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A new seismic retrofitting technique using compressive bracings for existing piloti-type reinforced concrete (R/C) frames has been proposed. The bracing is composed of steel pipes filled with high-strength mortar with its ends being able to resist only compressive force. This makes carrying out seismic retrofit easier, lowers the cost, and also minimizes the time spent. A model is proposed in this paper to predict the envelop curve of lateral load versus story drift angle in the strengthened story after employing the compressive bracings. Calculations are presented to predict the axial stiffness and axial strength of the bracing, as well as the bearing strength and the partial bearing stiffness of the beams jointed to the bracing. Comparison between the experimental and theoretical values shows that the theoretical values predict the experimental values reasonably accurate.

From a viewpoint of the current climate crisis, there has been much recent interest in using timber structural members in large buildings because timber can be used as renewable natural resource, and moreover, in severe earthquake prone zones, such as Japan, they are more desired on the grounds of light weight of timber members. We are developing a frame system consisting of hybrid timber members reinforced with deformed steel bar using epoxy resin adhesive. In order to practice the system, it is necessary to investigate fire resistance performance of the members. This paper reports a burning test of a beam burned for 60-minute semi-fireproof using burning marginal layer ,i.e., charring layer.