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Số người truy cập: 51,401,424

 DRY GALLOPING OF SURFACE MODIFICATION CABLE IN LOW SCRUTON NUMBER RANGE
Tác giả hoặc Nhóm tác giả: VO Duy Hung , Hiroshi KATSUCHI, Hitoshi YAMADA
Nơi đăng: International Symposium on Flutter and its Application ( ISSN 1349-113X JAXA-SP-16-008E); Số: 1;Từ->đến trang: 629-638;Năm: 2017
Lĩnh vực: Kỹ thuật; Loại: Bài báo khoa học; Thể loại: Quốc tế
TÓM TẮT
After the rain wind induced vibration (RWIV) phenomenon was pointed out as one of harmful vibration, cable manufacturers have proposed some types of surface modification on cable sheathing for stopping the RWIVs. In Japan, two common types of control methods are high-density polyethylene tube (HDPE) with indented surfaces, HDPE tube with twelve parallel protuberances. The indented surface was the first applied to Tatara Bridge, later to the Sutong Bridge and Stonecutters Bridge. It has been found to promote the stabilization of cable under rain-wind interaction. Parallel protuberances initially applied in Higashi Kobe Bridge. This countermeasure uses twelve of fillets along cable to control the forming of upper and lower rivulets, and then it can stop RWIVs. Nevertheless, a recent study reported that dry galloping (DG) occurred in case of indented cable with the some yaw angles and the onset reduced wind speed between 90 and 110. Therefore, the aim of this study is to clarify the effectiveness of current surface treatments, especially in case of low Scruton number.In present paper, dry galloping of bridge cables with smooth surface, parallel protuberances and indented surface are examined. Experiments were carried out in wind tunnel circuit of the Yokohama National University, Japan. Cable model was supported by 1-DOF spring system and its position can be changed by flow angle and inclined angle. WTT campaign is divided into two phases. Phase 1 carries out the experiments with circular cylinder for the baseline. Phase 2 is WTT with indented surface and parallel protuberances for estimating the level of effectiveness. Cable diameters were 110mm and 158mm with an effective model length of 1.5 m, the aspect ratio was 9.5 and 13.6 respectively. Damping ratio ranges from approximate 0.08 to 0.25% while natural frequency is around 0.75-1.02Hz in considering the typical value of actual stay cables.Under each case, responses of cable were different and it depended on wind attack angle, surface modification. The present study allows the following conclusions to be drawn. First, divergent galloping occurred in many wind attack angle in low Scruton number region. Secondly, the countermeasures of indented surface and parallel protuberances are still defective. They can suppress the divergent galloping to some extent and the large amplitude still occurred. The results and further discussion will be illustrated in full paper.
ABSTRACT
After the rain wind induced vibration (RWIV) phenomenon was pointed out as one of harmful vibration, cable manufacturers have proposed some types of surface modification on cable sheathing for stopping the RWIVs. In Japan, two common types of control methods are high-density polyethylene tube (HDPE) with indented surfaces, HDPE tube with twelve parallel protuberances. The indented surface was the first applied to Tatara Bridge, later to the Sutong Bridge and Stonecutters Bridge. It has been found to promote the stabilization of cable under rain-wind interaction. Parallel protuberances initially applied in Higashi Kobe Bridge. This countermeasure uses twelve of fillets along cable to control the forming of upper and lower rivulets, and then it can stop RWIVs. Nevertheless, a recent study reported that dry galloping (DG) occurred in case of indented cable with the some yaw angles and the onset reduced wind speed between 90 and 110. Therefore, the aim of this study is to clarify the effectiveness of current surface treatments, especially in case of low Scruton number.In present paper, dry galloping of bridge cables with smooth surface, parallel protuberances and indented surface are examined. Experiments were carried out in wind tunnel circuit of the Yokohama National University, Japan. Cable model was supported by 1-DOF spring system and its position can be changed by flow angle and inclined angle. WTT campaign is divided into two phases. Phase 1 carries out the experiments with circular cylinder for the baseline. Phase 2 is WTT with indented surface and parallel protuberances for estimating the level of effectiveness. Cable diameters were 110mm and 158mm with an effective model length of 1.5 m, the aspect ratio was 9.5 and 13.6 respectively. Damping ratio ranges from approximate 0.08 to 0.25% while natural frequency is around 0.75-1.02Hz in considering the typical value of actual stay cables.Under each case, responses of cable were different and it depended on wind attack angle, surface modification. The present study allows the following conclusions to be drawn. First, divergent galloping occurred in many wind attack angle in low Scruton number region. Secondly, the countermeasures of indented surface and parallel protuberances are still defective. They can suppress the divergent galloping to some extent and the large amplitude still occurred. The results and further discussion will be illustrated in full paper.
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