Use of colour image analysis for assessment of fire damaged concrete

The aim of this project was to carry out a fundamental study to assess the potential of colour image analysis for use in investigations of fire damaged concrete. This involved:(a) Quantification (rather than purely visual assessment) of colour change as an indicator of the thermal history of concrete.(b) Quantification of the nature and intensity of crack development as an indication of the thermal history of concrete, supporting and in addition to, colour change observations.(c) Further understanding of changes in the physical and chemical properties of aggregate and mortar matrix after heating.(d) An indication of the relationship between cracking and non-destructive methods of testing e.g. UPV or Schmidt hammer. Results showed that colour image analysis could be used to quantify the colour changes found when concrete is heated. Development of red colour coincided with significant reduction in compressive strength. Such measurements may be used to determine the thermal history of concrete by providing information regarding the temperature distribution that existed at the height of a fire. The actual colours observed depended on the types of cement and aggregate that were used to make the concrete. With some aggregates it may be more appropriate to only analyse the mortar matrix. Petrographic techniques may also be used to determine the nature and density of cracks developing at elevated temperatures and values of crack density correlate well with measurements of residual compressive strength. Small differences in crack density were observed with different cements and aggregates, although good correlations were always found with the residual compressive strength. Taken together these two techniques can provide further useful information for the evaluation of fire damaged concrete. This is especially so since petrographic analysis can also provide information on the quality of the original concrete such as cement content and water / cement ratio. Concretes made with blended cements tended to produce small differences in physical and chemical properties compared to those made with unblended cements. There is some evidence to suggest that a coarsening of pore structure in blended cements may lead to onset of cracking at lower temperatures. The use of DTA/TGA was of little use in assessing the thermal history of concrete made with blended cements. Corner spalling and sloughing off, as observed in columns, was effectively reproduced in tests on small scale specimens and the crack distributions measured. Relationships between compressive strength/cracking and non-destructive methods of testing are discussed and an outline procedure for site investigations of fire damaged concrete is described.

The effect of a curing agent on the thermal degradation of fire retardant brominated epoxy resins

The diglycidyl ether of tetrabromobisphenol A, the diglycidyl ether of bisphenol A and their mixture was cured by 4,4'-diaminodiphenyl methane. The pyrolysis of the obtained epoxy resins was studied by TG, DSC, TG/FTIR as well as FTIR characterization of pyrolysis residues. The gaseous and high boiling pyrolysis products were collected, characterized by GC/MS and their formation is discussed. The brominated epoxy resins are thermally less stable than the non-brominated ones. This effect is caused by the amine-containing hardener. The degradation initiation reaction is associated with the formation of hydrogen bromide which further destabilizes the epoxy network. The effect of the curing agent can be used in recycling of epoxy resins to separate brominated pyrolysis products from non-brominated ones.

Parametric study of the behaviour of reinforced concrete columns in fire

The research is concerned with the application of the computer simulation technique to study the performance of reinforced concrete columns in a fire environment. The effect of three different concrete constitutive models incorporated in the computer simulation on the structural response of reinforced concrete columns exposed to fire is investigated. The material models differed mainly in respect to the formulation of the mechanical properties of concrete. The results from the simulation have clearly illustrated that a more realistic response of a reinforced concrete column exposed to fire is given by a constitutive model with transient creep or appropriate strain effect The assessment of the relative effect of the three concrete material models is considered from the analysis by adopting the approach of a parametric study, carried out using the results from a series of analyses on columns heated on three sides which produce substantial thermal gradients. Three different loading conditions were used on the column; axial loading and eccentric loading both to induce moments in the same sense and opposite sense to those induced by the thermal gradient. An axially loaded column heated on four sides was also considered. The computer modelling technique adopted separated the thermal and structural responses into two distinct computer programs. A finite element heat transfer analysis was used to determine the thermal response of the reinforced concrete columns when exposed to the ISO 834 furnace environment. The temperature distribution histories obtained were then used in conjunction with a structural response program. The effect of the occurrence of spalling on the structural behaviour of reinforced concrete column is also investigated. There is general recognition of the potential problems of spalling but no real investigation into what effect spalling has on the fire resistance of reinforced concrete members. In an attempt to address the situation, a method has been developed to model concrete columns exposed to fire which incorporates the effect of spalling. A total of 224 computer simulations were undertaken by varying the amounts of concrete lost during a specified period of exposure to fire. An array of six percentages of spalling were chosen for one range of simulation while a two stage progressive spalling regime was used for a second range. The quantification of the reduction in fire resistance of the columns against the amount of spalling, heating and loading patterns, and the time at which the concrete spalls appears to indicate that it is the amount of spalling which is the most significant variable in the reduction of fire resistance.

Behaviour of concrete frame structures under localised fire scenarios

This thesis encompasses an investigation of the behaviour of concrete frame structure under localised fire scenarios by implementing a constitutive model using finite-element computer program. The investigation phase included properties of material at elevated temperature, description of computer program, thermal and structural analyses. Transient thermal properties of material have been employed in this study to achieve reasonable results. The finite-element computer package of ANSYS is utilized in the present analyses to examine the effect of fire on the concrete frame under five various fire scenarios. In addition, a report of full-scale BRE Cardington concrete building designed to Eurocode2 and BS8110 subjected to realistic compartment fire is also presented. The transient analyses of present model included additional specific heat to the base value of dry concrete at temperature 100°C and 200°C. The combined convective-radiation heat transfer coefficient and transient thermal expansion have also been considered in the analyses. For the analyses with the transient strains included, the constitutive model based on empirical formula in a full thermal strain-stress model proposed by Li and Purkiss (2005) is employed. Comparisons between the models with and without transient strains included are also discussed. Results of present study indicate that the behaviour of complete structure is significantly different from the behaviour of individual isolated members based on current design methods. Although the current tabulated design procedures are conservative when the entire building performance is considered, it should be noted that the beneficial and detrimental effects of thermal expansion in complete structures should be taken into account. Therefore, developing new fire engineering methods from the study of complete structures rather than from individual isolated member behaviour is essential.

The spalling of concrete in fires

The occurrence of spalling is a major factor in determining the fire resistance of concrete constructions. The apparently random occurrence of spalling has limited the development and application of fire resistance modelling for concrete structures. This Thesis describes an experimental investigation into the spalling of concrete on exposure to elevated temperatures. It has been shown that spalling may be categorised into four distinct types, aggregate spalling, corner spalling, surface spalling and explosive spalling. Aggregate spalling has been found to be a form of shear failure of aggregates local to the heated surface. The susceptibility of any particular concrete to aggregate spalling can be quantified from parameters which include the coefficients of thermal expansion of both the aggregate and the surrounding mortar, the size and thermal diffusivity of the aggregate and the rate of heating. Corner spalling, which is particularly significant for the fire resistance of concrete columns, is a result of concrete losing its tensile strength at elevated temperatures. Surface spalling is the result of excessive pore pressures within heated concrete. An empirical model has been developed to allow quantification of the pore pressures and a material failure model proposed. The dominant parameters are rate of heating, pore saturation and concrete permeability. Surface spalling may be alleviated by limiting pore pressure development and a number of methods to this end have been evaluated. Explosive spalling involves the catastrophic failure of a concrete element and may be caused by either of two distinct mechanisms. In the first instance, excessive pore pressures can cause explosive spalling, although the effect is limited principally to unloaded or relatively small specimens. A second cause of explosive spalling is where the superimposition of thermally induced stresses on applied load stresses exceed the concrete's strength.

Multiple paradigms and organisational research: an analysis of work behaviour in the fire service

The thesis examines Kuhn's (1962, 1970) concept of paradigm, assesses how it is employed for mapping intellectual terrain in the social sciences, and evaluates it's use in research based on multiple theory positions. In so doing it rejects both the theses of total paradigm 'incommensurability' (Kuhn, 1962), and also of liberal 'translation' (Popper, 1970), in favour of a middle ground through the 'language-game of everyday life' (Wittgenstein, 1953). The thesis ultimately argues for the possibility of being 'trained-into' new paradigms, given the premise that 'unorganised experience cannot order perception' (Phillips, 1977). In conducting multiple paradigm research the analysis uses the Burrell and Morgan (1979) model for examining the work organisation of a large provincial fire Service. This analysis accounts for firstly, a 'functionalist' assessment of work design, demonstrating inter alia the decrease in reported motivation with length of service; secondly, an 'interpretive' portrayal of the daily accomplishment of task routines, highlighting the discretionary and negotiated nature of the day's events; thirdly, a 'radical humanist' analysis of workplace ideology, demonstrating the hegemonic role of officer training practices; and finally, a 'radical structuralist' description of the labour process, focusing on the establishment of a 'normal working day'. Although the argument is made for the possibility of conducting multiple paradigm research, the conclusion stresses the many institutional pressures serving to offset development.

Lateral instability of slender reinforced concrete columns in a fire environment

The research concerns the development and application of an analytical computer program, SAFE-ROC, that models material behaviour and structural behaviour of a slender reinforced concrete column that is part of an overall structure and is subjected to elevated temperatures as a result of exposure to fire. The analysis approach used in SAFE-RCC is non-linear. Computer calculations are used that take account of restraint and continuity, and the interaction of the column with the surrounding structure during the fire. Within a given time step an iterative approach is used to find a deformed shape for the column which results in equilibrium between the forces associated with the external loads and internal stresses and degradation. Non-linear geometric effects are taken into account by updating the geometry of the structure during deformation. The structural response program SAFE-ROC includes a total strain model which takes account of the compatibility of strain due to temperature and loading. The total strain model represents a constitutive law that governs the material behaviour for concrete and steel. The material behaviour models employed for concrete and steel take account of the dimensional changes caused by the temperature differentials and changes in the material mechanical properties with changes in temperature. Non-linear stress-strain laws are used that take account of loading to a strain greater than that corresponding to the peak stress of the concrete stress-strain relation, and model the inelastic deformation associated with unloading of the steel stress-strain relation. The cross section temperatures caused by the fire environment are obtained by a preceding non-linear thermal analysis, a computer program FIRES-T.

Exporting to Eastern Europe : principles and practice, including a case study of the market for fire fighting equipment

East-West trade has grown rapidly since the sixties, stimulating a parallel expansion in the literature on the subject. An extensive review of this literature shows how: (i) most of the issues involved have at their source the distinctions between East and West in political ideology and/or economic management, and (ii) there has been a tendency to keep theoretical and practical perspectives on the subject too separate. This thesis demonstrates the importance of understanding the fundamental principles implied in the first point, and represents an attempt to bridge the gap identified in the second. A detailed study of the market for fire fighting equipment in Eastern Europe is undertaken in collaboration with a medium-sized company, Angus Fire Armour Limited. Desk research methods are combined with visits to the market to assess the potential for the company's products, and recommendations for future strategy are made. The case demonstrates the scope and limitations of various research methods for the East European market, and a model for market research relevant to all companies is developed. Tne case study highlights three areas largely neglected in the literature: (i) the problems of internal company adaptation to East European conditions; (ii) the division of responsibility between foreign trade organisations; and (iii) bribery and corruption in East-West trade. Further research into the second topic - through a survey of 36 UK exporters - and the third - through analysis of publicised corruption cases - confirms the representativeness of the Angus experience, and reflects on the complexity of the Bast European import process, which does not always function as is commonly supposed. The very complexity of the problems confronting companies reaffirms the need to appreciate the principles underlying the subject, while the detailed analysis into questions of, originally, a marketing nature, reveals wider implications for East-West trade and East-West relations.

The effectiveness of an organisations' equal opportunities policy for the role and training of women, particularly in the fire service

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