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Reinforced concrete buildings may be vulnerable to progressive collapse due to a lack of continuous reinforcement. Progressive collapse is an extreme form of collapse that is disproportionate to the originating cause. Such collapses cause not only significant damage to buildings, but also greater loss of life and injuries. Carbon fiber reinforced polymer (CFRP) may be used to retrofit existing reinforced concrete beams and provide the missing continuity needed to resist progressive collapse. This research focuses on retrofitting the beams in a reinforced concrete building to provide sufficient continuity to reach catenary action. The catenary action may allow the beam to carry vertical loads at large displacements if a supporting column were removed. The CFRP can provide continuity through the negative moment reinforcement or through the positive moment reinforcement. The research was broken into three major components. Anchorage tests form the design basis of the CFRP retrofit and ensure that the capacity of the retrofit can be accurately predicted. Continuity tests determine if the CFRP retrofit is capable of providing continuity and if the retrofit will allow the beam to reach catenary action and sustain a load representing resistance to progressive collapse. The analysis model forms a set of equations for catenary action so the results can be applied to reinforced concrete beams in general. Forty anchorage tests, eight continuity tests, and one analysis model were constructed and evaluated. The anchorage tests found that carbon fiber anchors enabled improved utilization of the tensile capacity of a CFRP sheet and improved the efficiency of material usage in CFRP retrofits. The continuity tests found that beams without continuous reinforcement can reach catenary action (depending on design details) and a CFRP retrofit, if designed correctly (placed in locations that do not cause rebar fracture before catenary), may be able to reduce vulnerability to progressive collapse. The analysis model was able to accurately predict the load-deflection behavior of a reinforced concrete beam in catenary action. The overall conclusion is that a CFRP retrofit can reduce vulnerability to progressive collapse in reinforced concrete buildings. / text

Slender structures are elegant aesthetically. The insufficiency in knowledge of the real resistance to buckling of very slender reinforced concrete columns leads to an exaggeration of the sizes of the columns. _The examples of concrete compression members cited and constructed in Industry on a global basis suggest that very slender columns have inherent safety both from the point of view of the ultimate strength and stability. The strengths of columns given. by the British codes would seem to be exceeded by many of the long slender reinforced concrete columns and struts which have been used Internationally. Both the theoretical and the experimental short term investigations have been carried out to establish the behaviour of hinged, very slender reinforced concrete columns at various stages'of axial loading. Forty three very slender reinforced concrete columns of two different square cross sections with two sizes of longitudinal reinforcements with lateral ties were cast. Slenderness rates, L A, were varied from 30 to 79. Special factors were obtained to relate the actual modulus of elasticity of concrete in columns at buckling failure to a knowledge of the initial modulus of elasticity of concrete in control cylinder specimens. Both theoretical and experimental graphs of load against moment, made dimensionless for critical sections of columns have been obtained. Dimensionless load-moment interaction diagrams using material failure as the criterion have been superimposed on these graphs to show considerable inherent material strength of the tested columns near buckling collapse failures. A theory using the fundamental approach has, been developed to predict the deflected shape and moments along the, heights of the columns at various stages of loading. The proposed theory predicts with good correlations the experimental deflections and moments of any loading stages of the columns. The theory has been used to obtain the required variables, to arrive at the initial predicted design loads of the investigated columns. Good correlations of the moments derived from observed strains have also been obtained. The developed theory predicts satisfactorily the buckling collapse loads of the columns. Although the theory has been derived for axially I loaded very slender reinforced concrete-columns, it seems to accept satisfactorily eccentricities of up to about 10 mm. This was confirmed after extensive comparisons of the theoretical buckling collapse loads with the applicable tests of other authors. Creep In the columns investigated was discovered to be one of the major factors for serious consideration. This was conclusively revealed from the observations on the last two very long term creep tests on columns. The actual safe sustained loads for these very slender columns of slenderness ratios, L/H, between 40 and 79 seem to be between 33% and 19% of the short term buckling collapse loads. The reduced modulus approach to predict the safe long term sustained loads seems to give reasonable values for L/H ratios of 40 and 50. The recommendations given for the proposed design of very slender reinforced concrete columns seem to be adequate and simple to use in practice. They are further simplified by the derivation of two equations for the reduction factors, R, for the slenderness ratios between 36 and 40 and between 40 and 79 respectively. The investigation has proved that very slender reinforced concrete columns are very dangerous structural members, as they tend to have violent buckling failures. Nevertheless, It must be prudent not to design against disaster at any cost. This Investigation seemed to have enhanced considerably knowledge of the design of very slender reinforced concrete columns.

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Rehabilitation and maintenance of the aging transportation infrastructure are of major concern in the Province of Ontario. A large portion of this work is related to the durability of highway bridges around the province. One of the weakest points in a bridge structure from a durability aspect is the expansion joints that can allow harmful elements, such as road salts and contaminants to leak down from the road surface and attack the supporting structure of the bridge. Although expansion joints can be eliminated in the design of a new bridge, such as in an integral abutment bridge, this requires major changes to the supports and structure of the bridge, making it impractical for retrofitting existing bridges. One effective alternative is the replacement of a traditional expansion joint with a link slab. A link slab is a concrete slab used in place of an expansion joint to make the bridge deck continuous while keeping the supporting girders simply supported [1]. Link slabs must be able to resist large force effects both in bending and direct tension while minimizing cracking [2], one solution is to use the high tensile and flexural strength properties of an ultra-high performance fibre-reinforced concrete (UHPFRC) [3]. The UHPFRC mixtures are often proprietary and expensive. The purpose of this research was to evaluate the potential of using common fibre types with standard concrete ingredients in a fibre-reinforced concrete (FRC) as an alternative to UHPFRC in a link slab. Using a selection of macro fibres commonly used in slab on grade applications for crack control, an optimized FRC mixture was developed following the principals established by Rossi and Harrouche [4]. This mixture was then used with a variety of fibre types to evaluate the structural and durability properties of the FRC. Testing was conducted for fresh mixture properties, compressive, tensile and flexural strength as well as freezing and thawing resistance, linear shrinkage, environmental and salt exposure along with other durability tests. Results showed that the concrete mixture used for an FRC link slab should consist of; an equal ratio of fine and coarse aggregate by weight and a higher than normal percentage of cement paste, for optimal workability and a dosage of 1.5% by volume of macro steel fibres. Hooked-end steel fibres resulted in the best performance increase to the FRC of the six fibre types tested. Results also showed that reinforcing cage for an FRC link slab should be designed to ensure that fibres can evenly reach all areas of the link slab form to give homogeneous fibre distribution. Although the FRCs created did not perform to the high level of a UHPFRC, these results show a consistent and effective FRC can be created, for use in a link slab with common fibres and standard concrete materials to provide a less expensive and more widely available FRC link slab than UHPFRC.

A procedure for improved nonlinear analysis of reinforced concrete (RC) slab and shell structures is presented. The finite element program developed employs a layered thick-shell formulation which considers out-of-plane (through-thickness) shear forces, a feature which makes it notably different from most shell analysis programs. Previous versions were of limited use due to their inabilities to accurately capture out-of-plane shear failures, and because analyses were restricted to force-controlled monotonic loading conditions. The research comprising this thesis focuses on addressing these limitations, and implementing new analysis features extending the range of structures and loading conditions that can be considered. Contributions toward the redevelopment of the program include: i) a new solution algorithm for out-of-plane shear, ii) modelling of cracked RC in accordance with the Disturbed Stress Field Model, iii) the addition of fibre-reinforced concrete (FRC) modelling capabilities, and iv) the addition of cyclic and dynamic analysis capabilities. The accuracy of the program was verified using test specimens presented in the literature spanning various member types and loading conditions. The new program features are shown to enhance modelling capabilities and provide accurate assessments of shear-critical structures. An experimental program consisting of RC and FRC slab specimens under dynamic loading conditions was performed. Eight intermediate-scale slabs were constructed and tested to failure under sequential high-mass low-velocity impact. The data from the testing program were used to verify the dynamic and FRC modelling procedures developed, and to contribute to a research area which is currently limited in the database of literature: the global response of RC and FRC elements under impact. Test results showed that the FRC was effective in increasing capacity, reducing crack widths and spacings, and mitigating local damage under impact. Analyses of the slabs showed that high accuracy estimates can be obtained for RC and FRC elements under impact using basic modelling techniques and simple finite element meshes.

A procedure for improved nonlinear analysis of reinforced concrete (RC) slab and shell structures is presented. The finite element program developed employs a layered thick-shell formulation which considers out-of-plane (through-thickness) shear forces, a feature which makes it notably different from most shell analysis programs. Previous versions were of limited use due to their inabilities to accurately capture out-of-plane shear failures, and because analyses were restricted to force-controlled monotonic loading conditions. The research comprising this thesis focuses on addressing these limitations, and implementing new analysis features extending the range of structures and loading conditions that can be considered. Contributions toward the redevelopment of the program include: i) a new solution algorithm for out-of-plane shear, ii) modelling of cracked RC in accordance with the Disturbed Stress Field Model, iii) the addition of fibre-reinforced concrete (FRC) modelling capabilities, and iv) the addition of cyclic and dynamic analysis capabilities. The accuracy of the program was verified using test specimens presented in the literature spanning various member types and loading conditions. The new program features are shown to enhance modelling capabilities and provide accurate assessments of shear-critical structures. An experimental program consisting of RC and FRC slab specimens under dynamic loading conditions was performed. Eight intermediate-scale slabs were constructed and tested to failure under sequential high-mass low-velocity impact. The data from the testing program were used to verify the dynamic and FRC modelling procedures developed, and to contribute to a research area which is currently limited in the database of literature: the global response of RC and FRC elements under impact. Test results showed that the FRC was effective in increasing capacity, reducing crack widths and spacings, and mitigating local damage under impact. Analyses of the slabs showed that high accuracy estimates can be obtained for RC and FRC elements under impact using basic modelling techniques and simple finite element meshes.

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

Thesis (PhD) -- University of Western Sydney, 2001. / "A thesis submitted for the degree of Doctor of Philosophy in the University of Western Sydney." Bibliography: leaves 163 - 170.

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