The present study deals with an experimental (EXP) and finite element (FEA) investigation for
studying internal confinement during construction by using stirrups densification at top and
bottom of columns and the regular stirrups distribution along length of columns with different
slenderness ratio (λ). Also, it deals with the effect of external confinement for damaged (RC)
columns by using steel jacketing technique with a various percentage of covered steel surface
area to column surface area (36,42,50,57 and 64). A total of twenty reinforced concrete
columns specimens having a cross section of 125 x 250 mm and a different slenderness 6, 8, 10
and 12 have been tested. Columns were divided in two stages; First stage tested four columns
to studying internal confinement during construction. It consists of four column specimens
with a different slenderness ratio 6, 8, 10 and 12 tested. The results in first stage; give a
decrease in the load carrying by increasing the slenderness ratio.
The increase in internal stirrups volumetric ratio by using densification of stirrups along of
column resulted in higher ultimate load. The failure of columns caused due to spall off concrete
after stirrups densification zone, thus signifying the large stress concentration after
densification directly. Second stage tested twenty columns until failure to study the internal
and external confinement for damaged (RC) columns. All damaged concrete parts were
removed and replaced the loose concrete part with grout mortar and retrofitted by using steel
straps jacketing technique. The steel jacket consists of four vertical steel angles placed at each
corner of column and connected together with horizontal steel straps. The results in second
stage; gives an increases in the column carrying capacity by increasing percentage of covered
steel surface area to column surface area and decrease by increasing slenderness ratio.
The optimum percentages of covered steel surface area to column surface area are 25, 28, 32
and 36 % for different slenderness ratio 6, 8, 10 and 12 for the rehabilitation of damaged (RC)
columns so that the column reaches the original. Faire agreement was found between finite
element (FEA) results and experimental (EXP) results. However, the (FEA) models can
identify the structure behavior of tested columns and can be excellent alternative of destructive
laboratory test.
 
تتناول الدراسة تاثير تکثيف الکانات اسفل واعلى الاعمدة الخرسانية المسلحة وکذلک التوزيع المنتظم على کامل طول العمود
مع تغير نسبة النحافة کما تتناول ايضا اعادة تاھيل الاعمدة الخرسانة التالفة حيث تم ازالة جميع الاجزاء الخرسانية التالفة
واستبدالھا بمونھ الجراوت. تم استخدام اربعة زوايا رأسية فى الارکان مع خوص افقية بعرض مختلف. قد بينت النتائج ان
زيادة نسبة النحافة تؤدى الى انخفاض حمل الانھيار. التوزيع المنتظم للکانات على کامل طول العمود اکثر فاعلية من
التکثثيف اعلى واسفل العمود. ايضا انھيار الاعمدة يقع مباشره بعد منطفة تکثييف الکانات مباشره مما يدل على ترکيز
الاجھاد بعد منطقة التکثييف.زيادة نسبة حديد التغطية يؤدى الى زيادة حمل الانھيار.النسبة المؤية المثلى لحديد التغطية
.١٢ - ١٠ - ٨ – ٣٦ % المقابلة لنسبة النحافة ٦ – ٣٢ – ٢٨ – ھى ٢٥