Thesis (Ph. D.)--Lehigh University, 2006. / Includes bibliographical references and vita.

Thesis (Ph. D.)--Lehigh University, 2000. / Includes vita. Includes bibliographical references (leaves 290-295).

Strengthening of aluminium and stainless steel structural tubular sections using adhesive bonded fibre-reinforced polymer (FRP) subjected to web crippling has been investigated. Aluminium and stainless steel tubular sections may experience web crippling failure due to local concentrated loads or reactions. The web crippling strength can be enhanced by strengthening the webs of the sections in localized regions. The current international specifications of aluminium and stainless steel structures do not provide web crippling design rules for strengthening of tubular sections. Therefore, there is a need to develop safe and reliable web crippling design rules for FRP strengthened aluminium and stainless steel structures. An extensive test program was performed on FRP strengthening of aluminium and cold-formed stainless steel tubular sections subjected to web crippling. The test specimens consisted of 6061-T6 heat-treated aluminium alloy, ferritic stainless steel type EN 1.4003 and lean duplex type EN 1.4162 square and rectangular hollow sections. A total of 254 web crippling tests was conducted in this study. The tests were performed on eighteen different sizes of tubular sections which covered a wide range of web slenderness (flat portion of web depth-to-thickness) ratio from 6.2 to 62.2. The web crippling tests were conducted under the four loading conditions according to the American Specification and Australian/New Zealand Standard for cold-formed steel structures, namely End-Two-Flange, Interior-Two-Flange, End-One-Flange and Interior-One-Flange loading conditions. The investigation was mainly focused on the effects of different adhesive, FRP, surface treatment, widths of FRP plate and web slenderness of tubular sections for strengthening against web crippling. Six different adhesives, six different FRPs, two different surface treatments, three different widths of FRP plate were considered. It was found that the web crippling capacity of aluminium tubular sections are significantly increased due to FRP strengthening, especially for those sections with large value of web slenderness. The web crippling strength can be increased up to nearly 3 times using the appropriate adhesive and FRP for aluminium tubular sections, whereas the web crippling strength can be increased up to 51% and 76% for ferritic and lean duplex stainless steel tubular sections, respectively. The finite element models for FRP strengthened aluminium and stainless steel tubular structural members subjected to web crippling were developed and calibrated against the experimental results. The debonding between FRP plate and aluminium or stainless steel tubes was carefully modelled using cohesive element. It is shown that the calibrated model closely predicted the web crippling strengths and failure modes of the tested specimens. An extensive parametric study included 212 web crippling specimens was carried out using the verified finite element models to examine the behaviour of strengthened aluminium and stainless steel tubular sections subjected to web crippling. Design equations are proposed to predict the web crippling strengths of FRP strengthened aluminium and stainless steel tubular sections based on the experimental and numerical results. The web crippling strengths obtained from the tests and numerical analysis were compared with the design strengths calculated using the proposed equations. The reliability of the proposed design rules was evaluated using reliability analysis. / published_or_final_version / Civil Engineering / Doctoral / Doctor of Philosophy

This thesis proposes two forms of external confinement for concrete filled steel tubular (CFST) columns. The confinement efficiency is studied by examining the axial strength enhancement and ductility improvement of the CFST columns with external confinement. Due to the heavy demand of confining steel to restore the column ductility in seismic regions, it is more efficient to confine these columns by hollow steel tube to form CFST column. Compared with transverse reinforcing steel, steel tube provides a stronger and more uniform confining pressure to the concrete core, and reduces the steel congestion problem for better concrete placing quality. The CFST columns are therefore characterised by higher strength, ductility and large energy absorption before failure. However, a major shortcoming of CFST columns is the imperfect steelconcrete interface bonding occurred at the elastic stage as steel dilates more than concrete in compression. This adversely affects the confining effect and decreases the elastic modulus. To resolve the problem, it is proposed in this thesis to use external steel confinement in the forms of rings and ties to restrict the dilation of steel tube. For verification, a series of uni-axial compression test was performed on some CFST columns with external steel rings and ties. From the results, it was found that the external steel rings could improve both the axial strength and stiffness of the CFST columns significantly. However, the steel ties could not improve either the axial strength or elastic stiffness significantly. The confining efficiency was then investigated by comparing the strength of these confined-CFST columns with the reinforced concrete (RC) columns counterparts with the same concrete and steel volume. It is evident that the axial strength of CFST columns is much higher than the RC columns, which suggests that the application of CFST columns can utilise less construction materials and reduce the demolition waste. A theoretical model is also proposed for predicting the axial strength of ring-confined CFST columns. Comparison between the predicted results and the test results obtained by the author and other researchers shows that the proposed model gives good estimation for both unconfined and confined CFST columns. / published_or_final_version / Civil Engineering / Master / Master of Philosophy

Project report (M.S.)--Virginia Polytechnic Institute and State University, 1990. / Vita. Abstract. Includes bibliographical references (119-121). Also available via the Internet.

Thesis (Ph. D.)--University of Hong Kong, 2009. / Includes bibliographical references (leaves 269-283) Also available in print.

Thesis (Ph. D.)--Lehigh University, 1999. / Includes vita. Includes bibliographical references (leaves [184-196]).

Thesis (M. Phil.)--Hong Kong University of Science and Technology, 2004. / Includes bibliographical references (leaves 149-154). Also available in electronic version. Access restricted to campus users.

Orientador: João Alberto Venegas Requena / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Civil / Made available in DSpace on 2018-07-31T23:17:23Z (GMT). No. of bitstreams: 1 Santos_RogerioMitsuodos_M.pdf: 3363967 bytes, checksum: ca4edb9a262e5fc2478f70d7c7c011ba (MD5) Previous issue date: 2002 / Resumo: Neste trabalho são apresentadas análises de estruturas metálicas planas constituídas de barras deformáveis por flexão, por força cortante e por força axial. Nestas análises é considerado o efeito de não-linearidade física em sistemas não-conservativos. Um programa computacional foi desenvolvido, em teoria dos pequenos deslocamentos, para possibilitar a determinação do comportamento global da estrutura. A técnica empregada foi a matricial, utilizando funções de rigidez. Esta técnica possibilita análises considerando a não-linearidade física de barras, com pouco esforço computacional. Para a resolução dos sistemas não-lineares foi adotado o método incremental-iterativo de Newton-Raphson. O processo incremental de cargas foi adotado para possibilitar o acompanhamento das deformações nas barras da estrutura nos carregamentos, descarregamentos e carregamentos reversos, de acordo com a análise solicitada; sendo que para as estruturas sujeitas a carregamentos reversos foi considerado o efeito Bauschinger no sistema. No carregamento incremental da estrutura as barras seguem o comportamento elástico ou elasto-plástico dependendo do estado de tensões. No descarregamento as barras seguem somente o comportamento elástico fazendo com que apareça um resíduo plástico de deformação. Desta forma, o sistema pode ser considerado não-conservativo aproximando-se do comportamento real. O regime elasto-plástico foi considerado para barras axialmente solicitadas, predominantemente, utilizando curvas de flambagem do CRC14 (Column Research Council) e da AISC-LRFD1 (Load and Resistance Factor Design). São apresentados exemplos numéricos comparando os tipos de análises nos regimes elástico e elasto-plástico / Abstract: In this work, analyses of steel plane framed structures, consisting of deformable frames by bending, shear and axial load are presented. In these analyses the effect of material nonlinearity in nonconservative systems are considered. According to the theory of small displacements, a computational program was developed to make possible the determination of the global structure behavior. The employed technique was the matrix method, using stiffness functions. This technique makes possible analyses considering the material nonlinearity of frames with little computational effort. For the nonlinear systems resolution the Newton-Raphson incremental-iterative method was adopted. The incremental load process was adopted to make possible the accompaniment of the deformations in the frames of the structure in the loading, unloading, and reverse loading, in accordance with the requested analysis. In the structures submited to reverse loading, the acting of Bauschinger effect in the system was considered. In the incrementalloading of the structure the frames follow the elastic or elastic-plastic behavior depending on the stress state. During the unloading of the structure the frames only follow the elastic behavior. Thus, the system can be considered nonconservative coming close to the real behavior. The elastic-plastic behavior was considered mainly for frames under axial loading using the column curve of CRC14 (Column Research Council) and the column curve of AISC-LRFD1 (Load and Resistance Factor Design). Numerical examples are presented comparing the types of analyses, in elastic and elastic-plastic behavior of the frames / Mestrado / Estruturas / Mestre em Engenharia Civil

Hydraulic steel structures (HSS) are key components of U.S. Army Corps of Engineers infrastructure and are subject to corrosive environments, unpredictable loadings, and extreme conditions. Corrosion can take many forms and can cause costly damage to HSS due to inadequate design of protective measures. There are numerous forms of corrosion that have a negative effect on HSS, as well as material properties that need consideration when design HSS preventive measures. Understanding corrosion and providing proper preventive measures is crucial for HSS. Proper maintenance and repair of these protection systems also play a significant part in corrosion control of HSS.