A comprehensive explanation of structural load types and the international code references used to calculate any steel structure.
Dead Load and Live Load: The Starting Point of Any Calculation
Dead load is the weight of the structure itself plus everything permanently attached to it, such as cladding, roofing, and permanently suspended HVAC equipment, while live load is the variable weight resulting from use, such as moving equipment, people, and inventory inside the facility. These two loads form the foundation the rest of the calculation is built on, and structural codes set default minimum live load values based on the building's use type, which cannot be reduced even if actual use appears less intensive.
Wind Load and Why It Varies by Height and Geographic Location
The wind pressure acting on a structure increases with building height and with a more exposed site lacking natural barriers or neighboring buildings. Wind load calculation depends on the region's reference wind speed (per locally or internationally approved wind maps such as ASCE 7), an exposure factor, and the building's own geometric shape factor. For this reason, the same wind load value can't be used for two different projects even if they're similar in shape and height.
Seismic Loads and Their Calculation Methodology
In seismically active regions, special calculations are added per response spectrum methodology to ensure the structure can absorb ground motion without sudden collapse, which affects the type of connections used and the overall flexibility of the structure. Even in low seismic activity areas, a minimum level of these considerations is factored in per the adopted structural code, since omitting them entirely is an explicit violation of most modern building codes.
Reference International Codes: AISC 360 vs Eurocode 3
The American AISC 360 code adopts a Load and Resistance Factor Design (LRFD) or Allowable Stress Design (ASD) methodology, while the European Eurocode 3 adopts a unified limit-state methodology with different partial safety factors for each load type separately. The reference code choice is usually determined by the licensing authority's requirements in the project country, and the structural engineer and fabricator must remain committed to the same code throughout the design and fabrication stages to avoid any conflict in the safety factors used.
The Safety Factor and Why It Should Never Be Negotiated
The safety factor added on top of theoretically calculated loads covers uncertainty in estimating actual loads, variance between material properties and theoretical values, and minor fabrication or installation errors that can't be fully eliminated. Some cost-pressured projects attempt to shrink this factor to save on steel quantity, and this is a dangerous practice that most approved engineering codes refuse to permit, and any responsible structural engineer should reject it regardless of commercial pressure.
