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Review Study on re-strengthening of reinforced concrete circular column using steel strips

Rahul Rakshe


This technique fixes thin steel plates i.e. steel encasement or tie plates i.e. steel cage around the column with steel angles at each corner, clamped to the concrete and welded together. Adequate tightening of the jackets can be ensured by means of heat tensioning. The use of steel jackets can enhance the shear strength of columns considerably. However, due to their low flexural stiffness they typically have poor confinement efficiency for square and rectangular columns. This limits the effectiveness of the system for increasing the deformability of the columns.
• Results in significant increase of member stiffness

• Increase the ductility of structure and enhances lateral response of structure

• Requires interruption of the use of structure
Steel collar ties are placed around the column and are densely spaced over the damaged area. Corners of existing columns are protected by steel angles and a light wire mesh is placed on all four edges with a gunite jacket of at least 50mm. As the collars are screw tightened, the tension force in the steel collar exerts an active confining stress on the column. Externally collared columns can exhibit an improved performance compared to conventionally reinforced ones as the area of confined concrete is increased and spalling can be prevented. With the increase in collar spacing, the confinement effectiveness is reduced.

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