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BASE METAL STRENGTH

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In a recent post it was stated that incorrect values were tabulated for the
minimum web thickness for fillet welds A in Table 9-4 of LRFD Volume II.
These values are derived from the shear yielding strength of the base
metal, as indicated on pages 9-15 and 9-16, using equation (J5-3) which
specifies
     phi * Rn  = 0.90 * 0.6 * Fy * t

However, Salmon and Johnson in "Steel Structures" 4th Edition on pages
225-227 and Figures 5.14.1 and 5.14.2 evaluate the strength of the shear
plane through the base metal using the shear rupture strength given by
equation (J4-1) which specifies:
     phi * Rn  = 0.75 * 0.6 * Fu * t

For A36 material equation (J4-1) gives a 27 % greater value for the base
material strength than equation (J5-3) and for A572 Grade 50 material
equation (J4-1) gives a 8 % greater value.  For comparison, the minimum web
thickness values given in Table III of ASD Part 4 are based on a 13 %
greater base material strength than those in Table 9-4 of LRFD Volume II.

In the section titled "Base metal design strength" on page 8-129 of LRFD
Volume II no mention is made of shear strength of the base metal in fillet
welded joints.  Table J2.5 LRFD Volume I also lacks details for shear
strength of the base metal in fillet welded joints.

Is there any consensus on which approach should be adopted?

Alan Williams