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No description available.

Thesis (M. Sc.)--University of Hong Kong, 2005.

No description available.

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<p> The thesis summarizes the experimental and analytical results of studies on the behavior of two FRP-encased steel-concrete composite columns under axial loading. Composite columns have been conventionally constructed using steel and concrete. This study utilizes FRP in combination with steel and concrete to manufacture composite columns with enhanced behavior. The first type of column is a concrete-encased steel column wrapped with epoxy-saturated glass and carbon fiber reinforced polymer (GFRP and CFRP) sheets in the transverse direction. The second type of composite column utilizes a GFRP tube that surrounds a steel I section column, which is subsequently filled with concrete. </p> <p> To the best of the author's knowledge, columns comprising FRP, steel and concrete in the shape of the proposed composite systems has not been reported on in the literature. This study includes two major phases. In the first phase, behavior of stub columns is investigated where stability effects are ignored and failure is governed by the loss of cross-sectional strength. In the second phase, influence of stability on the behavior of the proposed composite columns is studied by testing specimens with various slenderness ratios. </p> <p> To investigate the cross-sectional strength, a total of nine short (500 mm in height) composite column specimens were constructed and tested under axial compression. Five specimens were wrapped with FRP sheets and the remaining four were constructed using a GFRP tube. Experimental results showed significant enhancement in the behavior of the composite columns which was achieved due to confinement and composite action between the constituent materials. The compressive strength of the confined concrete core in the composite specimens constructed using FRP sheets and GFRP tube increased by a factor of 2.4 and 1.8, respectively. An analytical model was developed to predict crosssectional behavior of the proposed composited column. </p> <p> With the primary objective of investigating the influence of slenderness on the behavior of the composite columns, ten additional column specimens, ranging between 1,000 mm and 3,000 mm in height, were tested. Five specimens were constructed using FRP sheets and five constructed using the GFRP tube technique. It was found that the compressive strength of the confined concrete core in the longest tubular composite specimen was reduced to approximately 60% of that of the corresponding short specimen. No confinement was achieved in the longest FRP wrapped composite column specimen. </p> <p> Three bare steel columns, ranging between 500 mm and 3,000 mm in height, were also tested to facilitate comparison with the composite columns in terms of increased axial capacity, as well as stiffness and energy dissipation characteristics of the columns. The compressive strength, elastic axial stiffness and ultimate axial strain of the bare steel columns increased by a factor of up to 10, 6 and 3, respectively, in the composite columns constructed utilizing the concrete-filled GFRP tube. These factors were reduced to 5 .2, 2.5 and 2.6, respectively, in the concrete-encased steel columns wrapped with FRP jackets. </p> <p> Finally, an analytical model was developed to establish the capacity curves for the proposed composite columns accounting for slenderness effects. A simple design equation to predict the compressive strength of the tubular composite columns was proposed based on the capacity curve generated from the analytical model. Compressive capacity of the composite columns predicted using the proposed design equation showed favorable agreement with the experimental results. </p> / Thesis / Doctor of Philosophy (PhD)

Yes / Steel-concrete composite structures are commonly used in buildings and bridges because it takes advantage of tensile strength of steel and compressive strength of concrete. The two components are often secured by shear connectors such as headed studs to prevent slippage and to maintain composite action. In spite of its popularity, very little research was conducted on steel-concrete composites particularly on headed stud shear connectors in regards to its post-fire behaviour. This research investigates the post-fire behaviour of innovative shear connectors for composite steel and concrete. Three type of connectors were investigated. They are headed stud shear connectors, Blind Bolt 1 and Blind Bolt 2 blind bolts. Push-out test experimental studies were conducted to look at the behaviour and failure modes for each connector. Eighteen push tests were conducted according to Eurocode 4. The push test specimens were tested under ambient temperatures and post fire condition of 200˚C, 400˚C and 600˚C. The results in ambient temperature are used to derive the residual strength of shear connectors after exposing to fire. Findings from this research will provide fundamental background in designing steel-concrete composites where there is danger of fire exposure.

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No / Precast concrete hollow core floor units (hcu) are widely used in all types of multistorey steel framed buildings where they bear onto the top flanges of universal beams. The steel beam is normally designed in bending, in isolation from the concrete slab, and no account is taken of the composite beam action available with the precast units. A program of combined experimental and numerical studies was undertaken that aimed at deciding on a suitable approach for the design of composite steel beams that utilize precast concrete hollow core slabs. The results show that the precast slabs may be used compositely with the steel beams in order to increase both flexural strength and stiffness at virtually no extra cost, except for the headed shear studs. For typical geometry and serial sizes, the composite beams were found to be twice as strong and three times as stiff as the equivalent isolated steel beam. The failure mode was ductile, and may have been controlled by the correct use of small quantities of tie steel and insitu infill concrete placed between the precast units.

Este trabalho objetivou o estudo dos edifícios de múltiplos andares constituídos por elementos mistos aço-concreto, com enfoque acadêmico, porém abordando aspectos e recomendações normativas diretamente aplicadas na prática corrente da engenharia estrutural. A revisão bibliográfica foi realizada com base em estudos acadêmicos e normativos além do estudo de um edifício exemplo constituído por elementos mistos. Os elementos mistos lajes, vigas e pilares foram abordados inicialmente de forma isolada, com base nas recomendações normativas, sendo que ao final os elementos foram interligados, apresentando ao leitor os principais aspectos teóricos e normativos para o dimensionamento de um edifício completo constituído de elementos estruturais mistos. / This study aims the multiple storey buildings formed by composite elements steel-concrete, with academic emphasis, however approaching standard recommendations and aspects directly applied to the structural engineering. A bibliographic review based on academic and standard studies was made, besides the design of an example building formed by composite elements. The composite elements: slabs, beams and columns were firstly approached based on standard aspects, and in the end, the elements were interconnected and presented to the reader the main theoretical and standard aspects to the design of a complete building formed by composite structural elements.