Improvement of dynamic performances of suspension footbridges by modifying the hanger systems

A B S T R A C TThe suspension footbridges are very flexible due to their geometrical structure; hence they may face severe vibration problems induced mainly by natural forces and pedestrians crossing. By exceeding a certain limit, these vibrations can disturb the serviceability of the bridge as well as health and safety of the structure and pedestrians. Therefore, standard design guidelines are sets of recommendations to control the vibrations by applying restrictive design criteria. Because of the complexity of the exact simulation of the human-induced loads, these guidelines provide simplified methods to cover the frequency ranges of the human motion types in order to estimate the response of the structure without modeling the actual motion. As current paper, the simplified loading method proposed by EUR23984 EN code-as the main footbridge design standard was investigated. Its compliance with pedestrian's synchronization phenomenon was evaluated using the analysis results of a discontinuous type loading model proposed by authors. It was shown that the response of the footbridge strictly depends on the type and the speed of the pedestrian motion applied to the bridge, which is not included in the design parameters of the code. In this research work, a series of analysis is conducted on a suspension footbridge as a case study under both actual human loads and the simplified loads suggested by the code and the results were compared. It was found out that in the same crowd loading, the actual human loading creates greater vertical accelerations compare to EUR 23984 EN method results.

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“…Soti Ghat suspension footbridge in Nepal was chosen as a case study [17]. The side view and the main dimensions are shown in Figure 8.…”

Section: Structural Geometrymentioning

confidence: 99%

Dynamic Analysis of Suspension Footbridges Using an Actual Pedestrian Load Model Compared with EUR23984 EN Requirements

Samadi

Ahari

2019

IJE

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“…Generally, the limiting acceleration values are remarked as the percentage of the acceleration of gravity. These values are recommended by ISO 2631-2 [12], Ontario Bridge Code [15], and BS 5400 (British Standard) [16,17] as shown in Table 3. From the conducted numerical model analyses, the maximum accelerations resulted from excitation loads of one person running as slow, normal, and fast are 0.14% g, 0.15% g, and 0.16% g, respectively.…”

Section: Acceleration and Displacementmentioning

confidence: 99%

“…Max acceleration max (%g) Limitation of peak acceleration ISO 2631-2 [9] O N T [ 15] B S 5 4 0 0 [ 16,17] to zero after 1500 time steps. These fluctuations are due to coincidence of the frequencies of dynamic force and natural frequency in different times which delineate maximum acceleration as a result of resonance at that particular time and value of force.…”

Section: Isrn Civil Engineeringmentioning

confidence: 99%

Vibration Characteristics of Composite Footbridges under Various Human Running Loads

Sadeghi

Kueh

Fard

et al. 2013

ISRN Civil Engineering

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Various types of human running dynamic loads are numerically studied and compared to assess vibration characteristics of the light and slender composite footbridges. Running, which is a common human activity, has been categorized with respect to its intensity into jogging, normal running, and sprinting. To explore the footbridge’s performance, the vibration responses are investigated through a series of analyses in terms of the peak accelerations and displacements. In the model verification, the acquired first natural frequency of structure has shown good agreement with the value reported in the literature. The structural performance of the slender composite footbridge is then evaluated with regard to the serviceability requirement given by the current design standards. It is generally found that the maximum acceleration of the composite footbridge due to the excitation of one person running varies under different running types because of diversities in the velocity and the step frequency. Furthermore, it is shown that the investigated structure provides sufficient human comfort against vibrations for all the examined three types of running loads.

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“…For the first time, Barghian and Moghadasi [3] proposed the modified hanger system just for a case study of a suspension pedestrian bridge named Soti Ghat. Likewise, Faridani and Barghian [4], and Farahmand-Tabar and Barghian [5] studied the dynamic behavior of bridges with the modified hanger system. Similar to pedestrian suspension bridges, the modification of inclined hanger systems in a highway bridge such as cable-stayed arch bridge indicated the improvement of the dynamic properties and reduced several aforementioned disadvantages.…”

Section: Introductionmentioning

confidence: 99%

Formulating the optimum parameters of modified hanger system in the cable-arch bridge to restrain force fluctuation and overstressing problems

Farahmand‐Tabar

Barghian

2020

J Braz. Soc. Mech. Sci. Eng.

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Inclined hangers behave better than vertical ones under lateral loads (i.e., wind or earthquake) despite they are prone to fatigue phenomenon. In some instances, the slackness problem is seen in some inclined hangers, while others may become overstressed. By considering the modified hanger system, the disadvantages of vertical and inclined systems are resolved, while keeping their advantages. The objective of this study is to propose formulations for the optimum application of novel arrangement of hangers in a cable-arch bridge to suppress problems such as overstressing, force fluctuation, and decreasing the probability of fatigue phenomenon in hangers. To define optimum parameters, the modified hanger system was analyzed and compared with vertical and inclined ones considering nonlinear static analysis under dead load as an initial state plus seismic excitation and dynamic impact load of vehicles. Results indicate that the modified hanger system is improved remarkably in comparison with the inclined and vertical hanger systems.

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Improvement of dynamic performances of suspension footbridges by modifying the hanger systems

Cited by 15 publications

References 14 publications

Dynamic Analysis of Suspension Footbridges Using an Actual Pedestrian Load Model Compared with EUR23984 EN Requirements

Dynamic Analysis of Suspension Footbridges Using an Actual Pedestrian Load Model Compared with EUR23984 EN Requirements

Vibration Characteristics of Composite Footbridges under Various Human Running Loads

Formulating the optimum parameters of modified hanger system in the cable-arch bridge to restrain force fluctuation and overstressing problems

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