ACI 441R : High-Strength Concrete Columns: State of the Art
قیمت: 15000 تومان
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.