Vibrations in Composite Timber-Concrete Floor Systems

Abstract

Timber-concrete composite structures were originally developed for bridges and strengthening existing timber floors, but is today used extensively also in new buildings. The objective of this thesis was to look at the dynamic behavior of a timber-concrete composite system, where the concrete deck consisted of several prefabricated elements glued together. The shear connector used was a glued-in steel mesh, which had shown strong capacity in previous studies. The concrete was fibre reinforced concrete.A full-scale model was built in the laboratory, and the following tests were performed: A dynamic test (hammer impact test) and a deflection test with 1 kN load. In addition a direct shear test was performed on two asymmetrical specimen to find the stiffness of the shear connector. The fibre reinforced concrete was tested separately to find its characteristic properties. There was also made a numerical model in ABAQUS, to estimate the behavior of the composite beam.The hammer impact test showed that the composite beam satisfied the dynamic requirements sat for the beam. The shear connector proved to be weaker and more ductile than expected. It was discovered this was due to insufficient gluing during the assembly. The numerical analyses done in combination with the empirical tests proved to give good estimates on the behavior of the composite beam. The stiffness of the shear connector proved to be more decisive of the deflection of the beam than the frequency. Expanding the beam to a full-size floor in ABAQUS indicated that the composite beam gave smaller values for the frequency than what would be the case for a full floor. The overall performance of the timber-concrete composite system tested in this thesis was good. However, some adjustments should be made and more research has to be done, before developing this into a new floor system.