Structural Systems For
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STRUCTURAL SYSTEMS FOR
By, Group – 5 Phase - 1 Chirag Patel Vijay Garchar Bhavin Patel
2
What Will You Gain From This Presentation?
General knowledge of Composite Construction.
Knowledge about the details of composite steelconcrete construction, the components that are used, and how they are installed.
An understanding of the impacts that composite steel-concrete construction may have on project schedule, cost, sequence and overall management.
3
Benefits of Composite Construction In Tall Structures
Most
effective utilization of material Concrete Compression Steel Tension Provide more working space Better Seismic Resistance Faster construction Cost effectiveness 4
Some Unique Aspects of Composite Construction
• Steel Sections are fabricated off-site (above left). • On-site erection is a rapid process (above right). This gives use of some scheduling advantages.
5
6
FOR
7
Composite Gravity Systems Composite Floor Systems
Composite Columns
• Metal Deck • Beams • Trusses • Shear Connectors • Stub girders
Linked via shear connectors to a concrete floor 8
Composite Floor Systems
9
Composite Gravity System
10
Composite Floor Systems
Metal Deck
Composite Floor sheets 11
Metal Deck
Composite Floor Systems
• By fully mechanized, high-speed cold rolling process • Depth 1 1/2, 2 and 3 in. (38,51 and 76 mm) • Thickness up to 19 mm • Weight from 24 N/m2 to 431 N/m2
Corrugations
Embossments Ridges or Lugs 12
Metal Deck
Composite Floor Systems
Installation of Decking
13
Metal Deck
Composite Floor Systems
• Puddle welds (above right) are commonly used to attach the decking to the structural steel below • Daily output for a four person decking crew ranges from 2700 S.F. to 3860 S.F. per day depending on the depth and gauge of the decking
14
Metal Deck
Composite Floor Systems
•
As an alternative to welding, powder actuated tools may be used to attach metal decking to structural steel
•
Powder actuated tools use the expanding gases from a powder load, or booster, to drive a fastener
•
A nail-like fastener is driven through the metal deck into the steel beam
•
The powder actuated tool, powder load, and fastener must be matched to the thickness of the structural steel beam flanges
15
Metal Deck
Composite Floor Systems
Mechanical Interlock
Frictional Interlock
End anchorage 16
Metal Deck
Composite Floor Systems
Shear Connectors
Nominal Reinforcement (Welded Wire Fabric) 4 # @ 40 cm c/c
17
Metal Deck
Composite Floor Systems
Connecting the concrete to the steel beams can have several advantages: • It is typical to have a reduced structural steel frame cost
• Shallower beams may be used which might reduce building height
• Weight of the structural steel frame may be decreased which may reduce foundation costs
• Increased span lengths are possible
• Reduced live load deflections
• Stiffer floors
18
Metal Deck
Composite Floor Systems
SDI Specifications • Minimum yield point of metal deck is 227.5 MPa • Minimum compressive strength of concrete shall be 20.68 MPa. • Admixture containing chloride salts is prohibited. • Bending stress is limited to 0.6 times the yield strength of steel. • Deflection based on the weight of concrete is limited to the L/180 or 19 mm. • Minimum bearing of 33 mm is specified for proper deck seating on supports and at sides. • Max. average spacing of 12 in. (305 mm) for puddle welds.
19
Metal Deck
Composite Floor Systems
Testing
20
Metal Deck
Composite Floor Systems
Analysis
21
Composite Floor Systems
Beams
22
Beams
Composite Floor Systems
23
Beams
Composite Floor Systems
Continuous Composite Beam
24
Beams
Composite Floor Systems
Strain - Stress Diagram
25
Composite Floor Systems
Beams Cambering
26
Beams
Composite Floor Systems
Cambering is the process of creating an intentional slight curvature in a beam.
27
Beams
Composite Floor Systems
• Camber in a beam can be designed to compensate for either:
A certain percentage of the dead load deflection
The full dead load deflection
The full dead load deflection as well as a percentage of the live load deflection
• Camber is usually designed to compensate for deflections caused by pre-composite dead loads
28
Beams
Composite Floor Systems
Advantage of Cambering
•
Supporting beams will deflect under the load of concrete being placed.
•
This deflection can be exaggerated in a composite floor system where the full strength of the system is not achieved until the concrete has cured
•
Cambered beams (top diagram above) should deflect to a straight line (bottom diagram above), if load and deflection are predicted accurately and camber equals deflection 29
•
This allows the floor slab to be flat while maintaining a consistent thickness
Beams
Composite Floor Systems
•
If beams are not cambered (top diagram above) the deflection under the load of the wet (plastic) concrete will result in a ponding effect in the concrete (bottom diagram above) .
•
To create a flat floor in this situation the concrete will need to be thicker at the center of the bay where the deflection is the greatest .
•
The volume of concrete used will typically be 10-15% more than if the floor is a constant thickness. (ASCE 2002)30
Beams
Composite Floor Systems
•
The use of cambered beams will, to a certain degree, be limited by other aspects of the design for a structure
•
Due to the complexity in detailing, fabrication, and fit-up associated with moment connections (above left), camber should not be used in moment connected beams
•
Beams with simple framing connections (above right) may be cambered because the end rotational resistance of a simple connection is small31in comparison to that of a moment connection
Beams
Composite Floor Systems
Disadvantage of Cambering
•
Care needs to be taken in the specification and fabrication of camber to ensure that a beam, once in place and under load, will perform within tolerances
•
Levelness and consistent floor thickness can be a problem
•
The diagrams above show two possible results of cambered beams not deflecting as predicted under the load of the wet (plastic) concrete 1. Stud heads are exposed
(ASCE 2002)
32
2. Top of slab elevation out of tolerance
Beams
Composite Floor Systems
Alternative methods for achieving a level floor slab without using cambered beams include: •
Pouring a slab of varying thickness over deflecting beams
•
Using over-sized beams to minimize deflection
•
Shore the beams before placing the concrete
Shoring Concrete At 75% Strength
33
Composite Floor Systems
Beams
When to Camber
•
Girder Beams
•
Filler Beams
•
Members with uniform cross section
•
Composite Floor Beams
34
Composite Floor Systems
Beams
When not Camber
•
Moment Connected Beams
•
Spandrel Beams (above right)
•
Cantilevered Beams (above left)
•
Braced Beams (above right) 35
Composite Floor Systems
Beams
•
Beam with moment connections (above right)
•
Beam under 20 feet length (above right)
•
Beams with loading
•
Beams with connections
non-symmetrical
end
plate 36
Beams
Composite Floor Systems
Heat Cambering •
Beams may be cambered by applying heat to small wedge-shaped areas at specific increments along the beam (Ricker 1989)
•
The beam is place upside down on supports so the “bottom” flange can be heated
•
The heated flange expands under the heat and contracts as it cools
•
Camber is induced in the opposite side of the beam as the heated flange cools
37
Composite Floor Systems
Beams
Cold Cambering •
Cold cambering methods are more widely used and generally more economical than heat cambering
•
The beam is mounted in a frame and force from a ram(s) is used to bend the beam to create camber
38
Beams
Composite Floor Systems
Forms of Incorporating Services within Structural Depth
Beam with Openings
Castellated Beam
Truss 39
Beams
Composite Floor Systems
Beams with web openings
40
Beams
Composite Floor Systems
Beams with web openings • In order to accommodate large service ducts within the structural depth, thus reducing the ceiling to floor zone, large holes are sometimes required through the webs of beams. If these are not too large (say, not greater than 0.6D nor longer than 1.5D), holes without horizontal stiffening may be made provided of course that the remaining web has adequate shear resistance. If larger holes are necessary, stiffeners in the form of horizontal plates welded above and below the hole should be provided. • An alternative to providing customised holes at required locations in a rolled beam is to use a castellated or cellular beam. 41
Beams
Composite Floor Systems
Castellated Beams •
Castellated beams can be used effectively for lightly serviced buildings or for aesthetic reasons, where the structure is exposed. Composite action does not significantly increase the resistance of the beams but increases their stiffness.
•
Castellated beams have limited shear resistance and are best used as long span secondary beams or where loads are relatively low.
42
Beams
Composite Floor Systems
43
Composite Floor Systems
Trusses •
Composite trusses were developed in North America and are popular for spans of 10 to 20m.
44
Composite Floor Systems
Trusses
Typical Truss 45
Composite Floor Systems
Trusses
46
Trusses
Composite Floor Systems
Advantages •
They do not require any special fabrication equipment.
•
They offer plenty of space to accommodate services.
•
They can be designed with a Vierendeel Panels at mid span (where shears are low even under non-symmetric loading); this panel can accommodate an air conditioning duct.
Disadvantages •
The principal disadvantage, other than the increased fabrication cost, is that they are difficult to protect from fire. 47
Trusses
Composite Floor Systems
48
Beams
Composite Floor Systems
Haunched Beams •
Beams are about 20% heavier compared to a rigidly jointed frame but columns are typically 40% lighter, and connection costs are significantly reduced. This "heavy beam/light column" structure makes economic sense when the weight of the beams is similar to that of the columns.
•
Haunched beams are generally designed by forming a rigid moment connection between the beams and columns. The extra service zone created beneath the beam between the haunches, offers flexibility in service layout.
•
At edge columns, it would not be normal practice to develop additional continuity through the slab reinforcement; this, however, is an option at internal columns. This form of construction can be used for sway frames, i.e. where vertical bracing or concrete shear walls or cores are not provided.
49
Beams
Composite Floor Systems
50
Beams
Composite Floor Systems
51
Beams
Composite Floor Systems
52
Beams
Composite Floor Systems
53
Composite Floor Systems
Shear Connectors • Shear connectors are essential for steel concrete composite construction as they integrate the compression capacity of supported concrete slab with supporting steel beams / girders to improve the load carrying capacity as well as overall rigidity.
• Shear Connectors are designed to, Transmit longitudinal shear along the interface. Prevent separation of steel beam and concrete slab at the interface. 54
Shear Connectors
Composite Floor Systems
55
Shear Connectors
Composite Floor Systems
Types of Shear Connectors •
Rigid Shear Connectors
•
Flexible Shear Connectors
•
Anchorage Shear Connectors
Shear connectors to fulfils number of requirements, as follows: • • •
They must transfer direct shear at their base. They must create a tensile link into the concrete. They must be economic to manufacture and fix. 56
Shear Connectors
Composite Floor Systems
Deformation of Flexible Connectors 57
Shear Connectors
•
•
Composite Floor Systems
The electrical arc process is commonly used for stud welding
An arc is drawn between the stud and the base metal
The stud is plunged into the molten steel which is contained by the ceramic ferrule
The metal solidifies and the weld is complete
The ferrules are removed before the concrete is poured
58
Shear Connectors
Composite Floor Systems
•
Depending on the welding process used, the tip of the shear connector may be placed in a ceramic ferrule (arc shield) during welding to retain the weld.
•
Shear connectors create a strong bond between the steel beam and the concrete floor slab which is poured on top of the metal decking.
•
This bond allows the concrete slab to work with the steel beams to reduce live load deflection. 59
Shear Connectors
Composite Floor Systems
As Per IS 11384 : 1985
60
Shear Connectors
Composite Floor Systems
Alternative Forms of Connection Shot fire Connector
Friction grip Connector
61
Composite Floor Systems
Stub Girders •
The system was devised in North America in the 1970s and is described in detail by Chien and Ritchie (1984, 1992).
62
Composite Floor Systems
Stub Girders F lo o r
S t u b w e ld e d t o b o tto m c h o rd S e r v ic e z o n e
C o m p o s it e se c o n d a ry b e a m
F lo o r C o n t in u o u s r ib s
M a in d u c t s
D is t r ib u t io n d u c t s
63
Composite Floor Systems
Stub Girders •
Architectural demand for square column grids with spacing of 10 to 12 m led to the development of stub girder construction.
•
The stub girder comprises a bottom chord, which acts in tension, and a series of short beam sections (or stubs) which connect the bottom chord to the concrete slab. Secondary beams span across the bottom chord and can be designed as continuous members. Voids are created adjacent to the stubs for services.
64
Stub Girders
•
Composite Floor Systems
The major disadvantage of the conventional stub girder is that it requires temporary propping until the concrete has gained adequate strength for composite action. However, it is possible to introduce a light steel top chord, such as a T-section, which acts in compression, to develop the required bending resistance of the girder during execution.
65
Composite Floor Systems
Stub Girders
Stub Girder
66
Stub Girders
Composite Floor Systems
Long Span Stub Girder Grillage Animation
67
Construction Animation
Nail-like fastener is driven Shear throughConnectors the metal deck into the steel beam
Composite System
Installation of Concrete
68
Construction Animation
Nail-like fastener is driven Shear throughConnectors the metal deck into the steel beam
Composite System
Installation of Concrete
69
Construction Animation
Nail-like fastener is driven Shear throughConnectors the metal deck into the steel beam
Composite System
Installation of Concrete
70
Construction Animation
Nail-like fastener is driven Shear throughConnectors the metal deck into the steel beam
Composite System
Installation of Concrete
71
Composite Gravity Systems Composite Floor Systems
Composite Columns
• Metal Deck • Prismatic or Haunched Beams • Shear Connectors • Trusses • Stub girders
72
Composite Columns
Composite Columns •
•
•
A steel composite column is a compression member, comprising either a concrete encased hot – rolled steel section or a concrete filled tubular section of hot- rolled steel and is generally used as a load – bearing member in a composite framed structure. Both steel section and concrete resist external loading by interacting together through chemical bond and friction, or by the use of mechanical shear connectors in particular situation. Additional reinforcement in concrete encasement prevents excessive spalling of concrete both under normal load and fire condition. 73
Composite Columns
Composite Columns
Typical c/s of partially concrete encased sections
74
Columns
Composite Columns
Typical c/s of Fully concrete encased sections
75
Columns
Composite Columns
Stress distribution of the plastic resistance to compression of an encased I section
Pp =
Aa. fy α c. Ac.( 0.80*( fck )cu ) As. fsk + γa + γc γs 76
Columns
Composite Columns
Concrete filled steel column
Cheung Kong Center - Hong Kong
77
Columns
Composite Columns
78
Columns
Composite Columns
79
Connections
Composite Connection
Internal & external semi-rigid beam/column connection
80
Connections
Composite Connection
Composite beam to concrete surface connection
81
82
FOR
Earthquake
83
By, Group – 5 Phase - 1 Chirag Patel Vijay Garchar Bhavin Patel
2
What Will You Gain From This Presentation?
General knowledge of Composite Construction.
Knowledge about the details of composite steelconcrete construction, the components that are used, and how they are installed.
An understanding of the impacts that composite steel-concrete construction may have on project schedule, cost, sequence and overall management.
3
Benefits of Composite Construction In Tall Structures
Most
effective utilization of material Concrete Compression Steel Tension Provide more working space Better Seismic Resistance Faster construction Cost effectiveness 4
Some Unique Aspects of Composite Construction
• Steel Sections are fabricated off-site (above left). • On-site erection is a rapid process (above right). This gives use of some scheduling advantages.
5
6
FOR
7
Composite Gravity Systems Composite Floor Systems
Composite Columns
• Metal Deck • Beams • Trusses • Shear Connectors • Stub girders
Linked via shear connectors to a concrete floor 8
Composite Floor Systems
9
Composite Gravity System
10
Composite Floor Systems
Metal Deck
Composite Floor sheets 11
Metal Deck
Composite Floor Systems
• By fully mechanized, high-speed cold rolling process • Depth 1 1/2, 2 and 3 in. (38,51 and 76 mm) • Thickness up to 19 mm • Weight from 24 N/m2 to 431 N/m2
Corrugations
Embossments Ridges or Lugs 12
Metal Deck
Composite Floor Systems
Installation of Decking
13
Metal Deck
Composite Floor Systems
• Puddle welds (above right) are commonly used to attach the decking to the structural steel below • Daily output for a four person decking crew ranges from 2700 S.F. to 3860 S.F. per day depending on the depth and gauge of the decking
14
Metal Deck
Composite Floor Systems
•
As an alternative to welding, powder actuated tools may be used to attach metal decking to structural steel
•
Powder actuated tools use the expanding gases from a powder load, or booster, to drive a fastener
•
A nail-like fastener is driven through the metal deck into the steel beam
•
The powder actuated tool, powder load, and fastener must be matched to the thickness of the structural steel beam flanges
15
Metal Deck
Composite Floor Systems
Mechanical Interlock
Frictional Interlock
End anchorage 16
Metal Deck
Composite Floor Systems
Shear Connectors
Nominal Reinforcement (Welded Wire Fabric) 4 # @ 40 cm c/c
17
Metal Deck
Composite Floor Systems
Connecting the concrete to the steel beams can have several advantages: • It is typical to have a reduced structural steel frame cost
• Shallower beams may be used which might reduce building height
• Weight of the structural steel frame may be decreased which may reduce foundation costs
• Increased span lengths are possible
• Reduced live load deflections
• Stiffer floors
18
Metal Deck
Composite Floor Systems
SDI Specifications • Minimum yield point of metal deck is 227.5 MPa • Minimum compressive strength of concrete shall be 20.68 MPa. • Admixture containing chloride salts is prohibited. • Bending stress is limited to 0.6 times the yield strength of steel. • Deflection based on the weight of concrete is limited to the L/180 or 19 mm. • Minimum bearing of 33 mm is specified for proper deck seating on supports and at sides. • Max. average spacing of 12 in. (305 mm) for puddle welds.
19
Metal Deck
Composite Floor Systems
Testing
20
Metal Deck
Composite Floor Systems
Analysis
21
Composite Floor Systems
Beams
22
Beams
Composite Floor Systems
23
Beams
Composite Floor Systems
Continuous Composite Beam
24
Beams
Composite Floor Systems
Strain - Stress Diagram
25
Composite Floor Systems
Beams Cambering
26
Beams
Composite Floor Systems
Cambering is the process of creating an intentional slight curvature in a beam.
27
Beams
Composite Floor Systems
• Camber in a beam can be designed to compensate for either:
A certain percentage of the dead load deflection
The full dead load deflection
The full dead load deflection as well as a percentage of the live load deflection
• Camber is usually designed to compensate for deflections caused by pre-composite dead loads
28
Beams
Composite Floor Systems
Advantage of Cambering
•
Supporting beams will deflect under the load of concrete being placed.
•
This deflection can be exaggerated in a composite floor system where the full strength of the system is not achieved until the concrete has cured
•
Cambered beams (top diagram above) should deflect to a straight line (bottom diagram above), if load and deflection are predicted accurately and camber equals deflection 29
•
This allows the floor slab to be flat while maintaining a consistent thickness
Beams
Composite Floor Systems
•
If beams are not cambered (top diagram above) the deflection under the load of the wet (plastic) concrete will result in a ponding effect in the concrete (bottom diagram above) .
•
To create a flat floor in this situation the concrete will need to be thicker at the center of the bay where the deflection is the greatest .
•
The volume of concrete used will typically be 10-15% more than if the floor is a constant thickness. (ASCE 2002)30
Beams
Composite Floor Systems
•
The use of cambered beams will, to a certain degree, be limited by other aspects of the design for a structure
•
Due to the complexity in detailing, fabrication, and fit-up associated with moment connections (above left), camber should not be used in moment connected beams
•
Beams with simple framing connections (above right) may be cambered because the end rotational resistance of a simple connection is small31in comparison to that of a moment connection
Beams
Composite Floor Systems
Disadvantage of Cambering
•
Care needs to be taken in the specification and fabrication of camber to ensure that a beam, once in place and under load, will perform within tolerances
•
Levelness and consistent floor thickness can be a problem
•
The diagrams above show two possible results of cambered beams not deflecting as predicted under the load of the wet (plastic) concrete 1. Stud heads are exposed
(ASCE 2002)
32
2. Top of slab elevation out of tolerance
Beams
Composite Floor Systems
Alternative methods for achieving a level floor slab without using cambered beams include: •
Pouring a slab of varying thickness over deflecting beams
•
Using over-sized beams to minimize deflection
•
Shore the beams before placing the concrete
Shoring Concrete At 75% Strength
33
Composite Floor Systems
Beams
When to Camber
•
Girder Beams
•
Filler Beams
•
Members with uniform cross section
•
Composite Floor Beams
34
Composite Floor Systems
Beams
When not Camber
•
Moment Connected Beams
•
Spandrel Beams (above right)
•
Cantilevered Beams (above left)
•
Braced Beams (above right) 35
Composite Floor Systems
Beams
•
Beam with moment connections (above right)
•
Beam under 20 feet length (above right)
•
Beams with loading
•
Beams with connections
non-symmetrical
end
plate 36
Beams
Composite Floor Systems
Heat Cambering •
Beams may be cambered by applying heat to small wedge-shaped areas at specific increments along the beam (Ricker 1989)
•
The beam is place upside down on supports so the “bottom” flange can be heated
•
The heated flange expands under the heat and contracts as it cools
•
Camber is induced in the opposite side of the beam as the heated flange cools
37
Composite Floor Systems
Beams
Cold Cambering •
Cold cambering methods are more widely used and generally more economical than heat cambering
•
The beam is mounted in a frame and force from a ram(s) is used to bend the beam to create camber
38
Beams
Composite Floor Systems
Forms of Incorporating Services within Structural Depth
Beam with Openings
Castellated Beam
Truss 39
Beams
Composite Floor Systems
Beams with web openings
40
Beams
Composite Floor Systems
Beams with web openings • In order to accommodate large service ducts within the structural depth, thus reducing the ceiling to floor zone, large holes are sometimes required through the webs of beams. If these are not too large (say, not greater than 0.6D nor longer than 1.5D), holes without horizontal stiffening may be made provided of course that the remaining web has adequate shear resistance. If larger holes are necessary, stiffeners in the form of horizontal plates welded above and below the hole should be provided. • An alternative to providing customised holes at required locations in a rolled beam is to use a castellated or cellular beam. 41
Beams
Composite Floor Systems
Castellated Beams •
Castellated beams can be used effectively for lightly serviced buildings or for aesthetic reasons, where the structure is exposed. Composite action does not significantly increase the resistance of the beams but increases their stiffness.
•
Castellated beams have limited shear resistance and are best used as long span secondary beams or where loads are relatively low.
42
Beams
Composite Floor Systems
43
Composite Floor Systems
Trusses •
Composite trusses were developed in North America and are popular for spans of 10 to 20m.
44
Composite Floor Systems
Trusses
Typical Truss 45
Composite Floor Systems
Trusses
46
Trusses
Composite Floor Systems
Advantages •
They do not require any special fabrication equipment.
•
They offer plenty of space to accommodate services.
•
They can be designed with a Vierendeel Panels at mid span (where shears are low even under non-symmetric loading); this panel can accommodate an air conditioning duct.
Disadvantages •
The principal disadvantage, other than the increased fabrication cost, is that they are difficult to protect from fire. 47
Trusses
Composite Floor Systems
48
Beams
Composite Floor Systems
Haunched Beams •
Beams are about 20% heavier compared to a rigidly jointed frame but columns are typically 40% lighter, and connection costs are significantly reduced. This "heavy beam/light column" structure makes economic sense when the weight of the beams is similar to that of the columns.
•
Haunched beams are generally designed by forming a rigid moment connection between the beams and columns. The extra service zone created beneath the beam between the haunches, offers flexibility in service layout.
•
At edge columns, it would not be normal practice to develop additional continuity through the slab reinforcement; this, however, is an option at internal columns. This form of construction can be used for sway frames, i.e. where vertical bracing or concrete shear walls or cores are not provided.
49
Beams
Composite Floor Systems
50
Beams
Composite Floor Systems
51
Beams
Composite Floor Systems
52
Beams
Composite Floor Systems
53
Composite Floor Systems
Shear Connectors • Shear connectors are essential for steel concrete composite construction as they integrate the compression capacity of supported concrete slab with supporting steel beams / girders to improve the load carrying capacity as well as overall rigidity.
• Shear Connectors are designed to, Transmit longitudinal shear along the interface. Prevent separation of steel beam and concrete slab at the interface. 54
Shear Connectors
Composite Floor Systems
55
Shear Connectors
Composite Floor Systems
Types of Shear Connectors •
Rigid Shear Connectors
•
Flexible Shear Connectors
•
Anchorage Shear Connectors
Shear connectors to fulfils number of requirements, as follows: • • •
They must transfer direct shear at their base. They must create a tensile link into the concrete. They must be economic to manufacture and fix. 56
Shear Connectors
Composite Floor Systems
Deformation of Flexible Connectors 57
Shear Connectors
•
•
Composite Floor Systems
The electrical arc process is commonly used for stud welding
An arc is drawn between the stud and the base metal
The stud is plunged into the molten steel which is contained by the ceramic ferrule
The metal solidifies and the weld is complete
The ferrules are removed before the concrete is poured
58
Shear Connectors
Composite Floor Systems
•
Depending on the welding process used, the tip of the shear connector may be placed in a ceramic ferrule (arc shield) during welding to retain the weld.
•
Shear connectors create a strong bond between the steel beam and the concrete floor slab which is poured on top of the metal decking.
•
This bond allows the concrete slab to work with the steel beams to reduce live load deflection. 59
Shear Connectors
Composite Floor Systems
As Per IS 11384 : 1985
60
Shear Connectors
Composite Floor Systems
Alternative Forms of Connection Shot fire Connector
Friction grip Connector
61
Composite Floor Systems
Stub Girders •
The system was devised in North America in the 1970s and is described in detail by Chien and Ritchie (1984, 1992).
62
Composite Floor Systems
Stub Girders F lo o r
S t u b w e ld e d t o b o tto m c h o rd S e r v ic e z o n e
C o m p o s it e se c o n d a ry b e a m
F lo o r C o n t in u o u s r ib s
M a in d u c t s
D is t r ib u t io n d u c t s
63
Composite Floor Systems
Stub Girders •
Architectural demand for square column grids with spacing of 10 to 12 m led to the development of stub girder construction.
•
The stub girder comprises a bottom chord, which acts in tension, and a series of short beam sections (or stubs) which connect the bottom chord to the concrete slab. Secondary beams span across the bottom chord and can be designed as continuous members. Voids are created adjacent to the stubs for services.
64
Stub Girders
•
Composite Floor Systems
The major disadvantage of the conventional stub girder is that it requires temporary propping until the concrete has gained adequate strength for composite action. However, it is possible to introduce a light steel top chord, such as a T-section, which acts in compression, to develop the required bending resistance of the girder during execution.
65
Composite Floor Systems
Stub Girders
Stub Girder
66
Stub Girders
Composite Floor Systems
Long Span Stub Girder Grillage Animation
67
Construction Animation
Nail-like fastener is driven Shear throughConnectors the metal deck into the steel beam
Composite System
Installation of Concrete
68
Construction Animation
Nail-like fastener is driven Shear throughConnectors the metal deck into the steel beam
Composite System
Installation of Concrete
69
Construction Animation
Nail-like fastener is driven Shear throughConnectors the metal deck into the steel beam
Composite System
Installation of Concrete
70
Construction Animation
Nail-like fastener is driven Shear throughConnectors the metal deck into the steel beam
Composite System
Installation of Concrete
71
Composite Gravity Systems Composite Floor Systems
Composite Columns
• Metal Deck • Prismatic or Haunched Beams • Shear Connectors • Trusses • Stub girders
72
Composite Columns
Composite Columns •
•
•
A steel composite column is a compression member, comprising either a concrete encased hot – rolled steel section or a concrete filled tubular section of hot- rolled steel and is generally used as a load – bearing member in a composite framed structure. Both steel section and concrete resist external loading by interacting together through chemical bond and friction, or by the use of mechanical shear connectors in particular situation. Additional reinforcement in concrete encasement prevents excessive spalling of concrete both under normal load and fire condition. 73
Composite Columns
Composite Columns
Typical c/s of partially concrete encased sections
74
Columns
Composite Columns
Typical c/s of Fully concrete encased sections
75
Columns
Composite Columns
Stress distribution of the plastic resistance to compression of an encased I section
Pp =
Aa. fy α c. Ac.( 0.80*( fck )cu ) As. fsk + γa + γc γs 76
Columns
Composite Columns
Concrete filled steel column
Cheung Kong Center - Hong Kong
77
Columns
Composite Columns
78
Columns
Composite Columns
79
Connections
Composite Connection
Internal & external semi-rigid beam/column connection
80
Connections
Composite Connection
Composite beam to concrete surface connection
81
82
FOR
Earthquake
83
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