• Journal of the Korean Society of Safety
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• v.21 no.1 s.73
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• pp.92-95
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• 2006

This study is to find out how column with hole is behaved, compared to the normal one without hole. There might be existing buildings to make holes in the reinforced concrete column. Columns are made with commercially used compressive strength $240kg/cm^{2}$, air amount 5.0%, using re-bar of diameter D13 and D10 having yielding stress $4,000kg/cm^{2}$. The specimen were cured with temperature of $21{\pm}3^{\circ}C$. All specimens of five variables and all holes are geometrically considered and configurated. D3, D5 mean diameter 3cm and 5cm respectively. H1, H2 are the number of holes. Compressive pressure was forced in accordance with KS, following $0.6{\pm}0.4N/mm^{2}$ speed. Main re-bar's were strained with almost same shape through all the specimens. Hole diameter 5cm-having specimen showed cracking around hole. strains of back and front gauges of the specimen were showed similarly. Specimen having two holes in left and right from longitudinally axis resisted 7% less than the one having hole centrically from longitudinal axis. One hole having specimen with diameter 5cm resisted only 3% less than in case of 3cm diameter hole. Hole having in left and right from longitudinal axis will be less resistant than the case longitudinally arranged. Diameter 3cm hole showed less 10% capacity than normal one without hole. Capacity loss difference between diameter 3cm and 5cm showed almost none in case that they are arranged longitudinally.

• Journal of the Korea institute for structural maintenance and inspection
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• v.16 no.1
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• pp.1-8
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• 2012

Since the cement industry is expected to face serious setbacks in the near future associated with environmental concerns. With the advent of new technologies and increased public awareness about global environmental issues, the cement industry is actively seeking to adopt new technologies as part of an effort to diversity its resources. This study is designed to assess the fundamental properties of zeolite cement concrete which consists mainly of natural zeolite, which is known for removal of and harmful gas, ion exchange capacity removing cation contaminant including heavy metals and ammonia, absorptive capacity and molecular sieving effect together with excellent insulation capacity as a porous material, and recently draws much attention for its possibility as an alternative material to cement. The study was conducted to show the compressive strength of concrete, slump, bleeding and air volume according to the changes of natural zeolite and alkali activator(NaOH). As a result of measuring the compressive strength of natural zeolite concrete, it was almost 40MPa and displayed similar to general concrete in the tests of slump, bleeding and air volume, with which it was considered that it may be used as a future high performance, high performance construction material.

• Journal of the Earthquake Engineering Society of Korea
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• v.2 no.1
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• pp.11-21
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• 1998

During an earthquake, there are three main components of excitation : horizontal excitation of the ground, vertical excitation of the pile due to superstructure feedback produced by vertical excitation of the ground, and the seawater excitation induced by the vertical ground shaking, that is, "the seaquake." These excitations could have effects on the soil plugs in open-ended pie piles installed at offshore sites. In this study, seaquake excitation induced by the vertical ground shaking was simulated by pulsing the water pressure at the seabed. During a seaquake, due to the induced excess porewater pressure and pressure gradients in the soil, the capacity of open-ended pipe piles installed in a simulated sea depth of greate than 220 m was reduced serevely and the soil plugging resistance was degraded by more than 80% The soil plug was failed because of eh upward seepage forces that developed in the soil plug due to excess pore water pressure produced in the bottom of the soil plug during the seaquake, The compressive capacity of ar open-ended pile in a simulated sea depth of less than 220 m was reduced only by about 10% and the soil plug resistance was degraded by less than 5%.s than 5%.

• Journal of the Korean Recycled Construction Resources Institute
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• v.7 no.2
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• pp.158-165
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• 2019

The purpose of this study is to investigate analytically the flexural behavior of beam reinforced by an alkali-activated slag-based fiber-reinforced composite. The materials and mixture proportion were selected to manufacture an alkali-activated slag-based fiber-reinforced composite with high tensile strain capacity over 7% and compressive strength and tension tests were performed. The composite showed a compressive strength of 32.7MPa, a tensile strength of 8.43MPa, and a tensile strain capacity of 7.52%. In order to analyze the flexural behavior of beams reinforced by ultra-high-ductile composite, nonlinear sectional analysis was peformed for four types of beams. Analysis showed that the flexural strength of beam reinforced partially by ultra-high-ductile composite increased by 8.0%, and the flexural strength of beam reinforced fully by ultra-high-ductile composite increased by 24.7%. It was found that the main reason of low improvement in flexural strength is the low tensile strain at the bottom of beam. The tensile strain at bottom corresponding to the flexural strength was 1.38% which was 18.4% of tensile strain capacity of the composite.

• Steel and Composite Structures
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• v.30 no.5
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• pp.405-416
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• 2019

Profiled composite slab has been widely used in civil engineering due to its structural merits. The extension of this concept to the bearing wall forms the profiled composite wall, which consists of two external profiled steel plates and infill concrete. This paper investigates the structural behavior of this type of wall under axial compression. A series of compression tests on profiled composite walls consisting of varied types of profiled steel plate and edge confinement have been carried out. The test results are evaluated in terms of failure modes, load-axial displacement curves, strength index, ductility ratio, and load-strain response. It is found that the type of profiled steel plate has influence on the axial capacity and strength index, while edge confinement affects the failure mode and ductility. The test data are compared with the predictions by modern codes such as AISC 360, BS EN 1994-1-1, and CECS 159. It shows that BS EN 1994-1-1 and CECS 159 significantly overestimate the actual compressive capacity of profiled composite walls, while AISC 360 offers reasonable predictions. A method is then proposed, which takes into account the local buckling of profiled steel plates and the reduction in the concrete resistance due to profiling. The predictions show good correlation with the test results.

• Structural Engineering and Mechanics
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• v.85 no.1
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• pp.65-80
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• 2023

To explore the effect of Engineered Cementitious Composite (ECC) on improving the progressive collapse resistance of reinforced concrete frames under a middle column removal scenario, six beam-column substructures were tested by quasistatic vertical loading. Among the six specimens, four were ECC-concrete composite specimens consisting of different depth of ECC at the bottom or top of the beam and concrete in the rest of the beam, while the other two are ordinary reinforced concrete specimens with different concrete strength grades for comparison. The experimental results demonstrated that ECC-concrete composite specimens can improve the bearing capacity of a beam-column substructure at the stages of compressive arch action (CAA) and catenary action in comparison with ordinary concrete specimen. Under the same depth of ECC, the progressive collapse resistance of a specimen with ECC at the beam bottom was superior to that at the beam top. With the increase of the proportion of ECC arranged at the beam bottom, the bearing capacity of a composite substructure was increased, but the increase rate slows down with the proportion. Meanwhile, the nonlinear numerical analysis software MSC Marc was used to simulate the whole loading process of the six specimens. Theoretical formulas to calculate the capacities of ECC-concrete composite specimens at the stages of flexural action, CAA and catenary action are proposed. Based on the research results, this study suggests that ECC should be laid out at the beam bottom and the layout depth should be within 25% of the total beam depth.

• Journal of the Korea institute for structural maintenance and inspection
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• v.21 no.3
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• pp.69-75
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• 2017

Ultra-high performance concrete and high ductile cementless composite are considered as promising construction materials because those exhibits higher performance in terms of high strength and high ductility. The purpose of this study is to investigate experimentally the compressive strength and tensile behavior of ultra-high performance concrete and high ductile cementless composite. A series of experiments including density, compressive strength, and uniaxial tension tests were performed. Test results showed that the compressive strength and tensile strength of alkali-activated slag based high ductile cementless composite were lower than those of ultra-high performance concrete. However, the tensile strain capacity and toughness of alkali-activated slag based high ductile cementless composite were higher than those of ultra-high performance concrete. And it was exhibited that a high ductility up to 7.89% can be attainable by incorporating polyethylene fiber into the alkali-activated slag based cementless paste.

• Advances in concrete construction
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• v.11 no.4
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• pp.335-345
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• 2021

It is known from the literature that there are relatively few studies on the engineering properties of ultra-high performance concrete (UHPC) in early age. In fact, in order to ensure the safety of UHPC during construction and sufficient durability and long-term performance, it is necessary to explore the early behavior of UHPC. The test parameters (test control factors) investigated included the percentage of cement replaced by silica fume (SF), the percentage of cement replaced by ultra-fine silica powder (SFP), the amount of steel fiber (volume percent), and the amount of polypropylene fiber (volume percentage). The engineering properties of UHPC in the fresh mixing stage and at the age of 7 days were investigated. These properties include freshly mixed properties (slump, slump flow, and unit weight) and hardened mechanical properties (compressive strength, elastic modulus, flexural strength, and splitting tensile strength). Moreover, the effects of the experimental factors on the performance of the tested UHPC were evaluated by range analysis and variance analysis. The experiment results showed that the compressive strength of the C8 mix at the age of 7 days was highest of 111.5 MPa, and the compressive strength of the C1 mix at the age of 28 days was the highest of 128.1 MPa. In addition, the 28-day compressive strength in each experimental group increased by 13%-34% compared to the 7-day compressive strength. In terms of hardened mechanical properties, the performance of each experimental group was superior to that of the control group (without fiber and without additional binder materials), with considerable improvement, and the experimental group did not produce explosive or brittle damage after the test. Further, the flexural test process found that all test specimens exhibited deflection-hardening behavior, resulting in continued to increase carrying capacity after the first crack.

• Magazine of the Korea Concrete Institute
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• v.6 no.6
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• pp.190-198
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• 1994

Th~s paper presents the shear behavior in reinforced normal, medium and high strength con crete beams due to the Increase of concrete compressive strength. Twelve shear tests were con ducted on full scale beam speclrnerls havmg concrete compressive stlengths of 360, 670 and 873kg/$cm^2$. Different amounts of shear reinforcement as a variable were investigated according to ACI 318 89. The shear responses are discussed in terms of the shear capacity. the ductility and the reserved strength. The prediction and comparison with the test results are also presented.

• International Journal of Concrete Structures and Materials
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• v.9 no.2
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• pp.207-217
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• 2015

The influence of powdered and colloidal nano-silica (NS) on the mechanical properties of cement mortar has been investigated. Powdered-NS (~40 nm) was synthesized by employing the sol-gel method and compared with commercially available colloidal NS (~20 nm). SEM and XRD studies revealed that the powdered-NS is non-agglomerated and amorphous, while colloidal-NS is agglomerated in nature. Further, these nanoparticles were incorporated into cement mortar for evaluating compressive strength, gel/space ratio, portlandite quantification, C-S-H quantification and chloride diffusion. Approximately, 27 and 37 % enhancement in compressive strength was observed using colloidal and powdered-NS, respectively, whereas the same was up to 19 % only when silica fume was used. Gel/space ratio was also determined on the basis of degree of hydration of cement mortar and it increases linearly with the compressive strength. Furthermore, DTG results revealed that lime consumption capacity of powdered-NS is significantly higher than colloidal-NS, which results in the formation of additional calcium-silicate-hydrate (C-S-H). Chloride penetration studies revealed that the powdered-NS significantly reduces the ingress of chloride ion as the microstructure is considerably improved by incorporating into cement mortar.