• Computers and Concrete
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• v.20 no.6
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• pp.671-682
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• 2017

In this research, seismic response of pipes is examined by applying nanotechnology and piezoelectric materials. For this purpose, a pipe is considered which is reinforced by carbon nanotubes (CNTs) and covered with a piezoelectric layer. The structure is subjected to the dynamic loads caused by earthquake and the governing equations of the system are derived using mathematical model via cylindrical shell element and Mindlin theory. Navier-Stokes equation is employed to calculate the force due to the fluid in the pipe. Mori-Tanaka approach is used to estimate the equivalent material properties of the nanocomposite and to consider the effect of the CNTs agglomeration on the scismic response of the structure. Moreover, the dynamic displacement of the structure is extracted using harmonic differential quadrature method (HDQM) and Newmark method. The main goal of this research is the analysis of the seismic response using piezoelectric layer and nanotechnology. The results indicate that reinforcing the pipeline by CNTs leads to a reduction in the displacement of the structure during an earthquake. Also the negative voltage applied to the piezoelectric layer reduces the dynamic displacement.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.06a
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• pp.627-632
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• 2000

A finite element model for the transient dynamic analysis of a PWR fuel assembly was developed and programmed as a name of DAMASS. The Newmark time integration method was used to solve the governing equation of motion. Results of the program was compared with those of ANSYS in terms of displacement and impact forces to show the validity of the model. Up to now it has capability of solving the linear impact of FA(s) and it will be extended to the non-linear analysis of a FA in the future.

• Structural Engineering and Mechanics
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• v.46 no.1
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• pp.75-90
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• 2013

In order to identify damage of highway bridges rapidly, a method for damage identification using dynamic response of bridge induced by moving vehicle and static test data is proposed. To locate damage of the structure, displacement energy damage index defined from the energy of the displacement response time history is adopted as the indicator. The displacement response time histories of bridge structure are obtained from simulation of vehicle-bridge coupled vibration analysis. The vehicle model is considered as a four-degree-of-freedom system, and the vibration equations of the vehicle model are deduced based on the D'Alembert principle. Finite element method is used to discretize bridge and finite element model is set up. According to the condition of displacement and force compatibility between vehicle and bridge, the vibration equations of the vehicle and bridge models are coupled. A Newmark-${\beta}$ algorithm based professional procedure VBAP is developed in MATLAB, and used to analyze the vehicle-bridge system coupled vibration. After damage is located by employing the displacement energy damage index, the damage extent is estimated through the least-square-method based model updating using static test data. At last, taking one simply supported bridge as an illustrative example, some damage scenarios are identified using the proposed damage identification methodology. The results indicate that the proposed method is efficient for damage localization and damage extent estimation.

• Steel and Composite Structures
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• v.27 no.3
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• pp.255-271
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• 2018

This paper deals with the transient dynamic analysis and elastic wave propagation in a functionally graded graphene platelets (FGGPLs)-reinforced composite thick hollow cylinder, which is subjected to shock loading. A micromechanical model based on the Halpin-Tsai model and rule of mixture is modified for nonlinear functionally graded distributions of graphene platelets (GPLs) in polymer matrix of composites. The governing equations are derived for an axisymmetric FGGPLs-reinforced composite cylinder with a finite length and then solved using a hybrid meshless method based on the generalized finite difference (GFD) and Newmark finite difference methods. A numerical time discretization is performed for the dynamic problem using the Newmark method. The dynamic behaviors of the displacements and stresses are obtained and discussed in detail using the modified micromechanical model and meshless GFD method. The effects of the reinforcement of the composite cylinder by GPLs on the elastic wave propagations in both displacement and stress fields are obtained for various parameters. It is concluded that the proposed micromechanical model and also the meshless GFD method have a high capability to simulate the composite structures under shock loadings, which are reinforced by FGGPLs. It is shown that the modified micromechanical model and solution technique based on the meshless GFD method are accurate. Also, the time histories of the field variables are shown for various parameters.

• Structural Engineering and Mechanics
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• v.45 no.6
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• pp.741-758
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• 2013

In this study, inelastic displacement ratios are investigated for existing systems with known lateral strength considering soil structure interaction. For this purpose, SDOF systems for period range of 0.1-3.0 s with different hysteretic behaviors are considered for a number of 18 earthquake motions recorded on soft soil. The effect of stiffness degradation on inelastic displacement ratios is investigated. The Modified Clough model is used to represent structures that exhibit significant stiffness degradation when subjected to reverse cyclic loading and the elastoplastic model is used to represent non-degrading structures. Soil structure interaction analyses are conducted by means of equivalent fixed base model effective period, effective damping and effective ductility values differing from fixed-base case. For inelastic time history analyses, Newmark method for step by step time integration was adapted in an in-house computer program. A new equation is proposed for inelastic displacement ratio of system with SSI with elastoplastic or degrading behavior as a function of structural period ($\tilde{T}$), strength reduction factor (R) and period lengthening ratio ($\tilde{T}$/T). The proposed equation for $\tilde{C}_R$ which takes the soil-structure interaction into account should be useful in estimating the inelastic deformation of existing structures with known lateral strength.

• Wind and Structures
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• v.29 no.2
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• pp.129-137
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• 2019

The maximum along-wind displacement of a considerable amount of building under simulated wind loads is computed with the aim to produce a simple prediction model using multiple regression analysis with variables transformation. The Shinozuka and Newmark methods are used to simulate the turbulent wind and to calculate the dynamic response, respectively. In order to evaluate the prediction performance of the regression model with longer degree of determination, two complex structural models were analyzed dynamically. In addition, the prediction model proposed is used to estimate and compare the maximum response of two test buildings studied with wind loads by other authors. Finally, it was proved that the prediction model is reliable to estimate the maximum displacements of structures subjected to the wind loads.

• Earthquakes and Structures
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• v.21 no.6
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• pp.601-612
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• 2021

The paper concerns the selection of a design accelerograms used for the slope stability assessment under earthquake excitation. The aim is to experimentally verify the Arias Intensity as an indicator of the excitation threat to the slope stability. A simple dynamic system consisting of a rigid block on a rigid inclined plane subjected to horizontal excitation is adopted as a slope model. Strong ground motions recorded during earthquakes are reproduced on a shaking table. The permanent displacement of the block serves as a slope stability indicator. Original research stand allows us to analyse not only the relative displacement but also the acceleration time history of the block. The experiments demonstrate that the Arias Intensity of the accelerogram is a good indicator of excitation threat to the stability of the slope. The numerical analyses conducted using the experimentally verified extended Newmark's method indicate that both the Arias Intensity and the peak velocity of the excitation are good indicators of the impact of dynamic excitation on the dam's stability. The selection can be refined using complementary information, which is the dominant frequency and duration of the strong motion phase of the excitation, respectively.

• Economic and Environmental Geology
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• v.44 no.4
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• pp.289-302
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• 2011

Since the frequency of the earthquake occurrence in Korean peninsular is continuously increasing, the possibility that massive landslides are triggered by earthquake is also growing in Korea. Previously, the landslide is known to be induced by large magnitude earthquake, whose magnitude is larger than 6.0. However, the landslide can be induced by only small magnitude earthquake, especially in the fully saturated soil. Therefore, the susceptibility of landslide caused by small magnitude earthquake in fully saturated soil is analyzed in this study. For that, the topographical and geological characteristics of the site were obtained and managed by GIS software. In the procedure of the study, slope angle, cohesion, friction angle, unit weight of soil were obtained and constructed as a spatial database layer. Combining these data sets in a dynamic model based on Newmark's displacement analysis, the landslide displacements were estimated in each grid cell. In order to check out the possibility of the earthquake induced landslides, the level of the groundwater table is varied from dry to 80% saturated soil. In addition, in order to analyze the effect of the magnitude of earthquake and distance to epicenter, four different earthquakes epicenters were considered in the study area.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.13 no.5
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• pp.13-18
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• 1993

The purpose of this study is to analyze the seismic effects of Lead Rubber Bearing base isolators on bridges. Base isolation is the tool to minimize the effect of earthquake before the seismic force is transfered to the structure. Currently, many structures including the buildings, power plants, and bridges, were built and planned with base isolation method. The simple model is developed for bridges with Lead Rubber Bearings. Equations of motion are solved by Newmark ${\beta}$ method. Springs representing the base isolators are assumed as bilinear springs and piers are modeled as nonlinear springs implementing Q-HYST model. Analysis is performed for the selected bridge. El Centro (N-S) earthquake(1940) is used. Deck displacement, pier ductility and pier shear force are calculated for the various Lead Rubber Bearings.

• Structural Engineering and Mechanics
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• v.70 no.5
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• pp.551-562
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• 2019

In the present study, a suitable mathematical model considering parabolic transverse shear strains for dynamic analysis of laminated composite skew plates under different types of impulse and spatial loads was presented for the first time. The proposed mathematical model satisfies zero transverse shear strain at the top and bottom of the plate. On the basis of the cubic variation of thickness coordinate in in-plane displacement fields of the present mathematical model, a 2D finite element (FE) model was developed including skew transformations in the mathematical model. No shear correction factor is required in the present formulation and damping effect was also incorporated. This is the first FE implementation considering a cubic variation of thickness coordinate in in-plane displacement fields including skew transformations to solve the forced vibration problem of composite skew plates. The effect of transverse shear and rotary inertia was incorporated in the present model. The Newmark-${\beta}$ scheme was adapted to perform time integration from step to step. The $C^0$ FE formulation was implemented to overcome the problem of $C^1$ continuity associated with the cubic variation of thickness coordinate in in-plane displacement fields. The numerical studies showed that the present 2D FE model predicts the result close to the analytical results. Many new results varying different parameter such as skew angles, boundary conditions, etc. were presented.