Suitability of Fibre Reinforced Polymer Confined Concrete In-Filled Steel Tube Columns in Vulnerable Zones of Instability: A Case Study from Bhuj Earthquake Epicentral Zone, Gujarat, India

The present study aims to determine the suitability of fibre reinforced polymer confined concrete Infilled
steel tube columns in vulnerable zones of instability in the basement of Bhuj Earthquake
Epicentral Zone, Gujarat, India. Basement mapping is important to understand the subsurface
structural features in a sedimentary basin, which in turn pave a way for better insight of the tectonics.
It is important to plan all major civil structures based on the nature of the subsurface structure. In view
of identification of such zones and to find new ways of construction, a field experiment has been
carried out with a relatively new geophysical methodology – Magnetotellurics. A wide band (1000 -
0.001 Hz) magnetotelluric study has been taken up in the Bhuj earthquake epicentral zone and 21
sites have been occupied along three profiles during March-April 2001 to understand the deep
structure of the region. In addition, the region surrounding Bhuj has been probed earlier with number
of MT profiles and the subsurface structure is well constrained from hydrocarbon exploration point of
view besides seismotectonic studies. Structural damages occur in the columns due to the extreme
loading conditions and results in insufficient stiffness and ductility.
In the present study, we present the results of investigation in two phases. In phase I, the results
obtained along 130 km long profile from Mundra to Rapar oriented in NE-SW direction passing
through the epicenter are presented considering these databases. The subsurface structure has
shown interesting correlation with the surface deformations. A new basement configuration and
associated seismotectonics of the region has been identified. Our main result is relating the basement
configuration and surface ruptures. In phase II, our experimental study is extended to evaluate the
performance of Fibre reinforced polymer wrapped concrete in-filled steel columns subjected to lateral
loading in seismic regions. The parameters involved in this phase of investigation are the type of fibre
and shape of the steel tube. The results revealed that the Fibre reinforced polymer wrapped concrete
in-filled steel columns have higher load carrying capacity and energy absorption capacity and exhibit
ductile behavior when compared to columns. We recommend to follow these type of columns in civil
structures in the vulnerable zones identified from the first phase of our study. From the examination of
the surface deformations mapped at several locations around the epicentral zone and the basement
undulations from the present study an interesting correlation is observed. This has been explained
considering the tectonic forces acting on the weak sedimentary formations while the hard rock
basement is relatively stable.