• Steel and Composite Structures
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• v.20 no.2
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• pp.357-378
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• 2016

The progressive collapse phenomenon in structures has been interested by civil engineers and the building standards organizations. This is particularly true for the tall and special buildings ever since local collapse of the Ronan Point tower in UK in 1968. When initial or secondary defects of main load carrying elements, overloads or unpredicted loads occur in the structure, a local collapse may be arise that could be distributed through entire structure and cause global collapse. One is not able to prevent the reason of failure as well as the prevention of propagation of the collapse. Also, one is not able to predict the start point of collapse. Therefore we should generalize design guides to whole or the part of structure based on the risk analysis and use of load carrying elements removal scenario. There are some new guides and criteria for elements and connections to be designed to resist progressive collapse. In this paper, codes and recommendations by various researchers are presented, classified and compared for steel structures. Two current design methods are described in this paper and some retrofitting methods are summarized. Finally a steel building with special moment resistant frame is analyzed as a case study based on two standards guidelines. This includes consideration of codes recommendations. It is shown that progressive collapse potential of the building depends on the removal scenario selection and type of analysis. Different results are obtained based on two guidelines.

• Proceedings of the Korean Society of Crop Science Conference
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• 2017.06a
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• pp.93-93
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• 2017

To develop rice cultivars with increased biomass and grain yield, superior lodging resistance is an essential trait. The new breeding approach can be adopted for the improvement of stem lodging resistance by enhancing culm strength. The resistance to breaking type lodging is attributed to bending moment of basal culm (M), which is composed of the section modulus (SM) and bending stress (BS). The resistance to the bending type lodging is attributed to flexural rigidity (FR) of stem, which is composed of the secondary moment of inertia (SMI) and Young's modulus (YM). Starch and cell wall components such as cellulose, hemicellulose and lignin also play a significant role in physical strength of culm, and thus affect lodging. Leaf Star has a superior lodging resistance due to its thick and stiff culm because of its high M and FR compared with Koshihikari. Furthermore, Leaf Star contains high densities of hemicellulose, cellulose and low lignin density in culm compared with Koshihikari. In this study, we performed QTL analysis for these traits associated with culm strength, using 94 recombinant inbred lines (RILs, $F_8$), derived from a cross between Leaf Star and Koshihikari. The SM in the RILs showed a continuous distribution. QTLs for SM were detected on chrs.2, 3 and 10. Leaf Star alleles increased SM on chrs. 2 and 3, but Koshihikari allele increased on chr.10. These QTLs overlapped with those QTLs identified using backcrossed inbred line derived from a cross between Chugoku 117 and Koshihikari, the parents of Leaf Star. The FR in Leaf Star was higher than that in Koshihikari due to the larger SMI and YM. 3 QTLs for SMI were detected on chrs.2, 3 and 10. Leaf Star alleles increased SMI on chrs.2 and 3, and Koshihikari alleles increased on chr.10. One QTL on chr.3 and two QTLs on chr.5 for hollocelulose content were detected with Leaf Star alleles contribution. Moreover, two QTLs were detected for hemicellulose density on chrs.3 and 5. Leaf Star allele increased hemicellulose density on chr.5, and Koshihikari allele increased on chr.3. Furthermore, two QTLs for cellulose density were detected on chr.5, and one QTL on chr.2. For starch content, one QTL on chr.3 and two QTLs on chr.5 with Leaf Star alleles contribution were detected. TULK-6 carrying a chromosome segment of Leaf Star on chr.5 in the Koshihikari genetic background showed higher densities of starch and hemicellulose than those in Koshihikari. These results suggest that the detected QTLs for culm strength could be utilized for the improvement of lodging resistance in rice by marker-assisted selection.

• Proceedings of the Korean Society of Crop Science Conference
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• 2017.06a
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• pp.133-133
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• 2017

Lodging is one of the important constraints in rice production. The lodging destroys the canopy structure, and sharply reduces the capacity of photosynthetic rate and dry matter production. In cereal crops, stem lodging can be classified into two types: stem breaking type and stem bending type. To improve stem lodging resistance, it is important to reveal strong culm traits of superior lodging resistant varieties. There are large varietal differences in parameters associated with the bending moment at breaking (M) and flexural rigidity (FR). The indica variety Takanari possesses large M due to its large section modulus (SM) despite of its small bending stress (BS), while Takanari also has large FR due to its large secondary moment of inertia (SMI) and Young's modulus (YM). To identify quantitative trait loci (QTLs) and the corresponding genes associated with the parameters for M ($=SM{\times}BS$) and FR ($=SM{\times}YM$) should enable to develop lodging resistant varieties, efficiently. In order to identify QTLs for cell wall materials such as cellulose, hemicellulose and lignin associated with BS and YM, a set of Chromosome Segment of Substitution Lines (CSSLs) consisted of 37 lines with chromosome segments of Koshihikari in the genetic background of Takanari were used. Takanari had large M and small BS as compared with Koshihikari. The QTLs for BS were estimated on chromosomes 3, 5, 6, 8, 9, 10, 11 and 12. Koshihikari alleles increased BS in these QTLs. Takanari had a large FR due to its large SMI and YM as compared with Koshihikari. The YM was increased by substitution of the Koshihikari chromosomal segments on chromosomes 2, 10 and 11. Other QTLs estimated on chromosomes 7 and 12 that Koshihikari alleles contributed to the decrease of YM. For lignin, only one major QTL for lignin density was detected on chromosome 11. Hollocellulose densities were increased by the substitution of Koshihikari segments on chromosomes 5 and 11. On the other hand, these were decreased on chromosomes 1 and 3 by substitution of Koshihikari segments. QTLs for cellulose density were estimated on chromosomes 1, 3 and 5 by substitution of Koshihikari segments. For hemicellulose, QTL on chromosome 3 showed that hemicellulose density decreased by the substitution of Koshihikari segment. However, hemicellulose densities on chromosomes 5, 8 and 11 showed the opposite effects. The QTLs for hemicellulose, cellulose, and hollocelulose densities identified on chromosome 5 overlapped with that for bending stress, indicating the positive effect of Koshihikari segment on increasing bending stress. These results suggest that some QTLs for the densities of cell wall materials contribute to increasing bending stress and Young's modulus, and could be utilized to improve the lodging resistance for both types of breaking and bending in rice varieties.

• Convergence Security Journal
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• v.16 no.1
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• pp.13-21
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• 2016

At the present moment when around 60 years have passed after the introduction of private security, there are security instructor and protection specialist guard as government official recognition qualification. This study discussed problems of secondary performance test system among qualification certification items which have been implement ed as government official recognition qualification since 2013. Current qualification certification for protection specialist guard is composed of primary academic test and secondary performance test. Since it is estimated that it is high time to increase clients' satisfaction and public reliability through strict qualification certification for protection specialist guard. Following improvement plans are intended to suggest. First, it is a plan to divide and diversify difficulties of performance test evaluation events. Second, it is a plan to diversify evaluation criteria of performance test. Third, it is a plan to make criteria for selecting specialized performance test evaluation committee. Fourth, it is a new plan of exclusion system to avoid any relation between performance test evaluation committee and applicants. In this respect, institutional improvement should be followed in order to improve specialty of qualification certification of performance test system for protection specialist guard.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.23 no.3
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• pp.303-314
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• 2010

A study for the nonlinear analysis method of prestressed concrete(PSC) girders with external tendons is presented. The PSC girders with external tendons show the complex nonlinear behavior due to the slip of external tendons at deviator and the change of eccentricity between the girders and external tendons. The external tendon between anchorage-deviator or deviator-deviator is modeled as an assemblage of the curved elements. The slip effect of the external tendon at deviator is taken into account using the force equilibrium relationship between the friction force and the driving force at each deviator. The finite element model and analysis method of the external tendon suggested herein are integrated in the nonlinear analysis program of segmentally erected PSC frames developed by the authors. The proposed analysis method is verified through the comparison of the analysis and experimental results obtained from other investigators. From the ultimate analysis results of PSC beams with external tendons having different number of deviators, the yielding and ultimate loads of PSC beams found to be increased as the number of deviators are increased. In addition, the ultimate capacity of the PSC beam increases according to the increase of friction coefficient between deviator and external tendon, whereas found to decease over the certain value of friction due to the effect of the moment transmitted to the member by the friction force exerted from the external tendon.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.5
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• pp.569-576
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• 2019

PSC-Edge Rahmen Bridge makes low thickness and long span by introducing prestressed force to the edge girder and reducing positive moment. In the bridge, diagonal tension cracks occurred in the direction of $45^{\circ}$ to outer side of the girder after the temporary bent supported on the lower part of the upper slab and the secondary strand is tensioned on the girder. Researches on stress distribution and burst crack behavior of pre-stress anchorage has been conducted, it is difficult to analyze an obvious cause due to difference between actual shape and boundary condition. This study performed 3D frame analysis with additional boundary condition of temporary bent, the maximum compression stress occurred in the girder and there was a limit to identify the cause. It performed 3D Solid analysis with LUSAS 16.1 and the maximum principal tensile stress occurred at the boundary between the girder and the slab. As analyzing required reinforcement quantity at obtuse angle of the girder with the maximum principal tensile stress and directional cosine, reinforcement quantity was insufficient. Additional bridges have increased reinforcement quantity and extended area and crack was not occurred. It is expected that cracks on the girder during construction could be controlled by applying the proposed method to PSC-Edge Rahmen Bridge.

• Structural Engineering and Mechanics
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• v.52 no.6
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• pp.1069-1084
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• 2014

The long-term performance of plates resting on viscoelastic foundations is a major concern in the analysis of soil-structure interaction. As a powerful mathematical tool, fractional calculus may address these plate-on-foundation problems. In this paper, a fractionalized Zener model is proposed to study the time-dependent behavior of a uniformly loaded rectangular thin foundation plate. By use of the viscoelastic-elastic correspondence principle and the Laplace transforms, the analytical solutions were obtained in terms of the Mittag-Leffler function. Through the analysis of a numerical example, the calculated plate deflection, bending moment and foundation reaction were compared to those from ideal elastic and standard viscoelastic models. It is found that the upper and lower bound solutions of the plate response estimated by the proposed model can be determined using the elastic model. Based on a parametric study, the impacts of model parameters on the long-term performance of a foundation plate were systematically investigated. The results show that the two spring stiffnesses govern the upper and lower bound solutions of the plate response. By varying the values of the fractional differential order and the coefficient of viscosity, the time-dependent behavior of a foundation plate can be accurately captured. The fractional differential order seems to be dependent on the mechanical properties of the ground soil. A sandy foundation will have a small fractional differential order while in order to simulate the creeping of clay foundation, a larger fractional differential order value is needed. The fractionalized Zener model is capable of accounting for the primary and secondary consolidation processes of the foundation soil and can be used to predict the plate performance over many decades of time.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.29 no.5
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• pp.413-419
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• 2016

Damage of infrastructures by an earthquake causes the secondary damage through the world at large more than the damage of the structures themselves. Amomg them, underground utility tunnel structures comes under the special life line: communication, gas, electricity and etc. and it has a need to evaluate its fragility to an earthquake exactly. Therefore, the destruction ability according to peak ground acceleration of earthquakes for the underground utility tunnels is evaluated in this paper. As an input ground motion for evaluating seismic fragilities, real earthquakes and artificial seismic waves which could be generated in the Korean peninsula are used. And as a seismic analysis method, response displacement method and time history analyzing method are used. An limit state which determines whether destruction is based on the bending moment and shear deformation. A method used to deduct seismic fragility curve is method of maximum likelihood and the distribution function is assumed to the log normal distribution. It could evaluate the damage of underground utility tunnels to an earthquake and could be applied as basic data for seismic design of underground utility tunnel structures.

• The KSFM Journal of Fluid Machinery
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• v.10 no.6
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• pp.32-37
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• 2007

Aerodynamic forces and moments have been used to control rocket propelled vehicles. If control is required at very low speed, Those systems only provide a limited capability because aerodynamic control force is proportional to the air density and low dynamic pressure. But thrust vector control(TVC) can overcome the disadvantages. TVC is the method which generates the side force and roll moment by controlling exhausted gas directly in a rocket nozzle. TVC is classified by mechanical and fluid dynamic methods. Mechanical methods can change the flow direction by several objects installed in a rocket nozzle exhaust such as tapered ramp tabs and jet vane. Fluid dynamic methods control the flight direction with the injection of secondary gaseous flows into the rocket nozzle. The tapered ramp tabs of mechanical methods are used in this paper. They installed at the rear in the rocket nozzle could be freely moved along axial and radial direction on the mounting ring to provide the mass flow rate which is injected from the rocket nozzle. In this paper, the conceptual design and the study on the tapered ramp tabs of the thurst vector control has been carried out using the supersonic cold flow system and schlieren system. This paper provides the thrust spoilage, three directional forces and moments and distribution of surface pressure on the region enclosed by the tapered ramp tabs.

• Proceedings of the Korean Society of Crop Science Conference
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• 2017.06a
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• pp.95-95
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• 2017

Lodging is a serious issue in rice production, because it drastically decreases the biomass production and grain yield. Since the Green Revolution, the lodging resistance has been increased by lowering the moment of above-ground parts due to the short culm by the semi-dwarf gene sd1. However, it has been pointed out that sd1 alone has suppressive effects for biomass production and yield. To increase rice yield, the long-culm and large panicle type varieties with a superior lodging resistance need to be developed. To improve the lodging resistance and yield of these type varieties, it would be effective to identify novel alleles for these traits underlying natural variations in rice and to pyramid these alleles to a single rice variety. In order to perform this strategy, we have developed new rice lines derived from crosses among varieties with superior alleles. At first, TULT-gh-5-5 was selected from a cross between strong culm and high biomass variety Leaf Star and high-yielding variety Takanari, and TUAT-32HB was selected from a cross between high-yielding variety Akenohoshi and Takanari. Then, we developed the super thick-culm and super grain-bearing line, LTAT-29 derived from a cross between TULT-gh-5-5 and TUAT-32HB. In the current study, to identify the QTLs and genes relating to the strong culm and the high yield of LTAT-29, we performed QTL analysis using SNPs markers with $F_2$ population derived from a cross between LTAT-29 and Takanari. LTAT-29 has never lodged throughout the growth period despite it had long culms and heavy panicles. LTAT-29 had a larger outer diameter of the culm and twice the size of the section modulus than Takanari. As a result, the bending moment at breaking of LTAT-29 was significantly larger than that of Takanari. Brown rice yield of LTAT-29 was $9.2t\;ha^{-1}$ about 10% higher than that of Takanari due to the larger number of spikelets per panicle. LTAT-29 had a greater number of secondary branches per panicle. In the $F_2$ population between LTAT-29 and Takanari, we found continuous frequency distributions in the section modulus and the spikelet number per panicle. Two QTLs increased the section modulus by the alleles of LTAT-29 were detected on Chr.1L and Chr.2L. One QTL increased the spikelet number per panicle of Takanari by the allele of LTAT-29 was detected on Chr.1L, and two QTLs increased the number of secondary branches per panicle by the alleles of LTAT-29 were detected on Chr.1L and Chr.4L. It was found that the alleles of these QTLs were the japonica type originated from Leaf Star or Akenohoshi. The novel QTLs for the traits related to super thick-culm and super grain-bearing and their combinations could be utilized for improving the lodging resistance and yield in rice varieties.