Strengthening timber with CFRP or steel plates - Short and long-term performance

The limiting factors when it comes to design of timber structures are often stiffness properties of timber products. The stiffness requirements in serviceability limit state, both short-term and longterm deformation especially in horizontal members, is a factor that often makes it necessary to increase the dimensions of the member. Both the results from experimental studies and the results of analytical modelling are presented. The experimental study comprises results from short-term tests to failure of nine glulam beams strengthened with bonded steel plates or CFRP laminates and mechano-sorptive creep tests of strengthened glulam lamellas loaded in bending at 8 MPa. Positive effects on the strengthening when it comes to short-term and long-term behaviour were shown. The arrangement of the reinforcement in the cross-section makes it possible to control the behaviour of the beams in terms of strength, stiffness and ductility. The experimental results agreed very well with the proposed models for calculating both stiffness and moment capacity of the beams