Multiple laboratory characterization methods to identify the D-Load of reinforced concrete pipes based on three edge bearing tests

The indirect design method for concrete pipes, which estimates the bearing capacity of concrete pipes in a buried environment based on the D-load determined from a three-edge bearing test (TEBT), is a common method for designing concrete pipes. D-load is determined by the load corresponding to the first 3-mm crack, which has been used from the 1930s until today. To explore the potential of modern laboratory techniques as an alternative to the traditional vision method. This study discusses the application and cost-effectiveness of several technologies for detecting D-load, including strain gauges, displacement sensors, acoustic emission, digital image correlation, and infrared thermography, based on TEBT on full-scale double-cage reinforced concrete pipes with internal diameters of 1000, 1500, and 2000 mm. The consistency between D-load values obtained by these approaches along with the predicted value by Heger’s model is compared with the D0.3_visual determined by conventional visual observation in terms of the developed relative reliability. It is found that the method based on acoustic emission techniques is more consistent with the D0.3_visual than others, but is costly and time-consuming. Also, De, identified by the load corresponding to the end of the elastic phase of the force–time curve, is a reliable alternative and cost-effective method. This study will provide new insights into the aspect of performance design and evaluation for concrete pipes. •Modern laboratory methods are used to attempt to identify the D-Load of concrete pipes.•The D-load values obtained by the new methods were compared with that from the traditional method.•The cost-effectiveness and reliability of the new methods are discussed.