Identification of axial forces in beam members by local vibration measurements

A method is presented to estimate the axial force in a bar which is part of a built-up structure. The estimation is based on the modal characteristics of the bar or, alternatively, on its operational deflection shape, as determined from a local vibration test. Timoshenko beam theory is assumed and, in addition, the rotational inertia of the bar and the mass of the sensors are accounted for. A major advantage of the proposed method is its generality. When data from five or more sensors along the length of the bar are available, no information on the connection of the bar to the remainder of the structure is required. The method can therefore be used for any beam or truss element. The method is first verified numerically using finite element simulations. Finally, a set of laboratory experiments is performed in order to ascertain the applicability and accuracy of the proposed method.