Rotation capacities of reduced beam section with bolted web (RBS-B) connections

Current seismic design provisions (ANSI/AISC 358-05) permit reduced beam section with bolted web (RBS-B) connections for only intermediate moment frames (IMF). The connections in IMF systems should provide at least 2% radian of total rotation. Prior research, however, has reported that some RBS-B connection specimens failed by connection fracture prior to reaching the 2% radian rotation. To design RBS-B connections with rotation capacities greater than 2% radian, we calibrated the moment strength equation specified in ANSI/AISC 358-05 to account for the contribution of bolted web connections. To detect and repair RBS-B connections that are unable to provide rotation capacities greater than 2% radian in existing IMF systems, we also developed an empirical equation that estimates the total rotation capacities of such RBS-B connections. Finally, we present a procedure to design RBS-B connections without connection fracture for new building systems, and to estimate the probability of RBS-B connections to develop rotation capacities larger than 2% radian for existing IMF systems.

► We calibrated the moment strength equation specified in ANSI/AISC 358-05.
► The equation can account for the contribution of bolted web connections.
► We developed an equation estimating the rotation capacity of RBS-B connections.
► We present a procedure to design RBS-B connections without connection fracture.
► We estimate the probability for a connection rotation capacity larger than 2% radian.