Civil Engineering Reference
In-Depth Information
Introduction
1.1 Steel structures
Engineering structures are required to support loads and resist forces, and to
transfer these loads and forces to the foundations of the structures.The loads and
forces may arise from the masses of the structure, or from man's use of the struc-
tures, orfromtheforcesofnature.Theusesofstructuresincludetheenclosureof
space(buildings),theprovisionofaccess(bridges),thestorageofmaterials(tanks
and silos), transportation (vehicles), or the processing of materials (machines).
Structures may be made from a number of different materials, including steel,
concrete, wood, aluminium, stone, plastic, etc., or from combinations of these.
Structuresareusuallythree-dimensionalintheirextent,butsometimestheyare
essentially two-dimensional (plates and shells), or even one-dimensional (lines
andcables). Solidsteelstructuresinvariablyincludecomparativelyhighvolumes
of high-cost structural steel which are understressed and uneconomic, except in
very small-scale components. Because of this, steel structures are usually formed
from one-dimensional members (as in rectangular and triangulated frames), or
from two-dimensional members (as in box girders), or from both (as in stressed
skinindustrialbuildings).Three-dimensionalsteelstructuresareoftenarrangedso
that they act as if composed of a number of independent two-dimensional frames
or one-dimensional members (Figure 1.1).
Structural steel members may be one-dimensional as for beams and columns
(whose lengths are much greater than their transverse dimensions), or two-
dimensional as for plates (whose lengths and widths are much greater than their
thicknesses),asshowninFigure1.2c.Whileone-dimensionalsteelmembersmay
be solid, they are usually thin-walled, in that their thicknesses are much less than
theirothertransversedimensions.Thin-walledsteelmembersarerolledinanum-
ber of cross-sectional shapes [1] or are built up by connecting together a number
of rolled sections or plates, as shown in Figure 1.2b. Structural members can
be classified as tension or compression members, beams, beam-columns, torsion
members, or plates (Figure 1.3), according to the method by which they transmit
the forces in the structure.The behaviour and design of these structural members
are discussed in this topic.
