Strong-Column and Weak-Beam (SC/WB) Frame Mechanism per AISC 341-16 with ideCAD
How does ideCAD control the Column-Beam Moment Ratio according to AISC 341-16?
Moment ratio is automatically controlled and reported in accordance with AISC 341-16 §E3.
For structures with a seismic force-resisting system, the linear-inelastic behavior of the structural system under the design earthquake is considered. Although it is different for each type of steel structural system, the system is aimed at reaching the most appropriate mechanism. Accordingly, linear-inelastic deformations are only allowed in certain members. The structure is dimensioned according to this behavior model.
In moment-resisting steel frames, these members are beams. The regions defined for the plastic hinges are certain regions at the ends of the beams connected to the columns.
These parts, which are called the protected zones, absorb energy with linear-inelastic behavior, while the other parts must remain with linear-elastic behavior.
Columns must be stronger than beams to prevent brittle collapse, except for the intended mechanism.
The sway mechanism is preferred in Figure (a), while in Figure (b), the soft story mechanism is not desired. As shown in Figure (b), when the hinges are formed at the ends of the columns, this situation leads to brittle collapse.
