When compared to traditional concrete, steel fibre reinforced concrete (SFRC) shows several enhancements in performance, including improved tensile resistance, toughness and ductility. One potential application for SFRC is in columns where the provision of steel fibres can improve performance under axial and lateral loads. The use of SFRC can also allow for partial replacement of transverse reinforcement required by modern seismic codes. To improve workability, self-consolidating concrete (SCC) can be combined with steel fibres, leading to highly workable SFRC suitable for structural applications. Recent advances in material science have also led to the development of ultra-high performance fibre reinforced concretes (UHPFRC), a material which exhibits very high compressive strength, enhanced post-cracking resistance and high damage tolerance. In heavily loaded ground-story columns, the use of UHPFRC can allow for reduced column sections. This thesis presents the results from a comprehensive research program conducted to study the axial behaviour of columns constructed with highly workable SFRC and UHPFRC. As part of the experimental program, twenty-three full-scale columns were tested under pure axial compressive loading. In the case of the SFRC columns, columns having rectangular section and constructed with SCC and steel fibres were tested, with variables including fibre content and spacing of transverse reinforcement. The results confirm that use of fibres results in improved column behaviour due to enhancements in core confinement and cover behaviour. Furthermore, the results demonstrate that the provision of steel fibres in columns can allow for partial replacement of transverse reinforcement required by modern codes. The analytical investigation indicates that confinement models proposed by other researchers for traditional RC and SFRC can predict the response of columns constructed with SCC and highly workable SFRC. In the case of the UHPFRC columns, variables included configuration and spacing of transverse reinforcement. The results demonstrate that the use of appropriate detailing in UHPFRC columns can result in suitable ductility. Furthermore, the results demonstrate the improved damage tolerance of UHPFRC when compared to traditional high-strength concrete. The analytical investigation demonstrates the need for development of confinement models specific for UHPFRC.

Most of existing North American bridge infrastructure is reported to be deficient. Present infrastructure management mainly relies on qualitative evaluation, where bridge safety and serviceability are judged through routine visual inspection. With the successive increase in the number of severely deficient bridges and the limited available resources, it is crucial to develop a performance-based quantitative assessment evaluation approach that enables an accurate estimation of aging bridges ultimate and seismic capacities and ensures their serviceability. Reinforcement corrosion is the main cause of most of North American concrete infrastructure deterioration. Experimental investigations prove that reinforcement corrosion results in reduction of the steel reinforcement cross sectional area, localized (or global in very extreme cases) loss of bond action, concrete spalling, loss of core concrete confinement, and structural collapse. Field observations show that damage due to reinforcement corrosion in reinforced concrete (RC) bridge columns is localized in highly affected zones by splash of deicing water. In this thesis, an innovative performance-based semi-quantitative assessment framework is developed using newly developed simplified nonlinear static and dynamic finite element analysis approaches. The framework integrates the bridge’s available design and after-construction information with enhanced inspection and additional material testing as sources for accurate input data. In order to evaluate the structural performance and the capacity of the corrosion-damaged bridge columns, four nonlinear static and dynamic analysis approaches have been developed: (i) simplified nonlinear sectional analysis (NLSA) approach that presents the basis of the analysis approaches to estimate the ultimate and seismic capacities, and serviceability of bridge columns; (ii) simplified nonlinear finite element analysis (NLFEA) approach, which enables estimating the ultimate structural capacity of corrosion-damaged RC columns; (iii) simplified hybrid linear/nonlinear dynamic finite element analysis (SHDFEA) approach to evaluate the serviceability of the bridge; and, (iv) simplified non-linear seismic analysis (SNLSA) approach to evaluate the seismic capacity of the bridge columns. The four analysis approaches are verified by comprehensive comparisons with available test experimental and analytical results. The proposed semi-quantitative assessment framework suggests three thresholds for each performance measure of the evaluation limit states to be decided by the bridge management system team. Case studies are presented to show the integrity and the consistency of using the proposed assessment framework. The proposed assessment framework together with the analysis approaches provide bridge owners, practicing engineers, and management teams with simplified and accurate evaluation tools, which lead to reduce the maintenance/rehabilitation cost and provide better safety, and reduce the variation in the data collected using only traditional inspection methods.

Appropriate transverse confinement can significantly improve strength, ductility and energy dissipation capacity of reinforced concrete columns, therefore enhancing their seismic resistance. This study is conducted to evaluate the seismic behaviour of concrete columns transversely confined by steel spirals, ties or fiber reinforced polymer (FRP) wrapping. In the experimental program of this study, fifteen circular concrete columns of 356 mm (14 in.) diameter and 1473 mm (58 in.) length were tested under lateral cyclic displacement excursions while simultaneously subjected to constant axial load thus simulating earthquake loads. Eight columns were solely confined by various amounts of steel spirals, while seven other columns containing only minimal steel spirals were retrofitted by external FRP wrapping. Test results revealed that the increased transverse confinement can improve the energy dissipation capacity, ductility, deformability and flexural strength of concrete columns. The required transverse confinement should also be enhanced with the increase of axial load level to satisfy certain seismic design criterion. A computation program was developed to conduct monotonic pushover analysis for confined concrete columns, which can predict the envelope curves of moment vs. curvature and shear vs. deflection hysteresis loops with reasonable accuracy for columns subjected to simulated seismic loading. Based on extensive numerical analysis, expressions were developed for the relationships between the amount of transverse confinement and different ductility parameters, as well as the strength enhancement of confined columns. Finally, design procedures to determine the amount of transverse confinement were developed for concrete columns to achieve a certain ductility target. The enhancement of flexural strength of columns due to transverse confinement was also evaluated.

Appropriate transverse confinement can significantly improve strength, ductility and energy dissipation capacity of reinforced concrete columns, therefore enhancing their seismic resistance. This study is conducted to evaluate the seismic behaviour of concrete columns transversely confined by steel spirals, ties or fiber reinforced polymer (FRP) wrapping. In the experimental program of this study, fifteen circular concrete columns of 356 mm (14 in.) diameter and 1473 mm (58 in.) length were tested under lateral cyclic displacement excursions while simultaneously subjected to constant axial load thus simulating earthquake loads. Eight columns were solely confined by various amounts of steel spirals, while seven other columns containing only minimal steel spirals were retrofitted by external FRP wrapping. Test results revealed that the increased transverse confinement can improve the energy dissipation capacity, ductility, deformability and flexural strength of concrete columns. The required transverse confinement should also be enhanced with the increase of axial load level to satisfy certain seismic design criterion. A computation program was developed to conduct monotonic pushover analysis for confined concrete columns, which can predict the envelope curves of moment vs. curvature and shear vs. deflection hysteresis loops with reasonable accuracy for columns subjected to simulated seismic loading. Based on extensive numerical analysis, expressions were developed for the relationships between the amount of transverse confinement and different ductility parameters, as well as the strength enhancement of confined columns. Finally, design procedures to determine the amount of transverse confinement were developed for concrete columns to achieve a certain ductility target. The enhancement of flexural strength of columns due to transverse confinement was also evaluated.

The thesis is dealing with mixing processes havingapplication to ground improvement by deep mixing. The mainobjectives of the thesis is to make a contribution to knowledgeof the basic mechanisms in mixing binding agents into soil andimprove the knowledge concerning factors that influence theuniformity of stabilised soil. A great part of the work consists of a literature surveywith particular emphasis on literature on the processindustries. This review forms a basis for a profounddescription and discussion of the mixing process and factorsaffecting the process in connection with deep mixingmethods. The thesis presents a method for a simple field test for thestudy of influential factors in the mixing process. A number offactors in the installation process of lime-cement columns havebeen studied in two field tests using statistical multifactorexperiment design. The effects of retrieval rate, number ofmixing blades, rotation speed, air pressure in the storagetank, and diameter of the binder outlet on the stabilisationeffect and the coefficient of variation determined byhand-operated penetrometer tests for excavated lime-cementcolumns, were studied. The literature review, the description of the mixingprocess, and the results from the field tests provide a morebalanced picture of the mixing process and are expected to beuseful in connection to ground improvement projects and thedevelopment of mixing equipments. The concept of sufficient mixture quality, i.e. theinteraction between the mixing process and the mechanicalsystem, is discussed in the last section. By means ofgeostatistical methods, the analysis considers thevolume-variability relationship with reference to strengthproperties. According to the analysis, the design values forstrength properties depends on the mechanical system, the scaleof scrutiny, the spatial correlation structure, and the conceptof safety, i.e. the concept of sufficient mixture quality isproblem specific. Key words:Deep Mixing, Lime cement columns, Mixingmechanisms, Mixture quality, Field test, ANOVA, Variancereduction.

Thesis (Ph.D.)--McMaster University, 2003. / Advisor: K. Dunbabin. Also available via World Wide Web.

Thesis (Ph. D.)--University of New South Wales, 2005. / Also available online.

Thesis (Ph. D.)--University of Texas at Austin, 2008. / Vita. Includes bibliographical references.

Mémoire (M.A.)-- Université du Québec à Chicoutimi, 1994. / Document électronique également accessible en format PDF. CaQCU

Thesis (M.S.)--University of North Texas, Dec., 2008. / Title from title page display. Includes bibliographical references.