ISO 16521:2024

International
Standard
ISO 16521
First edition
Design of concrete-filled steel
2024-09
tubular (CFST) hybrid structures
Conception de structures hybrides en tubes d'acier remplis de
béton (CFST)
Reference number
© ISO 2024
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Published in Switzerland
ii
Contents Page
Foreword .vii
Introduction .viii
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Symbols . 5
5 Materials . 7
5.1 General .7
5.2 Concrete .8
5.2.1 Cement .8
5.2.2 Aggregates .8
5.2.3 Water .8
5.2.4 Admixtures.8
5.2.5 Additions .8
5.2.6 Concrete mixture specification .8
5.3 Steel tubes . .8
5.4 Steel reinforcement .9
5.4.1 Deformed reinforcement .9
5.4.2 Plain reinforcement .9
5.5 Other materials .9
5.5.1 Welding consumables .9
5.5.2 Fasteners .9
5.5.3 Protective paint systems .9
5.6 Storage of materials .9
6 Design and construction procedure . 9
7 General guides .11
7.1 Limitations .11
7.1.1 CFST members .11
7.1.2 Trussed concrete-filled steel tubular (CFST) hybrid structures . 12
7.1.3 Concrete-encased concrete-filled steel tubular (CFST) hybrid structures . 12
7.2 Limit states . 13
7.3 Ultimate limit state design format . .14
7.3.1 General .14
7.3.2 Factored load effects .14
7.3.3 Design resistances .14
7.4 Serviceability limit state design format . 15
8 Specific guides .15
8.1 Design working life . 15
8.2 Selections of materials, structural plans and detailing . 15
8.3 Seismic design requirements . 15
8.4 Selections of constructional methods and techniques . 15
9 Actions (loads). 16
9.1 General .16
9.2 Dead loads .16
9.3 Live loads .16
9.4 Snow loads .16
9.5 Wind forces .16
9.6 Earthquake forces .16
9.7 Thermal forces .17
9.8 Load partial factors and load combinations .17
10 Analysis . . 17

iii
10.1 General .17
10.1.1 Structural analysis purpose .17
10.1.2 Structural analysis methods.17
10.1.3 Structural analysis requirements .17
10.1.4 Loading cases .18
10.1.5 Construction stage analysis .18
10.2 Stress-strain relationships for materials .18
10.2.1 General .18
10.2.2 Concrete .19
10.2.3 Steel . 26
10.3 Indices for the strength and stiffness of CFST hybrid structures . 28
10.3.1 CFST cross-section . 28
10.3.2 CFST hybrid structures . 30
11 Ultimate limit states of trussed concrete-filled steel tubular (CFST) hybrid structures .31
11.1 General .31
11.2 Resistances to compression and bending .31
11.2.1 Axial compression .
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