• Steel and Composite Structures
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• v.19 no.6
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• pp.1421-1447
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• 2015

In this paper, the effect of material-temperature dependent on the wave propagation of a cantilever beam composed of functionally graded material (FGM) under the effect of an impact force is investigated. The beam is excited by a transverse triangular force impulse modulated by a harmonic motion. Material properties of the beam are temperature-dependent and change in the thickness direction. The Kelvin-Voigt model for the material of the beam is used. The considered problem is investigated within the Euler-Bernoulli beam theory by using energy based finite element method. The system of equations of motion is derived by using Lagrange's equations. The obtained system of linear differential equations is reduced to a linear algebraic equation system and solved in the time domain and frequency domain by using Newmark average acceleration method. In order to establish the accuracy of the present formulation and results, the comparison study is performed with the published results available in the literature. Good agreement is observed. In the study, the effects of material distributions and temperature rising on the wave propagation of the FGM beam are investigated in detail.

• Transactions of the Korean Society of Mechanical Engineers
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• v.12 no.4
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• pp.652-661
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• 1988

A theoretical attempt is made to analyze the dynamic contact force and response of laminated composite beams subjected to the transverse impact of steel balls. A beam finite element model based on the modified theory for laminated composites in conjunction with static contact laws is formulated for the theoretical investigation. Finally, it is shown that the present results are in good agreement with some existing solutions or wave propagation theory.

• International Journal of Concrete Structures and Materials
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• v.5 no.1
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• pp.19-28
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• 2011

This paper documents an experimental study of dynamic response of reinforced concrete beams following instantaneous removal of a bearing column. Four half-scale specimens representing two-span beam bridging across the removed column were tested. The test boundary conditions simulated rotational and longitudinal restraints imposed on a frame beam by the neighboring structural components. The gravity loads were simulated by attaching mass blocks on the beams at three locations. Dynamic loading effects due to sudden removal of a column were simulated by quickly releasing the supporting force at the middle of the specimens. The experimental study investigated the load-carrying capacity of beams restrained longitudinally at the boundaries and dynamic impact on forces. The tests confirmed the extra flexural strength provided by compressive arch action under dynamic loading. The tests also indicated that the dynamic amplification effects on forces were much lower than that assumed in the current design guideline for progressive collapse.

• Structural Engineering and Mechanics
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• v.3 no.5
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• pp.463-474
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• 1995

When a tubular cantilever beam is loaded by a dynamic force applied transversely at its tip, the strain hardening of the material tends to increase the load carrying capacity and local buckling and cross-sectional overlization occurring in the tube section tends to reduce the moment carrying capacity and results in structural softening. A theoretical model is presented in this paper to analyze the deformation of a tubular beam in a dynamic response mode. Based on a large deflection analysis, the hardening/softening M-${\kappa}$ relationship is introduced. The main interest is on the curvature development history and the deformed configuration of the beam.

• Structural Engineering and Mechanics
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• v.37 no.1
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• pp.79-93
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• 2011

A simple mechanical model is proposed to demonstrate qualitatively the pancake progressive collapse of multi-storey structures. The impact between two collapsed storeys is simulated using a simple algorithm that builds on virtual mass-spring-damper system. To analyze various collapse modes, columns and beams are considered separately. Parametric studies show that the process of progressive collapse involves a large number of complex mechanisms. However, the proposed model provides a simple numerical tool to assess the overall behavior of collapse arising from a few initiating causes. Unique features, such as beam-to-beam connection failure criterion, and beam-to-column connection failure criterion are incorporated into the program. Besides, the criterion of local failure of structural members can also be easily incorporated into the proposed model.

• Structural Engineering and Mechanics
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• v.82 no.5
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• pp.629-641
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• 2022

This study deals with the spinning impact on flap-wise vibration characteristics of nonlocal functionally graded (FG) cylindrical beam based on the Hyperbolic shear deformation beam theory. The nonlocal strain gradient theory is used to investigate the small-scale impact on the nonlocal motion equation as well as corresponding nonlocal boundary conditions. Based on the mathematical simulation and according to the Hamilton principle, the computerized modeling of a rotating functionally graded nanotube is generated, and then, via a numerical approach, the obtained mathematical equations are solved. The calculated outcomes are helpful to the production of Nano-electro-mechanical-systems (NEMS) by investigating some designed parameters such as rotating speed, hub radius, length-scale parameters, volume fraction parameters, etc.

• Computers and Concrete
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• v.32 no.1
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• pp.75-85
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• 2023

This work utilizes simplified higher-order shear deformation beam theory (HSDBT) to investigate the vibration response for functionally graded carbon nanotube-reinforced composite (CNTRC) beam. Novel to this work, single-walled carbon nanotubes (SWCNTs) are distributed and aligned in a matrix of polymer throughout the beam, resting on a viscoelastic foundation. Four un-similar patterns of reinforcement distribution functions are investigated for the CNTRC beam. Porosity is another consideration taken into account due to its significant effect on functionally graded materials (FGMs) properties. Three types of uneven porosity distributions are studied in this study. The damping coefficient and Winkler's and Pasternak's parameters are considered in investigating the viscosity effect on the foundation. Moreover, the impact of different parameters on the vibration of the CNTRC beam supported by a viscoelastic foundation is discussed. A comparison to other works is made to validate numerical results in addition to analytical discussions. The findings indicate that incorporating a damping coefficient can improve the vibration performance, especially when the spring constant factors are raised. Additionally, it has been noted that the fundamental frequency of a beam increases as the porosity coefficient increases, indicating that porosity may have a significant impact on the vibrational characteristics of beams.

• Proceeding of EDISON Challenge
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• 2017.03a
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• pp.194-203
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• 2017

The center of percussion(COP) is the point of an extended massive object attached to a pivot where a perpendicular impact will produce no reactive shock at the pivot. COP is an important concept in the field of vibration and dynamics. In vibration, COP causes reduction of vibration and in dynamics, it brings about maximum speed of an object. Many studies about COP are still in progress. However most of the researches have typically focused on the method of mathematical and numerical anlalysis. In this paper, impact analysis was proved by the mechanical energy method using EDISON co-rotational plane beam transient analysis program. The result expressed in acceleration was the relative magnitude of the impulse, which was the indicator of COP. Then, these results were compared with the reference thesis results for exact consequences. Additionally, parametric study of COP was conducted.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.26 no.5
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• pp.609-615
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• 2016

Measuring similarity between two signals is a key element of the location template matching (LTM) method which is one of impact source localization technique. As a measure of similarity, the correlation coefficient is most widely used, and the group delay based method is recently proposed to improve the accuracy of finding the impact source. In practice, the LTM method assumes that the similarity between two signals decreases as the distance between two corresponding impact points increases, where the distance between two neighboring impact points defines the grid spacing. In this paper, it is shown that this assumption is not always true but the correlation coefficients fluctuate forming a main robe and many side robes as the distance between two neighboring impact points increases. On the other hand, the standard deviation of group delay sharply increases with a small increase of the grid spacing. These are demonstrated by using a simple cantilever beam. Based on these findings, an optimal way of implementing the LTM method may be suggested by combining the correlation coefficient and the group delay based approaches.

• Journal of Radiation Industry
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• v.5 no.2
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• pp.145-149
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• 2011

Poly(butylenes terephthalate) have made large strides in applications of injection, extrusion, and molding material due to their excellent thermal resistance and appropriate mechanical properties. However, PBT was not hard polymer but a soft polymer which caused low absorption of external energy and the defect of being easily broken with the strong impact. Thus, the electron beam irradiation was carried out over a range of irradiation doses from 100 to 1,000 kGy for enhancing the properties. The decreases of $T_m$, $T_c$, and enthalpy were observed as increasing the absorbed dose in the results of DSC analysis. The improvement in the impact strength of PBT was clearly observed as the absorbed dose was increased. This was probably due to the 3-dimensional network structures, resulting in increasing the absorption of impact energy. In addition, the wear properties had increased at higher than 300 kGy. The negative deviation of weight loss confirmed the improvement of the wear properties of PBT, as evidenced by SEM observation on the wear surfaces.