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Design of Tension Member
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CE319
Design of Steel Structures
Maj. Dr. Khondaker Sakil Ahmed
Instructor Cl B
Department of Civil Engineering, MIST
CE 319: DESIGN OF STEEL STRUCTURES 3.00 CREDITS, 3 HRS/WEEK
Syllabus
1. Behavioral principles and design of structural steel2. Design of tension members 3. Bolted and welded connections 4. Compression members, residual stress, local buckling,
effective length 5. Flexural members, lateral torsional buckling 6. Design of beam-columns 7. Connection design, moment connection, column bases 8. Detailing of steel structures
REFERENCE BOOKS OR MANUALS
Main text book Steel Structures:
Design and Behavior, 5th Ed., 2009 Authors: Salmon, Johnson and Malhas, Publisher: Pearson – Prentice Hall
Other books and references
1. Theory of Simple Structures, 2nd Ed. 2001: Authors: T.C. Sheddand J. Vawter
2. Design of Steel Structures, 3rd Ed., 1991 Authors: Gaylord, Gaylord and Stallmeyer, Publisher: McGraw-Hill
3. Specifications for Structural Steel Buildings, 2005 Author: American Institute of Steel Construction (AISC)
4. Manual for Steel Construction, 13th Edition, 2005 Author: American Institute of Steel Construction (AISC)
DESIGN PRINCIPLE
Resistance ≥ applied load
Resistance ??
Material Property
Geometry
Soil Bearing Capacity
BC
LIMIT STATE
Loading condition defines failure mode
Limit of loading after which structure fails
Three broad classification
Strength limit states
Serviceability limit states
Special limit states
DESIGN CONSIDERATION
Adequate strength & Stiffness during service life
Adequate Margin of safety
COST ! Economical Design
Probability of failure based on design approach
Prevent limit state
Brittle Behavior
Experience
ASD & LRFD
TYPICAL SECTIONS
Cold Formed
ADVANTAGES OF STEEL
Uniform & Homogeneous ; Strength predictable
Higher strength comparative to other
High Ductility: Easy to understand failure
Easier and quicker to fabricate
Easier and quicker to build
Recycled
Not affected by weather
Easy to repair, maintain and inspect
DISADVANTAGES
Higher Cost
Not perfectly Susceptible to Environment particularly higher chance of corrosion if not properly coated: Extra Cost for Corrosion Resistance
Low fire resistance
Stress Concentration due to mismatch
Fracture, fatigue : Cyclic loading
STEEL VS CONCRETE (DESIGN & BUILT)
1. Cheap2. Less Earthquake Resistance3. Generally Cast in Place4. Flexible size and shape5. Easier connections6. Low chance of buckling7. High self weight8. Require longer construction time9. More fire resistant10.Easier maintenance11.Comparatively Safe against
Blast load12.Difficult repair and retrofit
1. Comparatively expensive2. Better Earthquake Resistance3. Generally prefabricated4. Defined size and shape5. Critical connections: Req Design6. High chance of buckling7. Low self weight8. Very Short construction time compare to
concrete9. More fire resistant10.Easier maintenance11.Not Safe against Blast load12.Easier repair and retrofit and
strengthen
TYPES OF STEEL BASED ON STRENGTH
CONSTITUTIVE LAW
STEEL STRESS-STRAIN BEHAVIOR
DESIGN METHODS-1
LRFD
Resistance or strength:Rn
Resistance factor:φ<1.0
Load Effect: Qi
Load Factor: γi
Ru: Factored Load Effect
LRFD Safety Eqn: φ Rn≥ Ru
nii RQ
DESIGN METHODS-2
ASD
Resistance or strength:Rn
Safety factor: Ω >1.0
Load Effect: Qi
Load Factor: γi=1.00
Ra: Allowable Strength
ASD Safety Eqn: Rn/Ω ≥ Ru iQ
DESIGN OF TENSION MEMBERS
Structural Elements Subjected to Axial Tensile Forces
Cables in Suspension and Cable-Stayed Bridges
Trusses
Bracing for Buildings and Bridges
DESIGN OF STEEL TENSION MEMBERS
What is the maximum P?
LRFD Equation
P P
nii RQ
Next Class
DESIGN OF STEEL TENSION MEMBERS
Equations for strength of tension members:
a) For yielding in the gross section:
b) For fracture in the net section:
gyn AFR
eun AFR
P P
DESIGN OF STEEL TENSION MEMBERS
Yielding in the gross section:
Max stress FyP P
Max stress Fu
YIELD STRESS OF GROSS SECTION
STRENGTH OF TENSION MEMBERS
NET AREA CALCULATION
NET AREA (An) CALCULATION
NET AREA CALCULATION EXAMPLE
DESIGN OF STEEL TENSION MEMBERS
Equations for strength of tension members:
a) For yielding in the gross section:
b) For fracture in the net section:
gyn AFR
eun AFR
90.0
75.0
IMPORTANT NOTES
LOAD COMBINATION
EFFECTIVE AREA (Ae)
Ae ?
DETERMINATION OF L
W M S SHAPES
U FOR WELDED CONNECTION (1/2)
U FOR WELDED CONNECTION (2/2)
OTHERS
EXAMPLE-1
EXAMPLE 2
EXAMPLE-3
NEXT CLASS
BLOCK SHEAR
