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• An efficient approach is explored to evaluate the extreme response and reliability of train-bridge interaction system. • The extreme response of an innovative railway integral bridge considering various stochastic excitations is studied. • The failure probability of high-speed train running safety conditional on wind speed and running speed is assessed. • The in-site long-term wind field measured data are applied to improve the assessment accuracy. The randomness of responses in a train-bridge interaction (TBI) system induced by stochastic track irregularity and crosswind has been addressed. However, the extreme value distribution (EVD) and reliability prediction of TBI system are little known. Due to the complexity of TBI system, the prediction approach is critical to the issues of extreme value and reliability evaluation, involving the computational accuracy and efficiency. Thus, the Monto Carlo-based global maximum method, probability density evolution-based virtual time process method (VPM), and average conditional exceeding rate method (ACERM) are considered in this study. The optimal approach for the EVD prediction of bridge buffeting responses and the TBI system with or without the consideration of crosswinds is identified. An innovative 3 × 70 m integral bridge is chosen as the study case, which is an emerging type of bridge structures used in the Chinese high-speed railway lines. Its extreme responses under the single and dual stochastic excitations of track irregularity and wind turbulence are fully investigated in this study. The study results show that the VPM and ACERM are efficient and accurate to evaluate the extreme responses of a TBI system. The ACERM is recommended in assessing the train running safety due to its high computational efficiency and reasonable accuracy. When the crosswind is not a consideration, the high-speed train running safety can be ensured with high probability if the train travels on the integral bridge below the design speed of 350 km/h. However, the failure probability of wheel-rail lateral contact forces reaches 51% if predicted under the mean wind speed of 30 m/s and train speed of 120 km/h. Finally, the advantages of the integral bridge over conventional bridges (e.g., continuous girder bridge) are discussed. [ABSTRACT FROM AUTHOR]

Cable-stayed bridges have been commonly used on high-speed railways. The design, construction, and maintenance of cable-stayed bridges necessitate an accurate assessment of the cable temperature field. However, the temperature fields of cables have not been well established. Therefore, this research aims to investigate the distribution of the temperature field, the time variability of temperatures, and the representative value of temperature actions in stayed cables. A cable segment experiment, spanning over one year, is conducted near the bridge site. Based on the monitoring temperatures and meteorological data, the distribution of the temperature field is studied, and the time variability of cable temperatures is investigated. The findings show that the temperature distribution is generally uniform along the cross-section without a significant temperature gradient, while the amplitudes of the annual cycle variation and daily cycle variation in temperatures are significant. To accurately determine the temperature deformation of a cable, it is necessary to consider both the daily temperature fluctuations and the annual cycle of uniform temperatures. Then, using the gradient boosted regression trees method, the relationship between the cable temperature and multiple environmental variables is explored, and representative cable uniform temperatures for design are obtained by the extreme value analysis. The presented data and results provide a good basis for the operation and maintenance of in-service long-span cable-stayed bridges. [ABSTRACT FROM AUTHOR]

Due to the atmospheric temperature and solar radiation, the effects of temperature variation in bridge structures should be considered. Such variation induces notable deformations and movements, jeopardizing the safety of bridges and high-speed trains operations. However, the temperature action is a random process and its distribution is difficult to determine. The existing methods for analyzing structural temperatures are insufficient to meet the precision requirement. Therefore, the accurate prediction of extreme structural temperatures relates to the accurate evaluation on the bridge safety. This paper proposes a robust and accurate model for predicting the extreme structural temperature of a bridge. A field experiment, spanning over 2 years, was carried out on a high-speed railway bridge; and the long-term (56-years) atmospheric temperature data was adopted. Probabilistic models for the structural temperature were established using the Maximum Entropy (MaxEnt) model and the Generalized Pareto distribution (GPD) model; and the predictions on the uniform structural temperature (T u ) with 50 and 100 years return periods are presented. Additionally, the performance between the MaxEnt model and the GPD model is compared, based on the estimates with different return levels. The results show that the MaxEnt model is more stable and is significantly robust to the variation of sample sizes; and indicates that the MaxEnt model reduces the uncertainty of outcomes and avoids the high risk of bias. The MaxEnt model has a great potential to the applications of the extreme value analysis with small sample size. It offers a wider applicability and helps solve practical problems. [ABSTRACT FROM AUTHOR]

The structural temperature distribution, especially temperature difference caused by solar radiation, has a great impact on the deformation and curvature of the concrete slab tracks of high-speed railways. Previous studies mainly focused on the temperature prediction of slab tracks, while how the temperature distribution is affected by environmental conditions has been rarely investigated. Based on the integral transformation method, this work presents an analytical method to determine and decompose the temperature distribution of the concrete slab track. A field temperature test of a half-scaled specimen of concrete slab track was conducted to validate the developed methodology. In the proposed method, we decompose the temperature distribution of the slab track into an initial temperature component and a boundary temperature component. Then, the boundary temperature components caused by solar radiation and atmospheric temperature are investigated, respectively. The results show that the solar radiation plays a significant role in the nonlinear temperature distribution, while the atmospheric temperature has little effect. By contrast, the temperature change in the slab surface resulting from the atmospheric temperature accounts on average for only 5% in the hot weather condition. The proposed method establishes a relation between the structural temperature and meteorological parameters (i.e., the solar radiation and atmospheric temperature). Consequently, the temperature distribution of the concrete slab track is predicted via the meteorological parameters. [ABSTRACT FROM AUTHOR]

This paper presents a theoretical solution for bond-slip behavior of SRC interface based on experiment, numerical simulation, and theoretical derivation. Push-out tests of five specimens were firstly carried out, based on which, the simplified bond-slip model was proposed. The specimen was fabricated using the Q345H-shape steel (400 mm × 200 mm×13 mm × 8 mm) and C50 concrete (350 mm × 600 mm) with a bonding length of 500 mm. A FE model was established based on the bond-slip model to analyze the nonlinear bonding stress that are difficult to obtain from the experiment. The research shows that although the bonding stress in the elastic stage is not uniformly distributed, it is basically uniformly distributed when the ultimate bearing capacity is reached. It proves that assuming the average interfacial bonding stress under ultimate load to replace the maximum bonding stress is reasonable, which is crucial for designer to estimate interface bearing capacity and maximum bonding stress. Moreover, five different stages were obtained by the FE model analysis and the theoretical equations of bonding stress nonlinear distribution were obtained based on the boundary condition of each stage. The theoretical solution clearly showed the relationship between interface nonlinear stress distribution and influencing parameters including the bond area, elasticity modulus of material, section area of specimen, bond-slip constitutive model, and the external load. Based on the theoretical model, the influences of different parameters can be directly obtained without conducting further experiments and establishing different FE models. • The simplified bond-slip model was proposed and nonlinear distributiion of interfacial bonding stress was analyzed. • Assuming the average interfacial bonding stress under ultimate load to replace the maximum bonding stress is reasonable. • Corresponding analytical formulas for the interfacial stress in five different stages were established, respectively. • The theoretical solution showed the quantitative relationship between interface nonlinear stress and influencing parameters. [ABSTRACT FROM AUTHOR]

Track-bridge interaction under the seismic excitation is a dominant factor to the design and operation of railway bridges. A spatial model integrating rails, deck system, stringers, cross beams, suspenders, main trusses, piers and foundations was established in this paper, adopting non-linear springs to simulate the longitudinal resistance between the track and the bridge. The improved Penzien model was utilised to simulate the soil-pile interaction effect and a computer program was developed to generate artificial seismic waves. Comparison of natural vibration characteristics for the track-bridge system with and without considering the track constraint was made. Furthermore, the effects of sensitive parameters were investigated, including the ballast resistance, friction of movable bearings, location of rail expansion joint (REJ), etc. Present study results indicate that the track-bridge interaction enhances the structural integrity and induces relatively higher natural frequencies of the bridge. In general, the response obtained by the ballast resistance specified in the Chinese code is smaller than that by UIC code. Neglecting the friction of movable bearing will lead to over-estimated rail stresses and under-estimated internal forces of some piers in the system. Setting REJ at both beam ends is more efficient to release the seismic stress of the rail on the bridge. [ABSTRACT FROM AUTHOR]

• The randomness of track irregularity and wind turbulence is considered to evaluate the extreme value distributions of high-speed train-bridge interaction system under crosswinds. • To obtain the accurate wind parameters used in the extreme analysis, the turbulence characteristic is analyzed based on the long-term wind field measurement near the bridge site. • The applicability of PDEM based virtual time process method to the extreme responses evaluation of train-bridge interaction (TBI) system is validated by comparing with Monto Carlo Method. • The Weibull distribution model (Type 3 of the generalized extreme value distribution) can be used for the extreme value evaluation of TBI system. This conclusion may be useful to the other similar analysis about extreme responses of TBI system. Deterministic safety curves of safe train running speeds versus mean wind speeds (MWSs) have been studied in the time domain, considering the train-bridge interaction (TBI) dynamics. However, the randomness of track irregularity and wind turbulence makes the extreme response of the TBI system indeterministic; and so does the safety curve. Therefore, an extreme evaluation theory based on the probability density evolution method (PDEM) is adopted in this study to investigate the extreme response distributions of TBI system under crosswinds with the consideration of the field measured turbulence characteristics. The applicability of the theory on train-bridge wind interaction system is verified first, followed by the discussion on the variations of extreme responses of train and bridge versus MWSs and running speeds of trains running on a high-speed railway cable-stayed bridge. A probabilistic safety curve is finally determined based on 40 cases with the wind speeds ranging from 10 m/s to 45 m/s and the train speeds ranging from 200 km/h to 400 km/h. The study analyses demonstrate the computational accuracy and efficiency of the PDEM-based extreme theory applied to the TBI system; and indicate that the extreme responses of high-speed trains and Quanzhou Bay Bridge increase with increasing MWSs and train speeds. In addition, most of performance indicators do not exceed the code-stipulated failure criteria except the train unloading factor and the lateral displacement at the mid-main span. The probabilistic safety curve for the studied bridge is thus deduced according to these two controlling indexes. [ABSTRACT FROM AUTHOR]

The effect of non-Gaussian inflows on structural long-term extreme buffeting responses has been little investigated. In this study, the sensitivity of long-term extreme value distribution (EVD) of a high-speed railway cable-stayed bridge to the non-Gaussian intensity is studied first. The turbulence skewness and kurtosis are then taken as the environmental variables to investigate their single and combined effects on bridge's long-term EVDs based on a proposed hybrid approach that combines the machine learning algorithm and virtual process method. The 2.5-year measured turbulence wind and 40-year annual extreme wind speed recorded near the bridge site are utilized to describe the probability distributions of the skewness and kurtosis of turbulence wind and 10-min mean wind speed. The research results reveal that: (1) the long-term EVD of torsional angle is more sensitive to non-Gaussian turbulence wind than vertical and lateral extreme responses; (2) the single effect of turbulence skewness is detrimental but limited, and the combined effect of skewness and kurtosis of turbulence u (w) is also weak within the considered MRIs (1–100 years). Lastly, the virtual process method is shown to be applicable to predict structural long-term EVDs; and it is efficient without losing significant prediction accuracy. • A hybrid approach is proposed to improve the analysis efficiency of structure long-term extreme response. • The long-term extreme response of a cable-stayed bridge under non-Gaussian inflow is investigated comprehensively. • The applicability and efficiency of virtual process method in evaluating structural long-term EVD are validated. • The probability models of turbulence high-order statics are constructed based on long-term monitoring wind data. [ABSTRACT FROM AUTHOR]

This paper presents the experimental observations and results of six full-scale field ballastless track structure specimens, and tested under longitudinal and transverse shear load. The tests aimed to examine the interfacial shear capacity of the continuous slab track structure and investigate the interfacial bond–slip behaviour. The results show that bond strength of the two interfaces which were on the top and bottom of mortar layer, respectively, have a large difference. Until the top interface of the mortar layer fractured, no slip displacement was observed in the bottom interface. In addition to the experimental study, a finite element model using nonlinear interface elements was employed to simulate the tests. The numerical calculated capacity agreed well with the experimental results, showing that the proposed bond–slip law is reliable. Finally, the track slab's evenness with the bond–slip effect under the dynamic load was studied. [ABSTRACT FROM AUTHOR]

The non-Gaussian property of turbulence has been emphasized in some measured wind data. However, the classic Scanlan buffeting theory with the Gaussian distribution assumption of turbulence may cause errors in predicting the structural extreme response. In this study, a hybrid approach for predicting bridge's extreme buffeting response is proposed and validated, which considers multi-dimensional non-Gaussian random variables. Then the extreme buffeting response of a cable-stayed bridge under the attack of non-Gaussian wind is investigated, where the in-situ measured wind data of Typhoon ' Bailu ' is adopted. The sensitivity of extreme buffeting response to turbulence skewness and kurtosis is also analyzed. The study results show that the lateral and vertical buffeting displacements are in skewed distributions under the attack of Typhoon ' Bailu '. Compared to the Gaussian wind assumption, the non-Gaussian typhoon decreases the lateral extreme response, while increases the vertical extreme response. The results from the sensitivity analysis reveal a strong correlation between the non-Gaussian intensity of component u and that of the lateral buffeting response. In addition, the lateral extreme buffeting response increases significantly with the skewness and kurtosis of component u at a high probability level. • The non-Gaussian property of Typhoon ' Bailu ' is fully investigated from the perspective of probabilistic statistics. • A hybrid approach for predicting bridge's extreme buffeting response is proposed and validated • The effect of the non-Gaussian typhoon on the extreme buffeting response of a cable-stayed bridge is addressed. • The sensitivity of the extreme buffeting responses to the non-Gaussian intensity is comprehensively investigated. [ABSTRACT FROM AUTHOR]

There are a number of long-span bridges located in the southeast coastal bay of China which is prone to typhoons. Very limited studies have been made of the wind field characteristics in this bay which is special as it has various changes in fetch from sea to land and vice versa, depending on the wind direction. Thus, a detailed analysis of the wind properties of the 2019 Typhoon Bailu has been carried out and the findings are presented in this paper. The measurements were made from sensors on a 40 ​m-high meteorological mast in the vicinity of Quanzhou Bay Sea-Crossing High-Speed Railway Bridge. First, the characteristics of mean wind and turbulence are analyzed. The study results show that: the amplitude of the typhoon spectra after the second landfall is smaller than that before the landfall almost in one order of magnitude. The wind profile and turbulence coherence are also a focus of this study. It is revealed that a logarithmic model is more consistent with the measured wind speed profile compared with other commonly specified profiles. Strong coherence of u and w components at low frequencies is demonstrated in this study. • A comprehensive study on the wind characteristics of the typhoon near a HSR sea-crossing bridge site is presented. • Typhoon data are completely recorded, and the profiles of mean wind and turbulence characteristics are fully analyzed. • Some important wind property indicators stipulated in some codes, such as TI, ILS etc., are compared with measured values. [ABSTRACT FROM AUTHOR]

Atmospheric temperature and directed solar radiation have a significant effect on the temperature field of high-speed railway (HSR) concrete bridge and ballastless track structure. However, temperature actions are random process of which distribution laws are difficult to explore, and existing statistical methods for structure temperature analysis are still not precise. So far, there are few researches for annual temperature spectra and design codes for bridge–track system. Based on the one-year observation data, this paper investigated the temperature actions for Chinese HSR bridge–track structure. By utilizing reliability high moment theory, a statistical method which could built virtual distribution was put forward. Based on the renewed study, the effects of waterproof for deck were taken into consideration, a temperature action model was proposed which is suitable for both bridge and track structure. In addition, for track structure, the previous temperature load models were modified. Apart from that, by proposing the concepts of temperature uniform and fluctuant spectra, the research evaluated service performance of structure. Finally, the distribution regularities of uniform temperature spectra were fitted by Fourier series, and the relationship between structural and atmospheric uniform temperature was established (formula (25) ). As a result, according to 50 years recorded atmospheric temperature data, the prediction model of the structure extreme temperature was suggested, and by taking the recurrence interval of 100, 150 and 300 years, the extreme temperatures of the system are 52.23, 54.34 and 57.77 °C. [ABSTRACT FROM AUTHOR]