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Retrofitting of Composite Steel Beams Pre-Damaged in Flexure using Fiber Reinforced Polymers

Karam, Ehab Clovis
A Master of Science thesis in Civil Engineering by Ehab Clovis Karam entitled, "Retrofitting of Composite Steel Beams Pre-Damaged in Flexure using Fiber Reinforced Polymers," submitted in May 2015. Thesis advisor is Dr. Rami Hawileh and thesis co-advisors are Dr. Jamal Abdalla and Dr. Tamer El Maaddawy. Soft and hard copy available.
The demand for the use of carbon-fiber-reinforced polymer (CFRP) composite sheets and plates is exponentially increasing in the rehabilitation of deteriorating steel-concrete composite beams across the Globe. The aim of this study is to investigate the performance of pre-damaged steel-concrete composite beams retrofitted with CFRP sheets and mechanically anchored with pultruded composite plates with high stiffness and bearing strength. A total of 10 composite steel-concrete beams were prepared and tested under two-point loading till failure. One beam was left undamaged to serve as a control specimen, while the remaining beams were divided into three groups, each consisting of three specimens and artificially damaged by cutting different notch depths of 5 mm, 8 mm and 11 mm in the bottom flange simulating corrosion damage levels of 45%, 73% and 100%, respectively. In each group, the first beam was tested without strengthening, the second specimen was externally retrofitted in flexure with CFRP sheets bonded with epoxy adhesives, and the third beam was strengthened in a similar fashion and mechanically fastened using the proposed composite pultruded plate system. The test results showed that the load-carrying capacity of the deteriorated specimens with different notch depths of 5 mm, 8 mm and 11 mm was reduced by 10.57, 21.52, and 49.1%, respectively. The strength of the repaired beam specimens with CFRP sheets ranged from 74.19 to 104.48% of that of the control undamaged beam, and ranged from 77.42 to 108.06% for the beams repaired with the proposed mechanical anchorage system. It was concluded that the proposed mechanically fastened repair system could fully restore the strength of damaged steel-concrete beams if the notch size at midspan is less than 50% of the bottom flange thickness. A finite element (FE) model was also developed that accurately simulated the response of some selected specimens. The developed models can be used in a future parametric study to investigate the effect of several parameters on the performance of the proposed retrofitting system.
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