Steel Special Moment Frames: Connection Seismic Requirements

November 29, 2010
Publication: Structure Magazine p 10-12
Author(s): Ronald Hamburger Scott M. Adan

In regions of high seismic risk, severe earthquakes are rare events, affecting typical building sites at intervals of hundreds of years. Given the infrequent return period, it is economically impractical to design structures to resist such rare but severe earthquakes without damage. Instead, building codes have developed a design philosophy intended to protect life safety by avoiding earthquake-induced collapse in severe events, while permitting extensive structural and nonstructural damage.|In a steel special moment frame, it is intended that inelastic behavior be accommodated through the formation of plastic hinges at beam-column joints and column bases. Plastic hinges form through flexural yielding of beams and columns and shear yielding of panel zones. Large cyclic plastic deformations of steel shapes inevitably results in local buckling of the section. Severe local buckling, such as that shown in Figure 1, results in strength loss and, for this reason, it is desirable to avoid plastic hinging in columns. The connections must be capable of transferring moment and shear forces that can be developed in the beam to the column. As a result of material and system overstrength, these moment and shear forces can be substantially larger than the design forces specified by the building code.

Services: Structural Design