Hits: 4684
The author works for a nuclear licensee, and was responsible for drafting the design document that specifies the requirements for seismic design (MED, 2009 updated 2014). Within this document is the statement that design to achieve ductility is just as important as strength design. This paper examines the background about why this statement has been made; and how ductile detailing can be achieved in practice.
The paper starts with a discussion about what is meant by ductility in the abstract then concentrate on what is achieved by ductile design. A simple example based upon comparison between a conventional braced frame and an eccentrically braced frame is used to illustrate this. This example is used to show how ductile details can protect a system and be used to demonstrate the capability of a structure to resist earthquakes beyond design basis.
The paper continues by describing some of the practical ways in which ductility can be incorporated into real structures taking account of the principal that stronger is not always better when considering seismic design. Reference is made to ACI 2013 for concrete structures; and to ANSI/AISC 341, 2010, for steel structures.
The paper concludes with real examples where ductile detailing has been used for nuclear projects. Examples will cover notched connections and special concentric bracing for storage racking; and use of special concentric bracing for strengthening an existing structure.