Braced frame structures designed according to the 1990 edition of the National Building Code of Canada and the CSA standard for steel structures (CAN/CSA-S16.1-M89) are analyzed under a number of different earthquake motions. The nonlinear response is studied in the light of the design philosophy, and the validity of a number of design assumptions is examined. The study is limited to a group of eight-storey frames, located either in Victoria, British Columbia, or Montreal, Quebec, all with the same bracing configuration. A 20-storey frame in Montreal is also considered. The results suggest a number of areas in which improved design provisions could be made. Key words: analysis, design, structural engineering, steel, earthquakes, braced frames.