Analysis On Irregular Box Beams In City Flying Junction Using FEM

By analyzing three typical irregular box beams of Shangde flying junction in hangzhou using the three-dimensional FEM, some problems in the design of irregular box beam that is often adopted in city flying junction have been studied deeply. Comparing the results of one irregular box beam obtained by the gridiron method to that by FEM, the characteristics of the application scope, merits and drawbacks of the gridiron method are convinced. It is shown that the gridiron method underestimates the results in contrast to FEM when analyzing irregular box beams. Meanwhile, the more regular the structures under consideration are, the better precision of the gridiron method is exhibited. So we must think much of this difference, and we can say this method is only applicable for simply structures and regular components of a structure. In order to enlighten whether increasing the width of the hidden beam can enforce the stability and security of the crotch, another irregular box beam in Shangde flying junction is investigated using FEM. It indicates that the width increase of the hidden beam cannot optimize the distribution of the stresses of the structure. Conversely, this action even probably increases the stresses near the crotch and thus makes the structure more danger. Therefore, when designing this type of structures, big eyes should be thrown on proper size of hidden beam. Next, a three-span curve continuous box beam has been studied by FEM, and how to set the single-pedestal pier in curve continuous box beams has been discussed. When setting the single-pedestal pier, the vehicle flow should be inspected firstly, and then a best offset distance should be selected within the feasible range of the offset distance. Meanwhile, increase the spacing interval of the double supports to the largest extent when installing a double supports on a sharing single-pedestal pier, which can enhance the stability and security of the bridge as a whole.