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The hangers represent the crucial load-bearing component of arch bridges and are susceptible to dynamic vehicle load. However, little effort has been made to carry out dynamic analysis of arch bridge hangers under high-speed train loads. This paper presents an investigation of the dynamic behavior of the arch bridge subjected to high-speed train with emphasis on the flexible hangers, using train–bridge interaction simulation and field measurement data. Coupled train–bridge system model composed of three-dimensional train model, bridge model, and wheel–rail interaction model is established to account for hanger transverse vibration, spatial train loading, and track irregularity excitation, among others. Vibration data of bridge components including the hanger are measured through field test on a typical high-speed railway tied-arch bridge. A total stress-based dynamic amplification factor is subsequently proposed to describe the effect of hanger transverse vibration. The influence of significant parameters such as train speed and track irregularity on the dynamic effects of hangers is examined by the experimentally validated train–bridge interaction model. It is found that the dynamic responses of the hangers are considerably different from bridge global responses. In-plane and out-of-plane transverse vibrations of the hanger result in a large increase in the hanger dynamic effects which prove to be sensitive to train speed, track irregularity, train loading position, etc. Moreover, the dynamic amplification factor formula in the current high-speed railway code may not be sufficient to characterize the dynamic amplification of hangers under operating conditions.

Four commercial urban maglev lines have already been put into operation, demonstrating the safety, comfort, environmental sustainability, and low maintenance of this innovative rail transit system. To further promote and apply this technology, reducing line construction costs has now become a priority. The deflection-to-span ratio limit of the girder plays a significant role in determining the construction cost of commercial lines. According to Chinese standards, the vertical deflection-to-span ratio limit for simply supported girders under maglev train loads is set at 1/3800 to prevent strong coupling vibrations between the maglev train and the girder, which could lead to levitation failure (i.e. the collision between the electromagnet and the rail). However, the current deflection-to-span ratio used in commercial lines is smaller, contributing to the high construction costs of commercial lines. To investigate whether the deflection-to-span ratio can be reduced, a 25m span variable-stiffness steel girder was designed and manufactured, with the deflection-to-span ratio range between 1/2000 and 1/4500. A coupled dynamic model of the maglev train-controllable electromagnetic force-variable stiffness girder was then established. Tests were conducted to analyze the dynamic responses of a single-car maglev train traveling over the variable stiffness girder at speeds of 20–60km/h, with the results being used to validate the numerical model. The coupled dynamic simulation analysis was also performed for the three-car maglev train traveling at speeds ranging from 20km/h to 100km/h. By focusing on levitation gap fluctuations and ride quality, the study discussed an optimal deflection-to-span ratio for the 25m span girder. Simulation results indicate that, regardless of the deflection-to-span ratio of the girder, the vertical accelerations of both the levitation bogie and the F-shaped rail initially decrease with increasing speed, then gradually increase. However, the vertical accelerations of both the carbody and the girder increase consistently with speed. As the deflection-to-span ratio decreases, the dynamic response of the coupling system gradually decreases. The deflection-to-span ratio of 1/2970 is optimal, ensuring both the safe and smooth operation of the maglev train while significantly reducing construction costs.

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The Chi-Chi Earthquake that struck Taiwan in 1999 damaged a 250 m tall chimney located in central Taiwan. To understand the dynamic behavior, failure trigger mechanism, and seismic performance of the chimney that has been rehabilitated, a study using experimental and analytical approaches was carried out. The ambient vibration test, together with a system identification approach, was used to evaluate the dynamic characteristics of the chimney. A subspace approach with an instrumental variable concept was used in the system identification. The dynamic behavior of the chimney was also simulated by a 3D finite element analysis using the commercial software SAP2000. Finally, the design code of ASCE 1975 was adopted to check the buckling capacity of the steel flues in the chimney structure. The results indicated that the calculated stresses correspond well with the actual damages observed in the steel flues.

To determine its actual dynamic responses under the wind loads, modal identification from the field tests was carried out for the Kao Ping Hsi cable-stayed bridge in southern Taiwan. The dynamic characteristics of the bridge identified by a continuous wavelet transform algorithm are compared with those obtained by the finite element analysis. The finite element model was then modified and refined based on the field test results. The results obtained from the updated finite element model were shown to agree well with the field identified results for the first few modes in the vertical, transverse, and torsional directions. This has the indication that a rational finite element model has been established for the bridge. With the refined finite element model, a nonlinear analysis in time domain is employed to determine the buffeting response of the bridge. Through validation of the results against those obtained by the frequency domain approach, it is confirmed that the time domain approach adopted herein is applicable for the buffeting analysis of cable-stayed bridges.

The contact between a vehicle tire and the road surface has been usually assumed as a single-point contact in the numerical simulation of vehicle–bridge interacted vibrations. In reality, the tire contacts the road surface through a patch instead of a single point. According to some recent studies, the single-point tire model may overestimate the dynamic amplification of bridge responses due to vehicle loadings. A new tire model, namely, the multi-point tire model, is therefore proposed in this paper with the purpose of improving the accuracy of numerical simulation results over the single-point model, while maintaining a certain level of simplicity for applications. A series of numerical simulations are carried out to compare the effect of the proposed tire model with those of the existing single-point model and disk model on the bridge dynamic responses. The proposed tire model is also verified against the field test results. The results show that the proposed multi-point tire model can predict the bridge dynamic responses with better accuracy than the single-point model, especially under distressed bridge deck conditions, and is computationally more efficient and simpler for application than the disk model.

The presence of intermediate supports usually imposes difficulties in identifying the tension force of stayed cables in cable-stayed bridges or hanger cables in arch bridges. This paper establishes the partial differential equations of motion of the cable and derives two numerical models with (Model 1) and without (Model 2) considering the flexural rigidity. The effects of two intermediate supports on the identification accuracy of the cable tension force are further studied analytically and experimentally. The effects of several non-dimensional parameters (e.g. damper location, support stiffness, flexural rigidity, and mode order of the cable) on the identification accuracy of the models are also investigated. It is theoretically concluded that the simplified Model 2 provides acceptable accuracy on tension force identification when the non-dimensional parameter $\xi$ is greater than 90 (slender cables), whereas the accurate Model 1 can be applied for tension force identification at any scenarios. The feasibility of two models is further verified by three numerical examples and field tests on two real-world arch bridges.

This paper aims to study the transfer laws of vibration signals in the free field near a high-speed train line by conducting a field test. The characteristics of ground vibration acceleration were analyzed in the time and frequency domains, and a prediction method in the frequency domain was proposed. The results show: (1) there is a vibration amplification area away from the bottom of the pier under the influence of high-speed trains running over the bridge due to the fluctuation attenuation of the vibration waves; (2) the dominant peak frequency points in the frequency spectrum of the acceleration can be regarded as the resonance frequency induced by periodic loading; and (3) the soil vibration can be effectively predicted by the proposed method with a strong capability to defend the interference of environmental vibrations according to the comparison between the predicted value and the experimental data.

Suspended monorail transportation (SMT) plays an important role in alleviating the urban traffic pressure, and its vehicle–bridge dynamic features are significantly different from those of the traditional railway. To grasp the coupled vibration features of suspended monorail train–bridge system (SMTBS), this paper presents a comprehensive experimental investigation on the vehicle–bridge vibrational responses under different operating conditions. First, based on the Chengdu SMT test line in China, a full-scale field measurement of the coupled vibration responses of the SMTBS is elaborately conducted under constant speed conditions. Then, the vibrational responses of the SMTBS are analyzed in the time and frequency domains to reveal its coupled vibration features and vibration transmission characteristics. Further, considering an extreme train operating condition, the vibrational responses of the SMTBS are tested and analyzed under train emergency braking; and the vibration features of the vehicle and bridge are examined for emergency braking, along with several key indexes evaluated for the train braking performance. Results show that the vibrational accelerations transmitted from the frame to the center pin and then to the carbody will be significantly decreased in turn, and the vibrational dominant frequencies of the bogie, center pin, and carbody mainly fall with 0–100Hz, 0–50Hz, and 0–20Hz, respectively. Under moving train loads, the box beam produces plentiful high-frequency vibrations and the vibrations transmitted from the driving track to the top plate are drastically reduced. The train braking significantly intensifies the car-body longitudinal vibration; however, it has small influences on the car-body vertical and lateral vibrations.

With the ongoing development and deployment of medium-low speed maglev vehicles in China, it has become common to increase operational speeds from 100km/h up to 140km/h or even 160km/h, necessitating further studies and simulation models to understand the implications of these changes. This paper analyzes medium-speed maglev vehicle-track-girder coupling dynamic performance at a speed of 160km/h. First, a field dynamics experiment is carried out on the Changsha Maglev Express with a running speed of 80–140km/h. Then we introduce the distributed coupling simulation platform for maglev transportation system (MTS-DCSP) and the vehicle-track-girder coupling model, taking into account the complex vehicle structure, the guideway structure, and the Proportion Integral Differential (PID) levitation control system. Together, this platform and model can conduct a simulation of the complete process at scale and at all degrees of freedom to obtain accurate results. Our analysis of the results gives an accurate portrayal of the coupling dynamics properties and validates the coupling model. The results from the field experiments together with the coupling simulation demonstrate that the medium-speed maglev train can operate safely and stably within the range of 140–160km/h. While at 140km/h, however, the Sperling ride quality index (RQI) is about 2.5, which is within the Excellent grade range, at a speed of 160km/h, the Sperling ride quality index can increase to as high as 2.74, which is a grade of Good. Therefore, it is necessary to optimize the parameters of the secondary suspension system to improve the ride comfort of the maglev vehicle at 160km/h.

This research elucidates the influence of the 60N rail profile on the dynamic interaction between wheel and rail, and the dynamic performance within the turnout. The influence of the 60N profile on the long-term service efficiency of turnouts was scrutinized. Subsequently, an optimization approach for the 60–60N rail combination profile was suggested. The main conclusions are as follows: (1) During the passage in the main direction, the 60N rail profile enhances driving stability and mitigates the progression of wear. However, it causes focalized wheel–rail contact on the rail head and escalates contact stress. (2) During the passage in the branch direction, the 60N rail profile amplifies the lateral dynamic force and rail wear rate in the closure panel, engendering two-point contact and increased contact stress. (3) In the early stage of field service of turnouts, a robust correlation exists between the contact band and the rail profile. In the fragile cross-section of the point rail, the contact band of the 60N rail profile turnout fully occupies the rail head, potentially causing stress concentration on the non-working edge position. By the stable service period, the wheel–rail contact band is mainly influenced by total weight. (4) An optimization method for the 60–60N combination profile was proposed with the corresponding machining tool profile designed. This strategy can avoid the profile transition before and after the turnout, reduce field maintenance workload, enhance running stability of straight passage through the turnout, and preclude fatigue damage in the weak cross-sections of the point rail.

Train vibrations are the primary concern in environmental engineering and civil engineering. It is significantly imperative to find new methods for reducing and isolating vibrations. The locally resonant metamaterials (LRMs) propose a novel method and concept for reducing train vibration. However, the accurate and quick design structures of LRMs based on vibration characteristics are still an issue. Thus, this study presents a novel inverse design model of three-component locally resonant metamaterial barriers (LRMBs) for vibration reduction based on deep learning. The bandgap characteristics and vibration modes of the LRMB are investigated by using the improved plane wave expansion (IPWE) and finite element method (FEM). Besides, the gradient-combined LRMBs are proposed based on time–frequency features of measured vibration caused by trains and the novel inverse design model, and a two-dimensional finite element model coupling with infinite element boundaries is established to study the reduction efficiency of the gradient-combined LRMBs. And the performances of different LRMBs are fully analyzed in time and frequency domains. The results show that the novel inverse design model can be successfully used to design the LRMB based on vibration features. Moreover, the gradient-combined LRMBs have better isolation performance.

An increase in the nonlinearity of the bridge will lead to a more obvious vehicle–bridge interaction effect and affect the vehicle response and driving comfort as the span increases. This paper establishes a refined finite element model of vehicle–bridge coupling for the 575 m long-span concrete-filled steel tubular arch bridge, Pingnan Third Bridge. Coupling vibration responses under different vehicle speeds, vehicle weights and road conditions of this bridge is analyzed. Then its comfort is assessed according to the comfort criterion. The results show that the vehicle–bridge coupling model has good agreement with the field test. The dynamic response of the bridge within the speed limit has no significant linear relationship with the magnitude of the vehicle speed without considering the pavement class. When the vehicle exceeds the speed limit, the dynamic response increases sharply with the increase in speed. The increase in vehicle weight leads to an increase in the maximum dynamic deflection of the bridge and a decrease in the impact coefficient, but the actual total response of the bridge does not decrease. The worse the road surface condition, the more dramatic the dynamic response of the bridge structure, taking into account the road surface level.

Application of a mechanical circulator was considered to reduce hypoxia and anoxia in an estuarine trench by numerical examination in terms of the required flow rate and direction along with the physical mechanism of its effectiveness. We then developed a prototype of the circulator, generating downward flow by an impeller attached to the main body of the circulator floating on the surface, in which the surface water is being transported to the bottom through a flexible draft tube connected to the floating body. The effectiveness of the proposed mechanical circulator was verified by performing field tests in a dredged trench in Tokyo Port of Tokyo Bay, while monitoring current and water and sediment quality. The field test results showed that the mechanical circulator achieved the desired effects, including reduction in hypoxia and improvement of water and sediment quality in the trench. We also applied a primitive equation model and found that the model can successfully reproduce the field test results. The present study shows the availability of a mechanical circulator and an effective application methodology in the field.

Ready-mixed shotcrete is dry-mixed at the plant before delivering to the site for pouring, making it possible the accurate aggregate quality control and improved construction quality thanks to standardized material. In this study, maximum size of the coarse aggregate for ready-mixed shotcrete was determined and the problem of material segregation at the production process at the plant could be solved through pilot plant test. Furthermore, comparison in quality with existing field mixing method was carried out through field application evaluation.

As the world’s first time implementation of MR-based smart damping technique in bridge structures, a total of 312 semi-active magneto-rheological (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 experiments and tests: (i) modal tests of undamped cables, (ii) forced vibration tests of MR-damped trial cables, (iii) monitoring of MR-damped and un-damped cable responses under rain-wind excitations, (iiii) comparative tests using different damper setups, (v) full installation, and (vi) field measurements and real-time control tests after the installation. After briefly introducing the above six stages of the whole project and addressing the experience and lessons learned from them for both the open-loop control and closed-loop control, this paper will focus on the design considerations on cable vibration control using MR dampers, taking into account the effect of the damper stiffness, damper mass, stiffness of damper support, nonlinearity of the damper, and sag and inclination of the cable. Some issues will be addressed on designing an improved MR-damper particular for application to bridge cables, based on the theoretical studies and several stages of field tests in the cable-stayed Dongting Lake Bridge, which have been being carried out for three years.

According to the reinforcement on pre-stressed anchor cable frame of a slope design, based on the field test to study the stress distribution and stress-strain characteristics of pre-stressed anchor cable frame system in the slope reinforcement. Through the testing of internal force of frame structure to acquire the internal force distribution of framework in different loads and the maximum bending moment position of beam and vertical rib of frame, the results showed that the maximum tensile bending moment are located around the anchor hole and the minimum bending moment which is in a state of compression in the middle of a beam (or vertical rib); also the safety of Winkler elastic beam theory to calculate bending moment is verified. Carried on the strain test for the anchoring sections of a pre-stressed anchor cable under concentrated tension (PACCT) and a pre-stressed anchor cable under dispersive pressure (PACDP) to acquire the strain distribution of anchoring sections when the different types of anchor cable is working, calculated the maximum shear stress positions of different types of anchor cable's anchoring sections, the calculating results show that the peak value of PACCT's shear stress is located at the bottom of the grout and the peak value of PACDP's shear stress is located near the anchoring steel bearing.