• Earthquakes and Structures
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• v.8 no.3
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• pp.713-732
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• 2015

The application of the compressive force path method for the design of earthquake-resistant reinforced concrete structural walls with a shear span-to-depth ratio larger than 2.5 has been shown by experiment to lead to a significant reduction of the code specified transverse reinforcement within the critical lengths without compromising the code requirements for structural performance. The present work complements these findings with experimental results obtained from tests on structural walls with a shear span-to-depth ratio smaller than 2.5. The results show that the compressive force path method is capable of safeguarding the code performance requirements without the need of transverse reinforcement confining concrete within the critical lengths. Moreover, it is shown that ductility can be considerably increased by improving the strength of the two bottom edges of the walls through the use of structural steel elements extending to a small distance of the order of 100 mm from the wall base.

• Magazine of the Korean Society of Agricultural Engineers
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• v.43 no.6
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• pp.135-142
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• 2001

Laboratory experiment was performed to evaluate the influence of mixing conditions to the strength of solidified sandy soils with cement. The major physical factors considered in this experiment were the fine particles content(<$\sharp200%$), cement content(%) and water-cement ratio, and unconfined compressive strength test was performed on the samples at 7 and 28 cured day. The results of tests shows that when the cement content is relatively low (7~10 percents) the fine content in the sandy soils is very important, but when cement content is high the water-cement ratio became more important. It was appeared that in the range of the cement content of 7~10 percents, about 20~30 percents of fine content to the total sample weight is the optimum condition to get the maximum strength. In the case of the cement content of 13 percents, the strength of sample was considerably affected by the water-cement ratio rather than the fine content. In this paper, empirical equations were also developed and evaluated to verify the relationship among three factors by the multi-regression analysis.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.5
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• pp.54-59
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• 2020

Coarse aggregate is produced in various ways depending on the location and production method. Currently, the construction industry is in need of a stable supply of coarse aggregate and a way to secure standard quality. The purpose of this study is to examine whether the use of coarse aggregate in 3D printing can help solve this problem. ABS filament was selected for use in 3D printing. CATIA was used for the design of the coarse aggregate, and CUBICON Single Plus was used for the production. Six specimens were produced and cured in water for 28 days. Three of them were made with AE agent, and three were made without it. A compressive strength test confirmed that when the AE agent was used, the compressive strength was greater than the lightweight concrete design criterion specified in the concrete standard specification. This suggests that coarse aggregate produced by a 3D printer may be used for lightweight concrete. A mass production system using this method could help to solve the problems facing the construction industry, such as stable supply and demand for coarse aggregate and securing standard quality.

• Journal of the Korean GEO-environmental Society
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• v.11 no.4
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• pp.5-12
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• 2010

Soil mixture using bentonite as a cutoff material is used a lot for various structures such as landfills, banks and dams as cutoff materials. But seepage water is expected to seep since shear failure of filter layer occurs due to external load, embankment load when constructed. Generally, only coefficient of permeability of Soil Mixture is considered irrespective of the changes of intensity on amount of additives. This research is to study on how the changes of amount of bentonite affects permeability and strength of soil mixture. So successive experiments for measuring permeability and strength were conducted as the amount of bentonite changes from 0 to 4%, mixing with the bed material and then making specimens. Around construction site of B dam. As a result, 2.085E-07 cm/sec was shown when the amount of Soil Mixture was 4%. It is proved that unconfined compressive strength and tensile strength increase as the amount of bentonite increases, but saturation shear strength of bentonite soil mixture from the CD experiment is hardly influenced by the amount of bentonite.

• Explosives and Blasting
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• v.27 no.1
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• pp.32-37
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• 2009

To look over the effect of mixed proportion of cement, sand and water on strength, 162 tests were made for 9 mix proportions. It was observed that strength increased as water in the mixture is reduced. As a result of the control of sand ratio by 50%, the execution strength increased when the sand ratio is raised. Strength was consistent during curing period on each mix proportion, but there were sections where it suddenly increased. Poisson's ratio widely ranged from 0.13 to 0.27, and Young's modulus also broadly ranged from 13.79MPa to 33.25MPa. Poisson's ratio had nothing to do with uniaxial compressive strength, wheras Young's modulus was concerned with it. Young's modulus from theory and experiment showed similar outcome on the 3rd curing day, however, the strength from theory was higher than that from test after 3rd day. In consequence, there was a great change of strength between 3rd and 7th curing day. In addition, it is more efficient to use field strength value between the 3rd and 7th day and to apply Young's modulus on it for determining the exact time.

• Steel and Composite Structures
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• v.23 no.5
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• pp.611-621
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• 2017

This paper presents an investigation on the fire resistance of high strength fiber reinforced concrete filled box columns (CFBCs) under combined temperature and loading. Two groups of full-size specimens were fabricated. The control group was a steel box filled with high-strength concrete (HSC), while the experimental group consisted of a steel box filled with high strength fiber concrete (HFC) and two steel boxes filled with fiber reinforced concrete. Prior to fire test, a constant compressive load (i.e., load level for fire design) was applied to the column specimens. Thermal load was then applied on the column specimens in form of ISO 834 standard fire curve in a large-scale laboratory furnace until the set experiment termination condition was reached. The test results show that filling fiber concrete can improve the fire resistance of CFBC. Moreover, the configuration of longitudinal reinforcements and transverse stirrups can significantly improve the fire resistance of CFBCs.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2006.11a
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• pp.53-56
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• 2006

The objection of this study is to investigate the properties of cement mortar with the kinds and addition of expansive additives. 3 kinds of expansive additives produced in our country and 0, 5, 10, 15, 20% of ratio of addition rate are selected for this experiment. According to experimental results, flow of cement mortar with expansive additives is nearly same with flow of plain mortar and compressive strength, tensile strength, bend strength of cement mortar with expansive additives at 28 days is higher than that of plain mortar.

• Steel and Composite Structures
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• v.11 no.6
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• pp.455-468
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• 2011

Although retrofitting and strengthening reinforced concrete (RC) columns by wrapping fiber reinforced polymer (FRP) composites have become a popular technique in civil engineering, the study on reinforced high-strength concrete (HSC) columns is still not sufficient. The objective of these companion papers is to investigate the mechanical properties of reinforced HSC square columns confined by aramid FRP (AFRP) jackets under concentric compressive loading. In the part I of these companion papers, an experiment was conducted on 54 confined RC specimens and nine unconfined plain specimens, the considered parameters were the concrete strength, the thickness of AFRP jackets, and the form of AFRP wrapping. The experimental process and results are presented in detail. Subsequently, some discussions on the confinement effect, failure modes, strength, and ductility of the columns are carried out.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2023.11a
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• pp.183-184
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• 2023

Considering the actual marine environment construction, this paper monitors the mechanical properties (Flexural, Compressive strength) by exposing alumina cement to seawater. As a result of the experiment, it was confirmed that the strength decreases by about -25% when curing in seawater, but the target strength of the product is met, so it is believed that exposure to the actual marine environment will not be significantly affected.

• Geomechanics and Engineering
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• v.4 no.4
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• pp.281-294
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• 2012

Filtration using granular media such as quarried sand, anthracite and granular activated carbon is a well-known technique used in both water and wastewater treatment. A relatively new pre-filtration method called pebble matrix filtration (PMF) technology has been proved effective in treating high turbidity water during heavy rain periods that occur in many parts of the world. Sand and pebbles are the principal filter media used in PMF laboratory and pilot field trials conducted in the UK, Papua New Guinea and Serbia. However during first full-scale trials at a water treatment plant in Sri Lanka in 2008, problems were encountered in sourcing the required uniform size and shape of pebbles due to cost, scarcity and Government regulations on pebble dredging. As an alternative to pebbles, hand-made clay pebbles (balls) were fired in a kiln and their performance evaluated for the sustainability of the PMF system. These clay balls within a filter bed are subjected to stresses due to self-weight and overburden, therefore, it is important that clay balls should be able to withstand these stresses in water saturated conditions. In this paper, experimentally determined physical properties including compression failure load (Uniaxial Compressive Strength) and tensile strength at failure (theoretical) of hand-made clay balls are described. Hand-made clay balls fired between the kiln temperatures of $875^{\circ}C$ to $960^{\circ}C$ gave failure loads of between 3.0 kN and 7.1 kN. In another test when clay balls were fired to $1250^{\circ}C$ the failure load was 35.0 kN compared to natural Scottish cobbles with an average failure load of 29.5 kN. The uniaxial compressive strength of clay balls obtained by experiment has been presented in terms of the tensile yield stress of clay balls. Based on the effective stress principle in soil mechanics, a method for the estimation of maximum theoretical load on clay balls used as filter media is proposed and compared with experimental failure loads.