Which type of cracking is primarily influenced by repeated loading and stress concentration?

• A. Longitudinal cracking
• B. Alligator cracking
• C. Transverse cracking
• D. Fatigue cracking

Answer: (B)

The type of cracking primarily influenced by repeated loading and stress concentration is fatigue cracking. Fatigue cracking occurs in materials subjected to cyclic loading, where the stress intensity at certain points can exceed the material’s ability to withstand it, leading to the gradual formation of cracks. This is particularly relevant in scenarios like roadways and pavement where vehicles repeatedly pass over the same areas, leading to localized stress that accumulates over time.

Longitudinal cracking typically occurs due to thermal expansion and contraction or shrinkage, which is not directly related to repeated loads. Transverse cracking is more associated with temperature fluctuations and resulting stresses rather than repeated loading scenarios. Alligator cracking, while it may appear in areas under high traffic, is more of a surface distress due to a combination of factors including inadequate support and is not defined primarily by fatigue mechanisms.

Understanding fatigue cracking is vital in transportation engineering, as it directly impacts the performance and longevity of pavement structures. Recognizing the conditions that lead to this type of cracking can aid in better design and maintenance practices.