CEMP-E
TI 809-07
30 November 1998
Where:
φt = the tensile rupture resistance factor, equal to 0.75
Ant = the net area subjected to tension along the rupture plane being considered.
The shear and tensile rupture strength are based on the diagonal strap ultimate strength of the member in
the joint being evaluated. The maximum applied load on this joint is based on the yield strength of the
same member, Psy. This will be much less than the maximum estimated strap axial force, Psu. The
maximum force in the members is not critical, but rather the minimum ratio of Fu/Fy because the rupture
strength capacity is dependent on Fu and the maximum applied force is dependent on Fy. This guidance
requires that ASTM A653 material be used for the straps and the minimum Fu/Fy ratio for Grade 33 and
Grade 50 material is 1.36 and 1.303, respectively. These minimum ratios equate to yield, Fy and ultimate
strengths, Fu of Grade 33 and Grade 50 material, such that Fy33 = 228 MPa (33 ksi), Fu33 = 310 MPa (45
ksi), Fy50 = 345 MPa (50 ksi), and Fu50 = 448 MPa (65 ksi). Therefore the strap yield strength, Psy may be
defined simply based on the yield strength of these materials. This requirement is expressed as follows:
( V + T)n s ≥ Psy
(Eq 3-19)
Where:
Psy = Fynsbs t s
(Eq 3-20)
When the strap-to-column rupture strength is evaluated based on Equation 3-19, the resistance factors in
Equations 3-17 and 3-18 may be increased to 1.0, because of the ASTM minimum material requirement
on Fu/Fy stated above.
d. Welded Connection Design. Welded design shall follow AISI guidance (Section E2 Welded
Connections). This guidance covers connections of members in which the thinnest member is 0.18
4
inches or less. Arc welds shall be made in accordance with AWS D1.3 and its commentary. Resistance
welds shall be made in accordance with the procedures in AWS C1.1 or AWS C1.3.
Welded diagonal strap-to-column connections will require fillet welds (AISI E2.4). The welds at the sides
of the straps will be loaded in the longitudinal direction, and welds at the ends of the straps will be loaded
in the transverse direction. The weld thickness should be equal to the thickness of the strap material.
Ultimate failure of fillet welded joints has usually been found to occur by the tearing of the plate adjacent
to the weld. The higher strength of the weld material prevents weld shear failure, therefore, this guidance
5
is based on sheet tearing. Fillet weld design for diagonal strap-to-column connections is summarized in
Appendix C (Paragraph C16).
The fillet weld longitudinal and transverse shear strengths are based on the ultimate strength of the
thinner member (normally diagonal strap) of the joint. The maximum applied load on this joint is based on
the yield strength of the same member, Psy. The maximum force in the members is not critical, but rather
the minimum ratio of Fu/Fy because the rupture strength capacity is dependent on Fu and the maximum
applied force is dependent on Fy. This guidance requires that ASTM A653 material be used for the straps
and the minimum Fu/Fy ratio for Grade 33 and Grade 50 material is 1.36 and 1.306, respectively.
Therefore, the strap yield strength, Psy shall be defined simply based on the yield strength of these
materials. This requirement is expressed as follows:
3
See AISI Dimensions and Properties for use with the 1996 AISI Cold-Formed Steel Specifications, ASTM Specifications for
Referenced Steels.
4
American Welding Society (1989), Structural Welding Code - Sheet Steel, ANSI/AWS D1.3-89, Miami, FL 1989.
5
AISI Commentary, E2.4.
6
See AISI Dimensions and Properties for use with the 1996 AISI Cold-Formed Steel Specifications, ASTM Specifications for
Referenced Steels.
3-11
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