What are load factors and why are they used in structural design?

Load factors are multipliers applied to service loads to account for uncertainties in load magnitudes and combinations. Dead loads typically have lower factors (1.2-1.4) due to less uncertainty, while live loads have higher factors (1.6) due to variability. Load combinations ensure structures can safely resist the most critical loading scenarios. This approach is part of Load and Resistance Factor Design (LRFD) methodology.