In recent years

the construction of electricity transmission systems that span from west to east China has been planned. Thus

the construction of foundations for overhead transmission towers is inevitable. Uplift loading often controls the design of transmission tower foundations. Belled piers have been used in loess area to satisfy the requirements for uplift resistance. At two places in Gansu province

twelve full-scale tests were carried out to investigate the uplift behavior of belled piers in loess. Based on the measured load-displacement curves

the ultimate bearing capacities and displacements were interpreted using the Chin hyperbolic model

the slope tangent

double line intersection and L1-L2 methods. A mean normalized load-displacement curve was obtained based on the statistical data of measured results. By fitting measured load-displacement data using a normalized hyperbolic model

normalized hyperbolic load-displacement curves were suggested at different confidence levels. The results show that the slope tangent and Chin methods represent the lower and upper bounds

respectively. The L1-L2 method is appropriate for interpreting the failure bearing capacity. Normalizing the measured load-displacement curves reduces the scatter in the curves. The mean curve more closely represents the actual test data. However

the field tests show a substantially stiffer load-displacement response than the curve at the 95% confidence limit.