30 November 1998
7. DIAGONAL STRAP DESIGN. The diagonal straps are designed to resist the seismic story shears, Vx
given in Equation C-27 that has been increased by the additional shear force due to torsion (Qsi in
Equation 3.1). The shear panels shall be configured and diagonal straps sized so that the lateral shear
panel design strength, φt Qsy satisfies the following equation (see Equation C-34 in Appendix C).
= φ t ∑ n sb s t sFsy
≥ Vx + Q si
φ t Q sy
φt = the resistance factor for tensile members (0.95),
n = the number of shear panels in the building frame for which the shear forces Vx and Qsi are
ns = the number of diagonal straps (panel faces with straps) in an individual panel.
Fsy = the design yield strength of the strap.
The number of shear panels, panel width, height, and strap size and strength shall be designed according
to Equation 3-4 to meet minimum lateral yield capacity. All diagonal strap material must be ASTM A653
steel. Diagonal straps may not use re-rolled steel, because the re-rolling strain hardens the material,
increasing material strength variability and reducing elongation (see USACERL Technical Report,
Chapter 4 for a discussion of this concern).
8. COLUMN DESIGN Structural Tubing or Built-up from Studs. The columns of the Panel A
configuration are built-up with cold-formed steel studs. These studs must be oriented to form a closed
cross-section as shown on the Test Panel A1 and A2 drawings in Appendix B. Individual studs must be
welded to each other with a weld thickness equal to the thickness of the studs. The welds are
intermittent, with a length and spacing that will ensure composite behavior of the column.
Structural tubing column design (Panel D configuration - Drawing D1 in Appendix B) follows the same
procedure, but consists of a single member which is a closed section by itself. The equations in this
guidance are used such that the number of studs making up this column is one.
a. Column Applied Loads. Loads applied to the columns are defined based on Equation C-17 (TI
809-04, Equations 4-2 and 4-6), where the effects of gravity load and seismic forces are additive and
diagonal strap overstrength is accounted for. Only that portion of gravity loads applied to the tributary
area of the shear panel columns are included in the design of these columns. However, the full horizontal
seismic force, Ω0QE applied to the shear panel and resisted by the diagonal straps, will add a vertical
component to the columns, increasing axial load. This horizontal load is based on the actual designed
area of the diagonal straps as defined in Equation C-16. The total column axial load at the maximum
ultimate stress in the diagonal straps, Pvumax is:
+ Fsu max n s b s t s
GLmax = the maximum gravity load per shear panel, i.e., from (1.2 + 0.2SDS)D + 0.5L + 0.2 S, in
Fsumax = the maximum estimated ultimate stress in the diagonal straps, which equals to 1.5 Fsu for
ASTM A653 Grade 33 steel (Fsu = 310 MPa and 45 ksi) and 1.25 Fsu of Grade 50 steel
(Fsu = 448 MPa and 65 ksi).
b. Column Axial Capacity. Column capacity is determined based on AISI provisions. The design
strength, P shall be determined based on the AISI guidance (Section C4 Concentrically Loaded