Structural dynamic responses analysis applying differential quadrature method

Unconditionally stable higher-order accurate time step integration algorithms based on the differential quadrature method (DQM) for second-order initial value problems were applied and the quadrature rules of DQM, computing of the weighting coefficients and choices of sampling grid points were discussed. Some numerical examples dealing with the heat transfer problem, the second-order differential equation of imposed vibration of linear single-degree-of-freedom systems and double-degree-of-freedom systems, the nonlinear move differential equation and a beam forced by a changing load were computed, respectively. The results indicated that the algorithm can produce highly accurate solutions with minimal time consumption, and that the system total energy can remain conservative in the numerical computation.

Distributed collaborative extremum response surface method for mechanical dynamic assembly reliability analysis

To make the dynamic assembly reliability analysis more effective for complex machinery of multi-object multi-discipline(MOMD),distributed collaborative extremum response surface method(DCERSM)was proposed based on extremum response surface method(ERSM).Firstly,the basic theories of the ERSM and DCERSM were investigated,and the strengths of DCERSM were proved theoretically.Secondly,the mathematical model of the DCERSM was established based upon extremum response surface function(ERSF).Finally,this model was applied to the reliability analysis of blade-tip radial running clearance(BTRRC)of an aeroengine high pressure turbine(HPT)to verify its advantages.The results show that the DCERSM can not only reshape the possibility of the reliability analysis for the complex turbo machinery,but also greatly improve the computational speed,save the computational time and improve the computational efficiency while keeping the accuracy.Thus,the DCERSM is verified to be feasible and effective in the dynamic assembly reliability(DAR)analysis of complex machinery.Moreover,this method offers an useful insight for designing and optimizing the dynamic reliability of complex machinery.

Analysis of interlaminar stress and nonlinear dynamic response for composite laminated plates with interfacial damage

By considering the effect of interfacial damage and using the variation principle, three-dimensional nonlinear dynamic governing equations of the laminated plates with interfacial damage are derived based on the general sixdegrees-of-freedom plate theory towards the accurate stress analysis. The solutions of interlaminar stress and nonlinear dynamic response for a simply supported laminated plate with interfacial damage are obtained by using the finite difference method, and the results are validated by comparison with the solution of nonlinear finite element method. In numerical calculations, the effects of interfacial damage on the stress in the interface and the nonlinear dynamic response of laminated plates are discussed.

Parametrical analysis of the railways dynamic response at high speed moving loads

The paper introduces some findings about a sensitivity analysis conducted on every geometrical and mechanical parameters which characterize the use of a railway superstructure at the high velocity. This analysis was carried out by implementing a forecast model that is derived from the simplified Gazetas and Dobry one. This model turns out to be particularly appropriate in the explication of problems connected to high velocity, since it evaluates both inertial and viscous effects activated by the moving load speed. The model implementation requires the transfer function determination that represents the action occurred by the bed surfaces on the railway and it therefore contains information concerning the geometrical and the mechanical characteristics of the embankment, of the ballast and of the sub-ballast. The transfer function H has been evaluated with the finite elements method and particularly, by resorting the ANSYS code with a harmonic structural analysis in the frequencies field. The authors, from the critic examination of the system＇s dynamics response in its entirety, glean a series of observations both of a general and a specific character, finally attaining a propose of a design modification of the standard railway superstructure at the high velocity of train operation adopted today especially in Italy.

Dynamic Response Analysis of Risers Subjected to Combined Wave and Current Loading

A dynamic response analysis in the frequency domain is presented for risers subjected to combined wave and current loading. Considering the effects of current, a modified wave spectrum is adopted to compute the linearized drag force. An additional drag force convolution term is added to the linearized drag force spectrum, therefore the error is reduced which arises from the truncation of higher order terms in the drag force auto-correlation function. An expression of linearized drag force spectrum is given taking the relative velocity into account. It is found that the additional term is a fold convolution integral. In this paper dynamic responses of risers are investigated, while the influence of floater motion on risers is considered. The results demonstrate that the accuracy of the present method reaches the degree required in time domain analysis.

Dynamic Response Analysis of Interaction System of R.C. Gravity Single-Leg Platform

In this paper, the responses of the interaction system of R.C. gravity single-leg platform to seismic excitation are mainly analysed. A set of nonlinear equations for the interaction system are established by using the wave, one is the soil-structure interaction and the other is the fluid-structure interaction. The seismic response of the interaction system is analysed for the influence of the asymmetric structure, fluid action, etc. with the input of seismic SH waves in any direction. The numerical results are given for a simple example.

Perturbation Analysis of the Attached Water Mass Effect on Offshore Platform Dynamic Response

Theoretically speaking, it is impossible to make the differential equation of motion uncoupled for the natural modes of a system in consideration of the attached water. The hydro-elastic structure is equal to the non-proportional damping system. In this paper a perturbation analysis method is put forward. The structure motion equation is strictly solved mathematically, and the non-proportional damping problem is transformed into a series of proportional damping ones in the superposition form. The paper also presents the calculation formula of the dynamic response of the structure being subjected to harmonic and arbitrary load. The convergence of the proposed method is also studied in this paper, and the corresponding convergence conditions are given. Finally, the proposed method is used to analyze the displacement response of a real offshore platform. The calculation results show that this method has the characteristics of high accuracy and fast convergence.

Linear analysis of the dynamic response of a riser subject to internal solitary waves

The flow field induced by internal solitary waves(ISWs)is peculiar wherein water motion occurs in the whole water depth,and the strong shear near the pycnocline can be generated due to the opposite flow direction between the upper and lower layers,which is a potential threat to marine risers.In this paper,the flow field of ISWs is obtained with the Korteweg-de Vries(Kd V)equation for a two-layer fluid system.Then,a linear analysis is performed for the dynamic response of a riser with its two ends simply supported under the action of ISWs.The explicit expressions of the deflection and the moment of the riser are deduced based on the modal superposition method.The applicable conditions of the theoretical expressions are discussed.Through comparisons with the finite element simulations for nonlinear dynamic responses,it is proved that the theoretical expressions can roughly reveal the nonlinear dynamic response of risers under ISWs when the approximation for the linear analysis is relaxed to some extent.

Dynamic response analysis of liquefiable ground due to sinusoidal waves of different frequencies of shield construction

Vibration induced by shield construction can lead to liquefaction of saturated sand.Based on FLAC3D software,a numerical model of tunnel excavation is established and sinusoidal velocity loads with different frequencies are applied to the excavation face.The pattern of the excess pore pressure ratio with frequency,as well as the dynamic response of soil mass under different frequency loads before excavation,is analyzed.When the velocity sinusoidal wave acts on the excavation surface of the shield tunnel with a single sand layer,soil liquefaction occurs.However,the ranges and locations of soil liquefaction are different at different frequencies,which proves that the vibration frequency influences the liquefaction location of the stratum.For sand-clay composite strata with liquefiable layers,the influence of frequency on the liquefaction range is different from that of a single stratum.In the frequency range of 5-30 Hz,the liquefaction area and surface subsidence decrease with an increase in vibration frequency.The research results in this study can be used as a reference in engineering practice for tunneling liquefiable strata with a shield tunneling machine.

Dynamics Response and Non⁃linear Characteristics Analysis of Complex Planar 2⁃DOF Mechanism with Revolute Clearances

There are clearances in mechanism because of manufacture and assembly error,which reduces operation life and working accuracy of mechanism and has a great impact on dynamical responses.At the moment,research in this area mainly focuses on single degree⁃of⁃freedom mechanism considering one clearance,while research of multi⁃DOF mechanism considering multi⁃clearance is less.With the purpose of studying the dynamical characteristics of complex multi⁃DOF mechanism with multi⁃clearances,a dynamic model was developed.The dynamic responses of 2⁃DOF mechanism with two clearances under different positions,values,and numbers of clearance were analyzed.The displacement,velocity,acceleration,collision force,and the axis trajectory at clearance were then given.In addition,there is a limited amount of literature on chaotic phenomena,which mainly focuses on the chaotic phenomena of end⁃effector of mechanism.But in this paper,the non⁃linear characteristics were analyzed by chaotic phenomenon of clearance joint,then chaotic phenomenon was identified by Poincarémappings and phase diagrams.Bifurcation diagrams were given.The results will offer a reliable technical support for the study of dynamical responses of planar mechanisms and the analysis of chaotic phenomena.

ANOMALOUS BEHAVIOR REVISITED:DYNAMIC RESPONSE OF ELASTIC-PLASTIC STRUCTURES

Based on the minimum principle of acceleration in the elastic-plastic continua under finite def ormation, the dynamic response of an elastic-perfectly plastic pin-ended beam subjected to rectangular impulse loading is studied with the help of a numerical approach. The calculated results once again show the anomalous behavior of the beam during its response process, which was previously found in [1]. By carefully analyzing the instantaneous distribution of the bending moment, the membrane force, the curvature and displacement during the response process, it is concluded that the interactive effect between the geometry and materials nonlinearities of the structure is the key reason for leading to the anomalous behavior. This will be helpful for clarifying some misunderstandings in explaining the problem before.

The dynamical and thermodynamical analysis of the oceanic response to storm

In this paper, the discussion is made on the problem of the oceanic response caused by air-sea interaction under storm. First, the perturbation differential equations for the problem are given, and the interaction functions are supposed to be the solving conditions. Next, the nonlinear diffusion equations of the problem are solved by using the method of the given variable transforms and the specific variable power series. Finally, the response disturbances to the circular intense storm is calculated so as to discribe quantitatively the evolution processes of the oceanic response.

Comparison between Different Shapes of Structure by Response Spectrum Method of Dynamic Analysis

Several procedures for non-linear static and dynamic analysis of structures have been developed in recent years. In this paper, the response spectrum analysis is performed on two different shapes i.e. regular and irregular shape of structure by using STAAD PRO. And the comparison results are studied and compared accounting for the earthquake characteristics and the structure dynamic characteristics. As the results show that the earthquake response peak values and the main response frequencies are very close and comparable. It can be referred to by the engineering applications.

Influence of Various Earth-Retaining Walls on the Dynamic Response Comparison Based on 3D Modeling

The present work aims to assess earthquake-induced earth-retaining(ER)wall displacement.This study is on the dynamics analysis of various earth-retaining wall designs in hollow precast concrete panels,reinforcement concrete facing panels,and gravity-type earth-retaining walls.The finite element(FE)simulations utilized a 3D plane strain condition to model full-scale ER walls and numerous nonlinear dynamics analyses.The seismic performance of differentmodels,which includes reinforcement concrete panels and gravity-type and hollowprecast concrete ER walls,was simulated and examined using the FE approach.It also displays comparative studies such as stress distribution,deflection of the wall,acceleration across the wall height,lateral wall displacement,lateral wall pressure,and backfill plastic strain.Three components of the created ER walls were found throughout this research procedure.One is a granular reinforcement backfill,while the other is a wall-facing panel and base foundation.The dynamic response effects of varied earth-retaining walls have also been studied.It was discovered that the facing panel of the model significantly impacts the earthquake-induced displacement of ER walls.The proposed analytical model’s validity has been evaluated and compared with the reinforcement concrete facing panels,gravity-type ER wall,scientifically available data,and American Association of State Highway and Transportation Officials(AASHTO)guidelines results based on FE simulation.The results of the observations indicate that the hollow prefabricated concrete ER wall is the most feasible option due to its lower displacement and high-stress distribution compared to the two types.The methodology and results of this study establish standards for future analogous investigations and professionals,particularly in light of the increasing computational capabilities of desktop computers.

Dynamic Response Analysis of A 5 MW NREL Wind Turbine Blade under Flap-Wise and Edge-Wise Vibrations

A wind turbine is subjected to a regime of varying loads.For example,each rotor revolution causes a complete gravity stress reversal in the low-speed shaft,and there are varying stresses from the out-of-plane loading cycle due to fluctuating wind load.Consequently,wind turbine blade design is governed by fatigue rather than ultimate load considerations.Previous studies have adopted many different beam theories,using different techniques and codes,to model the National Renewable Energy Laboratory(NREL)5MWoffshore wind turbine blade.There are differences,from study to study,in the free vibration results and the dynamic response.The contribution of this study is to apply the code written by the authors to the different beam theories used with the aim of comparing the different beam theories presented in the literature and that developed by the authors.This paper reports the investigation of the effects of deformation parameters on the dynamic characteristics of the NREL 5 MW offshore wind turbine blades predicted by the different beam theories.The investigation of free vibrations is a fundamental step in the analysis of structural dynamics,and this study compares different computational structural methods and investigates their effect on the predicted dynamic response.The modal characteristics of every model examined have been combined with strip theory to determine the dynamic response of the blade.

Distributed Collaborative Response Surface Method for Mechanical Dynamic Assembly Reliability Design

Because of the randomness of many impact factors influencing the dynamic assembly relationship of complex machinery, the reliability analysis of dynamic assembly relationship needs to be accomplished considering the randomness from a probabilistic perspective. To improve the accuracy and efficiency of dynamic assembly relationship reliability analysis, the mechanical dynamic assembly reliability（MDAR） theory and a distributed collaborative response surface method（DCRSM） are proposed. The mathematic model of DCRSM is established based on the quadratic response surface function, and verified by the assembly relationship reliability analysis of aeroengine high pressure turbine（HPT） blade-tip radial running clearance（BTRRC）. Through the comparison of the DCRSM, traditional response surface method（RSM） and Monte Carlo Method（MCM）, the results show that the DCRSM is not able to accomplish the computational task which is impossible for the other methods when the number of simulation is more than 100 000 times, but also the computational precision for the DCRSM is basically consistent with the MCM and improved by 0.40-4.63% to the RSM, furthermore, the computational efficiency of DCRSM is up to about 188 times of the MCM and 55 times of the RSM under 10000 times simulations. The DCRSM is demonstrated to be a feasible and effective approach for markedly improving the computational efficiency and accuracy of MDAR analysis. Thus, the proposed research provides the promising theory and method for the MDAR design and optimization, and opens a novel research direction of probabilistic analysis for developing the high-performance and high-reliability of aeroengine.

Seismic response of continuous span bridges through fiber-based finite element analysis

It is widely recognized that nonlinear time-history analysis constitutes the most accurate way to simulate the response of structures subjected to strong levels of seismic excitation. This analytical method is based on sound underlying principles and has the capability to reproduce the intrinsic inelastic dynamic behavior of structures. Nonetheless, comparisons with experimental results from large-scale testing of structures are still needed, in order to ensure adequate levels of confidence in this numerical methodology. The fiber modelling approach employed in the current endeavor inherently accounts for geometric nonlinearities and material inelasticity, without a need for calibration of plastic hinges mechanisms, typical in concentrated plasticity models. The resulting combination of analysis accuracy and modelling simplicity, allows thus to overcome the perhaps not fully justifiable sense of complexity associated to nonlinear dynamic analysis. The fiber-based modelling approach is employed in the framework of a finite element program downloaded from the Intemet for seismic response analysis of framed structures. The reliability and accuracy of the program are demonstrated by numerically reproducing pseudo-dynamic tests on a four span continuous deck concrete bridge. Modelling assumptions are discussed, together with their implications on numerical results of the nonlinear time-history analyses, which were found to be in good agreement with experimental results.

Shaking table test and dynamic response prediction on an earthquake-damaged RC building

This paper presents the results from shaking table tests of a one-tenth-scale reinforced concrete (RC) building model.The test model is a protype of a building that was seriously damaged during the 1985 Mexico earthquake.The input ground excitation used during the test was from the records obtained near the site of the prototype building during the 1985 and 1995 Mexico earthquakes.The tests showed that the damage pattern of the test model agreed well with that of the prototype building.Analytical prediction of earthquake response has been conducted for the prototype building using a sophisticated 3-D frame model.The input motion used for the dynamic analysis was the shaking table test measurements with similarity transformation.The comparison of the analytical results and the shaking table test results indicates that the response of the RC building to minor and the moderate earthquakes can be predicated well.However,there is difference between the predication and the actual response to the major earthquake.

Assessing the seismic behavior of steel moment frames equipped by elliptical brace through incremental dynamic analysis(IDA)

Incremental dynamic analysis and nonlinear static pushover analysis are carried out on a performance-based design to determine the seismic demands and capacities of an elliptic braced moment resisting frame(ELBRF).The objective is to assess ductility,overstrength and response modification factors in a modern steel-braced structural system based on incremental dynamic analysis.This integrated system is connected to a beam and column with an appropriate length while providing enough architectural space to allow for an opening without having the common problems associated with architectural spaces in braced systems.Several different classes of buildings are considered on soil type II.Linear dynamic analysis,nonlinear static pushover analysis and incremental nonlinear dynamic analysis related to 12 records from past earthquakes are carried out using OpenSees software.The factors of ductility,overstrength and response modification are calculated for this system.The values of 9.5 and 6.5 are found and suggested only for the response modification factor for ELBRF systems in allowable stress and ultimate limit state methods,respectively.The fragility curves are plotted for the first time for this type of bracing,which contributes to the assessment of building seismic damage.