Dongting Lake Bridge Research Articles

Characteristic analysis of rain-wind induced stay-cable vibration based on friction damper in field observation

Abstract Both domestic and foreign scholars have developed various friction dampers with good characteristics. The primary types of friction dampers include conventional friction dampers, Pall friction dampers, Sumitomo friction dampers, and Centripetal friction dampers. The components of these dampers will slip or deform under load effect when the energy is consumed by friction. As the structural vibration period increases while the external energy input decreases, the vibration amplitude is reduced. This vibration reduction method is widely used in the automotive industry. Most of the hysteresis models of dampers are similar to rectangular shapes, making the selection of an accurate initial sliding force crucial for the rectangular hysteresis model. Based on the effective data collected from the field observation test, a self-made friction damper, which has a good vibration reduction effect, was used to observe rain-wind induced stay-cable vibration at Dongting Lake Bridge in Yueyang, Hunan Province. Accordingly, some suggestions are put forward for the research work on rain-wind-induced vibration.

Damping enhancement of nodal modes for stay cables using a single-sided pounding tuned mass damper (SS-PTMD)

Extra long stay cables, owned characteristics of light weight and low damping, may produce large-amplitude vibrations in modes with relatively high frequencies under a moderate wind speed. Installing a transverse fluid viscous damper near the cable anchorage to add maximum damping to the first few cable modes is a traditional method to improve the cable modal damping ratio. However, the installation location of the damper may be coincide with the nodal point of some high vibration modes, and diminishing the damping effect to a large extent. To tackle this nodal mode issue, a single-sided pounding tuned mass damper (SS-PTMD), which exhibits superior control performance over a conventional tuned mass damper (TMD), is adopted to enhance the damping ratio of nodal modes. The coupled equations of motion of a cable equipped with a SS-PTMD are established, and impact force between damper mass and the cable are considered by a impact force model. Free pounding tests are performed to study the pounding behavior with different viscoelastic (VE) material layers and various types of pounding strikers. Numerical simulations are carried out to investigate the damping enhancement and vibration mitigation effect of the SS-PTMD on the cable under various loading cases, including harmonic and simulated turbulent wind excitations. Field performance validations of the SS-PTMD is performed on a cable numbered A10 of the Dongting Lake Bridge. The results from free pounding tests show that the selection of the VE material layers and strikers can greatly affect the pounding behavior of the SS-PTMD. The Numerical simulation of the coupled cable-SS-PTMD system reveals that the SS-PTMD can effectively enhance the damping ratio of the target mode by a SS-PTMD with only 1.08% mass ratio. The numerical results show that SS-PTMD is effective in mitigating the high-oder nodal mode vibration of the cable. Field tests show that after the installation of SS-PTMD, the 2nd-mode modal damping ratio of the cable increases from 0.15% to 1.8%.

Dynamic responses and fatigue assessment of OSD in heavy-haul railway bridges

With increasing freight volume and speed in heavy-haul railways, the impact of train loads on the orthotropic steel deck (OSD) has significantly increased, resulting in fatigue damage of bridges. In this study, the dynamic responses and fatigue assessment of OSD in heavy-haul railway bridges were carried out based on a coupled train-track-bridge analysis and hot spot stress (HSS) method. First, using Dongting Lake Bridge on Hao-Ji Railway as an example, a finite element (FE) model of OSD was established. Then, a simplified method of train loads is proposed to improve the calculation efficiency. The dynamic response results from the coupled train-track-bridge analysis and the moving train load method were compared. The most fatigue-prone detail was determined to be the rib-diaphragm joint weld at the notch. Subsequently, the HSS results of OSD for different scenarios were compared and analyzed. Moreover, the fatigue life of OSD was obtained. Due to multiple stress cycles and large local stresses caused by the heavy-haul train load, the fatigue life of OSD fatigue-prone detail is estimated to be 25.74 years. Finally, the effects of different parameters (e.g., axle weight, train speed, and track irregularity) on the fatigue life of OSD were analyzed. This study provides a reference for the design and evaluation of OSD in heavy-haul railway bridges.

Mechanical characteristics analysis of the orthotropic steel deck in heavy-haul railway bridges

This paper aims to assess the mechanical characteristics of the orthotropic steel deck (OSD) in heavy-haul railway bridges. Taking the Dongting Lake Bridge as an example, to simulate the transfer effect of the track structure and get mechanical characteristics of the OSD under the service load, the refined segmental finite element model (FEM) of the OSD in a heavy-haul railway bridge was established. Moreover, the Chinese C80 heavy-haul train (the C80) was selected as the applied load to make the analysis results close to the actual situation. And then, the stress influence lines of critical components in OSD were analyzed. Notches at diaphragms of the OSD are more likely to produce stress concentration. Due to the dense distribution and high stiffness of the longitudinal ribs of OSD, the final load influence range of OSD is limited. Since the T-shaped longitudinal ribs (T-Ribs) are located under the position of each rail, and its stiffness is greater than the adjacent U-shaped longitudinal ribs (U-Ribs), so that the T-Ribs are important load-bearing components of the OSD in heavy-haul railway bridges. Furthermore, the influences of the stiffness ratio of T-Rib to U-Rib on the mechanical characteristics of the OSD were analyzed.

Practice Research on Flat Streamlined Steel Box Girder Technology of Dongting Lake Bridge

Practice Research on Flat Streamlined Steel Box Girder Technology of Dongting Lake Bridge

Form Finding and Aesthetic Design for Pylons of Cable-supported Bridges

Pylons of cable-supported bridges are especially important components. They are generally large in scale and bear the main loads of the bridge, involving requirements both in structural performance and aesthetics. In this paper, a new form finding method for the pylon is proposed, with the use of bi-directional evolutionary structural optimization (BESO) method and the application of aesthetic rules. The principle of BESO method and the process for the form finding of the pylon are discussed. Pylons of the Hangrui Dongting Lake Bridge and the 3rd Panama Canal Bridge are used as cases to illustrate the proposed method. These two bridges are a suspension and a cable-stayed bridge with a main span of 1480 m and 530 m, respectively. The Golden-section and the Rectangle-division methods, together with the morphologic feature from local culture, are used to achieve harmony between the bridge and the environment. It is shown that the requirements mentioned above can be more easily achieved with the proposed method as well as some aesthetic rules.

Time Series Deformation Monitoring over Large Infrastructures around Dongting Lake Using X‐Band PSI with a Combined Thermal Expansion and Seasonal Model

The long‐term spatial‐temporal deformation monitoring of densely distributed infrastructures near the lake area is of great significance to understand the urban health status and prevent the potential traffic safety problems. In this paper, the permanent scatterer interferometry (PSI) technology with TerraSAR‐X imagery over the area around Dongting Lake was utilized to generate the long‐term spatial‐temporal deformation. Since the X‐band SAR interferometric phases are highly influenced by the thermal dilation of the observed objects, and the deformation of large infrastructures are highly related to external temperature, a combined deformation model considering the thermal expansion and the seasonal environmental factors was proposed to model the temporal variations of the deformation. The time series deformation and the thermal dilation parameter over the area were obtained, and a comparative study with the traditional linear model was conducted. The Dongting Lake Bridge and the typical feature points distributed around the lake were analyzed in details. In order to compensate for the unavailability of external in situ measurements over the area, phase residuals and the subsidence generated through Differential Interferometric Synthetic Aperture Radar (D‐InSAR) were utilized to verify the accuracy of the obtained deformation time series. Experiment results suggested that the proposed model is suitable and suggested for the selected study site. The root mean square error (RMSE) of the residual phase was estimated as 0.32 rad, and the RMSE compared with D‐InSAR derived deformation was ±1.1 mm.

Design of high performance concrete with multiple performance requirements for #2 Dongting Lake Bridge

Proper mixture design of concrete is of great significance for the quality of the concrete materials and structures. For #2 Dongting Lake Bridge in China, several performance requirements were required for designed concrete mixtures, including compressive strength, drying shrinkage, cracking resistance, alkali-aggregate reaction, permeability, and carbonation resistance. In this study, a mixture design method of concrete with multiple performance requirements was used to design C55 concrete for the project. The relationships between cement-fly ash-slag ternary cementitious composition and different properties were established based on the seven-batch factorial design method. Based on the requirements for different properties, a composition range meeting all requirements could be obtained. The verification tests showed that the designed mixture was suitable for the construction of #2 Dongting Lake Bridge.

Fatigue Performance of a Lightweight Composite Bridge Deck with Open Ribs

An innovative lightweight composite deck (LWCD) is proposed for steel bridges to avoid premature fatigue cracking. The composite deck is composed of an open-ribbed orthotropic steel deck (OSD) and a thin ultrahigh-performance concrete (UHPC) layer. This study is based on a suspension steel bridge in China, namely, the Second Dongting Lake Bridge. The following investigations were performed: (1) preliminary finite-element analysis (FEA) was carried out to evaluate the vehicle-induced stress ranges (i.e., Δσ = σmax − σmin) of six typical fatigue-prone details; (2) parameter analyses were performed to investigate the effects of the shape of cutouts and the thickness of the floor beams; and (3) two fatigue tests, one that used a full-scale LWCD panel and another that used a LWCD beam specimen, were conducted to reveal fatigue performance of the OSD and the stud shear connectors, respectively. Results of the preliminary FEA show that, with the contribution of the UHPC layer, the vehicle-induced stress ranges at some fatigue details of the LWCD, such as the rib–deck plate welded joints and the splice welds of the longitudinal ribs, were reduced to be less than their constant-amplitude fatigue limits, which indicates theoretically infinite fatigue lives of these details. The parameter analyses reveal that the apple-shaped cutout had relative good fatigue properties among the four cutout schemes and that the thickness of the floor beams is recommended to be 14–18 mm. According to the fatigue tests on the composite panel specimen and on the composite beam specimen, both the open-ribbed OSD and the stud shear connectors exhibited satisfactory fatigue endurances, which were much greater than 2 million cycles. The current theoretical and experimental investigations reveal that the proposed open-ribbed LWCD has favorable fatigue performances.

Correction Method of Cable Tension Measurement Bases on the Principle of Hamilton

In order to improve the accuracy of cable tension test, the motionequation of the stay cable with the rubber damper was established bases on the principleof Hamilton. First, the correction method for the damping coefficient of rubberdamper and cable tension was proposed according to the higher modal frequencyand measured frequency of cables difference. Then, take the cable of DongtingLake Bridge as an example, the cable tension was calculated by the proposedmethod and compared with the results of measurement by frequency method.Results showed that the proposed method can improve the accuracy of cabletension test and can effectively evaluate the cable tension condition of thecable-stayed bridge.

Influence of Central Buckle on Dynamic Behavior of Long-Span Suspension Bridge with Deck-Truss Composite Stiffening Girder

A 3-D finite element model for Yueyang Dongting Lake bridge was established with a large scale general finite element analysis software, and the subspace iteration method was adopted to analyze the natural vibration characteristics of the bridge, meanwhile, the influences of settings different types of central buckles at the mid-span of the main spans between the main cables and girder on the dynamic behaviors of the long-span suspension bridge with deck-truss composite stiffening girder were studied. The results show that compared with only setting short hanger cable at mid-span, the the whole rigidity of suspension bridge is raised and the natural frequencies increase by the setting central buckle, but various types of vibration modes are affected in different extents; among all of these vibration modes, the antisymmetric vibration and Longitudinal floating of stiffening girder are most obviously affected. The stiffness of central buckle has a great influence on the vibration of main cable, while compared with only setting short hanger cable, the vibration of main cable increases 7.32% while setting the rigid central buckle. The conclusions of this paper provide theoretical basis for the using of central buckle in long-span suspension bridge.

NONSTATIONARITY ANALYSIS IN WIND-RAIN-INDUCED VIBRATION OF STAY CABLES

Wind and wind-rain-induced cable vibration are usually nonstationary. Based on the field measured wind data from the Dongting Lake Bridge (DLB) in China, a wavelet-based method was developed to investigate the wind characteristics of wind-rain-induced cable vibration. By using the wavelet analysis, the time-varying mean wind speed is extracted and a nonstationary wind speed model is proposed. The turbulence intensities and probability distributions of measured wind data are calculated using the proposed nonstationary model and compared with those based on empirical mode decomposition (EMD) and design values. The correlation between wind and wind-rain-induced acceleration response are discussed. At the same time, the relativity of acceleration responses of cable and the wind speed are discussed via calculating root mean square (RMS) averaging and acceleration response peak factors.

Tension Force and Structural Parameter Identification of Bridge Cables

Vibration measurement is one of the most widely used methods for tension evaluation and condition assessment of stay cables in cable-stayed bridges. In the existing practice, the tension force of a cable is identified from the measured modal frequencies with the use of the taut string theory or empirical formulae, by assuming pre-determined structural parameters (geometric and material parameters) and boundary conditions of the cable. As a result, an inaccurate estimation of the cable tension may be obtained when there is an error in the pre-determined structural parameters and boundary conditions. Moreover, the commonly used empirical formulae are not applicable in the case when the cable is intermediately attached with dampers. In the present study, a method enabling simultaneous identification of cable tension and other structural parameters from the measured modal frequencies is developed. A precise finite element model (FEM) accounting for cable flexural rigidity, sag-extensibility, spatial variability of dynamic tension, boundary conditions, lumped masses and intermediate supports and/or dampers is first formulated as the reference model in parameter identification so that the modeling error is minimized. Then the measured multiple modal frequencies are used together with the FEM to figure out a nonlinear least-square optimization scheme which helps eliminate measurement error and allows for simultaneous identification of the cable tension and other structural parameters. Application of the proposed method to the Dongting Lake Bridge cables from in-situ ambient vibration measurements illustrates high identification accuracy and fidelity of the proposed method.

Wavelet-Based Nonstationary Wind Speed Model in Dongting Lake Cable-Stayed Bridge

The wind-rain induced vibration phenomena in the Dongting Lake Bridge (DLB) can be observed every year, and the field measurements of wind speed data of the bridge are usually nonstationary. Nonstationary wind speed can be decomposed into a deterministic time-varying mean wind speed and a zero-mean stationary fluctuating wind speed component. By using wavelet transform (WT), the time-varying mean wind speed is extracted and a nonstationary wind speed model is proposed in this paper. The wind characteristics of turbulence intensity, integral scale and probability distribution of the bridge are calculated from the typical wind samples recorded by the two anemometers installed on the DLB using the proposed nonstationary wind speed model based on WT. The calculated results are compared with those calculated by the empirical mode decomposition (EMD) and traditional approaches. The compared results indicate that the wavelet-based nonstationary wind speed model is more reasonable and appropriate than the EMD-based nonstationary and traditional stationary models for characterizing wind speed in analysis of wind-rain-induced vibration of cables.

Wavelet-Based Nonstationary Wind Speed Model in Dongting Lake Cable-Stayed Bridge

The wind-rain induced vibration phenomena in the Dongting Lake Bridge (DLB) can be observed every year, and the field measurements of wind speed data of the bridge are usually nonstationary. Nonstationary wind speed can be decomposed into a deterministic time-varying mean wind speed and a zero-mean stationary fluctuating wind speed component. By using wavelet transform (WT), the time-varying mean wind speed is extracted and a nonstationary wind speed model is proposed in this paper. The wind characteristics of turbulence intensity, integral scale and probability distribution of the bridge are calculated from the typical wind samples recorded by the two anemometers installed on the DLB using the proposed nonstationary wind speed model based on WT. The calculated results are compared with those calculated by the empirical mode decomposition (EMD) and traditional approaches. The compared results indicate that the wavelet-based nonstationary wind speed model is more reasonable and appropriate than the EMD-based nonstationary and traditional stationary models for characterizing wind speed in analysis of wind-rain-induced vibration of cables.

Field observations of rain-wind-induced cable vibration in cable-stayed Dongting Lake Bridge

The cable-stayed Dongting Lake Bridge has been observed several times to exhibit large-amplitude cable oscillation under simultaneous action of rain and wind. To investigate excitation mechanism and response characteristic of the rain-wind-induced stay vibration, a series of field measurements lasting 45 days have been conducted on the Dongting Lake Bridge by deploying accelerometers, anemometers and rain gauge for continuous monitoring. This paper presents the measurement results of rain and wind excitations as well as dynamic response of a typical stay in three rain-wind excitation events. The measurement data show that under specific combination of rain and wind, the maximum acceleration response of the cable reaches 10 g and the maximum displacement response (peak-to-peak) is around 0.7 m. It is revealed that the large-amplitude rain-wind-induced stay oscillation occurs in the bridge when the mean wind velocity at deck level ranges from 6 to 14 m/s, the wind attack angle (relative yaw angle) ranges from 10° to 50°, and the rainfall is light to moderate (less than 8 mm/h). For the observed cable, the overall dominant mode of cable vibration during rain-wind excitations is the third mode. However, in the evolution process of this kind of vibration, the dominant mode may differ for different response segments.

Cable Vibration Control using Magnetorheological Dampers

As the world's first implementation of magnetorheological (MR) smart damping technique in bridge structures, a total of 312 semi-active MR dampers (RD-1005, Lord Corporation) have recently been installed for rain–wind-induced cable vibration control on the cable-stayed Dongting Lake Bridge, China. This project has undergone several stages of in situ experiments and tests: (i) modal tests of undamped cables, (ii) forced vibration tests of MR-damped trial cables, (iii) monitoring of MR-damped and undamped cable responses under rain–wind excitations, (iv) comparative tests using different damper setups, (v) full installation, and (vi) field measurements and real-time control tests after the installation. After outlining the above six stages of the whole project and addressing the experience and lessons learned from both open-loop control and closed-loop control practices, this study focuses on the design considerations of implementing MR dampers for cable vibration control, taking into account the effects of the damper stiffness, damper mass, stiffness of damper support, nonlinearity of the damper, and sag and inclination of the cable. The research efforts make it possible to develop elaborate MR dampers specific for application to bridge stay cables.

State-Derivative Feedback Control of Cable Vibration Using Semiactive Magnetorheological Dampers

Abstract: This article presents the theoretical and in situ experimental studies on state-derivative feedback control of bridge cable vibration using semiactive magnetorheological (MR) dampers. The semiactive feedback control is accomplished using only one MR damper and one accelerometer collocated near the lower end of the cable. Within the framework of reciprocal state space (RSS), the linear quadratic regulator (LQR) control technique is applied to formulate state-derivative feedback control law and derive the feedback and estimator gains for real-time control of cable vibration using MR dampers. The state-derivative feedback control strategy directly uses acceleration information for feedback and state estimation, which is usually the only measure available in practical cable vibration control implementation. More importantly, the control force commanded by the state-derivative feedback control strategy based on energy weighting is a dissipative force except for low velocity and small force, which is therefore implementable by the semiactive MR dampers without clipping. Numerical simulations of state-derivative feedback control for a stay cable in the cable-stayed Dongting Lake Bridge are conducted under sweeping sine excitation and sinusoidal step relaxation excitation, and then the experimental validation of the prototype cable is carried out in the bridge site with the help of the real-time control system dSPACE. Good agreement between the simulation and experimental results is observed.

MR damping system for mitigating wind-rain induced vibration on Dongting Lake Cable-Stayed Bridge

The Dongting Lake Bridge is a cable-stayed bridge crossing the Dongting Lake where it meets the Yangtze River in southern central China. Several intensive wind-rain induced vibrations had been observed since its open to traffic in 1999. To investigate the possibility of using MR damping systems to reduce cable vibration, a series of field tests were conducted. Based on the promising research results, MR damping system was installed on the longest 156 stay cables of Dongting Lake Bridge in June 2002, making it the worlds first application of MR dampers on cable-stayed bridge to suppress the wind-rain induced cable vibration. As a visible and permanent aspect of the bridge, the MR damping system must be aesthetically pleasing, reliable, durable, easy to maintain, as well as effective in vibration mitigation. Substantial work was done to meet these requirements. This paper describes field tests and the implementation of MR damping systems for cable vibration reduction. Three-years reliable service of this system proves its durability.

Structural health monitoring and intelligent vibration control of cable-supported bridges: Research and application

Advances in structural health monitoring and intelligent vibration control technologies can have a great impact on the performance enhancement of civil engineering structures. In Hong Kong, a sophisticated long-term monitoring system has been devised by the HKSAR Highways Department to monitor structural performance and health conditions of three cable-supported bridges and monitoring systems for two new long-span bridges are also being developed. Implementation of these on-structure monitoring systems motivates associated technological and methodological investigations which are outlined in this paper. Newly emerging auto-adaptive and intelligent materials offer enormous potential for developing smart damping devices for vibration control of civil structures. Successful application of smart magneto-rheological (MR) dampers has recently been realized in the cable-stayed Dongting Lake Bridge for mitigating rain-wind-induced cable vibration. Experience and lessons learned from this engineering practice are summarized in this paper.