Quantitative Design Guidance on Smoke Control in Shopping Malls and Atria

Prior to the commencement of the work reported in this thesis, the Fire Research Station had established design procedures for smoke ventilation in large simple-volume buildings and in single-storey shopping malls. Design procedures for multi-storey malls were largely speculative. The papers presented in this Thesis describe the development over a twenty year period of quantitatively-based design procedures for multi-storey malls; the extension of those design procedures to cover multi-storey atria of all types; and experimental and theoretical developments appropriate to both single-storey and multi-storey malls and atria, which resolved areas of uncertainty in the available design advice. The major areas of study have included the entrainment of air into "spill plumes" flowing from beneath an intermediate ceiling into, and then through, a larger void. This has required the development of empirically-based theories and their modification to allow for the effects of locating the plume beneath an extensive thermally-buoyant layer rather than in free space. It has also required the development of a novel approach to the theoretical description of the horizontal flow of gases beneath the spill edge ( ie at the edge of an opening into the larger space ). These empirically-based theories were combined with a novel analysis of the flow of thermally-buoyant gases out of a fire compartment into the mall or atrium, and with the earlier theoretical models of smoke venting from smoke layers, to form a coherent body of design advice applicable to both malls and atria. The practical limits beyond which smoke ventilation becomes inappropriate have also been deduced. Alternative methods of smoke control appropriate to malls and atria have also been developed. The most important contributions here are the techniques of ventilating each storey separately, so that a multi-storey mall or atrium can be treated as a stack of superimposed single storeys, and the method of depressurisation of an atrium smoke layer to allow the architect to use "leaky" facades as a way of increasing his or her design options. Methods are described for using the UK Fire Statistics data-base to allow the choice of design fires for retail premises, offices, and hotel bedrooms to be put on a more quantitative basis. An experiment is described which allows the selection of a "porous" suspended ceiling in a mall to be matched to the smoke control system without degrading its performance. Early theoretical and experimental studies are described which relate the sprinkler performance to the cooling and downdrag of the smoke in buoyant layers typical of smoke ventilation systems. This last work was an early entry in what has become a major field of international study. The object of the work has always been to produce design advice in a form which can be easily used by system designers and by regulatory authorities. This has been achieved for malls by the publication in 1979 of the Building Research Establishment Report known as "BRE 34", and since updated as Building Research Establishment Report BR 186 ( included herein ). This latter document has already been included as the only recommended source of design advice on smoke ventilation of shopping malls explicitly cited by British Standard BS 5588 Part 10. The areas of study described by the papers included in this thesis are not at an end. They are mostly still active areas of research, and many recently-completed ( but unpublished ) and still-current studies are mentioned in establishing the context within which the included papers must be viewed. A corollary of this is that although readily-usable design guidance on smoke control in atrium buildings, based on this and related work, has not yet been published, such a document exists in draft at the time of writing. It has not been included in this thesis, although many of the design procedures themselves are included in the published research papers.