Curved and cambered glulam beams. Part 3. Constant amplitude fatigue tests

The tensile stresses acting perpendicular to grain in curved glulam beams cause failure when such beams are subjected to pure bending under long term loading conditions. To investigate the effect of tensile stresses perpendicular to grain, a three part research was undertaken at VTT. The first part was devoted to the study of curved beams under short term load, while the second part was to investigate the behaviour of beams under long term loading. The aim of the third part of the study was to investigate the behaviour of normal and repaired beams under static and cyclic loads. The report includes the results of the third part of the research carried out on curved beams with and without steel reinforcements. One repaired beam and one new beam, both having steel reinforcements were tested under static load, while one repaired beam and one new beam both with reinforcements were tested under cyclic loads. In addition, one new beam without any reinforcements was also tested under cyclic load. It was found that the repaired beams were able to carry significant portion of the static load under short term load. During cyclic loading, the initiation and propagation of fatigue cracks in both repaired beams and in new beam. The tests showed interesting results. The failure behaviour of beams with steel bars under static and cyclic load showed significant difference in failure behaviour compared to specimens without steel reinforcements.