Infrastructure Engineering - Theses

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End date: 1999 × Start date: 1995 × Type: Masters Research thesis × Subject: concrete columns ×

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    Flexural ductility of high strength concrete columns
    Kovacic, Daniel Antony ( 1995)
    A method for the design of reinforced high strength concrete columns considering the flexural ductile behaviour is presented in this thesis. High strength concrete, as used in this study, is defined as concrete with compressive strengths exceeding 50MPa. The study covers the following areas: A concrete stress-strain model previously used for normal strength concrete column analyses is presented along with a modification to include the characteristic behaviour of high strength concrete. The thesis also gives a literature review of the available information on the performance of high strength concrete columns. An experimental investigation of the influence of concrete strength, stirrup spacing, axial load level, and the percentage of longitudinal steel on the stress-strain and movement-curvature behaviour of confined concrete is presented. The test units included eight rectangular columns of compressive strengths ranging from 30 to 65MPa. The available strength and ductile behaviour of the columns is discussed and compared with the performance of columns tested previously at the University of Melbourne and Monash University, as well as with various analytical models, including the modified concrete stress-strain model mentioned above. A method for the determination of stirrup spacing resulting in equivalent ductile performance to that specified by the current Australian Concrete Code (AS3600) is presented. A set of criteria for the ultimate limit state including longitudinal steel buckling and lateral steel fracture was used to establish a design method for the available strength and ductility of high strength concrete columns. The effect of concrete cover on ductile behaviour is also discussed. Various spreadsheets were developed to determine such parameters as concrete strain at lateral steel fracture and strain at longitudinal steel buckling. A spreadsheet which determines the stirrup spacing of a column as specified by various codes and research reports was also developed. Two fortran computer programs which determine the axial force - moment interaction diagram and the moment-curvature curve of a reinforced concrete section were modified to include new stress-strain relationships suitable for high strength concrete and ductility measurements.