Harmonic Dynamic Loading Research Articles

Harmonic dynamic loading response of reinforced concrete column

A reinforced concrete column is classified as compression structural element mostly analyzed and designed due to the applied combinations of dead and live loading with other considered loadings. Industries of considerable or relatively great size, production and electrical utilities are very concerned about the presence of dynamic loads in their electrical power systems. This behavior provides current with different components that are multiples of the fundamental frequency of the system which are called harmonics. Reinforced concrete elements such as column must be checked for the strength capacity and the response due to applied harmonic loading after completed the static analysis and design. In present article evaluations of reinforced concrete columns under the effects of dynamic harmonic loadings are studied. The main parameters are the reinforcement ratio and harmonic ranged loadings. Finite elements approach was adopted to analyze the columns by ANSYS software and all models are simulated in three dimensions. The analysis results indicated that the square cross sections with that rectangular of the same cross sectional area are closed in performance against static and dynamic loadings.

A large-scale test of reinforced soil railway embankment with soilbag facing under dynamic loading

Geosynthetic reinforced soil retaining walls can be employed as railway embankments to carry large static and dynamic train loads, but very few studies can be found in the literature that investigate their dynamic behavior under simulated wheel loading. A large-scale dynamic test on a reinforced soil railway embankment was therefore carried out. The model embankment was 1.65 meter high and designed to have a soilbag facing. It was reinforced with HDPE geogrid layers at a vertical spacing of 0.3 m and a length of 2 m. The dynamic test consisted of 1.2 million cycles of harmonic dynamic loading with three different load levels and four different exciting frequencies. Before the dynamic loading test, a static test was also carried out to understand the general behavior of the embankment behavior. The study indicated the importance of loading frequency on the dynamic response of reinforced soil railway embankment. It also showed that toe resistance played a significant role in the dynamic behavior of the embankment. Some limitations of the test were also discussed.

Nonlinearity-induced time-varying harmonic dynamic axle load and its impact on dynamic stability of car–trailer combinations

ABSTRACTA nonlinearity-induced time-varying harmonic dynamic axle load is found in the road test of a car–trailer combination. To understand its influence on system dynamic stability, a corresponding linear single-track model (STM) is proposed. System dynamic stability is described and sensitivity analysis for the system parameters is achieved. The contribution of the harmonic force is quantified by a derived effective axle load. Because the harmonic effect might be time varying in practice, a time–frequency analysis-based parameter identification method is introduced. Experimental study shows that a time-varying harmonic effect really exists. A yaw-rate-based simulation method is designed to simulate this behaviour. The sensitivity analysis of the influence of the harmonic amplitude or phase on dynamic stability is performed with a simulation study. With appropriate modification of the harmonic amplitude and phase shift applied in selected time windows, the time-varying system characteristics in the road test can be simulated very well.

Comparison between experimental and analytical results for seesaw energy dissipation systems using fluid viscous dampers

This paper presents results of experimental and numerical investigations of a seesaw energy dissipation system (SEDS) using fluid viscous dampers (FVDs). To confirm the characteristics of the FVDs used in the tests, harmonic dynamic loading tests were conducted in advance of the free vibration tests and the shaking table tests. Shaking table tests were conducted to demonstrate the damping capacity of the SEDS under random excitations such as seismic waves, and the results showed SEDSs have sufficient damping capacity for reducing the seismic response of frames. Free vibration tests were conducted to confirm the reliability of simplified analysis. Time history response analyses were also conducted and the results are in close agreement with shaking table test results.

Numerical Investigations on the Influence of Soil Structure Interaction in the Dynamic Response of SDOF System

A single concrete pile embedded in various types of soil subjected to simple harmonic dynamic load is numerically analysed and studied. The soil type, the diameter of pile, the pile head projection above the ground level and the mass at pile head are varied and analysed. The influence of soil structure interaction on the structural behaviour of pile is investigated. The finite element software specialized in soil structure interaction analysis; PLAXIS-3D is used for the present study. Two different types of dimensionless design curves are plotted and studied, The frequency ratio Vs the stiffness ratio curves for different slenderness ratio and the frequency ratio Vs the stiffness ratio curves for different mass ratio.

Analysis on Shear Lag Effect of Box Girder Subject to Dynamic Load

Shear lag effect of box girders under static, transient dynamic load and harmonic dynamic load has been studied, respectively, through finite element method. Shear lag effects under different load conditions were compared and dynamic loading influence on shear lag was analyzed. The results show that the dynamic load has great influence on shear lag of thin box girder that can not be neglected. During the research, the eyesight was transfer from the conventional static load to the dynamic load to study the shear lag problem of box girder. The research conclusions will be useful for the design and construction of bridges and will enrich the design theory of box girder.

Dynamic BE analysis of 3-D cracks in transversely isotropic solids

A boundary element approach for the analysis of three-dimensional crack problems in transversely isotropic solids under time harmonic dynamic loading conditions is presented in this paper. For the first time a single region approach based on the tractions integral representation for three-dimensional anisotropic solids under dynamic loads is presented. Hypersingular and strongly singular kernels appearing in the formulation are regularized prior to any discretization. Two different crack geometries under time harmonic impinging waves are studied. Stress intensity factors are computed from the crack opening displacements at quarter-point quadratic elements. To the authors’ knowledge, no previous results for elliptical cracks in transversely isotropic solids under dynamic loading conditions exist in the literature. The results obtained in this paper for situations where previous solutions exist, show a good agreement with those other results. The number of elements required for the analysis is rather small.

Evolution of Natural Frequencies in Tensegrity Systems: A Case Study

In this study, a dynamic analysis of self-stress levels of tensegrity systems is proposed. A direct relation between the first natural frequency of these systems and the levels of self-stress in the elements is established. It constitutes a first step toward the study of the adaptability of tensegrity systems to external loads; this adaptability could be realized by adjusting the levels of self-stress of one or several cable elements. The study is carried out using continuous struts tensegrity systems made of linear associations of simplex type modules. When subjected to static loading, tensegrity systems show an evolution of their frequencies with respect to the tension levels in the elements. The frequencies are computed assuming the structure oscillates linearly about its static equilibrium position. This evolution can be used, to associate the level of self-stress to a desired resonant frequency of the system. The harmonic dynamic loading of these systems, confirms their non linear characters and show a particular evolution of the tension-frequency relation.