DYNAMIC BEHAVIOR OF MULTISPAN BEAMS UNDER MOVING LOADS

In this paper, an exact dynamic stiffness element under the frame work of finite element approximation is presented to study the dynamic res ponse of multi-span structures under a convoy of moving loads. A dynam ic model coupled with a FFT algorithm is developed. The model is highl y efficient for calculating the response of bridges under multiaxle mo ving forces. All the vibration frequencies and mode shapes of the beam -structure may be calculated exactly using the Wittrick and Williams a lgorithm. Examples show that with only one element per span, exact fre quencies and modes could be obtained. Some results on the dynamic ampl ification factor are presented also as a function of the speed of the moving loads. (C) 1997 Academic Press Limited.