Shear force is one of the internal forces checked in structural beam and purlin design. Under Eurocode 3, shear resistance is calculated from the shear area of the section, the yield strength of the steel, and the partial safety factor for material strength. For purlins carrying rooftop solar PV loads, bending moment and deflection typically govern, but shear is verified as part of a complete assessment.
Shear forces are highest near the supports of a loaded beam. In purlin design for commercial portal frame roofs, shear checks focus on the fixing connection between purlin and rafter flange, and at mid-span splice connections. On-site structural surveys measure purlin section depths and fixing details to enable accurate shear capacity calculations.