Eccentric Fillet Weld Group (Elastic Method)
Line polar moment, direct shear, torsional components, the resultant unit force at the critical corner.
Example
You enter
- In-plane load P (lb) 12000
- Eccentricity from centroid (in) 6
- Length of each vertical weld (in) 10
- Separation between welds (in) 4
- Allowable per 1/16 in leg (lb/in) 928
You get
- Line polar moment J 246.7 in3
- Direct shear 600 lb/in
- Resultant at critical corner 1879 lb/in
- Required fillet leg 3
Checked against published worked examples from: AISC 360 / Steel Construction Manual Part 8.
Details, formula, and sources
ScopeLine polar moment, direct shear, torsional components, the resultant unit force at the critical corner, and the required fillet leg for two vertical welds under in-plane eccentric load by the AISC elastic (vector) method. The conservative elastic method, a screen; the engineer of record governs.
Formula or tableTwo vertical welds length D, separation B: L_w = 2D; Ix = D3/6; Iy = D B2/2; J = Ix + Iy; direct shear f_d = P/L_w; torque T = P x e; f_tx = T(D/2)/J; f_ty = T(B/2)/J; resultant f_r = sqrt(f_tx2 + (f_d + f_ty)2); required leg (sixteenths) = ceil(f_r / allowable per 1/16 in).
Source and editionEccentrically loaded fillet weld group, elastic (vector) method, per AISC 360 and the AISC Steel Construction Manual Part 8, by name.
Free accessFirst-principles weld-line mechanics (the elastic method); the load, eccentricity, weld geometry, and the E70 allowable (about 928 lb/in per 1/16 in, ASD) are user-supplied.
What governsEstimate. Engineer of record governs the design and acceptance. Verify against the project structural drawings and the manufacturer's published capacity / chart.
API field namesload_lb, ecc_in, weld_len_in, separation_in, allow_per_16, polar_moment_in3, direct_shear_lb_in, resultant_lb_in, req_leg_16
- Fillet allowable E70 ASD about 928 lb/in per 1/16 in of leg; editableAISC 360 §J2
- Method elastic (vector) method, conservative vs instantaneous-centerAISC Manual Part 8