scholarly journals Damped dynamic response of strengthened beams by composite coats under moving force by FEM

2018 ◽  
Vol 106 (2) ◽  
pp. 206
Author(s):  
Abdennacer Chemami ◽  
Youcef Khadri ◽  
Sabiha Tekili ◽  
El Mostafa Daya ◽  
Ali Daouadji ◽  
...  
Keyword(s):  
Dynamic Response ◽  
Numerical Study ◽  
Moving Load ◽  
Damping Ratio ◽  
Time Integration ◽  
Superposition Method ◽  
Dynamic Amplification Factor ◽  
Aluminum Composite ◽  
Strengthened Beam ◽  
Dynamic Amplification

This paper presents a numerical study of the free and damped forced vibration of simply-supported beams with composite coats subjected to a moving load by use of finite elements method. Three types of beam configurations, aluminum, composite and strengthened beam are investigated. The equation of motion of the beam is solved using the modal superposition method and integrated by applying the Newmark time integration procedure. Good agreements were achieved between the FEM and analytical solutions. The damped dynamic response, critical velocities and the dynamic amplification factor of the beam are calculated for different parameters such as the thickness ratio, the fiber orientation of the coat and damping ratio.

scholarly journals Effect of temperature and porosities on dynamic response of functionally graded beams carrying a moving load

2017 ◽  
Vol 20 (K2) ◽  
pp. 24-33
Author(s):  
Tuyen Van Bui
Keyword(s):  
Dynamic Response ◽  
Temperature Rise ◽  
Material Properties ◽  
Amplification Factor ◽  
Moving Load ◽  
Functionally Graded ◽  
Effect Of Temperature ◽  
Element Formulation ◽  
Dynamic Amplification Factor ◽  
Dynamic Amplification

The effect of temperature and porosities on the dynamic response of functionally graded beams carrying a moving load is investigated. Uniform and nonlinear temperature distributions in the beam thickness are considered. The material properties are assumed to be temperature dependent and they are graded in the thickness direction by a power-law distribution. A modified rule of mixture, taking the porosities into consideration, is adopted to evaluate the effective material properties. Based on Euler-Bernoulli beam theory, equations of motion are derived and they are solved by a finite element formulation in combination with the Newmark method. Numerical results show that the dynamic amplification factor increases by the increase of the temperature rise and the porosity volume fraction. The increase of the dynamic amplification factor by the temperature rise is more significant by the uniform temperature rise and for the beam associated with a higher grading index.

Dynamic Response of Fractionally Damped Viscoelastic Plates Subjected to a Moving Point Load

2020 ◽  
Vol 142 (4) ◽  
Author(s):  
Rajendra Kumar Praharaj ◽  
Nabanita Datta ◽  
Mohammed Rabius Sunny
Keyword(s):  
Dynamic Response ◽  
Fractional Derivative ◽  
Dynamic Behavior ◽  
Moving Load ◽  
Viscoelastic Model ◽  
Point Load ◽  
Dynamic Amplification Factor ◽  
Modal Summation ◽  
Liouville Fractional Derivative ◽  
Dynamic Amplification

Abstract The dynamic response of fractionally damped viscoelastic plates subjected to a moving point load is investigated. In order to capture the viscoelastic dynamic behavior more accurately, the material is modeled using the fractionally damped Kelvin–Voigt model (rather than the integer-type viscoelastic model). The Riemann–Liouville fractional derivative of order 0 < α ≤ 1 is applied. Galerkin's method and Newton–Raphson technique are used to evaluate the natural frequencies and corresponding damping coefficients. The structure is subject to a moving point load, traveling at different speeds. The modal summation technique is applied to generate the dynamic response of the plate. The influence of the order of the fractional derivative on the free and transient vibrations is studied for different velocities of the moving load. The results are compared with those using the classical integer-type Kelvin–Voigt viscoelastic model. The results show that an increase in the order of the fractional derivative causes a significant decrease in the maximum dynamic amplification factor, especially in the “dynamic zone” of the normalized sweep time. The dynamic behavior of the plate is verified with ansys.

scholarly journals Dynamic Response of Long Rectangular Floors Subjected to Periodic Force Excitation

Materials ◽  
2019 ◽  
Vol 12 (9) ◽  
pp. 1417 ◽  
Author(s):  
Zsuzsa B. Pap ◽  
László P. Kollár
Keyword(s):  
Dynamic Response ◽  
Amplification Factor ◽  
Damping Ratio ◽  
Effective Width ◽  
Rectangular Plates ◽  
Dynamic Amplification Factor ◽  
Periodic Force ◽  
Static Loads ◽  
Dynamic Amplification ◽  
Force Excitation

Since damping in lightweight floors is usually low, dynamic amplification can be rather high. Long rectangular plates subjected to concentrated loads are often investigated by a replacement beam with a so called “effective width”. Although this approach is a reliable tool for static loads, the steady-state dynamic response of beams and long plates subjected to periodic loads are significantly different. The maximum displacements and accelerations of beams (and of not-long rectangular plates) are obtained by using a dynamic amplification factor, which in the case of resonance is equal to 1 / 2 ξ , where ξ is the damping ratio. For long plates (and for not-long orthotropic rib-stiffened plates), as discussed in the paper, the response and the amplification factor are substantially different from those of beams. Hence, design based on effective width may lead to 2–4 times higher acceleration than the real values. In an economic design, to avoid unnecessary damping enhancement, this effect must be taken into account.

Dynamic analysis of railway with locally continuous supported superstructures

2019 ◽  
Vol 36 (9) ◽  
pp. 3047-3069
Author(s):  
Muzaffer Metin ◽  
Arif Ulu ◽  
Ozgur Demir ◽  
Aytac Arikoglu
Keyword(s):  
Dynamic Response ◽  
Moving Load ◽  
Damping Ratio ◽  
Time Integration ◽  
Three Dimensional ◽  
Equation System ◽  
Solution Technique ◽  
Vehicle Speed ◽  
Content Type ◽  
Three Dimensional Finite Element

Purpose In this study, a railway superstructure is modeled with a new approach called locally continuous supporting, and its behavior under the effect of moving load is analyzed by using analytical and numerical techniques. The purpose of the study is to demonstrate the success of the new modeling technique. Design/methodology/approach In the railway superstructure, the support zones are not modeled with discrete spring-damping elements. Instead of this, it is considered to be a continuous viscoelastic structure in the local areas. To model this approach, the governing partial differential equations are derived by Hamilton’s principle and spatially discretized by the Galerkin’s method, and the time integration of the resulting ordinary differential equation system is carried out by the Newmark–Beta method. Findings Both the proposed model and the solution technique are verified against conventional one-dimensional and three-dimensional finite element models for a specific case, and a very good agreement between the results is observed. The effects of geometric, structural, and loading parameters such as rail-pad length, rail-pad stiffness, rail-pad damping ratio, the gap between rail pads and vehicle speed on the dynamic response of railway superstructure are investigated in detail. Originality/value There are mainly two approaches to the modeling of rail pads. The first approach considers them as a single spring-damper connected in parallel located at the centroid of the rail pad. The second one divides the rail pad into several parts, with each of part represented by an equivalent spring-damper system. To obtain realistic results with minimum CPU time for the dynamic response of railway superstructure, the rail pads are modeled as continuous linearly viscoelastic local supports. The mechanical model of viscoelastic material is considered as a spring and damper connected in parallel.

Dynamic response of bridges under travelling loads

1993 ◽  
Vol 20 (2) ◽  
pp. 287-298 ◽  
Author(s):  
J. L. Humar ◽  
A. M. Kashif
Keyword(s):  
Dynamic Response ◽  
Rational Design ◽  
Weight Ratio ◽  
Experimental Investigations ◽  
Speed Ratio ◽  
Force Model ◽  
Beam Model ◽  
Dynamic Amplification Factor ◽  
Design Procedures ◽  
Dynamic Amplification

In spite of a number of analytical and experimental investigations on the dynamic response of bridges to moving vehicle loads, the controlling parameters that govern the response have not been clearly identified. This has, in turn, inhibited the development of rational design procedures. Based on an analytical investigation of the response of a simplified beam model traversed by a moving mass, the present study identifies the governing parameters. The results clearly show why attempts to correlate the response to a single parameter, either the span length or the fundamental frequency, are unsuccessful. Simple design procedures are developed based on relationships between the speed ratio, the weight ratio, and the dynamic amplification factors; and a set of design curves are provided. Key words: dynamic response of bridges, vehicle–bridge interaction, moving force model, moving sprung mass model, dynamic amplification factor.

scholarly journals Optimal Design and Application of a Multiple Tuned Mass Damper System for an In-Service Footbridge

2019 ◽  
Vol 11 (10) ◽  
pp. 2801 ◽  
Author(s):  
Chao Wang ◽  
Weixing Shi
Keyword(s):  
Optimal Design ◽  
Vibration Control ◽  
Damping Ratio ◽  
Element Model ◽  
Frequency Bandwidth ◽  
Dynamic Amplification Factor ◽  
Control Effect ◽  
In Situ Test ◽  
Dynamic Amplification

Slender steel footbridges suffer excessive human-induced vibrations due to their low damping nature and their frequency being located in the range of human-induced excitations. Tuned mass dampers (TMDs) are usually used to solve the serviceability problem of footbridges. A multiple TMD (MTMD) system, which consists of several TMDs with different frequencies, has a wide application in the vibration control of footbridges. An MTMD system with well-designed parameters will have a satisfactory effect for vibration control. This study firstly discusses the relationship between the acceleration dynamic amplification factor and important parameters of an MTMD system, i.e., the frequency bandwidth, TMD damping ratio, central frequency ratio, mass ratio and the number of TMDs. Then, the frequency bandwidth and damping ratio optimal formulas are proposed according to the parametric study. At last, an in-service slender footbridge is proposed as a case study. The footbridge is analyzed through a finite element model and an in situ test, and then, an MTMD system is designed based on the proposed optimal design formulas. The vibration control effect of the MTMD system is verified through a series of in situ comparison tests. Results show that under walking, running and jumping excitations with different frequency, the MTMD system always has an excellent vibration control effect. Under a crowd-induced excitation with the resonance frequency, the footbridge with an MTMD system can meet the acceleration limit requirement. It is also found that the analysis result agrees well with the in situ test.

Dynamic Response of High Steep Rock Slopes Based on Wenchuan Near-Field Seismic Motion Characteristics

2010 ◽  
Vol 168-170 ◽  
pp. 1090-1097
Author(s):  
Shi Guo Xiao ◽  
Wen Kai Feng
Keyword(s):  
Numerical Analysis ◽  
Dynamic Response ◽  
Amplification Factor ◽  
Near Field ◽  
Seismic Load ◽  
Rock Slopes ◽  
Dynamic Amplification Factor ◽  
Seismic Motion ◽  
Dynamic Amplification ◽  
Motion Characteristics

Near-field seismic motion characteristics are analyzed in accordance with records of the 2008 Ms8.0 Wenchuan Earthquake measured at Wolong Station, upon which the determination of seismic load is introduced. Dynamic response features, such as acceleration, displacement and stress, of high steep rock slopes on the banks of Zipingpu Reservoir at a variety of locations resulting from horizontal seismic force are analyzed with a numerical analysis routine. The dynamic amplification factor on the slope top is determined, leading to a characterization of the mode of failure of the high steep slope. Analyses show that the dynamic amplification factor at the top of the slopes is about 1.34; however, dynamic response deformation features and stress state at different positions on the slope vary. Earthquake damage of the high steep rock slopes consists mainly of partial avalanche of the rock mass at the top of the slopes by joint cutting. Field investigations after the earthquake have partially confirmed the numerical analysis results presented in this paper.

Dynamic Behaviour of Minimum Platforms Under Random Seas

2003 ◽  
Author(s):  
Micaela Pilotto ◽  
Beverley F. Ronalds
Keyword(s):  
Dynamic Response ◽  
Dynamic Behaviour ◽  
Amplification Factor ◽  
Finite Element Models ◽  
Dynamic Amplification Factor ◽  
Maximum Value ◽  
Random Seas ◽  
Exponential Stretching ◽  
Structural Configurations ◽  
Dynamic Amplification

This paper describes the dynamic response of minimum facilities with different structural configurations which are subjected to random seas. The finite element models are kept simple with the aim of focusing on the physics of the phenomena involved. The response is studied in terms of the dynamic amplification factor (DAF), representing the ratio between the dynamic and the static response. Two different formulations of the DAF under random seas are compared. The first is defined in terms of standard deviation (DAF1), the second in terms of the most probable maximum value (DAF2). Ringing is observed to be a relevant feature of the dynamic response and to affect primarily the braced monopod configurations. Ringing is detected using DAF2. The paper also addresses the importance of the kinematic representation above the still water level. Different methods of stretching the velocity field in the wave zone (delta, Wheeler and exponential stretching) are shown to have a significant impact on the dynamic response of the platforms.

scholarly journals Damping in Dynamic Structure–Foundation Interaction

1975 ◽  
Vol 12 (1) ◽  
pp. 13-22 ◽  
Author(s):  
J. H. Rainer
Keyword(s):  
Damping Ratio ◽  
Dynamic Structure ◽  
Numerical Results ◽  
Material Damping ◽  
Dynamic Amplification Factor ◽  
Foundation Soil ◽  
Modal Damping Ratio ◽  
Modal Damping ◽  
Fixed Base ◽  
Dynamic Amplification

Two methods of calculating the damping ratio for structures on compliant foundations are presented. One method employs the calculation of the system damping ratio from the dynamic amplification factor, the other the modal damping ratio from energy considerations. The numerical results for both methods are compared and interpreted. Three sources of damping are considered: inter-storey damping, radiation damping, and foundation material damping. The numerical results demonstrate that with the introduction of compliant foundations the damping ratio of the system can be larger or smaller than that of the corresponding fixed-base structure. Material damping in the foundation soil has been shown to contribute significantly to the over-all damping ratio.

scholarly journals Evaluation of the Increased Dynamic Effects on the Highway Bridge Superstructure

2018 ◽  
Vol 13 (3) ◽  
Author(s):  
Ilze Paeglite ◽  
Juris Smirnovs ◽  
Ainars Paeglitis
Keyword(s):  
Amplification Factor ◽  
Dynamic Properties ◽  
Concrete Slab ◽  
Damping Ratio ◽  
Dynamic Amplification Factor ◽  
Reinforced Concrete Slab ◽  
Girder Bridges ◽  
Bridge Superstructure ◽  
High Dynamic ◽  
Dynamic Amplification

Dynamic properties of the bridge superstructure vary depending on many characteristics of the bridge and the loading conditions. In this paper, maximum Dynamic Amplification Factor was calculated for six different types of typical pre-stressed concrete beam bridges. It showed that each type of bridge with similar loading has a different range of Dynamic Amplification Factor. At the same time, every recently built bridge has different geometry and design load. Hence, it is difficult to determine a characteristic value of Dynamic Amplification Factor for the similar type of structures. By using fullscale dynamic and static bridge tests, it is possible to determine the necessary characteristics which show possibly high Dynamic Amplification Factor. This factor indicates if it is necessary to make a full-scale bridge dynamic analysis. It was found that those characteristics are natural frequency (first mode), damping ratio, relative deflection, and span and depth ratio. Obtained results from tests show a range of values for each of the characteristic. These ranges were analysed for reinforced concrete slab and pre-stressed concrete slab, and girder bridges.

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