Study On Calculating Methods Of Masonry Arch Bridge

Masonry arch bridge is sort of bridge with a long history. It is peculiar for its feature that it's beautiful, firm and durable, low-cost in maintenance and repair, convenient in collecting construction materials, simple in construction technique, low cost in construction, and it need less categories of technique workers than the other kind of bridges. However, since the materials used in masonry arch bridge are particular, the application of the bridge is restricted. It's the collapse of Fenghuang bridge in Hunan, which just happened not long ago, that brings about a big bomb in the field of bridge construction and makes lots of bridge constructor focus their attention on the construction of masonry arch bridge. Majority of the present calculating methods are based on the traditional ones, which regarded the structure above the main arch as a sort of load that worked on the main arch. Thus the coactions of the structure above the main arch and the main arch, which means that the structure above the main arch and the main arch should be regarded as an integration to bear load, couldn't be well reflected according to the traditional calculating method. By establishing theoretical models in finite element method whose emerging greatly fill up the blank of the traditional calculating method, which make the main arch and the structures above the main arch integrated to bear external load, the mechanical characteristics of the main arch under the external load can be analyzed more properly and scientifically. The FEM also make up that the traditional calculating method couldn't analyze the bridge step by step according to the construction stage, which make the analyzing course more effective and could be widely applied in the actual projects.Since this paper focus on discussing calculating method of the arch bridges, the history of masonry arch bridge's development and the general situation of research in the theory of traditional design methods have been expressed in the very beginning. By elaborating the traditional calculating method, both the advantages and the disadvantages of varieties of the present design theories and methods are represented in this text, which mostly introduced the calculating method of the arch with no articulations. Combined with the cases that bridge collapse in the actual projects ,it is proposed that it make sense to research on design theory and calculating method of masonry arch bridges.As masonry materials are not homogeneous, and the finite element method has not been widely applied in this typical bridge. Therefore, as for instance, traditional catenary arch axis theory (calculating method), midas/civil FEM calculating program and doctorbridge calculating program are used to analyze the Luozehe bridge under static load , dynamic load and temperature effect. On one hand, the analyzing results in different methods had been compared afterwards in order to check if the analyzing method used in the element of beam is accurate. And then it is found out that the calculating result of traditional catenary arch axis theory could play a role of preliminary control of the mechanical characteristics of main arch. But it could not well express the mechanical characteristics of main arch step by step as the construction stage. On the other hand, three different elements-beam, shell, solid are used to establish totally different models to calculate the static and dynamic effect of Luozehe bridge. By comparing the result from three different models, it is confirmed that only the simulation analyzing method used solid element can exactly reveal the mechanical characteristics of main arch of big span masonry arch bridge.And then according to the conclusions made above, masonry arch bridges with uniform sections, under different span of different ratio of rise to span are simulated in FEM program. And how to choose proper materials and sections under different spans of different ratios of rise to span is quantified.