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The Dongbao River Xin’an Bridge is the first hybrid continuous girder bridge with corrugated steel webs in China. To assess its service conditions and guarantee its safe operation, a continuous structural health monitoring (SHM) system is designed in this paper. The SHM system consists of a sensor system, a data acquisition and transmission system, and a data processing and control system. The measurement parameters, including vehicle loads, temperature, deformation, strain, and acceleration, are determined, and a detailed sensor layout is given based on the mechanical characteristics of the bridge. The SHM system adopts a bus gateway and an IP modem to collect and transmit sensor data. Monitoring data from October 9, 2022, to March 16, 2023, were analyzed. The probability distributions of the daily maximum temperature differences and vehicle loads are reconstructed. The correlation of girder deflection and strain with ambient temperature has been demonstrated. The identification and tracking of modal parameters are implemented. The results show that the maximum deflection is within the threshold range and that the modal parameters are basically stable. All the results demonstrate the healthy structural condition of the bridge and the excellent working performance of the SHM system. The collected data provide scientific guidance for the performance evaluation of the Dongbao River Xin’an Bridge and the optimized design of similar bridges.

Real-time representation of the current performance of structures is an important task for perceiving potential danger in in-service bridges. Methods driven by the multisource sensing data of structural health monitoring systems are an effective way to achieve this goal. Due to the explicit zero-point of signals, the live load-induced response has an inherent advantage for quantitatively representing the performance of bridges. Taking a long-span cable-stayed railway–highway combined bridge as the case study, this paper presents a representation method of in-service performance. First, the non-stationary sections of train-induced response are automatically extracted by wavelet transform and window with threshold. Then, the data of the feature parameter of each non-stationary section are automatically divided into four cases of train load according to the calculational theory of bridge vibration under train effect and clustering analysis. Finally, the performance indexes for structural deformation and dynamics are determined separately, based on hierarchical clustering and statistical modeling. Fusing the real variability of massive data from monitoring and the knowledge of mechanics of theoretical calculations, accurate and robust indexes of bridge deflection distribution and forced vibration frequency are obtained in real time. The whole process verifies the feasibility of the representation of bridge in-service performance from massive multisource sensing data. The presented method, framework, and analysis results can be used as a reference for the design, operation, and maintenance works of long-span railway bridges.

Using theoretical modeling combined with monitoring data, the typical dynamic and static behaviors of a continuous steel truss arch railway bridge are evaluated. The dynamic behavior involves an impact factor induced by the action of running trains, and the static behavior refers to axial bending performance and the stress distribution among different planes of the truss. The transverse position, length, and speed of running trains are introduced to conduct an analysis of their influences on the dynamic and static behaviors of the bridge superstructure. A structural safety evaluation is also conducted by comparison with the provisions recommended by design codes and by analysis of absolute stress. It is concluded that three types of members present different dynamic behaviors and that the value of the impact factor for chords B exceeds the provision recommended by the design codes. Chords C present the greatest ratio of bending stress versus axial stress. An imbalance of stress distribution exists among the three planes of the truss, and the difference is the smallest when trains run along the middle railways. Because the train-induced stress is considerably lower, the dynamic and static performances of the bridge are within the scope of safety.

This paper presents an investigation of the wind-induced buffeting responses of the Jiashao Bridge, the longest multispan cable-stayed bridge in the world. A three-dimensional finite element model for the Jiashao Bridge is established using the commercial software package ANSYS and a 3D fluctuating wind field is simulated for both bridge deck and towers. A time-domain procedure for analyzing buffeting responses of the bridge is implemented in ANSYS with the aeroelastic effect included. The characteristics of buffeting responses of the six-tower cable-stayed bridge are studied in some detail, focusing on the effects including the difference in the longitudinal stiffness between the side towers and central towers, partially longitudinal constraints between the bridge deck and part of bridge towers, self-excited aerodynamic forces, and the rigid hinge installed in the middle of the bridge deck. The analytical results can provide valuable references for wind-resistant design of multispan cable-stayed bridges in the future.

Nanjing Dashengguan Bridge, which serves as the shared corridor crossing Yangtze River for both Beijing-Shanghai high-speed railway and Shanghai-Wuhan-Chengdu railway, is the first 6-track high-speed railway bridge with the longest span throughout the world. In order to ensure safety and detect the performance deterioration during the long-time service of the bridge, a Structural Health Monitoring (SHM) system has been implemented on this bridge by the application of modern techniques in sensing, testing, computing, and network communication. The SHM system includes various sensors as well as corresponding data acquisition and transmission equipment for automatic data collection. Furthermore, an evaluation system of structural safety has been developed for the real-time condition assessment of this bridge. The mathematical correlation models describing the overall structural behavior of the bridge can be obtained with the support of the health monitoring system, which includes cross-correlation models for accelerations, correlation models between temperature and static strains of steel truss arch, and correlation models between temperature and longitudinal displacements of piers. Some evaluation results using the mean value control chart based on mathematical correlation models are presented in this paper to show the effectiveness of this SHM system in detecting the bridge’s abnormal behaviors under the varying environmental conditions such as high-speed trains and environmental temperature.

Making use of long-term transverse vibration monitoring data of DaShengGuan Bridge, the early-warning method of train running safety of the high-speed railway bridge is established by adopting principal component analysis (PCA) method. Firstly, the root mean square (RMS) of the transverse acceleration of the main girder is used as the monitoring parameter for the train running safety. The correlation model between the RMS values measured from different positions is further adopted as the evaluating model for the train running safety. Finally, the effects of the environmental changes on the evaluating model are eliminated using the PCA method and the warning index for the train running safety is further constructed. The analysis results show that the correlation between the RMS values of the accelerations from different measuring positions on the main girder can be analyzed by a quadratic polynomial fitting model. The PCA method can effectively remove the environmental effects on the quadratic polynomial fitting model. The proposed warning method provides a good capability for detecting the abnormal changes of the measured transverse accelerations and hence it is suitable for early-warning of the train running safety.

To accurately evaluate the influence of the actual tension and compression state and stress ratio at the deck-to-rib welding seam position on the fatigue life of a bridge deck, this paper establishes a coupled stress analysis model that considers the welding residual stress and vehicle stress. Taking the Jiangyin Bridge as an example, a qualitative analysis of the fatigue life under the vehicle load and residual stress field is carried out using the proposed method. A case analysis showed that when the residual tensile stress in the welding seam position is superimposed on the mainly tensile cyclic vehicle load stress, the longitudinal stress relaxation exceeds the peak vehicle load stress; significant longitudinal stress relaxation occurred, while the transverse stress relaxation is not significant. However, when the residual tensile stress is superimposed on the mainly compressive cyclic vehicle load stress, the relaxations of both the longitudinal and transverse stresses are not obvious. Compared with the stress state of the welding point under the action of only the vehicle stress, when the coupling effect of the residual stress and vehicle stress is considered, i.e., the loading condition, the fatigue stress state of the weld point has undergone an essential change under cyclic compressive stress, that is, the compressive stress state that does not require a fatigue check is changed to the tensile stress state. Although the fatigue state of the tensile stress cycle condition has not changed, the fatigue life is reduced by varying degrees under either the compressive or tensile condition. [ABSTRACT FROM AUTHOR]

The dynamic strain response due to the passing trains is one of the most important indexes in the design and maintenance of long-span steel-truss arch railway bridges. The strain influence line (IL) and dynamic load factor (DLF) are used to characterize the vehicle-induced strain response of bridge members. Temperature effects on ILs and DLFs of strain response due to high-speed trains in various bridge structural members are investigated. An adaptive finite impulse response (FIR) filter is implemented to obtain the strain IL and DLF for the response of various structural members of the Dashengguan Yangtze River Bridge using data from strain sensors that are part of the bridge structural health monitoring (SHM) system. Relationships between the strain ILs and DLFs and temperature are obtained for various members. The analysis reveals that (1) the DLFs for the short hangers require further study; (2) the effect of temperature on the ILs of each member in the subject bridge can be described by polynomials; and (3) the DLFs of the majority of the structural members are not related to temperature. Recommendations to improve the design, maintenance, and long-term monitoring of steel-truss arch bridges are provided. [ABSTRACT FROM AUTHOR]

Fatigue cracking is crucial issue for welded steel bridges that endure repeated vehicle loads. With typical fatigue-life evaluation methods, it is difficult to consider the influence of low stress amplitude. Based on existing full-range S-N curves and their formulas for base metal, a unified fatigue-life evaluation method is recommended for welded joints. The basis for construction of full-range S-N curves is to obtain the welding residual stress and stress concentration factor. In this paper, rib-to-deck welded joints are introduced as examples to demonstrate the detailed steps of a fatigue-life evaluation procedure. From the analysis of welding residual stress, it can be concluded that residual stress is influenced by the geometric dimensions of the composite members.With an increase in the geometric dimensions, the level of residual stress is increased. In addition, static-load experiments were conducted to obtain the stress concentration factor. A hot-spot full-range S-N curve was then obtained for rib-to-deck welded joints by calibrating the formula fromsmall quantities of fatigue experiments. An actual bridge installed with a structural health monitoring system (SHMS) was used as a case study to compare the recommended model with typical fatigue codes. The comparison results indicate that the recommended model is more conservative than typical fatigue codes. [ABSTRACT FROM AUTHOR]

The driving security of trains at high speeds is among the pivotal issues significantly affected by the smoothness of rail lines. For high-speed railway steel bridges, the fatigue cracking of typical positions under the rail lines will reduce the stiffness of the deck plate, inducing the smoothing of the rail lines. In this paper, a new theoretical approach is proposed that integrates the fatigue assessment of a typical welded joint for high-speed railway steel bridges in service. Based on the strain history data recorded by a structural health monitoring system, the theoretical approach includes various factors, including stress concentration, environmental corrosion, and train flow. Upon application in an actual high-speed railway bridge with an orthotropic steel deck, the approach was used to conduct determinative and reliable fatigue-life evaluation of the bridge. A static-load experiment was conducted to obtain the stress distribution around the weld and the difference in stress between the positions of the weld and strain gauge. The effect of environmental corrosion integrated two aspects: increased stress and reduced fatigue resistance. Without consideration of train-weight growth, in conclusion, the fatigue life of a typical welded joint will be infinite even if the train flow grows constantly. In addition, the fatigue life of typical welded joints, determinative or reliable, may be less than the designed service period when the growth rate of the train weight reaches 5%. [ABSTRACT FROM AUTHOR]

Temperature field data from the steel truss arch girder and longitudinal displacement data from six groups of rubber bearings were collected by the structural health monitoring system for the Dashengguan Yangtze Bridge. By using long-term monitoring data, two correlations are investigated: the linear correlation between the longitudinal displacement and the temperature field (including uniform temperature and temperature gradient); and the linear correlation of the longitudinal displacements in different locations. A multivariate linear regression equation is used to model the first correlation, and a Lagrange polynomial interpolation is used to model the second correlation. The final mathematical models, representing the healthy state of the bearings, can be applied to simulate the longitudinal displacements of the main girder. Furthermore, the change regularity of longitudinal displacements for the degraded rubber bearings is revealed taking advantage of a hysteretic model and presumed envelope curves of frictions caused by bearing degradation. A method of detection and location for the degraded bearings is proposed in four detailed steps, and the numerical results demonstrate that this method is effective. [ABSTRACT FROM AUTHOR]

Based on the health monitoring system installed on the main span of Sutong Cable-Stayed Bridge, GPS displacement and wind field are real-time monitored and analyzed. According to analytical results, apparent nonlinear correlation with certain discreteness exists between lateral static girder displacement and lateral static wind velocity; thus time series of lateral static girder displacement are decomposed into nonlinear correlation term and discreteness term, nonlinear correlation term of which is mathematically modeled by third-order Fourier series with intervention of lateral static wind velocity and discreteness term of which is mathematically modeled by the combined models of ARMA(7, 4) and EGARCH(2, 1).Additionally, stable power spectrum density exists in time series of lateral dynamic girder displacement, which can be well described by the fourth-order Gaussian series; thus time series of lateral dynamic girder displacement are mathematically modeled by harmonic superposition function. By comparison and verification between simulative and monitoring lateral girder displacements from September 1 to September 3, the presented mathematical models are effective to simulate time series of lateral girder displacement from main girder of Sutong Cable-Stayed Bridge. [ABSTRACT FROM AUTHOR]

Vibration tests on an AMECO (Aircraft Maintenance Engineering Company) maintenance hangar were performed as multi-support excitations in order to verify the effectiveness of the multi-support time history method. The excitation sources represented the three cases of aeroplane taking-off, aeroplane landing and the running in the hangar of the aeroplane engine. Acceleration sensors were installed on the column bases of the hangar structure in order to collect the ground motion records for various excitation cases. The structural dynamic responses were obtained when subjected to the collected ground motions via the multi-support time history method. The calculation results were generally in agreement with those of the test in both the time domain (acceleration peaks) and the frequency domain, which verify the effectiveness of the multi-support time history method. The vibration test can also provide valuable reference data for long-span space structures under multi-support excitations. [ABSTRACT FROM AUTHOR]

This paper describes the development of a multi-stage scheme for structural damage warning of the Runyang Cable-stayed Bridge using the measured dynamic responses from an on-line instrumentation system. In the first stage, the wavelet packet energy spectrum (WPES) is extracted using wavelet packet analysis from the measured dynamic responses caused by ambient excitations, thus providing parameters warning of occurrence of structural damage. The second stage is to formulate correlation models describing the seasonal relationship between WPES and temperature and the third stage is to classify the measured changes of WPES, whether due to environmental temperature or to structural damage, using a novelty detection technique based on statistical process control. The usefulness of the approach is examined on the Runyang Cable-stayed Bridge using 236 days of health monitoring data. The results reveal that the seasonal change of environmental temperature accounts for variation in the measured WPES, which averaged a 200% variance, and that the approach is able to eliminate the temperature effects and provides a good capability for detecting the damage-induced 10% variance. [ABSTRACT FROM AUTHOR]