energy is computed as the area under the axial load versus axial
deflection curve, as used by several researchers [26–28]. It is
observed that the confined specimens absorb more energy than
that of unconfined specimens. The specimens confined with single
layer mesh ferrocement jacket absorb more than double the energy
absorbed by the unconfined specimens. The energy absorption
capacity of double layer mesh ferrocement jacketed specimens is
more than 1.4 times the energy absorbed by the single layer mesh
confined specimens. It is also observed that MS specimens absorb
more energy than SS and LS specimens irrespective of ferrocement
confinement type.
4. Analytical model
4.1. Confinement mechanism
The external ferrocement jacket provides a passive form of confinement
to the internal concrete core. Thus, the confining pressure
is developed only after the core concrete undergoes lateral bulging
due to the Poisson’s effect. Therefore, the bulging properties of concrete
and the stiffness of the external jacket to restrain the bulging
dictate the overall confinement mechanism. Accordingly, the strain
compatibility between the core and external jacket; and the force
equilibrium in any section of confined concrete must be satisfied.
Fig. 7 shows a typical free body diagram of circular ferrocement
confined concrete. The force equilibrium will give the expression
of the confining pressure (fcf) in the following form: