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Description / Abstract:
One application of high-strength concrete (HSC) has been in the
columns of buildings. In 1968 the lower columns of the Lake Point
Tower building in Chicago, Illinois, were constructed using 52 MPa
concrete.1 More recently, several high rise
buildings1-4 have utilized concrete with compressive
strengths in excess of 100 MPa in construction of columns.
Many studies4-9 have demonstrated the economy of
using HSC in columns of high-rise buildings, as well as low to
mid-rise buildings.10 In addition to reducing column
sizes and producing a more durable material, the use of HSC has
been shown to be advantageous with regard to lateral stiffness and
axial shortening.11 Another advantage cited in the use
of HSC columns is reduction in cost of forms. This is achieved by
using HSC in the lower story columns and reducing concrete strength
over the height of the building while keeping the same column size
over the entire height.
The increasing use of HSC caused concern over the applicability
of current building code requirements for design and detailing of
HSC columns. As a result, a number of research studies have been
conducted in several countries during the last few years. The
purpose of this paper is to summarize major aspects of some of the
reported data.
The major objectives of reported studies have been to
investigate the validity of applying the current building code
requirements to the case of HSC, to evaluate similarities or
differences between HSC and normal-strength concrete (NSC) columns,
and to identify important parameters affecting performance of HSC
columns designed for seismic as well as non-seismic areas. These
concerns arise from the fact that requirements for design and
detailing of reinforced concrete columns in different model codes
are primarily empirical and are developed based on experimental
data obtained from testing column specimens having compressive
strengths below 40 MPa.
The reported information can be divided into two general
categories: performance of HSC columns under concentric axial load;
and performance of HSC columns under combined axial load and
bending moment. This report gives the highlights of the reported
data in each of these categories. In this report, HSC is defined as
concrete with compressive strength greater than 70 MPa.