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This thesis describes the results of research analysing the sub-contractor's risk elements in refurbishment projects. One of the main characteristics of refurbishment projects is that work is usually in small packages and scattered throughout the building making it unprofitable for one contractor to undertake. It is argued that the selection and appointment of the most suitable sub-contractors is very important in refurbishment projects as all other control measures have little effect once a totally unsuitable subcontractor has been appointed. The research methodology involved the extensive collaboration of a retired chief estimator with over thirty years experience in one of Britain's biggest construction firms with extensive knowledge in the management of sub-contractors and several other refurbishment contractors' senior management staff who were involved in choosing subcontractors for their contracts. Knowledge acquisition and representation and the evaluation of expert system shells are extensively reviewed. One of the important features of knowledge based systems is its ability to handle uncertain knowledge. Fuzzy set theory is shown to have certain advantages over other methods of dealing with uncertainty and has been employed in developing this knowledge based system. The research began with an evaluation of sub-contractors' selection and appointment as it is currently performed by refurbishment contractors. This exercise consisted of a wide range of criteria of which information is both qualitative and subjective in an unstructured intuitive manner with considerable reliance on the judgement of the evaluee. Thus, the research focused on a more formalised approach to the subcontractor's appointment. An adaptation of the Repertory Grid knowledge elicitation technique and subsequent grid analysis provides a methodology for organising logically related propositions into a hierarchical structure. A prototype knowledge based decision support system SSARC, for the selection and appointment of the most suitable sub-contractors for refurbishment projects, has been developed. This system represents a contribution in this area of research into refurbishment contracts which has been largely neglected to date.

Building with burnt clay bricks is part of Sri Lanka's engineering culture. To date, bricks produced by the island's cottage industry have remained the principal building element in the construction of walls. These walls, plastered on both sides, are used mainly as infills or partitions in reinforced concrete buildings except for walls in single storey and two storey buildings carrying light loads. . Neither bricks nor walls in Sri Lanka confirm with standard sizes and vary widely. Brickwork joints too vary also, with significant departures from the norms of other organised construction industries. These variations result in many problems in the industry in what can be described as a disordered or chaotic environment. With material costs far in excess of labour, the status-quo continues without regard to impact on time and costs. The objective of this research is to develop strategies for coping with this 'chaos' and focuses on single brick thick walls. This disorderly environment is profiled with indicators of reasons for departures. Procedures and practices adopted for coping with it are presented as case studies. Methods for computing mortar volumes are developed and validated. The impact of the brick size, joint size, the degree to which the joints are filled, wall thickness, and mortar mix is assessed with respect to mortar consumption, brickwork output, and costs. The study advocates a paradigm shift from the conventional focus of -the 'brick' and the 'joint' to the 'wall' and its 'width. A wall of a given width may be constructed not necessarily with a few discrete sizes of bricks and a standard joint size, but with a variety of brick and joint sizes. This research concludes that the generally perceived 'single best solution' of standardisation is not necessarily the only approach for coping with the existing and emerging future. There are better approaches. It recommends the 'nonstandardisation' route through chaos using its inherent flexibility to advantage in a complex environment. This route is depicted in the form of a map with features of 'universality' of costs, the 'chapparuflexibility' in the wall width, 'geometry of order' in the bed joint, and a 'general specification' for output. The end result is an 'orderly chaos'. The chaos described in Sri Lankan brickwork is different to the 'chaos' as outlined in chaos theory although exhibiting some similarities. This study shows how concepts embodied in chaos theory can be used conceptually and symbolically in furthering understanding on issues related to construction management. The benefits of this research are not limited to Sri Lanka, but are applicable both regionally and internationally. This study whilst laying the foundation for a 'theory on brickwork' suggests that rules for plastered brickwork would not necessarily be the same for exposed brickwork thereby exploring the advantages of such brickwork. It also shows the value of 'decision rules' in coping with chaotic phenomena in an emerging future. It is argued that 'chaos'presents opportunities for a new 'order'.

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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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