Long-span Cable-stayed Bridge Research Articles

Experimental Study of Seismic Mitigation of a Large-Span Cable-Stayed Bridge with Elastic Cables by Shaking Table Test

Elastic cables have the advantages of desirable seismic mitigation effect, low cost, and convenient installation, and have been used widely in low-to-mid-span bridges. However, their utilization in long-span cable-stayed bridges has been limited. To study the effect of elastic cable on the seismic response mitigation of long-span cable-stayed bridges, an experimental model (half-bridge model) with a geometric similarity ratio of 1∶40 was established. Both the semifloating system and the elastic restraint system were considered, and the seismic responses of the two systems under earthquake excitation were tested on the shaking table. The results demonstrated the seismic mitigation effect of the elastic restraint system, which is dependent on the characteristics of the seismic wave. The mechanism of the seismic response mitigation of the long-span cable-stayed bridge with longitudinal elastic restraint was discussed.

Seismic Performance of a Long-Span Cable-Stayed Bridge under Spatially Varying Bidirectional Spectrum-Compatible Ground Motions

Considering the socioeconomic prominence of long-span cable-stayed bridges, it is important to ensure their normal operation after strong earthquake events. To this end, their seismic performance must be based on a proper understanding of the relationship between structural capacity and seismic demand. However, evaluating the seismic demands on cable-stayed bridges is challenging due to relatively long distances between supports and the complex composition of various structural elements. The large dimension in the horizontal direction inevitably leads to incoherent input ground motions at supports, while various structural components such as cables, decks, and pylons make it difficult to define the system’s performance limit-state or capacity using a single index or function. This work presents three main contributions to properly assess the seismic performance of a long-span cable-stayed bridge. First, an algorithm was proposed to generate a set of bidirectional spectrum-compatible ground motions for the multiple supports of a bridge. Second, two performance measures were proposed to quantitatively assess the seismic demands and capacity of a cable-stayed bridge: probabilistic comparison index and axial force-bending moment (PM) safety factor. Third, the impacts of the seismic motions on the long-span cable-stayed bridge were thoroughly examined using eight different scenarios in terms of the three aspects: (1) multisupport excitation, (2) assumed soil class, and (3) wave passage effect. For this purpose, the Incheon Grand Bridge was chosen as a reference structure. This bridge has a central span of 800 m and a total length of 1,480 m. The results demonstrate that the seismic demands of the long-span cable-stayed bridge vary along with different conditions of seismic motions, and the proposed performance measures and ground motion-generating algorithm enable quantitative investigation of the impact of different conditions on the long-span cable-stayed bridge.

Assessment and mitigation on near-fault earthquake wave effects on seismic responses and pile-soil interactions of soil-pile-bridge model

A 1/70-scale soil-pile-bridge model was designed and constructed according to an extremely long-span cable-stayed bridge with a 1400 m-main span. Shaking table tests were performed to estimate the effects of the near-fault earthquake waves on the seismic responses and pile-soil interactions of the bridge model under near-fault and far-field earthquake waves in the longitudinal direction. A three-dimensional analytical model was established to represent the test results and track the response variations resulting from the near-fault earthquake waves. Finally, both control strategies were numerically studied to decrease the effects of the near-fault earthquake waves on the seismic responses of the bridge model. The results showed that the longitudinal near-fault earthquake excitation significantly increased the acceleration and displacement of the towers and girder, and augmented the curvature and strain at the bottom of the towers as compared to the far-field earthquake excitation, resulting in the bridge model suffering from more severe damage. The near-fault earthquake excitation considerably amplified the pile-soil interaction effects on the seismic responses of the towers and piers. Additionally, the analytical model could approximately represent the test results and reliably take the response variations induced by the near-fault earthquake waves. The elastic cables and supporting piers control strategies could effectively mitigate the effects of the near-fault earthquake waves on the seismic responses the bridge model except for the longitudinal acceleration and vertical displacement of the girder, preventing the towers from experiencing more significant damage.

Digital twin-based collapse fragility assessment of a long-span cable-stayed bridge under strong earthquakes

Fragility analysis is widely used in seismic performance assessment of bridges but uncertainties in seismic demand and bridge modelling affect the accuracy of assessment results. This study proposes a digital twin-based collapse fragility assessment method for long-span cable-stayed bridges under strong earthquakes. A scaled long-span cable-stayed bridge and its shake table tests are taken as an example. Three finite element (FE) models of the bridge, including a design document-based FE model, a linearly updated FE model, and a nonlinearly updated FE model, are established to demonstrate the necessity of the digital twin-based assessment. Incremental dynamic analyses (IDA) are conducted to calculate the collapse fragility curves of the FE models. The assessment results are compared with the test results in terms of collapse mechanisms, collapse ground motion intensities, and collapse probabilities. It is found that the proposed method is feasible and accurate for seismic collapse assessment of long-span cable-stayed bridges.

Transverse seismic response and failure mode of towers of a cable-stayed bridge full-model: Tests and simulations

Severe damage to towers of cable-stayed bridges have been recorded in past actual earthquakes. Therefore, increasing attention has been devoted to the seismic failure of cable-stayed bridges under strong earthquakes. However, few experimental studies focus on the seismic failure of long-span cable-stayed bridges including both superstructures and substructures under strong earthquakes. In this paper, a 1/70-scaled bridge full-model was designed and assembled following a 1400 m-span cable-stayed bridge, which was composed of the towers, girder, cables, piers, pile groups, and artificial soil placed in four shear boxes. Shaking table tests were conducted to study the seismic response and potential failure mode of towers of the bridge full-model under transverse earthquake excitation. Test results show that the tower exhibits an unexpected failure mode with the double plastic hinges, which reveals a new feature for the seismic failure of the tower of super long-span cable-stayed bridges. The plastic hinges are firstly observed at near the junction region between the tower and lower beam, then at the proximal joint portion between the tower and upper beam. The tower firstly suffers from severe damage or even local failure for the bridge full-model under strong earthquakes, but it could carry the vertical load. The seismic damage evaluated by the curvature criteria or residual displacements are in good agreement with the observed damage under earthquake excitation with low shaking amplitudes. Moreover, numerical modeling of the bridge full-model could effectively predict the dynamic properties and seismic response of the bridge full-model, and capture the character of the failure mode of the towers compared to the test results.

Prediction of Hydration Heat of Mass Concrete Based on the SVR Model

Thermal cracking in pile caps caused by concrete hydration heat will affect the safety and durability of long-span cable-stayed bridges. Therefore, effective prediction and control of concrete bridges hydration heat has been a challenging problem. In this study, the temperature of hydration heat in mass concrete pile caps belonging to a long-span cable-stayed bridge in China were monitored. Then, we adopt support vector machine regression (SVR) to establish the correlation between influencing variables and the temperature of hydration heat. The monitoring data are used to train to realize the short-term prediction of concrete temperature. The predicted results show that the SVR has a high accuracy, and the deviation between the prediction results and the measured values is quite small. The prediction performance of SVR for temperature of hydration heat of mass concrete is obviously better than that of BP neural network. The SVR prediction model can predict the temperature of 2–3 days with high accuracy. Based on the prediction results, temperature control method can be taken in advance to reduce the possibility of thermal cracks, which is of great significance for the safety and durability of actual engineering construction.

The design of super long span pedestrian landscape cable stayed bridge with sightseeing bridge tower

According to the design requirements of the super long-span pedestrian landscape cable-stayed bridge in Lake view Park, a kind of sightseeing tower-style pedestrian landscape three-tower cable-stayed bridge structure system was proposed. Sightseeing tower type bridge tower structure and duck egg arched bridge tower replace traditional cable-stayed bridge tower structure. Through the establishment of Midas finite element analysis model, dynamic modal analysis research was carried out. The analysis shows that: the sightseeing tower structure and the cable-stayed bridge tower structure are combined into one, and the two have good structural matching.

Shake Table Test on a Long-Span Cable-Stayed Bridge with Viscous Dampers Considering Wave Passage Effects

This work focused on the damping effectiveness of additional longitudinal viscous dampers employed for seismic control of long-span cable-stayed bridges considering wave passage effects. A 1/35-scale physical model scaled from a typical long-span cable-stayed bridge was designed, constructed, and tested on four shake tables. The seismic responses of the systems with and without viscous dampers, under different types of ground motions considering uniform or traveling wave excitations, were analyzed and compared. The test results show that the damping effectiveness of the additional longitudinal viscous dampers was significantly reduced under near-field ground motion. The wave passage had a great influence on the displacement responses of the towers and the deck and the relative variation amplitudes of the cable forces near the midspan. Positive damping effectiveness was commonly achieved from the additional longitudinal viscous dampers under the far-field ground motions when considering the wave passage effect, whereas negative damping effectiveness was observed under the near-field ground motion at certain wave velocities.

Stationary and non-stationary buffeting analyses of a long-span bridge under typhoon winds

The buffeting response is a vital consideration for long-span bridges in typhoon-prone areas. In the conventional analysis, the turbulence and structural vibrations are assumed as stationary processes, which are, however, inconsistent with the non-stationary features observed in typhoon winds. This poses a question on how the stationary assumption would affect the evaluation of buffeting responses under non-stationary wind actions in nature. To figure out this problem, this paper presents a comparative study on buffeting responses of a long-span cable-stayed bridge based on stationary and non-stationary perspectives. The stationary and non-stationary buffeting analysis frameworks are firstly reviewed. Then, a modal analysis of the example bridge, Sutong Cable-stayed Bridge (SCB), is conducted, and stationary and non-stationary spectral models are derived based on measured typhoon winds. On this condition, the buffeting responses of SCB are finally analyzed by following stationary and non-stationary approaches. Although the stationary results are almost identical with the non-stationary results in the mean sense, the root-mean-square value of buffeting responses are underestimated by the stationary assumption as the timevarying features existing in the spectra of turbulence are neglected. The analytical results highlights a transition from stationarity to non-stationarity in the buffeting analysis of long-span bridges.

An approach to the selection of target reliability index of Cable-stayed bridge's main girder based on optimal structural parameter ratio from cost-benefit analysis

A reasonable value of target reliability index is vital for long-span cable-stayed bridges. However, there are few methods to determine the reasonable target reliability index for long-span cable-stayed bridges. In this work, an original approach to solve this problem is developed. In this approach, a concept of optimal structural parameter ratio is presented from the perspective of cost-benefit. Determination of structural target reliability index should meet the requirements of safety and economy. This approach includes two parts. First, based on the statistical parameters of load and resistance of the cable-stayed bridge’s main girder and the most unfavourable bending moments obtained by finite element analysis, the structural reliability index was calculated by the JC method. Second, the reliability indexes with different structural parameter ratios were calculated, and the relational expression between the reliability index and structural parameter ratio was obtained by data fitting. Then the optimal structural parameter ratio was calculated from the perspective of cost-benefit. Finally, by substituting the optimal structural parameter ratio into the relational expression between the reliability index and structural parameter ratio, the optimal reliability index can be obtained. The optimal reliability index corresponding to the optimal structural parameter ratio can be regarded as the target reliability index.

Fatigue Performance of Butt-Welded Tensile Plate Cable-Girder Anchorages of Long-Span Cable-Stayed Steel Box Girder Railway Bridges

Abstract The fatigue performance of a new type of butt-welded tensile-plate cable-girder anchorage that requires higher load-bearing capacity and lower stress concentration compared with normal ten...

Static Behaviors of a Long-span Cable-Stayed Bridge with a Floating Tower under Dead Loads

Owing to the structural characteristics of floating-type structures, they can be effectively applied to overcome the limitation of conventional long-span bridges in deep water. Unlike cable-supported bridges with fixed towers, floating cable-supported bridges show relatively large displacements and rotations under the same load because of floating towers; moreover, the difference in the support stiffness causes differences in the behavior of the superstructures. In addition, the risk of overturning is greater than in conventional floating offshore structures because the center of gravity of the tower is located above the buoyancy center of the floater. A floating cable-supported bridge in which the tether supports the floating main tower is directly influenced by the tether arrangement, which is very important for the stability of the entire structure. In this study, according to the inclined tether arrangement, the outer diameter of the floater, and the buoyancy vertical load ratio (BVR), the static behavioral characteristics of the long-span cable-stayed bridges with floating tower are evaluated through nonlinear finite-element analysis. When the intersection of the tension line of the tether and a pivot point of the tower coincide, the tethers can no longer resist the tower’s rotation. For this reason, a large displacement occurs to equilibrate the structure, and further increases as it approaches the specific slope, even if it is not exactly the specific tether slope. The analytical model of this study indicates that, in terms of increasing the rotational stiffness of the main tower, it is advantageous to increase the floater diameter until a BVR of 1.8 is reached and to increase the axial stiffness of the tether from a BVR of 2.0 or higher.

Time history analysis-based nonlinear finite element model updating for a long-span cable-stayed bridge

Accurate finite element models play significant roles in the design, health monitoring and life-cycle maintenance of long-span bridges. However, due to uncertainties involved in finite element modelling, updating of the finite element model to best represent the real bridge is inevitable. This is particularly true after a long-span bridge experiences a moderate or severe earthquake and suffers some damage. This study thus proposes a time history analysis-based nonlinear finite element model updating method for long-span cable-stayed bridges. Special efforts are made to (1) establish the response time history-based objective functions and associated acceptance criteria, (2) conduct comprehensive sensitivity analyses to select appropriate nonlinear updating parameters and (3) develop a highly efficient cluster computing-aided optimization algorithm. A scaled structure of the Sutong cable-stayed bridge in China is adopted as a case study. Three nonlinear test cases performed in the shake table tests of the scaled bridge are used to validate the feasibility and accuracy of the proposed method. A good agreement is observed between the simulated response time histories and the measured response time histories for the scaled bridge under both moderate and strong ground motions. The proposed method could provide an accurate nonlinear finite element model for better performance assessment, damage detection and life-cycle maintenance of long-span cable-stayed bridges.

Study of experiment in field for long-span cable-stayed bridge

In order to provide the reasonable optimization measures for the construction of long-span steel bridge deck pavement in the alpine area, the actual pavement effect under the real load is studied by simulation simulation with the finite element analysis software relying on the construction of the bridge deck of No.1 Bridge of Haidong Avenue, Ledu District, Haidong city. Through different load positions and loading methods, the control load loading points are determined, and the parameterized analysis is carried out for the elastic modulus, thickness and temperature difference of the pavement, and finally the structural parameters of the pavement suitable for the bridge are obtained; the experimental analysis results show that the theoretical calculation idea adopted is feasible, and the measured value is within the expected range. It can be seen that the construction optimization measures and suggestions are of great significance to the construction of steel bridge deck pavement in the high cold area.

Investigation of the relationship between intensity measures and engineering demand parameters of cable-stayed bridges using intra-plate earthquakes

PurposeThe purpose of the study is to investigate and reveal this relationship of various engineering demand parameters (EDPs) of this structural type and intensity measures (IMs) under intra-plate earthquakes.Design/methodology/approachThe nonlinear finite element model used was calibrated first to the existing results of the shaking table test to verify the modeling technique.FindingsThis paper investigated the relationship between intensity measures and various engineering demand parameters of cable-stayed bridges using intra-plate earthquakes. The correlation analysis and Pearson coefficient are used to study the correlation between EDPs and IMs. The results showed that peak ground velocity (PGV)/peak ground acceleration, peak ground displacement and root-mean-square of displacement showed weak correlation with IMs. PGV, sustained maximum velocity, a peak value of spectral velocity, A95 parameter, Housner intensity and spectral acceleration at the fundamental period, the spectral velocity at the fundamental period and spectral displacement at the fundamental period were determined to be better predictors for various EDPs.Originality/valueThis paper investigated the correlation between the intensity measures of intra-plate earthquakes with the seismic responses of a typical long-span cable-stayed bridge in China. The nonlinear finite element model used was calibrated to the existing results of the shaking table test to verify the modeling technique. In total, 104 selected ground motions were applied to the calibrated model, and the responses of various components of the bridge were obtained. This study proposed PGV as the optimal IM.

Efficient simulation of fully non-stationary random wind field based on reduced 2D hermite interpolation

The spectral representation method (SRM) has been widely used to simulate stationary or non-stationary wind fields for engineering structures. Although several attempts have been made to realize the invoking of Fast Fourier Transform (FFT), the SRM is still very inefficient to simulate the fully non-stationary wind field with a time-varying coherence due to the extremely time-consuming Cholesky decompositions and large memory requirement. In this paper, a reduced 2D Hermite interpolation-enhanced approach is developed to further improve the efficiency of SRM in simulating fully non-stationary wind fields. Central to this approach is the interpolation procedure which requires Cholesky decompositions and storage of cross power spectral density matrix (CEPSD) elements only at interpolation knots. Thus the computational costs of Cholesky decompositions and memory requirement are dramatically decreased. The number of Cholesky decompositions is then fixed with no relation to the segments of frequency and duration of wind samples, which eliminates the Cholesky decomposition as a cause that affects the simulation efficiency. Meanwhile, each element in the decomposed CEPSD matrix is decoupled into products of time- and frequency-dependent functions by the reduced 2D Hermite interpolation, so the FFT can be used to expedite the summation of trigonometric terms. Apart from using FFT, another merit of the proposed approach is that an accelerated FFT algorithm can be incorporated to further improve the simulation efficiency based on the specific decoupled expression of frequency-dependent functions. The parametric analysis shows that the proposed approach is very efficient in comparison with the existing method using proper orthogonal decomposition (POD), and it provides a desired level of simulation accuracy when appropriate interpolation interval is selected. The case study in simulating the fully non-stationary wind field of a long-span cable-stayed bridge demonstrates the effectiveness of the proposed approach with verifications on both evolutionary power spectra and correlation functions.

Numerical Simulation on Thermomechanical Coupling Behavior of Early-Age Concrete in the Large-Scale Steel–Concrete Connecting Segment of a Hybrid-Girder Cable-Stayed Bridge

Abstract Large-scale connecting segments can provide reasonable load transition in hybrid girders, and have been broadly used in long-span cable-stayed bridges. However, the large volume of concret...

Numerical simulation of double deck pavement for long-span cable-stayed bridge

The double-deck pavement of the long-span cable-stayed bridge was set as the research object, by setting the load position, load condition and reference point on the bridge deck, the parametric analysis of the elastic modulus, thickness and temperature of the pavement material was performed. Then Pavement structure parameters suitable for the bridge were get. The finite element software was used to simulate the pavement effect of the No. 1 bridge of Haidong Avenue under the actual load, which provided reasonable optimization measures for the construction method of large-span steel bridge deck pavement in high and cold areas.

Deformation monitoring and analysis of a long-span cable-stayed bridge during strong typhoons

Deformation monitoring of the girders and towers during strong winds or typhoons is vitally important for serviceability and safety assessment of in-service long-span bridges. Although some field measurements were carried out, our understanding on the features of the bridge deformation during high-speed winds is still limited; therefore, more monitoring-based studies are still required. In this study, the displacements of a long-span cable-stayed bridge during three typhoons are recorded by the Global Positioning System (GPS) in its Structural Health Monitoring (SHM) system. The monitored displacements are decomposed into static and dynamic components using the autoregressive moving average model. The outliers and the low-frequency colored noise in the dynamic components are then analyzed and eliminated. On that basis, the relationship between the static displacements and environmental factors, in terms of wind and temperature, is investigated. Afterwards, the variation of dynamic displacements of the bridge is analyzed with respect to the surrounding environments. Results show that the structural temperature is the major reason that changes the static deformation of the bridge. The dynamic deformation of the girder is mainly controlled by the in-situ wind speed. Nevertheless, the influence of structural temperature on dynamic deformation is mildly. Conclusions are aimed to provide a reference for wind resistant design and assessment of similar long-span bridges.

Nonlinear parametric vibration with different orders of small parameters for stayed cables

For long-span cable-stayed bridges, parametric vibration associated with the axial component of the motion, therefore, could lead to serious dynamic instability or fatigue damage accumulations on cables, etc. Due to different stiffness and length of the cables, the governing perturbation equations of vibration for the cables vary with each other leading to different relationships of frequency and amplitude. In the present study, a theoretical model of the parametric vibration for a stayed cable subjected to the axial excitation is used, and the static sag of the cable is considered as the parabola with the only inclusion of the first mode of the cable. Governing vibration equation is obtained, consisting of nonlinear terms, namely external oscillation term, parametric oscillation term, cubic term, and quadratic term. Multiple scales method is applied to solve the governing nonlinear vibration equation. Based on the data for cables of the Shanghai Yangtze River Bridge, the coefficients of nonlinear terms are obtained, and the perturbation orders of nonlinear terms are determined. Based on the perturbation order of nonlinear terms, three types of perturbation equations motion are built based on different physical properties of cables, such as the length and cross-sectional area, etc., and the amplitude of the vibration for the deck. Therefore, the cables with different physical properties could have different parametric vibration characteristics. The results show that the sag effect of the cable has to be included when the order of deck vibration amplitude is lower than that of the parametric vibration of cable. However, the sag effect can be ignored in short cables with a large inclination angle. Meanwhile, when the external oscillation term has the same order as the quadratic term does, a combination of parametric resonance vibration and sub-harmonic occurs in the cable.