Large Span Cable-stayed Bridge Research Articles

Performance Evaluation of Inerter and Negative Stiffness-Based Dampers for Seismic-Induced Vibration Response Control of a Cable-Stayed Bridge: A Comparative Study

The excessive main girder displacement responses of the large-span cable-stayed bridges during seismic events may precipitate collisions between the main girder and the approach bridge. The viscous dampers (VDs) have been extensively employed in the seismic response control of long-span bridges, yet their effectiveness is limited. To augment the seismic-induced vibration control performance of the VD, inerter element, negative stiffness (NS) element, and spring element have been incorporated into the VD to achieve energy dissipation capacity enhancement. The equations of motion for the simplified cable-stayed bridge-damper systems are established under stochastic seismic excitation, and the design parameters of inerter and NS-based damper are optimized by using the genetic algorithm. The seismic control performance of the VD and five types of dampers are systematically compared, demonstrating that these dampers can substantially enhance the main girder displacement mitigation performance in cable-stayed bridges. Owing to the NS characteristics attributes of the inerter element and NS element and the tuning effect of the spring element, the tuned viscous mass damper (TVMD) with NS achieves a 24.56% higher efficiency in control performance compared to the VD.

Anomaly detection for bridge health monitoring data based on multiple encoded images and convolutional neural network

In bridge health monitoring systems, abnormal monitoring data inevitably appear due to the complex operational conditions, and these anomalous data will seriously affect the accuracy and reliability of the results of bridge health assessment. Hence, it is vital to detect the abnormal data before further processing. However, the pattern diversity and sample scarcity usually make the accuracy of data anomaly detection unsatisfactory. A novel anomaly detection method for bridge health monitoring data based on encoded images and convolutional neural network (CNN) is proposed in this paper. First, the raw time series are encoded into images to highlight the intrinsic features in the anomaly data, and multiple encoding techniques are adopted to represent the data in different perspectives. Then, the CNN is utilized to establish the mapping between the encoded images and the anomaly patterns for achieving the data anomaly detection. At last, the proposed method is verified with the acceleration data measured from an actual large span cable-stayed bridge. It shows that the proposed method can significantly improve the performance of data anomaly detection while the results are hardly affected by the small sample sizes, and a detection accuracy of over 95% is achieved based on the multiple encoded images.

Fast Cable-Force Measurement for Large-Span Cable-Stayed Bridges Based on the Alignment Recognition Method and Smartphone-Captured Video

The accurate measurement of cable force plays an important role in the structural form, structural behavior, and safety evaluation of large-span cable-stayed bridges. A fast cable-force estimation method is proposed based on the alignment recognition method and smartphone-captured video. This method can realize real-time, non-contact, and non-destructive force measurements. Videos of bridge cables were collected using a portable smartphone, and an alignment recognition method was employed to obtain the lateral displacement along the cable, followed by numerical differentiation of the lateral displacement of the cable to acquire the acceleration time history. Based on the fundamental dynamic equation of beam elements, a unified explicit formula for cable-force calculation considering service characteristics was established in the frequency method. Finally, the method was applied to the cable-force measurement during the operation and maintenance stage of the Gengcun Dou Bridge. The measured cable forces were compared with the values obtained from the on-site monitoring system. The results show that the proposed method can accurately identify the acceleration time history at different positions of the cable, and the corresponding frequency components are essentially consistent. The average relative deviation of the measured cable forces from the reference method is within 3%. The proposed cable-force measurement method is simple as regards equipment, convenient for operation, and high in efficiency, providing a new method for the measurement of cable forces in large-span cable-stayed bridges, which can offer reliable measured cable-force data for structural analysis during bridge operation and the maintenance stage.

Mechanical behavior improving study of concrete deck of main beam at pylon root of composite beam cable-stayed bridge

Steel-concrete composite beam has been increasingly applied to large span cable-stayed bridges. It takes full advantage of the material properties of steel and concrete. However, the concrete deck bears tension in the negative moment zone, such as zero block, which is disadvantageous to structures. Aiming at this problem, a finite element model of the zero block in the negative moment zone of a semi-floating cable-stayed bridge is built, and the local mechanical performance of the bridge deck under completed status is studied. Based on the analysis results, three improvement measures have been proposed. The improvement effect of each method and composed of three methods has been studied. The numerical results show that the whole zero block zone is in the compressed state under the combined action of the bending moment and axial force of the stay cable. However, the local negative moment effect in the zero block zone is very prominent under the support of the diaphragm plate. Removing parts of the diaphragm plate at the bearing position can significantly improve local mechanical behavior in the concrete deck, which transfers the local support to the adjacent two diaphragm plates. The composed improvement effect is prominent when the three measures are adopted simultaneously.

Investigating parameters and ultimate load-bearing performance of novel anchor-box type cable–girder anchoring structure for large-span cable-stayed bridges

This study combined experimental research and finite element numerical simulations to investigate the ultimate bearing performance of a novel anchor-box-type cable–girder anchorage structure for large-span cable-stayed bridges. The stress distribution and deformation in the structure was assessed under varying loads, and the effects of the construction parameters on peak stress in key load-bearing welds were analyzed. The proposed design exhibits a safety margin of 3.2. The simulated and experimental stress distributions agree well with experimental data, although deformation and load-bearing capacity results are non-conservative. The maximum stress in the main load-bearing welds exhibits an exponential relationship with construction parameters.

Research on the Influence of Geotextile and Elastic Cushion on the Static Performance of Ballastless Track on Long-Span Cable-Stayed Bridges

The elastic cushion is mostly used between the layers of ballastless tracks laid on a large-span cable-stayed bridge with a main span of more than 300 m. The rubber material is easy to harden and age, the geotextile has good acid-alkali resistance and antiwear performance, and the feasibility of geotextile application on the large-span cable-stayed bridge can be explored. The coupling model of a long-span cable-stayed bridge and the ballastless track was established to analyze the longitudinal mechanical characteristics of the seamless line, the deformation of the track structure, and the separation of the track plate and base plate under different loads. The results show that the application of geotextile or elastic cushion has little effect on the longitudinal mechanical properties of seamless lines. Compared to the elastic cushion, laying the geotextile increases the longitudinal stress of the slab by 0.13 Mpa, 0.025 Mpa, and 0.06 Mpa under different types of loads. The strength calculation of the seamless track is within the safety range. Laying elastic cushion can restrain the generation of separation under vertical loads, but there is no effect laying elastic cushion under temperature loads and braking loads, and the height of separation was less than 0.4 mm. The stress and deformation of the ballastless track do not exceed the standard when applying geotextile; it is feasible to apply geotextile on ballastless tracks on a large-span cable-stayed bridge. The next step is to study the vehicle–bridge–track dynamic response when elastic cushion and geotextile are laid.

Correlation Analysis of Large-Span Cable-Stayed Bridge Structural Frequencies with Environmental Factors Based on Support Vector Regression

The dynamic characteristics of bridge structures are influenced by various environmental factors, and exploring the impact of environmental temperature and humidity on structural modal parameters is of great significance for structural health assessment. This paper utilized the Covariance-Driven Stochastic Subspace Identification method (SSI-COV) and clustering algorithms to identify modal frequencies from four months of acceleration data collected from the health monitoring system of the Jintang Hantan Twin-Island Bridge. Furthermore, a correlation analysis is conducted to examine the relationship between higher-order frequency and environmental factors, including temperature and humidity. Subsequently, a Support Vector Machine Regression (SVR) model is employed to analyze the effects of environmental temperature on structural modal frequencies. This study has obtained the following conclusions: 1. Correlation analysis revealed that temperature is the primary influencing factor in frequency variations. Frequency exhibited a strong linear correlation with temperature and little correlation with humidity. 2. SVR regression analysis was performed on frequency and temperature, and an evaluation of the fitting residuals was conducted. The model effectively fit the sample data and provided reliable predictive results. 3. The original structural frequencies underwent smoothing, eliminating the influence of temperature-induced frequency data generated by the SVR model. After eliminating the temperature effects, the fluctuations in frequency within a 24 h period significantly decreased. The data presented in this paper can serve as a reference for further health assessments of similar bridge structures.

Probabilistic anomaly detection considering multi-level uncertainties for cable-stayed bridges

To model multi-level uncertainties within anomaly detection process for large-span bridges, a probabilistic anomaly detection method is proposed considering uncertain models in the data collection, thermal response separation, and trigger estimation. The uncertain model in the data collection is established with the measured value and measuring errors. The uncertain model in the thermal response separation is built through the linear Bayesian estimation. The uncertain distribution of the anomaly detection trigger is obtained via Bayesian estimation of generalized Pareto distribution. Subsequently, measurements from multi-sensors are used to detect anomalies in a probabilistic way. Evidential reasoning, a decision-level fusion tool, is used to derive a collective detection rate to distinguish sensor malfunctions from anomalous scenarios. Specifically, anomalous scenarios deserve a large collective detection rate, whilst sensor malfunctions are subject to a small collective detection rate and a large individual detection rate. Two cases (i.e., sensor malfunction and snow disaster) are illustrated based on measurements from a large span cable-stayed bridge. As a result, the sensor malfunction is detected with an individual detection rate of 89.20% and a collective detection rate of 2.77%. The snowstorm is detected by a collective detection rate of almost 100%.

Research on the Overall and Local Mechanical Behaviors of Steel Box Girder Cable-Stayed Bridge via Incremental Launching Construction

In this paper, a large-span cable-stayed bridge with double pylons and double cable planes is employed to study the overall and local mechanical behaviors. The steel box girder bridge is constructed by incremental launching with the maximum span of 50 m. Through the overall stress analysis, the most unfavorable stress position of the structure in the incremental launching construction is identified; the refined local stress analysis is carried out for the girder section at this position, and the local stress characteristics of the structure are studied. The mechanical performance and the applicability of incremental launching are determined by comparing four kinds of elastic cushion. This paper aims at improving the safety of incremental launching construction of steel box girder bridge, and can provide reference for similar projects.

Vision-based multi-point real-time monitoring of dynamic displacement of large-span cable-stayed bridges

The existing vision measurement methods face a significant challenge in the multi-point displacement monitoring of large-span bridges due to the contradiction between the measurement scale and image spatial resolution. Based on a cable-stayed bridge on a kilometer scale, a new vision-based multi-point displacement monitoring system is proposed. The bridge was designed and arranged with a camera network, consisting of a series of double-head camera stations that were connected by cooperative markers. Based on the observed multi-point deflection and lateral displacement, the deformation evolution of the bridge in the two dimensions of time and space is discussed. The results show that the proposed vision-based camera network can accurately monitor the dynamic deflection and lateral displacement across the whole span of the bridge. The measurement errors induced by the camera motion can be well compensated based on the optical constraints of the proposed camera network. The feasibility of the vision method for long-span bridge monitoring has greatly improved. The proposed system can provide a new method for displacement monitoring and fine parameters for the safety evaluation of large-span bridges.

Design and key construction technology of steel-concrete-steel sandwich composite pylon for a large span cable-stayed bridge

This paper introduces a new type of steel-concrete composite pylon that has been applied to Nanjing Fifth Yangtze River Bridge (a three-pylon cable-stayed bridge with a main span of 600 m). For this new type of pylon, the steel shells are connected with concrete through PBL shear connectors and studs, and the inner steel shells are connected with the outer steel shells by angle steels. Numerical analysis and full-scale model tests show that the pylon structure exhibits excellent mechanical properties and construction performance. The application of BIM technology, the research and development of special spreaders and construction platforms ensure the precise installation of structures. Highly factory-manufactured modular assembly of the reinforced steel shell structure can effectively reduce the intensity and difficulty of on-site operations, and improve the quality of the project, with low construction risks. Whereas, the successful application of this steel-concrete-steel sandwich composite pylon marks the formation of a complete set of construction technology of steel-concrete-steel sandwich composite pylon, which can be widely used in similar bridges.

Static Experimental Study on New Arc Multi-Tendon CFRP Cable Anchorage System

CFRP has the potential to replace steel cables in large-span cable-stayed bridges due to its high strength and lightweight material properties. However, the weak lateral force performance of CFRP material creates the challenge of anchoring. This study introduces a new inner cone + arc + straight cylinder bond-type anchorage system to optimize CFRP tendons’ force state. Experimental and finite element analyses verified the new anchoring system’s performance. In static load tensile tests, six groups of seven CFRP tendon anchorage systems with different sleeve grooves were used to study the failure mode and load–strain variation law. The difference in mechanical properties between the new and traditional anchorage is evaluated in the finite element analysis. The results indicate that the new anchorage system can lower the stress concentration in the anchorage zone and enhance anchorage performance. The groove design of the sleeve can effectively increase the anchoring efficiency, where the groove depth is proportional to the anchoring efficiency and the groove spacing is inversely proportional to the anchoring efficiency. The magnitude of the stress inhomogeneity in the multi-tendon anchoring system during tensioning is proportional to the beginning conditions and the load size. When the inner wall of the sleeve becomes more abrasive, the force heterogeneity of the anchorage system reduces. The tests and finite element analysis show that the new anchoring may improve stress distribution and anchorage efficiency. In engineering practice, it can be utilized as a dependable anchorage system.

A deep leaning method for dynamic vibration analysis of bridges subjected to uniform seismic excitation

The seismic response of a nonlinear, large-span cable-stayed bridge is a key problem in the assessment of structural safety. We propose an optimized deep learning network to study the random vibration of an uncertain bridge subjected to an earthquake. The dynamic formulas of the uncertain system were produced by transient analysis in the time domain to construct a numerical model comprising two functional modules: convolutional neural network (CNN) training with input rail irregularities and a long short-term memory (LSTM) layer for the bridge response time-history prediction. The LSTM cell was simulated by introducing the randomness of excitation and uncertain characteristics of parameters of the system into a portion of the cell, enabling the numerical model to convey the uncertainties of the bridge and obtained its stochastic response. The seismic response of railroad cable-stayed bridges under ground motion was calculated using the proposed method, taking into account the geometric nonlinearity of the bridges, and its accuracy and validity were verified. The effects of the distribution state of the seismic response samples, traveling wave effects, and intensity of the seismic spectrum were investigated, and the extremes of responses were analyzed based on Poisson's crossover assumption.

Shear lag effect of composite girders in cable-stayed bridges under dead loads

The shear lag effect is a common phenomenon among civil infrastructures, which is also a critical issue for composite girders. For composite girders in large-span cable-stayed bridges, there is a large proportion of internal forces caused by dead loads, and the shear lag effect of the concrete slab under dead loads is significant. To investigate the normal stress distribution at the construction and service stages, systematic in-situ stress monitoring of composite girders was performed on a cable-stayed bridge under dead loads. Then, the finite element models were built for numerical modeling. The theoretical analysis model was proposed to evaluate the shear lag effect of composite cable-stayed bridges under dead load. Then the law of the stress ratio and the shear lag effect was analyzed by contrasting the test data and simulation results. Meanwhile, the calibrated FE models were used to do the full-scale parametric analysis of the factors including span length, slab width, and cable spacing. The results show that the main girder segment near the bridge tower and the mid-span are critical sections at the construction and service stages for analyzing the shear lag effect. The cable spacing and slab width are the main factors affecting the shear lag effect under dead loads. The effective width coefficients are positively correlated with the stress ratio.

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.

Effect of reverse bending deformation of large-spancable-stayed bridge on ballastless tracks' behaviors

Laying ballastless tracks on large-span cable-stayed bridge is a new challenge, and it is particularly important due to the obvious advantages of ballastless track and the high requirements of high-speed railways. Under the complex load conditions in service, cable-stayed bridges have a variety of beam local deformations, and they inevitably affect the performances of the ballastless tracks laid on the bridge. In this work, a series of experimental studies and FEM simulations are carried out based on a large-span cable-stayed bridge and its segmental model. The main conclusions include: Under the most unfavorable reverse bending deformation of the large-span cable-stayed bridge, tensile and compressive deformations occurred at interlayers of the ballastless tracks with different isolation layers. The interlayer deformation variations of the ballastless tracks with EPDM or geotextile isolation layers are the same, and the deformation values of the ballastless tracks with EPDM isolation layers are larger than that of the ballastless tracks with geotextile isolation layers. However, due to the pre-compression of the EPDM isolation layer subjected to its upper structures' deadweight, it can reduce the influences of the reverse bending deformation on the ballastless tracks, and the gaps and voids at ballastless track interlayers can be avoided. Furthermore, the 5.92 m length ballastless tracks with EPDM isolation layer is recommended to apply on the large-span cable-stayed bridge in high-speed railway to ensure the reliability and durability of the ballastless tracks.

Research on the Overall and Local Mechanical Behaviors of Steel Box Girder Cable-Stayed Bridge via Incremental Launching Construction

<p>In this paper, a large-span cable-stayed bridge with double pylons and double cable planes is employed to study the overall and local mechanical behaviors. The steel box girder bridge is constructed by incremental launching with the maximum span of 50 m. Through the overall stress analysis, the most unfavorable stress position of the structure in the incremental launching construction is identified; the refined local stress analysis is carried out for the girder section at this position, and the local stress characteristics of the structure are studied. The mechanical performance and the applicability of incremental launching are determined by comparing four kinds of elastic cushion. This paper aims at improving the safety of incremental launching construction of steel box girder bridge, and can provide reference for similar projects.</p>

Simplified analysis of cable-stayed bridges with longitudinal viscous dampers

PurposeViscous dampers are commonly used in large span cable-stayed bridges to mitigate seismic effects and have achieved great success.Design/methodology/approachHowever, the nonlinear analysis on damper parameters is usually computational intensive and nonobjective. To address these issues, this paper proposes a simplified method to determine the viscous damper parameters for double-tower cable-stayed bridges. An empirical formula of the equivalent damping ratio of viscous dampers is established through decoupling nonclassical damping structures and linearization of nonlinear viscous dampers. Shaking table tests are conducted to verify the feasibility of the proposed method. Moreover, this simplified method has been proved in long-span cable-stayed bridges.FindingsThe feasibility of this method is verified by the simplified model shaking table test. This simplified method for determining the parameters of viscous dampers is verified in cable-stayed bridges with different spans.Originality/valueThis simplified method has been validated in cable-stayed bridges with various spans.

Reliability Analysis of Large Span Cable-stayed Bridges Based on Support Vector Machine

a method of combining the support vector machine and the intelligent algorithm to perform reliability analysis on large span cable-stayed bridges was proposed in this paper. The algorithm is verified by an example, which shows that the algorithm has higher precision and can be extended to the actual project. Therefore, this paper takes Jiangmen North Street Waterway Bridge as the engineering background, uses the finite element software ANSYS to establish the cable-stayed bridge model and MATLAB software to compile the intelligent algorithm and data processing. It mainly analyzes the reliability of the main beam mid-span deflection, the cable stress and main tower stress of the North Street Waterway Bridge. Finally, the general limit range method is used to estimate the reliability index of the North Street waterway bridge structure system. The results show that the cable stay failure has the greatest impact on the reliability of the entire structural system, so it is necessary to pay attention to the maintenance and monitoring of stay cables.

Optimal layout of sensors in large-span cable-stayed bridges subjected to moving vehicular loads

To obtain the health status of long-span cable-stayed bridges, multiple sensors are applied to the health monitoring system for data collection. The optimal layout of sensors that aims to obtain as much structural information as possible with fewer sensors is important to ensure the effectiveness of the health monitoring system. Sensors are usually placed in typical locations where the structural response is obvious, and most studies utilize static response for the determination of sensor location. In fact, bridges primarily suffer the dynamic load, of which the response has a significant impact on the structural health. In this article, an optimal sensor layout method for a long-span cable-stayed bridge based on dynamic response is proposed under the consideration of vehicle–bridge coupled vibration. With vehicle load applied onto different lanes, the dynamic responses of different bridge members are obtained, and the number and the location of cable force sensors are determined according to the distribution of cable dynamic coefficient DC, and the number and the location of displacement and strain sensors are determined according to the distribution of DGD and DGM, which are the dynamic load allowance for girder deflection and bending moment, respectively. The results prove that this method can reduce the number of sensors effectively and obtain bridge state information more perfectly.