• Proceedings of the KSME Conference
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• 2007.05a
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• pp.315-320
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• 2007

An analytical solution has been developed for the impact response of delaminated composite plates. The analysis is based on an expansion of loads, displacements, and rotations in a Fourier series which satisfies the end boundary conditions of simply-supported. The analytical formulation adopts the Laplace transformation technique, requiring a linearization of contact deformation. In this paper, the nonlinear contact stiffness is replaced by a linearized stiffness, to provide an estimate of the additional compliance due to contact area deformation effects. It has been shown that defects such as delaminations may be modeled as spring stiffness. The change in the impact characteristics as this spring stiffness has been investigated theoretically. Predicted impact responses using analytical solution are compared with the numerical ones from the 3-D non-linear finite element model. From the results, it is shown that analytical solution was found to be reliable for predicting the impact response.

• Journal of the Korean Society for Precision Engineering
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• v.26 no.8
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• pp.79-88
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• 2009

This paper presents the analytical stiffness analysis method for a low-DOF planar parallel manipulator. An n-DOF (n<3) planar parallel manipulator to which 1- or 2-DOF serial mechanism is connected in series may be used as a positioning device in planar tasks requring high payload and high speed. Differently from a 3-DOF planar parallel manipulator, an n-DOF planar parallel counterpart may be subject to constraint forces as well as actuation forces. Using the theory of reciprocal screws, the planar stiffness is modeled such that the moving platform is supported by three springs related to the reciprocal screws of actuations (n) and constraints (3-n). Then, the spring constants can be precisely determined by modeling the compliances of joints and links in serial chains. Finally, the stiffness of two kinds of 2-DOF planar parallel manipulators with simple and complex springs is analyzed. In order to show the effectiveness of the suggested method, the results of analytical stiffness analysis are compared to those of numerical stiffness analysis by using ADAMS.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.24 no.10
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• pp.749-755
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• 2014

The analytical-finite element(FE) squeal model is applied to investigate the squeal propensity associated with contact stiffness of the disc brake system. The system contact stiffness is incorporated into the perturbed equations of motion in the analytical manner where the brake components are modeled by FE method. The results show that the contact stiffness of the friction material and the contact stiffness between the pads and caliper are the influential factors on the squeal propensity. Particularly, the modal instability of the 3200 Hz squeal mode drastically changes with respect to the contact stiffness between the pads and caliper.

• Structural Engineering and Mechanics
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• v.31 no.2
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• pp.163-180
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• 2009

In the design of tall reinforced concrete (R/C) buildings, the serviceability stiffness criteria in terms of maximum lateral displacement and inter-story drift must be satisfied to prevent large second-order P-delta effects. To accurately assess the lateral deflection and stiffness of tall R/C structures, cracked members in these structures need to be identified and their effective member flexural stiffness determined. In addition, the implementation of the geometric nonlinearity in the analysis can be significant for an accurate prediction of lateral deflection of the structure, particularly in the case of tall R/C building under lateral loading. It can therefore be important to consider the cracking effect together with the geometric nonlinearity in the analysis in order to obtain more accurate results. In the present study, a computer program based on the iterative procedure has been developed for the three dimensional analysis of reinforced concrete frames with cracked beam and column elements. Probability-based effective stiffness model is used for the effective flexural stiffness of a cracked member. In the analysis, the geometric nonlinearity due to the interaction of axial force and bending moment and the displacements of joints are also taken into account. The analytical procedure has been demonstrated through the application of R/C frame examples in which its accuracy and efficiency in comparison with experimental and other analytical results are verified. The effectiveness of the analytical procedure is also illustrated through a practical four story R/C frame example. The iterative procedure provides equally good and consistent prediction of lateral deflection and effective flexural member stiffness. The proposed analytical procedure is efficient from the viewpoints of computational effort and convergence rate.

• Earthquakes and Structures
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• v.1 no.1
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• pp.1-19
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• 2010

It has been known that one-dimensional rod theory is very effective as a simplified analytical approach to large scale or complicated structures such as high-rise buildings, in preliminary design stages. It replaces an original structure by a one-dimensional rod which has an equivalent stiffness in terms of global properties. If the structure is composed of distinct constituents of different stiffness such as coupled walls with opening, structural behavior is significantly governed by the local variation of stiffness. This paper proposes an extended version of the rod theory which accounts for the two-dimensional local variation of structural stiffness; viz, variation in the transverse direction as well as longitudinal stiffness distribution. The governing equation for the two-dimensional rod theory is formulated from Hamilton's principle by making use of a displacement function which satisfies continuity conditions across the boundary between the distinct structural components in the transverse direction. Validity of the proposed theory is confirmed by comparison with numerical results of computational tools in the cases of static, free vibration and forced vibration problems for various structures.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2006.04a
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• pp.405-412
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• 2006

Among the various problems involved in the structural analysis of the Korean traditional wooden structure, the analytical model for the Kong-Po is controversial subject as usual. While some experiments are tried for establishing the basis of analytical models, most of these experiments are performed using scale down specimens. So, it is not possible to apply these experimental results to structural analysis of Korean traditional wooden structure directly. A numerical study for analogizing the stiffness of full scale Kong-Po structure is performed on the basis of experimental specimen. Some parameter studies using finite element method are made in this study. The finite element analysis used in this study is geometric material nonlinear analysis. The stiffness of Kong-Po structure found out in this study can be used for modelling the joints of the Korean traditional wood structure in frame analysis.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2003.03a
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• pp.302-310
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• 2003

Cracking of slabs will be caused by applied load and volume changes during the life of a structure and thus it reduces flexural stiffness of slabs. The effect of slab cracking must be considered for appropriate modeling of the flexural stiffness for frame members used in structural analysis. Analytical and experimental study was undertaken to estimate the stiffness reduction of slabs. In the analytical approach, the trend of slab stiffness reduction related to gravity and lateral loads is found and the stiffness reduction factor ranged from a half to a quarter in ACI building code is reasonable when defining range. Analyzing results of the test by Hwang and Moehle for 0.5% drift show that the differences of rotational stiffness on the connection types is found and good results of lateral stiffness using the value of one-third is obtained.

• Structural Engineering and Mechanics
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• v.63 no.5
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• pp.669-681
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• 2017

The design of reinforced concrete buildings must satisfy the serviceability stiffness criteria in terms of maximum lateral deflections and inter story drift in order to prevent both structural and non-structural damages. Consideration of plastic hinge formation is also important to obtain accurate failure mechanism and ultimate strength of reinforced concrete frames. In the present study, an iterative procedure has been developed for the analysis of reinforced concrete frames with cracked elements and consideration of plastic hinge formation. The ACI and probability-based effective stiffness models are used for the effective moment of inertia of cracked members. Shear deformation effect is also considered, and the variation of shear stiffness due to cracking is evaluated by reduced shear stiffness models available in the literature. The analytical procedure has been demonstrated through the application to three reinforced concrete frame examples available in the literature. It has been shown that the iterative analytical procedure can provide accurate and efficient predictions of deflections and ultimate strength of the frames studied under lateral and vertical loads. The proposed procedure is also efficient from the viewpoint of computational time and convergence rate. The developed technique was able to accurately predict the locations and sequential development of plastic hinges in frames. The results also show that shear deformation can contribute significantly to frame deflections.

• Structural Engineering and Mechanics
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• v.77 no.5
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• pp.601-612
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• 2021

To study the vibration characteristics of a high-speed railway continuous girder bridge-track coupling system (HSRCBT), a coupling vibration analysis model of an m-span continuous girder bridge-subgrade-track system with n-span approach bridge was established. The model was based on the energy and its variational method, where both the interlaminar slip and shear deformation effects were considered. In addition, the free vibration equations and natural boundary conditions of the HSRCBT were derived. Further, according to the coordination principle of deformation and mechanics, an analytical method for calculating the natural vibration frequencies of the HSRCBT was obtained. Three typical bridge-subgrade-track coupling systems of high-speed railway were taken and the results of finite element analysis were compared to those of the analytical method. The errors between the simulation results and calculated values of the analytical method were less than 3%, thus verifying the analytical method proposed in this paper. Finally, the analytical method was used to investigate the influence of the number of the approach bridge spans and the interlaminar stiffness on the natural vibration characteristics of the HSRCBT based on the degree of sensitivity. The results suggest the approach bridges have a critical number of spans and in general, the precision requirements of the analysis could be met by using 6-span approach bridges. The interlaminar vertical compressive stiffness has very little influence on the low-order natural vibration frequency of HSRCBT, but does have a significant influence on higher-order natural vibration frequency. As the interlaminar vertical compressive stiffness increases, the degree of sensitivity to interlaminar stiffness of each of the HSRCBT natural vibration characteristics decrease and gradually approach zero.

• Magazine of the Korea Concrete Institute
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• v.7 no.1
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• pp.156-164
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• 1995

P-${\Delta}$ analysis by use of the equivalent colurnn stiffness determined by Momcnt curvature-Thrust curves provides relatively precise analytical results for unbraced reinforced concrete columns, however it needs a complicated arialytical procedure. Equ~valent col~rnn stiffness equations are proposed for a simple analytical procedure which are ckterrnined by the Moment-Curvature Thrust curves of the practically useable sections. Thc proposed stiffness equations are appiled to P-${\Delta}$ analysis and rnornent magnifier method to compare with the selected test result. Use of the proposed stiffness equations may slrnplify the P-${\Delta}$ i.rialvtica1 procedure and improve the accuracy of moment magnifier niethod.