Failure experiment and calculation model for prestressed concrete cylinder pipe under three-edge bearing test using distributed fiber optic sensors

A prestressed concrete cylinder pipe (PCCP) with quality defects or being subjected to overloads can crack in the inner concrete core, thereby the internal water acting directly on the steel cylinder and further weakening the bearing capacity of the pipe. This study aims to explore calculation methods of when and after a PCCP cracks through the comparative analysis between the test results measured from the three-edge bearing test (TEBT) and the calculation results through the improved procedures based on ANSI/AWWA C304. To this end, the full strain distribution around the circumference of the first pipe is measured until failure by distributed optical fiber sensors. The thrust and moment coefficients of loads under the TEBT are derived, and strains are solved considering the stress–strain relationships of the constituent materials. The first pipe cracks in the inner core at the crown and invert as the load reaches 280 kN/m, but the second pipe with the same parameters does not crack when the load arrives at 360 kN/m. The measured strains reveal that the inner side at the crown and invert and the outer side at the springline are subjected to tension. Before appearing the cracks in the inner concrete core, the calculated results are in good agreement with experimentally observed data. After cracking of the inner concrete core, both the vertical displacement at the crown and the fluctuation amplitude of test strains begin to accelerate. The results calculated by considering two empirical assumptions can reflect the trend of the test results. The proposed comparative analysis approach provides the cracking test load that meets the serviceability limit-state design criterion for quality inspection and helps designers a better understanding of design assumptions and parameters.