Which statement best describes the effects of creep and shrinkage on long-term concrete bridge performance?

• A. Creep reduces deflections under sustained loads; shrinkage thickens cracks.
• B. Creep increases deflections under sustained loads; shrinkage induces cracking and increases crack widths, reducing stiffness and durability over time.
• C. Creep and shrinkage both improve stiffness over time.
• D. Creep reduces crack widths; shrinkage reduces cracking risk.

Answer: (B)

Creep and shrinkage cause time-dependent changes in concrete that matter for long-term bridge performance. Under sustained loads, concrete slowly continues to deform, so deflections grow with time beyond the initial elastic response. At the same time, moisture loss leads to shrinkage, and when the concrete is restrained, tensile stresses develop that cause cracks to form; these cracks may open or widen as drying and loading continue. Wider crack openings reduce the effective stiffness of the member and provide easier pathways for water, chlorides, and other aggressive agents, which degrades durability. So creep tends to increase deflections under sustained loads, while shrinkage induces cracking and increases crack widths, leading to lower stiffness and reduced durability over time.