Jetann C., Thambiratnam D., Kajewski S.

Vibration is a serviceability limit state for the design of suspended floor systems in buildings that is not well understood by many structural engineers. Dynamic behaviour is particularly critical for slender, two-way, post-tensioned concrete construction. At present, there are no reliable design guidelines that deal with this problem. To address this need, a comprehensive research program on the dynamic behaviour of post-tensioned concrete floors is presently underway at the Queensland University of Technology in Brisbane, Australia. This paper reports the preliminary results of laboratory testing and finite element analyses from this research program. A full-scale post-tensioned slab, having a span-to-depth ratio of 33.4, has been constructed in the university’s structural laboratory. Special purpose brackets have been designed to investigate the effects of support fixity at the corners of the specimen. A series of static and dynamic tests, including experimental modal analysis, have been performed in the laboratory to obtain parameters such as: stiffness, natural frequencies, mode shapes, damping and dynamic amplification factors. Parametric computational studies using finite element analysis are also being performed. Finite element models of both composite and homogeneous material cross-sections have been calibrated against results from laboratory experiments. These computational studies will be expanded to generate predictive guidelines for the free vibration and response of two-way, post-tensioned concrete floors. Field instrumentation and testing of floors in existing buildings will also be conducted to validate computational studies. Results from this research will enable the development of much needed design guidance on the dynamic behaviour of flat post-tensioned concrete floors in buildings.