Nangarhar University “Engineering Faculty”
Lecture # 1: Introduction To Steel
Structures
Subject: Design of Steel Structures CE411
Instructor: Associate Prof. Mcs Ibadurahmad " Momand"
Lecturer: Bcs Civil Engineer M.Hamid "Elmy"
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Introduction to Steel Structures
Steel Structures:
are one of the main part of structural engineering Course,
widely used as Architecture and civil infrastructure structures
such as; Buildings, Bridges, Towers, Reservoirs and….
Steel Design has direct relation with Statics, Dynamic,
Strength of Materials and Structural Analysis Courses.
Instructor: Ibadurahmad " Momand" Lecturer: M.Hamid "Elmy"
What is Steel
Steel is an Alloy.
An Alloy is a homogeneous mixture of two or more elements, at least
one of which is a metal iron is mixed with carbon and other elements.
A) Plain arbon Steels:
Low carbon [0.15% < C< 0.25%] such as A-36, A-53.
medium carbon [0.25% C < 0.6%] A-500, A-529.
high carbon [0.6% < C < 1.7%] A-570
B) High-Strength Low-Alloy Steels:
Having Fy 40 ksi to 70 ksi, may include chromium,
copper, manganese, nickel in addition to carbon.
e.g. A-242, A-441 and A-572.
C) High Alloy and Special Steels :
These alloy steels which are quenched and tampered
to obtain Fy > 80 ksi. They do not have a well defined
yield point, and are specified a yield point by the “offset
method”, examples are A-709, A-852and A-913.
3 Instructor: Ibadurahmad " Momand" Lecturer: M.Hamid "Elmy"
Effect of Carbon on Steel Properties
Carbon has a major effect on steel properties. Carbon is the primary
hardening element in steel. Hardness and tensile strength increases as
carbon content increases but decrease the elongation.
Steels are described as mild, medium or high-carbon according to the
percentage of carbon they contain, although this is never greater than
about 1.7%.
Mild Steel: Up to 0.25%
Medium Carbon Steel: 0.25% to 0.6%
High Carbon Steel: 0.6% to 1.70%
4 Instructor: Ibadurahmad " Momand" Lecturer: M.Hamid "Elmy"
Structural Steel – Characteristics
Advantage of Steel as Structural material
+ High Strength: the high strength of steel per unite of weight means that the weight of
structural will be small as well ensure the reliability.
+ Uniformity: steel is a homogeneous material and the property will change.
+Elasticity: Ability of metal to return to its original shape after loading and unloading
+Ductility: withstanding extensive Deformation without Failure under high stress.
+ Rapid Construction: Steel Fabrication cause its rapid construction and Performance.
+Toughness: the properties of steel that allowing it to be bent, hammered, sheared and to
have holes punched in without visible damage.
+ Recycling : Steel members can be reused as structure and or as scrape material.
5 Instructor: Ibadurahmad " Momand" Lecturer: M.Hamid "Elmy"
Structural Steel – Characteristics
Disadvantage of Steel as Structural material
- Corrosion: Most steel are susceptible to corrosion when freely exposure to air and
water, and therefore must be painted, periodically, need additional cost.
-Fire proofing: Strength reduces with increased temperature - Fireproofing required.
-Maintenance: maintenance and installation need skilled labor & technician.
- Fatigue: strength may be reduced if it is subjected to a large number of stress
reversal
6 Instructor: Ibadurahmad " Momand" Lecturer: M.Hamid "Elmy"
Structural Steel – Mechanical Properties
o Most widely used standards for structural materials quality and
testing are American Society for Testing of Materials (ASTM)
Standards.
o ASTM specifications for structural steels generally identify the
Process by which steel is to be made, chemical composition, and
tensile strength requirements.
Steel has a unite weight of W=7850Kg/m3,
and Modulus of Elasticity of E=2,100,000 kg/cm2.
With Yield Strength of Fy (240-700) Mpa Grade 36 to Grade100
and corresponding Elongation of (4-40)%.
Reefer to ASTM Table.
7 Instructor: Ibadurahmad " Momand" Lecturer: M.Hamid "Elmy"
Structural Steel – Mechanical Properties
Elastic Limit:
Transition from elastic to
inelastic behavior
Yield Point:
Stress Fy at the elastic limit
Ultimate Point:
Stress Fu at the Failur Point
Elastic Modulus:
Stress and Strain Diagram Slope of elastic part of curve
8 E~29,000 ksi (200,000 Mpa)
Instructor: Ibadurahmad " Momand" Lecturer: M.Hamid "Elmy"
Structural Steel – Mechanical Properties
Yield Strength:
Stress Fy at the highest
point of elastic limit
Ultimate Strength:
Fu is the maximum stress
developed in the inelastic
zone, at the point of fracture
9 Steel Stress and Strain Diagram
Instructor: Ibadurahmad " Momand" Lecturer: M.Hamid "Elmy"
Mechanical Properties of Structural Steels
10 Instructor: Ibadurahmad " Momand" Lecturer: M.Hamid "Elmy"
Type of Structural Steels Sections
• Hot-Rolled Sections.
W S C L WT or ST
(a) Wide-flange (b) American (c) American (d) Angle (e) Structural (f) Pipe (g) Structural
Shape Standard Standard Tee Section Tubing
Beam Channel
a – Wide-flange : W 18 97
b – Standard (I) : S 12 35
c – Channel : C 9 20
(h) Bars (i) Plates
d – Angles : L 64½
e – Structural Tee : WT, MT or ST e.g. ST 8 76
f & g – Hollow Structural Sections HSS : 9 or 8 8
11 Instructor: Ibadurahmad " Momand" Lecturer: M.Hamid "Elmy"
Type of Structural Steels Sections
• Cold Formed Sections
(a) Channels (b) Zees (c) I-shaped double channels
(e) Hat sections (f) Angles
(d) Steel Deck sections
12 Instructor: Ibadurahmad " Momand" Lecturer: M.Hamid "Elmy"
Type of Steels Shapes
Typical Tension Members
13 Instructor: Ibadurahmad " Momand" Lecturer: M.Hamid "Elmy"
Type of Steels Shapes
Typical Compression Members
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Type of Steels Shapes
Typical Beam Members
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Properties of Steels Used for Buildings and Bridges
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Instructor: Ibadurahmad " Momand" Lecturer: M.Hamid "Elmy"
Properties of Steels Used for Buildings and Bridges
17 Instructor: Ibadurahmad " Momand" Lecturer: M.Hamid "Elmy"
Properties of Steels Used for Buildings and Bridges
18 Instructor: Ibadurahmad " Momand" Lecturer: M.Hamid "Elmy"
Uses of Various Steels
19 Instructor: Ibadurahmad " Momand" Lecturer: M.Hamid "Elmy"
The End
Question!
20 Instructor: Ibadurahmad " Momand" Lecturer: M.Hamid "Elmy"
