• Structural Engineering and Mechanics
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• v.47 no.6
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• pp.881-898
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• 2013

This paper describes analytical investigation into a new dual function system including a couple of shear links which are connected in series using chevron bracing capable to correlate its performance with magnitude of earthquakes. In this proposed system, called Chevron Knee-Vertical Link Beam braced system (CK-VLB), the inherent hysteretic damping of vertical link beam placed above chevron bracing is exclusively utilized to dissipate the energy of moderate earthquakes through web plastic shear distortion while the rest of the structural elements are in elastic range. Under strong earthquakes, plastic deformation of VLB will be halted via restraining it by Stopper Device (SD) and further imposed displacement subsequently causes yielding of the knee elements located at the bottom of chevron bracing to significantly increase the energy dissipation capacity level. In this paper first by studying the knee yielding mode, a suitable shape and angle for diagonal-knee bracing is proposed. Then finite elements models are developed. Monotonic and cyclic analyses have been conducted to compare dissipation capacities on three individual models of passive systems (CK-VLB, knee braced system and SPS system) by General-purpose finite element program ABAQUS in which a bilinear kinematic hardening model is incorporated to trace the material nonlinearity. Also quasi-static cyclic loading based on the guidelines presented in ATC-24 has been imposed to different models of CK-VLB with changing of vertical link beam section in order to find prime effectiveness on structural frames. Results show that CK-VLB system exhibits stable behavior and is capable of dissipating a significant amount of energy in two separate levels of lateral forces due to different probable earthquakes.

• The Journal of the Convergence on Culture Technology
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• v.5 no.2
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• pp.381-388
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• 2019

In this paper, we propose a new wireless transport network, which is named as Mobile Xhaul Network(MXN), that is enable to bring cost efficiency of fronthaul, midhaul and backhaul and to make easy installation of 5G Radio Access Network(RAN). For this purpose, we design XDU discovery and xhaul link setup mechanism with MXN architecture and operational procedure. Especially, in this paper, we propose various types of beam discovery mechanisms for mmWave based radio access on XDU and evaluate proposed schemes. The Simulation result shows that threshold based scheme and information based scheme have less than about 50% beam discovery latency compared to full search scheme.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39C no.12
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• pp.1327-1337
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• 2014

In cellular communication systems employing millimeter wave (mmWave) bands for a link, a large amount of training time and network resources will be required to find a serving BS with the best transmit and receive (Tx-Rx) beam pair if downlink control signals are used. In this paper, a tracking technique for OFDM-based cellular communication systems with a mmWave link, where an analog beamforer is used at the mobile station (MS) and a digital beamformer is used at the BS, is proposed using an uplink signal. A technique to select a serving BS with the best beam pair is described using the uplink preamble sequence based on Zadoff-Chu sequence and a metrics which can be used to identify parameters such as beam ID (BID), MS ID (MID), and direction-of-arrival (DoA). The effectiveness of the proposed technique is verified via simulation with the spatial channel model (SCM) for a moving MS in mmWave cellular systems.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.26 no.7
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• pp.865-874
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• 2016

This research is concerned with the experimental investigation on the vibrations of a flexible two-link system for verifying the theoretical result from simplified equations of motion for the system along with the kinematical synthesis are proposed to simulate the elastic vibrations of a previous study. The structure consists of flexible two-links; The link 2 is attached to the end of the link 1. The link 1 is made of composite fiber reinforced polymer and the link 2 is an aluminum beam. In order to verify the theoretical result, a flexible two-link system operated by the AC and RC servo motors was constructed. Experimental results show that the dynamic modeling approach and the kinematical synthesis proposed in this paper are effective.

• 제어로봇시스템학회:학술대회논문집
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• 1993.10a
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• pp.8-13
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• 1993

This paper presents deterministic and adaptive control laws for two-link flexible arm. The flexible arm has considerable structural flexibility. Because of its flexbility, dynamic equations are very complex and difficult to get, dynamic equations for two-link flexible arm are derived from Bernoulli-Euler beam theory and Lagrangian equation. Using the fact that matrix is skew symmetric, controllers which have a simplified structure with less computational burden are proposed by using Lyapunov stability theory.

• Steel and Composite Structures
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• v.35 no.3
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• pp.305-325
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• 2020

Beams of steel frame-tube structures (SFTSs) typically have span-to-depth ratios of less than five. This makes a flexural beam unsuitable for such an application because the plastic hinges at the beam-ends cannot be adequately developed. This leads to lower ductility and energy dissipation capacities of SFTSs. To address this, SFTSs with bolted web-connected replaceable shear links (SFTS-BWSLs) are proposed. In this structural system, a web-connected replaceable shear link with a back-to-back double channel section is placed at the mid-length of the deep beam to act as a ductile fuse. This allows energy from earthquakes to be dissipated through link shear deformation. SFTS and SFTS-BWSL buildings were examined in this study. Several sub-structures were selected from each designed building and finite element models were established to study their respective hysteretic performance. The seismic behavior of each designed building was observed through static and dynamic analyses. The results indicate that the SFTS-BWSL and SFTS have similar initial lateral stiffness and shear leg properties. The SFTS-BWSL had lower strength, but higher ductility and energy dissipation capacities. Compared to the SFTS, the SFTS-BWSL had lower interstory drift, base shear force, and story shear force during earthquakes. This design approach could concentrate plasticity on the shear link while maintaining the residual interstory drift at less than 0.5%. The SFTS-BWSL is a reliable resistant system that can be repaired by replacing shear links damaged due to earthquakes.

• Transactions of the Korean Society of Mechanical Engineers
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• v.19 no.6
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• pp.1371-1381
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• 1995

A novel hybrid control scheme to actively control the endpoint position of a very flexible single-link manipulator is proposed. The control scheme consists of a motor mounted at the beam hub and a piezofilm actuator bonded to the surface of the flexible link. The control torque of the motor to produce a desired motion is firstly determined by employing the sliding mode control theory on the equation of motion of the rigid link having the same mass as that of the proposed flexible link. The torque is then applied to the flexible manipulator in order to activate the commanded motion. During the motion, undesirable oscillation is actively suppressed by applying a feedback control voltage to the piezofilm actuator. Consequently, the imposed desired position is accomplished. In order to demonstrate high control performances accrued from the proposed method, computer simulations are undertaken by treating both regulating and tracking control problems.

• Steel and Composite Structures
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• v.42 no.6
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• pp.827-841
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• 2022

The rotation capacities of the plastic hinges located at beam-ends are significantly reduced in traditional steel framed-tube structures (SFTSs) because of the small span-to-depth ratios of the deep beams, leading to the low ductility and energy dissipation capacities of the SFTSs. High-strength steel framed-tube structures with replaceable shear links (HSSFTS-RSLs) are proposed to address this issue. A replaceable shear link is located at the mid-span of a deep spandrel beam to act as a ductile fuse to dissipate the seismic energy in HSSFTS-RSLs. A 2/3-scaled HSSFTS-RSL specimen with a shear link fabricated of high-strength low-alloy Q355 structural steel was created, and a cyclic loading test was performed to study the hysteresis behaviors of this specimen. The test results were compared to the specimens with soft steel shear links in previous studies to investigate the feasibility of using high-strength low-alloy steel for shear links in HSSFTS-RSLs. The effects of link web stiffener spaces on the cyclic performance of the HSSFTS-RSLs with Q355 steel shear links were investigated based on the nonlinear numerical analysis. The test results indicate that the specimen with a Q355 steel shear link exhibited a reliable and stable seismic performance. If the maximum interstory drift of HSSFTS-RSL is designed lower than 2% under earthquakes, the HSSFTS-RSLs with Q355 steel shear links can have similar seismic performance to the structures with soft steel shear links, even though these shear links have similar shear and flexural strength. For the Q355 steel shear links with web height-to-thickness ratios higher than 30.7 in HSSFTS-RSLs, it is suggested that the maximum intermediate web stiffener space is decreased by 15% from the allowable space for the shear link in AISC341-16 due to the analytical results.

• Structural Engineering and Mechanics
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• v.64 no.3
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• pp.301-310
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• 2017

For further development of passive control systems to dissipate larger seismic energy and prevent the structures from earthquake losses, this paper proposes an innovative two-level control system to improve behavior of chevron braced steel frames. Combining two Knee Braces, KB, and a Vertical Link Beam, VLB, in a chevron braced frame, this system can reliably sustain main shock and aftershocks in steel structures. The performance of this two-level system is examined through a finite element analysis and quasi-static cyclic loading test. The cyclic performances of VLB and KBs alone in chevron braced frames are compared with that of the presented two-level control system. The results show appropriate performance of the proposed system in terms of ductility and energy dissipation in two different excitation levels. The maximum load capacity of the presented system is about 30% and 17% higher than those of the chevron braced frames with KB and VLB alone, respectively. In addition, the maximum energy dissipation of the proposed system is about 78% and 150% higher than those of chevron braced frames with VLB and KB respectively under two separate levels of lateral forces caused by different probable seismic excitations. Finally, high performance under different earthquake levels with competitive cost and quick installation work for the control system can be found as main advantages of the presented system.

• Journal of Advanced Marine Engineering and Technology
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• v.23 no.2
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• pp.227-235
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• 1999

In this paper a vibration control fo a one-link flexible beam is considered. At first a state-space model for a flexible beam is derived by using the assumed-modes approach. Based on this model the transfer function between the applied torque and the tip deflection fo the beam is presented because it is convenient to apply our method. In general there exist some control difference due to flexibility of the beam so we adop a forward-passive controller to reduce these phenomena. And a complex dual-input describing function compensator is used to control the tip deflection. The stabiltiy and the performance of the closed-loop system are analyzed. Finally the validity of the derived model and the effectiveness of proposed controller are confirmed throuth simula-tions and experiments.