Performance of FRP-strengthened reinforced concrete columns under impact loading
Abstract
The work presented herein focuses on studying experimentally and numerically the
behaviour of RC columns under the combined action of axial and lateral static or impact
loading, in particular when these members are strengthened with external sheets of
Carbon Fiber Reinforced Polymers (CFRP). In total, twenty-five RC column specimens
(un-strengthened and CFRP-strengthened) with identical dimensions have been tested.
Each specimen was first axially loaded to a predefined level and then subject to a three point bending test during which a lateral concentrated load was applied at mid-span.
The lateral load was applied either quasi-statically in the form of small increments up to
the specimen’s failure or dynamically by dropping a steel mass from a predefined
height. In the case of the un-strengthened specimens, the study mainly focused on
examining the effect of axial loading on the behaviour of the RC columns under lateral
impact. In the case of the strengthened specimens, the effect of different configurations
of CFRP sheets used for strengthening on the response of RC columns under static and
lateral impact loading was also investigated.
The experimental results have shown that the CFRP wrapping provides confinement to
the concrete which, in turn, reduces the sustained damage and increases the energy
absorbed by the strengthened specimens. The ultimate and residual mid-span deflections
decrease compared to those of the un-strengthened specimens indicating that the CFRP
sheets increase the stiffness of RC columns. Furthermore, as a consequence of the
smaller damage sustained by the strengthened specimens, the number of impact drops,
which these specimens can sustain before failure, increases.
In the numerical studies, a 3-dimensional finite element (FE) model has been developed
using commercial software ABAQUS to simulate the static and impact behaviour of RC
columns and validated using the experimental results. The Concrete Damage Plasticity
(CDP) model has been adopted to describe the concrete properties. The numerical
results have shown that the CDP model can predict reasonably well the response of RC
columns, including the crack pattern, under static and impact loading.