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Vertical stiffness of the bridge is of paramount importance in guaranteeing optimal driving performance for high-speed railway (HSR) trains. Initially, the Auto Regression and Moving Average model with eXogenous input (ARMAX) model is employed as the surrogate model for the train-bridge (TB) coupling system. Then, the framework for analyzing vertical bridge stiffness is proposed employing the surrogate model, and the relationship between the train response affected by excitation randomness and the vertical stiffness indicators of the bridge is established. Finally, the influence of various factors such as train speed, train type, car body mass, and bridge span on stiffness limit of 400 km/h HSR simple-supported bridge (SSB) is examined. The results indicate that the surrogate model offers a notable advantage in computational efficiency, while maintaining a satisfactory accuracy in predicting the train response. With higher train speeds, lighter car body masses, and longer spans, the demand for stricter bridge stiffness limits becomes more pronounced. Based on the driving performance of the train types analyzed, the recommended stiffness limit is proposed for the prestressed concrete simply supported beam (SSB) bridges used in HSR, with a span length of less than 40 m and operating at a speed of 400 km/h. [ABSTRACT FROM AUTHOR]

Affected by many factors, the local wind environment on the bridge deck is complex and changeable, and it seriously threatens traffic safety. To accurately evaluate the wind field on the bridge deck, this paper develops a system to monitor the actual local wind environment and applies it to field measurement of the wind parameters at different positions of a complex truss girder bridge. The results show that the wind parameters on the bridge deck, including wind speed, gust factor, and turbulence intensity, are different from the bridge site due to the influence of the ancillary facilities. Also, the wind profile of the local wind field on the bridge deck is more in line with the polynomial distribution, which makes the equivalent height of the wind load much higher than the vehicle gravity. It should be noted that the measured power spectrum of the bridge deck is quite different from the wind spectrum applicable to the bridge site area, so it is not appropriate to use the wind spectrum of the bridge site area to carry out the analysis of the windmill bridge, and a more suitable wind spectrum for bridge deck wind field is proposed. [ABSTRACT FROM AUTHOR]

Long span sea-crossing bridges are often slender and sensitive to wind and wave loads. Nonlinear dynamic response analysis of the bridges under three-dimensional (3D) correlated wind and wave loads is performed in this study in consideration of both geometric and aerodynamic nonlinearities. An optimized C-vine copula is first used to construct a 3D joint probability distribution and environmental contour of mean wind speed, significant wave height and peak wave period. Multi-point fluctuating wind loads with Davenport coherence function and random wave loads with pile group effect are then determined using wind and wave spectra respectively. The nonlinear wind-wave-bridge system considering geometric and aerodynamic nonlinearities is solved by the Newmark-β method with the 3D correlated wind and wave parameters as an input. The proposed approach is finally applied to a real sea-crossing cable-stayed bridge with the measured wind and wave data. The results show that the nonlinear response of the bridge is higher than its linear response with the same input. The bridge response is significantly reduced if the 3D correlated wind and wave loads other than conventional uncorrelated wind and wave loads are considered. [ABSTRACT FROM AUTHOR]

Flutter may lead to collapse of long-span bridges and need to be avoided, which makes the estimation of the onset flutter essential for long-span bridge design. However, the efficiency of traditional solution methods of predicting onset flutter is not high. In this study, it is converted into an optimization model, which is solved by a proposed advanced particle swarm optimization (APSO) with a novel inertia weight strategy and mutation mechanism. Two well-known benchmark functions are firstly employed to validate the performance of APSO. Compared with other existing PSO methods, APSO not only has high accuracy, but also has the fastest convergence speed. Then, APSO is used to find the flutter critical wind speed of bridges. A good agreement is obtained comparing predictions on the onset flutter by the proposed methods and available tests on several study cases. In addition, the value range of APSO variables is discussed in depth. It is confirmed that the proposed APSO algorithm has excellent stability, robustness and fast convergence, which is suitable for searching onset flutter of bridges. [ABSTRACT FROM AUTHOR]

Although the wind barrier was set near the bridge tower, more than 10 traffic accidents under crosswinds happen in the bridge tower area within 1 month of the opening operation of a cross-sea bridge. To investigate the wind shielding effect of the bridge tower, a field measurement scheme of wind-vehicle-bridge system, which is a step-by-step test method, was presented and performed on a long span cable-stayed bridge. Firstly, the horizontal profile of wind speed of bridge deck near bridge tower was obtained through the anemometers. Then, the dynamic response of the bridge was measured under the action of normal operating vehicle when the natural wind speed is low. Finally, the response of the moving car was measured when passing through bridge tower, and the wind speed was recorded simultaneously. The results show that the wind-vehicle-bridge system can be tested by step-by-step test method to understand the wind shielding effect of bridge tower. The displacement response of the bridge is still very small when two large trucks meet, and the coupling effect between the vehicle and the bridge is insignificant when a single car passes through the bridge tower. Due to a large porosity of the anti-collision guardrail, the wind speed at the height of 1 m from the bridge deck has changed dramatically when the car leaves the bridge tower on the windward and entering or leaving the bridge tower on the leeward. Among them, the leeward side change is more obvious, and the response of the leeward side vehicle is also greater. The suitable decrease of the anti-collision guardrail porosity in the bridge tower region will improve the running safety of vehicles. [ABSTRACT FROM AUTHOR]

Simply supported bridges occupy the majority of bridges. Compared with the flexible large span bridges, Dynamic Amplification Factor (DAF) of them is relatively large and attracts lots of studies. However, most of these studies are focused on the simplified condition that a single vehicle passes through a single span bridge. In general, the bridge bears complex traffic flow rather than a single vehicle. The vehicle type and dynamic loads on the bridge are thus dispersed. It is necessary to explore the multi-vehicle effects on the DAF caused by the complex traffic flow. Also, adjacent spans of a multi-span simply supported beam bridge may have continuous dynamic effects on the vehicles. In this regard, the DAF of a simply supported bridge considering the multi-vehicle and multi-span effects are explored numerically based on the coupling dynamic analysis of traffic flow and bridge, which can also consider the acceleration and deceleration of the vehicles. Cellular Automata (CA) method is used to simulate the traffic flow. It is found that the worse the driving condition of the road roughness, the greater the DAF. When road roughness is Class C, the DAF exceeds the values of American and Chinese codes. Under the action of traffic flow, DAF of the first span of the multi-span simply supported beam is larger than that of the span under the single vehicle. Only considering the effect of a single vehicle may underestimate the dynamic impact on the bridge. Sparse traffic flow has a larger DAF than moderate traffic flow and dense traffic flow in the statistic meaning of the multi-span, because the driving speed of sparse traffic flow is closer to the resonant speed of the bridge and the vibration disharmony of multi-vehicles is smaller. The greater the deceleration of the traffic, the greater the dynamic impact on the bridge. [ABSTRACT FROM AUTHOR]

Several factors could affect the function of the electromagnet control system when a high-speed maglev train runs over a bridge. To enhance the robustness of the electromagnet control system to the high-speed maglev train running over the bridge, a fuzzy active control rule is introduced into the currently used proportional–integral–derivative (PID) control system. Numerical analyses are then conducted with a high-speed maglev train passing through a series of simply supported beams. The numerical results with the fuzzy PID active control are compared with the maglev train–bridge system with the equivalent linearized electromagnetic forces. The comparative results show that the introduction of the fuzzy PID control system has improved the comfort of the maglev train and that the overall dynamic response of the bridge is reduced. There is an obvious time delay for the maximum dynamic response of the bridge to the high speed of the train. [ABSTRACT FROM AUTHOR]

Vortex-induced vibration (VIV) depends on aerodynamic shapes of bridge girders, which should be treated carefully in the design of long-span bridges. This paper studies the VIV performance of a suspension bridge with the truss girder which contains two separated decks. Although truss girders generally show better VIV performance than box girders, significant vibrations of this type of girders occurred in the wind tunnel tests based on a large-scale sectional model. Several lock-in regions with the same vibration frequency were observed, corresponding to different shedding vortices. Computational fluid dynamics (CFD) simulations were carried out, and monitoring points were set behind different components to study the characteristics of the shed vortices. As the truss girder consists of many members, the results show that various vortices with different dominant frequencies are formed in the wake flow. The vertical VIV of the bridge is probably driven by the vortices behind or above the upper deck, which is related to the guardrails. The torsional VIV of the bridge is probably driven by the vortices behind or below the lower deck, which is related to the service road at lower wind speeds while may be related the vertical stabilizers at higher wind speeds. [ABSTRACT FROM AUTHOR]

Normally strong winds in mountainous areas possess potential threats to the safety of vehicles travelling over the long-span bridges. Generally, decreasing the porosity of the guardrails could improve wind environment for vehicles, while the changed flow field around the bridge's girder may weaken the structural aerodynamic stability simultaneously. To solve the two seemingly contradictory issues, such a long-span suspension bridge in mountainous areas is taken as the case study, and the guardrails are optimized with different schemes. The effects on wind environment for vehicles under normal traffic conditions are first studied by computational fluid dynamics (CFD) simulations. The further effects on the aerodynamic stability of the bridge under extreme winds are then determined by wind tunnel tests, and the observed non-divergent flutter is explainedbythe change in dynamic flow field. Results show that reducing the porosity of guardrails does improve the wind environment above the bridge deck, and the improvement on wind environment increases with the increase in angle of attack. After closing the guardrails completely, however, the girder appears non-divergent vibration different from the linear theoretical flutter when the critical wind speed is exceeded. The different post-flutter behaviors at different angles of attack are mainly related to the synchronization condition between the movement of vortex and the motion of the girder. [ABSTRACT FROM AUTHOR]

This article investigates the vertical vortex-induced vibration of a flat-closed-box girder using numerical simulation method. The accuracy of simulation results is verified at first by comparing the displacement responses and vortex-induced force of vertical vortex-induced vibration with those obtained in a previous wind tunnel test of large-scale sectional model. The precision of extracting the vortex-induced pressures from the surface pressures and decomposing the vortex-induced pressures via the mathematical model is validated later. Subsequently, the vortex-induced pressures and energy distribution, and the evolution laws of vortex-induced pressures and energy are discussed. The results show that the linear aerodynamic negative damping and nonlinear aerodynamic positive damping are key factors of the rapid development of vortex-induced vibration and the self-limiting phenomenon separately. The positive aerodynamic damping is mainly provided by the lower surface and the middle of the upper surface, and the negative aerodynamic damping is primarily provided by the middle and downstream of the upper surface. [ABSTRACT FROM AUTHOR]

Based on the rigid–flexible coupling method, an original scheme for the dynamic analysis of the vehicle–bridge interaction between suspended monorail trains and horizontally curved bridges is proposed. Considering the compression deformation and contact model of walking tire and guiding tire, the geometric and mechanical coupling relationships between vehicle and bridge are studied, and the dynamic equations of suspended monorail vehicle–bridge interaction are derived. A vehicle–curved bridge coupling vibration system is established according to transformable relationship between the local coordinate system and the global coordinate system in SIMPACK. Considering a curved bridge under passage of suspended monorail vehicles as an example, the influences of critical system parameters, such as the superelevation, vehicle speed, and bridge curve radius, on the dynamic responses of vehicles and the curved bridge are explored. It is shown that the direction of the yawing moment of the front bogie is in accordance with the turning direction of the vehicle, while the yawing moment of the rear bogie is in the opposite direction. The superelevation has great influence on the lateral guiding force and vertical walking force of vehicle, and vehicle speed is a key factor to the running safety of suspended monorail vehicle. In addition, the curve negotiation ability of vehicle is better with the increase in bridge curve radius. [ABSTRACT FROM AUTHOR]

Uncertainties from random multiple factors bring great challenges for assessing response of long-span bridges. This study proposes a dynamic analysis framework by integrating the wind–wave–bridge system with Bayesian regularized back propagation neural network, and then investigates stochastic response of a cross-sea cable-stayed bridge under extreme wind and wave parameters. The wind–wave–bridge system involving wind–bridge and wave–bridge interactions is constructed to calculate dynamic response of the bridge by Newmark-β method, considering stationary fluctuating wind fields and multidirectional random wave fields. To reduce the calculation cost, a Bayesian regularized back propagation neural network model is introduced, and the model evaluation is carried out to illustrate its accuracy and efficiency. After performing small-scale finite element analyses, the response statistics are obtained and later used as the known samples for training the neural network. The power spectrum analyses of the deterministic results are performed to investigate the contribution mechanism of the wind and wave. Finally, the correlation between the bridge response and the single wind–wave parameter is given by uncertainty analysis of the Bayesian regularized back propagation neural network model. The results show that the proposed framework is capable of capturing the nonlinear bridge response resulting from nonlinear wind and wave loads, which, however, is significant different from that under wind alone. The bridge response receives significant contribution from wind and waves relative to the vibration characteristic of the bridge at smaller wind and wave loads. The contribution from vibration characteristic of the bridge becomes significant at larger wind and wave loads. The uncertainty analyses illustrate the significant effects of four wind and wave parameters on girder, tower, and submerged structure. [ABSTRACT FROM AUTHOR]

Wind environment in mountainous areas is very different from that in coastal and plain areas. Strong winds always show large angles of attack, affecting the flutter stability of long-span bridges which is one of the most important design factors. The central vertical stabilizer has been demonstrated to be an effective aerodynamic measure to improve the flutter stability, and this article optimizes the stabilizer to improve its applicability in mountainous areas. Computational fluid dynamics simulations are first performed to analyze the effects of stabilizers with different positions and forms on the flutter stability of an ideal box girder, and the aerodynamic mechanism is discussed based on the static and the dynamic flow fields, respectively. Wind tunnel tests are then carried out to test the critical flutter wind speed of a real box girder equipped with different stabilizers, and the change in its flutter stability is further analyzed. The results show that the vertical stabilizer with appropriate positions and heights can improve the participation level of structural heaving vibration, and thereby increases the flutter stability. At large angles of attack, the big vortex on the leading edge which may drive the bridge to flutter instability is gradually weakened with the increase in stabilizer's height. Compared with a single stabilizer, double vertical stabilizers, in the midst of which exists a negative pressure region, could achieve better effects. [ABSTRACT FROM AUTHOR]

The typical U-shaped deep-cut canyon is widely distributed in the western mountainous areas of China, especially in Sichuan province and Yunnan province. The deep-cut canyon has the characteristics of the high drop in elevation, high-temperature difference, and complex wind environment. A 50 m high meteorological mast with a total of eight anemometers was erected in such topography, and a long-span suspension bridge will be constructed in the area where the meteorological mast is located. Based on the long-term monitor data, the wind characteristic parameters including average and fluctuating wind characteristics and coherence between different heights are investigated. The results are as follows. The dominant wind direction which depends on the topography is north–south. The attack angle of wind is mainly less than zero, and its probability distribution obeys the hypothetical Gaussian distribution. Both the increases in height of anemometer and in wind speed reduce the dispersion of the attack angle of wind. The gust factor has a similar change law of attack angle of wind. Turbulence intensities are affected by the height of the anemometer and the wind speed, and they are different from the recommended value of China Codes. In terms of turbulence integral length scale, the value increases with an increase in the height of the anemometer in the same component. The largest value occurs in the longitudinal direction and the smallest occurs in the vertical direction at the same level. The coherence between any two locations is relatively strong, and the longitudinal component is stronger than others. The measured wind power spectrum for longitudinal, lateral, and vertical wind in deep-cut canyon fits the von Kármán model better. [ABSTRACT FROM AUTHOR]

To improve the efficiency of reliability calculations for vehicle-bridge systems, we present a surrogate modeling method based on a nonlinear autoregressive with exogenous input artificial neural network model and an important sample, which can forecast responses of dynamic systems, such as vehicle-bridge systems, subjected to stochastic excitations. We also propose a process to analyze the method. A quarter-vehicle model is used to verify the proposed method's precision, and the nonlinear autoregressive with exogenous input artificial neural network model is used to predict responses of vertical vehicle-bridge systems. The results show that, compared to other training samples, the nonlinear autoregressive with exogenous input artificial neural network model has better prediction accuracy when the sample with the maximum response is considered as an important sample and is used to train the nonlinear autoregressive with exogenous input artificial neural network model, and it requires only two-time numerical simulation (or Monte Carlo simulation) at most, which is used in the training of the nonlinear autoregressive with exogenous input artificial neural network model. [ABSTRACT FROM AUTHOR]

Based on the theory of pseudo excitation method, a so-called stochastic pseudo excitation method is proposed to acquire the sampling results of stochastic dynamic response of uncertain bridge structure directly, which cannot be achieved by the classical pseudo excitation method. In order to reduce the computational cost of the dynamic finite element analysis of the samples to gain the probability density function of structural responses, the response surface method was adopted to handle the sampling results. The stochastic pseudo excitation method combing response surface method is verified by comparing with Monte Carlo method in good agreement. As an example, the stochastic response of a super-high slender bridge tower subjected to the Davenport fluctuating wind excitations is evaluated taking into account the uncertainties of material properties and wind speed. Numerical results show that the effect of uncertainties of structure or excitations plays a constant role in the stochastic response at the different levels of external excitations. [ABSTRACT FROM AUTHOR]

A growing number of long-span bridges are under construction across straits or through valleys, where the wind characteristics are complex and inhomogeneous. The simulation of inhomogeneous random wind velocity fields on such long-span bridges with the spectral representation method will require significant computation resources due to the time-consuming issues associated with the Cholesky decomposition of the power spectrum density matrixes. In order to improve the efficiency of the decomposition, a novel and efficient formulation of the Cholesky decomposition, called "Band-Limited Cholesky decomposition," is proposed and corresponding simulation schemes are suggested. The key idea is to convert the coherence matrixes into band matrixes whose decomposition requires less computational cost and storage. Subsequently, each decomposed coherence matrix is also a band matrix with high sparsity. As the zero-valued elements have no contribution to the simulation calculation, the proposed method is further expedited by limiting the calculation to the non-zero elements only. The proposed methods are data-driven ones, which can be applicable broadly for simulating many complicated large-scale random wind velocity fields, especially for the inhomogeneous ones. Through the data-driven strategies presented in the study, a numerical example involving inhomogeneous random wind velocity field simulation on a long-span bridge is performed. Compared to the traditional spectral representation method, the simulation results are with high accuracy and the entire simulation procedure is about 2.5 times faster by the proposed method for the simulation of one hundred wind velocity processes. [ABSTRACT FROM AUTHOR]

The sea-crossing railway bridge is exposed to a high risk of wind and wave, which threatens the safety of the bridge and railway. A wind–wave–vehicle–bridge dynamic analysis model for sea-crossing railway bridge under wind and wave loadings is developed by extending the previous wind–vehicle–bridge model. The developed wind–wave–vehicle–bridge model involves multipoint fluctuating wind field, irregular wave field, finite element model of the bridge, and mass–spring–damper model of the vehicle. The correlation between wind and wave is considered by an empirical curve derived based on field measurement. Static, buffeting, and self-excited wind forces on the bridge and vehicle are considered with coefficients obtained from wind tunnel tests. The wave forces on the bridge are calculated by Morison equation including stretching modification. The governing equations of the wind–wave–vehicle–bridge model are solved in time domain by Newmark-β method to compute the dynamic response of bridge and vehicle. The dynamic response of bridge and vehicle is compared and discussed in both wind–wave–vehicle–bridge and wind–vehicle–bridge model. The performance of bridge and vehicle are finally evaluated. Studies of dynamic response under correlated wind and wave are found to be imperative for assessment of structural and vehicle safety and driving comfort of sea-crossing railway bridge. [ABSTRACT FROM AUTHOR]

In order to study the variation of wind field characteristics under the influence of thermal effects at a bridge site in a deep-cutting gorge with high-altitude and temperature difference, the simulation of natural convection was realized by adding momentum source terms in FLUENT. And the correctness of the simulation results was verified. Then, choosing Dadu River Bridge located at a deep-cutting gorge in western Sichuan as an engineering background, combined with the variation of temperature tested at the bridge site, the numerical simulation of the wind field characteristics at the bridge site was carried out under the influence of the thermal effects. The influences of different thermal factors on the surface wind characteristics of bridge site area were discussed. The wind characteristics at the bridge site under the combined action of different wind velocities and thermal effects were analyzed. As shown in the results, the maximum vertical wind velocity caused by the thermal effects at the height of main girder is 3.0 m/s, and the maximum horizontal wind velocity is 6.4 m/s. When the upcoming wind velocity is greater than 5.0 m/s, the thermal effects have been significantly reduced, and the wind field at the bridge site is mainly influenced by the upcoming wind velocity, wind direction, and local terrain. Under the influence of thermal, the surface temperature distribution at the bridge site is significantly uneven, which are obviously different from the case of not considering the thermal effects. [ABSTRACT FROM AUTHOR]

To improve the flutter stability of a long-span suspension bridge with double-decks, aerodynamic optimization on the upper and lower bridge decks is studied, and a series of countermeasures are considered, including slotted deck, wind fairings, porosity of guardrail, and horizontal and vertical stabilizers. Wind tunnel tests were performed to measure the critical flutter wind speed of the bridge and find effective aerodynamic countermeasures for improvement of the flutter stability. The results show that double-vertical stabilizers symmetrically installed at the two sides of the bottom of the lower deck with the distance of 9.32 or 11.55 m to the center efficiently improve the flutter performance of the original section at −3°, 0°, and 3° angles of attack simultaneously, while other common aerodynamic measures can hardly achieve this effect alone. The composite measure which consists of two central stabilizers installed on the top of the upper and lower decks, respectively, is promise and superior to the single measure. The combination of wind fairing and central stabilizer on the top of the lower deck is also an effective countermeasure. The results can provide the reference information for flutter optimization of the long-span steel truss girder suspension bridge with double-deck in the future. [ABSTRACT FROM AUTHOR]

The assessment of wave conditions is a primary task for the design, construction, and structural analysis of sea-crossing bridge. This article presents a numerical simulation and a field measurement to study the wave conditions in the nearshore island area for sea-crossing bridges. Pingtan Strait sea-crossing bridge site was selected as an example of nearshore island area. A 3-day high-energy wave event was measured and simulated using spectral wave model. The parameters of the numerical model were calibrated through the comparison with the field measured wave data. The spatial pattern of wave conditions along the bridge and the wave-breaking zone were analyzed based on the calibrated model. The analytical procedures suggested in the Chinese Code for nearshore wave prediction were finally testified through the comparison with numerical results. The research showed that (1) spectral wave model predicts the wave conditions in bridge site reasonably; (2) seabed terrain and islands significantly influence wave conditions, wave spatial pattern, and breaking wave zones; and (3) analytical wave simulation procedure recommended in the Code is not suitable to island area for sea-crossing bridge. This research allows a better understanding of wave conditions for sea-crossing bridge site and could provide useful reference for engineering practice. [ABSTRACT FROM AUTHOR]

To analyze the effects of a central stabilizer on the flutter performance at large angles of attack, this study takes the ideal plate as a section of a bridge deck. The aerodynamic characteristics of stationary cross sections are examined using computational fluid dynamics simulations, and the flutter derivatives are extracted by forced vibration. The critical flutter speed of a target bridge is then calculated, and the aerodynamic mechanism of the central stabilizer is discussed from the work done by aerodynamic forces’ perspective. The results show that use of a central stabilizer with lower heights favors flutter stability at smaller angles of attack by improving the participation level of heaving motion, but the stability of the systematic heaving motion will decrease if the stabilizer is too high, leading to galloping. At larger angles of attack, where the movement of a big vortex causes the occurrence of torsional flutter, the stabilizer can hinder the movement of the vortex if they are on the same side, and the critical flutter speed increases with the increase in stabilizer height. [ABSTRACT FROM AUTHOR]

This study takes an ideal thin flat plate as a bridge deck section and derives its flutter derivatives at different angles of attack as well as different wind directions using computational fluid dynamics simulations. The effects of wind velocity distribution, angle of attack, and wind direction on flutter performance of a long-span suspension bridge under non-uniform inflow are then analyzed by the finite element program ANSYS. The results show that the adverse effects of higher wind velocities or larger angles of attack on the flutter performance of bridge are more remarkable than the beneficial effects of lower components when the inflow is non-uniform, leading to the reduction of flutter stability, and the decreasing range increases with the increase in non-uniformity of inflow. Moreover, the flutter critical state of bridge could be even controlled by the antisymmetric torsional modal branch if the inflow with a larger angle of attack at which the streamlined plate presents the characteristics of a bluff body acts on the two ends of bridge simultaneously. For skew wind, increasing yaw angle is favorable to the improvement of the flutter critical wind speed of bridge, but the flutter performance is mainly governed by lower yaw angles when the inflow is non-uniform. [ABSTRACT FROM AUTHOR]

The wind tunnel test is conducted to measure the wind loads of a train and the wind pressure distribution above track. The dynamic responses of vehicle are calculated by using the coupling vibration method of wind-vehicle-bridge (line) systems with the aid of the self-developed software BANSYS(Bridge Analysis System) to determine the protection effect of wind barrier. Three kinds of porosities and four kinds of heights are installed on three line structural forms. The aerodynamic mechanism of wind barriers on the railway is investigated and the effects of sudden changes of vehicle wind loads are examined by measuring the aerodynamic coefficients of a single train. The quantity of wind loads' sudden change and the dynamic responses of vehicles is considered as the input index. The protection effect of wind barrier is evaluated by data envelopment analysis (DEA) when the output is the same. The results show that the wind barrier with a certain height could increase the lift-drag ratio and is more likely to increase the lift coefficient. The method of comprehensive evaluation can be applied in the protection effect evaluation of the railway wind barrier and the comprehensive evaluation using the indexes of sudden change of vehicle wind loads is in agreement with the vehicle response index. [ABSTRACT FROM AUTHOR]

In most currently-used analytical models for studying rain-wind induced cable vibration, wind velocity relative to cable motion was determined by trigonometric decomposition and the aerodynamic coefficients of a cable were measured through wind tunnel tests using a horizontal cable model with two-dimensional flow field. In this paper, the aerodynamic coefficients of a cable were measured using a spatial cable model with a three-dimensional flow and an analytical model was developed to predict rain-wind induced cable vibration. The feasibility of the proposed analytical model was examined through the comparison with wind tunnel test results. The mechanism of rain-wind induced cable vibration was also investigated from viewpoints of rivulet motion and system energy. Further, an extensive parametric study was carried out in this study to investigate the properties of rain-wind induced vibration of a stay cable. The observation indicates that rain-wind induced cable vibration is essentially similar to cable galloping with limited amplitude, which is mainly induced by negative slope of lift coefficient curve and rivulet oscillation. The results from the parametric study indicate that the aerodynamic and motion parameters of cables may affect the maximum amplitude and the wind speed range for the occurrence of rain-wind induced vibration. [ABSTRACT FROM AUTHOR]

The present study was conducted to identify the difference of the relationship between lifestyle behaviors with hypertension (HTN) by various body mass index (BMI) categories. A cross-sectional study was conducted among Tianjin urban communities. A total of 26 438 subjects were randomly selected. The authors evaluated associations of lifestyle behaviors with HTN among normal, overweight, and obese adults using a hierarchical logistic model considering the gross domestic product of residence as socioeconomic proxy. A positive association was found between BMI and the risk of HTN among male and female subjects. Current smoking was associated with a higher risk of HTN in overweight (odds ratio [OR] = 1.19, 95% confidence interval [CI] = 1.04-1.36) and obese groups (OR = 1.20, 95% CI = 1.03-1.53). There were statistically significant associations of current drinking with risk of HTN in normal weight (OR = 1.18, 95% CI = 1.01-1.31) and overweight groups (OR = 1.22, 95% CI = 1.07-1.40). The prevention of overweight and obesity is important in preventing HTN. Additionally, adherence to healthy lifestyle is associated with less risk of HTN in various BMI categories. [ABSTRACT FROM PUBLISHER]