초고성능 콘크리트를 적용한 프리캐스트 보의 접합부 설계

Abstract

Since the precast structure assembles the members made in the factory on site, it is not easy to secure the structural performance to resist earthquakes compared to the integrated cast-in-place concrete structure compared to the cast-in-place concrete structure. This study examines the existing precast joint design, and based on this, proposes the design strength formula of the precast joint to which UHPC is applied and the design strength of the precast beam. Therefore, the material properties were studied through the mechanical experiment of ultra-high-performance concrete materials, and the joint design formula of precast concrete beams to which ultra-high-performance concrete was applied was proposed. To verify this, a bending fracture type precast beam and a shear fracture type precast beam were manufactured and tested. The proposed formula was verified by comparing the result obtained through the experiment with the design value through the proposed formula. As variable conditions in the study, the joint length was 100mm and 120mm at the joint with non-shrinkable mortar, high-performance concrete, and 1.5% of steel fiber mixed in the joint and the joint with a loop joint type. As a result of the experiment, the initial cracking load, maximum load, and maximum strength of precast beams to which high-strength concrete and ultra-high-performance concrete were applied were higher than general concrete beams and precast beams to which non-shrinkage mortar was applied. There was little difference in the result values ​​according to the length of the loop joint. Similar results were obtained when the proposed formula and the experimental values ​​proposed in this study were compared, but overall, the values ​​were slightly lower than the experimental values. However, considering that the design formula is conservative, it is considered to be an appropriately estimated result.