• Journal of The Korean Association For Science Education
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• v.24 no.5
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• pp.987-995
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• 2004

The purpose of this study was to analyze characteristics of problem solving process with proportional or compensational reasoning of the elementary school students. For this study, 85th grade students were selected and tested with Science Reasoning Task, information processing ability test and proportional and compensational reasoning tasks. This study revealed that students in mid concrete stage could solve the proportionality task and easy compensation task. But, most of the students could not solve difficult compensation task. And as the students got higher score in information processing test, it took them less time to solve the problem. The types of strategy used in solving proportional and compensational problem were categorized as the factor of change, building-up and the cross-product. Most of the students failed in problem solving used incorrect schema knowledge, procedure knowledge and strategy knowledge. Many students tended to use proportionality strategy to solve the difficult compensation task. Result of this study suggested that various task included different structure and the same schema knowledge can be effective for the advancement of students' proportional and compensational reasoning ability.

• Journal of the Korean Geosynthetics Society
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• v.16 no.4
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• pp.211-219
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• 2017

The spray-applied waterproofing membrane is installed on shotcrete or concrete surface to make impermeable layer with 3-5 mm thick for the purpose of waterproofing. This study aims to determine the internal structure of a spray-applied waterproofing membrane including pores by using X-ray CT technique. Before obtaining X-ray images of the membrane specimens, a waterproof performance test was performed on the membrane specimens with a water pressure of 500 kPa for 28 days. Results show that the movement of moisture is made through micropores. This is based on the fact that the large pores inside the membrane are not saturated and the degrees of saturation of the micropores are high. X-ray image is effective for determining the pore size distribution and whether the membrane with pores contains the water However, it is necessary to pay attention to the determination of water content, since water content may vary depending on the threshold value of X-ray image analysis applied to calculate the water content.

• Journal of the Korea institute for structural maintenance and inspection
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• v.20 no.1
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• pp.104-111
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• 2016

The steel frame modular housing of which the research and development has been actively carried out recently cannot be constructed through monolithic placement like the reinforced concrete deck of general structure due to the characteristics of construction method of production in the factory and assembly on the site. And floor vertical vibration and deflection caused by inhabitants' activities may become an important issue in the aspect of usability evaluation due to a decrease in the section size of member, a decrease in weight, and so on. Therefore, this study evaluated the vibration performance of deck by using formula of AISC Design Guide 11(hereinafter AISC formula) which was practically used in general for modules where a stud was and wasn't installed at the center of beam in the longitudinal direction in the modular housing to be studied, and examined the applicability of AISC formula through comparison with the results of analysis using a general-purpose analysis program. On the basis of this, a structural cause for an error to occur between analysis result and AISC formula in the deck of module in which a stud was installed was analysed, and measures for considering this were suggested. Besides, an analysis model with the variables of measures for improving the floor vibration performance of modular housing to be studied was established. And measures having excellent vibration performance and economic feasibility were suggested through vibration response analysis and economic evaluation.

• Journal of the Earthquake Engineering Society of Korea
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• v.13 no.1
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• pp.17-26
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• 2009

The capacity spectrum method (CSM), which is known to be an approximate technique for assessing the seismic capacity of an existing structure, was originally proposed for simple building structures that could be modeled as single-degree-of-freedom (SDOF) systems. More recently, however, CSM has increasingly been adopted for assessing most bridge structures, as it has many practical advantages. Some studies on this topic are now being performed, and a few results of these have been presented as ground-breaking research. However, studies have until now been limited to symmetrical straight bridges only. This study evaluates the practical applicability of CSM to the evaluation of irregular curved bridges. For this purpose, the seismic capacities of 3-span prestressed concrete bridges with different subtended angles subjected to some recorded earthquakes are compared with a more refined approach based on nonlinear time history analysis. The results of the study show that when used for curved bridges, CSM induces higher inelastic displacement responses than the actual values, and that the gap between the two becomes larger as the subtended angle increases.

• Journal of the Earthquake Engineering Society of Korea
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• v.13 no.1
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• pp.35-43
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• 2009

Two types of piloti-type high-rise RC building structures having irregularity in the lower two stories were selected as prototypes, and nonlinear time history analysis was performed using OpenSees to verify the analysis technique and to investigate the seismic capacity of those buildings. One of the buildings studied had a symmetrical moment-resisting frame (BF), while the other had an infilled shear wall in only one of the exterior frames (ESW). A fiber model, consisting of concrete and reinforcing bar represented from the stress-strain relationship, was adapted and used to simulate the nonlinearity of members, and MVLEM (Multi Vertical Linear Element Model) was used to simulate the behavior of the wall. The analytical results simulate the behavior of piloti-type high-rise RC building structures well, including the stiffness and yield force of piloti stories, the rocking behavior of the upper structure and the variation of the axial stiffness of the column due to variation in loading condition. However, MVLEM has a limitation in simulating the abrupt increasing lateral stiffness of a wall, due to the torsional mode behavior of the building. The design force obtained from a nonlinear time history analysis was shown to be about $20{\sim}30%$ smaller than that obtained in the experiment. For this reason, further research is required to match the analytical results with real structures, in order to use nonlinear time history analysis in designing a piloti-type high-rise RC building.

• Journal of the Earthquake Engineering Society of Korea
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• v.14 no.6
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• pp.11-21
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• 2010

This study presents seismic responses of 5-story reinforced concrete structures retrofitted with the buckling-restrained braces using a time-dependent element. The time-dependent element having birth and death times can freely be activated within the user defined time intervals during the time history analysis. The buckling-restrained brace that showed the largest energy dissipation capacity among the test specimens in previous research was used for retrofitting the RC buildings in this study. It was assumed that the first story of the damaged building under the first earthquake was retrofitted with the buckling-restrained braces considered as the time-dependent element before the second of the successive earthquakes occurs. Under this assumption, this paper compares seismic responses of the RC structures with the time-dependent element subjected to the successive earthquake. Subjected to the second earthquake, it was observed that activation of the BRB systems largely decreases deformation of the moment frame where the damage was concentrated under the first earthquake. However, damages to the shear wall systems were increased after activation of the BRB systems. Since the cumulative damages of the shear wall systems were infinitesimal compared with the retrofit effect of the moment frame, the BRB system was effective under the successive earthquake.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.37 no.4
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• pp.705-716
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• 2017

As many environmental pollution problems have arisen, various studies related to the environmental evaluation have been carried out in the construction industry. However, there is no methodology for estimating the environmental load quickly for design alternatives of civil facilities in the design phase. This study aim to establish criteria of works information and designed parts which can efficiently estimate environmental loads of PSC beam bridge based on standard quantity at the early design phase. For this purpose, a detailed environmental loads database was constructed by performing Life Cycle Assessment (LCA) based on detailed design data of 25 bridges. In addition, major work with high impact on environmental load were selected, and the analysis of characteristics of environmental load according to the required materials and 8 impact categories were conducted. As a result, the superstructure accounted for 42.91%. In the superstructure, remicon of the material base and PSC beam work occupied 53.13% and 31.25%. In the substructure, remicon, rebar, and cement, which are material base, accounted for more than 93%. It is expected that this major work and material information for each part of bridge can be utilized in the construction of the model, which can estimate the approximate environmental load, reflecting the characteristics of the structure in the design phase.

• Journal of the Korean Geotechnical Society
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• v.15 no.3
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• pp.161-176
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• 1999

A powerful numerical method that can be used for modeling rock-structure interaction is the Discontinuous Deformation Analysis (D D A) method developed by Shi in 1988. In this method, rock masses are treated as systems of finite and deformable blocks. Large rock mass deformations and block movements are allowed. Although various extensions of the D D A method have been proposed in the literature, the method is not capable of modeling water-block interaction, sequential loading or unloading and rock reinforcement; three features that are needed when modeling surface or underground excavation in fractured rock. This paper presents three new extensions to the D D A method. The extensions consist of hydro-mechanical coupling between rock blocks and steady water flow in fractures, sequential loading or unloading, and rock reinforcement by rockbolts, shotcrete or concrete lining. Examples of application of the D D A method with the new extensions are presented. Simulations of the underground excavation of the \ulcornerUnju Tunnel\ulcorner in Korea were carried out to evaluate the influence of fracture flow, excavation sequence and reinforcement on the tunnel stability. The results of the present study indicate that fracture flow and improper selection of excavation sequence could have a destabilizing effect on the tunnel stability. On the other hand, reinforcement by rockbolts and shotcrete can stabilize the tunnel. It is found that, in general, the D D A program with the three new extensions can now be used as a practical tool in the design of underground structures. In particular, phases of construction (excavation, reinforcement) can now be simulated more realistically.

• Journal of the Korean Geotechnical Society
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• v.29 no.11
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• pp.119-127
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• 2013

Recently, several researches on the development of new economical foundation types have been performed to support floating structures as many offshore structures have been constructed. This study focused on the evaluation of bearing capacity of group suction piles, which are connected by a concrete pile cap. The offshore floating structures are mainly subjected to horizontal loading, so the horizontal bearing capacities of the group suction piles were analyzed by performing 3-dimensional finite element analyses. The group suction piles are expected to behave as a rigid pile due to its shallow embedded depth. Therefore, the detailed soil modeling was necessary to simulate the bearing behavior of soils under low confining pressure. The modulus and the strength of soils were modelled to increase with effective confining pressure in soils. For the parametric study, the center-to-center spacing between piles was varied and two soil types of clay and sands were applied. The analyses results showed that the yielding load of the group pile increased with the increase of the pile spacing and the yielding load of the group piles with 5D spacing was about 3 times larger than that of the single pile with free rotation.

• Journal of the Korea Institute of Building Construction
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• v.14 no.3
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• pp.207-215
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• 2014

As a reinforcement material for RC members, the modified epoxy mortar has been reported one of the superior materials since the material can improve the load capacity and the seismic performance of the RC members. However, there were few experimental studies and analytical research for improving seismic performance with the material. This study is to propose an effective reinforcement plan for RC Ordinary Moment Resisting Frame (OMRF) with the evaluation of seismic performance and economic analysis. For the objective, first, the load-deflection curve of a simple beam specimen was compared with the analytical results. Second, a 5-story RC OMRF structure was designed only for gravity load and the alternatives for seismic reinforcement were suggested. Third, pushover analysis was executed for evaluation of design coefficients and seismic performance of the structures. Finally, an effective reinforcement plan was suggested based on the results of quantity take-off and economic analysis. The findings of this study can be utilized as the basic data when the modified epoxy mortar is applied to practice for improving the seismic performance of RC members.