Cable-supported Bridges Research Articles

Improvement of the Performance-Based Seismic Design Method of Cable Supported Bridges with the Resilient-Friction Base Isolation Systems

In areas of civil engineering, the resilient friction base isolator (R-FBI) system has been used due to its enhanced isolation performance under seismic excitations. However, because nonlinear behavior of the R-FBI should be reflected in seismic design, effective stiffness (Keff) of the R-FBI is uniformly applied at both peak ground acceleration (PGA) of 0.08 g and 0.154 g which use a multimodal response spectrum (RS) method analysis. For rational seismic design of bridges, it should be required to evaluate the dynamics of the R-FBI from in-field tests and to improve the seismic design procedure based on the performance level of the bridges. The objective of this study is to evaluate the dynamics of the R-FBI and to suggest the performance-based seismic design method for cable-supported bridges with the R-FBI. From the comparison between the experiments’ results and modal shape analyses, the modal shape analyses using primary (Ku) or infinite stiffness (fixed end) showed a great agreement with the experimental results compared to the application of Keff in the shape analysis. Additionally, the RS or nonlinear time history method analyses by the PGA levels should be applied by reflecting the dynamic characteristics of the R-FBI for the reasonable and efficient seismic design.

Wide Cable-supported Bridges for Rail-cum-road Traffic

This paper reviews and describes experiences and the state-of-art of cable-supported rail-cum-road bridges with box girder. The application range of wide single box girder, vented box girders with two and three separated boxes is analyzed from the point of view of structural behavior, fabrication, transportation, installation depending upon the number of tracks, road lanes and different transversal locations of the pylon legs. Future trends of these bridges for multiple railway tracks and road lanes are discussed. A cable-stayed bridge with a main span of 520 m and three-separated-box-girder with different arrangements of the cable planes has been analyzed in a little more detail. The results reveal that the three-separated-box-girder is an effective solution for long span cable-supported bridges with multiple railway tracks and road lanes.

Aerodynamic and aeroelastic responses of short gap twin-box decks: Box geometry and gap distance dependent surrogate based design

The aerodynamic and aeroelastic performances of twin-box deck bridges are difficult to anticipate when changes in the deck geometry are introduced. Considering moderate changes in the gap distance and in the box geometry, a surrogate model may provide the full picture of the aerodynamic properties, and even the critical flutter speed. In this work the boxes’ width and depth, and the slot between girders, are selected as input of a surrogate model. A set of 25 samples is defined using the Latin Hypercube Sampling method for training the Kriging surrogate, and for these samples, the force coefficients and their slopes are obtained by means of 2D URANS simulations. Force coefficients and flutter derivatives have been obtained experimentally for a subset of three samples. These experimental data have been used to validate the CFD results, finding a good agreement. Furthermore, based upon these experimental results, the values adopted for the aerodynamic centers in the quasi-steady approximation of the flutter derivatives have been corrected, improving their accuracy. Using the quasi-steady formulation, the critical flutter velocity is obtained over the whole design domain, finding that the gap distance and the boxes’ width are very influential in the aeroelastic performance of cable-supported bridges.

Identification of instantaneous tension of bridge cables from dynamic responses: STRICT algorithm and applications

Real-time monitoring of instantaneous cable tension is essential for condition monitoring and health diagnosis of cable-supported bridges. Vibration-based identification of cable tension resting on the relation between the cable tension and the frequency of dynamic responses has been increasingly investigated in the last decade. The extant studies have realized identification of cable tension by in-situ measurement of dynamic responses, whereas monitoring of instantaneous variation of cable tension is a pending issue, not yet well resolved. To address this issue, this study proposes a new algorithm termed Synchrosqueezing short-time Fourier Transform-based Real-time Identification of Cable Tension (STRICT). The STRICT features identification of instantaneous frequencies of dynamic responses from acceleration sensors, facilitating determination of the instantaneous cable tension of bridges. The accuracy and reliability of the proposed method is demonstrated on a 3D finite element model, and its applicability is experimentally validated on the Jiangyin Yangtze River bridge. The numerical and experimental results show that the STRICT algorithm can identify instantaneous cable tension with satisfactory accuracy, providing a new path for monitoring the condition of cable-supported bridges.

Experimental study on seismic control of towers in cable-supported bridges by incorporating fluid viscous dampers between sub-towers

In this article, the seismic control of towers incorporated with fluid viscous dampers between sub-towers is investigated experimentally. To replace one entire tower, an alternative scheme consisting of four separate sub-towers is first proposed. Fluid viscous dampers are utilized as energy dissipation devices to be installed between sub-towers. Experimental tests are conducted to study the damping force characteristics. Three control strategies with various distributions of these dampers between sub-towers are developed. Then, a series of shaking table tests are carried out to evaluate the control performance of the proposed control strategies. Different earthquake records are adopted as seismic loadings. Experimental results clearly show a remarkable reduction in the towers seismic responses, including the accelerations, relative displacements, and strains. Rather than attaching dampers in concentrated ways, the strategy of distributing dampers uniformly behaves better.

Dynamic Characteristics of submerged floating tunnel under irregular waves

submerged floating tunnel (SFT) is an innovative structural solution for waterway crossings and is based on the idea of Archimedes Buoyancy. The main structure is kept at a certain depth underwater and is placed in position by anchor/mooring cables. SFT becomes a more economical alternative for waterways compared to classical solutions such as cable-supported bridge, immersed tunnel or underground tunnel when the width and depth of the waterway are large enough. As SFT is completely submerged in water and is subjected to extreme environmental conditions such as waves, earthquakes, and hurricanes, therefore, the evaluation the dynamic characteristics of an SFT under irregular waves is a key demand from the design point of view. In this study, the responses of an SFT that is to be built in Qindao Lake of China are investigated under irregular waves. A 3D FEM model for SFT was established, the tunnel was modeled by 3D beam elements and cables were modeled by elastic catenary elements. The irregular waves were modeled by JONSWAP spectrum. The time history analysis was performed under irregular waves and currents. The time-domain simulations were transformed to the frequency domain by Fast Fourier Transform (FFT). The spectra were smoothed using Savitzky-Golay smoothing filters. The transfer functions of SFT horizontal and vertical displacements; and cable tensions were obtained for 30 realizations. Two major peaks have been observed in each transfer function (response spectrum). One of the peaks was associated with the peak wave frequency; the second peak was associated with the translational natural frequency of the SFT.

ASSESSMENT OF SEISMIC PERFORMANCE OF SUBMERGED FLOATING TUNNEL UNDER MULTI-SUPPORT SEISMIC EXCITATIONS

Submerged floating tunnel (SFT) is an innovative structural solution for the transportation infrastructure through sea straits, fjords, and inland waters and is an economical alternative to the long-span cable-supported bridge, immersed tunnel, or underground tunnel. An SFT is a massive cylindrical structure that floats at a certain depth below the water surface and subjected to extreme environmental conditions, such as waves, tsunamis and earthquakes. The seismic assessment of SFT supported by mooring cables, under multi-support seismic excitations needs to be evaluated in more detail. The time domain dynamic problem of SFT moored by inclined mooring cables/anchors is formulated and the geometric non-linear dynamic analysis of SFT subjected to hydrodynamic and seismic excitations is performed in this paper. The prototype of SFT to be constructed in Qindao Lake of China is analysed under multi-support seismic excitations. It was found that due to the fluid environment and flexible cables the effective seismic forces are dissipated well and SFT is stable under the spectrum compatible ground motions. However, the lateral component of seismic excitations produce larger responses compared to longitudinal one and may be critical for other case studies.

A multi-scale corrosion fatigue damage model of high-strength bridge wires

Cables are the most sensitive components in cable-supported bridges, and the failure of cables is usually caused by the degradation of mechanical properties of internal wires. Based on Faraday's law and the rates of microcrack initiation and propagation, a multi-scale corrosion fatigue damage model was developed to describe the damage evolution in the stages of pit growth and microcrack propagation. The accuracy and effectiveness of this damage model were also verified through the experimental data of corrosive fatigue life of high-strength bridge wires. The result shows that this damage model can describe the multi-scale corrosion fatigue damage evolution process of high-strength bridge wires reasonably and effectively, which provides a new way to better understand the trans-scale damage evolution mechanism during the corrosion fatigue process of high-strength bridge wires.

Effect of Rotational Restraint at Damper Location on Damping of a Taut Cable with a Viscous Damper

AbstractThe installation of an external damper on a cable of a cable-supported bridge is often associated with attachments or support devices that trigger vibration restraints at the damper locatio...

Temperature Effect on Tension Force of Stay Cable of Cable-Stayed Bridge

Cable is the main element of cable-supported bridge, such as suspension bridge, cable stayed bridge and arch bridge. For the cable-stayed bridge, the cable receives the load from the bridge deck and transfer it to the pylon. As the ambient temperature change, the internal force in bridge element including stayed cable will change. This research investigate the ambient temperature effect to the tension force of stayed cable of cable-stayed bridge by comparing the result of finite element model analysis with the field measurement form electromagnetic sensor data. The finite element model of Merah Putih Cable-Stayed Bridge has been developed based on detailed engineering design data. The finite element model is validated using the natural frequency data from dynamic load test of the bridge. The ambient temperature and bridge elements temperature were measured for 24 hours. The finite element analysis were conducted based on field measurement data and the contribution of pylon and girder temperature to the cable tension forces variation was investigated. The output of finite element analysis then compared to the actual cable tension as measured by an electromagnetic sensor. It was found that the ambient temperature will affecting the magnitude of tension force at stay cable and the variation of cable tension has similar pattern of both from the finite element model and electromagnetic data. As the temperature of bridge element increases or decreases, the bridge will experience a deformation. Since the stay cable connected to the pylon at one side and to the girder at the other side, its will make the stay cable elongated or contracted which in turn will affecting the tension force at stay cable. When evaluating the bridge condition based on the tension force at stay cable, the effect of temperature variation need to be considered.

Research on Wire-Broken Monitoring of Bridge cable based on Acoustic Emission technique

Acoustic emission signals generated by broken prestressed steel strand of cable can transmit up to 29.5 meters without maintaining significant attenuation of the amplitude. Therefore, the installation of a few acoustic emission sensors can comprehensively monitor the damage of the entire prestressed steel strand. Thereby, the detection of unknown defects is realized, and the structural health status can be quantitatively and quantitatively evaluated. In this paper, the acoustic emission technology is used to monitor the damage and fracture of prestressed steel strand under over tension. The acoustic emission technology is used to test the broken wires of cable of a concrete-filled steel tubular arch bridge. The correlation of the broken wires test results of the bridge is qualitatively analysed, including the stress state of the cable, the location of the measuring points and whether there is a PVC sheath at the measuring points. Therefore, a safe, reliable and efficient method is sought to monitor the damage status of the in-service cable-supported bridge.

Parametric Optimization of Orthotropic Girders in a Cable-Supported Bridge

AbstractIn the last six decades, closed-box orthotropic steel girders have been widely used in cable-supported bridges. Several parametric studies were previously carried out to reduce inherent fat...

압축과 휨을 동시에 받는 케이블교량용 광폭 강박스거더의 강도상호작용

압축과 휨을 동시에 받는 케이블교량용 광폭 강박스거더의 강도상호작용

Assessment of the Dynamic Behaviors of Submerged Floating Tunnel Under a High-Speed Train Loading

Submerged floating tunnels (SFTs) are innovative structural solutions to waterway crossings and are more economical compared to the conventional structures such as cable-supported bridges, underground tunnels or immersed tunnels. The dynamic behaviors of SFT under real train loads is the primary design requirement of an SFT, However, it is not investigated using realistic train models. In this study, the China-star high-speed train is used to evaluate the dynamic displacements, internal forces and cable tensions of SFT. The tunnel is modeled by FEM, the cables are modeled by elastic catenary cables, and ocean waves and currents are modeled by Airy’s wave theory. The SFT displacements, bending moments and cable tensions were significantly influenced by moving trains. The SFT experienced extreme vertical displacements and there was a large drop in the minimum cable tensions. The mooring cables were slacked both by magnitudes and speed of the moving trains, which should be avoided for the safety of SFT. This study recommends the additional buoyancies for the stability of SFT subjected to high speed trains.

Real-Time Aerodynamics Hybrid Simulation: A Novel Wind-Tunnel Model for Flexible Bridges

Despite rapid development in computational fluid dynamics, semiempirical analyses based on parameters identified from spring-mounted sectional models are still widely used to examine wind-induced effects on bridges. In addition, wind tunnel results from full-bridge aeroelastic models, viewed as the most comprehensive representations, are typically a final check for wind design of long-span cable-supported bridges. There are several well-known limitations associated with conventional wind tunnel testing of both sectional and full-bridge models. For example, structural nonlinearities and large deformations are difficult to simulate in sectional models, and only a limited number of modes can be accurately simulated in full-bridge aeroelastic models. To advance aeroelastic modeling of flexible bridges in the wind tunnel, a slightly different version of the real-time hybrid simulation (RTHS) techniques, frequently used in various branches of engineering, is developed here. Specifically, the skeleton of the sectional or full-bridge model, characterizing the dynamic properties (e.g., mass, damping, and stiffness of the structure), is numerically simulated using computational structural dynamics, while its skin, characterizing the aerodynamic and aeroelastic properties, is physically modeled in the wind tunnel. Aerodynamic inputs (gusts) are applied directly on the skin in the wind tunnel, while aeroelastic inputs (motions) are represented by the simulation outputs of the bridge skeleton. On the other hand, the dynamic inputs to the bridge skeleton are acquired from the measured forces (and moments) on the bridge skin. The interactions between the skeleton and skin of the bridge are accomplished through a system consisting of sensors, a network of electromagnetic actuators, and controllers. The time history of the wind-induced bridge responses can be obtained at the end of the proposed real-time aerodynamics hybrid simulation (RTAHS). The feasibility of the RTAHS methodology is demonstrated by a numerical example involving both linear and nonlinear wind-induced forces on the bridge deck.

Experimental Investigation on a Cable Structure Equipped with an Electrodynamic Damper and Its Monitoring Strategy through Energy Harvesting.

The vibration of cables in a cable-supported bridge affects its serviceability and safety. Therefore, cable dampers are essential for vibration control, monitoring, and the further maintenance of such bridges. In this study, the vibration control performance of an electrodynamic damper applied to a cable used in a footbridge was experimentally verified considering the major design variables of the damper. The damping performance was analyzed by varying the damping ratio according to the excitation condition and external circuit resistance. The acceleration and displacement at each measurement point and the frequency-domain response decreased. Considering the dominant response conditions of the cables in the bridge, an effective additional attenuation was observed. In addition, the harvesting power considering the measurement frequency and power loss was sufficient to operate a wireless measuring sensor by examining the energy harvesting performance from the cable measurement data of an actual bridge in service. Finally, a stepwise operation strategy for a cable vibration monitoring system was suggested and examined by analyzing the meteorological observation data and the power output according to the wind environment. The results demonstrate the feasibility of using an electrodynamic damper to build an integrated monitoring system capable of simultaneous cable vibration reduction and energy harvesting.

Cable Surface for the Reduction of Risk Associated with Bridge Cable Ice Accretions

Cable-supported bridges can suffer from ice and snow accretions that develop in specific weather conditions, predominantly in cold climate regions. As shedding pieces of ice and snow can be of considerable size and weight, they may pose a significant hazard for the traffic below. Numerous anti-icing and de-icing technologies have been tested in laboratories as well as on bridges, but none have proven able to effectively mitigate the risk. Solution durability has also often proven to be lacking. In this paper, a recently developed cable surface that can effectively reduce the risk associated with ice and snow shedding is presented. Experimental results and statistical comparisons between two different cable surfaces in ice shedding tests performed in a climatic wind tunnel are shown. The performance of a conventional, helically-filleted, HDPE stay pipe is compared to that of the innovative stay pipe with a concave-filleted surface. Based on the tests, it is shown that the concave-filleted surface significantly outperforms the contemporary cable surface in terms of the duration for which ice is retained on its surface. This reduces the size and mass of shed ice fragments through prolonged melting, thus reducing the risk associated with it.

A combined method for instantaneous frequency identification in low frequency structures

Civil engineering structures such as high-rise buildings and long-span cable-supported bridges usually exhibit low-frequency characteristics and the resultant response signals may be non-asymptotic (the amplitude change rate is higher than its phase change rate) and even have closely-spaced frequency components. The identification of satisfactory instantaneous frequencies of such response signals is a challenge faced by standard synchrosqueezing wavelet transform. The paper aims to propose a combined method to address this challenge. The proposed method combines an extended analytical mode decomposition (AMD) method, a recursive Hilbert transform and a zoom synchrosqueezing wavelet transform (consisting of frequency-shift operation and partial zoom synchrosqueezing operation). In the method, a multi-component signal, which may consist of closely spaced frequency components, is firstly decomposed into several mono-component signals by the extended AMD, and the extracted mono-components are then demodulated into asymptotic signals by recursively using the Hilbert transform. After that, a frequency-shift operation is employed to improve time resolution and a partial zoom synchrosqueezing operation is then applied to improve the frequency resolution in the narrow low frequency range of interest. Two numerical examples, an experiment on an aluminum cantilever beam with abrupt mass reduction and an experiment on a cable with time-varying tension forces are provided to illustrate the effectiveness, accuracy and robustness of the method.

Buffeting-induced stress analysis of long-span twin-box-beck bridges based on POD pressure modes

Buffeting-induced stress analysis is imperative for the assessment of local failure and fatigue damage of long-span cable-supported bridges located in strong wind regions. This paper presents a new framework for buffeting-induced stress analysis of long-span twin-box-deck bridges based on the pressure modes obtained from the proper orthogonal decomposition (POD) of wind-induced fluctuating pressures and the substructure-based finite element (FE) model of the bridge. Distributed aerodynamic and aeroelastic pressures on the surface of the twin-box deck are modelled in terms of POD pressure modes. The substructure modelling scheme is adopted to construct the FE model of the bridge so that POD pressure modes can be applied and both global (displacement and acceleration) and local (stress) responses of the bridge can be captured simultaneously and accurately. The pseudo-excitation method is used to solve the governing equations for buffeting-induced stress analysis in the frequency domain. The Stonecutters cable-stayed bridge of a twin-box deck under Typhoon Hato is selected to examine the feasibility and accuracy of the proposed framework, in which the global and local responses of the bridge under Typhoon Hato are computed using the proposed framework and compared with the measured ones recorded by the wind and structural health monitoring system installed in the bridge. The comparative results show a good agreement between the computed and measured responses and confirm the necessity of the proposed framework for buffeting-induced stress analysis.

Proposal of Disaster Management Criteria of Seismic Accelerometers Installed on the Primary Structural Elements of Cable-Supported Bridges Based on Long-Term Data

This study presents a proposal of disaster management criteria of seismic accelerometers installed on primary structural elements of cable-supported bridges. Extreme value distributions of accelerations are estimated with respect to 1 month of a reference time period based on a statistical estimation method that uses the long-term records of acceleration measured at the target cable-supported bridges. Extreme value distributions of the acceleration with respect to reference time periods of 100 years and 1000 years are extrapolated by applying extreme value theory, and the disaster management criteria are proposed based on the mean values of the estimated extreme value distributions of the acceleration. The validity of the proposed disaster management criteria is verified through comparison with the peak values of recorded accelerations during the Gyeongju and Pohang earthquakes. Keywords: Cable-supported Bridge, Seismic Accelerometers, Disaster Management Criteria, Extreme Value Distributions