The current research work investigates the behaviour of steel and composite beams as well as beam-to-column connections at elevated temperatures. Significant attention is needed to identify the main issues, as the behaviour is profoundly different from that at ambient temperature. Local buckling of the beam flange outstands has been found to be highly significant in accelerating the development of catenary action in fire, since this action is reliant on hinges forming which may result from local buckling. Local buckling of the beam web, which experiences a non-uniform temperature variation, is also important because the mechanical properties of the steel are degraded non-uniformly from their ambient values. Current formulations for web buckling at ambient temperature therefore need substantial revision at elevated temperatures. Very large compressive forces are developed within the beams initially and these induce large stresses in the column web; hitherto this has not been considered. Developing a formulation representing the mechanics of this potential failure zone in the column web in the compression region of the connection is a useful and needed addition to research in the topic. Predicting the critical temperature in a connection that causes failure of the bolts, end plate and column flange in the tension zone of the connection is considered in this research work. An elastic analysis of a panel zone in a rigid or semi-rigid joint in a steel frame, which is based on simple equilibrium considerations that takes into account the shear and flexural deformations of the panel zone, is developed at elevated temperatures. In order to model the structural response of a composite beam restrained by cooler members in a steel compartment fire in a frame structure at elevated temperature, recourse is needed to a geometric nonlinear formulation, since the beam transverse deflections are not negligible and the axial compressive force in the member is also substantial at the early stages of the fire. This thesis presents such a formulation, which incorporates partial interaction between the concrete slab and steel component, as well as the degradation of the stiffnesses of the components of the composite beam prior to yield at elevated temperature.

Master of Science / Department of Grain Science and Industry / Bhadriraju Subramanyam / Heat treatment of grain-processing facilities involves using elevated temperatures of 50- 60˚C for 24 h or less to manage stored-product insects. Heat is an alternative to a non-ozone depleting fumigant sulfuryl fluoride, which was registered in the United States in 2004 for disinfestation of grain-processing facilities. In this study, life history traits of the warehouse beetle, Trogoderma variabile Ballion, were characterized on ground cat food at 28°C and 65% RH to facilitate harvesting life stages of a specific age for bioassays with heat. Eggs laid by females were observed for daily eclosion. Eggs hatched on days 6 through 10, and the mean proportion for egg hatching was 87%. Larvae hatching from eggs (first instars) were reared on ground cat food and their head capsule widths were measured every 2 d until all larvae became pupae. Head capsule widths indicated six instars and the total larval duration ranged from 28-40 d. Pupae became adults in 3-9 d. Newly eclosed unmated female adults lived 7 d longer than unmated males (16 d), whereas mated males lived 2 d longer than mated females (8 d). Eggs were not observed when food was not provided to male and female pairs. Females started laying eggs 2 d after pairing until the fifth day. The total number of eggs laid by mating pairs in the presence of food ranged from 30 to 135. Exposure of eggs, young larvae, old larvae, pupae, and adults of T. variabile at 46, 50, and 54°C and 15-20% RH for four fixed time periods showed pupae to be generally more heat tolerant than other life stages. At 46, 50, and 54°C, complete mortality of all stages occurred at 1440, 120, and 30 min, respectively. Pupae also were generally more heat tolerant than other life stages during tests in pilot flour and feed mills at Kansas State University and in a commercial grain-processing facility. However, results from pilot and commercial mills were not as conclusive as the results at fixed temperatures in the laboratory.

Roxithromycin is a semi-synthetic, macrolide antibiotic, derived from erythromycin A. It acts as a bacteriostatic drug at low concentrations and a bactericidal drug at high concentrations. It binds to the 50S subunit of the 70S ribosome, which causes the reversible inhibition of RNA-dependent bacterial protein synthesis. It is well known that active pharmaceutical ingredients (APIs) may exist in numerous solid states. Differences in the solid state significantly influence the physical and chemical properties of an API. The in vivo performance of a dosage form will also be influenced by the solid state properties of a given pharmaceutical active. The amorphous characteristics of APIs have a significant impact on their performance and thus offer the potential for exciting new pharmaceuticals. Whilst amorphous forms of poorly soluble APIs are more soluble than their crystalline counterparts, they tend to be physically unstable, which makes their formulation into solid dosage forms quite challenging. Roxithromycin has only 50% oral bioavailability due to its poor aqueous solubility and for this reason, its potential for optimal therapeutic effect are limited. Poor solubility is thus an important obstacle in formulation development. During this study, amorphous forms of roxithromycin were prepared via quench cooling, and desolvation of chloroform- and ethyl acetate solvates. These amorphous forms were characterised by means of several techniques, whilst their solubilities and stabilities were also investigated. The outcomes of the solubility studies illustrated the complexity of this API and its amorphous forms with regards to their interactions with water. Solubility studies confirmed the superior solubility of the roxithromycin glass (prepared through quench cooling) and amorphous forms (desolvation of solvates) over the roxithromycin monohydrate in water. The solubility in water improved in the order of roxithromycin monohydrate < roxithromycin glass < roxithromycin glass powder < amorphous chloroform desolvate. The roxithromycin monohydrate, as well as the amorphous forms of roxithromycin demonstrated stability over a one-month period of exposure 40°C and relative humidity (RH) of 75%. The roxithromycin glass powder tended to revert to the more stable crystalline monohydrate after week 3 of stability testing. The roxithromycin glass at lower temperatures of 25°C and 30°C (both at 75% RH) tended to transform into the more crystalline form at week 4 of the study. These transformations were, however, not as significant as during the 40°C / 75% RH study. The conclusion could therefore be made that this transformation into the crystalline form was more temperature – than moisture dependant. At a higher temperature (at identical humidity conditions), the transformation into the crystalline form was much faster. Stability studies on the two roxithromycin desolvates were also performed in order to determine whether these amorphous forms, would differ, with regards to their stability, from the glass prepared through heating and cooling. It was determined that the desolvates were more stable than the roxithromycin glass. / Thesis (MSc (Pharmaceutics))--North-West University, Potchefstroom Campus, 2012

Roxithromycin is a semi-synthetic, macrolide antibiotic, derived from erythromycin A. It acts as a bacteriostatic drug at low concentrations and a bactericidal drug at high concentrations. It binds to the 50S subunit of the 70S ribosome, which causes the reversible inhibition of RNA-dependent bacterial protein synthesis. It is well known that active pharmaceutical ingredients (APIs) may exist in numerous solid states. Differences in the solid state significantly influence the physical and chemical properties of an API. The in vivo performance of a dosage form will also be influenced by the solid state properties of a given pharmaceutical active. The amorphous characteristics of APIs have a significant impact on their performance and thus offer the potential for exciting new pharmaceuticals. Whilst amorphous forms of poorly soluble APIs are more soluble than their crystalline counterparts, they tend to be physically unstable, which makes their formulation into solid dosage forms quite challenging. Roxithromycin has only 50% oral bioavailability due to its poor aqueous solubility and for this reason, its potential for optimal therapeutic effect are limited. Poor solubility is thus an important obstacle in formulation development. During this study, amorphous forms of roxithromycin were prepared via quench cooling, and desolvation of chloroform- and ethyl acetate solvates. These amorphous forms were characterised by means of several techniques, whilst their solubilities and stabilities were also investigated. The outcomes of the solubility studies illustrated the complexity of this API and its amorphous forms with regards to their interactions with water. Solubility studies confirmed the superior solubility of the roxithromycin glass (prepared through quench cooling) and amorphous forms (desolvation of solvates) over the roxithromycin monohydrate in water. The solubility in water improved in the order of roxithromycin monohydrate < roxithromycin glass < roxithromycin glass powder < amorphous chloroform desolvate. The roxithromycin monohydrate, as well as the amorphous forms of roxithromycin demonstrated stability over a one-month period of exposure 40°C and relative humidity (RH) of 75%. The roxithromycin glass powder tended to revert to the more stable crystalline monohydrate after week 3 of stability testing. The roxithromycin glass at lower temperatures of 25°C and 30°C (both at 75% RH) tended to transform into the more crystalline form at week 4 of the study. These transformations were, however, not as significant as during the 40°C / 75% RH study. The conclusion could therefore be made that this transformation into the crystalline form was more temperature – than moisture dependant. At a higher temperature (at identical humidity conditions), the transformation into the crystalline form was much faster. Stability studies on the two roxithromycin desolvates were also performed in order to determine whether these amorphous forms, would differ, with regards to their stability, from the glass prepared through heating and cooling. It was determined that the desolvates were more stable than the roxithromycin glass. / Thesis (MSc (Pharmaceutics))--North-West University, Potchefstroom Campus, 2012

This thesis investigates, using finite element modelling and experimental investigation, the fracture of mesh reinforcement in composite floor slabs at elevated temperatures. The main objective of the research is the study of the bond strength between the welded mesh reinforcement and concrete at elevated temperatures, since this was found to be the principal behaviour that governs the fracture of the reinforcement in a composite floor slab.The experimental programme included steady state and transient pull-out tests carried out at temperatures varying from 20°C to 1000°C. However, unlike previous work, which concentrated on the bond of single bars, rectangular normal concrete prisms were constructed with one longitudinal bar, ensuring a bond length of 200 mm, and one transverse bar welded centrally. As a result, the influence of the weld of the mesh reinforcement in the bond strength between reinforcement and concrete was studied. The bond strength-slip-temperature relationship was obtained for various sized ribbed and plain bars. It was found that the 6, 7 and 8mm diameter ribbed mesh failed by fracture of the longitudinal bar at all temperatures, including ambient temperature. It was shown that the reduction of bond strength of ribbed mesh was similar to the reduction in strength of the bar, which together with the observed modes of failure, lead to the conclusion that ribbed mesh can be assumed to be fully bonded at all temperatures. The 10mm diameter ribbed mesh failed by splitting due to the cover-bar diameter ratio being small. In contrast, all the plain bars failed by fracture of the weld followed by pull-out of the bar. Therefore the correct bond stress-slip relationship should be modelled for smooth bars to accurately predict global structural behaviour.The investigation using finite element modelling utilizes the DIANA program. The incorporation by the author of the bond strength-slip-temperature relationship within the models permits a better prediction of fracture of the reinforcement in composite floor slabs. It has been shown that smooth bars are more beneficial since the bond is broken before fracture of the bar allowing strains to be distributed along the bar. In the case of ribbed bars the bond is such that localised strain will occur in the bar at crack locations leading quickly to fracture of the reinforcement.

The variation in the compressive strength of concrete block masonry was studied at elevated temperatures. Small specimens known as wallettes were used to obtain the compressive strength under steady state conditions. Eighteen wallettes were made of lightweight concrete blocks and 1:1:5 mortar proportion. The target temperatures were 20°C, 200°C, 400°C, 600°C, 700°C and 800°C. Initially load-deflection relationships were determined from the experimental wallettes and later they were converted into stress-strain relationships. Although the goal was to determine the compressive strength, other parameters were also studied such as modulus of elasticity, temperature-time relationships, modes of failure, material degradation, and change of colour.Lightweight concrete blocks were also tested to determine the compressive strength at equal temperatures applied for the wallettes. The blocks belonged to the same batch used for the wallettes. The tensile behaviour of mortar was determined at 20°C, 200°C and 400°C.Once the mechanical properties of the masonry wallettes, units and mortar were determined, they were used as input data to develop finite element models to simulate the same behaviour of the experimental wallettes. Finally, using the experimental and numerical results from the wallettes, they were used to predict the behaviour of 3m height walls.

Submitted by Patrícia Valim Labres de Freitas (patricial) on 2016-04-05T18:36:31Z No. of bitstreams: 1 Mauricio Schafer_.pdf: 3502667 bytes, checksum: bef575d3f673b57858290149f4ca04ed (MD5) / Made available in DSpace on 2016-04-05T18:36:31Z (GMT). No. of bitstreams: 1 Mauricio Schafer_.pdf: 3502667 bytes, checksum: bef575d3f673b57858290149f4ca04ed (MD5) Previous issue date: 2015-10-28 / itt Performance - Instituto Tecnológico em Desempenho da Construção Civil / UNISINOS - Universidade do Vale do Rio dos Sinos / Uma solicitação extrema a que uma alvenaria pode ser submetida é a decorrente de incêndios, que se destacam pelo grande potencial de degradação. Os revestimentos de argamassa são normalmente aplicados sobre substratos e, por comporem a última camada da alvenaria, se tornam mais suscetíveis às elevadas temperaturas. O estudo das alterações macro e microestruturais das argamassas podem auxiliar na identificação dos níveis de temperatura a que a estrutura foi submetida ao longo de um incêndio, permitindo um melhor diagnóstico sobre o sinistro e uma melhor estimativa sobre o nível de danos da estrutura de concreto e demais componentes da edificação. Partindo deste contexto, esta pesquisa tem como objetivo a análise da influência de elevadas temperaturas em um revestimento de argamassa. O programa experimental desenvolvido possui duas etapas: a primeira utilizando-se argamassas de revestimento aplicadas sobre blocos cerâmicos submetidos, em uma mufla, a temperaturas de 100, 300, 500, 700, e 900ºC, e caracterizados com relação a sua macroestrutura (resistência de aderência, absorção de água e velocidade de propagação da onda) e microestrutura (microscopia eletrônica de varredura e porosimetria por intrusão de mercúrio). A segunda etapa consiste no ensaio de paredes de alvenaria, construídas com o mesmo bloco cerâmico e a mesma argamassa da etapa anterior, em um forno que simula a ação de incêndio, especificado pela NBR 10636 (ABNT, 1989). Nas temperaturas até 300ºC houve uma melhoria nas propriedades das argamassas, já a partir da temperatura de 500ºC ocorreu uma degradação das argamassas e do revestimento, com queda de revestimento a partir da temperatura de 700ºC. Embora os procedimentos utilizados para o aumento da temperatura em mufla e em forno tenham ciclos de aquecimento distintos, não foram constatadas diferenças expressivas entre os resultados de ensaios em revestimentos submetidos a aquecimento em mufla e os submetidos ao forno simulando o incêndio. / An extreme request that masonry can be submitted is the result of fires that stand out for great potential of degradation. The mortar coatings are typically applied to substrates, and compose the last layer of masonry, become more susceptible to elevated temperatures. The study of changes macro and microstructure of the mortars can help identify temperature levels to which the structure was subjected over a fire, enabling a better diagnosis of the accident and a better estimate of the level of damage of the concrete structure and other components of the building. From this context, this research aims to analyze the influence of high temperatures in a mortar coating. The experimental program has two steps: first using a mortar coating applied over subjected ceramic blocks in a muffle furnace at temperatures of 100, 300, 500, 700, and 900°C, and characterized with regard to its macrostructure (adhesion resistance, water absorption and speed wave propagation) and microstructure (scanning electron microscopy and mercury intrusion porosimetry). The second step consists in testing masonry walls built with the same ceramic block and the same mortar in an oven to simulate the action of fire, specified by NBR 10636 (ABNT, 1989). In temperatures to 300°C there was an improvement in the properties of mortars, already from 500°C temperature occurred the deterioration of the mortar and coating, coated drop from the temperature of 700°C. Although the procedures used for increasing the temperature in a muffle furnace and oven have separate heating cycles, no significant differences observed between the test results on coatings.

Concrete is a strong material as to its compressive strength. However, it is a material with a low tensile and shear strength, and brittleness at failure. Concrete has to be reinforced with appropriate materials. Steel fibre is one of the most common materials currently being used to develop reinforced concrete, which may replace partially or completely conventional steel reinforcement. Successful reinforcement of concrete composite is closely related to the bond characteristics between the reinforcing fibre and matrix. The effective utilisation of steel fibre reinforced concrete (SFRC) requires in-depth and detailed understanding of bonding mechanisms governing the tensile behaviour. In response to this demand, this study embraced two main areas: understanding the reinforcing mechanisms of fibres in SFRC and material's post-cracking behaviour. Comprehensive experimental and theoretical programmes have therefore been developed: the experimental work is subdivided into three parts. The first part was to investigate the effect of various physical parameters, such as fibre characteristics (i.e. geometry, inclination angle, embedded length, diameter and tensile strength) and matrix strength which controls the pull-out behaviour of steel fibres. The second part is concerned with the assessment of the bond mechanisms of straight and hooked end fibres after exposure to elevated temperatures and varying matrix strength. The third part is devoted to gain further insight on the bond mechanisms governing the post-cracking behaviour through uniaxial and bending tests. It was found that the varying hook geometry and matrix strength each had a major influence on the pull-out response of hooked end fibres. As the number of the hook's bends increased, the mechanical anchorage provided by fibre resulted in significant improvement of mechanical properties of SFRC. The reduction in bond strength at elevated temperatures is found to be strongly related to the degradation in properties of the constituent materials, i.e. the fibre and concrete. The most effective combination of matrix strength and fibre geometry was found to be as follows: 3DH (single bend) fibre with normal-medium strength matrix, 4DH (double bend) fibre with high strength matrix and 5DH (triple bend) fibre with ultra-high performance matrix. Two analytical models to predict the pull-out behaviour of hooked end fibres were developed. Both models were able to predict the pull-out response of SFRC made from a variety of fibre and matrix characteristics at ambient temperature. This work has established a comprehensive database to illustrate the bonding mechanisms of SFRC and anchorage strengthening of various hooked end fibres, and this should contribute towards an increasing interest and growing number of structural applications of SFRC in construction.

A fundamental task in structural stability analysis is to ensure the safety of structures throughout their operational life so as to prevent catastrophic consequences either at ambient or elevated temperatures. This thesis concerns the stability of unbraced steel frames due to abnormal loadings or fire loads, and develops practical methods to evaluate the stability capacity of unbraced steel frames at ambient temperature or in fire. The problem of determining the elastic buckling strengths of unbraced steel frames subjected to variable loadings can be expressed as an optimization problem with stability constraints based on the concept of storey-based buckling. The optimization problem can be solved by the linear programming method, which is considerably simpler and more suitable for engineering practice than the nonlinear programming method. However, it was found that the frame buckling strength obtained from the linear programming method based on Taylor series approximation on column stiffness may be overestimated in some cases. Thus, a secant approximation of the column stiffness was introduced, and a modified linear programming method based on the secant approximation was proposed. Numerical examples show that the linear programming method in light of the secant approximation can yield conservative results and maintain simplicity. In spite of the convenience of the modified linear programming method, numerical examples show that the linear programming method cannot accurately detect the maximum and minimum frame buckling strengths in some cases. Therefore, an alternative method to assess the lateral stiffness of an axially loaded column derived by using two cubic Hermite elements to signify the column is proposed. Unlike the column stiffness obtained from the Euler-Bernoulli beam theory containing transcendental functions, the stiffness in the proposed method includes only polynomials. Thus, the column stiffness within the proposed method enables the minimization and maximization problems to be solved by efficient gradient-based nonlinear programming algorithms, which overcome the inability of linear programming algorithm to detect the minimum frame buckling strength in some cases. The accuracy of the column stiffness associated with the proposed method was compared with that of the Euler-Bernoulli beam theory. Four unbraced steel frames were investigated to demonstrate the efficiency of the proposed method. It is known that the evaluation of the lateral stability of steel frames subjected to elevated temperatures is different from that at ambient temperature due to the degradation of material strength. Thus, the storey-based buckling method at ambient temperature was extended to evaluating the stability of unbraced steel frames subjected to elevated temperature. To simulate a steel column exposed to the elevated temperature, an analytical model was proposed to examine the effects of axial loading, elevated temperature, and thermal boundary restraints on the lateral stiffness of steel columns in unbraced frames. The procedure of evaluating the stability capacity of unbraced steel frames at elevated temperature was then concluded. Numerical examples are presented to demonstrate the evaluation procedure of the proposed method. The column model was then refined to evaluate the lateral stiffness of steel column subjected to non-uniform elevated temperature distributions along the longitudinal direction. The lateral stiffness equation of the column model was derived based on the Euler-Bernoulli beam theory. The procedure to evaluate the stability capacity of unbraced steel frames subjected to non-uniform elevated temperature distributions was then concluded. The numerical examples were investigated with the proposed method for non-uniform elevated temperature distributions. Finally, initial attempts were made to evaluate the stability of unbraced steel frames with fire-protected columns at different fire scenarios. A degradation factor charactering the variation of the Young's Modulus of steel at elevated temperature was introduced. The objective and constraint functions were constructed, and optimal tools were used to determine the buckling strength of an unbraced steel frame at different fire scenarios.

No description available.