A flexible adhesive layer to strengthen glulam beams

Brunner, Maurice Yaw; Lehmann, Martin; Kraft, Sebastian; Fankhauser, Urs; Richter, Klaus; Conzett, Jürg (2010). A flexible adhesive layer to strengthen glulam beams Journal of Adhesion Science and Technology, 24(8-10), pp. 1665-1701. Taylor & Francis 10.1163/016942410X507759

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Glulam is manufactured by gluing graded timber boards on top of each other with standard, stiff adhesives to form a beam. The research presented here is concerned with the use of a single flexible adhesive layer at a certain position of the beam cross section instead of the standard, stiff adhesive. In a first step, fundamental theoretical considerations for a favourable redistribution of the stresses over the cross section of the beam are presented and the position of the flexible adhesive layer is optimized in order to obtain the highest bending resistance of the total beam. Further calculations help to determine the requisite mechanical properties of the adhesive layer. They are communicated to the adhesive manufacturer as target values for the development of new adhesives. The industrial partner was able to produce several adhesive layers with the required mechanical properties. There was a need to select a limited number of the adhesive layers for further tests. The selection was done based on creep and delamination tests. Finally, several beams were manufactured with three selected adhesive layers. Bending tests were carried out to verify the theoretical predictions. The beams manufactured with two of the selected adhesives did not perform well on the large scale as compared to the small scale tests. One of the adhesive layers, however, gave completely satisfactory results: The beams manufactured with this adhesive layer exhibited much higher strength than the control beams and thus confirmed the theoretical expectations. The authors envision a new strengthening technique for glulam beams with this simple technique of using a single, flexible adhesive layer in the beam cross section.

Item Type:

Journal Article (Original Article)


School of Architecture, Wood and Civil Engineering
School of Architecture, Wood and Civil Engineering > Institute for Materials and Wood Technology
BFH Centres and strategic thematic fields > BFH Centre for Wood - Resource and Material
School of Architecture, Wood and Civil Engineering > Institut for Building Materials and Biobased Products IBBM


Brunner, Maurice Yaw;
Lehmann, Martin0000-0002-0813-7023;
Kraft, Sebastian;
Fankhauser, Urs;
Richter, Klaus and
Conzett, Jürg


Q Science > Q Science (General)
T Technology > T Technology (General)
T Technology > TA Engineering (General). Civil engineering (General)
T Technology > TH Building construction
T Technology > TP Chemical technology




Taylor & Francis




Sally Haddad

Date Deposited:

04 May 2020 11:31

Last Modified:

01 Oct 2021 02:18

Publisher DOI:


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Uncontrolled Keywords:

Flexible adhesive layer Stress redistribution Bending resistance





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