TESTS ON PRESTRESSED CONCRETE BEAMS

Abstract

Synopsis In this paper, the writer reports the results of investigations of the following tests which were carried out during the years from 1947 to 1952.(1) Static test on 17 beams of 7 different kinds manufactured by post-tensioning method.(2) Fatigue test on 44 beams of 6 kinds manufacturedd by pre-tensioning method.(3) Stress relaxation of high tensile steel wire under constant stress.(4) Creep tests on prestressed concrete beams.As a result of the test, the following points have been made clear:(1) Certain items regarding the executing devices and their making in the case of post-tensioning method, to which a special attention shall be paid.(2) Method of calculating the decrease of tension which occurs during the stretching process due to the following causes:(i) friction(ii) elastic deformation(iii) slippage at the anchor(3) Calculation formula of the ultimate strength for a post-tensioned prestressed concrete beam.(4) Regarding a beam manufactured by the post-tensioning method, the difference of the statical behaviour between the case where grouting is applied and that grouting is not applied.(5) Relation between static strength and fatigue strength of pre-stressed concrete beam(6) Allowable tensile stress at the lower fiber to prevent cracking due to fatigue.(7) Relation between the number of repititions, width, of crack and position of neutral axis.(8) Creep value of prestressed concrete beam and its calculation.(9) Standard for designing and executing the prestressed concrete beam.