• Steel and Composite Structures
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• v.18 no.3
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• pp.757-773
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• 2015

This work attempts to implement multiple regression analysis (MRA) for modeling and predicting the shear buckling strength of a steel beam with corrugated web. It was recognized from theoretical and experimental results that the shear buckling strength of a steel beam with corrugated web is complicated and affected by several parameters. A model that predicts the shear strength of a steel beam with corrugated web with reasonable accuracy was sought. To that end, a total of 93 experimental data points were collected from different sources. Then mathematical models for the key response parameter (shear buckling strength of a steel beam with corrugated web) were established via MRA in terms of different input geometric, loading and materials parameters. Results indicate that, with a minimal processing of data, MRA could accurately predict the shear buckling strength of a steel beam with corrugated web within a 95% confidence interval, having an $R^2$ value of 0.93 and passing the F- and t-tests.

• Structural Engineering and Mechanics
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• v.87 no.6
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• pp.529-540
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• 2023

A novel laminated-hybrid-composite-beam (LHCB) of glass-epoxy infused with flyash and graphene is constructed for this study. The conventional mixture-rule and constitutive-relationship are modified to incorporate filler and lamina orientation. Eringen's non-local-theory is used to include the filler effect. Hamilton's principle based on fifth-order-layer-wise-shear-deformation-theory is applied to formulate the equation of motion. The analogous shear-spring-models for LHCB with multiple-cracks are employed in finite-element-analysis (FEA). Modal-experimentations are conducted (B&K-analyser) and the findings are compared with theoretical and FEA results. In terms of dimensionless relative-natural-frequencies (RNF), the dynamic-response in cantilevered support is investigated for various relative-crack-severities (RCSs) and relative-crack-positions (RCPs). The increase of RCS increases local-flexibility in LHCB thus reductions in RNFs are observed. RCP is found to play an important role, cracks present near the end-support cause an abrupt drop in RNFs. Further, multiple cracks are observed to enhance the nonlinearity of LHCB strength. Introduction of the first to third crack in an intact LHCB results drop of RNFs by 8%, 10%, and 11.5% correspondingly. Also, it is demonstrated that the RNF varies because of the lamina-orientation, and filler addition. For 0° lamina-orientation the RNF is maximum. Similarly, it is studied that the addition of graphene reduces weight and increases the stiffness of LHCB in contrast to the addition of flyash. Additionally, the response of LHCB to moving mass is accessed by appropriately modifying the numerical programs, and it is noted that the successive introduction of the first to ninth crack results in an approximately 40% to 120% increase in the dynamic-amplitude-ratio.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.25 no.8
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• pp.864-871
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• 2014

In this paper, we propose an optimization method for obtaining beam curve which minimize the phase errors of Rotman lens. This method is based on idea that 3 path lengths from a beam port through equal phase points, which consist of the center point of array antenna and two points placed symmetrically or asymmetrically along array antenna, to the corresponding phase front are equal. According to this method, the optimal locations of beam ports can be obtained directly by finding each equal phase point set on array antenna to minimize the phase errors for each beam direction. Simulation results show that the proposed method is the most optimal and effective method for determining the beam curve of Rotman lens with low phase errors.

• The Journal of Korean Society for Radiation Therapy
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• v.7 no.1
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• pp.15-31
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• 1995

The radiosurgery treatment is one time, non surgical approach to the treatment of patients with intracranial disorders whose conditions would be difficult or dangerous to treat with conventional sugical procedures. The LINAC based radiosurgery is based on the combination of multiple isocentric arc irradiation with small fields centered in the stereotactic target. The absorption of the beam in a tissue equivalent medium, such as water, as well as the uniformity, or profile, of the beam must be precisely documented. The beam characteristics and dosimetric measurememts of the 6MV X-ray beam from a ML-6M linear accelerator are examined. The percent depth dose (PDD) and beam profile (including flatness, symmetry and penumbra) is calibrated with the radiosurgery cone in water phantom. The cone is made of lead which size is from $10{\times}10mm{\phi}$ to $30{\times}30mm{\phi}$ All of these dosimetric measurements sufficiently characterized the beam to permit safe clinical use.

• Journal of the Architectural Institute of Korea Structure & Construction
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• v.35 no.4
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• pp.135-146
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• 2019

Deep beam has high section modules compared with shallow beam of the same weight. However, deep beam has low rotational capacity and high possibility of brittle failure so it is not possible to apply deep beams with a long span to intermediate moment frames, which should exhibit a ductility of 0.02rad of a story drift angle of steel moment frames. Accordingly, KBC and AISC limit the beam depth for intermediate and special moment frame to 750mm and 920mm respectively. The purpose of this paper is to improve the seismic performance of intermediate moment frame with 1200mm depth beam. In order to enhance vulnerability of plastic deformation capacity of deeper beam, Multi-Reduced Taper Beam(MRTB) shape that thickness of beam flange is reinforced and at the same time some part of the beam flange width is weakened are proposed. Based on concept of multiple plastic hinge, MRTB is intended to satisfy the rotation requirement for intermediate moment frame by dividing total story drift into each hinge and to prevent the collapse of the main members by inducing local buckling and fracture at the plastic hinge location far away from connection. The seismic performance of MRTB is evaluated by cyclic load test with conventional connections type WUF-W, RBS and Haunch. Some of the proposed MRTB connection satisfies connection requirements for intermediate moment frame and shows improved the seismic performance compared to conventional connections.

• Journal of the Korean Society for Nondestructive Testing
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• v.28 no.6
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• pp.531-537
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• 2008

One of the fundamental features of time reversal acoustic (TRA) techniques is the ability to focus the propagating ultrasonic beam to a specific point within the test material. Therefore, it is important to understand the focusing properties of a TR device in many applications including nondestructive testing. In this paper, we employ an analytical scheme for the analysis of TR beam focusing in a homogeneous medium. More specifically, a nonparaxial multi-Gaussian beam (NMGB) model is used to simulate the focusing behavior of array transducers composed of multiple rectangular elements. The NMGB model is found to generate accurate beam fields beyond the nonparaxial region. Two different simulation cases are considered here for the focal points specified on and off from the central axis of the array transducer. The simulation results show that the focal spot size increases with increasing focal length and focal angle. Furthermore, the maximum velocity amplitude does not always coincide with the specified focal point. Simulation results for the off-axis focusing cases do demonstrate the accurate steering capability of the TR focusing.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2002.10a
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• pp.25-32
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• 2002

Free vibration analysis of radialiy multi-delaminated beams with through-the-width multi-delamination is performed in the present study. The multiple delaminations are considered to be in a radial manner through the thickness from the top surface of the beam. The natural frequencies of the radially multi-delaminated beams are calculated from a new algorithm that is based on the single compound delaminated beam model. That is, beams with radial multi-delaminations are regarded as the sum of a single compound delamlnated beam that is the single sub-delaminated beam from the top surface of global beam. Each result of frequency equation for the single delaminated beam with unknown boundary conditions obtained through continuity conditions Is updated to the next one, With these sequential operations, the final frequency equation of radially multi-delaminated beams is obtained for both ends boundary conditions of global beam. The numerical results carried out for the beams are compared with those of some references to give the reliance on the proposed algorithm and to investigate the effects of the shape, number, size of multi-delaminations on the natural frequency. Compared with the other previously presented model, the proposed algorithm is more flexible in modeling and formulating as the total array size of frequency equation is always four by four. Therefore, the proposed algorithm will reduce the effort of user in formulating the physical model to the numerical model.

• Ocean Systems Engineering
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• v.13 no.2
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• pp.195-224
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• 2023

This paper proposes a method for the acoustic imaging wherein the traditional requirement of the relative movement between the transmitter and target is overcome. This is facilitated through the beamforming acoustic array in the transmitter, in which the target is illuminated by the array at various azimuth and elevation angles without the physical movement of the acoustic array. The concept of beam steering of the acoustic array facilitates the formation of the beam at desired angular positions of azimuth and elevation angles. This paper substantiates that the combination of illumination of the target from different azimuth and elevation angles with respect to the transmitter (through the beam steering of beam forming acoustic array) and the beam steering at multiple frequencies (through SF) results in enhanced reconstruction of images of the target in the underwater scenario. This paper also demonstrates the possibility of reconstruction of the image of a target in underwater without invoking the traditional algorithms of Digital Image Processing (DIP). This paper comprehensively and succinctly presents all the empirical formulae required for modelling the acoustic medium and the target to facilitate the reader with a comprehensive summary document incorporating the various parameters of multi-disciplinary nature.

• Earthquakes and Structures
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• v.23 no.1
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• pp.23-34
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• 2022

This paper presents experimental studies on reinforced concrete moment resisting frames that have engineered cementitious composite (ECC) in plastic hinge length (PHL) of beam/column members and beam-column joints. A two-story frame structure reduced by a 1:3 scale was further tested through a shake-table (seismic simulator) using multiple levels of simulated earthquake motions. One model conformed to all the ACI-318 requirements for IMRF, whereas the second model used lower-strength concrete in the beam/column members outside PHL. The acceleration time history of the 1994 Northridge earthquake was selected and scaled to multiple levels for shake-table testing. This study reports the observed damage mechanism, lateral strength-displacement capacity curve, and the computed response parameters for each model. The tests verified that nonlinearity remained confined to beam/column ends, i.e., member joint interface. Calculated response modification factors were 11.6 and 9.6 for the code-conforming and concrete strength deficient models. Results show that the RC-ECC frame's performance in design-based and maximum considered earthquakes; without exceeding maximum permissible drift under design-base earthquake motions and not triggering any unstable mode of damage/failure under maximum considered earthquakes. This research also indicates that the introduction of ECC in PHL of the beam/column members' detailing may be relaxed for the IMRF structures.

• Transactions of the Korean Society of Mechanical Engineers
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• v.15 no.6
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• pp.1897-1907
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• 1991

An analysis is presented for the primary resonance of a clamped-hinged beam, which occurs when the frequency of excitation is near one of the natural frequencies, .omega.$_{n}$. Three mode interactions, .omega.$_{2}$=3.omega.$_{1}$, and .omega.$_{3}$=.omega.$_{1}$+2.omega.$_{2}$, are considered and their influence on the response is studied. The case of two mode interaction, .omega.$_{2}$=3.omega.$_{1}$, is also considered in order to compare it with the case of three mode interactions. The straight beam experiencing mid-plane stretching is governed by a nonlinear partial differential equation. By using Galerkin's method the governing equation is reduced to a system of nonautonomous nonlinear ordinary differential equations. The method of multiple scales is applied to obtain steady-state responses of the system. Results of numerical investions show that there exists no significant difference between both modal interactions.