Wind-induced Response, Pedestrian-induced Response And Control Of Catwalk Of Suspension Bridges

In this paper, choosing a catwalk of a suspension bridge as the research object, some research are carried out for wind-induced response, pedestrian-induced response and control measures of the catwalk by means of the finite element software ANSYS.Firstly, the finite element model of the catwalk is established with the finite element software ANSYS. To verify the reliability of the finite element model, natural vibration frequencies of catwalk calculated with the finite element model are compared with that of the theoretical analyses.Secondly, wind-induced static effect and buffeting are analyzed to study on wind-induced response and control measures of catwalk. Two-dimensional linear analysis method and three-dimensional non-linear analysis method are adopted respectively to analyze aerostatic stability of catwalk. Fluctuating wind field is simulated and time-domain buffeting analysis is taken at the design wind speed of construction stages to investigate characteristics of buffeting response. The relative displacement under static wind load between the catwalk and main cable is computed to definite the maximum allowable wind speed for the main cable construction. The buffeting acceleration to evaluate vibration comfort is calculated at the maximum allowable wind speed for the main cable construction as well as the buffeting displacement to analyze the influence on construction accuracy of main cables. The effectiveness of the number of cross bridges at the center span, horizontal vibration control ropes and stay ropes to reduce lateral displacement and mitigate vibration is discussed.Finally, pedestrian-induced response and control measures are analyzed. Vibration response of catwalk under single pedestrian load is analyzed to study on the characteristics of pedestrian-induced response. Then, the relationship between fundamental frequency of local vertical bending of the catwalk and pedestrian-induced vibration acceleration response is obtained. Furthermore the reasonable distance between gantry mountings and cross bridges is put forward to avoid resonance. Then vibration response of catwalk under group load is analyzed to research on the relationship between the number of pedestrians in a group and pedestrian-induced vibration acceleration response to determine the maximum number of pedestrians in a group. The effect of the ratio of rise to span on pedestrian-induced response is investigated.It is showed in wind-induced response that aerostatic stability of catwalk could meet the requirements. Lateral displacement response is major part of buffeting response at the design wind speed for construction stages. When the wind speed is greater than10m/s, the relative displacement under static wind load between the catwalk and main cable would affect the construction accuracy. The buffeting acceleration under the maximum allowable wind speed for the main cable construction satisfies vibration comfort requirement, but lateral displacement is too large to ensure construction accuracy of main cables. Horizontal vibration control ropes and stay ropes could reduce lateral displacement and mitigate vibration effectively.It is showed in pedestrian-induced response analysis that pedestrian-induced vibration is the local vibration between gantry mountings and cross bridges. The fundamental frequency of local vertical bending vibration locates from1.7to2.2Hz, and pedestrian-induced vibration acceleration response is large. When the number of pedestrians in a group reaches5, vertical acceleration response of the catwalk exceeds lm/s2which would cause uncomfortable for pedestrians. With the increasing of the ratio of rise to span, tension of bearing cable reduce and pedestrian-induced acceleration response increase.