Fiber reinforced polymeric (FRP) composites are beginning to find applications in constructing infrastructures such as bridges, railroads, etc. Composites may potentially be more durable replacements for steel and concrete, but their experience in these applications is minimal. Also, composite decks are susceptible to change in environmental conditions. Thus, the study of the behavior of composite material in elevated environmental conditions is necessary. This thesis is aimed at development and validation of Finite element methods used to analyze Fiber reinforced polymeric composite beam under moisture and elevated temperature change. The response of the composite beam subjected to various loads is analyzed under dry and moist conditions. It is assumed that only the matrix properties are adversely affected. The mechanical properties such as stiffness, strength, etc are degraded due to the combined effect of moisture and temperature change. The laminate properties are calculated using the rule of mixtures. A parametric study is carried out by varying the fiber volume fraction and by changing the fiber orientations and ply lay-ups in the laminate. From results it can be observed that the static and dynamic deflections increase due to the presence of moisture and increased temperature. The behavior of the beam is also influenced by the ply orientations and fiber volume fraction. Thus, for composite materials to reach their full potential in structural applications, it becomes quite imperative to consider factors such as moisture content, temperature, ply orientations and fiber volume during design and analysis.