本計畫總執行預計持續三年，第一年研究，主要是探討如何控制梁塑性鉸發生位置，以避免傳統塑性鉸發生在梁端貼近柱面位置之缺點。目前第二年正執行高拉力鋼筋受反覆拉壓測試，以及NEW RC梁耐震測試，用以觀察探討箍筋間距對NEW RC梁主筋挫屈影響。此次申請第三年，則主要探討NEW RC梁滑移剪力設計問題。第一年與第二年初步成果顯示，高拉力SD 690鋼筋防挫屈間距是以5db較佳，耐震行為與一般RC梁使用SD 420鋼筋之6db間距相近。在梁塑性鉸移轉設計方面結果，顯示所提出設計方式是可將塑性鉸成功地轉移而遠離柱面一倍梁深，以免造成梁柱接頭損傷而無法修補持續使用。但在實驗中也發現，有塑性鉸轉移的梁，相對地震引入剪力會提升約20%，在塑性鉸區有發現明顯滑移剪力裂縫，故如何檢核與設計，也引發本次申請計畫重點。本次所研究之梁滑移剪力設計，主要在ACI 318-14耐震設計章節並無相關說明，只是在一般規定中說明單向摩擦剪力設計，且鋼筋級數上限為SD 420鋼筋，對本研究所使用SD 690與SD 790鋼筋，是急待加以探討。再者，目前使用New RC會比較偏向於未來中高層建築大樓之預鑄工法，許多梁與柱冷縫對結構物耐震影響勢必要被重視，本主題研究成果亦可提供作參考。 ;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.
