This document discusses different types of steel structures, including welded, bolted, composite, hot-rolled, and cold-formed steel structures. It provides examples of each type, noting that welded connections were prone to brittle fracture during earthquakes in the 1990s, while bolted connections are easier to install. Composite steel-concrete columns and concrete-filled steel tubes offer advantages like enhanced ductility and strength. Hot-rolled steel is formed at high temperatures, while cold-formed steel uses low-temperature processes like rolling and pressing of thin sheets. Cold-formed steel is commonly used residential and commercial construction.

1. Steel Structure
CE4101

2. Outlines
Steel Structure
Welded structure
Bolted structure
Stee-composite structure
Cold-formed steel
Hot rolled steel

3. 3
Background and Introduction
• Steel Moment Resisting Frames (MRFs): oldest structural forms and are
in use in all regions for many decades.
• Rectilinear assemblage of beams and columns, with beams rigidly
connected to the columns.
• By the virtue of rigid beam-column joints, frames cannot displace
laterally under the action of lateral loads without developing shear force
and bending moment.
• Steel MRFs can be broadly classified into two categories: braced and
unbraced frames.

4. Building in Singapore
Industrial Structure
Structural Connection
Benefits of Steel Structure
1. Lightweight to strength
Capacity.
2. Ductile in nature.
3. Speedy Construction.
4. Fire Resistance
5. Easy Installation
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5. The most vulnerable part of the steel structure
Steel Connections
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6. Why does steel construction need to study?
• The approach regarding the ductile behavior of the steel MRFs was significantly challenged by the Northridge
earthquake (Los Angeles, California, USA) in 1994 and Hyogo-ken Nanbu (Kobe) earthquake (Japan) in 1995.
• These earthquakes caused significant damage to almost 60% of the steel Moment Resisting Frame (MRF) buildings.
• The effect of these earthquakes particularly on steel buildings was the unexpected and widespread occurrence of
brittle beam-column connection fracture.
Source: Verisk Analytics Source: Insurance Journal Source: usgs.gov
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7. 1. Real Example of Poor Construction
Northridge Earthquake, 1994 (USA)
Casualties: 72 Injured: 1500 (1000 homeless) Property Damage > $15 B
Northridge earthquake data
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8. Casualties: 6434; Injured: 35000 (30000 homeless); Property Damage > $150 B
Kobe Earthquake, 1995 (Japan)
1. Real Example of Poor Construction
2. Real Example of Poor Construction 8

9.  Poor construction
practice
 Poor load carrying
capacity of column
 Welds were fractured.
 Bolts were failed
Observations
Impact
Cause
Assam
Earthquake
(1950)
Sikkim
Earthquake
(2011)
Nepal
Earthquake
(2015)
Manipur
Earthquake
(2016)
3. Real Example of Poor Construction in India 9

10. Welded Connection
 Generally, the deep rolled beam and column sections are [W30×99 and W36×150] used
in connection.
 Bolted shear tab is used to transfer shear forces.
 Complete Joint Penetration (CJP) groove welding is used for moment connection.
 Type of welding: E70T-4
Typical connection for
pre-Northridge SMRF.
(Popov et al. 1969; Popov et al. 1970; Popov et al. 1972)
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11. [Popov et al. 1969; Popov et al. 1970; Popov et al. 1972; Popov et al. 1973, Carpenter et al. 1973; Beedle et al.
1973; Chen el al. 1981]
Welded Connection
 Before 1994, Uniform Building Code (UBC) presumed that only welding can
satisfy the beam-to-column connection requirements.
 Welded connections have been investigated by a number of researchers between
1969 and 1984.
 Results showed that only the shallow specimens with welding were adequate for
construction.
 Bolting construction is required.
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12. Critical observations in welded construction
 Brittle fracture in welded connection.
 Fracture occurred in welding and bottom
flange and it extended to the column web and
flange.
 Under SAC program twelve specimens were
selected for laboratory test.[W18×50 and
W24×76]
 Results showed that the welded connections
had a very low performance under critical
conditions due to poor construction
methodology and poor material performance Typical fracture paths at the welded beam-to-
column connection
(Popov et al. 1994)
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13. 13
Bolted Connection

14. 14
 The installation process of nuts and bolts is far easier and more efficient when compared
to welding.
 Welding requires skilled labour, special equipment, and safety measures, whereas nuts
and bolts require simple tools and unskilled labour also makes it cost-efficient.
The connection supports loads as soon as the bolts are tightened.
Noiseless and quick fabrication, fast progress of work.
No special equipment is needed for installation.
Use of unskilled labour and simple tools.
Bolted Connection

15. Steel-Concrete Composite Structure
 Steel-concrete composite columns are among the most common type
of composite structural system used in USA, Europe, Japan, China
and Taiwan.
 Composite steel-concrete structures are used as earthquake resistant
structure.
 There are two types of composite columns: Concrete encased
structural steel columns and Concrete-filled tube. (CFT).
(Shakir et al. 1992; Kanatani et al. 1987; Wu et. al. 2016)
15

16. The Casting of Composite Column in
Structural Engineering Lab
at IIT Guwahati.
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17. Concrete Fill Tube
 Concrete-Filled Steel Tubes (CFTs) are composite members consisting of a steel tube in filled
with concrete.
 CFT columns are used in lateral resistance systems for bridge piers, retrofitting purposes for
strengthening concrete columns in earthquake zones.
The advantages of CFT
 The tube eliminates the column
formwork during construction.
 The steel pipe prevents breaking of
concrete.
 The concrete prolongs the local
buckling of pipe wall.
(Kanatani et al. 1987; Wu et al. 2016)
Applications of CFT
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18. Unique Characteristics of Concrete Filled Tube
 It enhances the ductility.
 It can resist much more bending moment in tension.
 It enhances the stiffness capacity.
 CFT increases the compressive strength.
 It provides natural reinforcement for the panel zone, which reduces the material
and labor costs of the connections.
(Webb, 1993)
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19. Hot-rolled steel structure
Hot rolled steel is easier to make, shape and form.
It has its source in a mill process involving rolling the steel at high
temperature.
It starts from a piece of still billet which is heated up to 1700 degrees
Fahrenheit (926° Celsius) and
Then the steel is rolled through the mill into the particular shape
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20. 20

21. 21

22. Cold-formed steel structure
Cold-formed steel members fabricated from
thin sheets using folding, rolling, or
press braking operations
Lighter, economical, and offers faster
construction than traditional hot-
rolled members
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23. Cold-formed steel residential building (Chennai) 23
Cold-formed steel (CFS) is the common term for steel products shaped by cold-
working processes carried out near room temperature, such
as rolling, pressing, stamping, bending, etc.
Cold-formed steel, especially in the form of thin gauge sheets, is commonly
used in the construction industry for structural or non-structural items
such as columns, beams, joists, studs, floor decking, built-up sections and
other components

24. Cold-formed steel house (Vizag)
24

25. Steel building (Raigarh)
25

26. Different types of cold-formed steel section
IS 811: (1987)Cold-Formed Light Gauge Structural Steel
Sections
IS 801: (1975) Code of practice for use of cold-formed light
gauge steel structural members in general building
construction
Revision (2001)
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27. LOCAL BUCKLING
DISTORTIONAL BUCKLING
LATERAL-TORSIONAL
(GLOBAL) BUCKLING
The main instabilities of cold-formed steel beams 27

28. Failure Types of Cold-formed steel section
LOCAL BUCKLING
28

29. Failure Types of Cold-formed steel section
LATERAL-TORSIONAL
(GLOBAL) BUCKLING
29

30. Failure Types of Cold-formed steel section
DISTORTIONAL BUCKLING
30