28.02.2013 Views

Building Design and Construction Handbook - Merritt - Ventech!

Building Design and Construction Handbook - Merritt - Ventech!

Building Design and Construction Handbook - Merritt - Ventech!

SHOW MORE
SHOW LESS

Create successful ePaper yourself

Turn your PDF publications into a flip-book with our unique Google optimized e-Paper software.

STRUCTURAL STEEL CONSTRUCTION 7.5<br />

levels being dependent on thickness of material. The listed thicknesses are precise<br />

for plates <strong>and</strong> nearly correct for shapes. To obtain the precise value for shapes,<br />

refer to an AISC ‘‘Manual of Steel <strong>Construction</strong>’’ (ASD or LRFD) or to mill catalogs.<br />

Weathering Steels. The A242 <strong>and</strong> A588 grades of steel offer enhanced corrosion<br />

resistance relative to A36 material. These steels, called weathering steels, form a<br />

thin oxidation film on the surfaces that inhibits further corrosion in ordinary atmospheric<br />

conditions. However, special treatment of construction details is required.<br />

Because of such constraints, <strong>and</strong> because these grades are more expensive, utilization<br />

of weathering steels in building construction is limited. These grades are<br />

more commonly used in bridge construction.<br />

Steel Grade Identification. Because of the several grades of steel in use, ASTM<br />

specifications require that each piece of hot-rolled steel be properly identified with<br />

vital information, including the heat number. The AISC specifications for structural<br />

steel buildings require fabricators to be prepared to demonstrate, by written procedure<br />

<strong>and</strong> by actual practice, the visible identification of all main stress-carrying<br />

elements at least through shop assembly. Steel identification include ASTM designation,<br />

heat number (if required), <strong>and</strong> mill test reports when specifically ordered.<br />

Availability. Because structural steel is produced in a batch process, the less commonly<br />

used shapes <strong>and</strong> the higher-strength grades are produced less frequently than<br />

commonly used A36 shapes. Furthermore, steel service centers stock the smaller<br />

A36 shapes. As a result, availability of steels can affect construction schedules.<br />

Consequently, steel designers should be aware of the impact of specifying less<br />

commonly used materials <strong>and</strong> shapes if the project has a tight schedule. Fabricator<br />

representatives can provide needed information.<br />

7.2.2 Structural Shapes<br />

Steel mills have a st<strong>and</strong>ard classification for the many products they make, one of<br />

which is structural shapes (heavy). By definition this classification takes in all<br />

shapes having at least one cross-sectional dimension of 3 in or more. Shapes of<br />

lesser size are classified as structural shapes (light) or, more specifically, bars.<br />

Shapes are identified by their cross-sectional characteristics—angles, channels,<br />

beams, columns, tees, pipe, tubing, <strong>and</strong> piles. For convenience, structural shapes<br />

are simply identified by letter symbols as indicated in Table 7.3. The industry<br />

TABLE 7.3 Symbols for Structural Shapes<br />

Section Symbol<br />

Wide-flange shapes W<br />

St<strong>and</strong>ard I shapes S<br />

Bearing-pile shapes HP<br />

Similar shapes that cannot be grouped in W, S, or HP M<br />

Structural tees cut from W, S, or M shapes WT, ST, MT<br />

American st<strong>and</strong>ard chemicals C<br />

All other channel shapes MC<br />

Angles L

Hooray! Your file is uploaded and ready to be published.

Saved successfully!

Ooh no, something went wrong!