C & MC shapes

STRUCTURAL STEEL SHAPES Welcome to a discussion on C & MCon shapes Based AISC manual 13th edition.

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INTRODUCTI ON Structural steel is one of the basic materials commonly used in structures, such as industrial and commercial buildings, bridges, and piers. It is produced in a wide range of shapes and grades, which permits great flexibility in its usage. It is relatively inexpensive to manufacture and is the strongest and most versatile material available to the construction industry. AISC manual 13th edition classifies the structural steel shapes generally into, I shapes - W, M, S & HP Channels - C & MC Shapes Tee sections - WT, MT & ST Shapes Angles Hollow Structural Sections & Pipe Shapes

Our discussion today focuses Channels on - C & MC Shapes

C SHAPES

Introduction As the name suggests C channels have a shape similar to alphabet “C”. The shape is unsymmetrical with a web, 2 flanges at top and bottom projecting to one of the sides & the other side is flat in the cross section.

Also called American standard channels üCommon, Standard & readily available with most of the manufacturers. üRolled with a constant inner flange surface slope of 2 on 12 ü

C channel is designated as CX Where nominal depth is the overall depth of the member rounded of to a whole number in inches & nominal weight is the weight of the cross section in Lbs/ft. For dimensions & properties refer

C SHAPES

Dimensions & properties Reference: Table 1-5 AISC Manual 13th Edition.

Shape

C3X3.5

Area

Depth

Thickness

A

d

tw

in2

in

in

1.09 3.0

3

0.132

1/8

Width

Average thickness

tw/2

bf

tf

in

in

in

Lb/ft

T

in

in

Workable gage in

1/16 1.37 1”3/8 0.273 1/4 11/16 1”5/8

C15X50 14.7 15.0 15 0.716 11/16

Shear Nomina centre l wt

k

Dimensio ns rts h0

3/8

-

in

in

0.455 2.73

3.72 3”3/4 0.650 5/8 1”7/16 12”1/8 2”1/4 1.17 14.4

Propertie s

Axis X-X

Axis Y-Y

Torsional properties

e0

I

S

r

Z

I

S

r

x

Z

xp

J

Cw

r0

in

in4

in3

in

in3

in4

in3

in

in

in3

in

in4

In6

in

3.5

0.493 1.57 1.04 1.20 1.24 0.169 0.182 0.394 0.443 0.364 0.296 0.0226

50

0.583 404 53.8 5.24 68.5 11.0 3.77 0.865 0.799 8.14 0.490

2.65

H

0.276

1.57 0.645

492

5.49 0.937

General nomenclature used in Table -5 & Table -6 of AISC manual 13th edn. A – Area of cross section (in2) d – Overall depth of the member (in) tw – thickness of web (in) bf - width of flange (in) tf – thickness of flange (in) k – Distance from outer flange of flange to web toe of fillet (in) T – Distance between web toes of fillets at top and at bottom of web (in) rts – Effective radius of gyration (in) h0 – distance between the flange centroids (in) e0 – Shear centre (in) I – Moment Of Inertia (in4)

General nomenclature used in Table -5 & Table -6 of AISC manual 13th edn. S – Elastic section modulus(in3) r – radius of gyration (in) x – Horizontal distance from outer edge of a channel web to its centroid (in) Z – Plastic section modulus(in3) PNA – Plastic neutral axis xp – Horizontal distance from the designated edge of member to its plastic neutral axis (in) J – Torsional constant (in4) Cw – Warping constant (in6) r0 – Polar radius of gyration about the shear center (in) H – Flexural constant

MC SHAPES

Introduction MC or Miscellaneous channels (similar to C channel) have a shape similar to alphabet “C”. The shape is unsymmetrical with a web, 2 flanges at top and bottom projecting to one of the sides & the other side is flat in the cross section.

Also called ship / car channel üNon standard channels & not readily available with all the manufacturers. ü the inner-flange slope of MC-shapes will vary from manufacturer to manufacturer MC is designated as MCX Where nominal depth is the overall depth of the member rounded of to a whole number in inches & nominal weight is the weight of the cross section in Lbs/ft. ü

For dimensions & properties refer

MC SHAPES

Dimensions & properties Reference: Table 1-6 AISC Manual 13th Edition.

Shape

Area

Depth

Thickness

A

d

tw

in2

in

in

MC3X7.1 2.11 3.0

3

0.312 5/16

Width

Average thickness

tw/2

bf

tf

in

in

in

3/16 1.94

2

Dimensio ns rts h0

k

T

in

in

in

1”3/8

-

0.351 3/8 13/16

Workable gage

in

in

0.657 2.65

MC18X5 17.1 18.0 18 0.700 11/16 8 Shear centre Axis X-X Nominal wt e0 I S r Z Lb/ft 7.1 58

3/8

4.20 4”1/4 0.625 5/8 1”7/16 15”1/8 2”1/2 1.35 17.4 Propertie

s

Axis Y-Y I

S

r

x

Torsional properties Z

xp

in in4 in3 in in3 in4 in3 in in in3 in 0.574 2.72 1.81 1.14 2.24 0.666 0.518 0.562 0.653 0.998 0.414 0.695 675 75.0 6.29 95.4

17.6

5.28

1.02 0.862 10.7

0.474

J

Cw

r0

in4 0.0928

In6 0.915

in 1.76

2.81

1070

6.56

MILL TOLERANCES FOR C & MC SHAPES

a A is measured at centerline of web for beams & at back of web for channels b T + T’ applies when flanges of channels are toed in or out

MILL TOLERANCES FOR C & MC SHAPES

Indicates that there is no requirement The permitted variation under the specified length is 0 in for all lengths. c There are no requirements for lengths over 65 ft. The tolerances specified herein are taken from ASTM A6 and apply to the straightness of members received from the rolling mill, measured as d illustrated in Figure 1-1. For tolerance on induced camber & sweep, see Code of standard practice section 6.4.4.

APPLICABLE ASTM SPECIFICATIONS FOR C & MC SHAPES Preferred material specification

Other applicable material specification, the availability of which should be confirmed prior to specification.

Material specification does not apply.

APPLICATIONS OF C & MC SHAPES IN THE STRUCTURAL STEEL CONSTRUCTION INDUSTRY Neither type of shape is very commonly used in structural steel applications for buildings, but the c-shapes may be a little more common. This is mainly due to the cross sectional asymmetry of the section which makes it a back seater when structural properties are the consideration. Asymmetry, slenderness & buckling makes it less favorable for axial loading Relatively lesser resistance to torsion & warping makes the channels less favorable for transverse loading. But it can be can be advantageous in various situations: Channels can be used at floor / roof openings, as stair stringer, door header, door jamb etc by taking advantage of the fact that one of its sides along the major axis is a flat surface. Channels are also used as Platform beams, landing beams, girts, purlins & other light weight applications. Channels are widely used in built-up sections resisting transverse or axial load

Than k you

Viji Anto