Composite Steel and Concrete - Construction Design of composite columns

A general presentation of composite columns was given in § 1.2.3 of the article [C 2560] , showing that there is a wide variety of possible cross-sections, but distinguishing between two main families:

• posts partially or totally encased in concrete ;

• hollow sections filled with concrete.

Like steel posts, composite posts offer the following advantages:

• high load-bearing capacity for relatively small cross-sections;

• ease of assembly with other elements, beams in particular, due to the presence of the steel part of the columns (cf. § 1.2.4 of article [C 2560] );

• the ability to deform in the plastic range and exhibit ductile behavior.

Thanks to the collaboration of concrete and steel, the mixed column solution can significantly reduce the cross-section of the steel section, compared with the steel-only column solution, for a given load-bearing capacity.

The protection provided by concrete, in the case of partially encapsulated sections (and even more so for fully encapsulated sections), can give these elements a high level of fire resistance (see clause 4.3.5. and Annex G of EN 1994-1-2). Even in the case of hollow sections filled with unprotected concrete, the reinforced concrete inner section more than compensates for the loss of strength of the rapidly heating steel, and can achieve appreciable fire durations, provided that appropriate dimensioning is used (see Annex PCRB to NF EN 1994-1-2/NA and ,