STR-966: SEISMIC RETROFIT OF EXISTING LOW-RISE STEEL BUILDINGS IN EASTERN CANADA USING ROCKING BRACED FRAME SYSTEM

A promising retrofit strategy consists of allowing deficient braced frames to rock at their bases to reduce the force demands on the structure and the foundation. For low-rise buildings, modifications to the structure may be limited to the braced frames, which then represent a very effective solution when compared to other approaches where alterations are needed along the entire lateral load path. In the article, the rocking braced frame solution is investigated for the seismic retrofit of 3-storey typical office buildings designed in accordance with codes prevailing in the early 1980s. The frames are located in Montreal, QC, and firm ground and soft soil conditions are examined for both locations. Rocking braced frames with friction energy dissipation mechanism are investigated. The response of the retrofitted structures is examined through nonlinear time history analyses using site representative ground motions and the results are compared to predictions from simplified models assuming first mode response