Said M. Abdalla, Ramadan Abdel Aziz Askar , Wadid W.
Ibrahim,and Rehab M. Abd El-Aziz El-Bagory
Shear interface transfer between new an old concrete has a several factors that affect on the
value of its ultimate shear resistance. To study the behavior of shear dowels connected
reinforced concrete jacket with footing, an experimental program consists of two groups of
specimens were casted and tested. Group I consists of 16 push-off specimens representing 14
different cases of placing dowels were tested under static load. Two control specimens
without dowels were tested. Group II consists of 4 push-off specimens representing 4
different cases of placing dowels with smooth interfaces and strain gauges fixed on dowels
representing the position of all dowels were tested under static load., concrete of 250 kg/cm2 ,
350 kg/cm2 were casted for footings and jacket.
Different percentages of shear dowels in different surfaces of R.C. footing were studied
and test results showed that in placing dowels in surfaces A1 (column head surfaces) the
ultimate load increased and placing dowels in surfaces A2 and A3 (horizontal surface of
footing and vertical surfaces of footing) respectively decreased the displacement. When
dowels placed in three surfaces A1, A2, A3 together, the ultimate load was increased and
displacement was decreased. The actual effect of placing dowels in surfaces A2 and A3 did
not appeared bacause of high steel reinforcement ratio of jacket which resist the increament of
loading that was noticed from test results of group II.
A proposed modification of the Japanese code (JCI) formula was presented and
compared with the experimental test results and other formulae.