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1. Composite Structures - Introduction
BY,
SHASHANK N BABU

2. What are Composite Structures?
• General – Any members composed of more
than one material.
• Combination of Steel – Concrete.
Why?
Steel is efficient in tension while concrete is
efficient in compression.
Uses?
Buildings, Bridges

3. Major Types
• COMPOSITE BEAMS - SIMPLY SUPPORTED
• COMPOSITE BEAMS - CONTINUOUS
• COMPOSITE COLUMNS
• COMPOSITE SLABS
• COMPOSITE JOINTS

4. Codes Associated with Design
• IS 11384 – 1985 – Code of Practice for Composite
Construction in Structural Steel and Concrete.
• This standard deals with the design and construction of
Composite beams ( simply supported ) made up of
structural steel units and cast in-situ concrete.
• Eurocode 4: Design of composite steel and concrete
structures (2004)
• EN 1994-1-1 : General rules and rules for buildings
• EN 1994-1-2 : Structural fire design
• EN 1994-2 : General rules and rules for bridges

5. Advantages
• Architectural
• In addition to reductions in the dimensions of the beams
• longer spans
• thinner slabs
• Economical
• Reduction of height reduces the total height of the building
• Functionality
• Big Bonus is Fire Safety, Modern steel and composite structures can
provide fire resistance by using principles of reinforced concrete
structures in which the concrete protects the steel because of its high
mass and relatively low thermal conductivity. (IS Codes do not cover
this at all)

6. Example Comparison

7. Examples in Real Life
Millennium Tower
(Vienna - Austria)
Citibank Duisburg, Germany

8. Examples in Real Life
Grand Palladium, Mumbai Eicher Corporate Office, Gurgaon

9. Composite Beams

10. Composite Beams (Typical Types)
Partially encased
SOLID SLABS
COMPOSITE SLABS

11. Composite Beams (Typical Types)
Composite or Non-composite?
• Design the bare steelwork to carry all the loads
• Since the 1950´s it has become increasingly common to
connect the concrete slabs to the supporting beams by
mechanical devices.
• Eliminates slip at the steel-concrete interface, so that the
slab and the steel beam section act together.

12. Main Components of Composite Beam
• Types of Steel Beam
• Standard hot rolled section
• Symmetric or a-symmetric welded section
• Types of Slab
• In-situ
• Concrete Planks or
• Prefab Plates

13. Composite Action
Strains
SLIP!
Strains
NO SLIP!

14. Shear Connectors

15. Shear Connectors
• Headed Stud Connector
• Hilti Connectors
• Anchors
• Block Type Connector

16. Design Assumptions

17. Design Assumptions
STEEL
CONCRETE

18. Shear Connectors - Contd
• Strength plays a crucial part.
• Obtained experimentally (Push off or out
test)
• Output – Load vs Slip Curve.

19. Shear Connectors - Strength
• fu = 450 N/mm2
(Generally)
• Strength depends on:
• Size, height, concrete grade and ultimate stress
fu
• Shear of steel stud
• Crushing of concrete
• α = 1 for h/d>4
• α = 0.8 for h/d=3

20. Shear Connectors - Strength

21. Shear Connectors – Strength Reduction

22. Shear Connectors – Strength Reduction
• Ribs tangential to stud
nr is the number of stud
connectors in one rib at a
beam intersection, not to
exceed 2

23. Shear Connectors – Strength Reduction
• Ribs parallel to stud
nr is the number of stud
connectors in one rib at a
beam intersection, not to
exceed 2
hsc is the overall height of the stud,
but not greater than hp + 75 mm

24. Simply Supported Beam (Composite)
• Typical Design Sections for SS Case.

25. Max Moment Section I-I
• Case 1: Neutral Axis in concrete slab.
hc be 0.85 fcd = Fc
Afy = Fs

26. Max Moment Section I-I
• Case 1: Neutral Axis in concrete slab.
hc be 0.85 fcd = Fc
Afy = Fs

27. Max Moment Section I-I
• Case 1: Neutral Axis in concrete slab.
• x =
• Force Equilibrium
hc be 0.85 fcd = Fc
Afy = Fs

28. Max Moment Section I-I
• Case 2: Neutral Axis in Steel Flange.
Fs > Fc > hw tw fy

29. Max Moment Section I-I
• Case 2: Neutral Axis in Steel Flange.
Fs > Fc > hw tw fy

30. Max Moment Section I-I
• Case 3: Neutral Axis in Steel Web.
Fc < hw tw fy

31. Max Moment Section I-I
• Case 3: Neutral Axis in Steel Web.
Fc < hw tw fy

32. Max Long. Shear Section II-II
• Typical Design Sections for SS Case.

33. Max Long. Shear Section II-II
• Full Shear Connection (2 Cases)

34. Next Part
• Partial Shear Connection
• Maximum Vertical Shear Design
• Deflection