ABSTRACT

The design of composite steel/concrete buildings in EC8, covered in Section 7 of EN 1998-1 (2004), largely follows the general methodology adopted for steel structures (Section 6 of EN 1998-1). Accordingly, most of the approaches and procedures discussed in the previous chapter also apply to composite steel/concrete structures, with some differences related mainly to ductility requirements and capacity design considerations. This chapter highlights these differences, discusses a number of key behavioural and design aspects, and concludes with an illustrative design example.Three general ‘design concepts’ are stipulated in Section 7 of EN 1998-1, namely: 1 Concept a: low-dissipative structural behaviour – which refers to DCL in the same manner as in steel structures. In this case, a behaviour factor of 1.5-2 (recommended as 1.5) can be adopted based largely on the provisions of EC3 (EN 1993-1, 2005) and EC4 (EN 1994-1, 2004) for steel and composite components, respectively. 2 Concept b: dissipative structural behaviour with composite dissipative zones. In this case, DCM and DCH design can be adopted with additional rules to satisfy ductility and capacity design requirements as discussed in subsequent sections of this chapter. 3 Concept c: dissipative structural behaviour with steel dissipative zones. In this case, critical zones are designed as steel to Section 6 of EN 1998-1 in the seismic situation, although other ‘non-seismic’ design situations may consider composite action to EC4 (EN 1994). Therefore, specific measures are stipulated to prevent the contribution of concrete under seismic conditions.