• Steel and Composite Structures
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• v.24 no.5
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• pp.561-568
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• 2017

Steel frames are widely used in steel structures. Exiting steel structures may be needed to strengthen for various reasons. Carbon Fiber Reinforced Polymers (CFRP) is one of the materials that are used to strengthen steel structures. Most studies on strengthening steel structures have been done on beams and steel columns. No independent study, to the researcher's knowledge, has studied the effect of CFRP strengthening on steel frames. This study explored the use of CFRP composite on retrofitting square hollow section (SHS) steel frames, using numerical investigations. Ten Finite Element (FE) models, which were strengthened with CFRP sheets, were analyzed under different coverage length, number of layers, and location of CFRP composite. One FE model without strengthening was analyzed as a control FE model to determine the increase of the ultimate load in the strengthened steel frames. ANSYS software was used to analyze the SHS steel frames. The results showed that the coverage length and the number of layers of CFRP composite have a significant effect on increasing the ultimate load of the SHS steel frames. The results also showed that the location of CFRP composite had no similar effect on increasing the ultimate load and the amount of mid span deflection of the SHS steel frames.

• Journal of KIISE:Software and Applications
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• v.27 no.5
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• pp.510-520
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• 2000

For content-based video indexing and retrieval, it is necessary to segment video data into video shots and then select key frames or representative frames for each shot. However, it is very difficult to select key frames automatically because the task of selecting meaningful frames is quite subjective. In this paper, we propose a new approach in selecting key frames based on visual contents such as region information and their temporal variations in the shot. First of all, we classify video shots into panning shots, zooming shots, tilting shots or no camera motion shots by detecting camera motion information in video shots. Then, in each category, we apply appropriate fuzzy rules to select key frames based on meaningful content in frame. Finally, we control the number of key frames in the selection process by adjusting the degree of detail in representing video shots.

• Earthquakes and Structures
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• v.13 no.5
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• pp.443-454
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• 2017

When eccentrically braced steel frames (EBFs) are in the desired failure mode, links yield at each layer and column bases appear plastically hinged. Traditional design methods cannot accurately predict the inelastic behavior of structures owing to the use of capacity-based design theory. This paper proposes the use of performance-based seismic design (PBSD) method for planning eccentrically braced frames. PBSD can predict and control inelastic deformation of structures by target drift and failure mode. In buildings designed via this process, all links dissipate energy in the rare event of an earthquake, while other members remain in elastic state, and as the story drift is uniform along the structure height, weak layers will be avoided. In this condition, eccentrically braced frames may be more easily rehabilitated after the effects of an earthquake. The effectiveness of the proposed method is illustrated through a sample case study of ten-story K-type EBFs and Y- type EBFs buildings, and is validated by pushover analysis and dynamic analysis. The ultimate state of frames designed by the proposed method will fail in the desired failure mode. That is, inelastic deformation of structure mainly occurs in links; each layer of links involved dissipates energy, and weak layers do not exist in the structure. The PBSD method can provide a reference for structural design of eccentrically braced steel frames.

• Earthquakes and Structures
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• v.15 no.3
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• pp.319-334
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• 2018

In this paper, an analytical study was carried out to propose an optimum base-isolated system for the design of steel structures equipped with lead rubber bearings (LRB). For this, 5 and 10-storey steel moment resisting frames (MRFs) were designed as Special Moment Frame (SMF). These two-dimensional and three-bay frames equipped with a set of isolation systems within a predefined range that minimizes the response of the base-isolated frames subjected to a series of earthquakes. In the design of LRB, two main parameters, namely, isolation period (T) and the ratio of strength to weight (Q/W) supported by isolators were considered as 2.25, 2.5, 2.75 and 3 s, 0.05, 0.10 and 0.15, respectively. The Force-deformation behavior of the isolators was modelled by the bi-linear behavior which could reflect the nonlinear characteristics of the lead-plug bearings. The base-isolated frames were modelled using a finite element program and those performances were evaluated in the light of the nonlinear time history analyses by six natural accelerograms compatible with seismic hazard levels of 2% probability of exceedance in 50 years. The performance of the isolated frames was assessed in terms of roof displacement, relative displacement, interstorey drift, absolute acceleration, base shear and hysteretic curve.

• Structural Engineering and Mechanics
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• v.76 no.3
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• pp.421-433
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• 2020

Masonry infills are normally considered as non-structural elements in design practice, therefore, the interaction between the bounding frame and the strength contribution of masonry infills is commonly ignored in the seismic analysis work of the RC frames. However, a number of typical RC frames with irregular distributed masonry infills have suffered from undesirable weak-story failure in major earthquakes, which indicates that ignoring the influence of masonry infills may cause great seismic collapse risk of RC frames. This paper presented the investigation on the risk of seismic collapse of RC frames with irregularly distributed masonry infills through a large number of nonlinear time history analyses (NTHAs). Based on the results of NTHAs, seismic fragility curves were developed for RC frames with various distribution patterns of masonry infills. It was found that the existence of masonry infills generally reduces the collapse risk of the RC frames under both frequent happened and very strong earthquakes, however, the severe irregular distribution of masonry infills, such as open ground story scenario, results in great risk of forming a weak story failure. The strong-column weak-beam (SCWB) ratio has been widely adopted in major seismic design codes to control the potential of weak story failures, where a SCWB ratio value about 1.2 is generally accepted as the lower limit. In this study, the effect of SCWB ratio on inter-story drift distribution was also parametrically investigated. It showed that improving the SCWB ratio of the RC frames with irregularly distributed masonry infills can reduce inter-story drift concentration index under earthquakes, therefore, prevent weak story failures. To achieve the same drift concentration index limit of the bare RC frame with SCWB ratio of about 1.2, which is specified in ACI318-14, the SCWB ratio of masonry-infilled RC frames should be no less than 1.5. For the open ground story scenario, this value can be as high as 1.8.

• Journal of KIISE:Information Networking
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• v.31 no.1
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• pp.1-10
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• 2004

This study discusses Application-layer FEC using erasure codes. Because of the simple decoding process, erasure codes are used effectively in Application-layer FEC to deal with Packet-level errors. The large number of parity packets makes the loss rate to be small, but causes the network congestion to be worse. Thus, a redundancy control algorithm that can adjust the number of parity packets depending on network conditions is necessary. In addition, it is natural that high-priority frames such as I frames should produce more parity packets than low-priority frames such as P and B frames. In this paper, we propose a redundancy control algorithm that can adjust the amount of redundancy depending on the network conditions and depending on data priority, and test the performance in simple links and congestion links.

• Journal of IKEEE
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• v.2 no.1 s.2
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• pp.114-121
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• 1998

This paper proposed a collision avoidance scheme to improve the network performance and priority control scheme to support real-time ATM applications in CIF(Cells in Frames), which carries ATM cells over existing Ethernet interfaces. The proposed scheme has optimized for the two nodes Ethernet, that is a typical CIF network, and doesn't require any hardware modification of existing Ethernet interface card. The collision avoidance scheme gives fair access opprtunities with minimized contention to the nodes by assigning different inter-frame gap to each element of CIF network. The priority control scheme guarantees preemptive transmission of real-time frames to the medium by exchanging queuing status information between two nodes. Therefore in this paper it is shown that CIF network which has both the collision avoidance scheme of MAC layer and the priority control scheme of CIF layer has a improved network performance and supports real-time ATM applications efficiently.

• Journal of Electrical Engineering and Technology
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• v.3 no.1
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• pp.94-100
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• 2008

This paper presents a new control method of single-phase active power filter (APF) for the compensation of harmonic current components in nonlinear loads. To facilitate the possibility of complex calculation for harmonic current detection of the single phase, a single-phase system that has two phases was constructed by including an imaginary second-phase giving time delay to the load current. The imaginary phase, which lagged the load current T/4 (Here T is the fundamental cycle) is used in the conventional method. But in this proposed method, the new signal as the second phase is delayed by the filter. Because this control method is applied to a single-phase system, an instantaneous calculation was developed by using the rotating reference frames synchronized to source-frequency rather than by applying instantaneous reactive power theory that uses the conventional fixed reference frames. The control scheme of single-phase APF for the current source with R-L loads is applied to a laboratory prototype to verify the proposed control method.

• Journal of Power Electronics
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• v.8 no.4
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• pp.317-324
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• 2008

This paper proposes a Multiband Shunt Hybrid Active Filter (SHAF) with sensorless control. A plant is modeled in the discrete- time domain and a controller is designed using the Pole shifting law in the polynomial domain. This control approach is very useful for filtering the load harmonics with reduced sensor counts where a low cost solution like SHAF is required. Multiple Synchronous Reference Frames (MSRF) and low pass filters are used to measure the $5^{th}$ and $7^{th}$ harmonic components separately from the load and filter currents. Individual current controllers are designed for the $5^{th}$ and $7^{th}$ harmonic currents. Control is realized in the stationary, three-phase (abc) reference frame. Performance of the controller is validated through simulation, using realistic plant and controller models, as well as experimentally on a full-scale distribution system.

• Journal of the Earthquake Engineering Society of Korea
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• v.15 no.1
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• pp.11-18
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• 2011

The connection type of steel moment frames in the country is mostly fabricated in factories so that it is fairly ductile due to good quality control. Based on references, the domestic connection satisfies the performance limit for steel intermediate moment frames specified by the AISC. However, the current KBC2009 building code specifies various systems for steel moment frames such as ordinary, intermediate, and special moment frames while the former KBC2005 only did so for a ductile moment frame. This induces the necessity of investigating which system is appropriate in the country when the domestic connection is applied. Therefore, this study was aimed at finding a proper design method by comparing the ductile moment frame in KBC2005 and the intermediate moment frames in KBC2009. The results showed that seismic design parameters for the ductile moment frames can be reasonable for satisfying the performance objective.