Comparative Study on Experimental Behavior of R.C. Inverted Dapped-End Girders with Openings Strengthened by Vertical Normal Bolts
This paper is a part of some continuous researches done at Al-Mustansiriya university, college of engineering to investigate the behavior with comparison study of seven simply supported reinforced concrete inverted dapped-end beams and evaluate effectiveness of strengthening by vertical bolts working as post-tension normal strand bars under two point concentric loads. The investigated girders are of 1220 mm length,, 240 mm height and 130 mm width with different sections ( i.e. without or with transverse opening ). Five R.C. inverted dapped-end girders are strengthened by vertical bolts and nuts working as post-tension normal strand bars for both sections i.e. with or without opening. The main investigated variables are compressive strength, number of strengthening bolts (post-tension normal strand bars ratio), and effective type section (with and without opening). Test results show that when the compressive strength is increased by about 20%, an increase in strength capacity by about 10% is gained. Meanwhile, the section type i.e. the transverse opening in the reinforced concrete inverted dapped-end girders when compared with girders without openings results show a decrease in strength capacity and an increase in the girder deflection in ranges of (8-16%) and (15-20%), respectively. The third effect involves ratio of vertical bolts, which when used in strengthening they led to increase in ultimate strength capacity and decrease in corresponding deflection compared with other girders without bars by about (8-20%) and (20-30%). Furthermore, results show that only some of them provide significant load ultimate capacity increase. The observed failure modes ranged from a sudden failure up to the desired progressive failure of the strengthening system.