A Research On 3D Design And Analysis Of Concrete Bridge

In modern bridge engineering, concrete and prestressed concrete bridge still has a wide range of applications. At the same time, more and more concrete bridges also increasingly have longer span, wider, irregular shape, etc characteristics. These factors lead to concrete bridges showed spatial effect force. Analysis using 3-D model of the bridge can accurately calculate the true force, and calculate the local bridge force, while 3-D design method can make bridge the design work and calculations are more consistent.3-D design and analysis of bridge is valid 3-D design and analysis perfect unity, in this method, the bridge model in the computer is expression by the 3-D solid model, if in giving the corresponding materials, loads, boundary conditions and the other information,the bridge model will be changed to calculation model. In the optimization process, only need to modify the geometric model, without the need to repeat material, load and other information to add, and create the calculation model. This method reduces the workload and also reduces the chance of error.Currently, in the process of Analysis bridge by 3-D model method, there are the complexity of create modeling, the uncontrolled division of the grid, and it is difficult to add the prestressing effect etc weakness.In this research, the software platform formed by the SALOME and Code Aster, SALOME is an open-source software that provides a generic platform for Pre-and Post-Processing for numerical simulation. It supports interoperability between CAD modeling and computation software (CAD-CAE link).and makes the numerical calculations easier. Code Aster is a finite element analysis software, which is a perfect match Salome, which can be used in mechanics, thermodynamics, electromagnetism and a series of linear and nonlinear calculations. Code Aster has a significant advantage, allows us to select it as the article's analysis software, which is in the solid element model, can achieve independence added the prestressed steel beams. Code Aster can calculate the prestressing loss, which is caused by the shrinkage and creep, elastic compression, friction etc factors. Code Aster can be used to calculate the different structures, as it is open source, so it has been widely developed. It has a rich computing unit type, through the development; Code Aster has a unique advantage and maturity in the calculation of metal structures, reinforced concrete structures and composite materials model.In this paper, a method of fast created the geometric models to be researched, which adapt to the complex structure of the bridge, at the same times we complete add the space prestressing effect to bridge model, and add the load to space Influence surface, As follows:1. Create the solid element model of bridge:Solid element model is the base of 3-D design and analysis of bridge. At present, CSG and B-rep are solid model representations which are more agreed with in industry. As the bridge has complicated shape, if we using CSG method, then the workload will be relatively heavy, So GSG is used to represent model in the computer, Salome is the platform, Python is used to expand style commands, we can quickly create 3-D solid model by defining the key sections of the bridge. Box beam is a common type of complex structure in the concrete bridges. It can be obtained through the difference set operations by external entity and hollow part of the entity internal. So we only need to create these two parts' entities. And then by the difference set operations can get the model of a box beam, at the base it is easy to create the model of a span beams. This is the whole idea of the geometric modeling, simply and clearly. It can be used to the other types of bridge's superstructure.2. Add the 3-D space prestressing effect to bridge's modeling:The most important feature of prestressed concrete bridge is that it has prestressed steel beams. In the past, when calculation of prestressed concrete structures by solid element model. Prestressing effect can be expressed by the indirect methods. But it can not consider the partial tension, prestress losses, etc. In this paper, through Code Aster's prestressed module, Unity the calculate method of prestress losses. And then Figure out the element nodes' deformation relation of steel beam and concrete. If the anchor point has been made into a node, it will cause stress concentration, so we model it into a region that has a certain of radius and length. Use python to expand shape commands, To achieve prestressed steel beams be added.3. Post-processing of Numerical Analysis:The main task of this section is add loads to the space influence surface, In bridge's 3-D model, the internal force influence line is 3-D too. To get accurate results, it is necessary to add realistic load to the model. The basic idea is very simple, Get a cross section's internal force influence line of a bridge, and then following the code to load on the most disadvantaged position, calculate the maximum internal force. The idea is very simple, but the computer is not flexibly as the human, it can not accurately determine which area is the most unfavorable position. This paper used a dynamic programming approach to simplify the 3-D influence surface load, through divided it into several stages. Determine the maximum internal force method is given, Realized add Drive loads and vehicle loads to 3-D influence surface.