Glued Composite Timber-Concrete Beams.II: Analysis and Tests of Beam Specimens

This paper reports an experimental program on composite timber-concrete beams with glued interface. The test results are compared to those provided by an analytical model based on the assumption of a fully composite behavior. Both cast-on-site and prefabricated composite timber-concrete beams were produced, aimed at simulating rehabilitation situations or the possibility of a partial or of a full prefabrication of the composite element. Timber-concrete beams with dowel-type shear connectors were also produced and tested for comparison. The results show that the strength is similar, but the glued beams displayed a larger stiffness and, consequently, smaller deflections, which may be of relevance in design. The results also show that, at least under stabilized and dry room conditions, the prevailing mode of failure is tension in timber and, when shear failure occurs, it is mostly conditioned by the shear strength of the concrete or the timber, not by that of the adhesive. As the system depends on the shear strength of the interface, a preceding program consisting in tests on small-size composite specimens was undertaken and is reported in a companion paper.