In regions of high seismicity, both domestically and internationally, the use of steel Special Moment Frame (SMF) with Reduced Beam Section (RBS) connections is commonly employed to provide an economical and high performance structural system. For larger and taller buildings, built-up steel box columns are further introduced in SMF with RBS connections for effective bi-axial and economical control of seismic strength and drift demands. However, due to a lack of qualification testing in the U.S., AISC 358 limits the maximum box column size dimension to 24 inches in width and depth, and RBS beam to 300 lbs./ft. While interest in additional testing and pre-qualification per AISC 341 and AISC 358 requirements in the U.S. has been limited, there has been significant focus on testing and research of these connections over the past five years in Japan and Taiwan. Research using finite element modelling of weldments, heat affected zones and residual stresses has been conducted to better understand brittle fracture connection failure modes identified through full-scale specimen testing. Nonetheless, recent qualification testing and research in the U.S. conducted at UC San Diego during the design and construction documentation of the new San Diego Central Courthouse project now under construction, has provided additional qualification test results on three full-scale test specimens of SMF RBS connections with 36 inch deep built-up box column and W36x302 RBS beam. This paper summarizes investigations undertaken by the authors as part of the SEAONC 2015 Special Project Initiative (SEAONC 2015 SPI) award to provide analytical verification modeling of test results obtained from the courthouse testing program. This paper describes the development of the finite element verification model using Abaqus/CAE (2016) simulation tools including introduction of initial imperfections (global and local top and bottom flange) using buckling modes, and other parameters defining material nonlinear properties for cyclic isotropic and kinematic hardening components of beam, column and continuity plate elements. Recommendations for additional testing and extending AISC 358 RBS prequalification limits based on additional simulation models with varying column sizes are considered demonstrating correlations with verification models over a range of story drift ratios. Detailed investigation of continuity plate stresses and impact on connection behavior with and without continuity plates is described.
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