Abstract

Beam bridges in mountainous and high-altitude transport corridors are frequently exposed to large diurnal temperature differences, intense solar radiation, low humidity, freeze–thaw action and repeated wetting–drying cycles. These coupled actions can accelerate concrete surface cracking and reduce the durability of prestressed concrete T-girder bridges, but field evidence linking crack morphology, crack depth, concrete cover and short-term environmental response remains limited. This study investigates a representative 40 m in-service prestressed concrete T-girder bridge on the Western Sichuan Plateau through field survey and four-month continuous monitoring. Crack location, length, width, depth and concrete cover thickness were measured, and representative crack-width responses to ambient temperature were analyzed. The results show that web cracks are dominated by reticular and irregular microcracks, bottom cracks are mainly longitudinal intermittent short cracks, and diaphragm cracks are concentrated near reticular zones and local corner discontinuities. The sunny side of the edge girder contained approximately 598 cracks, about 4.8 times the 123 cracks observed on the shaded side. Web and diaphragm crack widths were mainly 0–0.04 mm, while bottom-crack widths of 0–0.10 mm accounted for about 92.7%; most crack lengths were 2–20 cm. During monitoring, newly developed cracks accounted for about 6.0% of all recorded cracks, and only 3 of 721 existing cracks increased by 4–6 cm. Representative crack widths fluctuated by about 0.02 mm under −1 to 24 °C without sustained growth. Cracks wider than 0.20 mm generally exceeded the approximately 40 mm concrete cover. Such penetrating cracks should be prioritized in durability maintenance and long-term monitoring.

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