Keywords: composite floor, dynamic loads, finite element modelling, vibrations, dynamic amplifications, damping coefficient.

Recent advances in material and computational technology have enabled the construction of thin and long span floors, super tall buildings, large span bridges, etc. These structures are slender and hence prone to vibration for which there is no adequate design guidance at present. Composite floors, consisting of profiled steel sheets and concrete, are popular in high-rise buildings as they are light, economical and easy to construct and find use in buildings, which house office space, light industries and parking stations. Use of high strength steel and concrete enable larger spans. However, as these composite floors are slender, they are vibration prone due to dynamic loads induced by human activity. These composite floor structures are mostly analysed and designed by static methods with provisions for dynamic amplifications [1,2]. However, these simple methods do not sufficiently address the complex response of multi-span composite floor slabs. Thus, vibration due to human activity is becoming an issue in the design of these composite floor structures, and the need for research on their dynamic responses is thus evident.

The research program described in this paper treats composite floor slabs consisting of concrete on profiled steel sheets at the base, with the steel sheet acting as permanent formwork and the steel profiles providing tensile reinforcement. It is intended to generate fundamental research knowledge on their dynamic characteristics using computer simulations supported by limited experimental testing. A composite floor system, used in vibration prone areas with large multi-panels has been chosen for the study. Experimental testing of a typical panel has been carried out. Static, free vibration and dynamic tests at a number of frequencies have been carried out. The results from these tests not only provide valuable information, but also enable the calibration of the computer models. This paper presents the initial phase of the research project, which includes the experimental testing, determination of dynamic amplification factors, natural frequency, damping coefficient and the development, calibration and validation of the finite element models.

The experimental investigation provided an increased response under dynamic loads than that under static loads. Further, it provided a damping coefficient of 3.5% and 4.0% for the panels without and with top reinforcement. The finite element models have been calibrated using the results from the static tests and validated using the results for the natural frequency.

Extensive computer simulations, using the calibrated finite element models is under way to determine the Dynamic Amplification Factors (DAFs) of multi-panel slabs under pattern loading. The analytical results will then be used to develop a deterministic procedure for design of these types of composite floor structures that are sensitive to human-induced vibrations.

1

J.G.S. da Silva, P.C.G. da S Vellasco, S.A.L. de Andrade, F.J. da CP Soeiro, R.N. Werneck, "An Evaluation of the Dynamical Performance of Composite Slabs", Computers & Structures, 81 (2003) 1905-1913. doi:10.1016/S0045-7949(03)00210-4

2

M. Willford, "An Investigation into Crowd-Induced Vertical Dynamic Loads using Available Measurements", The Structural Engineer, 79 (2001) 21-25.

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