Code-Checker AI Agent

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Review this beam design calculation for code compliance:

BEAM DESIGN CALCULATION SUBMISSION:
Project: Office Building Renovation
Location: Chicago, IL
Code: IBC 2021 / ASCE 7-16

Beam: W16×50 (A992 steel, Fy = 50 ksi)
Span: 28 feet (simply supported)
Loading:
- Dead Load: 0.8 kips/ft
- Live Load: 1.2 kips/ft

Load Combination (LRFD):
w_u = 1.2D + 1.6L = 1.2(0.8) + 1.6(1.2) = 2.88 k/ft

Maximum Moment:
M_u = w_u × L² / 8 = 2.88 × 28² / 8 = 282.2 kip-ft

Section Check:
W16×50: Z_x = 92.0 in³
φM_n = 0.9 × 50 × 92.0 / 12 = 345 kip-ft > 282.2 kip-ft ✓ OK

CONCLUSION: Beam is adequate.

Please validate this calculation for code compliance and mathematical accuracy.

CODE-CHECKER AGENT VALIDATION REPORT

🔴 CRITICAL ERRORS FOUND: 2
🟡 WARNINGS: 1
🟢 COMPLIANT ITEMS: 3

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SECTION 1: CODE COMPLIANCE REVIEW

1.1 APPLICABLE CODES ✓ CORRECT
   ✓ IBC 2021 correctly references ASCE 7-16
   ✓ Steel design per AISC 360-16 (implied)
   ✓ LRFD method appropriate

1.2 LOAD COMBINATIONS ❌ ERROR
   Code Reference: ASCE 7-16 Table 2.3-1

   Issue: Missing load combinations!
   You only checked: 1.2D + 1.6L

   Required combinations per ASCE 7-16:
   - Combo 2: 1.2D + 1.6L + 0.5Lr  (you used this)
   - Combo 3: 1.2D + 1.6Lr + L (if roof loads present)
   - Combo 5: 1.4D (controls for deflection check)

   ⚠️ Recommendation: Verify no roof loads tributary to beam.
   If office floor beam only, 1.2D + 1.6L is likely governing.

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SECTION 2: CALCULATION VERIFICATION

2.1 MOMENT CALCULATION ✓ CORRECT
   Formula: M = wL²/8 (simply supported, uniform load)
   M_u = 2.88 × 28² / 8 = 282.24 kip-ft ✓

2.2 FLEXURAL CAPACITY ❌ CRITICAL ERROR
   Code Reference: AISC 360-16 Chapter F

   Your calculation:
   φM_n = 0.9 × Fy × Zx / 12 = 345 kip-ft

   Issues:
   ❌ Missing lateral-torsional buckling check!
   ❌ Assumed plastic section modulus applies
   ❌ Did not verify Lb ≤ Lp

   Correct approach (AISC 360-16 §F2):
   1. Determine unbraced length (Lb)
   2. Calculate Lp and Lr
   3. Check if Lb ≤ Lp (compact, use Zx)
      OR if Lp < Lb ≤ Lr (inelastic LTB)
      OR if Lb > Lr (elastic LTB)

   For W16×50 (AISC Steel Manual):
   - Lp = 5.63 ft (compact limit)
   - Lr = 16.9 ft (inelastic limit)

   **CRITICAL:** If Lb = 28 ft (full span unbraced):
   Lb > Lr → Elastic LTB controls!

   φM_n = φCb[π²EIy/(Lb)² × √(GJ + (πE/Lb)²Cw)]^0.5
   Estimated φM_n ≈ 180 kip-ft (if Cb = 1.0)

   ❌ BEAM FAILS! (180 < 282)

   Solution: Add lateral bracing at mid-span
   OR upsize to W18×60

2.3 SHEAR CHECK ⚠️ MISSING
   AISC 360-16 §G requires shear check
   V_u = w_u × L/2 = 2.88 × 14 = 40.3 kips

   W16×50 shear capacity:
   φV_n ≈ 175 kips (typically OK, but must verify)

2.4 DEFLECTION CHECK ⚠️ MISSING
   IBC 2021 Table 1604.3: L/360 for floors

   Δ_L = 5wL⁴/(384EI)
   Must verify Δ < L/360 = 28×12/360 = 0.93"

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FINAL VERDICT:

❌ CALCULATION REJECTED - CRITICAL ERRORS

Required Actions:
1. ⚠️ IMMEDIATELY check lateral bracing spacing
2. ❌ Recalculate flexural capacity with LTB
3. ⚠️ Add shear and deflection checks
4. ✓ Verify no missing load cases

Likelihood: Current beam is UNDERSIZED if unbraced length = 28 ft.

Recommendation: Provide lateral bracing at L/3 points (9.3 ft spacing) OR upsize to W18×60 or W21×57.

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Code-Checker Agent v2.0
Validation Date: 2026-01-09
Confidence Level: 95%

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