Strength of shear section pre-tensioned concrete structures subjected to flexural moments

Abstract

Steel strands as reinforcement for concrete structures are used in many cases without additional anchorage. In such cases the length of anchorage of the strands is quite long and in the support part of the beams there is a zone in which the strands are not completely introduced in interaction with the concrete. In strength calculations of the support zone reduction in strength and prestressing force provided by the longitudinal reinforcement has to be taken in to account. Flexural resistance of reinforced concrete flexural member at this zone is less than that in the other parts. Therefore, in spite of the quite small value of the acting bending moment, such support zone can fail due to the action of this particular bending moment The influence of the bending moment and anchorage length of prestressed reinforcement on the strength of shear section of concrete structures is analyzed in this paper. Theoretical investigations in the strength of shear section of prestressed concrete flexural members taking into account the anchorage length, prestressing force and transverse reinforcement were performed. It was determined by investigations that in design of such structures the decrease in effect of longitudinal reinforcement must be compensated by an adequate amount of shear reinforcement. Results of theoretical investigations indicated that the strength of concrete structures under the action of sufficiently large loads is governed by the resistance of the shear section to the action of the bending moment. Hollow core prestressed concrete slabs were tested. A comparison of the results obtained by experiments and by theoretical calculations of prestressed concrete stabs was made.