Long-term strain behavior of in-service cable-stayed bridges under temperature variations

Long-term structural health monitoring of bridges is very important to ensure their serviceability and structural integrity. Strain monitoring data is better suited to characterize the local deficiencies and damage in bridges than global responses. Strain behaviors of structural elements of in-service long-span cable-stayed bridges under operational conditions are highly sensitive to temperature effects. The present study aims to investigate the effects of air temperature on the yearly and daily strain behaviors of deck, pylon and cable elements of in-service cable-stayed bridges under normal operational conditions. The new Kömürhan cable-stayed bridge constructed in Turkey in 2021 has been selected as an application. To capture seasonal and daily strain trends of the bridge structural elements, 1-year monitoring strain and temperature data recorded on the bridge have been processed and evaluated in detail. The yearly data comprises the data recorded from January to December 2021. The daily data includes data for the day of July 3, when the maximum temperature was recorded. While daily and yearly strain responses of the main span steel deck are dominantly affected by air temperature according to traffic and wind effects, yearly strain responses of the concrete pylon do not show a strong correlation with air temperature. The yearly variations in cable forces of the main span deck and back span anchorage block generally increase with increasing air temperature. It can be generally stated that thermal effects are the main factor on the daily and yearly structural strain behaviors of in-service cable-stayed bridges under normal operational conditions.