Single Tower Cable-stayed Bridge Research Articles

Research on Dynamic Response of a Single-Tower Cable-Stayed Bridge with Successive Cable Breaks Based on a 3D Index

Aiming at the problem of cable breakage of an asymmetric single-tower cable-stayed bridge by taking a single-tower cable-stayed bridge that has been in operation for more than 20 years as an engineering example, a spatial finite element model that reflected the actual stress state of the structure was established and a method for solving the time point of cable breakage was proposed. The results show that the strength of the main girder, pylon and cable could meet the stress requirements of the vibration caused by successive cable breaks, and the maximum dynamic displacement of the main girder did not exceed the stiffness limit. Although the breakage of the stay cable caused the stress in the adjacent position and the corresponding position on the opposite side of the tower to increase sharply, the stress fluctuation in other positions was small. The fluctuation of the dynamic stress of the cable tower was relatively small, but the displacement of the tower top changed greatly. The dynamic response of the cables breaking in succession was less than that of simultaneous breaking, and the structural vibration caused by cable breaking was not as severe as that caused by simultaneous breaking.

Stress Analysis and Structural Optimization of Steel–Concrete Joint of Zhonghua Road Bridge in Liaocheng

Based on Zhonghua Road Bridge in Liaocheng city, a single tower hybrid cable-stayed bridge, the stress of the steelconcrete joint of the girder is studied using the finite element method with the software MIDAS and ANSYS. The beam element model of the whole bridge is established in MIDAS CIVIL, from which the internal forces of the critical sections of the steel–concrete joint under six adverse conditions are obtained. Then, the results are applied in the refined solid-shell finite element model established in ANSYS. With the stress analysis, it is found that when the steel–concrete joint is used in the girder of the single tower cable-stayed bridge, both the compressive strength of concrete and the tensile strength of steel can be fully used, and the structural stiffness can be smoothly transferred through the two different materials in the joint, which makes the structural behavior more reasonable. The detailed stress analysis also shows that it is prone to generate considerable stress concentration at the corners and the connection between the steel lattice chamber and the pressure bearing plate, and the concentration can be avoided by local stiffening and smoothing of the chamfers. The sensitivity analysis of the web thickness in the joints and bearing plates showed that increasing the thickness of the intermediate web would lead to a moderate reduction in the stress of the web itself, while the stress in the steel member remained relatively constant. However, when the thickness of the bearing plate is increased from 60 to 80 mm, the stress of each part of the steel plate in the steel grid will be significantly reduced, and the maximum reduction can reach 48%. The improvement of concrete strength has little effect on the stress of the steel cell, and the C50 concrete strength grade used in the design is more reasonable.

Research on Reasonable Construction Plan for Cast-in-Place UHPC Bridge Deck Plate of Cable-Stayed Bridge

This article takes a single-tower cable-stayed bridge with a steel-UHPC composite deck steel box girder as the research object and develops different casting plans for the UHPC layer on the bridge deck. It analyzes the influence of factors such as the block casting sequence of the UHPC layer on the bridge deck, whether or not to set up a post-casting section, whether or not to set up bridge deck counterweights and the range of it on the additional deformation and stress of the formed UHPC bridge deck during the construction stage, exploring the impact of various factors on the structural target bridge’s completion status (cable force, bridge completion linearity, bridge deck and steel box girder stress) under different pouring schemes. Research has shown that under the constant initial tension of stay cables, adjusting the pouring sequence of UHPC bridge decks and setting post-pouring sections is not significant in reducing the tensile stress of UHPC bridge decks. The more effective technical measure is to use bridge deck counterweight pouring during construction; the closer the counterweight is to the later stage constant load loading value, the more significant the decrease in UHPC tensile stress is. When factors such as on-site construction conditions, construction period, and labor costs are limited, local weight balancing on the bridge deck can be used.

Mechanical Properties and Experimental Study of a New Laminated Girder Single Tower Cable-Stayed Bridge

Mechanical Properties and Experimental Study of a New Laminated Girder Single Tower Cable-Stayed Bridge

A New Technique for Calculating the Effective Length Factor of the Tower in Cable-Stayed Bridge

The stability issues of the tower column (hereinafter referred to as ‘tower’) in the cable-stayed bridge are studied in this paper. Two types of cable-stayed bridges are considered, namely inclined tower cable-stayed bridges without backstays and floating single-tower cable-stayed bridges. Based on the structure feature of the inclined tower cable-stayed bridge without backstays, a novel double-beam model with discrete springs is established to facilitate the linear elastic buckling analysis of the tower. To solve the model, the transfer matrix method is applied, and the stability characteristic equation of the system is derived by considering the boundary and continuity conditions. In this way, the effective length factors for the longitudinal stability of the tower are obtained. At the same time, the finite element method is utilized to verify the results obtained by the proposed model and method. Then, the parametric analysis is conducted to explore the effects of some structure parameters on the effective length factor of the tower. In addition, the influence on the effective length factor of the tower is investigated in detail when the steel cables are replaced with CFRP cables for an inclined tower cable-stayed bridge without backstays. Finally, the same processing method is extended to derive the effective length factor of the tower in the floating single-tower cable-stayed bridge. The comparison with the results of the finite element method confirms the feasibility of the present method again.

Seismic Damage Identification of Composite Cable-Stayed Bridges Using Support Vector Machines and Wavelet Networks

A seismic damage identification method for composite cable-stayed bridges has been developed. The proposed method is based on a Support Vector Machine (SVM) and Wavelet Network (WN). A shaking table test of a composite cable-stayed bridge is employed to verify the identification accuracy of the WNSVM method; the test results show that the nonlinear Finite Element Model (FEM) can correctly simulate the single-tower cable-stayed bridge, and the learning samples of WNSVM can be produced based on the nonlinear FEM. The structural damage results identified by the WNSVM method are in good agreement with those obtained by the shaking table test, and the maximum error is less than 8%. Therefore, the WNSVM method can be used for the seismic damage identification of composite cable-stayed bridges.

Calculation Method of Rotational Constraint Stiffness for a New Tower-Pier Connected System

The universal hinge support (UHS) is a new connection system for the tower and pier of a single-tower cable-stayed bridge (STCSB), which could conform the multi-direction rotation of the tower and release the bending moment at the bottom of the tower in all directions. However, UHS is not an ideal hinge in practical projects, and the rotational constraint stiffness (RCS) of UHS is constantly changed with construction. In order to determine the RCS of UHS in situ, parametric analysis was performed by establishing a theoretical mechanical model of plane rotation and a refined solid finite element (FE) model of UHS. The slope of the linear rising segment of the load–displacement curve obtained from the numerical simulation was considered as the RCS of the UHS. The relationships between RCS and the vertical force, geometric parameters, and material parameters were established, and then the calculation formula of RCS was further proposed. To verify the accuracy of the proposed formula, a case study for a real bridge was conducted in this paper. The results show that the error of the tower rotation displacement can be reduced by about 90% using the proposed method compared with the conventional method, which regards the hinge as an ideal one, and the precision is greatly improved. This study has enormous potential to quickly determinate the RCS of UHS in practical applications, and plays a great promotion role in enriching the structural system of cable-stayed bridges.

Modal Analysis of a Steel Truss Girder Cable-Stayed Bridge with Single Tower and Single Cable Plane

The dynamic characteristics of bridge structures are important in wind stability analysis, seismic design, fatigue assessment, health inspection, and maintenance of bridge structures; however, the mechanical and dynamic properties of different bridge types are different. A long-span cable-stayed bridge has the advantages of large flexibility, long natural vibration period, low natural frequency, dense spectrum, and denser modal than those of general structures. In this paper, the dynamic characteristics of a cable-stayed bridge with single pylon and single cable plane in the maximum cantilever stage and the complete bridge are analyzed. The single-tower cable-stayed bridge has some unique characteristics, such as lower cost, and a more beautiful appearance, but its torsional rigidity is lower, which increases the risk of wind damage and earthquake damage. Therefore, a finite element analysis of this bridge in the maximum cantilever state is carried out, and the influences of the main components’ rigidity, the inclination angles of the stayed cables, the supporting conditions, and the locations of the auxiliary piers are analyzed for the sustainability of this type of cable-stayed bridge. The analysis results show that a cable-stayed bridge with single pylon and single cable plane has more flexibility, and that the lateral rigidity and torsional rigidity are smaller. Structure rigidity, dip angles of the stayed cables, and positions of the auxiliary piers all have significant influences on the dynamic characteristics of cable-stayed bridges.

An Improved Static Residual Force Algorithm and Its Application in Cable Damage Identification for Cable-Stayed Bridges

For cable-stayed bridges, cables are very important components to maintain the safety of the whole bridge structure. It is well-known that change in cable force reflects the health of the cable-stayed bridge. Therefore, it is necessary to detect and quantify local damage in cables prior to the occurrence of a failure. To this end, an improved residual force algorithm independent of static load vector was proposed in this study. The proposed method mainly makes use of the particularity that only a few coefficients in the residual force and static load vectors are nonzero. By combining two different static loading modes, a new damage indicator vector was defined in the method for damage localization and quantification. Compared with existing static residual force methods, the significant advantage of the proposed algorithm is that the specific value and loading position of the static load are not required in the damage identification process. This special advantage causes this method to not require special static loading, but instead uses any load vehicle. This advantage can make the operation process of structural damage identification based on static tests easier and faster. A single tower cable-stayed bridge structure was used to verify the feasibility of the proposed method in cable damage identification. It was shown that the proposed method successfully identified cable damage, even if the value and loading point of the static load were uncertain.

Analysis of the effect of cable replacement and reconstruction of a single-tower cable-stayed bridge based on cable force optimization

Taking a single-tower cable-stayed bridge as the engineering background, this paper simulates the cable replacement process of the bridge by finite element analysis method, and improves the structural stress state by optimizing the cable force. Combined with the construction technology of demolishing old cables and installing new cables, the force of stay cables is controlled. The results of construction control and load test are compared and analyzed. It is found that bridge structure is safely stressed in the construction process, with no excessive displacement for main girder and bridge tower. Furthermore, after the cable is replaced, the overall stiffness of the bridge is significantly improved, and the load-bearing capacity and reinforcement effect are increased.

ANALYSIS ON ULTIMATE LOAD-CARRYING CAPACITY AND FAILURE MODES OF LONG-SPAN CABLE-STAYED BRIDGES WITH FLOATING SYSTEMS UNDER THE ACTION OF VERTICAL LOADS

The plastic limit analysis method is proposed to study the ultimate load-carrying capacity and failure modes of long-span cable-stayed bridges with floating systems under the action of vertical loads. Firstly, based on the assumptions of the plastic limit analysis and on the elementary mechanisms, the feasibility of the method applied to the failure analysis of cable-stayed bridges was proved. Secondly, combined with a single-tower cable-stayed bridge with a floating system, the calculation formula of ultimate load-carrying capacity was derived and the corresponding failure modes are analyzed. Finally, the plastic collapse loads and the corresponding failure modes of the cable-stayed bridges were obtained through the interior point method which is an optimization method, and then the comparison analysis of two results respectively from the plastic limit analysis method and the OpenSEES were conducted. The results show that: the girder of cable-stayed bridges subjected to vertical loads presents the characteristic of global failure when the cable's yield strength is relatively small, otherwise it presents the characteristics of local failure. The influence of the girder's yield strength on the failure behavior is just the opposite of those cables. The cable corrosion not only reduces the ultimate load factor of the cable-stayed bridges, but also changes its failure modes. Compared with the FEM, the plastic limit analysis method is simple and easy to operate. It can be used to study the ultimate load-carrying capacity and failure modes of cable-stayed bridges subjected to vertical loads and can quickly and effectively evaluate the influence of changes of structural parameters on the failure behavior of bridges.

Conceptual design of a new type of single-tower cable-stayed arch bridge and study of its mechanical properties

In order to overcome the apparent characteristics as a flexible structure of a long-span single-tower cable-stayed bridge and the excessive axial force of the main girder, and to exert the advantages of cable-stayed arch cooperative system bridges, this paper proposes a new type of single-tower cable-stayed arch cooperative system bridge. On the premise of the same amount of steel, the new cooperative system bridge can have a greater stiffness than the existing cable-stayed arch cooperative system bridge with the same span. The new system bridge uses the main girder as the rigid tie bar to balance the arches’ thrusts, which enables the main girder to have a smaller axial force and makes the cable-stayed arch cooperative system bridge a thrustless structure. The proposed bridge is assembled by the following method: (a) constructing a cable-stayed bridge with a steel box girder to bear part of the dead load and to act as a construction platform firstly; (b) then installing arch structures and fixing they with the girder to bear the remaining dead load; and, (c) adding web members between the arch ribs and the girder to form a variable-height truss structure with the arch ribs as the upper chords and the girder as a lower chord to bear most of the live load at last. The underlying mechanical principles were explained, and the mechanical properties of the cooperative system bridges were calculated with the finite element method in this paper. The stiffness and axial forces in the girders are analyzed by the finite element method and compared with those of the conventional bridges. The FEA results show that the new cooperative system bridge has the truss structure’s characteristics, which shows apparent advantages of stiffness and much smaller axial force in the main girder.

Fast operational modal analysis of a single-tower cable-stayed bridge by a Bayesian method

Cable-stayed bridges are popular bridge designs and have been widely used all around the world. To investigate the dynamic properties of cable-stayed bridges, many structural health monitoring (SHM) systems have been implemented. The vibration-based operational modal analysis (OMA) has attracted increasing attentions in the past decades by using the ambient data obtained from the SHM system, which plays an important role in extracting the key dynamic parameters of the structure for the purpose of model updating and damage detection. This paper presents the work on operational modal analysis of a single-tower cable-stayed bridge based on the data collected from a SHM system. A fast Bayesian FFT (Fast Fourier Transform) method was used to efficiently carry out the OMA to determine the most probable values of modal parameters and the associated posterior uncertainty. The modal parameters of the bridge deck and cables were identified and investigated. The uncertainty quantification was performed to evaluate the accuracy of the modal parameters. Based on the recorded temperature data, the relationship between the modal parameters and the temperature was studied. Furthermore, a prediction model of the modal parameters was developed incorporating the information of 24-hour data to investigate the probability density function (PDF) of the natural frequency and damping ratio for both the bridge deck and cables.

Dynamic Response Study of a Single Tower Cable Stayed Bridge using Finite Element Method

Cable-stayed bridges are most widely used in modern bridge construction. The dynamic response of a single tower cable-stayed bridge is studied by performing nonlinear dynamic analysis using finite element method based software ANSYS. A three-dimensional bridge model was developed. Steel cables were simulated using a single element approach. Due to the coupling effects, the bridge exhibits complex modal shapes. The response of the bridge in the vertical direction is more elastic and flexible as compared to the longitudinal and transverse direction. The response of the critical sections of girder, tower, and cables was also studied by time-history analysis using the ground acceleration data of EI-Centro 1940. A 10-second ground data with 0.0001 second time step was used.

Comfort evaluation of bridge based on stochastic process theory

Vehicle or pedestrian loads can cause bridge vibration. The pedestrian load is essentially a stochastic process, and the vibration response of pedestrian bridges is also a stochastic process. In order to evaluate the human comfort of a pedestrian bridge comprehensively, this paper presents a comfort evaluation method based on stochastic process theory. The autocorrelation function of the displacement response of a pedestrian bridge under random pedestrian load is derived in this paper. On this basis, the root mean square (RMS) of acceleration is proposed as the comfort evaluation index. Taking an asymmetric single-tower cable-stayed bridge as an example, the modal analysis of the bridge is proceeded by finite element method (FEM). Then the acceleration time histories of four measuring points are obtained by fi eld experiment. FEM results and fi eld experiment results are used to analyse random vibration of the bridge. Through a fi eld experiment and random vibration analysis of the bridge, the acceleration peak value evaluation index and the RMS of acceleration value evaluation index are compared. The results show that the RMS of acceleration index is more comprehensive and reasonable because it considers the whole-time history of the vibration response. The RMS of acceleration index is based on stochastic process theory, so it is more rigorous in mathematical expression and clearer in physical concept. It provides a reference for the evaluation of pedestrian bridge comfort.

Modeling and Parametric Analysis of In-Plane Free Vibration of a Floating Cable-Stayed Bridge with Transfer Matrix Method

As a classic bridge type, cable-stayed bridge is widely used because of its superior spanning capacity. Based on the mechanical characteristics of stay cable supporting deck, we propose a novel mechanical model aiming to evaluate the vertical bending stiffness of a floating cable-stayed bridge, namely, multi-beam model with discrete springs. First, a single-tower cable-stayed bridge is modeled as a triple-beam model with discrete springs in order to introduce the novel method easily. In this model, the stay cables are simplified as springs without mass and the single tower is regarded as an Euler–Bernoulli beam with consideration of the effect of axial force. At the same time, the bridge deck has been cut into two Euler–Bernoulli beams at the intersection of a deck and a tower. Then equations governing vibrations of the beam and tower are derived according to Hamilton’s principle for dynamic problems in elastic body under equilibrium state. The program is established by transfer matrix method to solve the eigenvalues of the system along with its boundary and matching conditions. Thus, the vertical bending stiffness of the floating cable-stayed bridge can be evaluated based on the frequency. In addition, the influences of the cables’ material, location, stiffness and number on vertical bending stiffness are analyzed in detail when the steel cables are replaced with CFRP cables. Lastly, the same method is directly extended to modeling the floating multi-tower cable-stayed bridge. The results, which are validated by commercial finite element software, demonstrate that the proposed mechanical model and method are both valuable and significant not only in theoretical research and calculation but also in design of engineering.

Summary of Research on Shock Absorption Design of Long-Span Cable-Stayed Bridges

Long-span cable-stayed bridges are a kind of bridge type that has developed rapidly in recent years. It is always the focus of research to take reasonable measures and take effective measures to ensure the safety of bridges in earthquakes. In order to improve the shock absorption performance of long-span cable-stayed bridges, scholars from various countries have carried out a series of experimental exploration and theoretical analysis. According to the number of cable-stayed bridge towers, this paper systematically combs and summarizes the shock absorption design of the three types of cable-stayed bridges of single tower cable-stayed bridge, double-tower cable-stayed bridge and multi-tower cable-stayed bridge. On the one hand, it is the design and theoretical study of shock absorption, on the other hand, it is the design and effect study of shock absorption measures. It summarizes some conclusions of the shock absorption design of various types of long-span cable-stayed bridges, and puts forward suggestions for the future shock absorption design.

Shake Table Studies on Viscous Dampers in Seismic Control of a Single-Tower Cable-Stayed Bridge Model under Near-Field Ground Motions

To investigate the effectiveness of viscous damper on seismic control of single-tower cable-stayed bridges subjected to near-field ground motions, a 1/20-scale full cable-stayed bridge model was designed, constructed and tested on shake tables. A typical far-field ground motion and a near-field one were used to excite the bridge model from low to high intensity. The seismic responses of the bridge model with and without viscous dampers were analyzed and compared. Both numerical and test results revealed that viscous dampers are quite effective in controlling deck displacement of cable-stayed bridges subjected to near-field ground motions. However, due to near-field effects, viscous damper dissipated most energy through one large hysteresis loop, extensively increasing the deformation and damping force demand of the damper. Further study based on numerical analysis reveals that to optimize deck displacement of cable-stayed bridges during an earthquake, a viscous damper with relatively larger damping coefficient should be introduced under near-field ground motions than far-field ones.

Base-isolation design of single-tower cable-stayed bridges: a case study in meizoseismal area

The single-tower cable-stayed bridge is one of the most popular types of bridges. Seismic design for this type of bridge, however, is rather difficult. When subjected to longitudinal earthquakes, the tower stands as the weakest part of all the bridge components. To solve this problem, a base-isolation design was developed and adopted for a practical single-tower cable-stayed bridge. In this design, laminated elastomeric bearings (EB) and liquid viscous dampers (LVD) were installed to serve as a base-isolation layer inside the tower cap. Numerical analysis was then conducted to investigate the variations of dynamic characteristics and seismic responses between conventional designs and base-isolation designs. LVD were used on the top of the transition pier to optimize the seismic system of the bridge. It was found that: i) the seismic loads acting on the bridge component were reduced as the seismic displacements increased. This was the result of amplification of the bridge vibration period by the EB in the base-isolation layer; ii) the seismic displacements were restrained by the LVD in the base-isolation layer, but the seismic forces increased due to improper parameter values; and iii) the seismic response decreased further by the transition pier’s LVD.

Identification and application of six-component aerodynamic admittance functions of a closed-box bridge deck

A colligated residue least square method of auto and cross spectra (CRLSMACS) is presented for identifying six-component aerodynamic admittance functions (AAFs) base on common force and pressure measurement tests in the passive grid-generated turbulent flow. The incomplete spanwise correlation of the buffeting force on the sectional model in the turbulent flow is corrected. The six-component AAFs of a flat closed-box deck of a single-tower cable-stayed bridge are identified with the presented method for the service states without/with wind barriers and the construction state under 0° wind attack angle, respectively. The buffeting responses of the bridge are then calculated for both the service and typical construction sates by using a finite element approach based on the quasi-steady buffeting theory with the tested six-component AAFs to consider the unsteady effect of buffeting forces. The calculated buffeting responses are finally compared with and found to agree well with those obtained via full bridge aeroelastic model tests, verifying the feasibility of the proposed CRLSMACS as well as the reliability of the identified six-component AAFs and the calculated buffeting responses.