Extended Monitoring of Earth Pressures Behind a 90 m Integral Bridge

Despite the popularity of integral bridges, long-term field data are required to better understand the soil strain ratcheting behavior that occurs with thermal cycles. This work presents over 6 years of field data collected from the Van Zylspruit Bridge, a 90-m-long integral bridge in South Africa. Sensors recording temperature, abutment movement, earth pressure, and soil water content were used to understand bridge behavior. Results show only a small increase in earth pressure over time, far less than that expected from physical modeling. One explanation for this may be the smaller-than-expected thermal movements recorded. Further possibilities were investigated through the small-scale modeling of a 1.5-m RC abutment, from which it was found that the starting position of the abutment and concrete drying shrinkage are both unlikely to contribute to the pressure buildup, while soil water content may play a part through the suctions generated. Based on these findings, the strain ratcheting of earth pressures in the field appears to be less severe than modeling efforts would suggest.