Interior Joints with Variable Anchorage Lengths

Four halfscale R.C. interior beamcolumn joints were tested to assess the validity of current anchorage provisions for interior beamcolumn joints. The specimens had beam bars with anchorage lengths of 16, 20, 24, and 28 bar diameters through the joint. The tests show that anchorage length is as important as shear stress in design, and that there is no experimental evidence to support lowering the current anchorage requirements of 20 bar diameters. Current design recommendations are adequate for moderate earthquakes, but would probably lead to significant stiffness and strength losses under a major earthquake. The data on bar slippage and anchorage indicate that 24 bar diameters is very close to the ideal anchorage length for interior beamcolumn joints.