Determining the Axial Force in Metallic Rods

A new method to determine the tensile axial force in metallic rods is presented. The method consists of an analytical identification procedure, based on the experimental measurement of the fundamental vibration frequency, and the vertical displacement caused by a concentrated load. These measurements are carried out at the middle of the tested rods. The rods are modelled as tie-beams with two identical elastic rotational springs at the extremities, which schematise the actual constraint level at the end-sections. The springs' rigidity, K, along with the axial force, P, represent the two unknowns of the parametric identification procedure. Knowledge of the above experimental quantities permits K and P to be evaluated, using the solving equations of the analytical procedure. Laboratory tests proved the method's reliability and indicated its most appropriate use. The method was successfully applied to the analysis of the rod systems of many historical Italian buildings. A synthesis of these studies is reported in the paper.