1.1 Scope of prEN 1993-1-4 This document provides supplementary rules for the structural design of steel structures that extend and modify the application of EN 1993-1-1, EN 1993-1-3, EN 1993-1-5 and EN 1993-1-8 to austenitic, duplex (austenitic-ferritic) and ferritic stainless steels. NOTE 1 Austenitic-ferritic stainless steels are commonly known as duplex stainless steels. The term duplex stainless steel is used in this document. NOTE 2 Information on the durability of stainless steels is given in Annex A. NOTE 3 The execution of stainless steel structures is covered in EN 1090-2 and EN 1090-4. 1.2 Assumptions Unless specifically stated, EN 1990, EN 1991 (all parts), EN 1993-1-1, EN 1993-1-3, EN 1993-1-5 and EN 1993-1-8 apply. The design methods given in prEN 1993-1-4 are applicable if - the execution quality is as specified in EN 1090-2 and EN 1090-4, and - the construction materials and products used are as specified in EN 1993-1-1, EN 1993-1-3, EN 1993 1-5 and EN 1993-1-8, or in the relevant material and product specifications.