In order to understand the dynamic behaviors of deep reinforced concrete (RC) beams under impact loadings, falling-weight impact tests on two groups of simply-supported deep RC beams with different static behaviors were carried out and the effects of impact velocity and the second impact on the impact-resistant behavior of deep RC beams are investigated. By analyzing the crack initiation, propagation and the failure process of the specimens recorded using a high-speed video camera and comparing the crack patterns of specimens under different loadings, it is found that the crack initiation, propagation, the failure process and crack patterns are affected obviously by impact velocity and the major crack development under the second impact mainly follows the crack path induced by the first impact loading. The characteristics of time histories of impact force and mid-span displacement and impact force versus mid-span displacement curves are described in details and that the maximum impact force, the maximum mid-span deflection, the residual mid-span deflection change approximately linearly with impact velocity for specimens without serious shear failure is observed. Moreover, the specimens with better ductility have better impact-resistant behaviors. Finally, by analysis of the time histories of impact force, supported reaction force and inertia force, it is deduced that taking the maximum impact force or the maximum support force as the impact-resistant loading capacity is irrational.

Through the discussion on the anti-seismic test for telecommunications equipment, researched the anti-seismic test method in GR-63-CORE criteria of NEBS (Network Equipment-Building System). For the problems that the system bandwidth was not enough and nonlinear factors existed in a seismic test, designed a TVC (three-variable control) algorithm for servo control of the seismic simulating shaking table, and also proposed a correcting iteration algorithm in frequency domain for the drive signal correction of the shaking table. The research results show that the TVC algorithm can effectively expand the bandwidth of the test system and extend its dynamic response range; and the correcting iteration algorithm can effectively compensate the influences of the nonlinear factors in the test system by on-line correcting the drive signal iteratively. The seismic tests of NEBS GR-63-CORE show that with the control strategies of the TVC algorithm and the correcting iteration algorithm, the shaking table can achieve seismic waveform replication tests precisely.

The automatic deduction method to overall transfer equation and rapid simulation of launch dynamics of Multiple Launch Rocket Systems (MLRS) are the key to the dynamic design of MLRS. For a new type MLRS, the multibody system launch dynamics model and its topological graph are developed. According to sign conventions and transfer equation of elements, an automatic method to develop the overall transfer equations for the new type MLRS is developed. The modeling efficiency and programming level are improved. The visual simulation system for dynamics of MLRS is established, and the launch dynamics are simulated rapidly and validated by test. The theory base for dynamic design of a new MLRS is provided.

Due to the processing and manufacturing uncertainty the actual structure system often has a lot of uncertainty. How to accurately assess the dynamic behavior of the uncertain system, it not only has the practical significance, but also is a research focus on the structural theory in recent years. In this paper the dynamic behavior of the structure with uncertain parameters under external random excitation is investigated. The uncertain parameters of the structure are modeled by the random variable, and the random excitations are modeled by the stochastic process. The hybrid Polynomial Chaos and Pseudo Excitation Method (PC-PEM) are proposed to evaluate the random vibration response of the uncertain structure. Finally, the proposed method is applied to evaluate the random response of a 21 bars truss with uncertain parameters. The first two statistical moments are discussed, and the correctness and effectiveness of the proposed method are verified compare with the Monte Carlo Method. This work is of great significance to the random vibration analysis for the complex equipments and structures with the uncertain parameters.

Braking action of a brake disc is a local contacting problem, which brings influence to the modes and inherent frequencies of the system. The method of local discontinuous basis function can be used to estimate the modes of system accurately. In this paper, a brake disc, contacted by a brake boot or friction block, is simplified as a one-dimensional beam model with loop structure. The equation of motion is established. Firstly, the modes of the free vibration beam with no contact, defined as reference system, are calculated. Then the contact of the friction block is simplified as several linear springs. Considering the continuous conditions, the discontinuous modes are calculated and orthogonalized with the reference modes.,as the supplement of reference mode, used to calculate the system response. Compared with the finite difference method, Local discontinuous basis function method is more accurate than the traditional modal method.Analyses show that the local contact by the friction piece can restrain the symmetry of vibration of the brake plate, which leads to disappearance of sine or cosine modes. Based on the discontinuous mode analysis, vibration of the brake disk under action of external excitation is calculated. And the function of the nonlinear stiffness and friction, can make the vibration to be wave type.Further researches on structure unstable vibration mechanism of the brake noise can be carried out based on the above result.

The vibration caused by subway has a certain effect on multilayer frame structure and high-rise frame structure. Aimed at the vibration isolation issues of a proposed teaching building located in Guangzhou City, the environmental vibration of the proposed building site was measured. It shows that vertical vibration level of the proposed building site is beyond the limits of codes and higher than horizontal vibration level; In the dynamic response analysis of upper structure, the most unfavorable vibration acceleration time history that we had measured as consistent incentive to the substrate of structure was input. It shows that the vibration of 3.15Hz ~ 31.5Hz is amplified after transmitting to the structure, vertical vibration level of the structure increases layer by layer; The results show that we can effectively reduce the vertical vibration caused by subway by 23% and meet the limits of codes after using steel spring floating vibration isolation in the base of the building.

To study the response of submerged floating tunnel tether subjected to random ambient excitation, a non-linear random vibration equation of tether is established considering tether sag. Subsequently, the vibration response of tether is analyzed by means of stochastic equivalent linearization method. The results indicate that, the mid-span displacement and velocity root mean square response of tether subjected to zero-mean Gaussian white noise excitation tends to stable value after a certain period of time, while the cross-correlation function of mid-span displacement and velocity tends to zero; the mid-span displacement root mean square response of tether decreases as its damping ratio increases，whereas it increases as power spectral density of excitation increases; due to the existence of water damping force, the displacement and velocity root mean square response of tether decreases rapidly compared with tether in air.

In order to solve the reliability problem of structural damage equation, a damage detection method based on ridge estimation and L-curve is presented. First, a structural damage equation based on modal strain energy sensitivity is given out. Then, considering that measurement noise will cause the ill-posed equation problem, ridge estimation is utilized to solve the damage equation and L-curve is utilized to identify optimal ridge parameter. Finally, an improved ridge estimation method is proposed to enhance the identification precision. Simulation results demonstrate that the proposed ridge estimation and L-curve method can detect structural damage locations and extent with good accuracy, the quantification results of the proposed method are obviously better than those of the basic ridge estimation and L-curve method and the truncated singular value decomposition method.

Generalized Differential Quadrature Rule(GDQR)was applied to investigate the stability of a pipe conveying fluid on an elastic foundation. Based on the motion equations and boundary conditions of a pipe conveying fluid, the matrix eigenvalue equation consisted of the dynamic equations and boundary conditions was obtained after discreted by GDQR. After analyzing the corresponding eigenvalue equations,the results of critical velocity for divergence and flutter under different supporting conditions were calculated ,the effect of translational and rotational spring stiffness to critical instability velocity and stability region was discussed , meanwhile the influence of mass ratio ,reaction coefficient and shear modulus in two-parameter model to stability region were studied, some useful conclusions were obtained. The conclusion of the study could provide some useful suggestion for engineering.