Which load combination represents an owner-specified permit load model with less uncertainty than random traffic?

• A. Strength I
• B. Strength II
• C. Strength III
• D. Strength IV

Answer: (B)

When engineers evaluate loads on a bridge, there are different load models to represent how traffic might act on the structure. An owner-specified permit load model is used when a permit allows a known, overweight vehicle configuration to operate, so the load becomes deterministic rather than a broad, probabilistic mix of traffic. That fixed, defined load reduces uncertainty compared with random traffic, which can vary in weight, number of axles, and spacing.

Strength II is the category that represents this owner-specified permit load model. It’s chosen because the permit defines the exact load scenario the bridge must withstand, giving a predictable demand. The other strengths are designed for different traffic representations that involve more variability or broader assumptions, which carry more uncertainty compared to a defined permit load.