• Steel and Composite Structures
• /
• v.45 no.1
• /
• pp.1-21
• /
• 2022

In the structural analysis of steel frames, joints are generally considered as rigid or hinged considering their moment transfer ability. However, the first studies conducted with the beginning of the 20th century showed that the joints do not actually fit these two definitions. In reality, a joint behaves between these two extreme points and is called semi-rigid. Including the actual state of the joint in the structural analysis provides significant economic advantages, so the subject is an intense field of study today. However, it does not find enough application area in practice. For this reason, a large-scale literature published from the first studies on the subject to the present has been examined within the scope of the study. Three important points have been identified in order to examine a joint realistically; modelling the load-displacement relationship, performing the structural analysis and how to design. Joint modelling methods were grouped under 7 main headings as analytical, empirical, mechanical, numerical, informational, hybrid and experimental. In addition to the moment-rotation, other important external load effects like axial force, shear and torsion were considered. Various evaluations were made to expand the practical application area of semi-rigid connections by examining analysis methods and design approaches. Dynamic behaviour was also included in the study, and besides column-beam connections, other important connection types such as beam-beam, column-beam-cross, base connection were also examined in this paper.

• International Journal of Aeronautical and Space Sciences
• /
• v.17 no.3
• /
• pp.315-323
• /
• 2016

This paper deals with experimental investigation of active flow control via synthetic jets using an unmanned combat air vehicle (UCAV) planform. Fourteen arrays of synthetic jets, mounted along both leading edges, were fully or partially activated to increase aerodynamic efficiency and reduce pitch-up moment. The measurements were carried out using a six-component external balance, a pressure scanner, and tuft flow visualization. It was observed that aerodynamic efficiency (L/D) and pitching moment were clearly affected by the location of jets. In particular, inboard and outboard actuation could effectively increase L/D. Moreover, inboard actuation showed a reduction in the pitch-up, even more than that generated by the full actuation. These results suggest that inboard actuation not only effectively increases L/D but also reduces the pitch-up using only a few actuators.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 1998.11a
• /
• pp.179-182
• /
• 1998

The structural changes of molecules on the water surface were measured by displacement currents and $\pi$-A isotherm. By using a theoretical equations we calculated charges($\Delta$Q) and dipole moment( $m_{z}$) of saturated fatty acids( $C_{12}$, $C_{14}$, $C_{16}$). The dynamic behavior of saturated fatty acid monolayers at the air/water interface was investigated using a displacement current-measuring technique coupled with the so called Langmuir film technique and also the dipole moment of the acids was determined.as determined.d.

• 제어로봇시스템학회:학술대회논문집
• /
• 2005.06a
• /
• pp.1814-1819
• /
• 2005

This paper describes the development of a Stewart platform-based robot force sensor with distinctive structure of ball joints. The number of ball joints is only a half of the similar style sensors, so it is possible to reduce size and weight of the sensor. The structure of ball joint is described and discussed. Furthermore, we use strain gauges, but not liner voltage differential transformers, as sensing elements, in order to reduce size and weight of the sensor. It is also proposed that beams are replaced with pipes as sensing elements of the sensor. The ball joints and sensing elements with pipes can effectively reduce the error of the sensor. A geometric analysis model is also proposed. The external force and its moment can be measured with this model. Moreover, the performance of this sensor was tested. The test results conducted to evaluate the sensing capability of the sensor is reported and discussed.

• Structural Engineering and Mechanics
• /
• v.10 no.3
• /
• pp.197-209
• /
• 2000

The effects of weight and axial inertia of a beam are taken into account for studying the nonlinear vibration of the Timoshenko beam due to external loads. The combination of Galerkins method and Runge-Kutta method are employed to obtain the dynamic responses of the beam. A concentrated force and a two-axle vehicle traversing on the beam are taken as two examples to investigate the response characteristics of the beam. Results show that the effect of axial inertia of the beam increases the fundamental period of the beam. Further, both the dynamic deflection and the dynamic moment of the beam obtained with including the effect of axial inertia of the beam are greater than those of the beam without including that effect of the beam.

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.15 no.2 s.95
• /
• pp.123-128
• /
• 2005

Forced vibration of a thin circular ring with a concentrated harmonic force is analyzed when the ring is free and has only the in-plane motion. Using the unit doublet function for external force, the governing equation is obtained and is solved by the use of Laplace transform. The exact solutions of displacement components and bending moment are obtained. In order to verify the solutions of analysis, finite element analysis is performed and the results shows good agreement. Then, frequency response curves for displacement and bending moment are obtained. In deriving the governing equations and the solutions, nondimensional parameter of the exciting frequency and the magnitude of exciting force are extracted. As the displacement components are obtained, the remaining bending strain, slope, curvature, shear force, etc. can also be derived. With the results of this work, the responses of a free ring excited on multiple points with different frequencies can also be obtained easily by superposition.

• Ocean Systems Engineering
• /
• v.1 no.1
• /
• pp.1-15
• /
• 2011

Offshore structures are subjected to wind loads, wind generated wave excitations, and current forces. In this paper we focus on the wind generated wave excitations as the main source for the external forces on the structure. The main objective of the paper is to provide a tool for using deck acceleration measurements to predict the value of the force and moment acting on the offshore structure foundation. A change in these values can be used as an indicator of the health of the foundation. Two methods of analysis are used to determine the relationship between the force and moment acting on the foundation and deck acceleration. The first approach uses neural networks while the other uses a Fokker-Planck formulation. The Fokker-Plank approach was used to relate the variance of the excitation to the variance of the deck acceleration. The total virtual mass of the equivalent SDOF of the structure was also determined at different deck masses.

• Journal of Advanced Marine Engineering and Technology
• /
• v.2 no.1
• /
• pp.3-14
• /
• 1978

The authors have developed a calculating method of propeller shaft alignment by the finite element method. The propeller shaft is divided into finite elements which can be treated as uniform section bars. For each element, the nodal point equation is derived from the stiffness matrix, the external force vector and the section force vector. Then the overall nodal point equation is derived from the element nodal point equation. The deflection, offset, bending moment and shearing force of each nodal point are calculated from the overall nodal point equation by the digital computer. Reactions and deflections of supporting points of straight shaft are calculated and also the reaction influence number is derived. With the reaction influence number the optimum alignment condition that satisfies all conditions is calculated by the simplex method of linear programming. All results of calculation are compared with those of Det norske Veritas, which has developed a computor program based on the three-moment theorem of the strength of materials. The authors finite element method has shown good results and will be used effectively to design the propeller shaft alignment.

• Steel and Composite Structures
• /
• v.33 no.2
• /
• pp.225-243
• /
• 2019

Cold-formed steel (CFS) sections when used as primary load carrying members often require additional strengthening for retrofitting purposes. In some cases, it is also necessary to reduce deflections in order to satisfy serviceability requirements. The introduction of angle sections, screwed to the webs so as to act as external stiffeners, has the potential to both increase flexural strength as well as reduce deflections. This paper presents the results of ten four-point bending tests, on built-up CFS sections, both open and closed, with different stiffening arrangements. In the laboratory tests, the stiffening arrangements increased the moment capacity and stiffness of the CFS beams by up to 85% and 100% respectively. The increase in moment capacity was more evident for the open sections, while that reduction in deflection was largest for the closed sections.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.24 no.9 s.180
• /
• pp.2259-2265
• /
• 2000

A dynamic modeling of a rotating pretwist blade which interacts with the fluid is proposed in this study. The hybrid deformation variable modeling method is employed to derive the equations of motion. The external force and moment induced by the fluid (with fixed configurations of the blade) are obtained by fluid flow analysis and tabulated in a database. This database is efficiently utilized to save the computational effort to calculate the dynamic response of the blade. The numerical results show that the fluid affects the transient response as well as frequency characteristics of the system.