Conceptual Design And Wind Stability Analysis Of A Suspension Bridge With Span Of 3500m

The limiting factor of increase of span is the aerodynamic stability problem which includes flutter stability and aerostatic stability. Improving the wind resistance of the suspension bridge is the key way of increasing the span. The research in the static and dynamic responses and the wind-induced responses of the suspension bridge is necessary.The main work of the paper is as follows.1. A design scheme of a 3500m span suspension bridge which is on the basis of the calculation theories and the designed and built bridge in the world was proposed in this paper.2. An efficien calculation of curves of wire strands of long suspension bridges was put forward which accuracy was verified by comparing with the results of the business software.3. An programme mean using ANSYS/APDL language was proposed based on outer and inner increment iteration method which took a full consideration of geometric nonlinearity and the static wind load nonlinearity.4. The paper analyzed the characteristics and the mechanism of aerostatic instability phenomena under different wind attack angles. The effect of satic wind loads on main cables and how the parameters including torsional rigidity of stiffening girder, rise span ratio,the center distance of the main cables and the width of the stiffening girder worked on the value of critical wind speed were idiscussed. Effective advice was offered based on the above reseach results.5. The flutter stability of the structure was evaluated briefly.The study shows that material strength and structural displacement were not the limiting factors of increase of span and the ability to resist live load of suspension bridge was improved as the main spans became longer. However longer span led to a more flexible structure which had prominent problems in dynamic performance and stability. The results of the three-dimensional calculation of aerostatics stability show that initial wind attack angle and three-component coefficient could determine the displacement development trend and structural failure modes.The primary cause of aerostatic instability was the change of geometrical stiffness because of geometric nonlinearity. Improving the torsional rigidity of the whole structure was the key way to increase the critical wind speed value. Some measures could be taken such as improving the torsional rigidity of stiffening girder or width-span ratio and lowering the rise span ratio. The increase of the span lead to a lower torsional frequency. The flutter problem is more evident than aerostatic problem. Separative box-girder instead of traditional monolithic box-girder s and aerodynamic measures should be used in long-span structures.