Self-anchored Suspension Bridge Research Articles

Failure analysis of the suspender fracture in a railway self-anchored suspension bridge: Damage identification, fatigue mechanism and remaining life prediction

A suspender fracture accident was reported in a railway self-anchored suspension bridge, arousing intensive concern to fatigue issue in the suspender end connector area which is exposed to complex stress states and cyclic traffic loads. Some critical issues involving the fatigue mechanism, the damage identification, and the remaining life prediction were investigated on the basis of on-site and lab tests, numerical simulations, and theoretical analyses. It was found that the root of an ear-plate screw with threads becomes the fatigue-prone detail since action of stress concentration and the unexpected cyclic bending. Also, an effective crack identification scheme by the ultrasonic phased array inspection as well as a verified prediction method for remaining life were proposed. Short suspenders in the main span are significantly affected by the cyclic bending, resulting in the extremely lower fatigue life than that of a long or side-span suspender. Suggestions for a classified disposal plan are provided based on fatigue risk for individual suspender.

Ultimate bearing capacity analysis of self-anchored suspension bridge with steel box girders considering local buckling

The local stability may dominate the design of a self-anchored suspension bridge with steel box girders. Due to geometric imperfections and welding residual stresses rarely considered for its ultimate bearing capacity analysis, the influences of the local buckling on the global structural behavior remain unknown. This paper presents a multi-scale finite element (FE) model for a self-anchored suspension bridge incorporating geometric imperfections and residual stresses in a steel box girder segment simulated by shell elements. Also, the pattern considering the defects in the shell FE model is validated by experiments. An extended parametric study is carried out via multi-scale FE models under various defects. Results illustrate that: ➀ the effects of local buckling on the ultimate bearing capacity of the bridge is small and can be ignored if geometric imperfections and residual stresses are not considered; ➁ the influences of local buckling becomes significant if geometric imperfections and residual stresses are included; and ➂ ultimate bearing capacity decreases with increase of defects, with geometric imperfection being the main factor influencing the ultimate bearing capacity of the bridge. Additionally, the thickness of steel plates has significant influences on the ultimate bearing capacity of the bridge. A comparison between the EN 1993–1-5 and the FE analysis results indicates that the former is conservative. This study provides useful insights for analyzing and designing local buckling from the perspective of steel bridge system.

Identifying damage in long-span self-anchored suspension bridges using characteristic indices

This study presents a methodology for detecting damage in bridge structures using three damage identification indices: the deviation of displacement influence line (DDIL), the deviation curvature of displacement influence line (DCDIL), and the relative rate of change of wavelet packet energy (RES). The proposed approach is based on the principles of displacement influence line and wavelet packet transform. To demonstrate the effectiveness of the three metrics in determining the location of structural damage, a finite element model of the main bridge in Zhengzhou Taohuayu Yellow River Bridge, a three-span twin-tower all-steel girder self-anchored suspension bridge, is evaluated. The study investigates the impact of various factors, such as damage degree, damage location, signal noise, variable speed vehicles, and random traffic flow, on the usefulness of the metrics. The results indicate that all three indices are effective in detecting damage in bridge structures. The DCDIL demonstrates a distinct, abrupt change at the location of damage, while the DDIL is somewhat less effective. Additionally, the RES curve is particularly sensitive to local damage and can identify damage locations far from the bridge span. However, the study notes that the accuracy and reliability of the RES identification indicators decrease non-linearly in the presence of signal noise. The highest values of the RES curve are positively correlated with acceleration and less closely related to uniform acceleration. A vehicle speed of 20 m/s is recommended for identifying the location of bridge structure damage. Finally, the study suggests that random, unevenly spaced traffic enhances vibration and can more precisely localize the damage location and degree of the bridge structure.

Experimental Investigation of a Rapid Calculation and Damage Diagnosis of the Quasistatic Influence Line of a Self-Anchored Suspension Bridge Based On Deflection Theory

Abstract Based on deflection theory (DT), the basic differential equations and deformation compatibility equations of self-anchored suspension bridges (SASBs) are established. The calculation formula for the stiffening girder (SG) deflection of a three-span SASB is derived, and the validity of the formula is confirmed through an example. In addition, a fast calculation method for the theoretical deflection influence line (TDIL) is proposed by using the deflection calculation formula, and a calculation method for the actual deflection influence line (ADIL) is founded on the concept of time and space coordinate transformation. By loading the bridge with a load car and using real-time monitoring of the displacement response of the bridge test section, combined with the proposed intelligent damage evaluation program, the abnormal situation of the damage of the three-span SASB can be quickly and accurately identified. The research results of this paper can provide flexible, economical and effective guidance for detecting the capacity of real bridges.

Study, Review and Analysis of Self-Anchored Suspension Bridge

Study, Review and Analysis of Self-Anchored Suspension Bridge

Twinning of the Egongyan Bridge

The First Egongyan Bridge in Chongqing, China was opened to traffic on December 27, 2000. It carries six-lanes of city traffic and two pedestrian paths, one on each side. It is a 600 m span suspension bridge. It was planned that the two pedestrian paths might eventually be converted to transit tracks in the future. However, with the rapid increase in urban traffic, the deck was transformed into an 8-lane bridge instead. Therefore, a new bridge parallel and adjacent to the old bridge was built for the rail transit. For aesthetic reasons, the city decided that the new bridge should also be a suspension bridge, with the same span length and tower height as the first bridge. The First Egongyan Bridge was a true suspension bridge with main cables anchored to ground anchors. However, the new bridge bridge’s proximity to the first bridge necessitated the construction of a self-anchored suspension bridge that did away with a second set of ground anchors. This 600 m span happened to be the world’s longest span for a self-anchored suspension bridge.

Influence of non-uniform grid plates on the vortex-induced vibration performance of twin-box girder section

The wind resistance design of long-span bridges necessitates addressing the issue of vortex-induced vibration (VIV) and implementing appropriate counter measures to mitigate it. The present study focused on the examination and comprehensive analysis of a self-anchored suspension bridge. Wind tunnel tests were conducted on sectional models to analyze the effect of wind attack angles on the VIV performance of the girder. Moreover, the investigation examined the impact of opening slot ratio and the configuration of grid plates on the trigger mechanism and performance of VIV. From the results, it is observed that the main girder displays vertical VIV when the damping ratio reaches 0.25%. At wind attack angle of − 3°, 0°, and + 3°, the dimensionless maximum amplitude of the vertical VIV normalized by the height of the girder section, represented as ymax/D, is measured to be 0.032, 0.033, and 0.023 correspondingly. When the opening slot ratio of the grid plates reaches 50%, and the grid plates are non-uniformly arranged on the opening slot, that is the sides of the opening slot position, the vertical VIV becomes non-existent. Furthermore, it is observed that when the grid plates are arranged uniformly with the same opening slot ratio, the suppression effect on VIV is relatively worse and the dimensionless maximum amplitude of the vertical VIV is reduced to 0.013 from 0.032. The flow structure mechanism is that the upside airflow is separated at the windward edge of the girder section, leading to the formation of a large upper vortex. The upper vortices interact with the airflow passing through the upper and lower portions of the central slot, colliding with the top and bottom surfaces of the downstream section. Eventually, the vortices are shifted towards the tail side of the girder section and eventually shed, causing VIV. After implementing grid plates, vortices with a certain size still form at the gap. The grid plate effectively separates the vortices from the upper and lower sections of the girder, reducing their impact on the downstream section and optimizing the VIV performance of the main girder. These research findings could serve as a guide for designing the two-box girder section.

Spanning capacity analysis of self-anchored suspension bridges based on the stability and compression strength of stiffening girder

ABSTRACT Considerable axial compression stress exists in the stiffening girder of self-anchored suspension bridges. Therefore, failures of self-anchored suspension bridges will be either due to material failure or instability of the stiffening girder, which will be the major concerns. In this study, the spanning capacity of self-anchored suspension bridges is studied based both on the stability and compression strength of the stiffening girder. Theoretical analysis reveals that, due to the elastic supports provided by the main cables and suspenders, in-plane elastic buckling of the stiffening girder is prevented. However, the stiffening girder may still buckle in the transverse direction. The extreme span length of self-anchored suspension bridges increases as the rise-to-span ratio increases. For general bridge designs, when the rise-to-span ratio is smaller than that of a bridge-specific turn point value, the spanning capacity of self-anchored suspension bridges is directly proportional to the rise-to-span ratio; however, when the rise-to-span ratio is larger than that of the turn point value, the spanning capacity of self-anchored suspension bridges is proportional to the 1/3rd power of the rise-to-span ratio. Besides, the spanning capacity of self-anchored suspension bridges will increase as the width or yielding strength of the stiffening girder increases.

Flexural performances of steel–concrete composite section of self-anchored suspension bridge: Experimental and theoretical research

This paper aims to clarify the flexural performance and the cracking load, the ultimate bearing capacity calculation theories of the steel–concrete composite section of the self-anchored suspension bridge. A refined local finite-element (FE) model of the steel–concrete composite section was built to evaluate the mechanical performance of key parts under three unfavourable load conditions. A test model of the steel–concrete composite section with a length × width × height of 7 m × 1.833 m × 1.2 m was fabricated according to the scale of 1: 3, and a four-point negative bending test was carried out. The test results show that the test model is in the elastic stage, and the residual displacement ratio is 0.7 % under the design load condition. Under the overload condition (2.3 times the design load), the experimental model is in the elastic–plastic stage, and the residual displacement ratio is 19 %. At the same time, the stress of each component still meets the requirements. Under the two conditions, the deformation angle of the composite section is small, and the stiffness transition is stable. The relative slip between the top steel plate and the concrete in the composite section is small (no more than 0.25 mm). The stress of the top steel plate and bottom steel plate of the composite section gradually decreases during the transfer from the steel stiffening beam to the concrete side. The bearing plate is the main bearer of the force transmission of the steel–concrete composite section, accounting for about 51.24 %, while the top steel plate, bottom steel plate and shear connectors share the remaining load. The steel–concrete composite section of the test model has reasonable force, smooth force transmission and good deformation coordination performance. In addition, the calculation methods of cracking load and ultimate bearing capacity of the prestressed steel–concrete composite section were proposed. The theoretically calculated value of the ultimate bearing capacity of the steel–concrete composite section is in good agreement with the FEA value, and the difference does not exceed 10 %.

The New Self-Anchored Suspension Bridge of the San Francisco Bay Bridge System: A Preliminary Study of Its Response and Behavior during a Small Earthquake

The New Self-Anchored Suspension Bridge of the San Francisco Bay Bridge System: A Preliminary Study of Its Response and Behavior during a Small Earthquake

Performance degradation prediction of extra-wide concrete self-anchored suspension bridge under vehicle load considering time-dependent effects

Performance degradation prediction of extra-wide concrete self-anchored suspension bridge under vehicle load considering time-dependent effects

Determining the Reasonable Completed Bridge State of a Self-Anchored Suspension Bridge with a Spatial Cable System Based on Minimum Bending Strain Energy: An Analytical Algorithm

Determining the Reasonable Completed Bridge State of a Self-Anchored Suspension Bridge with a Spatial Cable System Based on Minimum Bending Strain Energy: An Analytical Algorithm

Numerical Study on the Evolution Law of Explosion Response of Extra-wide Self-anchored Suspension Bridge under the Influence of Concrete Shrinkage and Creep

In order to deeply reveal the evolution law of explosion response of super wide self anchored suspension bridge under the influence of concrete shrinkage and creep, the evolution law of explosion response of extra-wide self-anchored suspension bridge under the influence of concrete shrinkage and creep is studied by simulation experiment. Based on a real bridge, the dynamic response of vertical displacement of the bottom plate of the bridge under explosion load at different ages is analyzed by numerical simulation. Firstly, the refined finite element model of the whole bridge is established by using SolidWorks software and Hypermesh software; Secondly, the explosion load is applied by ANSYS/LS-DYNA software and *LOAD_BLAST_ENHANCED (LBE) method, and the reliability of the calculation method is verified by combining the explosion test results of concrete members in the literature; Finally, the dynamic response of the bridge at different ages is analyzed by modifying the elastic modulus of the material to make the main girder reach the linearity predicted in the literature. The results show that under the action of explosion shock wave, the stress of the concrete element on the top plate of the main girder reaches the limit value and fails, forming an elliptical breach. With the increase of the age of the bridge, the vertical displacement of the bottom plate in the middle of the bridge span increases continuously, and the growth rate is “fast in front and slow in back”, which is consistent with the impact of concrete shrinkage and creep on the bridge. The results of this paper can provide an important basis for the anti-explosion protection and reinforcement of concrete extra-wide self-anchored suspension bridge.

Static Response of Self-anchored Suspension Bridge under Vehicle Load Considering Time-varying Effects

In order to study the structural state of the bridge under the influence of time-varying effect, the response of the concrete self-anchored suspension bridge under vehicle load and temperature load during the 30-year operation period is studied, through field load test and finite element analysis based on ANSYS refined spatial solid model. The results show that with the increase of the service life of the bridge, the bottom plate of the box chamber of the main girder gradually tends to be tensioned in the longitudinal direction of the bridge, and the horizontal preload stress of the main girder gradually loses when the bridge is completed; The transverse bridge stress at the junction of the outermost bottom of the box chamber and the web tends to be tensile, while the transverse bridge stress at the measuring point of the inner bottom plate gradually increases. The change value of the cable force of the hanger is obviously affected by the restraint mode of the support. Affected by the main tower support, the cable force of the hanger adjacent to the main tower decreases greatly. During the operation of the bridge, the working conditions of the mid span and east span hangers shall be monitored.

Experimental study on the flexural performance of steel-concrete composite section of self-anchored suspension bridge

In order to study the flexural performance of the steel-concrete composite section of self-anchored suspension bridge, a test model of the steel-concrete composite section was fabricated according to the scale of 1 : 3 based on the Wushui Bridge, and a four-point negative bending test was carried out. The results show that the residual displacement ratio is 0.7%, and the experimental model is in the elastic stage under the design load condition, which incidate that the component is safe under normal service condition. Under the overloading condition, the residual displacement ratio is 19%, the experimental model is in the elastic-plastic stage, but the stress of materials still meets the requirements. Under the two conditions, the deformation angle of the composite section is small and the stiffness transition is stable. The relative slip between the steel plate and concrete in the composite section is small (no more than 0.25 mm). The stress in the top steel plate and bottom steel plates of the composite section are gradually decreases during the transfer from the steel stiffening beam to the concrete side. The design of the steel-concrete composite section is reasonably loaded, and the mechanical properties are smoothly transferred.

Modified Deflection Theory for Preliminary Design of Self-Anchored Suspension Bridges

A modified deflection theory is developed for preliminary design of self-anchored suspension bridges. The proposed theory modifies the questionable approach of the existing theory considering the initial fabrication camber and overcomes the limitation that the hangers are assumed inextensible, which results in a stiffer bridge system and thus underestimation of the main cable and girder deflections. In addition, in order to avoid the inconvenience of solving a system of nonlinear equations iteratively for the preliminary design, the tower flexural stiffness is neglected rationally to obtain a system of linear equations only. With the aid of all force equilibrium and deformation compatibility conditions for the entire bridge system, the modified deflection theory is formulated. Its solution procedure is presented, which leads to a complicated sixth-order variable-coefficient ordinary differential equation, and a practical approximate solution to the equation is sought. To verify the proposed theory, a bridge example is investigated, and the results are compared to those from the previous deflection theory and complex finite element analysis. The comparisons demonstrate the effectiveness of the modified deflection theory.

Effect change of extra-wide concrete self-anchored suspension bridge under blast loads and its prediction considering time-dependent effect

In order to study the dynamic response of self-anchored suspension bridge with extra-wide concrete girder under explosive load, a real bridge was taken as the background, which is the widest on in China at present. Firstly, the refined finite element model (FEM) of the whole bridge was established. The reliability of numerical simulation method was validated by the measured data of the bridge at completion state and explosive test results of scaled girder specimen. The vertical displacement, reinforcement strain, acceleration and failure characteristics of the girder specimen under the explosive load of 3 kg TNT were analyzed. Through parametric simulation, the effects of different scale distance, concrete strength and reinforcement ratio on the explosion response of girder specimen were studied. Secondly, the dynamic responses of girder were studied. Finally, the change law of dynamic response at different ages was analyzed. The results show that the elliptical crack is formed on girder top plate. The maximum girder vertical displacement reaches 135.9 mm under 1000 kg, and the maximum increasing ratio of hanger force is 27%. The influence brought by the extra width of girder is significant. The girder vertical displacement changes along transverse direction and the concrete breach sizes are different. In addition, with the increase of service age, the girder displacement increases from 60.50 mm to 106.16 mm under the same explosive load. The research results can provide an important basis for the anti-explosion protection and reinforcement of similar extra-wide concrete self-anchored suspension bridge.

Structural Response of an Extra-Wide Concrete Self-Anchored Suspension Bridge under Static Vehicle Loads: Testing and Numerical Simulations

Structural Response of an Extra-Wide Concrete Self-Anchored Suspension Bridge under Static Vehicle Loads: Testing and Numerical Simulations

An Analytical Model for Three-Tower Self-Anchored Suspension Bridges with Longitudinal Tower-Girder Connections

This study proposes an analytical model for three-tower self-anchored suspension bridges with different longitudinal tower-girder connections based on the deflection theory. The proposed model utilizes horizontal springs to model the stiffness of the tower-girder connections and includes the nonlinear effect caused by the stiffness of the towers and the tower-girder connections. The comparison analysis demonstrates that the structural responses predicted by the proposed analytical model agreed well with those gained by the nonlinear finite element method under various live load cases. A parametric analysis is carried out to examine the effects of different parameters, including the side-to-main span ratio, stiffness of the towers, sag-to-span ratio, axial and flexural stiffness of the girder, on the mechanical characteristics of three-tower self-anchored suspension bridges. The results show that decreasing the side-to-main span ratio and the sag-to-span ratio have the same effect as increasing the flexural stiffness of the girder on improving the static behavior of three-tower self-anchored suspension bridges. The tower-girder longitudinal connection has an apparent impact on the structural performances of the bridges, and the structural system with a tower-girder connection at the mid-tower always has the smallest structural responses under live loads.

Comparative Analysis of Buffer and Damper Positions for Increasing the Seismic Performance of Suspension Bridge

In this research, a finite element model is established to investigate effective seismic control schemes for a self-anchored suspension bridge (SASB) with three towers. Nonlinear dynamic analyses are conducted to evaluate the seismic performance of SASB with different layout schemes of viscous dampers and buffers, which were installed in longitudinal direction and transversal direction, respectively. The responses of the SASB designed with 10 seismic control schemes are compared to ascertain suitable seismic schemes for SASBs. The results show that the number and location of lateral buffers have an important impact on the dynamic characterization of the SASB, especially for the first lateral mode and lateral fundamental frequency. To effectively increase the seismic performance of SASBs with three towers, mounting buffers between the side towers and the main girder of SASBs is an appropriate scheme. The viscous dampers can effectively decrease the dynamic reaction of the towers and longitudinal deformation of the girder under earthquake excitations. The plan involves the installation of dampers between the main concrete stiffening girder and the side towers as the optimal longitudinal seismic scheme for the SASB. The study offers important insights into the seismic design of SASBs with three towers.