A Discussion and Analysis of Ductile Detailing Requirements for Seismic Design in Moderate Seismic Regions

Abstract

This paper explores the current building code seismic design requirements for typical buildings in regions of moderate seismic hazard. In particular, the costs and benefits of various levels of ductile connection detailing requirements are reviewed for steel buildings constructed in the northeastern United States. The design of lateral force resisting systems for seismic forces has been required in the northeast states for over 20 years. However, recent building codes have introduced special ductile detailing requirements that substantially increase the cost of building connections and lateral force resisting system framing. In general, these increased costs for improved ductility allow for the proportioning of members based on assumptions of higher levels of inelasticity, and thus lower member forces, in the response of the structure. In regions of high seismicity, the benefits of such ductile detailing are clear as they improve building performance and allow for economical design of structures for more severe earthquake effects. However, in regions of moderate seismicity, the cost of these details can be very high in comparison to conventional details. Consequently, many engineers in the northeastern United States have questioned the value of design for inelastic response in non-essential facilities. The purpose of this paper is to explore these requirements and provide a qualitative and quantitative basis for comparison of seismic force resisting systems of varying levels of inelasticity for non-essential buildings in the northeastern United States.