Steel-Concrete-Steel (SCS) composite construction consists of two relatively thin steel plates with the space between filled with concrete. Various forms of this construction exist, using overlapping shear studs and single bar connectors to provide shear reinforcement to the concrete and provide a shear transfer at the interface. The problem with current systems that rely purely upon shear studs or bar connectors is that they are prone to slip between the steel faceplates and concrete core. This slip leads to a loss of composite action causing a loss of stiffness and a reduced fatigue life. An extensive experimental programme consisting of 32 beam specimens and 34 other small scale specimens formed the basis for the study of the behaviour of surfaced SCS specimens under a variety of load conditions. The results of this test program showed that surfaced SCS specimens behaved in a more composite manner. This increase in composite action manifested itself in a number of ways. • Reduced slip between steel plate and concrete core • Increased stiffness of specimen • More even crack distribution This extensive experimental study was backed up with an analytical study to understand and predict the behaviour of the surfaced SCS elements. This study has led to a new method of predicting the capacity of such sections, to a greater degree of accuracy than current methods allow. Further to this a FE parametric study was carried out to investigate the sensitivity of the elements to changes in the main geometrical and material variables.

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The problem of unwanted noise in buildings has grown continuously over the last twenty years and impact noise through separating floors has been identified as a particularly important problem. One accepted method for improving impact sound insulation is to use floating floors in which the walking surfaces are isolated from the supporting structure by a resilient layer. Traditionally the resilient layers comprise mineral or glass fibre quilts but other materials such as flooring grade polystyrene are increasingly used. Recently, shallow profile floating floors comprising flexible open cell polyurethane foam resilient layers have been developed. These systems are attractive for refurbishment projects since they can simply be placed on existing floors in order to improve their impact sound insulation whilst raising the existing floor level less than systems comprising fibre quilts. Shallow profile floating floors with thin layers of flexible open cell polyurethane foam are the subject of investigation as part of this research work. This thesis reviews the previous research on polyurethane foams and evaluates the usefulness of the Standard Tests on these materials for assisting in the selection of foam for use as resilient layers under lightweight floors. Both the static and dynamic behaviour of flexible open cell polyurethane foam are investigated and recycled polyurethane foam is shown to be particularly useful for use under floating floors Its characteristic behaviour under compressive strain is described for the first time. This thesis shows that by modifying the Standard Method for the determinaf on of the dynamic stiffness of resilient layers under floating floors (BS EN 29052-1), the effect of the air contained in the open cell foam specimens can be included in the Standard laboratory test. The modification makes it possible to evaluate the dynamic stiffness of low airflow resistivity resilient polyurethane resilient layers using the apparatus described in BS EN 29052-1 for the first time. Field measurements of impact sound pressure level conducted using sections of lightweight shallow profile floating floor on a concrete supporting floor are described. The measured improvements in impact sound insulation achieved by using the sections of floating floor are compared with the improvements predicted using the results from the modified Standard laboratory tests on the foams used as resilient layers. It is shown that by compensating for the mass impedance of the Standard tapping machine hammers good correlation between predicted and measured data is achieved. A simple method for predicting the weighted standardised impact sound pressure level (L'nT,w) in the receiving room is proposed which shows excellent correlation with L'nT,w obtained from the measured data. The work shows that BS EN 29052-1 is more widely applicable than the Standard itself states and for the first time identifies a method of predicting the performance of lightweight shallow profile floating floors with polyurethane foam resilient layers. Finally the use of the ISO tapping machine for assessing the impact sound insulation of the very lightweight floating floors of interest to this research is considered. Different methods of correlating perceived and measured the impact sound insulation of floors are reviewed. Experimental results conducted in this research programme, along with searches of the literature confirm that the tapping machine is a suitable source for measuring the impact sound insulation of these floors.

Low frequency noise transmission between dwellings is an increasing problem due to home entertainment systems with enhanced bass responses. The problem is exacerbated since there are not presently available methods of measurement, rating and prediction appropriate for low frequency sound in rooms. A review of the classical theory of sound insulation and room acoustics has shown that both theories are not applicable. In fact, the sound insulation of party walls at low frequencies is strongly dependent on the modal characteristics of the sound fields of the two separated rooms, and of the party wall. Therefore methods originally developed for measurement conditions where the sound field was considered diffuse, may not be appropriate for room configurations with volumes smaller than 50m3 and for frequencies where sound wavelengths are large. An alternative approach is proposed using a Finite Element Method (FEM) to study the sound transmission between rooms. Its reliability depends on the definition of the model, which requires validating measurement. FEM therefore does not replace field or laboratory measurements, but provides complementary parametric surveys not easily obtainable by measurements. The method involves modelling the acoustic field of the two rooms as an Acoustic Finite Element model and the displacement field of the party wall as a Structural Finite Element model. The number of elements for each model was selected by comparing the numerical eigenfrequencies with theoretical values within an acceptable processing time and error. The simulation of a single room and of two coupled rooms, defined by linking the acoustic model with the structural model, were validated by comparing the predicted frequency response with measured response of a 1:4 scale model. The effect of three types of party wall edge condition on sound insulation was investigated: simply supported, clamped, and a combination of clamped and simply supported. It is shown that the frequency trends still can be explained in terms of the classical mechanisms. A thin masonry wall is likely to be mass controlled above 50Hz. A thick wall is stiffness controlled, below 100Hz. A clamped thin wall provides a lower sound insulation than a simply supported, whereas a clamped masonry wall provides greater sound level difference at low frequencies than a simply supported. The sound insulation of masonry walls are shown to be strongly dependent on the acoustical modal characteristics of the connected rooms and of the structural modal characteristics of the party wall. The sound pressure level difference displays a sequence of alternating maxima and minima about a trend, dictated by the properties of the party wall. The sound insulation is lower in equal room than in unequal rooms, whatever the edge conditions and smaller wall areas provide higher sound insulation than large areas. A correction factor is proposed as a function of room configuration and wall area and edge conditions. Attempts to quantify the factor were made using statistical and deterministic analyse, but further work is required.

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