- Flaig, M. Biegeträger aus Brettsperrholz bei Beanspruch in Plattebene. Ph.D. Thesis, KIT, Karlsruhe, Germany, 2013. [Google Scholar]
- Danielsson, H.; Jeleč, M.; Serrano, E. Strength and Sitffness of Cross Laminated Timber at In-Plane Beam Loading; Report TVSM-7164; Division of Structural Mechanics, Lund University: Lund, Sweden, 2017. [Google Scholar]
- CEN/TC 250/SC5 (2021); Working Draft of Eurocode 5: Design of Timber Structures—Common Rules and Rules for Buildings Part 1-1: General, Version: 2021-10-27, N1489. European Committee for Standardization: Brussels, Belgium, 2021.
- Flaig, M. Design of CLT beams with rectangular holes or notches. In Proceedings of the 1st INTER-Meeting, Bath, UK, 1–4 September 2014. [Google Scholar]
- Flaig, M. In Plattenebene beanspruchte Biegeträger aus Brettsperrholz—Teil 1: Effektive Festigkeits und Steifigkeitskennwerte für die Schubbemessung. Bautechnik 2015, 92, 741–749. [Google Scholar] [CrossRef]
- Flaig, M.; Blass, H.J. Shear strength and shear stiffness of CLT-beams loaded in plane. In Proceedings of the CIB-W18, CIB-W18/46-12-3, Vancouver, BC, Canada, 26–29 August 2013. [Google Scholar]
- Jeleč, M.; Rajčić, V.; Danielsson, H.; Serrano, E. Strural analysis of in-plane loaded CLT beams with holes: FE-analysis and parameter studies. In Proceedings of the INTER/49-12-2, Graz, Austria, 16–19 August 2016. [Google Scholar]
- Jeleč, M.; Strukar, K.; Rajčić, V. Structural analysis of in-plane loaded CLT beams. Electron. J. Fac. Civ. Eng. Osijek E-GFOS 2017, 8, 20–30. [Google Scholar] [CrossRef]
- Danielsson, H.; Serrano, E.; Jeleč, M.; Rajčić, V. In-plane loaded CLT beams—Tests and analysis of element lay-up. In Proceedings of the INTER, INTER/50-12-2, Kyoto, Japan, 28–31 August 2017. [Google Scholar]
- Danielsson, H.; Serrano, E. Cross laminated timber at in-plane beam loading—Prediction of shear stresses in crossing areas. Eng. Struct. 2018, 171, 921–927. [Google Scholar] [CrossRef]
- Jeleč, M. Shear Resistiance of Cross-Laminated Timber Beam Elements. Ph.D. Thesis, Faculty of Civil Engineering, University of Zagreb, Zagreb, Croatia, 2019. [Google Scholar]
- Jeleč, M.; Danielsson, H.; Rajčić, V.; Serrano, E. Experimental and numerical investigations of cross laminated timber at in-plane beam loading conditions. Constr. Build. Mater. 2019, 206, 329–346. [Google Scholar] [CrossRef]
- Danielsson, H.; Jeleč, M.; Serrano, E.; Rajčić, V. Cross laminated timber at in-plane beam loading—Comparison of model predictions and FE-analyses. Eng. Struct. 2019, 179, 246–254. [Google Scholar] [CrossRef]
- Jeleč, M.; Danielsson, H.; Serrano, E.; Rajčić, V. Cross laminated timber at in-plane beam loading—New analytical model predictions and relation to EC5. In Proceedings of the INTER, INTER/51-12-5, Tallinn, Estonia, 13–16 August 2018. [Google Scholar]
- Jeleč, M.; Dokšanović, T.; Draganić, H.; Rajčić, V. Advancement in prediction of shear strength and stiffness of cross laminated timber beams. Eng. Struct. 2021, 238, 112247. [Google Scholar] [CrossRef]
- DIN EN 1995-1-1/NA; National Annex—Nationally Determined Parameters—Eurocode 5: Design of Timber Structures—Part 1-1: General—Common Rules and Rules for Buildings. Deutsches Institut für Normung: Berlin, Germany, 2013.
- EN 338:2016; Structural Timber—Strength Classes. European Committee for Standardization (CEN): Brussels, Belgium, 2016.
- Brandner, R.; Bogensperger, T.; Schickhofer, G. In shear strength of cross laminated timber (CLT): Test configuration, quantification and influencing parameters. In Proceedings of the CIB-W18/46-12-2, Vancouver, BC, Canada, 26–29 August 2013. [Google Scholar]
- Brandner, R.; Dietsch, P.; Droscher, J.; Schulte-Wrede, M.; Kreuzinger, H.; Sieder, M.; Schickhofer, G.; Winter, S. Shear properties of cross laminated timber (CLT) under in-plane: Test configuration and experimenal study. In Proceedings of the INTER/49-12-2, Sibenik, Croatia, 24–27 August 2015. [Google Scholar]
- Brandner, R.; Dietsch, P.; Droscher, J.; Schulte-Wrede, M.; Sieder, M. Scheibenschub von Brettsperrholz: Verifizierung einer Prüfkonfiguration und Parameterstudie. Bautechnik 2015, 92, 759–769. [Google Scholar] [CrossRef]
- Ehrhart, T.; Brandner, R. Rolling shear: Test configurations and properties of some European soft- and hardwood species. Eng. Struct. 2018, 172, 554–572. [Google Scholar] [CrossRef]
- Europan Technical Assessment ETA-12/0281 from 19.08.2017; Noritec Holzindustrie GmbH—Cross Laminated Timber (CLT)—Solid Wood Slab Elements to Be Used as Structural Elements in Buildings. Austrian Institute for Construction Engineering: Vienna, Austria, 2017.
- JCSS Probabilistic Model Code Part III—Resistance Models, Section 3.05—Timber; Joint Committe on Structural Safety (JCSS): Zurich, Switzerland, 2006; ISBN 978-3-909386-79-6.
- Andreolli, M.; Tomasi, R.; Polastri, A. Experimental investigation on in-plane behaviour of cross-laminated timber elements. In Proceedings of the CIB-W18/45-12-4, Växjö, Sweden, 27–30 August 2012. [Google Scholar]
- Jöbstl, R.A.; Bogensperger, T.; Schickhofer, G. In plane shear strength of cross laminated timber. In Proceedings of the CIB-W18/41-12-3, St. Andrews, NB, Canada, 24–28 August 2008. [Google Scholar]
Varying Parameter | Beam with a Hole | Beam with an End-Notch |
---|---|---|
Lamination width (bx = by = b) | 150 mm | 150 mm |
Beam height (h) | ≥600 mm; ≤1800 mm | ≥300 mm; ≤1200 mm |
Layup ratio (tnet,y/tgross) | 0.20 | 0.20 |
Layup ratio (tgross/nCA) | 50 mm | 50 mm |
Hole length (lh) | ≥b; ≤h | - |
Hole height (hh) | ≥b; ≤0.5h | - |
Aspect ratio of the hole (lh/hh) | ≥1; ≤4 | - |
Notch depth (h − hef) | - | ≥b; ≤0.5h |
Notch length (ln) | - | ≥b; ≤0.5h |
Aspect ratio of the notch (ln/hef) | - | ≤1.0 |
Test Series | Number of Specimens | tgross [mm] | h [mm] | L [mm] | hh (hef) [mm] | lh (ln) [mm] | M/V [-] | Layup [mm] |
---|---|---|---|---|---|---|---|---|
H1 | 4 | 100 | 600 | 3300 | 300 | 300 | 1.50h | 40-20-40 |
H2 | 4 | 100 | 600 | 3300 | 240 | 240 | 1.50h | 40-20-40 |
H3 | 4 | 100 | 600 | 3300 | 300 | 300 | ∞ | 40-20-40 |
H4 | 4 | 100 | 600 | 3000 | 300 | 300 | 0 | 40-20-40 |
N1 | 4 | 100 | 600 | 2400 | 300 | 200 | 0.33h | 40-20-40 |
N2 | 4 | 100 | 600 | 2400 | 450 | 200 | 0.33h | 40-20-40 |
Test Series | Test Specimen | by * [mm] | bx,1 [mm] | bx,2 [mm] | bx,3 [mm] | bx,4 [mm] | bx,5 [mm] | bx,6 [mm] | h = Σbx [mm] |
---|---|---|---|---|---|---|---|---|---|
H1 | 1 | 121 | 83 | 67 | 131 | 168 | 30 | 120 | 599 |
2 | 121 | 69 | 80 | 118 | 182 | 16 | 136 | 601 | |
3 | 121 | 53 | 96 | 102 | 198 | - | 151 | 600 | |
4 | 113 | 164 | - | 198 | 88 | 110 | 40 | 600 | |
H2 | 1 | 146 | 38 | 142 | 56 | 184 | 14 | 166 | 600 |
2 | 148 | 52 | 128 | 70 | 170 | 28 | 152 | 600 | |
3 | 151 | 122 | 58 | 140 | 100 | 98 | 82 | 600 | |
4 | 149 | 138 | 43 | 155 | 85 | 113 | 68 | 602 | |
H3 | 1 | 31 | 82 | 68 | 130 | 170 | 28 | 122 | 600 |
2 | 25 | 165 | - | 198 | 89 | 109 | 40 | 601 | |
3 | 27 | 150 | - | 198 | 102 | 96 | 53 | 599 | |
4 | 31 | 136 | 16 | 182 | 118 | 80 | 72 | 604 | |
H4 | 1 | 104 | 118 | 33 | 165 | 135 | 63 | 88 | 602 |
2 | 96 | 57 | 94 | 104 | 135 | 2 | 148 | 601 | |
3 | 96 | 132 | 18 | 180 | 119 | 79 | 70 | 598 | |
4 | 106 | 132 | 49 | 149 | 151 | 47 | 104 | 602 | |
N1 | 1 | 28 | 148 | 152 | 46 | 198 | 60 | - | 604 |
2 | 31 | 130 | 168 | 30 | 198 | 70 | - | 596 | |
3 | 15 | 66 | 198 | 34 | 164 | 134 | - | 596 | |
4 | 15 | 55 | 198 | 47 | 151 | 150 | - | 601 | |
N2 | 1 | 28 | 98 | 198 | 154 | 44 | 105 | - | 599 |
2 | 33 | 118 | 198 | 134 | 64 | 85 | - | 599 | |
3 | 16 | 80 | 198 | 172 | 26 | 128 | - | 604 | |
4 | 35 | 102 | 198 | 150 | 48 | 100 | - | 598 |
Test Series | H1 | H2 | H3 | H4 | ||||
---|---|---|---|---|---|---|---|---|
Test Specimens | Fmax [kN] | δ6,Fmax [mm] | Fmax [kN] | δ6,Fmax [mm] | Fmax [kN] | δ6,Fmax [mm] | Fmax [kN] | δ6,Fmax [mm] |
1 | 125.4 | 17.94 | 179.7 | 22.29 | 201.3 | 16.30 | 240.5 | 9.48 |
2 | 149.8 | 25.99 | 170.9 | 17.48 | 183.9 | 20.51 | 255.7 | 8.34 |
3 | 152.0 | 19.82 | 166.7 | 25.36 | 198.7 | 17.26 | 203.3 | 8.58 |
4 | 163.7 | 22.12 | 175.1 | 23.70 | 188.3 | 18.98 | 225.3 | 7.98 |
Mean | 147.7 | - | 173.1 | - | 193.1 | - | 231.2 | - |
CoV | 9.4% | - | 2.8% | - | 3.7% | - | 8.4% | - |
Test Series | N1 | N2 | ||
---|---|---|---|---|
Test Specimens | Fmax [kN] | δ6,Fmax [mm] | Fmax [kN] | δ6,Fmax [mm] |
1 | 213.7 | 17.23 | 247.8 | 21.56 |
2 | 189.8 | 16.77 | 230.4 | 17.61 |
3 | 194.3 | 17.55 | 225.4 | 12.23 |
4 | 200.4 | 16.54 | 231.3 | 12.99 |
Mean | 199.6 | - | 233.7 | - |
CoV | 4.5% | - | 3.6% | - |
Failure Modes | Bending | Tension | FM I | FM II | FM III | ||||
---|---|---|---|---|---|---|---|---|---|
Test Specimen | Fmax [kN] | σx (1) [MPa] | σx,h (2) [MPa] | σt,y,h (7) [MPa] | τxy,gross,h (9) [MPa] | τxy,net,h (11) [MPa] | τzx,h (21) [MPa] | τzy,h (19) [MPa] | τtor,z,h (16) [MPa] |
H1-1 | 125.4 | 21.55 | 29.10 | 16.70 | 3.14 | 13.18 | 0.66 | 0.56 | 2.00 |
H1-2 | 149.8 | 25.75 | 34.78 | 19.96 | 3.75 | 15.75 | 0.79 | 0.66 | 2.39 |
H1-3 | 152.0 | 26.13 | 35.28 | 20.26 | 3.80 | 15.98 | 0.80 | 0.67 | 2.43 |
H1-4 | 163.7 | 28.14 | 37.99 | 21.82 | 4.09 | 17.21 | 0.86 | 0.73 | 2.61 |
mean | 147.7 | 25.34 | 34.28 | 19.68 | 3.69 | 15.53 | 0.77 | 0.66 | 2.36 |
H2-1 | 179.7 | 30.89 | 32.88 | 19.72 | 3.74 | 17.23 | 0.86 | 0.55 | 2.28 |
H2-2 | 170.9 | 29.38 | 31.28 | 18.76 | 3.56 | 16.38 | 0.82 | 0.52 | 2.17 |
H2-3 | 166.7 | 28.65 | 30.50 | 18.30 | 3.47 | 15.98 | 0.80 | 0.51 | 2.11 |
H2-4 | 175.1 | 30.09 | 32.04 | 19.22 | 3.65 | 16.78 | 0.84 | 0.53 | 2.22 |
mean | 173.1 | 29.75 | 31.67 | 19.00 | 3.61 | 16.59 | 0.83 | 0.53 | 2.19 |
H3-1 | 201.3 | 25.17 | 25.17 | 3.75 | 2.52 * | 12.58 * | 0.63 * | - | 1.57 * |
H3-2 | 183.9 | 22.99 | 22.99 | 3.43 | 2.30 * | 11.49 * | 0.57 * | - | 1.44 * |
H3-3 | 198.7 | 24.84 | 24.84 | 3.71 | 2.48 * | 12.42 * | 0.62 * | - | 1.55 * |
H3-4 | 188.3 | 23.54 | 23.54 | 3.51 | 2.35 * | 11.77 * | 0.59 * | - | 1.47 * |
mean | 193.1 | 24.13 | 24.13 | 3.60 | 2.41 | 12.07 | 0.60 | - | 1.51 |
H4-1 | 240.5 | 12.53 | 20.04 | 18.80 | 4.01 | 16.86 | 0.84 | 0.63 | 2.56 |
H4-2 | 255.7 | 13.32 | 21.31 | 19.98 | 4.26 | 17.92 | 0.90 | 0.67 | 2.72 |
H4-3 | 203.3 | 10.59 | 16.94 | 15.89 | 3.39 | 14.25 | 0.71 | 0.53 | 2.17 |
H4-4 | 225.3 | 11.73 | 18.78 | 17.61 | 3.76 | 15.79 | 0.79 | 0.58 | 2.40 |
mean | 231.2 | 12.04 | 19.27 | 18.07 | 3.85 | 16.20 | 0.81 | 0.60 | 2.46 |
Failure Modes | Bending | Tension | FM I | FM II | FM III | FM III | ||||
---|---|---|---|---|---|---|---|---|---|---|
Test Specimen | Fmax [kN] | σx (1) [MPa] | σx,n (4) [MPa] | σt,y,n (8) [MPa] | τxy,gross,n (10) [MPa] | τxy,net,n (12) [MPa] | τzx (21) [MPa] | τtor,z (17) [MPa] | τzy,n (20) [MPa] | τtor,z,n (17) [MPa] |
N1-1 | 213.7 | 23.37 | 17.81 | 46.31 | 5.34 | 24.58 | 0.67 * | 1.67 * | 0.77 | 3.07 |
N1-2 | 189.8 | 20.76 | 15.82 | 41.14 | 4.75 | 21.83 | 0.59 * | 1.48 * | 0.68 | 2.73 |
N1-3 | 194.3 | 21.26 | 16.19 | 42.10 | 4.86 | 22.35 | 0.61 * | 1.52 * | 0.70 | 2.79 |
N1-4 | 200.4 | 21.92 | 16.70 | 43.43 | 5.01 | 23.05 | 0.63 * | 1.57 * | 0.72 | 2.88 |
mean | 199.6 | 21.83 | 16.63 | 43.25 | 4.99 | 22.96 | 0.62 * | 1.56 * | 0.72 | 2.87 |
N2-1 | 247.8 | 27.10 | 9.17 | 16.77 | 4.13 | 18.48 | 0.77 * | 1.94 * | 0.56 | 2.31 |
N2-2 | 230.4 | 25.20 | 8.53 | 15.60 | 3.84 | 17.18 | 0.72 * | 1.80 * | 0.52 | 2.15 |
N2-3 | 225.4 | 24.65 | 8.34 | 15.26 | 3.76 | 16.81 | 0.70 * | 1.76 * | 0.51 | 2.10 |
N2-4 | 231.3 | 25.29 | 8.56 | 15.66 | 3.86 | 17.25 | 0.72 * | 1.81 * | 0.52 | 2.16 |
mean | 233.7 | 25.56 | 8.65 | 15.82 | 3.90 | 17.42 | 0.73 * | 1.83 * | 0.53 | 2.18 |
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. |
© 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).
Share and Cite
Jeleč, M.; Damjanović, D.; Varevac, D.; Rajčić, V. Experimental Investigation of Cross Laminated Timber Elements with Holes or Notches at In-Plane Beam Loading Conditions. Buildings 2022, 12, 967. https://doi.org/10.3390/buildings12070967
Jeleč M, Damjanović D, Varevac D, Rajčić V. Experimental Investigation of Cross Laminated Timber Elements with Holes or Notches at In-Plane Beam Loading Conditions. Buildings. 2022; 12(7):967. https://doi.org/10.3390/buildings12070967
Chicago/Turabian StyleJeleč, Mario, Domagoj Damjanović, Damir Varevac, and Vlatka Rajčić. 2022. "Experimental Investigation of Cross Laminated Timber Elements with Holes or Notches at In-Plane Beam Loading Conditions" Buildings 12, no. 7: 967. https://doi.org/10.3390/buildings12070967