Page 4 - Open-Access-May-2020

TECHNICAL PAPER

Performance of HigH-

StrengtH concrete

aS Jacket material

in StrengtHening

aPPlicationS Komathi murugan

amlan K. Sengupta

Abstract

A major advantage of high-strength concrete (HSC) is the
reduction in size of members in a reinforced concrete building.
The present research examines the application of HSC as a
jacketing material to increase the shear strength of columns.
Self-compacting concrete of two different strengths (high and
normal) was used to jacket twelve shear-critical beam-column
specimens. The details of specimen preparation, tests and
results are discussed in this paper. It was observed that the
use of HSC is suitable for increasing the shear capacity of
columns with thin jackets, with improvement in dowel action
of the added longitudinal bars and diagonal crushing strength
of the concrete. There was no undesirable increase in stiffness
as compared to the specimens jacketed with normal-strength
concrete. Figure 1: Concrete jacketing of a column (Courtesy: Engineering Unit,
IIT Madras, and Hitech Concrete Solutions Chennai Pvt. Ltd.)
Keywords: jacket; High-strength Concrete; Self-compacting
Concrete; Shear Capacity; Shear-critical. concrete (HSC) as the jacketing material. This is a local
retrofitting strategy, which is applied on selected individual
1. INTRODUCTION columns. The short columns can exist in the following situations.

Several disastrous earthquakes have occurred in the past. • In an open ground storey with low storey height,
Post-earthquake reconnaissance studies have reported severe used for car parking
damage to reinforced concrete (RC) structures along with • In the staircase in between a floor and the mid-level
casualties. These incidences have exposed the vulnerability landing
of existing structures to seismic forces. The vulnerability of
an existing structure can be ascertained based on a suitable • Next to a fenestration opening
condition assessment procedure. Retrofitting/strengthening of
existing structures for seismic forces at global and local levels, For such a column, the height to a lateral dimension ratio is
can reduce their vulnerability (Figure 1). A suitable retrofitting low. In absence of adequate amount of ties, it can have a brittle
scheme combining global and local strategies should be shear failure during an earthquake, compromising its capacity to
selected based on appropriate analyses of the pre-retrofit and carry gravity loads. Hence, such shear-critical columns need to
post-retrofit conditions of the entire structure, as well as of its be strengthened.
members.
HSC is preferred for jacketing based on minimal increase in size
The present research focused on the strengthening of short of the members, thereby limiting the reduction in floor area and
columns in RC multi-storied buildings, with high-strength increase in the mass of the structure. Since the jacket typically

The IndIan ConCreTe Journal | MaY 2020 5