Effects of Axial Prestressing on Lateral Displacement of Steel Pipe Columns

The application of prestressing to concrete beams has been used to improve flexural strength. With the demand in producing tall, sleek structures (i.e. monopoles), stiffness must be improved, thus decreasing lateral displacement. This study will cover the effects of prestressing steel columns by determining the magnitude of lateral displacement for a given applied axial force. For this study, a 16mm threaded bar was used as the prestressing medium. In the first experiment, the threaded bar was subjected to varying levels of torques. The corresponding axial forces were measured by using spring balances. The aim for the first experiment is to provide a relationship between the applied torque and its corresponding prestressing force. The relationship observed was then used to determine the prestressing force for the second experiment. For the second experiment, a steel column was subjected to horizontal forces by mounting a motor on top of it. It was subjected to varying prestressing forces by using the threaded bar. Lateral displacements were then observed for each force applied. The initial experiment yielded an average ratio of 39.45 N axial force for every 1 N-m applied torque. This ratio was then used to determine the prestressing force applied in the second experiment. It was noted that after subjecting the column to prestressing force, the observed lateral displacement decreased. The results indicated that prestressing steel columns can reduce lateral displacement.