• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 2005년도 추계 학술발표회 제17권2호
• /
• pp.339-342
• /
• 2005

This paper presents flexural test results of concrete beams reinforced with GFRP and conventional steel reinforcement for comparison. The beams were tested under static loading to investigate the effects of reinforcement ratio and compressive ,strength of concrete on cracking, deflection, ultimate capacity and mode of failure, This study attempts to establish a theoretical basis for the development of simple and rational design guideline. Test results show that ultimate capacity increases as the reinforcement ratio and concrete strength increase. The ultimate capacity increased up to $8\%-25\%$ by using high strength concrete. The deflection at maximum load of GFRP reinforced beams was about three times that of steel reinforced beams. For GFRP-reinforced beams, the ACI code 440 design method resulted in conservative flexural strength -estimates.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2014년도 추계학술대회 논문집
• /
• pp.916-921
• /
• 2014

In this paper, an improved small-scaled blade prototype was designed with the flap-driving mechanism classified as an active vibration reduction method, in order to reduce vibratory load in the helicopter. In detail, the previous Active Trailing-Edge Flap based on piezoelectric actuator, called SNUF(Seoul National University Flap), failed to achieve the target value (${\pm}4^{\circ}$) of the flap deflection angle. Therefore, the flap-driving mechanism design was improved, and a new piezoactuator was selected to accomplish the target value of the flap deflection angle in both static and rotating situations.

• Coupled systems mechanics
• /
• 제4권3호
• /
• pp.251-262
• /
• 2015

The current paper aims at investigating the nonlinear dynamical behaviour of an electrically actuated microcantilever. The microcantilever is excited by a combination of AC and DC voltages. The nonlinear equation of motion of the microcantilever is obtained by means of force and moment balances. A high-dimensional Galerkin scheme is then applied to reduce the equation of motion to a discrete model. A numerical technique, based on the pseudo-arclength continuation method, is used to solve the discretized model. The electrostatic deflection of the microcantilever and static pull-in instabilities, due to the DC voltage, are analyzed by plotting the so-called DC voltage-deflection curves. At the simultaneous presence of the DC and AC voltages, the nonlinear dynamical behaviour of the microcantilever is analyzed by plotting frequency-response and force-response curves.

• 한국소성가공학회:학술대회논문집
• /
• 한국소성가공학회 1992년도 춘계학술대회 논문집 92
• /
• pp.115-130
• /
• 1992

The analysis of thermoplastic automotive bumpers needs not only characterizations of the thermomechanical properties of thermoplastic materials but also the finite element method which can solve the problems with a large deflection, an elastic-inelastic deformation, and a change of a contact state. This paper describes the modeling techniques in the finite element analysis in order to get a good prediction of thermoplastic bumper behaviors. Simplification effects of a complex geometry of thermoplastic bumpers are studied by comparing the results from static loading tests and the finite element analysis.

• Advances in Computational Design
• /
• 제3권2호
• /
• pp.165-190
• /
• 2018

In this article, the static behavior of non-prismatic sandwich beams composed of functionally graded (FG) materials is investigated for the first time. Two types of beams in which the variation of elastic modulus follows a power-law form are studied. The principle of minimum total potential energy is applied along with the Ritz method to derive and solve the governing equations. Considering conventional boundary conditions, Chebyshev polynomials of the first kind are used as auxiliary shape functions. The formulation is developed within the framework of well-known Timoshenko and Reddy beam theories (TBT, RBT). Since the beams are simultaneously tapered and functionally graded, bending and shear stress pushover curves are presented to get a profound insight into the variation of stresses along the beam. The proposed formulations and solution scheme are verified through benchmark problems. In this context, excellent agreement is observed. Numerical results are included considering beams with various cross sectional types to inspect the effects of taper ratio and gradient index on deflections and stresses. It is observed that the boundary conditions, taper ratio, gradient index value and core to the thickness ratio significantly influence the stress and deflection responses.

• Structural Engineering and Mechanics
• /
• 제32권3호
• /
• pp.399-406
• /
• 2009

A three-dimensional panel system, which was offered as a new method for construction in Jordan using relatively high strength modular panels for walls and ceilings, is investigated in this paper. The panel consists of two steel meshes on both sides of an expanded polystyrene core and connected together with a truss wire to provide a 3D system. The top face of the ceiling panel was pored with regular concrete mix, while the bottom face and both faces of the wall panels were cast by shotcreting (dry process). To investigate the structural performance of this system, an extensive experimental testing program for ceiling and wall panels subjected to static and dynamic loadings was conducted. The load-deflection curves were obtained for beam and shear wall elements and wall elements under transverse and axial loads, respectively. Static and dynamic analyses were conducted, and the performance of the proposed structural system was evaluated and compared with a typical three dimensional reinforced concrete frame system for buildings of the same floor areas and number of floors. Compressive strength capacity of a ceiling panel is determined for gravity loads, while flexural capacity is determined under the effect of wind and seismic loading. It was found that, the strength and serviceability requirements could be easily satisfied for buildings constructed using the three-dimensional panel system. The 3D panel system is superior to that of conventional frame system in its dynamic performance, due to its high stiffness to mass ratio.

• 한국정밀공학회지
• /
• 제22권3호
• /
• pp.146-153
• /
• 2005

In this paper, a multi-step optimization using genetic algorithm with variable penalty function is introduced to the structural design optimization of a grinding machine. The design problem, in this study, is to find out the optimum configuration and dimensions of structural members which minimize the static compliance, the dynamic compliance, and the weight of the machine structure simultaneously under several design constraints such as dimensional constraints, maximum deflection limit, safety criterion, and maximum vibration amplitude limit. The first step is shape optimization, in which the best structural configuration is found by getting rid of structural members that have no contributions to the design objectives from the given initial design configuration. The second and third steps are sizing optimization. The second design step gives a set of good design solutions having higher fitness for lightweight and minimum static compliance. Finally the best solution, which has minimum dynamic compliance and weight, is extracted from the good solution set. The proposed design optimization method was successfully applied to the structural design optimization of a grinding machine. After optimization, both static and dynamic compliances are reduced more than 58.4% compared with the initial design, which was designed empirically by experienced engineers. Moreover the weight of the optimized structure are also slightly reduced than before.

• Steel and Composite Structures
• /
• 제24권4호
• /
• pp.425-439
• /
• 2017

As a thin-walled structure, local joint flexibility (LJF) in a tubular structure is prominent, and it may produce significant effect on the static performance for the overall structure. This study presents a simplified analytical model to analyze the static behavior for a steel tubular structure with LJF. The presented model simplifies a tubular structure into a frame model consisted of beam elements with considering the LJFs at the connections between any two elements. Theoretical equations of the simplified analytical model are deduced. Through comparison with 3-D finite element results of two typical planar tubular structures consisted of T- and Y-joints respectively, the presented method is proved to be accurate. Furthermore, the effect of LJF on the overall performance of the two tubular structures (including the deflection and the internal forces) is also investigated, and it is found from analyses of internal forces and deformation that a rigid connection assumption in a frame model by using beam elements in finite element analysis can provide unsafe and inaccurate estimation.

• Journal of Mechanical Science and Technology
• /
• 제19권4호
• /
• pp.947-957
• /
• 2005

In this study a simple model is developed that predicts impact damage in a composite laminate avoiding the need of the time-consuming dynamic finite element method (FEM). The analytical model uses a non-linear approximation method (Rayleigh-Ritz) and the large deflection plate theory to predict the number of failed plies and damage area in a quasi-isotropic composite circular plate (axisymmetric problem) due to a point impact load at its centre. It is assumed that the deformation due to a static transverse load is similar to that oc curred in a low velocity impact. It is found that the model, despite its simplicity, is in good agreement with FEM predictions and experimental data for the deflection of the composite plate and gives a good estimate of the number of failed plies due to fibre breakage. The predicted damage zone could be used with a fracture mechanics model developed by the second investigator and co-workers to calculate the compression after impact strength of such laminates. This approach could save significant running time when compared to FEM solutions.

• 한국지반공학회논문집
• /
• 제34권7호
• /
• pp.51-58
• /
• 2018

본 연구에서는 하중 조건에 따른 지반-말뚝 상호작용 시스템의 거동 차이를 분석하기 위해 일련의 원심모형 실험을 수행하였다. 정적 하중 조건의 경우, 말뚝 직경의 50% 수준까지 변위제어를 통해 하중을 재하하였으며, 지진 하중 조건의 경우 0.1g~0.4g 수준으로 1Hz 정현파를 가진하였다. 실험 결과로부터 얻은 정적 및 동적 p-y 곡선을 API p-y 곡선과 비교한 결과, API p-y 곡선과 정적 하중조건에서의 실험 p-y 곡선은 최대 지반반력 값이 20% 이내의 오차를 보인 반면, 동적 하중 조건에서의 실험 p-y 곡선과는 최대 지반반력 값이 5배 이상 차이가 발생하였다. 이는 등가정적 해석에서 기존 API p-y 곡선을 적용할 경우 비선형 영역에서 지반 반력을 크게 과소평가하며 보수적 설계를 야기할 수 있음을 의미한다.