Complicated temperature fields and crossing high-speed trains offer new challenges for monitoring girder deflections in operating railway bridges. Behavior analyses and early warning of girder deflections are necessary for the diurnal operation of bridge structures. Regarding the Nanjing Dashengguan Yangtze River Bridge, the present paper identifies the temperature-induced/train-induced deflections of the bridge girder from deflection data obtained from the wavelet transform. The principal components of the bridge temperature field are obtained to verify the temperature sensitivity of the girder deflection. The effect of the temperature-induced girder deformation on train-induced girder deflections is analyzed using the train-bridge dynamic model. The statistical laws of the downward and upward of train-induced girder deflections are described using the t location-scale distribution. Based on the mutual updating of monitoring data and numerical model, the behaviors of the temperature-induced/train-induced deflections of the bridge girder can be captured accurately, and the warning threshold of girder deflections under the coupling effects of temperature and trains is determined rapidly. The results demonstrated that the influence of the temperature-induced girder deformation on the train-induced girder deflection is relatively small when compared with the train-induced girder deflection itself, with the increasing amplitude being no more than 3%. A real-time early warning of girder deflections for the long-span railway bridge can be conducted to indicate the abnormal changes in girder deflection less than 10 s, which is likely due to the deterioration of track irregularity on the bridge or damaged bridge components.

Bridge performance undergoes time-varying changes when exposed to aggressive environments. While much work has been done on bridge reliability under corrosion, little is known about the effects of creep and shrinkage on the reliability of concrete bridges. In this paper, the CEB-FIP model for creep and shrinkage is applied by using finite-element (FE) analysis in conjunction with probabilistic considerations. Verification is made by comparing the analytical findings with existing test data. More specifically, a time-dependent reliability assessment is made for a composite prestressed concrete (PSC) box-girder bridge exposed to a chloride environment. This realized via an advanced probabilistic FE method. The postcracking behavior of the thin-walled box girder is described using composite degenerated shell elements, and importance sampling is used to improve the efficiency of the reliability analyses. It is shown that concrete creep and shrinkage dominate during the early stages of bridge structure deterio...

Both conservation and intervention methods must be compatible with each other and appropriate for the original building materials. Therefore, the characterization of historic building materials is indispensable for investigating chemical composition, micro-structure and morphological features to study the current condition, environmental influence and change mechanism due to natural aging or man-made decay processes. Given the great variety of chemicals which can be analyzed, complex problems related to architectural heritage materials are investigated via optimized methodologies. Among the existing techniques, optical microscopy (OM) is an inexpensive and dominating tool to obtain preliminary information on complex samples. Atomic force microscopy (AFM) can provide real three-dimensional topographies showing sample surface properties. Electron microscopes combined with energy dispersion X-ray analysis (EM-EDX) are the instruments specifically developed to acquire images of target materials at high magnification. Infrared and Raman spectroscopies are frequently used to characterize inorganic and organic compounds. Thermal analysis can rapidly and accurately measure changes in crystalline structure, dehydration and decomposition. X-ray based technologies have a wide range of applications as follows. X-ray fluorescence (XRF) is one of the most frequently used techniques for elemental analysis. X-ray diffraction (XRD) is a fast and inexpensive technique for the characterization of man-made and natural materials. X-ray photoelectron spectroscopy (XPS) is applied to quantify the valence and electronic levels of specific elements. X-ray absorption spectroscopy (XAS) is a powerful technique for detecting the electronic structure of matter. UV–visible (UV–vis) spectroscopy is also of great importance in architectural heritage, which can reveal different physicochemical mechanisms causing color. Laser-induced breakdown spectroscopy (LIBS) can effectively eliminate the pollution on the surface and detect the internal elements of the target material. Ion beam analysis can quantify trace elements with high sensitivity. Mass-based techniques are mainly applied to identify unknown organic substances at the molecular level. This review describes some classical applications of individual techniques and provides scientific support for scientists and engineers to make decisions in the context of architectural heritage.

This study proposes a novel curved steel plate damper to improve the seismic performance of structures. The theoretical analysis of the curved plate damper was carried out deriving formulas of key parameters of the curved plate damper including elastic lateral stiffness, yield strength, and yield displacement. Moreover, a cyclic loading test of four sets of specimens was conducted, and the hysteretic performance, ductility, energy dissipation performance, and strain of the specimens were studied. The results showed that the initial stiffness of the damper was large, no obvious damage was observed, and the hysteresis loop was full. The tested dampers had good deformation and energy dissipation performance. The stress variable rule of the damper was obtained by stress analysis, where the plastic deformation at the end of the semi-circular arc was large. The formula for various parameters of the damper was compared with experimental and numerical results; thus, the value of the adjustment coefficient was determined reasonable. Meanwhile, the rationality of the finite element model was also verified.

In this paper, the Ogden model is employed to characterize the hyperelastic properties of rubber, and on the basis of a pattern search algorithm and the Levenberg-Marquardt algorithm, a professional method that can realize the comprehensive fitting of the uniaxial tension, biaxial tension, planar tension, and simple shear experimental data of hyperelastic materials was developed. The experiment data from Treloar (1944) was fitted very well, and the determined parameters by using this method were proven correct and practical in the numerical verification in ANSYS. Then, the constitutive model of the hyper-viscoelastic materials combining the Ogden model with the generalized Maxwell model was explained in detail, and the parameter identification method was also proposed by using the pattern search method. Then, three groups of relaxation tests of uniaxial tension and four groups of simple shear tests with different loading velocities were conducted to obtain the corresponding virtual experiment data. After discussing the constraints and initial setting values for the undetermined parameters, these virtual data of different loading histories were respectively employed to identify the parameters in the hyper-elastic model, and the accuracy and the reliability of the estimated parameters were also verified in ANSYS.

Dynamic parameterization of the statistical characteristics of structural systems’ measured input and output data is an important task for the digital twin modeling and intelligent risk assessment of transportation infrastructures. Characteristics of mixed skewness probability are common in structural systems, and its extreme value represents the risk state closest to the critical limit. The generalized extreme value mixture model (GEVMM) can consider multiple factors that interfere with each other, based on which the generalized maximum likelihood estimation (GMLE) of full Bayesian is introduced. The proposed GMLE-GEVMM can conduct the modeling of mixed skewness probability (mainly including strong uni-factor and multi-factor statistical characteristics) by fusing the prior physical information for each parameter. A reliable paradigm for predicting the dynamic extreme value of practical engineering is presented. The proposed methods can overcome the probabilistic modeling problem for complex mixed skewness characteristics, and significantly improve the prediction accuracy of the extreme value of probability. The continuous monitoring data from a real bridge is used for validation. The modeling and predicting results verified the proposed methods’ strong applicability and high accuracy for complex probabilistic system input and output characteristics from in-service structures.