Design of Composite RCS Special Moment Frames

This document was developed to assist practicing engineers in the design of Composite Special Moment Frame (C-SMF) systems utilizing reinforced concrete columns and steel beams (known as Composite RCS frames). These systems utilize the intrinsic advantages of each material which are optimized in resisting the applied loads.

Seismic design requirements for C-SMF systems are included in ASCE 7 (2010) and AISC 341 (2010). These system-level requirements are supported by research and other documents on the design and detailing of beam-column connections between the steel beams and concrete (or encased composite) columns. In 1994, the ASCE Task Committee on Design Criteria for Composite Structures in Steel and Concrete issued guidelines for the Design of Joints between Steel Beams and Reinforced Concrete Columns in 1994 (ASCE 1994). Based on research at the time, it was recommended to limit the use of Composite RCS systems to regions of low seismicity. Since then, further research has been performed which has demonstrated that Composite RCS systems can be designed to have reliable ductile performance, making them an attractive design alternative for high seismic areas. Based on this research, a draft Pre-Standard for the Design of Moment Connections between Steel Beams and Concrete Columns (ASCE 2015 draft) has been prepared as an update to the 1994 ASCE connection design guidelines. This draft is utilized for the design studies presented herein.