Question 9.2: A 1/2 -in by 2-in rectangular-cross-section 1015 bar carries...

a) From Table 9–6, allowable force per unit length for a \frac {3}{8} -in E70 electrode metal is 5.57 kip/in of weldment; thus

F = 5.57l = 5.57(4) = 22.28 kip

Since 22.28 > 16.5 kip, weld metal strength is satisfactory.

Table 9–6    Allowable Steady Loads and Minimum Fillet Weld Sizes

Schedule B: Minimum Fillet Weld Size, h	Schedule A: Allowable Load for Various Sizes of Fillet Welds
Not to exceed the thickness of the thinner part. *Minimum size for bridge application does not go below \frac {3}{16} in. †For minimum fillet weld size, schedule does not go above \frac {3}{16} in fillet weld for every \frac {3}{4} in material.	Strength Level of Weld Metal (EXX)
	60*	110*	100	90*	80	70*	60*
	Allowable shear stress on throat, ksi (1000 psi) of fillet weld or partial penetration groove weld
	36.0	33.0	30.0	27.0	24.0	21.0	18.0	τ =
	llowable Unit Force on Fillet Weld, kip/linear in
	25.45h	23.33h	21.21h	19.09h	16.97h	14.85h	12.73h	† f =
	able Unit Force for Various Sizes of Fillet Welds							Leg  Size h, in
	25.45	23.33	21..21	19.09	16.97	14.85	12.73	1
	22.27	20.41	18.57	16.70	14.85	12.99	11.14	7/8
	19.09	17.50	15.92	14.32	12.73	11.14	9.55	3/4
	15.91	14.58	13.27	11.93	10.61	9.28	7.96	5/8
	12.73	11.67	10.61	9.54	8.48	7.42	6.37	1/2
	11.14	10.21	9.28	8.35	7.42	6.50	5.57	7/16
	9.54	8.75	7.95	7.16	6.36	5.57	4.77	3/8
	7.95	7.29	6.63	5.97	5.30	4.64	3.98	5/16
	6.36	5.83	5.30	4.77	4.24	3.71	3.18	1/4
	4.77	4.38	3.98	3.58	3.18	2.78	2.39	3/16
	3.18	2.92	2.65	2.39	2.12	1.86	1.59	1/8
	1.59	1.46	1.33	1.19	1.06	0.930	0.795	1/16

Source: From Omer W. Blodgett (ed.), Stress Allowables Affect Weldment Design, D412, The James F. Lincoln Arc Welding Foundation, Cleveland, May 1991, p. 3. Reprinted by permission of Lincoln Electric Company.

(b) Check shear in attachment adjacent to the welds. From Table 9–4 and Table A–20, from which S_{y} = 27.5 kpsi, the allowable attachment shear stress is

τ_{all} = 0.4S_{y} = 0.4(27.5) = 11  kpsi

Table A–20   Deterministic ASTM Minimum Tensile and Yield Strengths for Some Hot-Rolled (HR) and Cold-Drawn (CD) Steels [The strengths listed are estimated ASTM minimum values in the size range 18 to 32 mm ( \frac {3}{4}  to 1\frac {1}{4}in). These strengths are suitable for use with the design factor defined in Sec. 1–10, provided the materials conform to ASTM A6 or A568 requirements or are required in the purchase specifications. Remember that a numbering system is not a specification.] Source: 1986 SAE Handbook, p. 2.15

Table 9–4   Stresses Permitted by the AISC Code for Weld Metal

*The factor of safety n has been computed by using the distortion-energy theory.
†Shear stress on base metal should not exceed 0.40Sy of base metal.

The shear stress τ on the base metal adjacent to the weld is

τ =\frac {F}{2hl} =\frac {16.5}{2(0.375)2} = 11  kpsi

Since τ_{all} ≥ τ , the attachment is satisfactory near the weld beads. The tensile stress in he shank of the attachment σ is

σ =\frac {F}{tl }=\frac {16.5}{(1/2)2} = 16.5  kpsi

The allowable tensile stress σ_{all}, from Table 9–4, is 0.6S_{y} and, with welding code safety level preserved,

σ_{all} = 0.6S_{y} = 0.6(27.5) = 16.5  kpsi

Since σ_{all}≥ σ , the shank tensile stress is satisfactory.