Natural Frequency Improvement of a Suspended FGM Bridge

In this paper application of Functionally Graded Materials (FGMs) in suspension bridge structures for the purpose of vertical vibration improvement is investigated. Functionally graded materials are inhomogeneous composites, which are usually made from a mixture of metal and ceramic. Initially the classical equation of motion is modified based on the FGM model and natural frequencies of structure are extracted by Galerkin method. The material properties of structure vary continuously in the longitude direction according to power law form. In this regard, combination of materials is structured in such a way that the desired frequencies of the bridge are achieved by designing the proper power law of the FGM. Natural frequencies are evaluated to avoid any resonant due to environmental vibration. A bridge structure based on FGM made of steel and aluminum oxide is designed and improved for proper frequency. For the simple case of homogenous structures results are compared with those reported in the literature and very good agreements are obtained.