Cantilever Rack Arm Weld Joint FEA: Gusset Design to IS 800 and AISC ASD

A storage rack manufacturer was building cantilever racks for long and bulky goods, the kind of rack where I-section arms stick out from a central column with nothing at the free end. Each arm is welded to an end plate, and the end plate is bolted to the column. The maker wanted to rate the arm for a heavier load and needed to know whether the welded joint at the root of the arm could take it.

Shirsh Technosolutions carried out cantilever rack arm FEA in ANSYS Mechanical. The study looked at the weld, the end plate and the arm itself, first without any stiffener and then with a gusset under the arm, and checked every case against the working stress design method of IS 800:2007 and AISC ASD.

Rib placement study first. Before the weld check, Shirsh compared the arm with no rib, with a rib on the upper side and with a rib on the lower side, looking at how much the arm tip deflects in each layout. The rib on the upper side gave the stiffest arm. The lower rib deflected noticeably more and was not recommended for stiffness.

Detailed joint model. For the weld study, a 3D model of the column, end plates, bolts, gusset and I-section arms was built from the client's drawings. Shell and solid elements were used with contact between bolted parts, the weld region was modelled as its own body, and the column base was fully fixed. Self-weight was applied from material density and the rated load was applied vertically on each arm.

Allowables from the material certificates. Allowable stresses for the end plate and gusset, the I-section and the weld metal were taken from the supplier test certificates using the working stress approach of IS 800:2007 and AISC ASD, with separate allowables for normal and shear stress.

Three cases, checked part by part. The joint was solved without a gusset at the standard rating, and with a gusset at the standard and the higher rating. For each case von Mises stress and the shear stress in all three planes were read at the weld, the end plate and the arm, and compared with the allowables.

A gusset that works at both ratings. The plain joint was well over the weld and end plate limits, so a gusset was clearly needed. When the client tried a smaller gusset, the model showed the gusset and its weld were still overstressed. A longer gusset was then sized, and its thickness was set so that the weld, end plate and arm stayed within the allowables at the higher rating too. The client got one gusset detail for both arm ratings.

Common questions

Why does a cantilever rack arm need a weld joint FEA? The arm is fixed only at the column, so the highest bending moment sits right at the arm-to-end-plate weld. FEA shows how that moment spreads through the weld, the plate and the bolts, which a simple connection calculation cannot show, and it tells you whether a gusset is needed.

Is a gusset better on top of or below a cantilever arm? It depends on what you are trying to control. In this study a rib on the upper side gave the lowest arm deflection, while a gusset below the arm was the practical choice to relieve the weld and end plate. Both were checked in the model before the detail was fixed.