The Influence of the Compression Interface on the Failure Behavior and Size Effect of Concrete

• Other Authors: Kampmann, Raphael, 1980- (authoraut)
• Format: Others
• Language: English; English
• Published: Florida State University
• Subjects: Engineering
• Online Access: http://purl.flvc.org/fsu/fd/FSU_migr_etd-5375

The failure behavior of concrete materials is not completely understood because conventional test methods fail to assess the material response independent of the sample size and shape. To study the influence of strength and strain affecting test conditions, four typical concrete sample types were experimentally evaluated in uniaxial compression and analyzed for strength, deformational behavior, crack initiation/propagation, and fracture patterns under varying boundary conditions. Both low friction and conventional compression interfaces were assessed. High-speed video technology was used to monitor macrocracking. Inferential data analysis proved reliably lower strength results for reduced surface friction at the compression interfaces, regardless of sample shape. Reciprocal comparisons revealed statistically significant strength differences between most sample shapes. Crack initiation and propagation was found to differ for dissimilar compression interfaces. The principal stress and strain distributions were analyzed, and the strain domain was found to resemble the experimental results, whereas the stress analysis failed to explain failure for reduced end confinement. Neither stresses nor strains indicated strength reductions due to reduced friction, and therefore, buckling effects were considered. The high-speed video analysis revealed localize buckling phenomena, regardless of end confinement. Slender elements were the result of low friction, and stocky fragments developed under conventional confinement. The critical buckling load increased accordingly. The research showed that current test methods do not reflect the ''true'' compressive strength and that concrete failure is strain driven. Ultimate collapse results from buckling preceded by unstable cracking. Suplemental Files: Additional video files, that supplement the test results presented in Chapter 4, can be accessed through the Florida State University Library System. The high-speed videos were selected to exemplify each specimen type (tall cylinder, small cylinder, column, and cube) under both boundary conditions (conventional and reduced surface friction). 01_TallCylinderConventionalFriction.mp4 - Tall cylinder under conventional friction 02_TallCylinderReducedFriction.mp4 - Tall cylinder under reduced friction 03_SmallCylinderConventionalFriction.mp4 - Small cylinder under conventional friction 04_SmallCylinderReducedFriction.mp4 - Small cylinder under reduced friction 05_ColumnConventionalFriction.mp4 - Column under conventional friction 06_ColumnReducedFriction.mp4 - Column under reduced friction 07_CubeConventionalFriction.mp4 - Cube under conventional friction 08_CubeReducedFriction.mp4 - Cube under reduced friction === A Dissertation submitted to the Department of Civil and Environmental Engineering in partial fulfillment of the requirements for the degree of Doctor of Philosophy. === Fall Semester, 2012. === September 19, 2012. === compression, concrete, crack, failure, fracture, high-speed video === Includes bibliographical references. === Michelle Rambo-Roddenberry, Professor Co-Directing Dissertation; Wei-Chou Virgil Ping, Professor Co-Directing Dissertation; Peter N. Kalu, University Representative; Kamal Tawfiq, Committee Member.