Confinement of Reinforced-Concrete Columns with NonCode Compliant Confining Reinforcement Plus Supplemental Pen-Binder

Abstract.  One  of  the  important  requirements  for  earthquake  resistant  building related  to  confinement  is  the  use  of  seismic  hooks  in  the  hoop  or  confining reinforcement  of  reinforced-concrete  column  elements. However, installation of a  confining  reinforcement  with  a  135-degree  hook  is  not  easy.  Therefore,  in practice, many construction workers apply a confining reinforcement with a  90-degree  hook  (non-code  compliant).  Based  on  research  and  records  of  recent earthquakes  in  Indonesia,  the  use  of  a  non-code  compliant  confining reinforcement  for  concrete  columns  produces  structures  with  poor  seismic performance.  This paper  presents a study  that  introduces  an additional element that is expected to improve the effectiveness of concrete columns confined with a non-code compliant  confining reinforcement. The additional element, named a pen-binder,  is   used to keep the  non-code compliant  confining reinforcement in place. The effectiveness of this element  under pure axial concentric loading  was investigatedcomprehensively.The  specimens  tested  in  this  study  were  18 concrete columns,with a cross-section of 170 mm x 170 mm and a height of 480 mm. The main test variables were the material type of the  pen-binder, the angle of  the  hook,  and  the  confining  reinforcement  configuration.The  test  results indicate  that  adding  pen -binders  can  effectively  improve  the  strength  and ductility of the column specimens confined with a non-code compliant  confining reinforcement.