ABSTRACT
Glossary .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-99
References .. .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-100
Further Reading.... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-102
Relevant Websites .. . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-103
Structural steel is a construction material that possesses attributes such as strength, stiffness, toughness,
and ductility that are desirable in modern constructions. Strength is the ability of a material to resist
stress. It is measured in terms of the material’s yield strength Fy and ultimate or tensile strength Fu. Steel
used in ordinary constructions normally have values of Fy and Fu that range from 36 to 50 ksi (248 to
345 MPa) and from 58 to 70 ksi (400 to 483 MPa), respectively, although higher-strength steels are
becoming more common. Stiffness is the ability of a material to resist deformation. It is measured in
terms of the modulus of elasticity E and modulus of rigidity G. With reference to Figure 4.1, in which
several uniaxial engineering stress-strain curves obtained from coupon tests for various grades of steels
are shown, it is seen that the modulus of elasticity E does not vary appreciably for the different steel
grades. Therefore, a value of 29,000 ksi (200 GPa) is often used for design. Toughness is the ability of a
material to absorb energy before failure. It is measured as the area under the material’s stress-strain
curve. As shown in Figure 4.1, most (especially the lower grade) steels possess high toughness that made
them suitable for both static and seismic applications. Ductility is the ability of a material to undergo
large inelastic (or plastic) deformation before failure. It is measured in terms of percent elongation or
percent reduction in area of the specimen tested in uniaxial tension. For steel, percent elongation ranges
from around 10 to 40 for a 2-in. (5-cm) gage length specimen. Ductility generally decreases with
increasing steel strength. Ductility is a very important attribute of steel. The ability of structural steel to
deform considerably before failure by fracture allows an indeterminate structure to undergo stress
redistribution. Ductility also enhances the energy absorption characteristic of the structure, which is
extremely important in seismic design.
