THESIS
2002
1 v. (various leaves) : ill. ; 30 cm
Abstract
Many concrete structures over the world have deteriorated through the corrosion of steel reinforcement. In concrete columns, corrosion often occurs preferentially on one side of the member, leading to unsymmetrical loss of steel area. For slabs, corrosion of bottom steel also results in reduction in steel reinforcement ratio....[
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Many concrete structures over the world have deteriorated through the corrosion of steel reinforcement. In concrete columns, corrosion often occurs preferentially on one side of the member, leading to unsymmetrical loss of steel area. For slabs, corrosion of bottom steel also results in reduction in steel reinforcement ratio.
The objective of this research is to study the effectiveness of repairing deteriorated concrete columns and slabs with fiber reinforced plastic (FRP) composite sheets.
Using steel reinforcements with reduced cross sections, concrete columns and slabs are cast to represent members with corroded steel bars. This research focuses on the repair of columns (circular and rectangular) and slabs (one way and two way) with different FRP configurations.
Circular and rectangular columns are retrofitted with horizontal and vertical FRP’s to study the strengthening effect. The columns are tested under uniaxial compression load. The failure mechanisms are reported. A simple analytical model to compute the failure load is also proposed. For circular columns, horizontal wrapping is found to be the most effective approach. For rectangular columns, one can either employ horizontal FRP alone or vertical FRP confined by external horizontal FRP.
Slabs with reduced steel area are tested in both one way and two way bending. Various repair configurations are studied, and the cracking and failure mechanisms are reported. For one-way slab, the H-type configuration, with two FRP strips bonded on the two sides of the region with reduced steel area, is found to be the most effective. To predict the failure load of the strengthened member, a simple analytical approach based on existing debonding models has been developed. Predictions are found to be in good agreement with test results. For two-way slab, two sheets of FRP with bond length 300mm bonded crossing each other at the centre of the slab is found to be more effective than the grid type with composite strips placed around the reduced steel region. In predicting the peak load of the retrofitted member, a simple analytical approach with assumed yield line pattern is also proposed.
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