• Steel and Composite Structures
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• v.20 no.4
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• pp.833-849
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• 2016

Pre-stressing of existing structures using steel cables, FRP cables or FRP laminates has been successfully tried in the past. Retrofitting of beams using pre-stressed laminates does not utilize the full strength of the FRP due to de-bonding of the laminates before the fibre fracture. In the present study attempt has been made to overcome this problem by replacing the FRP laminates by the FRP sheets. In the present paper the effect of initial damage level and pre-stress level on strength, stiffness, cracking behaviour and failure mode of girders retrofitted using pre-stressed CFRP sheets has been studied. The results indicate that rehabilitation of initially damaged girders by bonding pre-stressed CFRP sheets improves the flexural behaviour of beams appreciably. However, it has been observed that with increase in pre-stressing force the load carrying capacity of the girders increases up to a particular level up to which the mode of failure is fibre fracture. Thereafter, the mode of failure shifts from fibre fracture to de-bonding and there is no appreciable increase in load carrying capacity with further increase in pre-stressing force.

• Journal of IKEEE
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• v.19 no.3
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• pp.455-459
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• 2015

This paper proposes a dispatch unit of GP-GPU with SIMT architecture to support the acceleration of general-purpose operation as well as graphics processing. If all the information of an operand used instructions issued from the warp scheduler is decoded, an unnecessary operand load occurs, resulting in register loads. To resolve this problem, this paper proposes a method that can reduce the operand load and the load on the resister by decoding only the information of the operand using a pre-decoding method. The operand information from the dispatch unit is passed to the operand selection unit with preventing register bank collisions. Thus the overall performance are improved. In the simulation test, the total clock cycles required by processing 10,000 arbitrary instructions issued from the wrap scheduler using ModelSim SE 10.0b are measured. It shows that the application of the dispatch unit equipped with the pre-decoding function proposed in this paper can make an improvement of about 12% in processing performance compared to the conventional method.

• Journal of Korean Society on Water Environment
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• v.32 no.6
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• pp.600-627
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• 2016

Korea is one of the countries with a large veterinary antibiotics market, although antimicrobial resistance in bacteria is becoming a serious issue in many countries. The Korean government started to take interest in estimating the effects of livestock manure on rivers and agricultural soils and in monitoring of heavy metals, organic pollutants and antibiotics in the ambient water and soil. In this paper, pre-treatment methods to separate the selected antibiotics from solid samples were reviewed. It is essential to select an efficient and appropriate procedure for pre-treatment due to the high proportion of proteins and organics in biosolid samples. Pre-treatment consists of extraction followed by clean-up. Initially, homogenized samples were extracted by sonication, mechanical agitation or pressurized liquid extraction with methanol/acetonitrile/water mixture under acidic/basic conditions depending on the compound. However, aminoglycosides and colistin were extracted with 5% trichloroacetic acid and HCl, respectively. Since the ${\beta}-lactams$ are easily decomposed in acidic and basic conditions, they were extracted in neutral pH. Filtration with a membrane (pore size, $0.2{\mu}m$) or solid phase extraction with HLB and methanol, as eluents, was normally applied for the clean-up. At least, three different pre-treatment procedures should be adopted to screen all the selected antibiotics in solid samples.

• Steel and Composite Structures
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• v.6 no.5
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• pp.401-415
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• 2006

Based on a non-linear model taking into account flexural-torsional couplings, analytical solutions are derived for lateral buckling of simply supported I beams under some representative load cases. A closed form is established for lateral buckling moments. It accounts for bending distribution, load height application and pre-buckling deflections. Coefficients $C_1$ and $C_2$ affected to these parameters are then derived. Regard to well known linear stability solutions, these coefficients are not constant but depend on another coefficient $k_1$ that represents the pre-buckling deflection effects. In numerical simulations, shell elements are used in mesh process. The buckling loads are achieved from solutions of eigenvalue problem and by bifurcations observed on non linear equilibrium paths. It is proved that both the buckling loads derived from linear stability and eigenvalue problem lead to poor results, especially for I sections with large flanges for which the behaviour is predominated by pre-buckling deflection and the coefficient $k_1$ is large. The proposed solutions are in good agreement with numerical bifurcations observed on non linear equilibrium paths.

• Proceedings of the Korea Concrete Institute Conference
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• 1999.10a
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• pp.701-704
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• 1999

The purpose of this study was to investigate the effectiveness of the flexural rehabilitation of the pre-loaded reinforced concrete beams strengthened by the steel plate. Main test parameters were the existence and the magnitude of the pre-loading at the flexural of rehabilitation and the tensile reinforcement ratio of the specimens. Seven beam specimens were tested to investigate the effectiveness of the rehabilitation method. Test results showed that the ultimate load capacities of the pre-loaded specimens were higher than not-pre-loaded specimens at the rehabilitation. The cause of the pharameter was analyzed if is suggested that the bond failure between the concrete and the strengthening steel plate occured prior to the yielding of the tension reinforcement. The member flexural stiffnesses, were similar regardless of the load conditions at retrofit and failure modes showed brittle aspect caused by rip-off failure.

• Journal of Korean Tunnelling and Underground Space Association
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• v.9 no.4
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• pp.331-341
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• 2007

Pre-loads could be imposed on the braced wall to prevent the horizontal displacements during the ground excavation adjacent to the existing tunnel. For this purpose, new pre-loading system through which large pre-loads could be applied to the braced wall was used in the model tests. Large scale model tests were performed in the real scale test pit which was 2.0 m in width and 6.0 m in hight and 4.0 m in length. Test ground was constructed by sand. Model tunnel in 1.2 m diameter was constructed before test ground excavation. Test ground was excavated adjacent to existing tunnel and was braced. To investigate the effect of pre-loading, tests without pre-load were also performed. During the ground excavation were the behavior of braced wall, test tunnel, and ground measured. Model tests were also numerically analysed and their results were compared to that of the real scale tests. As a result, it was found that the stability of the existing tunnel was greatly enhanced when the horizontal displacements of braced wall was reduced by applying pre-load larger than the design load.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.05a
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• pp.92-95
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• 2004

The flexural strengthening effect of the RC beam strengthened with CFS under pre-loading condition was studied here. The beams were additionally strengthened at the each end with U type wrapping using the same CFS. Main variables considered were number of CFS plies(1,2) and pre-loading values(30,50,$70\%$ of the yield load of the control beam). The flexural strengthening effect was investigated through comparing the yield load, ultimate load, and ductility index of the specimens.

• Proceedings of the Korea Concrete Institute Conference
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• 2009.05a
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• pp.193-194
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• 2009

In this study, a simple indeterminate strut-tie model reflecting all characteristics of the ultimate strengths and complicated structural behavior of pre-tensioned concrete deep beams is presented. In addition, a load distribution ratio, defined as a magnitude of load transferred by a vertical truss mechanism, is proposed to help structural designers perform the strength analysis of pre-tensioned concrete deep beams by using the strut-tie model approaches of current design codes.

• Proceedings of the KSME Conference
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• 2001.06b
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• pp.355-360
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• 2001

By using Frenet formulation and Timoshenko beam theory, the partial differential equations of motion are derived for a helical spring having a doubly symmetrical cross section subjected to the pre-load axially. These equations of motion are solved to give the dispersion relationship and dynamic stiffness matrix is assembled. Natural frequencies are obtained from the receptance of the system. The results of the dynamic stiffness method are compared with those of the transfer matrix method from published examples and finite element method.

• Magazine of the Korean Society of Agricultural Engineers
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• v.20 no.3
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• pp.4750-4770
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• 1978

Under the various variations of the sample thickness, the load increment ratio and the load increment duration, this consolidation test of the clay in the Asan Bay was tried for the comparison with the standard consolidation test. The results gained are as follows; 1. The void ratio variations of the leached-clay samples were increasingly high, according as the sample thickness thinned and the load increment duration and the laod increment ratio increased. 2. The coefficient of consolidation were increased with the increment of the sample thickness, of the load increment ratio and of the load increment duration. Near the pre-consolidation load, the coefficient of secondary consolidation had the maximum value and lessened with the increment of the sample thicknss, and of the load increment duration 3. The value of the pre-consolidation load increased in proportion to the increment of the sample thickness and the decrease of the load increment ratio and the load increment duration. 4. The compression indices increased as the increment of load increased and decreased as the sample thickness increased. 5. The initial compression ratio increased as the sample thickness, the load increment ratio and the load increment duration decreased. The ratio of primary compression to the secondary decreased with the increment of the sample thickness and of the load increment ratio. 6. The time at the completion of psimary consolidation increased with the increment of the sample thickness and of the consolidation load, and with the decrease of the load increment ratio. 7. The compression indicses increaed as the sample thickness lessened and decreased as the load increment ratio increased. The coefficient of consolidation increased according as the sample thickness, the load increment ratio and the load increment duration went up. The settlement at the construction site should be calculated highly in proportion as the sample thickness lessened and the load increment ratio increased. The consolidation ratio is thought to be accelerated if the sample thickness and the load increment ratio becomes higher and the load increment duration longer.