高張力鋼棒を用いたPC桁の亀裂荷重と疲労強度

Abstract

Literatures show that very few tests have been made on the fatigue strength of prestressed concrete beams. This paper reports the results of fatigue and static tests on two kinds of posttentioned prestressed concrete beams. The Losenhausen fatigue testing machine was used for these tests.The distinctive characteristics obaiined from this investigation are as follows;1) All the steel bars used for prestressing the beams are of high strength steel having the ultimate strength of over 100kg/mm2.2) The upper limit of repeating load is larger than the cracking load of the prestressed beams found in static test.The main results obtained in this experiment are;1) The fatigue strength at N=6.4×105 is 130% of the cracking strength.2) The fatigue strength at N=6.4×105 is 60% of the statical ultimate strength.3) When the upper load of fatigue test is below the fatigue strength at N=6.4×105, the statical ultimate strength is little affected by the repeated loading subejected before the statical test.4) When the upper load of fatigue test is over the fatigue strength, the dynamic deflection and compressive strain during fatigue test increase with the numbers of repetition, and when the upper load of fatigue test is below the fatigue strength, they are almost constant irrespective of the numbers of repetition.