Table of Contents
Understanding load resistance in AISC steel design involves a series of calculations to ensure structural safety and compliance with standards. This article provides a step-by-step guide to perform these calculations accurately.
Determine Material Properties
The first step is to identify the material properties of the steel, including the yield strength (Fy) and ultimate strength (Fu). These values are obtained from the steel’s specifications and are essential for subsequent calculations.
Calculate Cross-Sectional Properties
Next, determine the cross-sectional properties such as the area (A), the moment of inertia (I), and the section modulus (S). These are typically provided in the steel section’s specifications or can be calculated based on the geometry.
Compute Load Resistance
The load resistance, often called the nominal strength (Pn), is calculated using the formula:
Pn = Fy × A
This provides the basic axial load capacity of the section. For bending resistance, the calculation involves the section modulus:
Mn = Fy × S
Apply Resistance Factors
The ultimate load resistance is obtained by applying the resistance factor (φ), which accounts for safety margins:
ΦPn = φ × Pn
Commonly, φ is taken as 0.9 for steel design. This adjusted value ensures the structure can safely withstand the applied loads.