Date of Award

7-1994

Degree Type

Thesis

Degree Name

Doctor of Philosophy (PhD)

Department

Civil Engineering and Engineering Mechanics

Supervisor

A. Ghobarah

Abstract

Based on a limited number of experiments, the current practice is to use fully welded link-column connections for links in eccentrically braced frames (EBFs). Since the use of field welded connections has its limitations, the use of bolted connections may be an attractive alternative. The extended end plate bolted connection (EEP) was selected for use in link-column join applications in eccentrically braced frames.

The link-column connection is required to behave in a ductile manner. This would enable the shear link to develop its full plastic capacity and thus the EBF would be able to dissipate the earthquake input energy. In addition, the link-column connection should not result in any degradation of the EBF lateral stiffness. To test the ability of EEP connections to satisfy both those requirements, a two phase research program was performed.

The first phase of study is experimental in nature and involves the testing of end plate connections under severe cyclic loading. The cyclic load is used to model the severe load reversals associated with a major seismic event. The effect of bolt size, end plate thickness and the use of end plate stiffeners on the performance of the joint was evaluated. It was found that properly designed EEP connections showed ductile performance. Links with extended end plate connections developed ultimate forces and reached deformation angles comparable to those with fully welded connections. Guidelines for designing EEP connections for link-column joints are proposed.

Because of the severe inelastic behaviour of the shear links, their proper modelling is important for the accurate analysis of an EBF. In the second phase of this research, a simple yet effective link element model is developed. This model was included in the computer code DRAIN-2DX, of Prakash and Powell (1992). Comparisons with previous and current results confirm the accuracy of this new link model.

An extensive dynamic analysis of EBFs with semi-rigid joints was conducted to shed some light on the effect of EEP connections on the performance of EBFs. A six-story, three-bay EBF and a twenty-story, single-bay EBF were selected. These EBFs were subjected to several strong ground motion records. The developed shear link model was used in the computer modelling of these frames. Several designs of these frames involving different degrees of connection flexibility are analyzed. The various design responses are compared to each other to determine the effect of connection flexibility on the response of EBFs. It was found that properly designed bolted EEP connections can be used as alternative to welded link-column joints in eccentrically braced frames.

Files over 3MB may be slow to open. For best results, right-click and select "save as..."

Share

COinS