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Different from the bridge with a single deck, the aerodynamic interference phenomenon caused by the two neighboring decks makes the aerodynamic performance of the parallel bridge with twin-decks much more complicated. Tanggu Bridge over Hai River in Tianjin, a parallel bridge with twin-decks, was taken as an engineering background. The present paper focuses on the vortex--induced oscillation (VIO) study of Tanggu Bridge which involves the amplitude analysis and the selection of vibration-reducing measure. The results firstly show that the high-order VIO can be successfully simulated via the full bridge aeroelastic model test and the Strouhal numbers of each VIO remain the same. Secondly, the high-order VIO can be estimated by the first--order VIO test, but the lock-in zone of wind speed may be larger than that of the test results. Besides, the maximal amplitudes of the estimation are smaller than those of the test results, the reasons of which are also analyzed briefly in this paper. Thirdly, the multi -- orifice plate has a good vibration -- reducing effect, which is related directly to the perforated ratio and its location [ABSTRACT FROM AUTHOR]

For the problem that the existing methods are difficult to identify main noise sources of the ship efficiently, a transmissibility matrix method (TMM) is introduced. The main problems of TMM facing in the practical application were analyzed, and the methods used to solve those problems were also proposed. In order to investigate the method which can solve cross-coupling of vibration sources, a new vibro-acoustic transfer path model for analysis based on TMM was established. The displacement response difference of isolator at both ends was considered as the equivalent vibration source, which avoided cross coupling of vibration sources efficiently. By Combining simulation analysis and the test of ship vibration and acoustic radiation in the water, the feasibility and correctness of the new model which is used to identify noise sources and study the noise contribution are validated. The results indicate that the new model can effectively identify and quantify noise source of ship which maintains the efficiency and also improves the accuracy. Since resilient isolators are extensively used in modern ship, which provide a precondition for widely applying the proposed method. Therefore the new method established in this paper has broad prospect of engineering application. [ABSTRACT FROM AUTHOR]

Magneto-rheological damper model suitable for helicopter air resonance and momentum theory model of hover condition involving momentum theory were built in this paper. The equations of the two models with the dynamic equations of helicopter rotor/body coupling were solved by Simulink time domain simulation method to obtain the helicopter dynamic stability influenced by Magneto-rheological damper and compared the blade flapping and lagging impacted by Magneto-rheological dampers under different voltages. It could be conclude that under a certain voltage, Magneto-rheological damper was not influenced by duel-frequent excitation, and was good at restraining the helicopter air resonance. [ABSTRACT FROM AUTHOR]

A mathematical model of Active Magnetic Bearing (AMB)-flexible rotor system is built in the paper. Supporting characteristic of AMB, unbalanced stationary responses of the system under control with different parameters and the influences of control parameter variation on system stability in rotating state were analyzed, and variable parameter control strategy based on rotation speed was put forward. The experimental setup for 5 DOF active magnetic bearing-rotor systems was established. The signal of the rotation speed was introduced into the digital controller, different control parameters were adopted in different rotation speed section, and dynamic characteristics of the system with variable parameter control strategy were investigated. Theoretical analysis and experimental results show that the variable parameter control strategy can meet requirements of low-frequency and high-frequency dynamic characteristics of the system synchronously, thus reducing unbalance vibration of the rotor effectively, and making for stably passing the critical speed of the rotor system. [ABSTRACT FROM AUTHOR]

As for the incremental learning of the unsupervised manifold learning algorithms the paper provides an incremental local tangent space alignment (LTSA) algorithm based on selecting landmark points for the clustering of incremental points. Firstly, the least angle regression (LARS) algorithm was used to select landmark points from original training samples, and then using those selected points and new samples the global coordinate matrix for all samples could be constructed. The lower-dimensional embedding coordinate of the incremental samples was estimated according to the global coordinate matrix and lower-dimensional embedding coordinate of the given training points. Then the lower-dimensional embedding coordinate of all samples was iteratively updated based on the eigenvalues of the global coordinate matrix. Experiments with the proposed method were carried out in four different cases of the vibration signal samples of rolling bearing. Results demonstrate the incremental LTSA algorithm based on selecting landmark points can preserve the class separability measure of the samples in different cases for rolling bearing. [ABSTRACT FROM AUTHOR]

Floating ring bearings (FRBs) are widely used in high speed rotating machines. In this paper, the carrying capacity of outer oil film, which can represent the total capacity of FRBs, in floating-ring bearing was analyzed only because the bearing capacity of inner oil film is larger than that of the outer one. Based on the rotordynamic DyRoBes software and finite difference method, the pressure of outer oil film in relatively heavy load micro gas turbogenerator was computed and the results were analysed and compared. Because of the structural characteristics of FRBs, the relationship of stiffness and damping of inner and outer films is equivalent to the series of spring and damper, thus the total stiffness and damping of FRB could be calculated under different rotation speeds. The important parameters, such as eccentricity ratio, static balance position, which give the influences on the oil film characteristics and rotor dynamic behavior were also studied. At last, the stability of oil film was determined using Routh-Hurwitz criterion. [ABSTRACT FROM AUTHOR]

The pure mass model method (PMM) which can be utilized to calculate the earthquake responses quickly for high-rise isolated structures is proposed in the paper. Firstly, the simplified single mass model, its transformation relationship with original structure and its parameter selection were determined according to equivalent criteria for base shear force and energy. And then, envelop responses of simplified model were calculated by introducing energy balance method. The method and model transformation relationship were used to predict the seismic response envelop values of every layer of the original structure. The prediction formula for acceleration, deformation and storey shear force of superstructure and isolation layer were given too. The effectiveness and accuracy of pure mass model method were verified by using a 22 stories high-rise isolated structure as an engineering example. Results show that computational results of simplified method and multi-mass model time history analysis method are comparable. The calculation amounts of the method proposed is less, and parameter selection is clear and convenient with high precision analysis. [ABSTRACT FROM AUTHOR]

In this paper, a decentralized vibration control algorithm is proposed for large-scale engineering structures utilizing the instantaneous optimal control scheme. Based on finite element model, a large-scale structure is divided into small size sub-structures. Interconnection forces between adjacent substructures are considered as "additional unknown disturbances" to the substructures. A computational algorithm based on sequential application of Kalman estimator for the state vector and least-square estimation for the "additional unknown disturbances" in each substructure, respectively is developed. The optimal control forces are determined by the instantaneous optimal control scheme. The proposed decentralized vibration control algorithm is applied to the ASCE 20-story control benchmark building under earthquake excitation and compared with the conventional centralized vibration control approach. It is demonstrated that the proposed decentralized vibration control algorithm provides satisfactory control performances. Thus, the proposed decentralized control algorithm is suitable for the vibration control of large-scale engineering structures. [ABSTRACT FROM AUTHOR]

The environmental vibration induced by moving trains is getting more concerned. In this paper, a field experiment was carried out at the Beijing-Guangzhou railway to study the train-induced vibrations of nearby buildings. The train speeds in the experiment were 40∼115 km/h for passenger trains and 26∼57 km/h for freight trains. The results show that the vibration of the building floors, in general trend, attenuates with distance to the track and get bigger with the increase of train speed; the vibration induced by freight train is 5∼15 dB bigger than that by passenger trains. For a six-story building, the vibration of floors becomes greater with the height, the vertical vibration of the sixth floor is 2∼6 dB higher than the ground floor and the lateral vibration 5∼10 dB higher. The vibration at floor center is larger than that at floor corners and staircase. The vibration of outside ground surface is greater than that of inside building, the difference being 2∼10 dB and getting smaller with the increase of vibration levels. The vibration of buildings near the track is serious, and some exceeds the allowance given in relevant codes, to which attention should be paid. [ABSTRACT FROM AUTHOR]

Multi steps method for damage identification is valid approach for complex structure at present. In the first instance, the structure is partitioned to some regions, and the most possible region for damage is confirmed. Finally, damage location and extending are identified in the search regions reduced. Based on the concepts of the dynamical indexes of frequency and COMAC, the similar region is partitioned by using fuzzy clustering method, and the damage is classified using support vector machine. It is demonstrated that the method presented in this paper can assess damage correctly in the case of test data polluted by measurement noises. [ABSTRACT FROM AUTHOR]