• Computers and Concrete
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• v.12 no.5
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• pp.717-737
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• 2013

In this study, experiment and numerical analysis were conducted to identify the heat transfer characteristics and behavior of high-strength concrete upon a fire. The numerical analysis was employed to forecast the characteristics and properties of the high-strength concrete upon a fire, which can not be accomplished through a fire test due to the specific conditions and restrictions associated with the test. The result of the numerical analysis was compared with that of the test to verify the reliability of the analysis. In the numerical analysis of the heat transfer characteristics and behavior of 80 and 100 MPa high-strength concrete upon a fire, the commercial software of ABAQUS(V.6.8) was used. It was observed from the experiment that the contraction of the concrete with fiber-cocktail was mitigated by 25~55 % compared with that without fiber-cocktail because the fiber controlled the heat transfer of the concrete and thus improved the fire-resistance performance of the column.

• Advances in concrete construction
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• v.13 no.3
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• pp.243-254
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• 2022

Reinforced concrete (RC) deep beams are critical structural elements used in offshore pile caps, rectangular cross-section water tanks, silo structures, transfer beams in high-rise buildings, and bent caps. As a result of the low shear span ratio to effective depth (a/d) in deep beams, arch action occurs, which leads to shear failure. Several studies have been carried out to improve the shear resistance of RC deep beams and avoid brittle fracture behavior in recent years. This study was performed to investigate the behavior of RC deep beams numerically and experimentally with different reinforcement arrangements. Deep beams with four different reinforcement arrangements were produced and tested under monotonic static loading in the study's scope. The horizontal and vertical shear reinforcement members were changed in the test specimens to obtain the effects of different reinforcement arrangements. However, the rebars used for tension and the vertical shear reinforcement ratio were constant. In addition, the behavior of each deep beam was obtained numerically with commercial finite element analysis (FEA) software ABAQUS, and the findings were compared with the experimental results. The results showed that the reinforcements placed diagonally significantly increased the load-carrying and energy absorption capacities of RC deep beams. Moreover, an apparent plastic plateau was seen in the load-displacement curves of these test specimens in question (DE-2 and DE-3). This finding also indicated that diagonally located reinforcements improve displacement ductility. Also, the numerical results showed that the FEM method could be used to accurately predict RC deep beams'behavior with different reinforcement arrangements.

• Advances in concrete construction
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• v.9 no.4
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• pp.367-374
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• 2020

Concrete surfaces, industrial floors, sidewalks, roads and parking lots are typically subjected to abrasions. Many studies indicated that the abrasion resistance is directly related to the ultimate strength of the cured concrete. Chemical reactions, freeze-thaw cycles, and damages under abrasion are among many factors negatively affecting the concrete strength and durability. One of the major solutions to address the abrasive resistance of the concrete is to use fibers. Fibers are used in the concrete mix to improve the mechanical properties, strength and limit the crack propagations. In this study, implementation of the steel fibers in concrete to enhance the abrasive resistance of the concrete is investigated in details. The abrasive resistance of the concrete with and without steel fibers is studied with the sandblasting technique. For this purpose, different concrete samples are made with various hooked steel fiber ratios and investigated with the sandblasting method for two different strike angles. In total, 144 ASTM verified cube samples are investigated and it is shown that those samples with the highest steel fiber ratios have the highest abrasive resistance. In addition, the experiments determine that there is a meaningful correlation between the steel fiber percentage in the mix, strike angle and curing time which could be considered for improving structural behavior of the fiber-reinforced concrete.

• Advances in concrete construction
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• v.2 no.3
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• pp.193-207
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• 2014

The study presented herein aims to investigate the durability related properties of rubberized concrete. Two types of waste scrap tire rubber were used as fine and coarse aggregate, respectively. The rubber was replaced with aggregate by three crumb rubber and tire chips levels of 5, 15, and 25% for the rubberized concrete productions. In order to improve the transport properties and corrosion resistance of rubberized concretes, SF was replaced with cement at 10% replacement level by weight of total binder content. The transport properties of the rubberized concretes were investigated through water absorption, gas permeability, and water permeability tests. The corrosion behavior of reinforcing bars embedded in plain and silica fume based rubberized concretes was investigated by linear polarization resistance (LPR) test. The results indicated that the utilization of SF in the rubberized concrete production enhanced the corrosion behavior and decreased corrosion current density values. Moreover, the reduction in the water and gas permeability coefficients was observed by the incorporation of SF in plain and especially rubberized concretes.

• Journal of Ocean Engineering and Technology
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• v.38 no.1
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• pp.30-42
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• 2024

This study examined the jack-up spudcan penetration for a new type of offshore wind substructure newly proposed using the jack-up concept to reduce construction costs. The jack-up spudcan for offshore wind turbines should be designed to penetrate a stable soil layer capable of supporting operational loads. This study evaluated multi-layered soil conditions using centrifuge tests: loose sand over clay and loose sand-clay-dense sand. The penetration resistance profiles of spudcan recorded at the centrifuge tests were compared with the ISO and InSafeJIP methods. In the tests, a spudcan punch-through effect slightly emerged under the sand-over-clay condition, and a spudcan squeezing effect occurred in the clay-over-sand layer. On the other hand, these two effects were not critically predicted using the ISO method, and the InSafeJIP result predicted only punch-through failure. Nevertheless, ISO and InSafeJIP methods were well-matched under the conditions of the clay layer beneath the sand and the penetration resistance profiles at the clay layer of centrifuge tests. Therefore, the ISO and InSafeJIP methods well predict the punch-through effect at the clay layer but have limitations for penetration resistance predictions at shallow depths and strong stratum soil below a weak layer.

• Proceedings of the Korean Geotechical Society Conference
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• 2006.03a
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• pp.1287-1294
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• 2006

A pile is compressed with settlements when loading and bearing capacity is altered along relative displacement of pile/soil on settlement and compression. Settlements of pile displaying limit skin friction is different from displaying tip resistance. Therefore, it is an error in traditional method that bearing capacity of pile is estimated from the sum of limit skin fraction and tip resistance. Accordingly, development of design method considering behavior of load-settlement is needed. In this study, we would like to establish the base for development of design method considering bearing capacity altering along displacement on settlement and compression. For this, we established system and substance of design method. And in order to establish relationship of load-settlement of pile on the type of soil, we analyzed and arranged existing database and pile loading test. On design method, settlement is assumed gradually on each capacity level being assumed gradually. Bearing capacity developing on the pile is obtained on each settlement level. Until the obtained bearing capacity will be equal to assumed capacity, this process is continued with increasing settlement. Load-settlement curve for soil classification is sketched in the process computing settlement on assumed capacity. This design method will be materialized by computation program.

• Journal of the Korea Institute of Building Construction
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• v.21 no.1
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• pp.87-95
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• 2021

In this study, seven companies(A~G) designated as new construction technology selected and evaluated KS F 2622: Method of test for performance evaluation of membrane roofing systems that are similar to field application conditions. As a result of the test, it was confirmed that although all test specimens exceeded KS standards in the basic physical, it was difficult to obtain field quality performance in weak areas such as joints and vertical parts of the adhesive coating method in water-tightness, sagging resistance, swelling resistance tests except for fatigue(crack behavior) tests.

• International Journal of Concrete Structures and Materials
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• v.9 no.2
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• pp.241-254
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• 2015

A lot of reinforced concrete (RC) structures in Syria went out of service after a few years of construction. This was mainly due to reinforcement corrosion or chemical attack on concrete. The use of blended cements is growing rapidly in the construction industry due to economical, ecological and technical benefits. Syria is relatively rich in scoria. In the study, mortar/concrete specimens were produced with seven types of cement: one plain Portland cement (control) and six blended cements with replacement levels ranging from 10 to 35 %. Rapid chloride penetration test was carried in accordance with ASTM C 1202 after two curing times of 28 and 90 days. The effect on the resistance of concrete against damage caused by corrosion of the embedded steel has been investigated using an accelerated corrosion test by impressing a constant anodic potential. The variation of current with time and time to failure of RC specimens were determined at 28 and 90 days curing. In addition, effects of aggressive acidic environments on mortars were investigated through 100 days of exposure to 5 % $H_2SO_4$, 10 % HCl, 5 % $HNO_3$ and 10 % $CH_3COOH$ solutions. Evaluation of sulfate resistance of mortars was also performed by immersing in 5 % $Na_2SO_4$ solution for 52 weeks. Test results reveal that the resistance to chloride penetration of concrete improves substantially with the increase of replacement level, and the concretes containing scoria based-blended cements, especially CEM II/B-P, exhibited corrosion initiation periods several times longer than the control mix. Further, an increase in scoria addition improves the acid resistance of mortar, especially in the early days of exposure, whereas after a long period of continuous exposure all specimens show the same behavior against the acid attack. According to results of sulfate resistance, CEM II/B-P can be used instead of SRPC in sulfate-bearing environments.

• Journal of the Korean Recycled Construction Resources Institute
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• v.8 no.3
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• pp.349-355
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• 2020

The purpose of this study is to investigate the effects of types and amounts of fibers on the compressive strength and tensile behavior high strength fiber-reinforced composites under a static load and impact resistance properties of composites under a high-velocity projectile impact load. Three kinds of mixtures were designed and specimens were manufactured. compressive strength, uniaxial tension, and high velocity projectile impact load tests were performed. Test results showed that the amount of fiber has a greater effect on the tensile strength an d tensile strain capacity than the compressive strength, an d the tensile strain capacity was improved by using hybrid fibers. It was also found that the amount of steel fiber had a great influence on the impact resistance capacity of panels. Although the impact resistance capacity of panels could be improved by using hybrid fibers, the difference of impact resistance capacity between specimens was found to be larger than the case of use of single fiber.

• Journal of Korean Association for Spatial Structures
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• v.23 no.2
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• pp.61-68
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• 2023

A two-hour fire-resistance PC hollow slab for residential use was developed to secure structural and fire-resistance performance and to be applied to the general building and apartment housing markets. Compared to the existing hollow slab, in order to secure the same or better structural performance and economic feasibility by reducing the quantity, it was attempted to secure the fire resistance performance by reducing the concrete filling rate in the cross section and adjusting the thickness of the upper and lower flanges by optimizing the hollow shape in the cross section of the slab. For structural performance evaluation, experiments were performed on PC hollow slabs by varying the member thickness and the presence or absence of overlaid concrete, and all of the experimental results showed that the design strength was sufficiently exhibited and that stability during construction was possible. The developed synthetic PC hollow slab has secured fire resistance and residential performance so that it can be applied to all buildings, and it is intended to be immediately applied to the field.