Structural Design and Behaviour of PSC Beams Prestressed with 2160MPa / 2400MPa Steel Strand

This paper introduces newly developed 2160MPa / 2400MPa steel strand for prestressing and its application to PSC girders. Diameter of the strand is 15.2mm which is generally used in Asia and America. Nominal tensile strengths are increased up to 300kN and 333kN for 2160MPa and 2400MPa strand, respectively, from 261kN of 1860MPa strand. This paper reviews the feasibility in structural design aspect of the high strength strands, especially in terms of long-term prestressing losses due to creep, shrinkage of concrete and relaxation of steel. First, the structural design using simplified equations of KHBDC(Korea Highway Bridge Design Code) was compared with numerical analysis result using MIDAS for PSC beam with 2160MPa PS strand. Then, long-term prestressing losses calculated from design equations of KHBDC, Eurocode2 were compared for 35m long PSC beam according to the strength of PS strand(1860MPa/2400MPa). The comparison presented that simplified equations of KHBDC were conservative with no regards to the strength of PS strands and the high strength strands reduce long-term prestressing losses.