Failure behaviour and repair of delaminated glulam beams

- Delamination process is known to occur in glulam beams.
- Numerical studies show that delaminated glulam beams loose strength and stiffness.
- Experimental evidence on delamination effects is provided.
- Delamination repairing techniques are proposed and experimentally validated.

This paper presents the results of an experimental study carried out with the following main purposes: (i) evaluate the effect of different types of delamination of straight glulam beams on their structural behavior up to failure; (ii) evaluate the effectiveness of repairing those beams after bending failure through the use of self-drilling screws and plywood sheets; (iii) evaluate the effectiveness of a preventive repair of those beams (applied before loading them to failure) through the use of self-drilling screws.The tested elements comprised (i) reference beams, without delamination; beams with delamination at the ends involving the overall cross-section width, in (ii) moderate lengths and in (iii) significant lengths; and (iv) beams with delamination along all length at the outer thirds of the cross-section width.The results of the bending tests of the unrepaired beams showed that (i) the end delamination causes a decrease in the strength and stiffness of the beams, more markedly for longer delamination length and that (ii) the longitudinal delamination, not involving the entire cross-section width, does not significantly affect the behavior of the beams. The results of the beams repaired after failure showed that the intervention technique used is adequate and that its degree of effectiveness depends on the type of delamination and on the level of damage occurred at failure. The results of the preventively repaired beams showed that the intervention method used confers significant improvements in resistance and stiffness to unrepaired beams, although it does not allow achieving the performance of healthy beams.