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Hygrothermal Analysis of Composite Beams under Moving Loads



With the expanded use of composite materials in civil structures such as bridge decks, a moving-load analysis would simulate a truck moving over a composite bridge. Available results concerning moving-load analysis are in the form of deflections and dynamic load factors; a natural extension is the behavior of such a beam under a hygrothermal environment. In this research a finite element method employing h-p version finite elements is made and analyzed to determine the deflection distribution and the dynamic magnification factor of a composite beam under the action of a moving load. A computer code is written in MATLAB to accomplish this. Classical laminate plate theory (CLPT) and first order shear deformation theory (FSDT) are considered for the analysis of composite beams. A consistent formulation is used to reduce the composite plate theory to beams. The governing equations are obtained using Hamilton’s principle. Newmark’s time integration scheme is used to determine the dynamic response in the form of the displacement field of the beam. The maximum deflection obtained for the moving load case is compared with that of the static load to determine the dynamic magnification factor when subjected to a hygrothermal environment. Results are presented for a simply-supported beam subjected to a moving load that traverses the entire span of the composite beam. The displacement field and the magnification factors based on the CLPT is compared with that of FSDT. A parametric study is conducted by considering different fiber volume fractions and different laminates. The major conclusions are listed here. The ply orientation influences the dynamic behavior of a beam subjected to moving load. The dynamic magnification factors in dry and hygrothermal conditions for the laminates considered generally follow similar pattern. As the fiber volume fraction increases, the dynamic magnification factor generally decreases.

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