Static Characteristic Analysis Of Super-span Suspension Bridges By Gravity Stiffness Method

The research of super-span suspension bridge is mostly based on finite element method.Due to the complexity, research of super-span suspension bridge according to traditional theory is relatively less studied.This thesis will study the static characteristic of super-span suspension bridge according to traditional theory, which can reduce the dependence on finite element method. And also, this thesis can help researchers to understand the static characteristic of super-span suspension bridge completely.The research method of this thesis is the gravity stiffness method.Firstly, for single super-span suspension bridge, the static control equations are deduced in this thesis. Then the characteristic of the solution of these equations is analyzed. CFRP is leaded into this thesis as to be the material of main cable for increasing the span of the single span suspension bridge.And the feasibility and advantage of CFRP as the material of the main cable is researched.After that, the static performance of suspension bridge with CFRP main cable is compared with that of steel main cable. Meanwhile, the influence of static performance of single span suspension bridge by span and sag ratio is analyzed.According to all of this research, it shows that span and sag ratio have a great impact on the super-span suspension bridge. CFRP main cable is greater than steel main cable on super-span suspension bridge. So CFEP main cable will be more and more used in the future.Secondly, for multi-span suspension bridge, the basic static equations are deduced in this thesis. According to these equations and taking three pylons and four spans suspension bridge as example, the dimensionless calculating equation of deflection is deduced. As to improve the calculating accuracy of this equation, the parameter α in this equation is corrected. According to the dimensionless calculating equation of deflection, the influence of the static performance of multi-span suspension bridge by some design parameters is analyzed. All of these research shows that steel main cable can still be used in mutil-span suspension bridge.And because of the increment of span, the deflection of multi-span suspension bridge is obviously increased.So the gravity stiffness is not enough for multi-span suspension bridge, which is different with single span suspension bridge.The pylon especially the mid-pylon is very important to the static performance of multi-span suspension bridge.Finally,a new method for the static performance anaylisis of suspension bridge is presented in this thesis,which is called Normalization Method.This method will make the static performance analysisi of suspension bridge more simplified. And also, this method can show the effect and influence of suspension bridge by different components clearly.