Issue 4

The continuing trend towards lighter and longer span floor construction and large partition-free office layouts has brought the issue of floor vibration to the attention of designers and owners. In composite construction, footfall induced floor vibration is now an essential consideration in the design of floors, and has become the governing factor in some circumstances. Increasing the damping can be an effective means of reducing floor vibration. This paper describes how a constrained layer damping system may be incorporated into a composite floor, potentially improving the floor’s dynamic performance by a factor of 2 or more. The increase in damping is achievable without additional structural mass or depth and so offers considerable cost savings over alternative methods for reducing footfall vibration (such as increasing the mass and/or stiffness). The system is now available as the commercial product Resotec This paper provides some background to the floor vibration problem and discusses various vibration reduction techniques. The principles and performance of the Resotec product are then discussed in detail and three example applications are used to illustrate its potential. Michael Willford, MA(Cantab), CEng, MIMechE Arup Peter Young, MEng, CEng, MIMechE Arup William H. Algaard, MEng, PhD Arup

Timber frame buildings may have low embodied energy, but have the disadvantage of low thermal mass. Steel and concrete composite construction provides good thermal mass but is becoming less economic with the increasing cost of steel. This paper presents results from testing of a composite system that allows the use of timber with improved structural efficiency and increased thermal mass. The composite system consists of a concrete slab cast on profiled steel decking acting compositely with glue-laminated timber beams. Composite action is achieved with coach screw shear connectors between the beams and slab. The connectors have been tested in ‘push-out’ shear tests and a three-point bend test of a full-scale floor slab has been completed. The composite system is more than three times as stiff and almost twice as strong as the same beam/slab configuration without composite action. Existing analytical and design methods are compared to finite element predictions and the experimental results and show good correlation. Richard Persaud Dr Digby Symons, University of Cambridge, Department of Engineering, Trumpington Street, Cambridge, CB2 1PZ