Abstract: Time history response analysis finite element method and modal analysis finite element method are used to analyze large U-shaped beam aqueducts with different lengths in this paper．The earthquake responses of middle long shells and long shells with earthquake waves from transverse direction and vertical direction are studied and the regulations of the additive dynamic internal force were found．In the static analysis‚the internal force result by finite element method is just one third of the result by the tratitional method．In the dynamic analysis‚the transverse additional dynamic bending moment generated by the transverse earthquake is more than50％ of the static result by finite element method．That means when the dynamic loads are considered‚the internal force result by the traditional method is safe and the safety factor is at least two． 

Key words: U-shaped aqueduct；middle long shell；long shell；dynamic internal force