"Effects of Bond Deterioration on Hysteretic Behavior of Reinforced Concrete Joints"
by F.C. Filippou, E.P. Popov and V.V. Bertero

Abstract: The work presented in this report is concerned with developing an analytical model which describes the hysteretic behavior of reinforced concrete beam-column joints. The model takes into account the interaction of reinforcing steel and surrounding concrete through bond and the deterioration of such interaction under cyclic deformation reversals. The cyclic deterioration of bond results in relative slippage of reinforcing bars with respect to concrete thus giving rise to significant concentrated rotations at the beam-column interface. The model is presented for interior joints; its extension to exterior joints and girder inelastic regions is indicated.

In Chapter 2, following the introductory material presented in Chapter 1, the analytical description of the interaction of reinforcing steel and surrounding concrete along the anchorage length of the bars is given. The relative slip of reinforcing bars with respect to the surrounding concrete results in the formation of large cracks which run perpendicular to the axis of the girder. In order to provide the necessary number of equations describing the hysteretic moment-rotation relation of a R/C member, the equilibrium of horizontal forces and bending moments has to be satisfied at the cracked reinforced concrete sections. This necessitates the development of a new cracked R/C section model which accounts for the effects of bond deterioration in the vicinity of the crack in establishing the equilibrium of steel and concrete forces at a cracked section. This model is presented in Chapter 3 along with material models describing the stress-strain relation of reinforcing steel as well as the bond stress-slip behavior under arbitrary cyclic excitations.

Details on the numerical solution algorithm are presented in Chapter 4. The algorithm consists of three nested iteration loops, which arise when the boundary value problem of Chapter 2 is solved using transfer matrices and a numerical "shooting technique".

Comparison of analytical predictions with experimental evidence from two interior beam-column subassemblages is presented in Chapter 5. Satisfactory agreement is exhibited by the proposed model. The reported results allow insight into the physical behavior of R/C beam-column joints which can lead to improvements in the earthquake resistant design of moment resisting frames.

In Chapter 6 a series of analytical parametric studies on an interior beam-column joint are reported. Parameters varied include: bond strength along anchorage length in the joint, ratio of top to bottom reinforcement, yield strength of reinforcing bars, history of loading and effects of model scale of R/C members.

If you are interested in a copy of this report, please contact the EERC Library at eerclib@shake.berkeley.edu or send e-mail to Professor Filippou