1. To reduce calculation effort in design
2. Because each type of failure has different consequences and uncertainty
3. To eliminate the need for load combinations
4. To increase structural redundancy

Explanation

Explanation:

Collapse, excessive deformation, and fatigue cracking represent fundamentally different behaviours with different consequences and statistical uncertainties. CHBDC assigns separate load and resistance factors so that each failure mode achieves an appropriate reliability level. A single global safety factor would either:

• Over-design serviceability and fatigue, or
• Under-protect against collapse.

Separating limit states enables consistent reliability while maintaining structural efficiency.

Learning Resources:

• CSA S6:19, Clause 1.4.2.1 – Limit States Design Philosophy