Date of Award

7-1997

Degree Type

Thesis

Degree Name

Doctor of Philosophy (PhD)

Department

Civil Engineering

Supervisor

A. Ghobarah

Co-Supervisor

T.S.Aziz

Abstract

Many multi-story reinforced concrete frame structures were designed before the availability of current seismic design codes. The lateral load resistance of these structures may not be adequate even for a moderate earthquake due to the non-ductile reinforcement details of this type of structures. Recent post-earthquake investigations indicated that extensive damage occurs as a result of excessive shear deformation of the beam-column joints in the non-ductile frames, thus leading to full collapse of structures. The objectives of this study are to investigate the seismic behaviour of existing reinforced concrete frames under simulated seismic loading; as well as develop a rehabilitation technique for strengthening non-ductile frames. The first major part of the study is an experimental program conducted to: (i) investigate the inelastic behaviour of the non-ductile beam-column connections under cyclic loading; (ii) compare the response of the non-ductile beam-column connections with the response of beam-column connections designed according to the current concrete design code; and (iii) propose a practical method of rehabilitating existing connections and investigate their cyclic behaviour. The tested connections represent one-third scale model of existing connections. Six beam-column connections were tested under cyclic loading. The variables in the test specimens included the amount of joint and column transverse reinforcement and jacketing of the column only or both the column and the beam. Based on the test results, a design procedure is proposed for the rehabilitation of beam-column connections using corrugated steel jackets. The second major part of the study is to develop a suitable analytical procedure to simulate the behaviour of existing reinforced concrete joints so as to predict the proper behaviour of the non-ductile frames and develop a strategy for rehabilitation of such frames. Two joint elements are developed to represent the joint shear deformation and the beam reinforcing bar bond slip. The two elements are introduced into a non-linear dynamic analysis program which is used to simulate existing and rehabilitated frames. From the experimental and analytical research findings, recommendations for the design and detailing of the corrugated steel jacketing system for existing reinforced concrete frames are developed. In addition, a rehabilitation strategy is proposed to improve the performance of existing structures. The effects of the rehabilitation system on the confinement of beam-column connections, the provision of adequate development length for the positive bottom beam bars and the provision of full joint shear capacity are assessed and quantified. Test results indicated that corrugated steel jacketing system was found to be efficient in the rehabilitation of existing structures which do not meet the current seismic code requirements. A method is proposed for the design of the corrugated steel jacket to enhance the shear strength and ductility of the beam-column joint.

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