DYNAMIC MODELING OF CONCRETE RAILWAY SLEEPERS

A simple dynamic model of monobloc concrete railway sleepers of non-uniform cross-section has been derived by reference to experimental data for about the first six resonance frequencies of 12 different types of sleeper. It is demonstrated that a sleeper is well modelled as a uniform Timoshenko beam the effective flexural rigidity, cross-sectional area and radius of gyration of which are found from the sleeper's mass and length, and from the cross-sectional geometry of the railseat and centre. An effective Young's modulus for all of the sleepers of 52.4GPa was calculated for the prestressed concrete from measured resonant frequencies for four prismatic sleepers of different lengths. An effective density of 2750kg/m(3) was also calculated from these sleepers. Data for the uniform sleepers in particular indicate that it may be unwise to expect any model to predict natural frequencies to better than a few percent. (C) 1995 Academic Press Limited