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University of Anbar Steel Structures (DWE4336)
College of Engineering Dr. Ahmed T. Noaman
Department of Dams & Water Resources Eng. Phase: 4
Semester II (2018-2019)
1
Course Description:
Design of structural steel systems using AISC LRFD code, welded and bolted connections of
axial members, framed and seated shear connections, rigid and semi-rigid moment
connections, base plate connections, beam and column splices, steel concrete composite
construction, and use of software to design typical systems.
Recommended Textbook(s):
---------------------------
Prerequisites:
DWE3313 Strength of materials
DWE3321 Theory of Structures
Course Topics:
1 Structural Design Philosophy, an introduction to the LRFD method.
2 Properties and behavior of structural steel.
3 Strength of tension members, design by codes and specifications.
4 Strength of compression members, design by codes and specifications.
5 Strength of beams in bending, design by codes and specifications
6 Bending and axial forces in beam-columns, design by codes and specifications
7 Introduction to plastic hinges, collapse mechanism.
8 Steel member connections, design by codes and specifications.
9 Design of a complete steel structure (Design of Hydraulic steel structure).
10 Use of commercial software for the design of structural elements
Program and Course Outcomes:
1. Students should be able to design bolted and welded connections and composite (steel/concrete)
beams and columns.
2. Students will also be familiar with the use of plastic analysis to determine failure modes and
Corresponding ultimate capacity of steel structural systems.
3. Students will learn to use commercial software to analyze and design steel structural elements
Class Schedule: 50-minute session (Monday) + 100 -minute session (Thursday) per week
University of Anbar Steel Structures (DWE4336)
College of Engineering Dr. Ahmed T. Noaman
Department of Dams & Water Resources Eng. Phase: 4
Semester II (2018-2019)
2
Methods of Assessment:
Progress exams (P1 and P2) in March and May 2019 (20% marks)
Quizzes (min. two) (5% marks)
Attendance and Class activity (5% marks)
Student Project (5% marks)
Home work (5% marks)
Final exam (60% marks)
Selected References
1. J.C. McCormac and S. F. Csernak , Structural Steel Design, LRFD Method, Prentice Hall, 5th
edition, 2012.
2. Manual of Steel Construction, LRFD, Fourteenth Edition, American Institute for Steel
Construction, 2011
3. W. Segui, Steel Design, Global Engineering, 5th edition, 2013.
4. Design of hydraulic steel structures, ASCE Press, 1997.
University of Anbar Steel Structures (DWE4336)
College of Engineering Dr. Ahmed T. Noaman
Department of Dams & Water Resources Eng. Phase: 4
Semester II (2018-2019)
3
Chapter one
Introduction
1. Types of steel structures:
1 – Building: (1) public, (2) industrial, (3) residential
2 – Bridges: (1) pedestrian, (2) over ground, (3) railroads
3 – Others: (1) transmission towers , (2) vessels , (3) gates , (4) tanks (5) ships and air planes
2. Steel:
The basic constituent of structural steel is iron, an element widely and liberally available over the
world’s surface but with rare exceptions found only in combination with other elements. The main
deposits of iron are in the form of ores of various kinds which are distinguished by the amount of
metallic iron in the combination and the nature of the other elements present. The most common ores
are oxides of iron mixed with earthy materials and chemically adulterated with, for example, sulphur
and phosphorus. Iron products have three main commercial forms; wrought iron, steel and cast iron in
ascending order of carbon content.
Table 1.1, which gives some physical properties of these three compounds, shows that as the carbon
content of the metal increases the melting point is lowered; this fact has considerable importance in the
production process. Modern steelmaking depends for its raw material on iron produced by a blast
furnace. Iron ore is charged into the furnace with coke and limestone. A powerful air blast raises the
temperature sufficiently to melt the iron, which is run off. The iron at this stage has high carbon
content; steel is obtained from it by removing most of the carbon. In the most modern processes
decarburizing is done by blowing oxygen through the molten iron.
University of Anbar Steel Structures (DWE4336)
College of Engineering Dr. Ahmed T. Noaman
Department of Dams & Water Resources Eng. Phase: 4
Semester II (2018-2019)
4
3. Advantages of steel as a structural material
1. High strength
2. Uniformity
3. Elasticity
University of Anbar Steel Structures (DWE4336)
College of Engineering Dr. Ahmed T. Noaman
Department of Dams & Water Resources Eng. Phase: 4
Semester II (2018-2019)
5
4. Permanence
5. Ductility
6. Toughness
7. Addition to existing structures
University of Anbar Steel Structures (DWE4336)
College of Engineering Dr. Ahmed T. Noaman
Department of Dams & Water Resources Eng. Phase: 4
Semester II (2018-2019)
6
8. Miscellaneous
4. Disadvantages of steel:
1. Corrosion
Cavitation
University of Anbar Steel Structures (DWE4336)
College of Engineering Dr. Ahmed T. Noaman
Department of Dams & Water Resources Eng. Phase: 4
Semester II (2018-2019)
7
2. Fireproofing cost
3. Susceptibility to buckling
4. Fatigue
University of Anbar Steel Structures (DWE4336)
College of Engineering Dr. Ahmed T. Noaman
Department of Dams & Water Resources Eng. Phase: 4
Semester II (2018-2019)
8
5. What is Steel? " Steel Properties"
- It's an alloy of iron and the nonmetallic element carbon 0.3 – 0.2 % .
Carbon steels "structural"
High strength or low alloy
Tempered alloy
6. Stress - Strain diagram for steel
University of Anbar Steel Structures (DWE4336)
College of Engineering Dr. Ahmed T. Noaman
Department of Dams & Water Resources Eng. Phase: 4
Semester II (2018-2019)
9
Table (2-4) page 2 – 48 structural steel specifications AISC "
American Institute of Steel Construction" – LRFD " Allowable stress
Design " Manual
Example: A36 fy = 36 ksi (yield stress)
fu = 58 ksi (ultimate strength)
ε
0.002
Modulus of elasticity for aluminum is 10,000 ksi while for steel is ≈ 30000
ksi. Thus , the elastic deformation of an aluminum structure = 3 times that
of an identically loaded steel structure of the same dimensions
- yield of aluminum fy = 35 ksi
Strength = 38 - 42 ksi
- weight of alloy is about 36% as much as steel , besides
resistance to corrosion , reduced maintenance but higher initial
cost.
fy fu
σ
High strength steel
University of Anbar Steel Structures (DWE4336)
College of Engineering Dr. Ahmed T. Noaman
Department of Dams & Water Resources Eng. Phase: 4
Semester II (2018-2019)
10
7. Structural Steel sections
(5 – 1) standard rolled shapes:
They are formed from hot steel by passing through roll several times to
obtain the desired shape.
Standard Sections
1 – W section (wide – flange section)
W36*230 tables (p.p. 1 – 12 , 1 -29)
36. nominal depth
230 weight of sect. per foot
2 – S section (Standard beam section)
S18*70 table (p.p. 1 – 32 , 1 -33)
3 – M shapes (Special sections from W sections)
Tables (p.p. 1 – 30 , 1 -31)
4 – HP shapes
Tables (p.p. 1 – 34 , 1 -35)
University of Anbar Steel Structures (DWE4336)
College of Engineering Dr. Ahmed T. Noaman
Department of Dams & Water Resources Eng. Phase: 4
Semester II (2018-2019)
11
5 – Channel shape (C – shape)
Tables (p.p. 1 – 36 , 1 - 37)
C12*30
12. depth
30 weight
6 – MC shapes
Special type of C shapes
7 – Angles (L – shapes)
L1 * L2 * t
Tables (p.p. 1 – 42 , 1 - 49)
8 – T sections
Tables (p.p. 1 –50 , 1 - 69)
University of Anbar Steel Structures (DWE4336)
College of Engineering Dr. Ahmed T. Noaman
Department of Dams & Water Resources Eng. Phase: 4
Semester II (2018-2019)
12
9 – Pipes
1 – circular , 2 – square , 3 – rectangular
Tables (p.p. 1 –74 , 1 - 101)
10 – Bars and Plates
Bars: circular, square, rectangular , etc.
Page (1 – 138)
11 – Rails page (1 -112)
(5 – 2) Cold – formed steel shapes:
Made by bending thin sheets of carbon or low alloy steel into almost any
desired section.
University of Anbar Steel Structures (DWE4336)
College of Engineering Dr. Ahmed T. Noaman
Department of Dams & Water Resources Eng. Phase: 4
Semester II (2018-2019)
13
8. Loads
Structures have to carry different types of loading. These can be broadly
divided into two categories dead, and live loads.
(1) Dead Loads
They are loads due to self-weight (mass) of the structure. They are
includes structural frames' own weight and other loads that are
permanently attached to frame, like, pipes , electrical conducts, air
conditioning and heating ducts , lighting fixtures, roof covering,
suspended ceilings.
. (2) Live Loads
They're all loads other than dead load." Like : human, furniture, movable
equipments , vehicles , and snow or rain …. etc."
Floor loads
They're uniformly distributed static loads.
UBC1999 "Unified Building Code: "
University of Anbar Steel Structures (DWE4336)
College of Engineering Dr. Ahmed T. Noaman
Department of Dams & Water Resources Eng. Phase: 4
Semester II (2018-2019)
14
Snow loads
Density 5 – 6 pcf
Flat surfaces 30 – 40 psf
Inclined surfaces (horizontal projection) 10 psf
Wind Loads
Special considerations for wind are required for tall buildings.
The N.B.C. recommended the following wind pressure
For tanks and chimneys, tunnels, the above values should be multiplied by
shape factor.
Wind pressure can be approximately predicted as follows (Bernoulli's
equation):
q = 0.5 ρ v2 ----------- (1)
where:
q = pressure in psf
ρ = mass density of air
v = velocity in mph
ρ = 0.0765 pcf ----------- (2)
Height (ft) Wind pressure (psf)
Less than 30 15
30 – 49 20
50 – 99 25
100 – 499 30
Shape of Structure factor
Rectangular and square 1
Hexagonal and octagonal 0.8
Round or elliptical 0.6
University of Anbar Steel Structures (DWE4336)
College of Engineering Dr. Ahmed T. Noaman
Department of Dams & Water Resources Eng. Phase: 4
Semester II (2018-2019)
15
q = 0.00256 v2 ------------- (3)
Aerodynamic effects “sloping roofs"
+ suction -
Wind ward Wind leeward
α
When considering aerodynamic effects:
P = C q
P = static pressure
C = coefficient suggested by ASCE
α = slope of the roof
C = -0.7 (α ≤ 20◦)
C = 0.07 α – 2.1 (20◦ < α ≤ 30
◦)
C = 0.03 α – 0.9 (30◦ < α ≤ 60
◦)
C = 0.9 (α >60)
For leeward surface: C = -0.6
Impact and Dynamic loads
The term “impact" refers to extra static load applied to approximate the
dynamic effect of a suddenly applied load like cranes and various types of
machinery.
If = 25L
50
≤ 0.3
L = length of portion of span (ft)
If = impact factor
University of Anbar Steel Structures (DWE4336)
College of Engineering Dr. Ahmed T. Noaman
Department of Dams & Water Resources Eng. Phase: 4
Semester II (2018-2019)
16
Impact load (static) = dynamic load * (1 + If)
Or If = 1 for elevator
= 0.25 for machinery
Traffic loads
Highway traffic is made up for four principal kinds of vehicles – the truck
tractor, truck, bus, and passenger car.
Earthquake loads
W W
Cw = inertia reaction
Earth motion
(a) @ rest (b) under horizontal motion
from an earthquake
Water and Soil pressure
P = γ h
γ = density of soil or water
h = difference between the reference level and the surface of the liquid or soil
γ soil = 90 – 120 lb/ft3
γ water = 62.4 lb/ft3
University of Anbar Steel Structures (DWE4336)
College of Engineering Dr. Ahmed T. Noaman
Department of Dams & Water Resources Eng. Phase: 4
Semester II (2018-2019)
17
9. Methods of Design
In Steel Structures DWE4336, we consider AISC specifiications and methods:
1. Allowable Stress Design (ASD)
2. Load and Resistance factor Design (LRFD)
3. Plastic Analysis and Design
1 - Allowable Stress Design (ASD)
It's called also working stress method. The analysis in this method is based on the
use of:-
1. classical analytical formulae of stress and strain
2. actual working loads (service loads)
2 – Plastic analysis and design.
based on a consideration of failure conditions rather than working load
conditions. A member is selected by using the criterion that the structure will fail
at a load substantially higher than the working load. Failure in this context means
either collapse or extremely large deformations. The term plastic is used because,
at failure, parts of the member will be subjected to very large strains—large
enough to put the member into the plastic range.
3 – Load and Resistance Factor Design.
Design strength = Φ actual strength
University of Anbar Steel Structures (DWE4336)
College of Engineering Dr. Ahmed T. Noaman
Department of Dams & Water Resources Eng. Phase: 4
Semester II (2018-2019)
18
30 '
30 '
Ex1: For the gable frame shown in fig. below, if wind speed = 180 mph,
roof dead load = 15 lb/ft2. Determine:
1 – The magnitude and direction of the force applied at point O due to the
roof load.
2 – The uniform static load applied due to the wind and the load transmitted
by the purlin to the point O
Solution:
Length of rafter ab = √ 212 + 30
2 = 36.6 ft
Length between each purlin = 36.6/3 = 12.2'
6 @ 10ft = 60 ft
21 ft
Purlin beam
Frame
Rafter
20 ft
University of Anbar Steel Structures (DWE4336)
College of Engineering Dr. Ahmed T. Noaman
Department of Dams & Water Resources Eng. Phase: 4
Semester II (2018-2019)
19
1) Load on point O :
(15/1000) * 12.2 *30 = 5.5 kips
2) q = 0.00256 v2 , q = 0.00256 (180)
2 = 16.4 lb/ft
2
α = 35 , C = 0.03 α – 0.9 (30 < α ≤ 60)
C = +0.15 (comp.)
For the leeward surface C = - 0.6
Wind ward : P = 0.15 * 16.4 = 2.46 lb/ft2
U.S.L.(windward) = 2.46 * 30 = 73.8 lb/ft
U.S.L.(leeward) = 0.6*16.4 * 30 = 295.2 lb/ft
For point O : load = 73.8*12.2 = 900.36 lb
10. Introduction to LRFD:
The factored resistance ɸRn is called the design strength. The summation on
the left side of Equation above is over the total number of load effects
(including, but not limited to, dead load and live load), where each load
effect can be associated with a different load factor. Not only can each load
effect have a different load factor but also the value of the load factor for a
particular load effect will depend on the combination of loads under
consideration. Equation above can also be written in the form: