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Kim S.-H.,Hanbat National University | Noh S.-Y.,Hanyang University | Kim K.-S.,Hanyang University | Han B.-S.,Dongbu Corporation
Applied Mechanics and Materials | Year: 2012

The cross section of Permanent Uni-Wall System (PUS) is formed by circular casing and special casing. As for the special casing cross section of PUS, it is difficult to calculate the shear strength because of atypical section. This study conducted a shear test for three specimens, the variable of which is the shape of the PUS cross section, without the shear reinforcing bar. The test results showed that the shear strength of the specimens had a resisting force larger than the nominal shear strength by ACI318. It was also found that the specimens of PUS's special casing cross section and the specimen of the equivalent rectangular cross section had a similar level of shear strength. © (2012) Trans Tech Publications, Switzerland.

Lee H.,Sustainable Development Technology | Lee D.,Korea University | Hong S.,Korea University | Yun G.H.,Korea University | And 4 more authors.
Journal of Environmental Sciences (China) | Year: 2014

Anoxic gas recirculation system was applied to control the membrane fouling in pilot-scale 4-stage anoxic membrane bioreactor (MBR). In the anaerobic-anoxic-anoxic-aerobic flow scheme, hydrophilic polytetrafluoroethylene (PTFE) membrane (0.2 μm, 7.2 m2/module) was submerged in the second anoxic zone. During 8 months operation, the average flux of the membrane was 21.3 L/(m2·hr). Chemical cleaning of the membrane was conducted only once with sodium hydroxide and sodium hypochlorite. Dissolved oxygen (DO) concentration in the second anoxic zone was maintained with an average of 0.19 ± 0.05 mg/L. Gas chromatography analysis showed that the headspace gas in the second anoxic reactor was mainly consisted of N2 (93.0% ± 2.5%), O2 (3.8% ± 0.6%), and CO2 (3.0% ± 0.5%), where the saturation DO concentration in liquid phase was 1.57 mg/L. Atmospheric O2 content (20.5% ± 0.8%) was significantly reduced in the anoxic gas. The average pH in the reactor was 7.2 ± 0.4. As a result, the recirculation of the anoxic gas was successfully applied to control the membrane fouling in the anoxic MBR. © 2014 The Research Centre for Eco-Environmental Sciences, Chinese Academy of Sciences.

Seo D.,Hanyang University | Shin S.,Hanyang University | Han B.,Dongbu Corporation
Journal of Asian Architecture and Building Engineering | Year: 2010

The strength of reinforced concrete members may vary from the calculated or the nominal strength due to variations in the material strength and dimensions of the element. Statistical descriptions of the variabilities in loads and strengths are required in all studies pertaining to the safety of reinforced concrete members. Therefore, this paper recommends a number of values for the coefficient of variation of concrete, reinforcement, dimension and load to be used in the probability analysis. Also, this study analyzes reinforced concrete members using the Advanced First Order Second Moment (AFOSM) method using the statistical characterization of variables. This study shows that Bayes' theorem is an effective tool for updating prior probabilities when the value of a random parameter is known. Finally, the results in this paper contribute to the limit state reliabilities implied in the current design of reinforced concrete elements.

Choi S.W.,Yonsei University | Kim I.S.,POSCO | Park J.H.,Dongbu Corporation | Kim Y.,Yonsei University | And 2 more authors.
Sensors (Switzerland) | Year: 2013

The outrigger truss system is one of the most frequently used lateral load resisting structural systems. However, little research has been reported on the effect of installation of outrigger trusses on improvement of lateral stiffness of a high-rise building through full-scale measurements. In this paper, stiffness changes of a high-rise building due to installation of outrigger trusses have been evaluated by measuring lateral displacements using a global positioning system (GPS). To confirm the error range of the GPS measurement system used in the full-scale measurement tests, the GPS displacement monitoring system is investigated through a free vibration test of the experimental model. Then, for the evaluation of lateral stiffness of a high-rise building under construction, the GPS displacement monitoring system is applied to measurements of lateral displacements of a 66-story high-rise building before and after installation of outrigger truss. The stiffness improvement of the building before and after the installation is confirmed through the changes of the natural frequencies and the ratios of the base shear forces to the roof displacements. © 2013 by the authors; licensee MDPI, Basel, Switzerland.

Seo K.,Dongbu Corporation | Lee J.,Yonsei University
International Journal of Offshore and Polar Engineering | Year: 2014

The piezocone penetration test (PCPT) is an effective in-situ testing method for the characterization of saturated clays. While various PCPT-based consolidation analysis methods were developed, uncertainties still exist, which are associated with the type of interpretation methods and model parameter determination. In this paper, a methodology for the analysis of horizontal consolidation using PCPT dissipation test results is explored and proposed for the application in vertical drains. Based on the concept of time-drainage distance relationship, a direct correlation model between field horizontal consolidation and PCPT dissipation processes is proposed. The proposed method refers the whole range of the PCPT dissipation process, and thus more realistic consolidation prediction is expected. PCPT dissipation test results and time-settlement data from the test site are used to evaluate the correlation parameter for the proposed method. In order to validate the proposed method, experimental test results were collected from the literature and used to compare measured and predicted consolidation behavior. It is observed that the results from the proposed method show reasonably close agreement with measured field consolidation settlements. © 2014 The International Society of Offshore and Polar Engineers.

Lee J.,Yonsei University | Seo K.,Yonsei University | Park Y.,Dongbu Corporation
International Journal of Offshore and Polar Engineering | Year: 2010

The piezocone penetration test (PCPT) is particularly effective for the characterization of saturated clays as it allows measurements of both strength and consolidation properties. While various PCPT-based methods have been developed, most of them have focused on time-dependent consolidation characteristics, and no specific attention has been given to the evaluation of compressibility-related parameters. In this paper, a methodology was proposed for the estimation of the compression index using PCPT dissipation results. In order to reflect stress state and volume change during consolidation, the time-stress-volume change relationship was analyzed and introduced into the investigation. Based on the concept of the coupled time-stress-volume relationship, a correlation was proposed between the compression index and PCPT dissipation results. PCPT and consolidation test results from 2 test sites near offshore areas were obtained and used to evaluate the correlation parameter for the proposed method. Calculated results using the proposed method showed reasonable agreement with measured results. Additional test sites from the literature were selected and adopted to verify the proposed method. © International Society of Offshore and Polar Engineers.

Kim G.B.,Dongbu Corporation | Pilakoutas K.,University of Sheffield | Waldron P.,University of Sheffield
Magazine of Concrete Research | Year: 2010

A major impediment for the development of precast concrete permanent formwork and other thin structural elements such as cladding is the minimum cover requirement to the reinforcement. For aggressive environments, this can be up to 50 mm, which results in minimum 100 mm thickness units. Currently, glass-fibre-reinforced concrete or cement (GFRC) is used to address that problem in small non-structural elements. However, the structural capacity of GFRC is limited and fibre-reinforced plastic (FRP) reinforcement can be used to structurally reinforce GFRC to enable the development of much larger units. The 'skin and rib' concept for the design of such units has been developed by the authors and has been used for the design of precast units. The main issues relating to GFRPreinforced GFRC are bond, anchoring, tension stiffening, deflections and shear capacity of thin panels. This paper presents experimental and analytical work undertaken to address all the above issues. Pull-out tests confirm that the pull-out resistance of FRP is greater in GFRC than in concrete. Flexural capacity and deformations can be predicted provided the tensile properties of the GFRC are determined and modelled correctly. Finally the shear resistance of the elements is examined and design proposals are made. The work demonstrates that it is possible to develop 1 cm thick GFRC permanent formwork for bridge or building applications - spanning unsupported up to 3.85 m and up to 10 m with intermediate supports, thereby providing a durable and economic alternative to metal decks.

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