Date of Award

Fall 2020

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Civil, Construction, and Environmental Engineering

First Advisor

Wan, Baolin

Second Advisor

Heinrich, Stephen M.

Third Advisor

Karshenas, Saeed

Abstract

External bonding of fiber reinforced polymer (FRP) composite materials has been widely recognized as a popular technique for strengthening concrete structures. To find advanced strategies to improve the bond behavior of externally bonded composites strengthened concrete, three major tasks were conducted in this study: experimental work, finite element (FE) analysis, and reliability analysis. The mechanical properties and the deterioration due to water absorption of carbon nanofibers (CNFs) epoxy composites with different contents of CNFs were tested through uniaxial tensile test. According to the tensile test results, adding CNFs could significantly enhance the tensile behavior for epoxy resin. Because adding proper content of CNFs into epoxy could create longer water diffusion paths, CNFs epoxy performed better than pure epoxy to resist the deterioration of mechanical properties in moist environment. Two 3D FE models, i.e., the external bonding of FRP composite materials with epoxy interlocking (EB-FRP-EI) model and the prestressed hollow-core slabs strengthened with laminated bamboo (LB) plates model were developed. By comparing the load vs. slip relationships and cracking patterns with experimental results, both FE models were validated. The validated FE models were then used to investigate the key parameters that may affect the performance of EB-FRP-EI and the flexural behavior of the LB plate strengthened prestressed hollow-core slabs. The FE analysis showed that increasing the number of grooves could significantly improve the performance of epoxy interlocking enhancement, and enlarging the width and thickness of laminated bamboo plate could improve flexural performance of laminated bamboo plate strengthened prestressed hollow-core slabs. The reliability analysis of EB-FRP-EI was conducted, and then the reliability-based design guideline for selecting the depth and number of grooves was performed with 28 design points (7 × 4) in total, in which the proper depth and number of grooves could be achieved. The effects of design parameters including depth of grooves, number of grooves, thickness of FRP, width of FRP and strength of concrete on reliability performance of EB-FRP-EI were presented and discussed. As a result, this study provides suggestions for proper design of FRP-concrete joints with epoxy enhancement based on these design parameters.

Available for download on Saturday, December 18, 2021

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