Optimization Design And Mechanical Property Analysis Of The Joint Between The Main Arch And Spandrel Arch Of The Sunflower Arch Bridge

Sunflower arch bridge is a new kind of bridge with the advantage of elegant design and novel structure. The stanchion of traditional Open-spandrel arch bridge is replaced by spandrel arch connected with the main arch. This structural design not only alleviate the gravity loads substantially, but also enhances the stiffness of bridge. The shape of the bridge likes a blooming sunflower. Resulting from its innovated structure and complicated stress system, the sunflower arch bridge is different from the traditional reinforced concrete bridge in the force-transmission pattern. Therefore, conducting further and elaborate research on the mechanical properties of this kind of bridge is very meaningful. Based on the real project-“Second Phoenix Bridge”, the optimization design and mechanical property analysis of the joint between the main arch and spandrel arch of the sunflower arch bridge is studied using the FEM numerical analysis. The main contents of this thesis are as follow:1. Taking “the Second Phoenix Bridge” as a research background, the spatial beam element of FEM numerical calculation software of Midas/Civil is used to simulate the bridge.under the influence of various connecting methods of connecting the main arch and the spandrel arch, variation tendency of The vertical displacement, internal force and stress of the bridge is compared. It is shown from the chart: the “partially-hinging-consolidation” method can effectively decreases the moment in skewback area of spandrel arch, increase the tensile stress in top edge of skewback area of spandrel arch, at the same time, the moment in dome area of spandrel arch and skewback area of main arch is increased slightly, the tensile stress in dome area of spandrel arch and skewback area of main arch is increased, but the stress value is not large. To ensure the both dome and skewback area of spandrel arch will not appear the large stress value, the section of partially-hinging should be larger than 50 cm, smaller than70 cm.2. The stress calculation results based on spatial beam element is not very accurate,besides, the details of structure are very difficult to be simulated by beam element. In order to get more precise stress information in vital local part, the solid element of ANSYS software is used to establish the node model of the Sunflower Arch Bridge which is verified to be practical and feasible with the FEM numerical analysis and model testing.3. Using the ANSYS software, the new modeling method based on MPC is put forward,the method can solve the connection problem between the different seize element and mismatching problem of degreed of freedom between the different kind of element effectively,which will be convenient to divide the unit independently in different area of structure, finally,the point model of “the Second Phoenix Bridge” is used to prove the effectiveness of MPC method. Besides, both the outstanding advantages and serious weakness are proposed, and this thesis gives a way to evade the defects of MPC method.4. I-beam is used to replace the concrete playing a role as the partially- hinging connecting the main arch and spandrel arch, with the changes of the number, length,inclination angle and thickness of I-beam, the stiffness of I-beam varies. Taking the stiffness of I-beam as the variables, the research is made on relationship between the variables and the stress of critical section as well as the displacement of bridge. The main conclusion is that: the tensile stress in bottom side of spandrel arch is a little large if the stiffness of I-beam remains the default, compared with the other ways, decreasing the length of I-beam is an effective method to strengthen the stiffness of partially- hinging, which will alleviate the tensile stress of spandrel arch effectively. I-beam is recommended to connect the main arch and spandrel arch, which can not only ensure the safety of structure, but also solve the casting and cracking problem in skewback area of spandrel arch.