Xiang Hai-fan

Response characteristics of wind excited cables with artificial rivulet

A wind tunnel investigation of response characteristics of cables with artificial rivulet is presented. A series of cable section models of different mass and stiffness and damping ratio were designed with artificial rivulet. They were tested in smooth flow under different wind speed and yaw angle and for different position of artificial rivulet. The measured response of cable models was then analyzed and compared with the experimental results obtained by other researchers and the existing theories for wind-induced cable vibration. The results show that the measured response of horizontal cable models with artificial rivulet could be well predicted by Den Hartogs galloping theory when wind is normal to the cable axis. For the wind with certain yaw angles, the cable models with artificial rivulet exhibit velocity-restricted response characteristics.

Aerodynamic study on a proposed cable-stayed bridge in Shanghai, China

Abstract This paper deals with the aerodynamic study on a proposed composite deck cable-stayed bridge alternative over the Huangpu River in Shanghai, China. The non-steady aerodynamic model is identified directly by taking the coupled vibration response (CVR method) records under initial impulse as basic information obtained from section model wind tunnel test. The 3-D flutter analysis in full-process (from construction stage to completion stage) is carried out by using the state-space method. The analysis indicates that the alternative proposed has enough wind-resistant aerodynamic stability at completion stage, but it is necessary to add some ties or guys to raise the wind-resistant capability at the construction stage. The result of 3-D flutter analysis is also verified by the full-bridge model wind tunnel test, a first attempt of such test in China.

State-of-the-art of long-span bridge engineering in China

This paper introduces the state-of-the-art of longspan bridge engineering in China with emphases on recent long-span bridge projects, bridge deck configuration and material, design codes of long-span bridges and improvement of aerodynamic performance. The recent long-span bridge projects include thirty-eight completed suspension bridges, cable-stayed and arch bridges with a main span over 400 m, and eighteen major bridges are under construction. The bridge deck configuration and material, with prestressed concrete decks, steel-concrete composite decks and steel box decks together with several popular cross-sections, are presented. The third part briefly outlines four design codes, including static and dynamic design for highway long-span bridges, and the recent engineering experiences gained from several aerodynamic vibration control projects of long-span bridges are shared in the last part.

Flutter control effect and mechanism of central-slotting for long-span bridges

The flutter control effect and mechanism of central-slotting, which have gradually been adopted in the design and construction of long-span bridges as an effective flutter controlling measure, were investigated with theoretical analysis and wind tunnel test. Five basic girder cross-sections representing five typical aerodynamic configurations were selected and central-slotted with two different slot widths. Then, a series of sectional model tests and theoretical analyses based on the two-dimensional three-degrees-of-freedom coupling flutter analysis method (2 dimension-3 degrees of freedom method, 2d-3DOF method) were carried out to investigate the aerody namic performance, flutter mechanism and flutter modality of the five basic sections and their corresponding central-slotted sections. The results show that central-slotting can not always improve the aerodynamic stability of bridge structure. The control effect of central-slotting depends on the aerodynamic configuration of the original girder section and the corresponding central-slotting width. If the original section is inappropriate or the slot width is unsuitable, central-slotting will even deteriorate the structural flutter performance. Theoretical investigations indicated that the differences in flutter control effects come from the different formation and evolution of aerodynamic damping, and flutter modality especially the participation level of heaving motion also has a significant influence on the control effect of central-slotting.

Aerodynamic challenges in span length of suspension bridges

The potential requirement of extreme bridge spans is firstly discussed according to horizontal clearances for navigation and economical construction of deep-water foundation. To ensure the technological feasibility of suspension bridges with longer spans, the static estimation of feasible span length is then made based on current material strength and weight of cables and deck. After the performances of the countermeasures for raising the aerodynamic stability are reviewed, a trial design of a 5 000 m suspension bridge, which is estimated as a reasonable limitation of span length, is finally conducted to respond to the tomorrow’s challenge in span length of suspension bridges with the particular aspects, including dynamic stiffness, aerodynamic flutter and aerostatic stability.

Aerodynamic stability of cable-stayed bridges under erection *

In this work, nonlinear multimode aerodynamic analysis of the Jingsha Bridge under erection over the Yangtze River is conducted, and the evolutions of structural dynamic characteristics and the aerodynamic stability with erection are numerically generated. Instead of the simplified method, nonlinear multimode aerodynamic analysis is suggested to predict the aerodynamic stability of cable-stayed bridges under erection. The analysis showed that the aerodynamic stability maximizes at the relatively early stages, and decreases as the erection proceeds. The removal of the temporary piers in side spans and linking of the main girder to the anchor piers have important influence on the dynamic characteristics and aerodynamic stability of cable-stayed bridges under erection.

Three-dimensional nonlinear flutter analysis of long-span suspension bridges during erection.

In this work, the aerodynamic stability of the Yichang Suspension Bridge over Yangtze River during erection was determined by three-dimensional nonlinear flutter analysis, in which the nonlinearities of structural dynamic characteristics and aeroelastic forces caused by large deformation are fully considered. An interesting result obtained was that the bridge was more stable when the stiffening girders were erected in a non-symmetrical manner as opposed to the traditional symmetrical erection schedule. It was also found that the severe decrease in the aerodynamic stability was due to the nonlinear effects. Therefore, the nonlinear factors should be considered accurately in aerodynamic stability analysis of long-span suspension bridges during erection.

Research of the Dynamic Behavior of Long Span Suspension Bridges Under Static Wind Load

The dynamic behavior of long span suspension bridge is the key to the research of its windinduced vibration and seismic response. Since suspension bridge is a type of geometrical non\|linear structure,its dynamic behavior is closely related to the inner force state.The static wind load would thoroughly change the inner force state of the structure, and consequently change the dynamic behavior.In this paper we explore the influence on the long span suspension bridge by static wind load and put forward our calculation method of the dynamic behavior of long span suspension bridge under static wind load.