Chapter: Civil : Repair and Rehabilitation of Structures : Repairs, Rehabilitation and Retrofitting of Structures
Deflection due to Strengthening of columns
Deflection due to Strengthening of columns
Jacketing is the process of
fastening a durable material over concrete and filling the gap with a grout
that provides needed performance characteristics.
The column jacket can also be used for increasing
the punching shear strength of column slab connections by using it as a column
capital. When the jacket is provided around the periphery of the column, it is
termed a collar. In most of the applications, the main function of the collar
is to transfer vertical load to the column. Circular reinforcement can be used
for load transfer. The practice of transferring load through dowel bars
embedded into columns or shear keys has a disadvantage in that they require
drilling of holes for dowels or cutting shear keys which are costly and time
consuming, and can damage the existing column. Reinforcement encircling the
column can be used to transfer the load through shear friction. The expansion
of collar as it slides along the roughened surface causes the tensioning of
circular reinforcement resulting in radial compression, which provide normal
force needed for load transfer. The shear transfer strength is provided by both
frictional resistance to sliding and dowel action of reinforcement crossing the
crack.
The collar is subjected to shear
and bending along the collar circumference as well as direct bearing stress
under concentrated load. In addition shear transfer reinforcement, the collar
should be provided with reinforcement for shear and moment within collar.
Column collars can be provided below the slab to act as column capital to
improve punching shear strength of the slab column connection
Related Topics