EXPERIMENTAL PERFORMANCE OF HSC COLUMNS UNDER CYCLIC LOADS Y. H. HAMMAD 1 ; M. EISSA 2 ; G. T. ABDEL-RAHMAN 3 and M.SAID 4 1 Professor of Reinforced Concrete Structures, Faculty of Engineering in Shoubra, Benha Univ., Egypt 2 Professor of Reinforced Concrete Structures, Faculty of Engineering, Cairo University, Egypt 3 Associate Professor, Civil Engineering Dept., Faculty of Engineering in Shoubra, Benha Univ., Egypt 4 Assistant Lecturer, Civil Engineering Dept., Faculty of Engineering in Shoubra, Benha University, Egypt ثΤΒ الصΨϠ م افѧ ألييѧϠ عϱوѧتΤ تيѧ التΔѧاومϘϤ الΔѧ عاليΔانѧرسΨ الΕاΫ ΓΪѧϤ لاعائيѧانش اϙوϠѧ السرفѧ تصΔѧاسέΪ لثΤΒ الاά ھفΪ يھ .ΩوѧϤ العاعѧتفέ افѧتصϨ مΪѧϨ عϩاѧاتج اΓرѧ متغيهѧيέوΩ ϝاѧϤ وأحΔѧيέوΤϤ الϝاѧϤاح ااثيرѧ تتѧΤ تΕاناϜ بΓΪيϘϤ والبϠ الص ) ΩΪعέاΒ اخت تم حيث14 بأهϨ عي( ) Ω بعا0.20 * 1.80 * 1.80 ϙوϠѧ سϰѧϠ عؤثرѧ تيѧ التΕراѧتغيϤ الضѧ بعΔѧاسέΩ مѧ تΪѧ وق( Ϊѧ وق.ΔѧيέوΤϤ الϝاѧϤاح اΔΒѧ نس،ΔانѧرسΨ الΩاѧ اجھΔѧϤ قي،ΕاѧϨ العييѧ فبϠѧ الصافѧ أليΔΒѧ نسختاف ا: ھاϨ ومΕاϨ العيϩά ھ السنΤ وتΥ التشرϝاϤ واحϱصوϘ الϝاϤاح اΔϤ قيΪ تزيبϠ الصلياف اϡاΪΨ استϥ اتائجϨ الΕھرυ اΪѧ وقΓΪϤ لاعΔوليτϤϤ ھيبϠ الصلياف لاΔΒ نس افضلϥ اتائجϨ الΕھرυ ا1.5 الراسيلϤΤ ال تاثيرϥوϜ يϥ ا يفضل انهتائجϨ الΕΪ اكاϤ ك.% ΪѧϨ عΔѧاومϘϤ الΔѧ عاليΔانѧرسΨ الΕاΫ ΓΪѧϤ اع نتائجيϠ عΓΪϤ معتΩكواا ا فيΔتاحϤ الΔلΩعاϤ الϥوϜ تϥواέاΒاعت ا فيΫ مأخو ΔوليτϤϤ الΓΪϤاع ايمϤ تص. ABSTRACT The behavior of high strength concrete columns; HSCC with steel fibers under cyclic loading was investigated. Fourteen half-scale column specimens were tested under cyclic lateral load. The key variables covered in this investigation include the steel fibers ratio ranging from 0.00% to 1.50%. The concrete strength varied from 50 MPa to 100 MPa. The columns were subjected to constant axial loads corresponding to target values of 10%, 25% and 45% of the column axial-load capacity. The confinement index values were 0.122, 0.230 and 0.392. The columns were designed according to seismic requirements of ACI 318 Code. The study present that the steel fibers is shown to improve the performance and ductility of HSC columns. Column with 80% higher amounts of transverse reinforcement than that required by seismic provision of ACI 318-08 and with steel fiber content 1.5% showed ductile behavior and higher ultimate capacity. The results indicated that increasing the axial load level from 10 to 45 percent reduced the maximum displacement by 34 percent. The need to include the axial-load level in ACI Code requirements for confinement reinforcement is pointed out. KEYWORDS: HSC, HSCC, Fibers, Ductility, Drift, Columns, Cyclic. 1. INTRODUCTION The use of high-strength concrete has been steadily increasing due to its many advantages over normal-strength concrete. HSC is used primarily in high-rise buildings to significantly decrease the dimensions of the columns in lower stories, thereby reducing the volume of concrete. Studies have shown, however, that HSC is more brittle than NSC [1, 2]. Brittle behavior of high strength concrete in compression has to some extent, limited its application in seismically active regions. Commonly, to overcome the adverse effect of such brittleness on the column behavior, thoughtful confinement is adopted. The