Round Wood Post Design per NDS 2024 §3.7.3

Summary: Design a round timber post using equivalent square cross-section per NDS 2024 §3.7.3. Free wood beam calculator NDS: equivalent b=d=√(π×D²/4) for…

Overview

Design a round timber post using equivalent square cross-section per NDS 2024 §3.7.3. Free wood beam calculator NDS: equivalent b=d=√(π×D²/4) for buckling check.

Problem statement

A 8 in. diameter round post, 10 ft tall, pinned both ends. Load 5000 lb D+L. Southern Pine. NDS 2024 §3.7.3: round columns designed as equivalent square (same area). Common for timber frame, poles.

Workflow in StructSuite

StructSuite: select Sawn Lumber (or appropriate product), round cross-section. Enter diameter 8 in. Equivalent square b=d=√(π×8²/4)≈7.09 in. NDS 2024 §3.7.3. Axial capacity per Eq 3.7-1. 8 in. round ≈ 7×7 equivalent; capacity similar to 6×6 sawn at same height.

Design considerations (excerpt)

NDS §3.7.3: equivalent square b=d=√(πD²/4). 8 in. round → 7.09 in. square. Le/d uses equivalent d. Round has same area as square; buckling uses √A. Tapered poles: use avg or conservative D. 6–12 in. dia common.

Round posts: Southern Pine, DF peeler. Design values from NDS. PT for ground contact. Poles (utility, lighting): ASTM D3200, D2899. Round timber vs sawn: different grading; verify product.

5 kip concentric. Eccentric (cantilever post, lateral): beam-column. Wind on sign, canopy: adds moment. CD=1.6 for W, E. Self-weight for 10+ ft poles.

8 in. round ≈ 7×7 square capacity. At 10 ft, ~6–8 kip typical. Bearing uses full area πD²/4. Pitfall: Le/d with D instead of √(πD²/4)…

Related terms

• StructSuite
• structural engineering
• design example
• wood column
• NDS 2024
• round post

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