COMPARISON OF CONFINEMENT REINFORCEMENT IN REINFORCED CONCRETE STRUCTURES

Abstract

The major cause of damage of R.C. structures during Kashmir-Hazara earthquake observed was due to improper and insufficient confinement reinforcement in columns. This experimental investigation represents the comparison of improper and insufficient confinement reinforcement and confinement reinforcement specified by the building code. Two reinforced concrete (RC) columns were constructed, each having cross sectional dimension of 230 mm x 230 mm and a height of 1834 mm. A foundation of 800mm x 800mm x 460mm was casted monolithically with each column. Concrete strength and longitudinal reinforcement are kept same for each column. However in one column hoop reinforcement with 90° bend is used as confinement reinforcement while in the other column angle of bend is 135° is used as per specification of seismic code. Strain gauges are fixed on the longitudinal and lateral reinforcement within the zone of plastic hinge for the column. Lateral cyclic load is applied for evaluation of response of column under constant axial compression. The study revealed that seismic hook increased the moment resistance of column by 31% and load carrying capacity by 51%. It is concluded that major loss of structural performance is mainly due to improper onfinement reinforcement used in engineered and non engineered structures in Northern areas of Pakistan.