• Steel and Composite Structures
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• 제43권4호
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• pp.447-456
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• 2022

Recent experimental studies showed that deep steel I-shaped profiles classified as high ductility class sections in seismic design international codes exhibit low deformation capacity when subjected to cyclic loading. This paper presents an innovative retrofit solution to increase the rotation capacity of beams using bonded carbon fiber reinforced polymers (CFRP) patches validated with advanced finite element analysis. This investigation focuses on the flexural cyclic behaviour of I-shaped hot rolled steel deep section used as beams in moment-resisting frames (MRF) retrofitted with CFRP patches on the web. The main goal of this CFRP reinforcement is to increase the rotation capacity of the member without increasing the overstrength in order to avoid compromising the strong column-weak beam condition in MRF. A finite element model that simulates the cyclic plasticity behavior of the steel and the damage in the adhesive layer is developed. The damage is modelled using the cohesive zone modelling (CZM) technique that is able to capture the crack initiation and propagation. Details on the modelling techniques including the mesh sensitivity near the fracture zone are presented. The effectiveness of the retrofit solution depends strongly on the selection of the appropriate adhesive. Different adhesive types are investigated where the CZM parameters are calibrated from high fidelity fracture mechanics tests that are thoroughly validated in the literature. This includes a rigid adhesive commonly found in the construction industry and two tough adhesives used in the automotive industry. The results revealed that the CFRP patch can increase the rotation capacity of a steel member considerably when using tough adhesives.

• 응용통계연구
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• 제17권1호
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• pp.61-73
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• 2004

교체표본조사에서는 모든 표본단위를 복수 개(=G)의 교체그룹으로 나누고 일정 횟수만큼 조사한 후 표본단위 의 교체를 하는 경우와 조사기 간 동안 동일한 표본단위를 조사한 후 교체그룹 자체를 교체하는 두 가지 경우가 있다. 본 연구는 후자의 경우를 일반화하는 것으로, 매 조사월에서 하나의 교체그룹이 조사되고 이 교체그룹에 속한 모든 표본단위는 최근 l개월 동안의 정보를 제공하는 l-수준 교체표본설계이다. 표본단위 교체가 오직 교체그룹의 총 개수인 G와 회상 개월 수인 l에 의해 결정되므로 이를 l/G 교체표본설계로 일반화하였으며 일반화복합추정량의 분산과 두 가지 형태의 편향(bias)하에서 MSE를 구하고 절충 GCE(compromise GCE)의 계수를 유도하였다. 또한 GCE의 분산과 MSE를 상관계수, 편향, 표본조사단위의 분산의 형태, 그리고 설계간격(design gap)의 형태에 따라 분석하였다.

• 한국전산구조공학회논문집
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• 제14권4호
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• pp.537-549
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• 2001

본 논문은 강 뼈대 구조물의 보-기둥 접합부의 사실적인 상태를 묘사하기 위하여 부분구속 접합부(Partially Restrained (PR) connections)를 고려한 지진하중 상태하의 신뢰성 해석과 접합부 및 그들에 내재된 불확실성이 구조물의 위험도에 미치는 영향에 관한 연구이다. 신뢰성해석을 위하여 응답면기법(Response Surface Method), 유한요소법(Finite Element Method), 일차신뢰도법(First Order Reliability Method), 그리고 반복선형보간 기법(Iterative Linear Interpolation Scheme)을 효과적으로 결합한 추계유한요소법(Stochastic Finite Element Method)을 제안하였다 일반적으로 모멘트-상대회전각 곡선에 의해서 표현되는 보-기둥에 대한 부분구속 접합부(PR connections)의 거동이 본 논문에서는 네 개의 매개변수를 사용하는 리차드 모델(Four-parameter Richard Model)을 사용하여 모사하였다. 지진하중에 대하여, 부분구속 접합부에서의 재하(Loading), 제하(Unloading) 및 재재하(Reloading) 거동은 모멘트-상대회전각 곡선과 Masing법칙을 사용하여 표현하였다. 시간영역에서 지진가속도를 구조물에 작용시킴으로써 지진하중의 사실적인 재현을 도모하였다. 다양한 주요 비선형성의 원인들을 고려한 부분구속 접합부를 가지는 강 뼈대 구조물의 신뢰성해석이 지진위험도를 평가하기 위하여 수행되었다. 제안된 기법의 명확한 이해를 돕기 위하여 한 예제를 제시하였다.

• Structural Engineering and Mechanics
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• 제6권7호
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• pp.727-746
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• 1998

Finite element models and numerical results are presented for bending and natural vibration using the unified third-order plate theory developed in Part 1 of this paper. The unified third-order theory contains the classical, first-order, and other third-order plate theories as special cases. Analytical solutions are developed using the Navier and L$\acute{e}$vy solution procedures (see Part 1 of the paper). Displacement finite element models of the unified third-order theory are developed herein. The finite element models are based on $C^0$ interpolation of the inplane displacements and rotation functions and $C^1$ interpolation of the transverse deflection. Numerical results of bending and natural vibration are presented to evaluate the accuracy of various plate theories.

• Advances in aircraft and spacecraft science
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• 제3권4호
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• pp.379-397
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• 2016

In this manuscript, free vibrations of a unidirectional composite orthotropic Timoshenko beam based on finite strain have been studied. Using Green-Lagrange strain tensor and comprising all of the nonlinear terms of the tensor and also applying Hamilton's principle, equations of motion and boundary conditions of the beam are obtained. Using separation method in single-harmonic state, time and locative variables are separated from each other and finally, the equations of motion and boundary conditions are gained according to locative variable. To solve the equations, generalized differential quadrature method (GDQM) is applied and then, deflection and cross-section rotation of the beam in linear and nonlinear states are drawn and compared with each other. Also, frequencies of carbon/epoxy and glass/epoxy composite beams for different boundary conditions on the basis of the finite strain are calculated. The calculated frequencies of the nonlinear free vibration of the beam utilizing finite strain assumption for various geometries have been compared to von Karman one.

• 한국기계가공학회지
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• 제14권5호
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• pp.102-106
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• 2015

In this paper, we study the optimal design for improved rotation latch system performance. The factors affecting the Torque generated in the armature were chosen as design variables. Utilizing the vertical matrix, the orthogonal array table was created to predict the results through minimal analysis. To confirm the Torque generation amount, by utilizing the commercial electromagnetic analysis software MAXWELL, finite element analysis was performed. The approximation method and experimental design through the commercial PIDO tool PIAnO for optimal design and calculations were utilized to perform experiments using an optimization method with evolutionary algorithms. Using the approximation model, design factors were determined that can maximize the torque generated in the armature, and the simulation was performed.

• Steel and Composite Structures
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• 제7권2호
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• pp.119-133
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• 2007

Based on stability theory of current rigid steel frames and using the three-column subassemblage model, the governing equations for determining the effective length factor (${\mu}$-factor) of the columns in semirigid composite frames are derived. The effects of the nonlinear moment-rotation characteristics of beam-to-column connections and composite action of slab are considered. Furthermore, using a two-bay three-storey composite frame with semi-rigid connections as an example, the effects of the non-linear moment-rotation characteristics of connections and load value on the ${\mu}$-factor are numerically studied and the ${\mu}$-factors obtained by the proposed method and Baraket-Chen's method are compared with those obtained by the exact finite element method. It was found that the proposed method has good accuracy and can be used in stability analysis of semi-rigid composite frames.

• Journal of Mechanical Science and Technology
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• 제16권4호
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• pp.485-491
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• 2002

The gyroscopes have been used as a suitable inertial instrument for the navigation guidance and attitude controls. The accuracy as very sensitive sensor is limited by the lock-in region (dead band) by the frequency coupling between two counter-propagating waves at low rotation rates. This frequency coupling gives no phase difference and an angular increment is not detected. This problem can be overcome by the mechanical dithering. The purpose of the mechanical dithering is to suppress the dead band, oscillate the monoblock about the rotation axis and add an external rotation rate. This paper presents the theoretical considerations of the mechanical performances of dither on the basis of the loading condition and angular characteristics due to the piezoelement deformation and the validity of theoretical equations are compared through FEM (Finite Element Method) simulations.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2004년도 봄 학술발표회 논문집
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• pp.9-16
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• 2004

This paper deals with the development of computational schemes for the dynamic analysis of flexible and nonlinear multibody systems. Different from the existing method, this paper introduces the quaternion algebra to develop the equation of the conservation of energy. Simultaneously, Rodrigues parameters are used to express the finite rotation for the proposed scheme. The proposed energy scheme is derived such that it provides unconditionally stable conditions for the nonlinear problems. Several examples of dynamic systems are presented which illustrate the efficiency and accuracy of the developed energy schemes.

• Steel and Composite Structures
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• 제3권6호
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• pp.439-450
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• 2003

The finite strip transition matrix technique, a semi analytical method, is employed to obtain the buckling loads and the natural frequencies of symmetric cross-ply laminated composite plates with edges elastically restrained against both translation and rotation. To illustrate the accuracy and the validation of the method several example of cross play laminated composite plates were analyzed. The buckling loads and the frequency parameters are presented and compared with available results in the literature. The convergence study and the excellent agreement with known results show the reliability of the purposed technique.