For a single rolled section used as a tension member (with holes), by how much should the gross area typically exceed the required net area to account for reductions at holes and stress concentrations?

Introduction / Context:When designing a tension member, the presence of holes reduces the effective section and introduces stress concentration. Practical guidelines recommend a margin of gross area over the required net area to maintain adequate capacity and ductility.

Given Data / Assumptions:

• Single rolled section (e.g., single angle or plate) in tension.
• Presence of standard bolt/rivet holes.
• Allowable stresses as per conventional design practice.

Concept / Approach:Net area A_net equals gross area minus deductions for holes (and plus stagger correction where applicable). To avoid overly thin members and to limit localized stresses around holes, a practical rule is to keep the gross area about 20% to 30% larger than the minimum required net area.

Step-by-Step Solution:

Verification / Alternative check:Check block shear and connection efficiency; confirm that the fracture path governs and that yielding precedes fracture in a ductile design.

Why Other Options Are Wrong:Margins of 30%–70% are overly conservative for typical practice and lead to uneconomical members without commensurate benefit.

Common Pitfalls:Forgetting to add stagger restoration; using nominal hole size instead of standard (larger) hole diameter; ignoring reduced net section near the connection.

Final Answer:20% to 30% in excess of the net area