Understanding Load Calculations
Proper concrete load calculations ensure structural safety and code compliance.
- Dead Loads Concrete: 150 pcf. Steel: 490 pcf. CMU: 85-135 pcf. Roofing: 5-15 psf. MEP: 5-10 psf. Ceiling: 2-5 psf. Partitions: 15-20 psf.
- Live Loads Office: 50-100 psf. Residential: 40-60 psf. Storage: 125-250 psf. Retail: 75-100 psf. Assembly: 100 psf. Corridors: 80-100 psf.
- Environmental Loads Snow: 20-40 psf. Wind: 90-140 mph basic. Seismic: zone dependent. Rain: 20 psf ponding. Temperature: ±30°F. Soil: 30-60 pcf active.
- Load Combinations 1.4D. 1.2D+1.6L. 1.2D+1.0E+1.0L. 1.2D+1.0W+0.5L. ASD factors: 0.6-0.9. Importance factor: 1.0-1.5. Redundancy: ρ=1.0-1.3.
Design Considerations
Structural Analysis
Safety factor: 1.5-2.0. Deflection: L/360-L/240. Drift: H/400. Overturning: 1.5 min. Sliding: 1.5 min. P-delta effects: >1.1.
Material Properties
f'c: 3000-5000 psi. fy: 60,000 psi. E concrete: 57,000√f'c. Poisson's ratio: 0.2. Thermal expansion: 5.5×10⁻⁶/°F. Creep factor: 2.0.
Special Requirements
Exposure category: B-D. Risk category: I-IV. Special inspection: >2000 psi. Load testing: >2×DL. Monitoring: settlement >1". Impact: 1.3×LL.
Documentation
Calculations sealed. Shop drawings: 1/4"=1'-0". As-builts required. Load posting: visible. Test reports: 7 and 28 day. Inspection logs daily.