FUNDAMENTAL PERIOD OF REINFORCED CONCRETE MOMENT-RESISTING FRAME STRUCTURES by Vitelmo V. Bertero, Fouad M. Bendimerad and Haresh C. Shah

This repcrt investigates the rationale behind the approximate formula for computing the period of reinforced concrete frame structures recommended by the Structural Engineers Association of California (SEAOC) and adopted by the International Conference of Building Offcials (100). Pertinent studies and reports constituting the basis for that formula are critically reviewed. The discrepancies of the data base and procedure fcr compiling building periods from the data base are discussed. Results from various experimental studies are repcrted to illustrate the variation of building period with the increase of building vibrational response. The effects of building period on the response of structures under two orthogonal ground motion inputs are illustrated. The influence Of structure characteristics and soil conditions are also discussed. The study introduces a rnethodology for inferring, in a consistent manner, building periods from actual strong motion instrument records. Based on this methodology, periods of 15 reinforced concrete frame buildings are compiled The new data is correlated with approximate (ernpirical) period formulas prescribed in various code regulations and recommendations.