In order to solve the data correlation of the vehicle load effect and make full use of the data samples, the modified method of independent storms (MMIS) is proposed. First, a triple class threshold method is proposed to obtain the threshold by primary data analysis. Then considering that the vehicle load effect of simply supported beam bridge is mainly affected by the single heavy vehicle, the MMIS is adopted to extract the independent and identically distributed (IID) data. Finally, the extreme vehicle load effect is estimated by generalized Pareto distribution. In the end, the estimation of extreme vehicle load effect is performed on the measured data of the bridge recorded by weigh-in-motion (WIM) and compared with the peak-over-threshold method and method of independent storms. The results show that within the short estimation period (T<20 years), all the three methods can better estimate the extreme load effect, while within the middle or long estimation period, the estimation of the modified method of independent storms is higher and safer.

 

Based on FLUENT software, the wind field and wind-driven rain around a 2MW horizontal axis wind turbine are analyzed under the condition of rated operation and 50mm/h storm. It is shown that a large number of raindrops flow separated from both sides of the wind turbine with the wind, only parts of raindrops impact the windward of wind turbine, some raindrops on the wake area flow back and hit the leeward of wind turbine. 99% of the raindrops impacting the wind turbine are below 2.5mm in diameter. Flow field suddenly changes when airflow flow past the wind turbine, the adjustment of raindrops speed lag from the change of wind speed, causes the final horizontal speed of raindrops no longer equal to the horizontal wind speed. The rain load on wind rotor and nacelle can be ignored when the wind turbine operated in rainstorm weather, but the rain load on the tower should be counted for its value is more than 12% of tower wind load. 
 

In order to deeply study the non-smooth dynamic mechanism of self-excited vibration, the friction self-excited vibration system model containing the Stribeck friction model is established, which is a nonlinear dynamical mass-spring-belt model. Secondly, the bifurcation characteristics of the system under different parameters are analyzed by using numerical simulation method. The results show that feed speed, damping coefficient and ratio of dynamic-static friction coefficient are the main factors affecting the system motion state. Quasi-period fluctuation happened in low feed speed region and the supercritical Hopf bifurcation appeared at the system when the feed speed is 0.4944. The system appeared to be the similar rules with different damping coefficient and ratio of dynamic-static friction coefficient. Thirdly, the Washout filter method is designed to control the bifurcation phenomenon existed in the system. By contrast the phase diagrams pre and post, results show that the amplitude of controlled system is reduced and the topology is improved obviously after introducing the Washout filter. All demonstrate adding Washout filter into the system to control the bifurcation phenomenon is a more effective method.

 

Because strong pulse electromagnetic interference (PEMI) has high energy and no regularity, and it pollutes signals seriously, we proposed a new denoising method to solve this problem. According to the different structure between signal and PEMI, the unit pulse atom was constructed to match PEMI, and the sine atom, cosine atom and wavelet atom were chosen to match signal. Unlike common filtering ways of sparse decomposition, the PEMI was firstly taken as signal component, and all the atoms above were used to decompose the original signal. Second, only the component matched by sine atom, cosine atom and wavelet atom was used to reconstruct the unpolluted signal, and the component matched by unit pulse atom was eliminated as PEMI. Simulations and applications testified that this technology could filter strong PEMI, the filtered signal not only has high signal to noise ratio, but also retain details.
 

In order to study cavitation characteristics of a centrifugal charging pump in nuclear power plant，the first prototype was specially made. Pro/E and ICEM software were respectively used to be the tools of three-dimensional modeling and meshing of the hydraulic machinery. The cavitation was divided into four stages: cavitation inception，cavitation development，critical cavitation and fracture cavitation. Based on SST k-ω turbulence model，cavitation numerical simulation was finished by ANSYS CFX software. The results showed that: with the occurrence of cavitation，number of bubbles in the radial position in the impeller increases rapidly，and bubble volume fraction is also growing. Vortex appears gradually in the impeller and it leads to sharp decline in pump head in fracture cavitation. （修改后：When cavitation occurs to a certain extent, vortex appears in the impeller and its area constantly increases.）Pressure pulsation is regular in cavitation inception and dynamic and static interference of the impeller and the volute plays a main role；then cavitation gradually becomes the main factor of controlling pump pressure fluctuation rules. In the maximum flow rate condition，head error of simulation and experimental results is 2.1% and NPSH error is 3.5%. The change trend of numerical results and test results are same and they reveal changes of internal flow field of the charging pump indifferent cavitation conditions.
     

The dynamic responses of layered saturated ground-track-train coupling system are studied by the semi-analytical method. The layered saturated ground is composed by arbitrary horizontal saturated layers and the underlying saturated half-space. The track is composed by the rail, the sleepers and the blast. The rail is regarded as an infinitely long Euler beam; the sleepers are represented by a continuous mass and the ballast is accounted for by introducing the Cosserat model. The vehicle is described as a multi-rigid-body system connected by the spring and damping elements. The dynamic loads are assumed to be generated from the rail surface irregularities. The dynamic responses are first obtained in the frequency-wave number domain and then are transformed into the time-space domain by inverse Fourier transformation. Finally, the dynamic responses in the time-space domain are obtained by using inverse Fourier transform. The exactness of the method is verified and numerical calculation and analysis are performed. The study shows that, for low vibration frequencies induced by track irregularities, the ground surface displacement amplitudes increase gradually with the increase of the velocity, while for high vibration frequencies, the maximum displacement amplitudes seems insensitive to the velocity, but the amplitudes vibrate more seriously and the durations of the vibration become longer.
 

To investigate the working performance of twin flapper-nozzle servo valve in theory, the accurate mathematic model of servo valve needs to be established. In the view of electromechanical coupling characteristics of the servo valve, so the bond graph method was introduced with the advantage in modeling complex and dynamic multi-energy domains system. According to the geometric relationship between the armature, baffle component and the main valve, the bond graph model of the servo valve was obtained based on the working mechanism, the nozzle jet fluid power and other nonlinear factors were taken into consideration in the model, and the system state-equations describing energy input, transfer, translation and dissipation of the servo valve were deduced. Numerical simulation based on four order Runge-Kutta method was studied with parameters in the experiment. The results show that the trend of load flow rate step response can agree well with the experimental results, the system internal parameters response can be predicted by t-he model during the working process, and that this modeling method provides a theoretic-al basis for the optimum design and dynamic analysis of the servo valve.
 

Considering the swing of the suspension weight, the suspension weight-bridge crane coupling system is simplified to a model that the moving mass and the suspension weight moving on a simply supported beam and its motion differential equation is derived based on Lagrange equation. Runge-Kutta integration is used for numerical solution and some influence factors on system response are analyzed, such as the acceleration of the moving mass, the length of the wire and the mass ratio of the suspension weight. The results show without considering the swing of the suspension weight, vibration response of the beam will be underestimated by using the beam subjected to the moving mass model. When the mass sum of the moving mass and the suspension weight is a fixed value, the greater the mass ratio of the suspension weight,the greater the response of the beam that the acceleration of moving mass has great influence on the vibration of the beam. 
 

Acccording to the fact that the scale has a tremendous impact on the result of Morlet wavelet transform, a method based on energy spectrum of singular value is proposed to optimize Morlet wavelet scale and extract fault feature. Firstly, Shannon entropy is used to optimize the central frequency and bandwidth parameter of the Morlet wavelet. According to the situation that there is no clear minimum value in the calculation result of Shannon entropy, Morlet wavelet decomposition results with different parameters are compared to obtain the optimal wavelet parameter. Then, the effective scale ranges are chosen to do Morlet wavelet transform according to the relationship between practical frequency and wavelet scale parameter. Finally, the wavelet coefficients at each scale are decomposed into singular values and the energy spectrum of singular value is calculated. The optimal scale is obtained by choosing the maximum in energy spectrum, and then the fault feature can be extracted. The experimental results and analysis results of rolling bearing signals show that the proposed method overcomes the disadvantages of previous methods and has good effect in fault feature extraction when signal-to-noise ratio(SNR) is low.
 

The Hinged Rocker bearings are used on railway bridge at 20m ~ 32m, in recent years, some bearings appear hazards while using, mainly resulting bearing’s axial endplay or channeling which make parts of the bearing out of work under the transversal force , and leave security risk to the operate of the railway bridge, urgent needed to be reset. In this paper, numerical calculation and experimental study are done. By coupling vehicle-bridge vibration analysis, the maximum of transverse force of the bearing is 160kN, and by finite element analysis, bearing’s axial endplay need the transverse force to be 139kN, and by in-site testing, bearing’s axial reset need the transverse force to be 190kN~210kN，which explain the cause of the hazard occurs, also suggest that the possibility of bearing’s axial reset. According to the results of calculation and experiment, a simple high rigidity axial endplay automatic reset equipment is introduced to eradicate the hazards ,and the equipment can be installed at the time of operation of railway without adverse effect.
 

In order to analyze the effect of fastener stiffness and damping on the box-girder noise, a mixed FEM-BEM noise prediction model based on train-track-bridge coupling vibration theory and acoustical BEM theory was built and validated by field test. A 32 m simply-supported box-girder was selected as the case study, the effects of fastener stiffness and damping on the distribution of noise field, characteristics of noise spectra and wheel/rail interaction force were investigated. Results show that the mixed FEM-BEM model is a good predictor, the dominant frequency range of structure-borne noise is 40～80 Hz which mainly depends on the fastener stiffness; the sound pressure levels (SPLs) of the field points with a height of 1.2 m from the ground have an attenuation rate of 0.29 dB(Lin)/m and 0.067 dB(Lin)/m respectively in the distance of 10～40 m and 40～100 m from the nearest track centerline; the direction angle of structure-borne noise decreases significantly with the increase of the fastener stiffness; when the fastener stiffness varies from 10 MN/m to 100 MN/m, the average SPLs increase 12.5 dB(Lin) for the field points in the longitudinal section that has a distance of 30 m from the nearest track centerline, and the peak frequencies of structure-borne noise and wheel/rail interaction force vary from 30 Hz to 67 Hz simultaneously; the fastener damping has little effect on the directivity of the noise field; when the fastener damping ratio varies from 0.0625 to 0.5, the average SPLs decrease 5.0 dB(Lin) for the field points in the longitudinal section that has a distance of 30 m from the nearest track centerline, and the peak frequencies of the structure-borne noise and wheel/rail interaction force remain unchanged.
 

Section model wind tunnel test is currently the main technique to investigate the flutter performance of long-span bridges. But further study about applying the results to the aerodynamic optimization of the bridge main beam is still needed. Methods and results of selecting design wind parameters of the bridges in the mountainous valley are determined by using the example of one long-span steel truss girder suspension bridge. The flutter critical winds at different attack angles are obtained through the 1:48 proportion section model flutter test. Under the most unfavorable working condition, tests to investigate the effects that upper central stabilized plate, lower central stabilized plate and horizontal stabilized plate have on the flutter performance of the main beam were conducted. According to the test results, the optimal aerodynamic measure was chosen to have met the requirements of the bridge wind resistance in consideration of safety, economy and aesthetics. At last, the credibility of the results is confirmed by the 1:100 proportion full bridge aerodynamic elastic model test. That the flutter reduced wind speed of long-span steel truss suspension bridges stays approximately at 4 is concluded as a reference for the investigation of the flutter performance of similar steel truss girder suspension bridges.
 

It is still facing the long-term challenges to establish the longitudinal vibration and impact model of the train consisting of railway tankers considering fluid-structure interaction in this study field. In order to realize this goal, It designed a railway tank car model whose scaling ratio is 1:5. It studyed the longitudinal impact and vibration characteristics of liquid-solid coupling model for the railway tanker in various filling ratio and various quality of rice based on the method of random decrement technique (RDT) and Morlet Wavelet transform（WT）. Morlet WT is applied to analyze the free longitudinal responses of the railway tank car obtained by random decrement technique (RDT), which can identify resonance frequencies and damper ratio of different condition.