• Structural Engineering and Mechanics
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• v.31 no.4
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• pp.423-437
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• 2009

In order to perform a step-by-step force-displacement response analysis or dynamic time-history analysis of large buildings with masonry infilled R/C frames, a continuous force-deformation model based on an equivalent strut approach is proposed for masonry infill panels containing openings. The model, which is applicable for degrading elements, can be implemented to replicate a wide range of monotonic force-displacement behaviour, resulting from different design and geometry, by varying the control parameters of the model. The control parameters of the proposed continuous model are determined using experimental data. The experimental program includes fifteen 1/3-scale, single-story, single-bay reinforced concrete frame specimens subjected to lateral cyclic loading. The parameters investigated include the shape, the size, the location of the opening and the infill compressive strength. The actual properties of the infill and henceforth the characteristics needed for the diagonal strut model are based on the assessment of its lateral resistance by the subtraction of the response of the bare frame from the response of the infilled frame.

• Tribology and Lubricants
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• v.22 no.2
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• pp.73-78
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• 2006

The surface modification of automobile parts is of great technological importance for the improvement of corrosion resistance, wear resistance, fatigue strength and so on. Recently, research on the development of the technology of surface modification substituting 6-balance chrome process has progressively been achieved in automobile parts. Although the innovation technology for the improvement of the corrosion-resisting and wear resistant properties through post oxidation after nitrocarburising process had attracted a great attention. For this, anodically potentiodynamic polarisation testing was carried out to corrosion resistance and friction and wear experiment according to applied load and sliding distance was carried out to evaluate the wear resistance of machine structural steel with nitrocarburising and non-nitrocarburising SM45C. The presumed wear volume was calculated with the image processing far evaluation of wear resistance of two materials. The results show that the nitrocarburising had a distinguished corrosion resistance and wear resistance than non-nitrocarburising.

• Knowledge Management Research
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• v.6 no.2
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• pp.105-118
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• 2005

The future will see all industries become technology-driven in the competitive global market place. Firms with deep technological roots and innovation strategies have some advantages. Business valuation of technology is critical to the future of firm's business. In this situation widely used scoring valuation is not enough to evaluate relative business competitiveness associated with technology and to assign its relative ranking category. Therefore, a more useful and comprehensive new valuation approach, which is called business composite index, is needed to complement and to enhance the existing scoring valuation approach. In this research, statistical factor analysis is applied to determine the common factors and to estimate associated weights. And business composite index, which is a kind of weighted scoring method, is derived based on the results of factor analysis. This research shows that business composite index is considered very useful to measure the business relative strength of individual technology and also to assign its relative ranking category instead of absolute ranking based on scoring valuation approach.

• Earthquakes and Structures
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• v.1 no.2
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• pp.163-175
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• 2010

The vertical axis through the modal center of rigidity (m-CR) is used for interpreting the code torsional provisions in the design of eccentric multi-story building structures. The concept of m-CR has been demonstrated by the author in an earlier paper and the particular feature of this point is that when the vertical line of the centers of mass at the floor levels is passing through m-CR, minimum base torsion is developed. For this reason the aforesaid axis is used as reference axis for implementing the code provisions required by the equivalent static analysis. The study examines uniform mixed-bent-type multistory buildings with simple eccentricity, ranging from torsionally stiff to torsionally flexible systems. Using the results of a dynamic response spectrum analysis as a basis for comparisons, it is shown that the results of the code static design are on the safe side in torsionally stiff buildings, but unable to predict the required strength of bents on the stiff side of systems with a predominantly torsional response. Suggestions are made for improving the code provisions in such cases.

• Earthquakes and Structures
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• v.10 no.3
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• pp.613-628
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• 2016

The effectiveness of the use of modern repair schemes for the seismic retrofit of existing RC structures were assessed on a comparative experimental study of carbon fiber-reinforced polymer (CFRP) strips and sheets for the repair of reinforced concrete members of RC frames, damaged because of cyclic loading. Two virgin, single - story, one - bay, 1/3 - scale frame specimens were tested under cyclic horizontal loading, up to a drift level of 4%. Then, virgin specimens, B and F, respectively, were repaired and retested in the same way. One, specimen RB, was repaired with epoxy injections and CFRP strips and one, specimen RF, was repaired with epoxy injections and CFRP sheets. The two specimens are used to examine the differences between the structural behavior of frames repaired using CFRP strips and frames repaired using CFRP sheets. Both qualitative and quantitative conclusions, based on the observed maximum loads, loading and reloading stiffness, hysteretic energy absorption and failure mechanisms are presented and compared. The repaired frames recovered their strength, stiffness and energy dissipated reasonably. The use of CFRP sheets was found more effective than CFRP strips, due to the proper anchorage.

• Geomechanics and Engineering
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• v.17 no.5
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• pp.497-505
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• 2019

Biocementation based on the microbially induced calcite precipitation (MICP) process is a novel soil improvement method. Biocement can improve significantly the properties of soils by binding soil particles to increase the shear strength or filling in the pores to reduce the permeability of soil. In this paper, results of triaxial consolidated undrained (CU) tests and constant shear drained (CSD) tests on biocemented Ottawa sand are presented. In the CU tests, the biocemented sand had more dilative behaviour by showing a higher stress-strain curves and faster pore pressure reducing trends as compared with their untreated counterparts. In the CSD tests, the stress ratio q/p' at which biocemented sand became unstable was higher than that for untreated sands, implying that the biocementation will improve the stability of sand to water infiltration or liquefaction.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2020.11a
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• pp.104-105
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• 2020

Red mud is a highly alkaline waste by-product of the aluminum industry. Although recycling of red mud is being actively researched, a feasible technological solution has not been found yet. In this study, we propose that neutralization of red mud alkalinity could assist in its use as a construction material. Neutralized red mud ( pH 6-8) was prepared by adding sulfuric acid to liquefied red mud (pH 10-12). After adding liquid and neutralized red mud to the cement paste, the heat of hydration was measured. As a result of the experiment, the calorific value of the cement paste with liquid red mud was lowered and delayed compared to the cement paste with neutralized red mud.

• The Journal of Advanced Prosthodontics
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• v.7 no.1
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• pp.39-46
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• 2015

PURPOSE. The mechanical and interfacial characterization of laser welded Co-Cr alloy with two different joint designs. MATERIALS AND METHODS. Dumbbell cast specimens (n=30) were divided into 3 groups (R, I, K, n=10). Group R consisted of intact specimens, group I of specimens sectioned with a straight cut, and group K of specimens with a $45^{\circ}$ bevel made at the one welding edge. The microstructure and the elemental distributions of alloy and welding regions were examined by an SEM/EDX analysis and then specimens were loaded in tension up to fracture. The tensile strength (TS) and elongation (${\varepsilon}$) were determined and statistically compared among groups employing 1-way ANOVA, SNK multiple comparison test (${\alpha}$=.05) and Weibull analysis where Weibull modulus m and characteristic strength ${\sigma}_0$ were identified. Fractured surfaces were imaged by a SEM. RESULTS. SEM/EDX analysis showed that cast alloy consists of two phases with differences in mean atomic number contrast, while no mean atomic number was identified for welded regions. EDX analysis revealed an increased Cr and Mo content at the alloy-joint interface. All mechanical properties of group I (TS, ${\varepsilon}$, m and ${\sigma}_0$) were found inferior to R while group K showed intermediated values without significant differences to R and I, apart from elongation with group R. The fractured surfaces of all groups showed extensive dendritic pattern although with a finer structure in the case of welded groups. CONCLUSION. The K shape joint configuration should be preferred over the I, as it demonstrates improved mechanical strength and survival probability.

• Proceedings of the Korean Geotechical Society Conference
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• 2005.03a
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• pp.483-490
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• 2005

At present around 50 companies have their own crushing plants, which manufacture rock into crushed sand, over around 350 different quarry throughout the nation. However, in most plants the stone dust sludge is left as it is in their plants so that they have difficulty to utilize. Furthermore, environmental pollution may be even caused due to dust generated when it is dried. Recycling is starting capturing the attention of the people working over the quarry due to the reasons described above. This research has studied in the quarters the usability as landfill liner of the stone dust sludge, which is industrial waste. We investigated what technological properties it would have after mixing the stone dust sludge with SM(sandy soil) first and then with blast furnace slag or reject ash, which is waste, and cement as the stabilizer. As the result of three tests; compacting test, strength test, and permeability test; to satisfy the regulatory guideline of the government that is the compress strength over 5 $kgf/cm^2$, the flexibility over 1 $kgf/cm^2$, and the permeability under $1.0{\times}10^{-7}cm/sec$ From this research, we could confirm that stone dust sludge would be used as waste landfill liner if it were mixed with other waste by the proper mixing ratio.

• Earthquakes and Structures
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• v.17 no.1
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• pp.115-129
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• 2019

The effectiveness of an innovative method for the earthquake-resistant rehabilitation of existing poorly detailed reinforced concrete (RC) structures is experimentally investigated herein. Eight column subassemblages were subjected to earthquake-type loading and their hysteretic behaviour was evaluated. Four of the specimens were identical and representative of columns found in RC structures designed in the 1950s-70s period for gravity load only. These original specimens were subjected to cyclic lateral deformations and developed brittle failure mechanisms. Three of the damaged specimens were subsequently retrofitted with innovative high-strength steel fiber-reinforced concrete (HSSFC) jackets. The main variables examined were the jacket width and the contribution of mesh steel reinforcement in the seismic performance of the enhanced columns. The influence of steel fiber volume fraction was also examined using test results of a previous work of Tsonos et al. (2017). The fourth earthquake damaged subassemblage was strengthened with a conventional RC jacket and was subjected to the same lateral displacement history as the other three retrofitted columns. The seismic behaviour of the subassemblages strengthened according to the proposed retrofit scheme was evaluated with respect to that of the original specimens and that of the column strengthened with the conventional RC jacket. Test results clearly demonstrated that the HSSFC jackets effectively prevented the development of shear failure mechanisms, while ensuring a ductile seismic response similar to that of the subassemblage retrofitted with the conventional RC jacket. Ultimately, an indisputable superiority in the overall seismic performance of the strengthened columns was achieved with respect to the original specimens.