PRACTICAL ASPECTS OF POSTTENSIONING TO CONTROL END-REGION 5 CRACKS IN PRETENSIONED GIRDERS

摘要

Web-splitting cracking during and immediately after prestress transfer is an ongoing problem in the end region of pretensioned concrete beams. Current practices offer a variety of methods for controlling end-region cracking. This paper addresses a developing method with potential for preventing end-region cracking using vertical end-region posttensioning. Specifically, practical aspects associated with end-region posttensioning using threaded rods are discussed. These aspects include: i) application and validation of posttensioning force, ii) details for posttensioning rods, and iii) the effects of posttensioning losses. An experimental case study is also discussed, in which vertical posttensioning was successfully applied to inverted-tee beams. Variables in the case study included the quantity of posttensioning rods and the level of posttensioning. Results indicate that end-region posttensioning can reduce and delay web-splitting cracking in inverted-tee beams.