ANALYSIS OF TENSILE CAPACITY OF REINFORCED CONCRETE COLUMNS AND ITS DUCTILITY PERFORMANCE TOWARDS SEISMIC BEHAVIOR

In the limit state of collapse design approach for reinforced concrete (RC) columns, the conceptual design criteria is formulated based on the balanced limiting strains i.e. simultaneous crushing of concrete and yielding of steel occurs in extreme concrete fiber and steel, which is designated as 0.0035 and 0.002+(fy+1.15/Es) respectively . But the tensile strain in extreme layer of steel is permitted to reach any value more than the prescribed value under crucial scenarios of high seismic influence. Therefore the premature yielding of extreme steel layer over the crushing of concrete, i.e. the under reinforced design of RC columns is not authentified by the existing design approach. Adding to this whenever RC columns are subjected to seismic forces, reversal of stresses occurs i.e. the predominant compressive forces in column changes its behavior to tensile forces. Hence it is mandatory to determine the tensile capacity of column and its corresponding ductile behavior and the strain energy stored in it. The tensile capacity of the column and the range of tension failure under combined compressive axial load and bending is thus identified by determining the Balanced Axial load factor λ ,in which the computation involves the limiting strain states in concrete and steel. A numerical study is made over the Balanced Axial Load factor λ by, varying parameters such as Column section, Percentage of reinforcement excessive limiting strains in steel and with the orientation of the column. Hence a more accepted under reinforced design approach i.e. ductile design is proposed for columns subjected to seismic forces.