STUDY ABOUT THE SEISMIC RETROFIT OF H-SHAPED STEEL BRACE JOINT USING STEEL CONCRETE COMPOSITE STRUCTURE

The brace joint fracture was observed in several severe earthquakes which occurred in the past. That's because fracture prevention of a brace joint wasn't considered by old seismic design code. The important problem to promote seismic retrofit works of a brace joint in the future is compact and fire-less seismic retrofit method which doesn't use a welding and gas-cutting. In this paper, fire-less seismic retrofit method which consists of prestressing steel bar, concrete and cover plate was proposed targeted for the existing H-shaped steel brace joint designed by old seismic design code. This seismic retrofit method aims at fracture prevention of an existence joint by an added load transmission route by reinforcement part. A series of loading test and a series of FEM analysis were carried out to consider strength improvement effect of this method and validity of the strength evaluation and each part design method. As a result, the following knowledge was obtained. The slipping strength of the existence brace and the concrete surface which were a dominant factor of the reinforcement part strength was proportional to the compression force introduced into prestressing steels bars. The reinforced joint strength exceeded the existing joint maximum strength, and the effect of the strength improvement was confirmed. The reinforcement part strength was evaluated as the slipping strength at the concrete surface, and the reinforced joint strength was evaluated as the simple sum of the existence joint maximum strength and the reinforcement part slipping strength.