Wind Tunnel Tests of Long Span Half - through Arch Bridge Section Model

Wind induced vibration is one of the main control factors in the Long span bridge structure design. The wind tunnel tests for measuring the static wind forces on the bridge girder and the section model wind tunnel dynamic testing for Caiyuanba Yangtze River Bridge in Chongqing are introduced in this paper. The wind tunnel testing for measuring static wind forces and vortex- induced vibration test on the arch are introduced taking account of the influence between two arches. The main contents and outcomes of testing are presented. It is indicated that the bridge girder has excellent wind stability and the arch mechanical characters are rather complicated. The drag force on the hind arch varied a lot because of the font arch interference on the wind flow. The drag force on the hind arch will be negative when two arches are close to each other. It increases with the space of two arches. The results of testing will give the data of buffeting and vortex - induced vibration and flutter analysis of the bridge.     

Time Domain Analysis on Buffeting of Jinma Bridge

Jinma bridge is a long span cooperative-system cable-stayed bridge with one tower cooperated with T frames on both sides.Owing to artistic form and lying in typhoonprone area,it is essential to process the buffeting analysis.In this paper,the turbulent wind velocity was first simulated with cosine wave superposition method as multi-correlated random processes;then,the time domain expressions for the buffeting and self-excited forces were given.On this basis,the buffeting analysis of Jinma Bridge was made.The results show that the anti-wind capacity of the cooperative-system cable-stayed bridge is ensured although the torsional resistibility of the main girders of this bridge is not good.     

Extracting a fetal electrocardiogram based on independent component analysis

Based on the basic generation model for the independent component analysis (ICA) and the fixed point FastICA algorithm using negentropy, three observed signals containing maternal electrocardiogram (MECG) and fetal electrocardiogram (FECG) components obtained from abdomen of a pregnant woman are successfully separated by using the FastICA algorithm with progressive orthogonalization, and the FECG is extracted. By invoking the wavelet de noising program in Matlab, the extracted FECG is decomposed to 8 levels with db2 wavelet to obtain the default soft threshold for de noising. The results show that the FastICA algorithm with progressive orthogonalization performed fast convergence. The three source components were extracted with only seven, three, and two iterations, respectively. The noise in the extracted FECG can be eliminated using wavelet de noising.     

Wind Vibration Characteristics of High-rise Building of RC Frame Structures

For high-rise building of RC Frame Structures, its security problems with wind load is more important, in this paper the mechanical model is established to simulate the atmospheric flow field around high-rise building, and the modal analysis is carried on for the structure. The simulation results show that velocity contour of wind field and pressure change contour describe the wind field characteristics. Wind velocity and pressure change near frontwall and backwall will affect obviously the vibration characteristics of high-rise building. Natural frequency and vibration mode can be obtained though modal analysis of high-rise building with wind load action, and necessary measures will be taken to avoid unnecessary losses due to resonance factors. And harmonic response is analyzed for high-rise building with load action to avoid resonance.     

Multi-objective dynamic optimization design of high-power wind turbine gearbox

A dynamic model of NGW helical planetary gear transmission for high-power wind turbine gearbox is established by considering these factors as errors of gears and time-varying mesh stiffness by using mass centralized method. Moreover, the random wind velocity is simulated as external seismic excitation making the results more conform to practical condition. And on this basis, this system is optimized for minimum gearbox volume and minimum component torsional acceleration with the restriction of reliability and strength restrain. The result indicates that the optimized parameters make gear transmission lightweight and the dynamic property improved so as to reduing vibration and noised.     

Wind Tunnel Test and Numerical Simulation of Wind Induced Loads on Complex Shaped High Rise Buildings

Taking a complex shaped high rise building as a case, the wind tunnel test with rigid model was carried out for wind load study. Meanwhile, with Fluent 6.1 software, the CFD numerical simulation had been performed with the RSM and the Non equilibrium Wall Functions. It was found that the results of the two methods were in good agreement. There were mainly positive pressures on the windward surface and negative pressures on the roof, the leeward surface and the side. Especially, negative pressure was higher in the leeward region at the building corner. And at the wind angle of 180°, the wind speed amplification effect was remarkable which was similar to those of canyons.     

Arch Axis Optimization of New Type Arch Bridge with Diagonal Web Cables Based on Geometric Nonlinear Mechanical Analysis

There are obvious geometric nonlinear mechanical characteristics in new type arch bridge with diagonal web cables. Meanwhile, the convergence of the existing arch axis iterative optimization method is not good. In order to solve new type arch bridge axis iteration convergence problem considering geometric nonlinear mechanical analysis, an arch axis iteration optimization method was proposed based on the iteration basis finite element model with two hinge arch model in main arch ring. A 600m span arch bridge with diagonal web cables was selected as an example to test the convergence performance and applicability of proposed method. The results showed that the bending moment of proposed method had better distribution along arch span, and it is about 35% smaller in maximum bending moment, 17% smaller in minimum bending moment and 23% smaller in bending strain energy compared to the results of linear iteration optimization method. Convergence analysis results demonstrated that proposed method had better iteration performance than the existing method. Meanwhile, different initial arch axis can converge to stable results.     

Simulation of Wind Loading for Large - span Bridge Structures

Wind speed time series obtained with numerical simulation methods are adopted in structural analysis of wind - induced vibration. In this paper, based on the natural wind properties and the correlativity of nodal wind speed time series, AR model is employed to simulate wind speed time series, and the AIC rule is used to fix the rank of the AR model. Statistical analysis results of numerical wind speed time series show that AR model is efficient in simulating nodal wind speed time series which has time and space correlativity, and that the simulation precision, simulation efficiency and calculation stability answer the needs of practical engineering.     

Influence on Turbulent Flow Calculation of Wind Flow Around TTU Building by Grid Size Δy in Near-Wall Region

In order to improve the accuracy of simulation in which k-ε EARSM turbulent model was employed, the influence of grids thickness Δy on the turbulent variables in flow field around building was researched. Coupled with real data of Texas Tech University experimental building, Δy as the main parameter was studied in the numerical wind tunnel simulation. Equation of k-ε EARSM and simplified equation of Δy were analyzed and deduced. Quasi-steady State Marching-on-in-time Approximation technology was employed to simulate the average flow in five working conditions, in which y is 0.001m, 0.005m, 0.01m, 0.05m, and 0.1m, respectively. And based on the results, the comparison of characteristic of flow around building, turbulent kinetic energy coefficient, fluctuating pressure coefficient along axis and mean pressure coefficient was conducted. The results indicate that very small Δy will make fluid with high Reynolds number penetrate into near-wall zone, and the calculation stability worsens; on the other side, very large Δy will lower simulated accuracy of main variable results in the turbulent region near the cornice with high Reynolds number. Accordingly, Δy near the wall ranging from 0.01m～0.05m meets the requirements for accuracy and stability, then the experiential formula of Δy upper limit is given.     

Numerical Simulation of 3D Atmospheric Flow Around a Bluff Body of CAARC Standard High Rise Building Model

Based on Reynolds Averaged Navier Stokes Equations(RANS)standard k ε model, realizable k ε model, RNG k ε model and SST k ε model, the 3D steady wind flow field around standard high building CAARC in atmospheric boundary layer was numerically simulated with software Fluent 6.3. And upon the comparison with those from wind tunnel test, it was found that numerical simulation was a feasible way to study the wind flow around high building and the distribution of wind pressure in the building’s surface. The four proposed models can reach the accuracy from the actual demand. Furthermore, it was also shown that, the numerical results were approximate to those from wind tunnel tests in the windward while between those from NPL and TJ 2 tests in the side and leeward. The pressure on the windward surface was positive with the maximum at 2/3 height and the minimum on the sides and the bottom. The pressures on the leeward surface and two sides were negative. There were little differences among the results of the four models.     

Analysis on the Cuplock Template Support System with Semi-Rigid Connettion

The Cuplock Template supports system joint initial rigidity and bowl buckle tightening torque was closely linked, with MATLAB applications for the two order and three order numerical fitting between them, found that three order fitting accuracy was higher than two order fitting results. Using ANSYS finite element software to establish the corresponding with the entity model, the changes in simulated nodes hinged, rigid and different initial stiffness condition for supporting system, and the simulation results were compared with the actual bearing capacity of the frame body stability. Find node is hinged and rigid connection simulation results state and actual frame difference. When the simulation results between node tightening torque of the 35N.m~50N.m and the actual time the frame carrying capacity is close, the node for the semi-rigid connection state. In order to show that the semi-rigid joint model can simulate accurately with the actual capacity of the Cuplock Template supports system.     

Turbulent Wind Velocity Spectrum Analysis Approach Based on Proper Orthogonal Decomposition

The emergence of large-span bridge and extreme weather attract much more attention of researchers on the bridge buffeting problem. One of the most important factors that affect bridge buffeting response is wind velocity spectrum. In the precious investigations, wind velocity of various frequency has impact on the bridge buffeting response. While Proper Orthogonal Decomposition(POD)method is proposed to decompose the wind velocity to solve the above problem and a cable-stayed bridge was used to investigate the contribution of effective model to bridge buffeting response. The result showed that not all frequency ranges of wind velocity spectrum contributed to the response which had relationship with both structural self-vibration mode and turbulence effective mode coefficient.     

CFD Simulation and Optimization of Internal Hydrodynamic Characteristics and Aerating Distribution in Membrane Bioreactor

The simulation of Eulerian multiphase flow model with two-phase (air & water) in membrane bioreactor were aimed at obtaining and comparing gas hold-up distribution, velocity field and membrane surface rate among the two reactor internal configuration of “alignment” and “alignment” diversion. Furthermore, the gas distribution mode was analyzed as well as optimized. The mini-model experiment was conducted to validate the simulation result. It is shown that: the bubbles track of internal field tended to flow to the membrane assembly center position, and then dispersed on the top of membrane modules in the two reactor configurations; the influence of diversion on gas holdup distribution was in apparent while notable on the velocity field distribution. The simulation results of an experimental model shrunk 100 times was proved to be consistent with the experimental results. Through an optimization simulation of gas distribution mode, the non-uniform gas distribution mode was proved that it can improve the range of gas distribution and the turbulence intensity.     

Improved AHP Assessment and Grey Relational Analysis Model for Optimizing Waterworks Sludge Treatment Process

The goal of AHP Grey Relational Analysis model is to solve problems during selecting the best waterworks sludge treatment process.And grey Relational Analysis is to confirm the compactness between the ideal process and candidate process.Moreover, weighting system was determined by the three mark matrix and consistency analysis of judgment matrix for traditional AHP was improved by the optimum transfer matrix.Base on these theories, AHP GRA model was established.A case study was addressed with the selection of waterworks sludge treatment process in Chongqing.It is found that this model is legitimate and credible.     

Strut and Tie Model Method of ReinforcedConcrete Beam Column Joint Core

“Macro model” in OPENSEES is an ideal and effective method for simulating RC beam column joint. Some disadvantages, however, exist in both the modified compression field theory (MCFT) and diagonal compression strut model, with which they are commonly used to obtain the shear stress strain relation of joint core. A new method by means of strut and tie model (STM), which reflected three mechanisms in joint well, was proposed to simulate the shear stress strain response of joint core. The deformation compatibility and equilibrium condition of the model were deduced thereafter. It was indicated that the result of STM method was in good agreement with that of test data. And it could simulate more accurately the shear stress strain response of joint core with a wide range of stirrup ratio.     

Predicting System of Hot Metal Silicon Content in Blast Furnace

Hot metal silicon content in blast furnace is a main parameter by which product quality is measured and energy utilization ratio of blast furnace is reflected.The precise predicted results of hot metal silicon content can be used to direct batch operation and smelting operation of blast furnace.And the purpose of reducing hot metal silicon content is realized.The equations of thermodynamics and dynamics were deduced based on the reduction mechanism of silicon. And the predicting model of hot metal silicon content was obtained.With this model and the calculation methods of blast furnace's materiel and energy balance,the predicting system of hot metal silicon content was programmed.Real materiel conditions and operation parameters wre inputted into the system.And predicted values of hot metal silicon content were gained.Compared with measured values the deviations of predicted values were small.So it is testified that this predicting system has credibility in practice.     

Error Analysis between Relative Motion Solving Method and Absolute Displacement Direct Solving Method

Under multi-support earthquake excitation, the damping is proportional to the relative velocity in relative motion method, While the damping is proportional to the absolute velocity in method of direct solving absolute displacement, and the damping assuming difference may cause the calculation errors on structural responses. The structural response errors of the dynamic component of power spectral density between the two solving methods are derived by random vibration theoretical analysis in Rayleigh damping model, which include damping ratio and the ratio between excitation frequency and fundamental frequency of the structures. Based on probability theory, the variation errors of dynamic component response between the two solving methods are also derived by theoretical analysis, and some numerical examples are provided to verify the error analysis. At last, it is pointed out that the calculation errors between the two solving methods decrease with damping ratio, and it is negligible when the damping ratio of structure is less than 5%.     

Construction Parameters and Process Simulation Method of Suspen domes

Mechanical behavior of Suspen domes during construction is different with that in service and even more adverse because of cables introduced in the structures. By studying the actual suspen dome projects, the key construction parameters for them were extracted and tensioning mechanism of hoop cables was studied. Then according to the tensioning mechanism and the key construction parameters, a numerical model and an algorithm for the whole process of tensioning were proposed. Moreover, a case study was addressed to approve the effectiveness.     

Spatial Calculation Methods of Three Main Trusses Continuous Plate truss Composite Bridge

According to the structural features of three main trusses continuous plate truss composite bridge, two composite beam methods are presented by constructing the displacement mode of composite beam elements and deriving the stiffness matrix of composite beam elements. The characteristic of composite beam method one is that the bridge slab is taken as the top flange of the chord of main truss and combined with the chord of main truss to form a steel concrete composite beam; the characteristic of composite beam method two is that the bridge slab is taken as the top flange of longitudinal and traverse beam and form a steel concrete composite beam with longitudinal and traverse beams. And as for the conventional plate beam composite method, the slab is characterized by forming bridge slab system with continuous isotropic sheets and longitudinal and traverse beams to bear load. Also, the comparison between theoretical results and experimental ones verifies the effectiveness of the above three methods.     

Wind tunnel tests and numerical simulation on arches’static wind loads of half through arch bridge

Long span half through arch bridges have the flexible space structure. Wind loads on the arches are usually the key factor to the whole bridge. Taking an example of the Chongqing Caiyuanba Yangzi River Bridge in P. R. China, wind tunnel tests of single arch and double arches section models were conducted. The results of a single arch in the smooth flow show that arch drag variability is small, and the lift and moment variability are significantly large. The results of double arches testing show that the static forces of the windward arch are similar to the single arch. The three force coefficients of leeward arches vary with the space width ratio and the angle between the two arches. Static forces testing was simulated by the CFD software FLUENT. The static forces from the testing and the simulation were compared. The results show that the values match quite well with testing, and the drag forces mainly varied with the space width ratio.