{"640034":{"#nid":"640034","#data":{"type":"event","title":"PhD Defense by Koochul Ji","body":[{"value":"\u003Cp\u003E\u003Cstrong\u003EPh.D. Thesis Defense Announcement\u003C\/strong\u003E\u003C\/p\u003E\r\n\r\n\u003Ch1\u003ENumerical modeling of mechanical recovery in damaged concrete repaired by epoxy at molecular and metric scales\u003C\/h1\u003E\r\n\r\n\u003Ch1\u003E\u0026nbsp;\u003C\/h1\u003E\r\n\r\n\u003Ch1\u003Eby\u003C\/h1\u003E\r\n\r\n\u003Ch1\u003EKoochul Ji\u003C\/h1\u003E\r\n\r\n\u003Ch1\u003E\u0026nbsp;\u003C\/h1\u003E\r\n\r\n\u003Ch1\u003EAdvisor(s):\u003C\/h1\u003E\r\n\r\n\u003Ch1\u003EDr. Chloe Arson (CEE)\u003C\/h1\u003E\r\n\r\n\u003Ch1\u003E\u0026nbsp;\u003C\/h1\u003E\r\n\r\n\u003Ch1\u003ECommittee Members:\u003C\/h1\u003E\r\n\r\n\u003Cp\u003EDr. Susan E. Burns (CEE), Dr. Kimberly E. Kurtis (CEE), Dr. Lauren K. Stewart (CEE), Dr. Olivier Pierron (ME)\u003Cstrong\u003E\u0026nbsp;\u003C\/strong\u003E\u003C\/p\u003E\r\n\r\n\u003Cp\u003E\u003Cstrong\u003EDate \u0026amp; Time: \u003C\/strong\u003EOct. 22, 2020 at 2.30pm\u003C\/p\u003E\r\n\r\n\u003Cp\u003E\u003Cstrong\u003ELocation: \u003C\/strong\u003E\u003Ca href=\u0022https:\/\/bluejeans.com\/854653129?src=join_info\u0022\u003Ehttps:\/\/bluejeans.com\/854653129?src=join_info\u003C\/a\u003E\u003C\/p\u003E\r\n\r\n\u003Cp\u003E\u0026nbsp;\u003C\/p\u003E\r\n\r\n\u003Cp\u003E\u0026nbsp;Complete announcement, with abstract, is attached\u003C\/p\u003E\r\n\r\n\u003Cp\u003EAlmost half of the U.S. bridges will require a major structural investment within the next 15 years. Naturally,\u003Cbr \/\u003E\r\nthe importance of preventive design and maintenance was stressed in many previous studies that aimed to\u003Cbr \/\u003E\r\nassess reparation techniques. Due to its economical and practical benefits, polymer injection is widely\u003Cbr \/\u003E\r\nemployed to repair cracks in concrete structures. In this thesis, we investigate the mechanisms of\u003Cbr \/\u003E\r\nmechanical recovery in concrete repaired by epoxy at atomic and metric scales.\u003Cbr \/\u003E\r\nThe first part of the thesis presents Molecular Dynamics (MD) models of High Molecular Weight\u003Cbr \/\u003E\r\nMethacrylate (HMWM). MD pull-out tests on calcite\/HMWM and silica\/HMWM interfaces show that the\u003Cbr \/\u003E\r\ntensile strength of concrete\/HMWM interfaces is optimal in dry conditions and at low temperatures, and\u003Cbr \/\u003E\r\nthat silica\/HMWM interfaces are stronger than calcite\/HMWM interfaces. Richeton\u0026#39;s model and Johnson-\u003Cbr \/\u003E\r\nCook model are employed to predict the tensile modulus of HMWM and the interfacial strength between\u003Cbr \/\u003E\r\nHMWM\/concrete minerals at a low strain rate. In order to investigate the effect of interlocking on interface\u003Cbr \/\u003E\r\nshear strength, we simulate shear deformation tests with silica\/polymer interfaces, in which the substrate is\u003Cbr \/\u003E\r\neither smooth or rough. Longer polymer chains promote higher strength but impede notch filling. Rough\u003Cbr \/\u003E\r\ninterfaces are in average 1.5 stronger than smooth ones. In both mode I and in mode II, MD results\u003Cbr \/\u003E\r\nindicate that the work of separation is mostly attributed to van der Waals forces.\u003Cbr \/\u003E\r\nIn the second part of the thesis, we present a numerical modeling approach based on the Finite Element\u003Cbr \/\u003E\r\nMethod (FEM), in which HMWM joints and cracks repaired by HMWM are represented by cohesive zone\u003Cbr \/\u003E\r\nelements and concrete, by a damage-plasticity model. The model is calibrated against experimental results\u003Cbr \/\u003E\r\nobtained on cut and sealed concrete specimens and verified against data on reinforced concrete (RC)\u003Cbr \/\u003E\r\nbeams and Pre-Stressed Concrete (PSC) beams. Simulation results suggest that HMWM can penetrate\u003Cbr \/\u003E\r\ncracks of width 0.01 mm and above by gravity. We also find that HMWM reparation increases concrete\u003Cbr \/\u003E\r\nstiffness and strength if cracks in concrete members are over 0.1 mm in width, in which case, the load\u003Cbr \/\u003E\r\ncapacity of repaired RC beams is 30 to 40% higher than that of as-built RC beams. We also simulate prestressing,\u003Cbr \/\u003E\r\nstrand release, and four-point loading of PSC girders. We find that the load capacity of a PSC\u003Cbr \/\u003E\r\ngirder damaged by pre-stressing and then repaired would be about 7% higher than that of the as-built PSC\u003Cbr \/\u003E\r\ngirder.\u003C\/p\u003E\r\n","summary":null,"format":"limited_html"}],"field_subtitle":"","field_summary":"","field_summary_sentence":[{"value":"Numerical modeling of mechanical recovery in damaged concrete repaired by epoxy at molecular and metric scales "}],"uid":"27707","created_gmt":"2020-10-08 20:09:28","changed_gmt":"2020-10-08 20:09:28","author":"Tatianna Richardson","boilerplate_text":"","field_publication":"","field_article_url":"","field_event_time":{"event_time_start":"2020-10-22T15:30:00-04:00","event_time_end":"2020-10-22T17:30:00-04:00","event_time_end_last":"2020-10-22T17:30:00-04:00","gmt_time_start":"2020-10-22 19:30:00","gmt_time_end":"2020-10-22 21:30:00","gmt_time_end_last":"2020-10-22 21:30:00","rrule":null,"timezone":"America\/New_York"},"extras":[],"groups":[{"id":"221981","name":"Graduate Studies"}],"categories":[],"keywords":[{"id":"100811","name":"Phd Defense"}],"core_research_areas":[],"news_room_topics":[],"event_categories":[{"id":"1788","name":"Other\/Miscellaneous"}],"invited_audience":[{"id":"78761","name":"Faculty\/Staff"},{"id":"78771","name":"Public"},{"id":"174045","name":"Graduate students"},{"id":"78751","name":"Undergraduate students"}],"affiliations":[],"classification":[],"areas_of_expertise":[],"news_and_recent_appearances":[],"phone":[],"contact":[],"email":[],"slides":[],"orientation":[],"userdata":""}}}