• Structural Engineering and Mechanics
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• v.67 no.4
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• pp.347-358
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• 2018

The main aim of this research was to investigate the shear strength of non-prismatic steel fiber reinforced concrete beams under monotonic loading considering different parameters. Experimental program included tests on fifteen non-prismatic reinforced concrete beams divided into three groups. For the first and the second groups, different parameters were taken into consideration which are: steel fibers content, shear span to minimum depth ratio ($a/d_{min}$) and tapering angle (${\alpha}$). The third group was designed mainly to optimize the geometry of the non-prismatic concrete beams with the same concrete volume while the steel fiber ratio and the shear span were left constant in this group. The presence of steel fibers in concrete led to an increase in the load-carrying capacity in a range of 10.25%-103%. Also, the energy absorption capacity was increased due to the addition of steel fibers in a range of 18.17%-993.18% and the failure mode was changed from brittle to ductile. Tapering angle had a clear effect on the shear strength of test specimens. The increase in tapering angle from ($7^{\circ}$) to ($12^{\circ}$) caused an increase in the ultimate shear capacity for the test specimens. The maximum increase in ultimate load was 45.49%. The addition of steel fibers had a significant impact on the post-cracking behavior of the test specimens. Empirical equation for shear strength prediction at cracking limit state was proposed. The predicted cracking shear strength was in good agreement with the experimental findings.

• Advances in concrete construction
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• v.11 no.2
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• pp.151-161
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• 2021

The major shortcoming of concrete in most of the applications is its high self-weight and thermal conductivity. The emerging trend to overcome these shortcomings is the use of foam-concrete, which is a lightweight concrete consisting of cement, filler, water and a foaming agent. This study aims at the development of a cost-effective high-volume fly-ash foam-concrete insulation wall cladding for existing buildings using natural fiber like rice straw in different proportions. The paper reports the results of systematic studies on various mechanical, acoustic, thermal and durability properties of foam-concrete with and without replacement of cement by fly-ash. Fly-ash replaces 60 percent by weight of cement in foam-concrete. The water-solid ratio of 0.3, the filler ratio of 1:1 by weight, and the density of 1100 kg/㎥ (approx.) are fixed for all the mixes. Rice straw at 1%, 3% and 5% by weight of cement was added to improve the thermal and acoustic efficiency. From the investigations, it was inferred that the strength properties were increased with fly-ash replacement up to 1% rice straw addition. In furtherance, addition of rice straw and fly-ash resulted in improved acoustic and thermal properties.

• Proceedings of the Korea Concrete Institute Conference
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• 1999.04a
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• pp.307-312
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• 1999

The purpose of this study is to ascertain the strength properties of water-permeable concrete with redispersible polymer powder, silica fume and polypropylene fibers. The water-permeable concrete using rediapersibel polymer powder with a water-cement ratio of 25%, polymer-cement ratios of 0 to 10%, silica fume contents of 0 to 10% and fiber contents of 0 to 1.5% are prepared, and tested for flexural strength, compressive strength and water permeability. From the test results, improvements in the strength properties of the water-permeable concrete due to the addition of the redispersible polymer powder, silica fume and fibers are discussed. It is concluded from the test results that the superior flexural and compressive strengths of water-permeable concretes are obtained at a propylene fiber content of 1.0% with a void filling ratio of 50%. And, the water-permeable concrete having a flexural strength of 15.6~28.4kgf/$\textrm{cm}^2$, a compressive strength of 63.5~120.6kgf/$\textrm{cm}^2$, and a coefficient of permeability of 1.14~1.70cm/s at a void filling ratio of 30% can be prepared. Also water-permeable concrete having a flexural strength of 35.6~57.9kgf/$\textrm{cm}^2$, a compressive strength of 164.0~290.0kgf/$\textrm{cm}^2$, and a coefficient of permeability of 0.19~1.04cm/s at a void filling ratio of 50% can be prepared in the consideration of the mix proprotioning factors.

• Steel and Composite Structures
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• v.48 no.5
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• pp.599-610
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• 2023

To avoid debonding failure, a novel type of hybrid anchorage (HA) is proposed in this study that uses a slotted plate to lock the ends of the fiber-reinforced polymer (FRP) sheet in addition to the usual bonding over the substrate of the strengthened member. An experimental investigation was performed on three groups of RC beams, which differed from one another in either concrete strength or steel reinforcement ratio. The test results indicate that the end self-locking of the CFRP sheet can improve the failure ductility, ultimate capacity of the beams and its utilization ratio. Although intermediate debonding occurred in all the strengthened beams, it was not a fatal mode of failure for the three specimens with end anchorage. Among them, FRP rupture occurred in the beam with higher concrete strength and lower steel reinforcement ratio, whereas the other two failed by concrete crushing. The beam strengthened by HA obtained a relatively high percentage of increase in ultimate capacity when the rebar ratio or concrete strength decreased. The expressions in the literature were inspected to calculate the critical loads at intermediate debonding, FRP rupturing and concrete crushing after debonding for the strengthened beam. Then, the necessity of further research is addressed.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.32 no.1A
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• pp.55-64
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• 2012

Experimental investigation on the structural behavior of steel fiber-reinforced ultra high performance concrete (UHPC) beams subjected to shear are presented. Six tests carried out on simply supported I-beams under concentrated loads are presented. The parameters varied were the volume fraction of the fibers (1.0, 1.5 and 2.0%) and shear span-effective depth ratio (2.5, 3.4). The test results indicated that ultimate shear strength increased with increasing fiber volume, and that ultimate shear strength decreased with increasing shear span-effective depth ratio. In addition, applicability of predictive equations for evaluating the ultimate shear strength of steel fiber-reinforced UHPC beams are estimated based on the test results. The comparison between computed values and the experimentally observed values are shown to validate the proposed theoretical equations. It is found that predictions by using AFGC and JSCE recommendations provide the most accurate estimates of shear strength of steel fiber-reinforced UHPC beams.

• Journal of Korean Society of Steel Construction
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• v.26 no.6
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• pp.499-509
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• 2014

This study focuses on mixing steel fiber in the concrete to improve the ductility and toughness of the columns. The purpose of the study is to evaluate the load capacity and deformation capacity associated with the amount of steel fiber and loading condition and to analyze the interplay between the steel fiber reinforced concrete and the welding built-up square tube in terms of structure and fire resistance performance. Reinforcement of concrete with steel fiber(Vf=0.375%), when cross-section shape and boundary condition (load ratio) remained unchanged, improved fire resistance performance by 1.1~1.3 times. It is deemed that the area resisting thermal load increased and fire resistance performance was improved since the concrete reinforced with steel fiber restrained cracking. In addition, the fact that the cross-sections of the concrete were barely damaged indicates that load share capacity was greatly improved.

• Journal of Nutrition and Health
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• v.39 no.6
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• pp.549-559
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• 2006

The present study determined the estimated dietary fiber (DF) intake per capita of Korean from 1991 to 2001 and analyzed the major food sources of dietary fiber for Korean using the data on per capita consumption of each food reported in the Korean National (Health and) Nutrition Survey Reports and the recently established DF database by the Korean Nutrition Society. The estimated mean daily DF intakes of Korean during the last 11 years $(1991{\sim}2001)$ were in the range of $19.25{\sim}21.22\;g\;or\;9.97{\sim}11.99\;g/1,000\;kcal$ with a small range of fluctuations. As of 2001, average DF intake per capita of Korean was estimated as 20.92 g or 10.59 g/1,000 kcal. The average DF intake level was under the Adequate Intake for DF (12 g per 1,000 kcal) of the Dietary Reference Intakes (DRIs) for Koreans established in 2005. The level of DF intake was relatively lower in small city residents compared to the large city or rural area. The top two major food group sources of DF for Korean were vegetables and cereals, in addition, legumes, fruits, seaweeds and seasonings were included among top five food groups. The ratio of DF intake from fruits was gradually increased but the ratio from legumes was steadily decreased during the last 11 years. The mostly contributed single foods for DF intakes of Korean were Kimchi and rice regardless of year and area. Percentage of DF intake from top ten single foods was continuously decreased from 65% in 1991 to 51 % in 2001. The results of this study revealed that DF intakes of Korean as of 2001 is insufficient compared to the Adequate Intake for DF for Korean and the source of fiber in Korean diet has been more various. Therefore the beneficial health effects of DF and the increased consumption of DF from a variety of food sources should be continuously emphasized through the nutritional education.

• Textile Coloration and Finishing
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• v.35 no.1
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• pp.20-28
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• 2023

In this study, TPU resin for coating was prepared by varying the mixing ratio of antistatic TPU and recycled TPU to manufacture permanent antistatic materials. The coated yarn was prepared by coating on the nylon yarn, and then the thermal, rheological, mechanical properties and antistatic properties were analyzed. In addition, antistatic properties and durability were confirmed after manufacturing UD fabrics using coated yarns. The mixing ratio of antistatic TPU and recycled TPU was most appropriate at 4:6, and the antistatic property had a surface resistance of 2.20 × 10⁹ Ω and a static charge of 398 V. In the coating process, the coating speed was most appropriate at 0.21 m/s, and the surface resistance of the UD fabric manufactured with the coated yarn manufactured under this condition was 6.80 × 10⁹ Ω and the static charge was 484 V. The UD fabric had a surface resistance of 7.21 × 10⁹ Ω and a static charge of 517 V after washing 10 times, and it was confirmed that the permanent antistatic property was excellent.

• Fashion & Textile Research Journal
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• v.12 no.4
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• pp.500-507
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• 2010

In this study, physical properties were studied by using latent stretching yarn in order to develop the texturing yarn technique for super bulky yarn, which is better in bulkiness and handle than natural wool and also adds property of synthetic fiber to natural wool. In order to obtain textured conditions by analysing basic properties for manufacturing DTY yarn with super bulky property, DTY 50d/12 after spinning latent yarn spined POY 80d/12 was obtained under the two conditions of (i) false twist(T/M) level 3 in DTY texturing and (ii) draw ratio level 4 in draw texturing. For DTY texturing yarn, Elongation rate increased as the heat treatment time and temperatures increased. In addition, shrinkage became higher as false twist was higher, so that elongation rate became lower. When annealing became longer in time and higher in temperature, initial modulus increased. In addition, as the count of false twist increased, the initial modulus showed higher values. For draw texturing yarn, under the conditions of heat temperature 180 and heating time 30 minutes, shrinkage rate in draw ratio 1.55 and 1.6 draw ratio was 7%, and that in 1.65 and 1.7 draw ratio was 8.5%. High draw ratio samples' tenacity was much influenced by heating time and temperature, but low draw ratio samples' tenacity was influenced not by treated time, but by treated temperature.

• Advances in concrete construction
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• v.15 no.6
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• pp.405-417
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• 2023

While ultra-high performance concrete (UHPC) is commonly reinforced with micro straight steel fibers in existing applications, studies have indicated that the use of deformed steel macro-fibers leads to enhanced ductility and post-peak responses for UHPC structural elements, which is of particular importance for earthquake-resistant structures. However, there are potential concerns regarding the use of UHPC reinforced with macro-fibers due to the issues of workability and fiber distribution. The objective of this study was to address these issues by extensively investigating the restricted and non-restricted deformability, filling ability, horizontal and vertical velocities, and passing ability of UHPC containing macro hooked-end steel fibers. A new approach is suggested to examine the homogeneity of fiber distribution in UHPC. The influences of ultra-fine fillers and steel macro-fibers on the workability of fresh UHPC and the mechanics of hardened UHPC were examined. It was found that although increasing the ratio of quartz powder to cement led to an improvement in the workability and tensile strain hardening behavior of UHPC, it reduced the fiber distribution homogeneity. The addition of 1% volume fraction of macro-fibers in UHPC improved workability, but reduced its compressive strength, which is contrary to the effect of micro-fiber inclusion in UHPC.