An elevated jogging track is supported at intervals by a wood beam AB (L = 7.5 ft) which is pinned at A and supported by steel rod BC and a steel washer at B. Both the rod (dBC = 3/16 in.) and the washer (dB = 1.0 in.) were designed using a rod tension force of TBC = 425 lb. The rod was sized using a factor of safety of 3 against reaching the ultimate stress σu = 60 ksi. An allowable bearing stress σba = 565 psi was used to size the washer at B.
Now, a small platform HF is to be suspended below a section of the elevated track to support some mechanical and electrical equipment. The equipment load is uniform load q = 50 lb/ft and concentrated load WE = 175 lb at mid-span of beam HF. The plan is to drill a hole through beam AB at D and install the same rod (dBC) and washer (dB) at both D and F to support beam HF.
(a) Use σu and σba to check the proposed design for rod DF and washer dF; are they acceptable?
(b) Also re-check the normal tensile stress in rod BC and bearing stress at B; if either is inadequate under the additional load from platform HF, redesign them to meet the original design criteria.

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Original structure Steel rod, BC 425 lb. 16 L-1.5 ft 25 Wood beam supporting track D B Washeri New steel rod, d-16in- WE 175 IIb 50 lb/ft 25 New beam to support equipment F Washer, dp same at D above)