Strengthening of the cross-laminated timber using glass fiber-reinforced polymer on the lateral performance of the single shear lap joints

Document Type : Research Paper


1 university of mohagheghe ardabili

2 Assistant prof. of Wood Science and Technology, Department of Natural Resources, Faculty of Agriculture and Natural Resources, University of Mohaghegh Ardabili. Ardabil, Iran.

3 university of mohaghegh ardabili

4 University of Mohaghegh Ardabili

5 BSc student of of Wood Science and Technology, Department of Natural Resources, Faculty of Agriculture and Natural Resources, University of Mohaghegh Ardabili. Ardabil, Iran.


In this study, the strengthening of cross-laminated timber (CLT) with glass fiber reinforced polymer (GFRP) on the lateral resistance (LR) of the single shear lap joints was investigated. Poplar (Populus alba) layers were used to construct the three-layer CLT. In first step, the effect of GFRP strengthening of CLT panel with three layers of FRP fastened with a lag screw, concrete screw, wood screw, and steel nail at an end distance of 1 cm on the lateral load capacity was investigated. In second step, the effect of the number of GFRP layers on the LR of the joint assembled with the lag screw with an end distance of 1 cm was investigated. Finally, the main effects of panel strength directions (major and minor axes), fastener types (lag screw, concrete screw, wood screw, and steel nail), and end distances (1and 2 cm) and their interaction on LR were investigated. The results showed that LR was increased by 22 to 53% with reinforcement, which was more considerable in joints with smaller diameter fasteners. By increasing the number of GFRP layers from one to three layers, LR was increased by 27%. By increasing the end distance, changing the fastener types and panel directions, LR was changed 114.7%, 219.6%, and 7%, respectively. The interaction of variables on LR showed that by simultaneously changing the fastener types × end distance, LR changed about 447%, which implied the importance of choosing the proper fastener with sufficient end distance to construct the joints with a metal connector such as brackets.


[1] Karacabeyli, E., and Gagnon, S., 2019. Canadian CLT Handbook. 2019 Edition. Digital. Pointe-Claire, QC: FPInnovations.
[2] Ringhofer, A., Brandner, R., and Blaß, H.J., 2018. Cross laminated timber (CLT): Design approaches for dowel-type fasteners and connections. Engineering Structures, 171: 849-861.
[3] Taj, M.A., Najafi, S.K., and Ebrahimi, G., 2009. Withdrawal and lateral resistance of wood screw in beech, hornbeam and poplar. European Journal of Wood and Wood Products, 67 (2): 135-140.
[4] Eshaghi, S., Faezipour, M., and Taghiyari, H.R., 2013. Investigation on lateral resistance of joints made with drywall and sheet metal screws in bagasse particleboard and comparison with that of commercial MDF. Maderas. Ciencia y tecnología, 15 (2): 127-140.
[5] Haftkhani, A.R., Ebrahimi, G., Tajvidi, M., Layeghi, M., and Arabi, M., 2011. Lateral resistance of joints made with various screws in commercial wood plastic composites. Materials & Design, 32 (7): 4062-4068.
[6] Mohamadzadeh, M., Haftkhani, A.R., Ebrahimi, G., and Yoshihara, H., 2012. Numerical and experimental failure analysis of screwed single shear joints in wood plastic composite. Materials & Design, 35: 404-413.
[7] Jockwer, R., Caprio, D., and Jorissen, A., 2021. Evaluation of parameters influencing the load-deformation behaviour of connections with laterally loaded dowel-type fasteners. Wood Material Science & Engineering: 1-14.
[8] Kode, A., Amini, M.O., van de Lindt, J.W., and Line, P., 2021. Lateral Load Testing of a Full-Scale Cross-Laminated Timber Diaphragm. Practice Periodical on Structural Design and Construction, 26 (2): 04021001.
[9] Li, Z., Wang, X., and He, M., 2020. Experimental and analytical investigations into lateral performance of cross-laminated timber (CLT) shear walls with different construction methods. Journal of Earthquake Engineering: 1-23.
[10] Mahdavifar, V., Sinha, A., Barbosa, A.R., Muszynski, L., and Gupta, R., 2018. Lateral and withdrawal capacity of fasteners on hybrid cross-laminated timber panels. Journal of Materials in Civil Engineering, 30 (9): 04018226.
[11] Rezvani, S., Zhou, L., and Ni, C., 2021. Experimental evaluation of angle bracket connections in CLT structures under in-and out-of-plane lateral loading. Engineering Structures, 244: 112787.
[12] American Wood Council. (2015). NDS National Design Specification for Wood Construction: With Commentary. American Wood Council.
[13] Mohammad, M., Blass, H., Salenikovich, A., Ringhofer, A., Line, P., Rammer, D., 2018. Design approaches for CLT connections. Wood and Fiber Science, 50 (Special): 27-47.
[14] Oh, J.-K., Kim, G.-C., Kim, K.-M., Lee, J.-J., and Hong, J.-P., 2017. End distance of single-shear screw connection in cross laminated timber. Journal of the Korean Wood Science and Technology, 45 (6): 746-752.
[15] Brown, J.R., and Li, M., 2021. Structural performance of dowelled cross-laminated timber hold-down connections with increased row spacing and end distance. Construction and Building Materials, 271: 121595.
[16] Haftkhani, A., Ebrahimi, G., Arabi, M., Tajvidi, M., and Layeghi, M., 2012. Investigation on lateral load of joints made with various screws on commercial wood-plastic composite. Iranian Journal of Wood and Paper Science Research, 27 (1): 100-113.
[17] Coleman, G., GE, C., and HT, H., 1974. Timber structures reinforced with light gage steel.
[18] Ahad, S., Singh, J., Bhat, J.A., and Sethi, A.S., 2019. An experimental study of CLT beams reinforced with steel bars, cold formed steel plate and FRP. International Journal for Technological Research In Engineering, 6 (11): 5790- 5799.
[19] Nowak, T., Jasieńko, J., Kotwica, E., and Krzosek, S., 2016. Strength enhancement of timber beams using steel plates–review and experimental tests. Drewno: prace naukowe, doniesienia, komunikaty, 59.
[20] ASTM D1037 – Standard Test Method for Evaluating Properties of Wood-Base Fiber and Particle Panel Materials
[21] Yoon, D., Kim, S., Kim, J., and Doh, Y., 2020, Study on bearing strength and failure mode of a carbon-epoxy composite laminate for designing bolted joint structures. Composite Structures, 239: 112023.
[22] Fridley, K.J., Pollock, J.D.G., and Cobeen, K., 2006. Design of Wood Structures-ASD/LRFD. McGraw-Hill New York, NY.
[23] Williamson, T.G., 2002. APA engineered wood handbook. McGraw-Hill Professional Pub.