This document discusses the advantages and disadvantages of steel as a structural material. It notes that steel has high strength, uniformity, elasticity, permanence, ductility, and toughness. However, it requires maintenance against corrosion and fireproofing. Steel is also susceptible to buckling if members become too long and slender. Additionally, steel strength can reduce due to fatigue, brittle failure, and residual stresses. The document provides information on common steel grades used in design and their properties.

1. 1 Prepared by Prof. Shehab Mourad – Department of Civil Eng. - KSU
Introduction to Structural Steel Design
- Advantages of Steel as a Structural Material:
1- High Strength
High strength of steel per unit weight means that the weight of
structure will be small, which has a great importance for large
structures, as bridges and tall buildings.
Typical used structural steel in design
Grade Fy MPa Fu
(MPa)
ASTM designation Availability
A 36 250
(36 ksi)
400
A36M For most applications
G 50
350
(50 ksi) 450
A572M For most applications
A529M
For thin-plate members
only
A242M, A588M
For corrosion-resistance
steel

2. 2 Prepared by Prof. Shehab Mourad – Department of Civil Eng. - KSU

3. 3 Prepared by Prof. Shehab Mourad – Department of Civil Eng. - KSU
2- Uniformity
Uniform and consistent properties with time
3- Elasticity
Steel behaves closer to design assumption (elastic, follows
Hooke's law) up to high stresses
4- Permanence
With proper maintain ace steel structures can last indefinitely
5- Ductility
Steel can withstand extensive deformation without failure under
high tensile stresses. Ductility gives more warning before failure.
6- Toughness
Steel members can still withstand large forces even it has large
deformations. The ability of material to absorb energy in large
amounts is called toughness.
7- Additions to Existing Structures
Existing steel structures can be easily expanded both in width and height

4. 4 Prepared by Prof. Shehab Mourad – Department of Civil Eng. - KSU
8- Miscellaneous
-Ability to fasten members together
- Ability to prefabrication
- Speed of erection
-Ability to be rolled into a wide Varity of sizes and shapes
- Ability to form built up section from standard sections
-Possible reuse and recycle after disassembling
-Can be used with concrete to form composite sections

5. 5 Prepared by Prof. Shehab Mourad – Department of Civil Eng. - KSU
- Disadvantages of Steel as a Structural Material:
1- Maintenance Costs
Most steels are susceptible to corrosion when freely exposed to
air and water, therefore it should be painted periodically,
otherwise weathering steel should be used.

6. 6 Prepared by Prof. Shehab Mourad – Department of Civil Eng. - KSU
2- Fireproofing Costs
Steel strength is tremendously reduced at temperature
commonly reached in fires; therefore steel members should be
painted by fire proofing materials.

7. 7 Prepared by Prof. Shehab Mourad – Department of Civil Eng. - KSU

8. 8 Prepared by Prof. Shehab Mourad – Department of Civil Eng. - KSU
3- Susceptibility to Buckling
As the member length increases, its danger of buckling
increases, therefore, steel sections need to be increased and
stiffened to avoid buckling.
Global Buckling Torsional Buckling
Local Buckling in Flanges and Web

9. 9 Prepared by Prof. Shehab Mourad – Department of Civil Eng. - KSU
4- Fatigue
Steel strength is reduced when subjected to a large number of stress
reversals or even a large number of variations of tensile stress.

10. 10 Prepared by Prof. Shehab Mourad – Department of Civil Eng. - KSU
5- Brittle Failure
Steel may lose its ductility in certain conditions, and brittle
failure may occur at places of stress concentrations
Brittle failure along the Weld
Brittle failure of Bolts

11. 11 Prepared by Prof. Shehab Mourad – Department of Civil Eng. - KSU
6- Residual Stresses
Residual stresses occur due to;
1- Uneven cooling of room temperature of hot rolled sections
2- Cold bending of cold formed sections
3- Welding of two or more plates together