Seismic Code Developments for Steel and Composite Structures

Abstract

As with other codified guidance, seismic design requirements undergo a process of continuous evolution and development. This process is usually guided by improved understanding of structural behaviour based on new research findings, coupled with the need to address issues identified from the practical application of code procedures in real engineering projects. Developments in design guidance however need to balance detailed technical advancements with the desire to maintain a level of practical stability and simplicity in codified rules. As a result, design procedures inevitably incorporate various simplifications and idealisations which can in some cases have adverse implications on the expected seismic performance and hence on the rationale and reliability of the design approaches. With a view to identifying the needs for future seismic code developments, this paper focuses on assessing the underlying approaches and main procedures adopted in the seismic design of steel and composite framed structures, with emphasis on the current European seismic design code, Eurocode 8. Codified requirements in terms of force reduction factors, ductility considerations, capacity design verifications, and connection design procedures, are examined. Various requirements that differ notably from other international seismic codes, particularly those incorporated in North American provisions, are also pointed out. The paper highlights various issues related to the seismic design of steel and composite frames that can result in uneconomical or impractical solutions, and outlines several specific seismic code development needs.

Nonlinear Numerical Assessment of Steel Reduced Beam Section Connections

“…For RBS connections incorporating large sections above W44×408 (607 kg/m and tf=55 mm), similar to those investigated in this paper, a deeper cut in the range of c ≈ 0.33×bf may be considered, subject to further validation. Such an approach would also lead to a stronger panel zone which would reduce the distortional demands which are known to cause unreliable behaviour of other components of the connection, particularly in welds [1].…”

“…Steel moment frames are typically designed with rigid full-strength connections using welded or combined welded/bolted configurations. Such connections are designed with sufficient overstrength such that dissipative zones develop primarily in the beams with or without dissipative contributions from the panel zones [1]. Assessments of damage in past seismic events have attributed steel beam-column connection 2 fractures to several factors including excessive strain demands and complex triaxial stress states as well as inadequate weld qualities and procedures [2].…”