An improved cable-cylinder bracing system with quarter-ring yielding devices for seismic retrofit of steel moment frames

Abstract

Cable-cylinder bracing system is a novel system composed of two steel cables and a steel pipe installed in a frame center. This system exhibits several merits mainly due to its simplicity; however, it needs to be enhanced due to limited source of energy dissipation, caused by plastic hinges formed at the ends of the beam, turning up some inappropriate cyclic behaviors in the hysteresis diagram of the system and also rupturing of the cables in large drifts. Therefore, we suggest the use of replaceable devices made of steel quarter-rings; and we propose a couple of accurate, practical, and simple formulas to calculate steel quarter-rings thickness utilized as replaceable devices. These equations correspond to the number of plastic hinges formed in the device partially under the capacity based design method. Also, the validity of these formulas along with the design requirements of device geometric parameters is fully examined and discussed by conducting FEbased parametric studies. Then, through the addition of four curved yielding devices made of low-yield-point steel to a cable-cylinder bracing system, the performance of the proposed system subjected to cyclic loading is identified.Based on the results, the new enhanced system represents a cost-effective,