Steel truss suspension bridges are prone to developing defects after prolonged use.These defects may include corrosion of the main cable or the steel truss.To ensure the normal and safe functioning of the suspension b...Steel truss suspension bridges are prone to developing defects after prolonged use.These defects may include corrosion of the main cable or the steel truss.To ensure the normal and safe functioning of the suspension bridge,it is necessary to inspect for defects promptly,understand the cause of the defect,and locate it through the use of inspection technology.By promptly addressing defects,the suspension bridge’s safety can be ensured.The author has analyzed the common defects and causes of steel truss suspension bridges and proposed specific inspection technologies.This research is intended to aid in the timely discovery of steel truss suspension bridge defects.展开更多
This paper is concerned with the earthquake analysis of suspension bridges, in which the effects of large deflections are taken into account. The first part of the study deals with an iteration scheme for the nonlinea...This paper is concerned with the earthquake analysis of suspension bridges, in which the effects of large deflections are taken into account. The first part of the study deals with an iteration scheme for the nonlinear static analysis of suspension bridges by means of tangent stiffness matrices. The concept of tangent stiffness matrix is then introduced in the frequency equation governing the free vibration of the system. At any equilibrium stage, the vibrations are assumed to take place tangent to the curve representing the force-deflection characteristics of the structure. The bridge is idealized as a three dimensional lumped mass system and subjected to three orthogonal components of earthquake ground motion producing horizontal, vertical and torsional oscillations. By this means a realistic appraisal is achieved for torsional response as well as for the other types of vibration. The modal response spectrum technique is applied to evaluate the seismic loading for the combination of these vibrations. Various numerical examples are introduced in order to demonstrate the method of analysis. The procedure described enables the designer to evaluate the nonlinear dynamic response of suspension bridges in a systematic manner.展开更多
In order to figure out the cable flexural rigidity influence on suspension bridges,a contrast model experiment is made:a chain cable model with no flexural rigidity and a wire cable model with some flexural rigidity.A...In order to figure out the cable flexural rigidity influence on suspension bridges,a contrast model experiment is made:a chain cable model with no flexural rigidity and a wire cable model with some flexural rigidity.And then,four finite element models of a same long-span suspension bridge with different cable element are set up to be analyzed.Both experimental and numerical simulation results show that,with the increase of the span and the decrease of sag-span ratio,the influence of the cable flexural rigidity is significant.The difference of nodes displacement reaches more than 10 cm in construction analysis,which will bring some trouble to the construction.And the difference of the maximum section edge normal stress may reach 15%,which may have an adverse impact onto the bridge.Therefore,considering the cable flexural rigidity is necessary on some analysis of suspension bridges.展开更多
This paper focuses on developing an online structural condition assessment technique using long-term monitoring data measured by a structural health monitoring system. The seasonal correlations of frequency-temperatur...This paper focuses on developing an online structural condition assessment technique using long-term monitoring data measured by a structural health monitoring system. The seasonal correlations of frequency-temperature and beam-end displacement-temperature for the Runyang Suspension Bridge are performed, first. Then, a statistical modeling technique using a six-order polynomial is further applied to formulate the correlations of frequency-temperature and displacement-temperature, from which abnormal changes of measured frequencies and displacements are detected using the mean value control chart. Analysis results show that modal frequencies of higher vibration modes and displacements have remarkable seasonal correlations with the environmental temperature and the proposed method exhibits a good capability for detecting the micro damage-induced changes of modal frequencies and displacements. The results demonstrate that the proposed method can effectively eliminate temperature complications from frequency and displacement time series and is well suited for online condition monitoring of long-span suspension bridges.展开更多
The rigid central buckle employed in the Runyang Suspension Bridge (RSB) was the first time it was used in a suspension bridge in China. By using a spectral representation method and FFT technique combined with measur...The rigid central buckle employed in the Runyang Suspension Bridge (RSB) was the first time it was used in a suspension bridge in China. By using a spectral representation method and FFT technique combined with measured data,a 3D fluctuating wind field considering the tower wind effect is simulated. A novel FE model for buffeting analysis is then presented,in which a specific user-defined Matrix27 element in ANSYS is employed to simulate the aeroelastic forces and its stiffness or damping matrices are parameterized by wind velocity and vibration frequency. A nonlinear time history analysis is carried out to study the influence of the rigid central buckle on the wind-induced buffeting response of a long-span suspension bridge. The results can be used as a reference for wind resistance design of long-span suspension bridges with a rigid central buckle in the future.展开更多
During the service life of civil engineering structures such as long-span bridges, local damage at key positions may continually accumulate, and may finally result in their sudden failure. One core issue of global vib...During the service life of civil engineering structures such as long-span bridges, local damage at key positions may continually accumulate, and may finally result in their sudden failure. One core issue of global vibration-based health monitoring methods is to seek some damage indices that are sensitive to structural damage, This paper proposes an online structural health monitoring method for long-span suspension bridges using wavelet packet transform (WPT). The WPT- based method is based on the energy variations of structural ambient vibration responses decomposed using wavelet packet analysis. The main feature of this method is that the proposed wavelet packet energy spectrum (WPES) has the ability to detect structural damage from ambient vibration tests of a long-span suspension bridge. As an example application, the WPES-based health monitoring system is used on the Runyang Suspension Bridge under daily environmental conditions. The analysis reveals that changes in environmental temperature have a long-term influence on the WPES, while the effect of traffic loadings on the measured WPES of the bridge presents instantaneous changes because of the nonstationary properties of the loadings. The condition indication indices VD reflect the influences of environmental temperature on the dynamic properties of the Runyang Suspension Bridge. The field tests demonstrate that the proposed WPES-based condition indication index VD is a good candidate index for health monitoring of long-span suspension bridges under ambient excitations.展开更多
Buckling-restrained braces(BRBs)are widely used to improve the seismic performance of buildings.This paper aims to introduce BRBs to suspension bridges and assess the seismic performance of bridges with BRBs.Taking th...Buckling-restrained braces(BRBs)are widely used to improve the seismic performance of buildings.This paper aims to introduce BRBs to suspension bridges and assess the seismic performance of bridges with BRBs.Taking the Dadu River Bridge as a case study,an FEA model of the bridge is established,and different seismic measures(BRBs between the deck and the tower,BRBs at the middle of the span to replace the inclined suspenders to connect the deck and the main cables,fluid viscous dampers(FVDs)between the deck and the tower,the combination of BRBs to replace the inclined suspenders as well as FVDs between the deck and the tower)are applied to the suspension bridge.The influence of the parameters of BRBs on the seismic response of the suspension bridge is studied,and the performance of the bridge with BRBs is compared with that of the bridge with FVDs.The results indicate that the use of BRBs in place of the inclined suspenders is beneficial to reduce the displacement of the deck and limit the shear force and bending moment of the tower.The seismic performance of the suspension bridge with BRBs and FVDs is better than that of the bridge with BRBs or FVDs.Therefore,the application of BRBs is a feasible method to improve the seismic performance of the suspension bridge.展开更多
Aerodynamic instability owing to aerostatic and flutter-related failures is a significant concern in the wind-resistant design of long-span suspension bridges.Based on the dynamic characteristics of suspension bridges...Aerodynamic instability owing to aerostatic and flutter-related failures is a significant concern in the wind-resistant design of long-span suspension bridges.Based on the dynamic characteristics of suspension bridges with spans ranging from 888 to 1991 m,we proposed fitted equations for increasing spans and base frequencies.Finite element models of suspension bridges with increasing span from 1000 to 5000 m were constructed.The structural parameters were optimized to follow the fitted tendencies.To analyze the aerodynamic instability,streamlined single-box section(SBS),lattice truss section(LTS),narrow slotted section(NSS),and wide slotted section(WSS)were considered.We performed three-dimensional(3-D)full-mode flutter analysis and nonlinear aerostatic instability analysis.The flutter critical wind speed continuously decreases with span growth,showing an unlimited approaching phenomenon.Regarding aerostatic instability,the instability wind speed decreases with span to approximately 3000 m,and increases when the span is in the range of 3000 to 5000 m.Minimum aerostatic instability wind speed with SBS or LTS girder would be lower than observed maximal gust wind speed,indicating the probability of aerostatic instability.This study proposes that suspension bridge with span approximately 3000 m should be focused on both aerostatic instability and flutter,and more aerodynamic configuration optimistic optimizations for flutter are essential for super long-span suspension bridges with spans longer than 3000 m.展开更多
The complex bridge-track interaction between kilometer-span bridges and continuous Welded Rail(CWR)brings great challenges to CWR designing.Taking a suspension bridge with laying CWR as a case,the mechanical propertie...The complex bridge-track interaction between kilometer-span bridges and continuous Welded Rail(CWR)brings great challenges to CWR designing.Taking a suspension bridge with laying CWR as a case,the mechanical properties of CWR on the bridge are analyzed to reveal the sensitive areas of the track,and the design method of CWR and track structures on the beam ends are proposed.The results show that the unidirectional Rail Expansion Joints(REJ)need to be installed on the beam end of the kilometer-span bridge to reduce rail longitudinal force.Due to the bridge characteristics,there is no CWR fixed area on the kilometer-span bridge,and rail longitudinal force on the main span caused by bending loads needs to be concerned.The deformation of track on the beam end is complex,which is the weak area on the kilometer bridge,the large relative displacement between the stock rail of REJ and the main beam can cause poor stability of ballast bed on beam end,small resistance fasteners need to be laid on the sides of stock rail on the main beam to increase the stability of ballast and fasteners on the beam end.To improve the driving safety and comfort of beam end,the Sleeper-Supporting Apparatus(SSA)should be specially designed to ensure the uniform transition of track on beam ends.Temperature and wind loads have a significant impact on track regularity on the kilometer span bridge,the dynamic response of trains and bridges under those loads needs to be attended to.展开更多
This paper reports a method for strand tension in anchor spans considering rotation.A kind of co-moved coordinate system,a saddle local coordinate system,was set up.This system implemented the rotation of the splay sa...This paper reports a method for strand tension in anchor spans considering rotation.A kind of co-moved coordinate system,a saddle local coordinate system,was set up.This system implemented the rotation of the splay saddle through the rotation of the coordinate system,and all calculations proceeded in this coordinate system.Considering the rotation of the anchoring surface by the rotation of the local coordinate system of the anchoring surface,the anchorage point coordinates of strands were transformed to the local sadle coordinate system.There was a two-layer iteration adopted in the calculation.In the inner iteration,the cable force at the end of the vertical bend was taken as the variable,and the ordinate of the anchorage point was taken as the target value.In the outer iteration,the vertical tangential angle at the end of the vertical bend was taken as the variable,and the ordinate of the anchorage point was taken as the target value.The method carried out the rotation of the splay saddle and anchor surface and was simple,convenient and without approximation.The effect of rotation was considered precisely;it showed stability during the process of two-layer iteration,powerful adaptation and higher efficiency and had been successfully applied in the construction control of the Wufengshan Yangtze River Bridge,the world's first kilometer-level combined highway and railway suspension bridge.展开更多
This work is devoted to the following suspension bridge with state-dependent delay: . The main goal of this paper is to investigate the long-time behavior of the system. Under suitable hypothesis, the quasi-stability ...This work is devoted to the following suspension bridge with state-dependent delay: . The main goal of this paper is to investigate the long-time behavior of the system. Under suitable hypothesis, the quasi-stability estimates of the system are established, based on which the existence of global attractor with finite fractal dimension is obtained. Furthermore, the existence of exponential attractor is proved.展开更多
Recently,ambient vibration test(AVT)is widely used tu estimate dynamic characteristics of large civil struc- tures.Dynamic characteristics ean be affected by various envirnnmental factors such as humidity,intensity of...Recently,ambient vibration test(AVT)is widely used tu estimate dynamic characteristics of large civil struc- tures.Dynamic characteristics ean be affected by various envirnnmental factors such as humidity,intensity of wind,and temperature.Besides these environmental conditions,tire mass of vehicles may change the measured valnes when traffic-in- duced vibration is used as a source of AVT tor bridges.The effect of vehicle mass on dynamic characteristics is investigated through traffic-induced vibration tests on three bridges;(1)three-span suspension bridge(128m+404m+128m),(2) five-span continuous steel box girder bridge(59m+3@ 95m+59m),(3)simply supported plate girder bridge(46m). Acceleration histories of each measurement location under normal traffic are recorded for 30 minutes at field.These recor- ded histories are divided into individual vibrations and are combined into two groups aceording to the level of vibration;one by heavy vehicles such as trucks and buses and the other by light vehicles such as passenger cars.Separate processing of the two groups of signals shows that,for the middle and long-span bridges,the difference can be hardly detected,but,for the short span bridges whose mass is relatively small,the measured natural frequencies can change up to 5.4%.展开更多
The present work is aimed at studying the mechanic properties of the extra-wide concrete self-anchored suspension bridge under static and dynamic vehicle loads. Based on the field test using 12 heavy trucks and finite...The present work is aimed at studying the mechanic properties of the extra-wide concrete self-anchored suspension bridge under static and dynamic vehicle loads. Based on the field test using 12 heavy trucks and finite element simulations, the static deformations of different components, stress increments and distributions of the girder, as well as the vibration characteristics and damping ratio of the Hunan Road Bridge were analyzed, which is the widest self-anchored suspension bridge in China at present. The dynamic responses were calculated using the Newmark-β integration method assisted by the simulation models of bridge and vehicles, the influences on the dynamic impact coefficient(DIC) brought by the vehicle parameters, girder width, eccentricity travel and deck flatness were also researched. The spatial effect of the girder is obvious due to the extra width, which performs as the stress increments distribute unevenly along the transverse direction, and the girder deflections and stress increments of the upper plate change as a "V" and "M" shape respectively under the symmetrical vehicle loads affected by the shear lag effect, cross slope and local effect of the wheels, the maximum of stress increments are located in the junctions with the inner webs. The obvious girder torsional deformation and the apparent unevenness of the hanger forces between the two cable planes under the eccentric vehicle loads, together with the mode shapes such as the girder transverse bending and torsion which appear relatively earlier, all reflect the weakened torsional rigidity of the extra-wide girder. The transverse displacements of towers are more obvious than the longitudinal ones. As for the influences on the DIC, the static effect of the heavier vehicles plays a major role when pass through with a higher speed and the changes of vehicle suspension stiffness generate greater impacts than the suspension damp. The values of DIC in the vehicle-running side during the eccentric travel, affected by the restricts from the static effects of the eccentric moving trucks, are significantly smaller than the vehicle-free side, the increase in the road roughness is the most sensitive one among the above influential factors. The results could provide references for the design, static and dynamic response analysis of the similar extra-wide suspension bridges.展开更多
The present study stems from the realization that the general problem relating to the analysis of wind-induced vibrations in suspension bridges still requires significant attention.Sidewalk railings,overhaul tracks,an...The present study stems from the realization that the general problem relating to the analysis of wind-induced vibrations in suspension bridges still requires significant attention.Sidewalk railings,overhaul tracks,and deflectors are known to largely affect such dynamics.Here,the influence of a row of water-filled traffic barriers on the response of a sample suspension bridge is investigated numerically.It is shown that the existence of water barriers causes flow separation and non-negligible vortices with respect to the condition with no water barriers.The vortex shedding frequency at the far end is around 41.30 Hz,relatively close to the real vibration frequency.It is also shown how different incoming angles of attack can change the flow field around the bridge cross-section and the vortex detachment frequency.展开更多
Due to complicated rock structure and environment, a prototype test for a tunnel-type anchorage is infeasible. Based on the rock mass parameters from tests, a three-dimensional (3D) elastoplastic analysis was perfor...Due to complicated rock structure and environment, a prototype test for a tunnel-type anchorage is infeasible. Based on the rock mass parameters from tests, a three-dimensional (3D) elastoplastic analysis was performed to simulate the influence of the construction procedure of Siduhe bridge with tunnel-type anchorage (TTA) in Hubei Province, China. The surrounding rock and concrete anchorage body were simulated by 8 nodes 3D brick elements. The geostatic state of the complex geometric structure was established with initial data. The in-situ concrete casting of the anchorage body and excavation of the rock mass were simulated by tetrahedral shell elements. The results show that the surrounding rock is in an elastic state under the designed cable force. The numerical overloading analysis indicates that the capacity of the surrounding anchorage is 7 times that of the designed cable force. The failure pattern shows that two anchorage bodies would be pulled out in the end. The maximum shear stress appears 10 m before the back anchorage face. The maximum range influenced by the TTA under ultimate loads is about 16 m.展开更多
The non-stationary buffeting response of long span suspension bridge in time domain under strong wind loading is computed. Modeling method for generating non-stationary fluctuating winds with probabilistic model for n...The non-stationary buffeting response of long span suspension bridge in time domain under strong wind loading is computed. Modeling method for generating non-stationary fluctuating winds with probabilistic model for non-stationary strong wind fields is first presented. Non-stationary wind forces induced by strong winds on bridge deck and tower are then given a brief introduction. Finally,Non-stationary buffeting response of Pulite Bridge in China,a long span suspension bridge,is computed by using ANSYS software under four working conditions with different combination of time-varying mean wind and time-varying variance. The case study further confirms that it is necessity of considering non-stationary buffeting response for long span suspension bridge under strong wind loading,rather than only stationary buffeting response.展开更多
The load</span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">-</span></span><...The load</span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">-</span></span></span><span><span><span style="font-family:""><span style="font-family:Verdana;">response correlation is a great concern for the management and maintenance agency of bridges. Based on both the load test data and the long-term structural health monitoring data, this study aims to characterize the variation in the girder-end longitudinal displacement of a long-span suspension bridge, </span><i><span style="font-family:Verdana;">i.e.</span></i><span style="font-family:Verdana;">, the Zhaoyun Bridge in Guangdong Province of China. The load test provides a valuable chance to investigate the structural deformation in high loading levels, while the structural health monitoring system records the real-time, in-site, and long-term measurements in the normal operational stage of bridges. During the load test, the movement direction of the main girder is found to depend on the relative position of the center of gravity of the girder and the loading vehicles. However, over the period of normal operation, the quasi-static displacement at the ends of the main girder along the bridge axis is dominated by the temperature variations, rather than the traffic loading. The temperature-induced deformation is considerable so it should be filtered out from the structural total responses to highlight the live load effects or the anomalies of the bridge. As a case study, the temperature-displacement baseline model of the Zhaoyun Bridge is established and then utilized to identify the erroneous measurements in the structural health monitoring system. This paper serves as a reference for the structural behavior interpretation and performance evaluation of similar bridges.展开更多
Modern suspension bridges exhibit a trend of lighter structures,more diversified structural forms,and longer spans,the latter already exceeding two kilometers.Bridge performance under dead and live loads depends on th...Modern suspension bridges exhibit a trend of lighter structures,more diversified structural forms,and longer spans,the latter already exceeding two kilometers.Bridge performance under dead and live loads depends on their structural and main cable systems,while cablesupported bridges especially rely on the design analysis and construction control of the main cable.This literary survey systematically analyzes the research progress and state-ofthe-art status quo in the structural systems and design theories of suspension bridges,focusing on the structural systems,main cable shape analyses,live load effect analyses,and emerging lucrative research directions.More than 100 reliable references have been surveyed.(1)Multi-span or multi-main cable schemes appeal to increasing attention,which may become a better choice in terms of structural systems in scenarios with extremely long spans and heavy loads.The cable layouts,such as spatial main cables and hybrid cable-stayed suspension systems have also become feasible approaches for enhancing structural stiffness.(2)The shape-finding analysis during the construction phase is more complex and has more essential factors than that of the completed bridge state.Refined theories combining analytical methods and finite element methods are more suitable for the shape-finding analysis of complex cable systems than any single theory of the two,especially for novel cable systems.(3)The live load effect analysis methods based on traditional deflection theory or modified/improved deflection theories still have wide applications,but the refined theory of treating hangers as discrete members is also constantly developing,which is expected to provide new ideas for more complex structural analysis under the different types of live loads and their distribution forms.展开更多
Based on the spatial model,a reliable and accurate calculation method on the shape finding of self anchored suspension bridge with spatial cables was studiedin this paper.On the principle that the shape of the main ca...Based on the spatial model,a reliable and accurate calculation method on the shape finding of self anchored suspension bridge with spatial cables was studiedin this paper.On the principle that the shape of the main cables between hangers is catenary,the iteration method of calculating the shapes of the spatial main cables under the load of hanger forces was deduced.The reasonable position of the saddle was determined according to the shape and the theoretical joint point of the main cables.The shapes of the main cables at completed cable stage werecalculated based on the unchanging principle of the zero-stress lengths of the main cables.By using a numerical method combining with the finite element method,one self-anchored suspension bridge with spatial cables was analyzed.The zero-stress length of the main cables,the position of the saddle,and the pre-offsetting of the saddle of the self-anchored suspension bridge were given.The reasonable shapes of the main cables at bridge completion stage and completed cable stage were presented.The results show that the shape-finding calculation method is effective and reliable.展开更多
A 3D finite element model for the Taizhou Yangtze River Bridge,the first triple-tower long-span suspension bridge in China,is established based on the nonlinear finite element software ABAQUS,and the dynamic character...A 3D finite element model for the Taizhou Yangtze River Bridge,the first triple-tower long-span suspension bridge in China,is established based on the nonlinear finite element software ABAQUS,and the dynamic characteristics of the bridge are analyzed using the LANCZOS eigenvalue solution method. The study focuses on the effects of the vertical,lateral and torsional stiffness of the steel box girder,the rigid central buckle and the elastic restraints connecting the towers and the steel box girder on the dynamic characteristics of the triple-tower suspension bridge. Our results show that,in general,the dynamic characteristics of the triple-tower suspension bridge are similar to those of two-tower suspension bridges. The vertical,lateral and torsional stiffness of the steel box girder have different effects on the dynamic characteristics of triple-tower suspension bridges. The elastic re-straints have a more significant effect on the dynamic characteristics than the central buckle,and decreasing the stiffness of the elastic restraints results in the appearance of a longitudinal floating vibration mode of the bridge. Also,rigid central buckles have a greater influence on the dynamic characteristics of triple-tower suspension bridges than on those of two-tower suspension bridges. The results obtained could serve as a valuable numerical reference for analyzing and designing super-long-span triple-tower suspension bridges.展开更多
文摘Steel truss suspension bridges are prone to developing defects after prolonged use.These defects may include corrosion of the main cable or the steel truss.To ensure the normal and safe functioning of the suspension bridge,it is necessary to inspect for defects promptly,understand the cause of the defect,and locate it through the use of inspection technology.By promptly addressing defects,the suspension bridge’s safety can be ensured.The author has analyzed the common defects and causes of steel truss suspension bridges and proposed specific inspection technologies.This research is intended to aid in the timely discovery of steel truss suspension bridge defects.
文摘This paper is concerned with the earthquake analysis of suspension bridges, in which the effects of large deflections are taken into account. The first part of the study deals with an iteration scheme for the nonlinear static analysis of suspension bridges by means of tangent stiffness matrices. The concept of tangent stiffness matrix is then introduced in the frequency equation governing the free vibration of the system. At any equilibrium stage, the vibrations are assumed to take place tangent to the curve representing the force-deflection characteristics of the structure. The bridge is idealized as a three dimensional lumped mass system and subjected to three orthogonal components of earthquake ground motion producing horizontal, vertical and torsional oscillations. By this means a realistic appraisal is achieved for torsional response as well as for the other types of vibration. The modal response spectrum technique is applied to evaluate the seismic loading for the combination of these vibrations. Various numerical examples are introduced in order to demonstrate the method of analysis. The procedure described enables the designer to evaluate the nonlinear dynamic response of suspension bridges in a systematic manner.
基金Sponsored by Major Research Plan of the National Natural Science Foundation of China (Grant No.90715021)
文摘In order to figure out the cable flexural rigidity influence on suspension bridges,a contrast model experiment is made:a chain cable model with no flexural rigidity and a wire cable model with some flexural rigidity.And then,four finite element models of a same long-span suspension bridge with different cable element are set up to be analyzed.Both experimental and numerical simulation results show that,with the increase of the span and the decrease of sag-span ratio,the influence of the cable flexural rigidity is significant.The difference of nodes displacement reaches more than 10 cm in construction analysis,which will bring some trouble to the construction.And the difference of the maximum section edge normal stress may reach 15%,which may have an adverse impact onto the bridge.Therefore,considering the cable flexural rigidity is necessary on some analysis of suspension bridges.
基金National Natural Science Foundation of China Under Grant No.50725828 & No.50808041PhD Programs Foundation of Ministry of Education of China Under Grant No. 200802861011Scientific Research Foundation of Graduate School of Southeast University Under Grant No.YBJJ0923
文摘This paper focuses on developing an online structural condition assessment technique using long-term monitoring data measured by a structural health monitoring system. The seasonal correlations of frequency-temperature and beam-end displacement-temperature for the Runyang Suspension Bridge are performed, first. Then, a statistical modeling technique using a six-order polynomial is further applied to formulate the correlations of frequency-temperature and displacement-temperature, from which abnormal changes of measured frequencies and displacements are detected using the mean value control chart. Analysis results show that modal frequencies of higher vibration modes and displacements have remarkable seasonal correlations with the environmental temperature and the proposed method exhibits a good capability for detecting the micro damage-induced changes of modal frequencies and displacements. The results demonstrate that the proposed method can effectively eliminate temperature complications from frequency and displacement time series and is well suited for online condition monitoring of long-span suspension bridges.
基金The Key Project of the National Natural Science Foundation of China Under Grant No.50538020 the National Science Fund for Distinguished Young Scholars Under Grant No.50725828+2 种基金 the National Natural Science Foundation of China Under Grant No.50978056the National Natural Science Foundation of China for Young Scholars Under Grant No.50908046 the Ph.D.Programs Foundation of Ministry of Education of China (No.200802861012)
文摘The rigid central buckle employed in the Runyang Suspension Bridge (RSB) was the first time it was used in a suspension bridge in China. By using a spectral representation method and FFT technique combined with measured data,a 3D fluctuating wind field considering the tower wind effect is simulated. A novel FE model for buffeting analysis is then presented,in which a specific user-defined Matrix27 element in ANSYS is employed to simulate the aeroelastic forces and its stiffness or damping matrices are parameterized by wind velocity and vibration frequency. A nonlinear time history analysis is carried out to study the influence of the rigid central buckle on the wind-induced buffeting response of a long-span suspension bridge. The results can be used as a reference for wind resistance design of long-span suspension bridges with a rigid central buckle in the future.
基金National Hi-Tech Research and Development Program of China (863 Program) (No. 2006AA04Z416)the National Natural Science Foundation of China Under Grant No. 50538020
文摘During the service life of civil engineering structures such as long-span bridges, local damage at key positions may continually accumulate, and may finally result in their sudden failure. One core issue of global vibration-based health monitoring methods is to seek some damage indices that are sensitive to structural damage, This paper proposes an online structural health monitoring method for long-span suspension bridges using wavelet packet transform (WPT). The WPT- based method is based on the energy variations of structural ambient vibration responses decomposed using wavelet packet analysis. The main feature of this method is that the proposed wavelet packet energy spectrum (WPES) has the ability to detect structural damage from ambient vibration tests of a long-span suspension bridge. As an example application, the WPES-based health monitoring system is used on the Runyang Suspension Bridge under daily environmental conditions. The analysis reveals that changes in environmental temperature have a long-term influence on the WPES, while the effect of traffic loadings on the measured WPES of the bridge presents instantaneous changes because of the nonstationary properties of the loadings. The condition indication indices VD reflect the influences of environmental temperature on the dynamic properties of the Runyang Suspension Bridge. The field tests demonstrate that the proposed WPES-based condition indication index VD is a good candidate index for health monitoring of long-span suspension bridges under ambient excitations.
基金supported by Scientific Research Start Foundation of Chengdu University of Technology(No.10900-KYQD-06455).
文摘Buckling-restrained braces(BRBs)are widely used to improve the seismic performance of buildings.This paper aims to introduce BRBs to suspension bridges and assess the seismic performance of bridges with BRBs.Taking the Dadu River Bridge as a case study,an FEA model of the bridge is established,and different seismic measures(BRBs between the deck and the tower,BRBs at the middle of the span to replace the inclined suspenders to connect the deck and the main cables,fluid viscous dampers(FVDs)between the deck and the tower,the combination of BRBs to replace the inclined suspenders as well as FVDs between the deck and the tower)are applied to the suspension bridge.The influence of the parameters of BRBs on the seismic response of the suspension bridge is studied,and the performance of the bridge with BRBs is compared with that of the bridge with FVDs.The results indicate that the use of BRBs in place of the inclined suspenders is beneficial to reduce the displacement of the deck and limit the shear force and bending moment of the tower.The seismic performance of the suspension bridge with BRBs and FVDs is better than that of the bridge with BRBs or FVDs.Therefore,the application of BRBs is a feasible method to improve the seismic performance of the suspension bridge.
基金support of National Key R&D Program of China(No.2022YFC3004105)National Natural Science Foundation of China(Grant Nos.52078383,52008314,52108469).
文摘Aerodynamic instability owing to aerostatic and flutter-related failures is a significant concern in the wind-resistant design of long-span suspension bridges.Based on the dynamic characteristics of suspension bridges with spans ranging from 888 to 1991 m,we proposed fitted equations for increasing spans and base frequencies.Finite element models of suspension bridges with increasing span from 1000 to 5000 m were constructed.The structural parameters were optimized to follow the fitted tendencies.To analyze the aerodynamic instability,streamlined single-box section(SBS),lattice truss section(LTS),narrow slotted section(NSS),and wide slotted section(WSS)were considered.We performed three-dimensional(3-D)full-mode flutter analysis and nonlinear aerostatic instability analysis.The flutter critical wind speed continuously decreases with span growth,showing an unlimited approaching phenomenon.Regarding aerostatic instability,the instability wind speed decreases with span to approximately 3000 m,and increases when the span is in the range of 3000 to 5000 m.Minimum aerostatic instability wind speed with SBS or LTS girder would be lower than observed maximal gust wind speed,indicating the probability of aerostatic instability.This study proposes that suspension bridge with span approximately 3000 m should be focused on both aerostatic instability and flutter,and more aerodynamic configuration optimistic optimizations for flutter are essential for super long-span suspension bridges with spans longer than 3000 m.
基金supported by the National Key R&D Program of China(2022YFB2602901)the National Natural Science Foundation of China(No.52178405).
文摘The complex bridge-track interaction between kilometer-span bridges and continuous Welded Rail(CWR)brings great challenges to CWR designing.Taking a suspension bridge with laying CWR as a case,the mechanical properties of CWR on the bridge are analyzed to reveal the sensitive areas of the track,and the design method of CWR and track structures on the beam ends are proposed.The results show that the unidirectional Rail Expansion Joints(REJ)need to be installed on the beam end of the kilometer-span bridge to reduce rail longitudinal force.Due to the bridge characteristics,there is no CWR fixed area on the kilometer-span bridge,and rail longitudinal force on the main span caused by bending loads needs to be concerned.The deformation of track on the beam end is complex,which is the weak area on the kilometer bridge,the large relative displacement between the stock rail of REJ and the main beam can cause poor stability of ballast bed on beam end,small resistance fasteners need to be laid on the sides of stock rail on the main beam to increase the stability of ballast and fasteners on the beam end.To improve the driving safety and comfort of beam end,the Sleeper-Supporting Apparatus(SSA)should be specially designed to ensure the uniform transition of track on beam ends.Temperature and wind loads have a significant impact on track regularity on the kilometer span bridge,the dynamic response of trains and bridges under those loads needs to be attended to.
文摘This paper reports a method for strand tension in anchor spans considering rotation.A kind of co-moved coordinate system,a saddle local coordinate system,was set up.This system implemented the rotation of the splay saddle through the rotation of the coordinate system,and all calculations proceeded in this coordinate system.Considering the rotation of the anchoring surface by the rotation of the local coordinate system of the anchoring surface,the anchorage point coordinates of strands were transformed to the local sadle coordinate system.There was a two-layer iteration adopted in the calculation.In the inner iteration,the cable force at the end of the vertical bend was taken as the variable,and the ordinate of the anchorage point was taken as the target value.In the outer iteration,the vertical tangential angle at the end of the vertical bend was taken as the variable,and the ordinate of the anchorage point was taken as the target value.The method carried out the rotation of the splay saddle and anchor surface and was simple,convenient and without approximation.The effect of rotation was considered precisely;it showed stability during the process of two-layer iteration,powerful adaptation and higher efficiency and had been successfully applied in the construction control of the Wufengshan Yangtze River Bridge,the world's first kilometer-level combined highway and railway suspension bridge.
文摘This work is devoted to the following suspension bridge with state-dependent delay: . The main goal of this paper is to investigate the long-time behavior of the system. Under suitable hypothesis, the quasi-stability estimates of the system are established, based on which the existence of global attractor with finite fractal dimension is obtained. Furthermore, the existence of exponential attractor is proved.
基金the Ministry of Construction and Transportation,Korea Highway Corporation and Hyundai E&C Co.Ltd.under Project No.R&D/970003-2.
文摘Recently,ambient vibration test(AVT)is widely used tu estimate dynamic characteristics of large civil struc- tures.Dynamic characteristics ean be affected by various envirnnmental factors such as humidity,intensity of wind,and temperature.Besides these environmental conditions,tire mass of vehicles may change the measured valnes when traffic-in- duced vibration is used as a source of AVT tor bridges.The effect of vehicle mass on dynamic characteristics is investigated through traffic-induced vibration tests on three bridges;(1)three-span suspension bridge(128m+404m+128m),(2) five-span continuous steel box girder bridge(59m+3@ 95m+59m),(3)simply supported plate girder bridge(46m). Acceleration histories of each measurement location under normal traffic are recorded for 30 minutes at field.These recor- ded histories are divided into individual vibrations and are combined into two groups aceording to the level of vibration;one by heavy vehicles such as trucks and buses and the other by light vehicles such as passenger cars.Separate processing of the two groups of signals shows that,for the middle and long-span bridges,the difference can be hardly detected,but,for the short span bridges whose mass is relatively small,the measured natural frequencies can change up to 5.4%.
基金Project(51278104)supported by the National Natural Science Foundation of ChinaProject(2011Y03)supported by Jiangsu Province Transportation Scientific Research Programs,China+1 种基金Project(20133204120015)supported by the Research Fund for the Doctoral Program of Higher Education of ChinaProject(12KJB560003)supported by Jiangsu Province Universities Natural Science Foundation,China
文摘The present work is aimed at studying the mechanic properties of the extra-wide concrete self-anchored suspension bridge under static and dynamic vehicle loads. Based on the field test using 12 heavy trucks and finite element simulations, the static deformations of different components, stress increments and distributions of the girder, as well as the vibration characteristics and damping ratio of the Hunan Road Bridge were analyzed, which is the widest self-anchored suspension bridge in China at present. The dynamic responses were calculated using the Newmark-β integration method assisted by the simulation models of bridge and vehicles, the influences on the dynamic impact coefficient(DIC) brought by the vehicle parameters, girder width, eccentricity travel and deck flatness were also researched. The spatial effect of the girder is obvious due to the extra width, which performs as the stress increments distribute unevenly along the transverse direction, and the girder deflections and stress increments of the upper plate change as a "V" and "M" shape respectively under the symmetrical vehicle loads affected by the shear lag effect, cross slope and local effect of the wheels, the maximum of stress increments are located in the junctions with the inner webs. The obvious girder torsional deformation and the apparent unevenness of the hanger forces between the two cable planes under the eccentric vehicle loads, together with the mode shapes such as the girder transverse bending and torsion which appear relatively earlier, all reflect the weakened torsional rigidity of the extra-wide girder. The transverse displacements of towers are more obvious than the longitudinal ones. As for the influences on the DIC, the static effect of the heavier vehicles plays a major role when pass through with a higher speed and the changes of vehicle suspension stiffness generate greater impacts than the suspension damp. The values of DIC in the vehicle-running side during the eccentric travel, affected by the restricts from the static effects of the eccentric moving trucks, are significantly smaller than the vehicle-free side, the increase in the road roughness is the most sensitive one among the above influential factors. The results could provide references for the design, static and dynamic response analysis of the similar extra-wide suspension bridges.
文摘The present study stems from the realization that the general problem relating to the analysis of wind-induced vibrations in suspension bridges still requires significant attention.Sidewalk railings,overhaul tracks,and deflectors are known to largely affect such dynamics.Here,the influence of a row of water-filled traffic barriers on the response of a sample suspension bridge is investigated numerically.It is shown that the existence of water barriers causes flow separation and non-negligible vortices with respect to the condition with no water barriers.The vortex shedding frequency at the far end is around 41.30 Hz,relatively close to the real vibration frequency.It is also shown how different incoming angles of attack can change the flow field around the bridge cross-section and the vortex detachment frequency.
文摘Due to complicated rock structure and environment, a prototype test for a tunnel-type anchorage is infeasible. Based on the rock mass parameters from tests, a three-dimensional (3D) elastoplastic analysis was performed to simulate the influence of the construction procedure of Siduhe bridge with tunnel-type anchorage (TTA) in Hubei Province, China. The surrounding rock and concrete anchorage body were simulated by 8 nodes 3D brick elements. The geostatic state of the complex geometric structure was established with initial data. The in-situ concrete casting of the anchorage body and excavation of the rock mass were simulated by tetrahedral shell elements. The results show that the surrounding rock is in an elastic state under the designed cable force. The numerical overloading analysis indicates that the capacity of the surrounding anchorage is 7 times that of the designed cable force. The failure pattern shows that two anchorage bodies would be pulled out in the end. The maximum shear stress appears 10 m before the back anchorage face. The maximum range influenced by the TTA under ultimate loads is about 16 m.
基金Sponsored by the National Natural Science Foundation of China(Grant No.51408174)Anhui Provincial Natural Science Foundation(Grant No.1408085QE95)+1 种基金China Postdoctoral Science Foundation(Grant No.2013M540511 and 2015T80652)Key University Science Research Project of Anhui Province(Grant No.KJ2016A294)
文摘The non-stationary buffeting response of long span suspension bridge in time domain under strong wind loading is computed. Modeling method for generating non-stationary fluctuating winds with probabilistic model for non-stationary strong wind fields is first presented. Non-stationary wind forces induced by strong winds on bridge deck and tower are then given a brief introduction. Finally,Non-stationary buffeting response of Pulite Bridge in China,a long span suspension bridge,is computed by using ANSYS software under four working conditions with different combination of time-varying mean wind and time-varying variance. The case study further confirms that it is necessity of considering non-stationary buffeting response for long span suspension bridge under strong wind loading,rather than only stationary buffeting response.
文摘The load</span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">-</span></span></span><span><span><span style="font-family:""><span style="font-family:Verdana;">response correlation is a great concern for the management and maintenance agency of bridges. Based on both the load test data and the long-term structural health monitoring data, this study aims to characterize the variation in the girder-end longitudinal displacement of a long-span suspension bridge, </span><i><span style="font-family:Verdana;">i.e.</span></i><span style="font-family:Verdana;">, the Zhaoyun Bridge in Guangdong Province of China. The load test provides a valuable chance to investigate the structural deformation in high loading levels, while the structural health monitoring system records the real-time, in-site, and long-term measurements in the normal operational stage of bridges. During the load test, the movement direction of the main girder is found to depend on the relative position of the center of gravity of the girder and the loading vehicles. However, over the period of normal operation, the quasi-static displacement at the ends of the main girder along the bridge axis is dominated by the temperature variations, rather than the traffic loading. The temperature-induced deformation is considerable so it should be filtered out from the structural total responses to highlight the live load effects or the anomalies of the bridge. As a case study, the temperature-displacement baseline model of the Zhaoyun Bridge is established and then utilized to identify the erroneous measurements in the structural health monitoring system. This paper serves as a reference for the structural behavior interpretation and performance evaluation of similar bridges.
基金financially supported by the National Key R&D Program of China(No.2022YFB3706703)the National Natural Science Foundation of China(Nos.52078134 and 52378138)the Postgraduate Research&Practice Innovation Program of the Jiangsu Province of China(No.KYCX22_0220).
文摘Modern suspension bridges exhibit a trend of lighter structures,more diversified structural forms,and longer spans,the latter already exceeding two kilometers.Bridge performance under dead and live loads depends on their structural and main cable systems,while cablesupported bridges especially rely on the design analysis and construction control of the main cable.This literary survey systematically analyzes the research progress and state-ofthe-art status quo in the structural systems and design theories of suspension bridges,focusing on the structural systems,main cable shape analyses,live load effect analyses,and emerging lucrative research directions.More than 100 reliable references have been surveyed.(1)Multi-span or multi-main cable schemes appeal to increasing attention,which may become a better choice in terms of structural systems in scenarios with extremely long spans and heavy loads.The cable layouts,such as spatial main cables and hybrid cable-stayed suspension systems have also become feasible approaches for enhancing structural stiffness.(2)The shape-finding analysis during the construction phase is more complex and has more essential factors than that of the completed bridge state.Refined theories combining analytical methods and finite element methods are more suitable for the shape-finding analysis of complex cable systems than any single theory of the two,especially for novel cable systems.(3)The live load effect analysis methods based on traditional deflection theory or modified/improved deflection theories still have wide applications,but the refined theory of treating hangers as discrete members is also constantly developing,which is expected to provide new ideas for more complex structural analysis under the different types of live loads and their distribution forms.
基金The authors would like to gratefully acknowledge the supports from the National Natural Science Foundation of China(Grant No.50738002)and from the School of Civil Engineering and Architecture of Changsha University of Science and Technology and the Wind Engineering Research Center of Hunan University in China.
文摘Based on the spatial model,a reliable and accurate calculation method on the shape finding of self anchored suspension bridge with spatial cables was studiedin this paper.On the principle that the shape of the main cables between hangers is catenary,the iteration method of calculating the shapes of the spatial main cables under the load of hanger forces was deduced.The reasonable position of the saddle was determined according to the shape and the theoretical joint point of the main cables.The shapes of the main cables at completed cable stage werecalculated based on the unchanging principle of the zero-stress lengths of the main cables.By using a numerical method combining with the finite element method,one self-anchored suspension bridge with spatial cables was analyzed.The zero-stress length of the main cables,the position of the saddle,and the pre-offsetting of the saddle of the self-anchored suspension bridge were given.The reasonable shapes of the main cables at bridge completion stage and completed cable stage were presented.The results show that the shape-finding calculation method is effective and reliable.
基金Project supported by the National Natural Science Foundation of China (NSFC) (No. 50978056)the NSFC for Young Scholars (No. 50908046)the PhD Programs Foundation of MOE of China (No. 200802861012)
文摘A 3D finite element model for the Taizhou Yangtze River Bridge,the first triple-tower long-span suspension bridge in China,is established based on the nonlinear finite element software ABAQUS,and the dynamic characteristics of the bridge are analyzed using the LANCZOS eigenvalue solution method. The study focuses on the effects of the vertical,lateral and torsional stiffness of the steel box girder,the rigid central buckle and the elastic restraints connecting the towers and the steel box girder on the dynamic characteristics of the triple-tower suspension bridge. Our results show that,in general,the dynamic characteristics of the triple-tower suspension bridge are similar to those of two-tower suspension bridges. The vertical,lateral and torsional stiffness of the steel box girder have different effects on the dynamic characteristics of triple-tower suspension bridges. The elastic re-straints have a more significant effect on the dynamic characteristics than the central buckle,and decreasing the stiffness of the elastic restraints results in the appearance of a longitudinal floating vibration mode of the bridge. Also,rigid central buckles have a greater influence on the dynamic characteristics of triple-tower suspension bridges than on those of two-tower suspension bridges. The results obtained could serve as a valuable numerical reference for analyzing and designing super-long-span triple-tower suspension bridges.