Browsing by Author "Dawood, Mina Magdy Riad"

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    Bond Characteristics and Environmental Durability of CFRP Materials for Strengthening Steel Bridges and Structures
    (2008-08-19) Dawood, Mina Magdy Riad; Dr. Sami Rizkalla, Committee Chair; Dr. Emmett Sumner, Committee Member; Dr. Murthy Gudatti, Committee Member; Dr. Kara Peters, Committee Member
    This dissertation presents the findings of a research program that was conducted in two parts to investigate the bond behavior and environmental durability of carbon fiber reinforced polymer (CFRP) materials for strengthening steel bridges and structures. The first part of the research consisted of an experimental and analytical research program to investigate the bond characteristics of CFRP lap-splice joints. The experimental program included a total of eight double-lap shear tests and ten steel beam tests. The main parameters considered include the geometric configuration of the plate ends, the length of the splice plates and the use of mechanical anchorage near the plate ends. A finite element analysis was conducted to determine the distribution of the stresses within the adhesive layer for different splice configurations. The findings indicate that the presence of the reverse tapered plate end reduced the magnitude of the peak stresses in the adhesive layer thereby increasing the tension strength of the splice joints. Increasing the splice length and installing additional mechanical anchorage did not enhance the strength of the joints. Based on the findings, a method is proposed to design lap-splice joints for implementation of the proposed CFRP system on longer-span flexural members. The second part of the research consisted of a total of 44 steel-CFRP double-lap shear tests to study the environmental durability of the proposed CFRP strengthening system. The specimens were exposed to accelerated corrosion conditions and subsequently loaded monotonically to failure. The additional use of a silane adhesion promoter or a glass fiber insulating layer, to enhance the bond durability, was also studied. The findings indicate that the presence of the glass fiber layer enhanced the initial bond strength of the system, while the use of a silane adhesion promoter was essential to ensure the durability of the system. The findings of this research program demonstrate that, with proper detailing, the proposed CFRP system can be effectively used for strengthening of steel bridges and structures.
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    Fundamental Behavior of Steel-Concrete Composite Beams Strengthened with High Modulus Carbon Fiber Reinforced Polymer (CFRP) Materials
    (2005-06-30) Dawood, Mina Magdy Riad; Dr. Emmett Sumner, Committee Member; Dr. Vernon Matzen, Committee Member; Dr. Sami Rizkalla, Committee Chair
    There is a growing need for a cost-effective, durable repair system that can be used for the repair and strengthening of steel bridges. Recently, high modulus carbon fiber reinforced polymers (CFRP) have been developed with a modulus of elasticity approximately two times greater than that of steel. Externally bonded high modulus CFRP materials have successfully been used to increase the elastic stiffness and ultimate capacity of steel-concrete composite beams However, since the technology is relatively new, the detailed behavior of steel bridge members strengthened with high modulus CFRP is not yet well understood. The current research investigates three aspects of the behavior of steel-concrete composite beams in detail. An experimental program was conducted to investigate the behavior of steel-concrete composite beams strengthened with high modulus CFRP materials. In the first phase of the study the behavior under overloading conditions was investigated. In the second phase of the research, the fatigue durability of the system was examined. In the third phase, the possible presence of shear-lag between the steel beam and the CFRP materials was investigated in detail. An analytical model was developed which can be used to determine the ultimate capacity and elastic stiffness increase for steel beams strengthened with high modulus CFRP materials. Additionally, a set of criteria are proposed which can be used to determine the allowable increase in the live load level for steel beams strengthened with high modulus CFRP materials.