Yuya KOMATSU

Development of Post Tension PC Members with Stainless Steel Anchorages

Takumi SHIMOMURA

In this study, in order to construct post-tension PC structures with non-corrosive materials, stainless steel anchorages were developed, PC beams were fabricated using these anchorages, and bending load tests were conducted.
Development of stainless steel anchorage.
The goal of satisfying a fusing efficiency of at least 95% was quickly achieved. However, it was difficult to achieve the goal of not causing the anchorage to break or deform significantly under the specified tensile load of the tension material. The use of quenched and tempered SUS420J2 for the wedge and annealed SUS420J2 for the anchor head resulted in an unbreakable anchorages fixture.
A prototype beam made entirely of stainless steel was fabricated using the developed stainless steel anchorages, and prestress reduction measurements and bending loading tests were conducted. The set was greater for the stainless steel anchorage, but the relaxation was equivalent to that of ordinary steel. In the flexural loading test, the ultimate load was lower for the stainless steel beams due to the lower stiffness of the steel compared to that of the regular steel beams, but there was no significant difference compared to the regular steel beams, and the difference in shear span had no effect on the results. The test results were well reproduced by analysis. The prototype stainless steel fixture was able to anchor without failure until the end of the test period, and there was no steel retraction.
Based on the results of the bending loading tests, some points to be considered when stainless steel is used for post-tensioned PC structures are discussed. When designing a member, the load-elongation relationship of a stainless steel PC strand can be considered and the member can be designed in the conventional manner. However, unlike ordinary steel strands, stainless PC steel strands have a low elongation at break, which must be taken into consideration. In particular, for safety reasons, it is necessary to check the ultimate strain of the steel to ensure that it will not break at the end of its life. The tensile stress of steel under tension and immediately after tensioning should be determined in accordance with the conventional rules.