Mechanical Behaviour of Confined Circular Columns

Abstract

In this thesis columns with varying lateral reinforcement were confined with welded wire mesh externally as well as internally and test was conducted to study the effect of confinement on behaviour of columns. Six different samples were constructed in which Group 1 samples were constructed by varying lateral reinforcements and in Group 2 columns of different mix were constructed with same number of lateral reinforcement. Total 36 samples were constructed and tests were constructed in which it was observed that external confinement gives more axial deformation for same load capacity. For group 1 external confinement increases the load taking capacity as it can be observed that maximum increase in peak load was for columns with 3 rings (17%). In group 1 by using external confinement occurrence of peak load was delayed with respect to unconfined specimens. The increment was maximum for columns with 3 rings (32%). In group 1 peak was obtained earlier in comparisons to unconfined ones and very low percentage increase in load taking ability. For group 2 maximum increases in load capacity was for w/c 0.55 when confined internally (11%). For group 2 with w/c 0.55 shows increase in axial deformation at peak load (42%). External confinement provided more ductility. In group 1 it was also observed that external confined column with 3 and 2 rings have similar ultimate load capacity as compared to unconfined 3 and 2 rings columns respectively. There was increase in energy absorption for group 2 column having w/c 0.55 (52%). In order to enhance ultimate load capacity in large scale columns can be confined by using double or triple layer of WWM. Also diameter of wire can be increased and orientation of mesh opening can be changed i.e. using diagonal openings. Increasing the proportion of aggregate with nominal size 10mm increases concrete homogeneity which assists in achieving high increments in ultimate load capacity.