Effects of guardrails on wind environment for vehicles and aerodynamic stability for bridges with box girders

2020 ◽  
pp. 136943322095682
Author(s):  
Junjie Guo ◽  
Haojun Tang ◽  
Yongle Li ◽  
Zewen Wang
Keyword(s):  
Flow Field ◽  
Suspension Bridge ◽  
Mountainous Areas ◽  
Box Girders ◽  
Aerodynamic Stability ◽  
Wind Environment ◽  
Long Span Bridges ◽  
Long Span ◽  
Strong Winds ◽  
Extreme Winds

Normally strong winds in mountainous areas possess potential threats to the safety of vehicles travelling over the long-span bridges. Generally, decreasing the porosity of the guardrails could improve wind environment for vehicles, while the changed flow field around the bridge’s girder may weaken the structural aerodynamic stability simultaneously. To solve the two seemingly contradictory issues, such a long-span suspension bridge in mountainous areas is taken as the case study, and the guardrails are optimized with different schemes. The effects on wind environment for vehicles under normal traffic conditions are first studied by computational fluid dynamics (CFD) simulations. The further effects on the aerodynamic stability of the bridge under extreme winds are then determined by wind tunnel tests, and the observed non-divergent flutter is explainedbythe change in dynamic flow field. Results show that reducing the porosity of guardrails does improve the wind environment above the bridge deck, and the improvement on wind environment increases with the increase in angle of attack. After closing the guardrails completely, however, the girder appears non-divergent vibration different from the linear theoretical flutter when the critical wind speed is exceeded. The different post-flutter behaviors at different angles of attack are mainly related to the synchronization condition between the movement of vortex and the motion of the girder.

Optimization for vertical stabilizers on flutter stability of streamlined box girders with mountainous environment

2019 ◽  
Vol 23 (2) ◽  
pp. 205-218 ◽  
Author(s):  
Junjie Guo ◽  
Haojun Tang ◽  
Yongle Li ◽  
Lianhuo Wu ◽  
Zewen Wang
Keyword(s):  
Leading Edge ◽  
Mountainous Areas ◽  
Box Girders ◽  
Box Girder ◽  
Long Span Bridges ◽  
Long Span ◽  
Participation Level ◽  
Computational Fluid Dynamics Simulations ◽  
Strong Winds ◽  
Dynamics Simulations

Wind environment in mountainous areas is very different from that in coastal and plain areas. Strong winds always show large angles of attack, affecting the flutter stability of long-span bridges which is one of the most important design factors. The central vertical stabilizer has been demonstrated to be an effective aerodynamic measure to improve the flutter stability, and this article optimizes the stabilizer to improve its applicability in mountainous areas. Computational fluid dynamics simulations are first performed to analyze the effects of stabilizers with different positions and forms on the flutter stability of an ideal box girder, and the aerodynamic mechanism is discussed based on the static and the dynamic flow fields, respectively. Wind tunnel tests are then carried out to test the critical flutter wind speed of a real box girder equipped with different stabilizers, and the change in its flutter stability is further analyzed. The results show that the vertical stabilizer with appropriate positions and heights can improve the participation level of structural heaving vibration, and thereby increases the flutter stability. At large angles of attack, the big vortex on the leading edge which may drive the bridge to flutter instability is gradually weakened with the increase in stabilizer’s height. Compared with a single stabilizer, double vertical stabilizers, in the midst of which exists a negative pressure region, could achieve better effects.

Flutter Stability of a Long-Span Suspension Bridge During Erection in Mountainous Areas

2020 ◽  
Vol 20 (09) ◽  
pp. 2050102
Author(s):  
Xingyu Chen ◽  
Ruijie Hu ◽  
Haojun Tang ◽  
Yongle Li ◽  
Enbo Yu ◽  
...  
Keyword(s):  
Dynamic Characteristics ◽  
Structural Characteristics ◽  
Suspension Bridge ◽  
Mountainous Areas ◽  
Structural Dynamic ◽  
Long Span Bridges ◽  
Aerodynamic Shape ◽  
Finite Element Software ◽  
Long Span ◽  
Structural Dynamic Characteristics

In mountainous areas, more challenges are expected for the construction of long-span bridges. The flutter instability during erection is an outstanding issue due to flexible structural characteristics and strong winds with large angles of attack. Taking the suspension bridge as an example, the flutter stability of the bridge with different suspending sequences was investigated. First, the dynamic characteristics of the bridge during erection were computed by the finite element software ANSYS, along with the effects on flutter stability discussed. Then, different aerodynamic shapes of the bridge girder during erection were considered. The aerodynamic coefficients and the critical flutter state were determined by wind tunnel tests. Based on the above analysis, some structural measures are proposed for improving the flutter stability of the bridge during erection. The results show that the flutter stability of the bridge during erection is related to the suspending sequence and the aerodynamic shape of the girder. Owing to the structural dynamic characteristics, the bridge has better flutter stability when the girder segments are suspended symmetrically from the two towers to the mid-span. Considering the construction requirement that the bridge deck should be laid without intervals, this structural superiority is seriously weakened by the unfavorable aerodynamic shape of the girder. In order to improve the flutter stability of the bridge during erection, an effective way is to adopt some temporary structural strengthening measures.

Experimental and numerical study on vortex-induced vibration of a truss girder with two decks

2020 ◽  
pp. 136943322096902
Author(s):  
Chen Fang ◽  
Ruijie Hu ◽  
Haojun Tang ◽  
Yongle Li ◽  
Zewen Wang
Keyword(s):  
Large Scale ◽  
Numerical Study ◽  
Suspension Bridge ◽  
Wake Flow ◽  
Box Girders ◽  
Vortex Induced Vibration ◽  
Long Span Bridges ◽  
Wind Speeds ◽  
Long Span ◽  
Lock In

Vortex-induced vibration (VIV) depends on aerodynamic shapes of bridge girders, which should be treated carefully in the design of long-span bridges. This paper studies the VIV performance of a suspension bridge with the truss girder which contains two separated decks. Although truss girders generally show better VIV performance than box girders, significant vibrations of this type of girders occurred in the wind tunnel tests based on a large-scale sectional model. Several lock-in regions with the same vibration frequency were observed, corresponding to different shedding vortices. Computational fluid dynamics (CFD) simulations were carried out, and monitoring points were set behind different components to study the characteristics of the shed vortices. As the truss girder consists of many members, the results show that various vortices with different dominant frequencies are formed in the wake flow. The vertical VIV of the bridge is probably driven by the vortices behind or above the upper deck, which is related to the guardrails. The torsional VIV of the bridge is probably driven by the vortices behind or below the lower deck, which is related to the service road at lower wind speeds while may be related the vertical stabilizers at higher wind speeds.

scholarly journals Ensuring the aerodynamic stability of the long-span bridges through studies in the wind tunnel

2018 ◽  
Vol 245 ◽  
pp. 02001 ◽  
Author(s):  
Evgenii Khrapunov ◽  
Sergei Solovev
Keyword(s):  
Wind Tunnel ◽  
Design Process ◽  
Aerodynamic Characteristics ◽  
Elastic Instability ◽  
Experimental Facility ◽  
Bridge Design ◽  
Aerodynamic Stability ◽  
Long Span Bridges ◽  
Long Span ◽  
Main Ideas

The main ideas of the aerodynamic studies of large bridges are presented in present paper. Main types of aero-elastic instability for bridges with spans over 100 meters are considered. A two-step modeling approach is presented. At the first stage, the aerodynamic characteristics of the span fragment are considered, at the second.stage the characteristics of the whole bridge. Methods for investigation of bridge oscillations in a special-purpose experimental facility – the Landscape Wind Tunnel – are described. Examples of tests with elastic similar models of bridges are given, and measurements to mitigate dangerous oscillations early in the bridge design process are described.

Flutter mitigation of a superlong-span suspension bridge with a double-deck truss girder through wind tunnel tests

2020 ◽  
pp. 107754632094615
Author(s):  
Yanguo Sun ◽  
Yongfu Lei ◽  
Ming Li ◽  
Haili Liao ◽  
Mingshui Li
Keyword(s):  
Wind Tunnel ◽  
Damping Ratio ◽  
Suspension Bridge ◽  
Wind Tunnel Tests ◽  
Long Span Bridges ◽  
Long Span ◽  
Upper Deck ◽  
Torsional Damping ◽  
And Control ◽  
Wind Induced Vibration

As flutter is a very dangerous wind-induced vibration phenomenon, the mitigation and control of flutter are crucial for the design of long-span bridges. In the present study, via a large number of section model wind tunnel tests, the flutter performance of a superlong-span suspension bridge with a double-deck truss girder was studied, and a series of aerodynamic and structural measures were used to mitigate and control its flutter instability. The results show that soft flutter characterized by a lack of an evident divergent point occurred for the double-deck truss girder. Upper central stabilizers on the upper deck, lower stabilizers below the lower deck, and horizontal flaps installed beside the bottoms of the sidewalks are all effective in suppressing flutter for this kind of truss girder. By combining the structural design with aerodynamic optimizations, a redesigned truss girder with widened upper carriers and sidewalks, and double lower stabilizers combined with the inspection vehicle rails is identified as the optimal flutter mitigation scheme. It was also found that the critical flutter wind speed increases with the torsional damping ratio, indicating that the dampers may be efficient in controlling soft flutter characterized by single-degree-of-freedom torsional vibration. This study aims to provide a useful reference and guidance for the flutter design optimization of long-span bridges with double-deck truss girders.

Effect of Turbulence on the Aerodynamic Stability of Long Span Bridges

2013 ◽  
Vol 639-640 ◽  
pp. 452-455 ◽  
Author(s):  
Chun Guang Li ◽  
Zheng Qing Chen ◽  
Zhi Tian Zhang
Keyword(s):  
Wind Tunnel Test ◽  
Grid Turbulence ◽  
Aerodynamic Stability ◽  
Rectangular Section ◽  
Long Span Bridges ◽  
Long Span ◽  
Turbulence Flow ◽  
Turbulence Effect ◽  
Suspended Bridge ◽  
Derivatives Of

The study deals with the problem of turbulence effect on the instability of a long span suspended bridge. Wind tunnel test of three representative section models have been carried out in four type of passive grid turbulence flow to clarify the effect of turbulence intensity and turbulence scales. It was found that the turbulence has little effect on the derivatives of those streamlined deck sections, while it exhibits significant stabilizing effect on the bluff rectangular section prism. The loss of spanwise correlation may not be the main reasons induce the change of flutter stability in turbulence.

Probabilistic Damage Detection of Long-Span Bridges Using Measured Modal Frequencies and Temperature

2018 ◽  
Vol 18 (10) ◽  
pp. 1850126 ◽  
Author(s):  
Yang Deng ◽  
Aiqun Li ◽  
Dongming Feng
Keyword(s):  
Damage Detection ◽  
Normal Distribution ◽  
Control Chart ◽  
Temperature Effects ◽  
Suspension Bridge ◽  
Standard Normal Distribution ◽  
Long Span Bridges ◽  
Long Span ◽  
Standard Normal ◽  
Probabilistic Monitoring

This paper aims to develop a new probabilistic monitoring-based framework for damage detection of long-span bridges, by eliminating the temperature effects from the measured modal frequencies, probabilistic modeling of modal frequencies using kernel density estimate, and detection damage using the control chart. A methodology is presented to address the issue of modal frequencies' non-normal distribution, which has been neglected in the past studies using the control chart to detect the modal frequencies' abnormality caused by structural damages. The efficiency of the proposed framework is validated through a case study of long-term monitoring data of a long-span suspension bridge. The results show that after elimination of the temperature effects, the selected modal frequencies are not normally distributed, while the Q statistics transferred from the modal frequencies follow the standard normal distribution. The abnormality of modal frequencies can be detected when the data points of the Q statistics exceed the limits of the control chart. Further, the control chart has sufficient sensitivity and thus can be used to detect minor abnormalities of the prototype bridge's modal frequencies. It is concluded that the proposed probabilistic monitoring-based framework offers an effective technique for structural health monitoring of long-span bridges.

scholarly journals Wind-driven damage localization on a suspension bridge

2016 ◽  
Vol 11 (1) ◽  
pp. 11-21 ◽  
Author(s):  
Marco Domaneschi ◽  
Maria Pina Limongelli ◽  
Luca Martinelli
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Damage Identification ◽  
Structural Response ◽  
Suspension Bridge ◽  
Element Model ◽  
Damage Localization ◽  
Damage Scenarios ◽  
Long Span Bridges ◽  
Long Span

The paper focuses on extending a recently proposed damage localization method, previously devised for structures subjected to a known input, to ambient vibrations induced by an unknown wind excitation. Wind induced vibrations in long-span bridges can be recorded without closing the infrastructure to traffic, providing useful data for health monitoring purposes. One major problem in damage identification of large civil structures is the scarce data recorded on damaged real structures. A detailed finite element model, able to correctly and reliably reproduce the real structure behavior under ambient excitation can be an invaluable tool, enabling the simulation of several different damage scenarios to test the performance of any monitoring system. In this work a calibrated finite element model of an existing long-span suspension bridge is used to simulate the structural response to wind actions. Several damage scenarios are simulated with different location and severity of damage to check the sensitivity of the adopted identification method. The sensitivity to the length and noise disturbances of recorded data are also investigated.

Effects of the highway live load on the additional forces of the continuously welded rails of a long-span suspension bridge

2021 ◽  
pp. 095440972110619
Author(s):  
Xiangdong Yu ◽  
Nengyu Cheng ◽  
Haiquan Jing
Keyword(s):  
High Speed ◽  
Suspension Bridge ◽  
Additional Stress ◽  
Live Load ◽  
Analysis Model ◽  
Maximum Displacement ◽  
Obvious Effect ◽  
Long Span Bridges ◽  
Long Span ◽  
Track Bridge

High-speed running trains have higher regularity requirements for rail tracks. The track-bridge interaction of long-span bridges for high-speed railways has become a key factor for engineers and researchers in the last decade. However, studies on the track-bridge interaction of long-span bridges are rare because the bridges constructed for high-speed railways are mainly short- or moderate-span bridges, and the effects of the highway live load on the additional forces of continuously welded rails (CWRs) have not been reported. In the present study, the effects of the highway live load on the additional forces of a CWR of a long-span suspension bridge are investigated through numerical simulations. A track-bridge spatial analysis model was established using the principle of the double-layer spring model and the bilinear resistance model. The additional stress and displacement of the rail are calculated, and the effects of the highway live load are analyzed and compared with those without a highway live load. The results show that the highway live load has an obvious effect on the additional forces of a CWR. Under a temperature force, the highway live load increases the maximum tensile stress and compressive stress by 10 and 13%, respectively. Under a bending force, the highway live load increases the maximum compressive rail stress and maximum displacement by 50 and 54%, respectively. Under a rail breaking force, when the highway live load is taken into consideration, the rail displacement at both sides of the broken rail varies by 50 and 42%, respectively. The highway live load must be taken into consideration when calculating the additional forces of rails on highway-railway long-span bridges.

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