On this page: [Laps] [Safety Factors] [Yields] [Material Specifications]

 

 

Design Information

Laps

Lap Conditions
Laps are reported in the tables for L (left) and R (right) as depicted below.

I-C-1

15 October 1998

 

 

Lap Notations
Laps are noted on the Laterally Braced and Continuously Braced Capacities tables as L and R. Laps are measured from the support to the end of the lap. L denotes the lap at the left end of the span and R denotes the lap at the right end of the span. The lap notations and related lengths are shown in the table below.

Notation

Length

0

no lap (at the end support)

1

1 ft. 1 ¾ in.

2

2 ft. 1 ¾ in.

3

3 ft. 1 ¾ in.


Lap Optimization
The optimization process includes selecting the best laps for each condition. Laps are permitted to vary from support to support, and from left to right at a support. In the area of the lap, the moment of inertia of both sections is used in determining required forces and deflections. Gauge changes are not considered. LGSI suppliers have the capability of optimizing both laps and gauges. Contact your LGSI supplier for assistance with large projects where this may be a consideration.

 

Safety Factors

Appropriate factors of safety have been applied as specified in the 1996 AISI specifications, ASD provisions.

 

Symbol

AISI Reference

Safety Factor

Web crippling

Pw

C3.4

Ww = 1.85

Bending

M

C3.1

Wb = 1.67

      Fully braced

  

C3.1.1

Wb = 1.67

      Laterally braced

  

C3.1.2

Wb = 1.67

      Through-fastened

  

C3.1.3, C3.1.4

Wb = 1.67

Shear

V

C3.2

Wv = 1.67

Axial Compression

P

C4

Wc = 1.80

      Through-fastened

Ptf

C4.4

Wc = 1.80

 

Yields

For all sections, Fy is 55 ksi and Fu is 67.7 ksi.

I-C-2

15 October 1998

Material Specifications

Structural properties relevant to cold-formed steel include yield point, tensile strength, elongation in 2 inches and ratio of tensile strength to yield point. Ductility, the ability of the material to undergo sizable plastic or permanent strains before fracturing, is measured by the percent elongation in 2 inches. The ability of the material to redistribute stress is reflected by the ratio of tensile strength to yield point. The following table (based on ASTM Specifications) lists materials used by LGSI member companies in manufacturing LGSI sections. An Fy of 55 ksi is required for LGSI sections (Reference page I-C-2).

 

 

ASTM Designation: A570/A570M-95

LGSI MEMBERS: ACI, Galvak, MBCI, McElroy, Metal Sales, NCI




SCOPE (After ASTM)




PRODUCT




GRADE


Fy
ksi
(min)


Fu
ksi
(min/max)

Percent
elongation
in 2 inches
(min)




Fu / Fy

This specification covers hot-rolled carbon steel sheet and strip of structural quality in cut lengths or coils. This material is intended for structural purposes where mechanical test values are required, and is available in a maximum thickness of 0.229 in. (6.0 mm) except as limited by Specification A568, A568M, A749, or A749M

Sheet
and Strip

30
33
36
40
45
50
55

30
33
36
40
45
50
55

49
52
53
55
60
65
70

21 to 25
18 to 23
17 to 22
15 to 21
13 to 19
11 to 17
9 to 15

1.63
1.58
1.47
1.38
1.33
1.30
1.27

I-C-3

15 October 1998

 

ASTM Designation: A607-92a

LGSI MEMBERS: ACI, Galvak, MBCI, NCI




SCOPE (After ASTM)




PRODUCT




GRADE


Fy
ksi
(min)


Fu
ksi
(min/max)

Percent
elongation
in 2 inches
(min)




Fu / Fy

This specification covers high-strength, low-alloy columbium, or vanadium hot-rolled sheet and strip, or cold-rolled sheet, or combinations thereof, in either cut lengths or coils, intended for applications where greater strength and savings in weight are important. The material is available as two classes. They are similar in strength level except that Class 2 offers improved weldability and more formability than Class 1. Atmospheric corrosion resistance of these steels is equivalent to plain carbon steels. With copper specified, the atmospheric corrosion resistance is twice that of plain carbon steel. Class 1 material was previously A607 without a class designation.

Sheet
and
Strip

Class 1
45

50

55

60

65

70

Class 2
45

50

55

60

65

70


45

50

55

60

65

70


45

50

55

60

65

70


60

65

70

75

80

85


55

60

65

70

75

80


Hot-Rolled 23-25
Cold-Rolled 22
Hot-Rolled 20-22
Cold-Rolled 20
Hot Rolled 18-20
Cold-Rolled 18
Hot-Rolled 16-18
Cold-Rolled 16
Hot-Rolled 14-16
Cold-Rolled 15
Hot-Rolled 12-14
Cold-Rolled 14

Hot-Rolled 23-25
Cold-Rolled 22
Hot-Rolled 20-22
Cold-Rolled 20
Hot-Rolled 18-20
Cold-Rolled 18
Hot-Rolled 16-18
Cold-Rolled 16
Hot-Rolled 14-16
Cold-Rolled 15
Hot-Rolled 12-14
Cold-Rolled 14


1.33

1.30

1.27

1.25

1.23

1.21


1.22

1.20

1.18

1.17

1.15

1.14

I-C-4

15 October 1998

 

ASTM Designation: A653/A653M-95

LGSI MEMBERS: ACI, Galvak, MBCI, McElroy, Metal Sales, NCI




SCOPE (After ASTM)




PRODUCT




GRADE


Fy
ksi
(min)


Fu
ksi
(min/max)

Percent
elongation
in 2 inches
(min)




Fu / Fy

This specification covers steel sheet, zinc coated (galvanized) or zinc-iron alloy coated (galvannealed) by the hot dip process in coils and cut lengths. Included are several grades based on yield strength in both structural quality (SQ) and high-strength low-alloy (HSLA). HSLA sheets are available as Type I or Type II. HSLA Type I is intended for applications where improved formability is required compared to SQ. HSLA Type II is intended for applications where improved formability is required to HSLA Type I. Products furnished under A653/A653M must conform to the latest revision of A924/A924M except as otherwise indicated in the specification.

Sheet

SQ

33
37
40
50 Class 1
50 Class 3

HSLA
Type I

50
60
70
80

HSLA
Type II

50
60
70
80



33
37
50
50





50
60
70
80




50
60
70
80



45
52
55
65
70




60
70
80
90




60
70
80
90



20
18
16
12
12




20
16
12
10




22
18
14
12



1.36
1.1
1.38
1.30
1.40




1.20
1.17
1.14
1.13




1.20
1.17
1.14
1.13

I-C-5

15 October 1998