Seismic Design of New Rc Beams Ⅲ-Design for Beam Sliding Shear

This sub-project is proposed in term of three years. The main goal of the first year is to investigate the design method for the plastic hinge relocation of New RC beams. The second year topic is now underway, focusing on the buckling behavior of the high strength SD690 reinforcing steel bars. The third year topic proposed will discuss the problem on how to design the sliding shear of New RC beams.Preliminary results on the projects for the first two years are: (1) the slenderness ratio of high strength steel reinforcement (s/db) is 5, whereas the traditional one for SD 420 steel bars is 6. (2) The hinge relocation design of New RC beams using additional high strength steel headed bars is available to successfully transfer the plastic hinge region from the column face to a distance of beam depth. However, the imposed shear demand of the relocated hinging beams is increased more than 20% of shear for the traditional beams. Thus, the final failure modes for the relocated hinging beams were turned to sliding shear failure. That is the reason why the third year topic is proposed focusing on the problem for the design of sliding shear.The sliding shear design specified in ACI 318-14 only stipulated in non-seismic chapter, called as frictional shear. Meanwhile, the steel bar grade limit specified up to SD 420 bars. Thus the sliding shear design for the high strength RC beams with SD 690 reinforcement is proposed by means of the research opportunity. Moreover, recent precast elements applied to the construction of high-rise buildings are facing a problem that those located in the potentially plastic hinge may harm the prototype behavior during earthquake. Therefore, the cold joint problem is also proposed to the project by this time.