• Structural Engineering and Mechanics
• /
• 제16권4호
• /
• pp.469-478
• /
• 2003

The primary aim of this study was to investigate the bond strength between reinforcement and concrete. Large sized nine beams, which were produced from concrete with approximately ${f_c}^{\prime}=30$ MPa, were tested. Each beam was designed to include two bars in tension, spliced at the center of the span. The splice length was selected so that bars would fail in bond, splitting the concrete cover in the splice region, before reaching the yield point. In all experiments, the variable used was the reinforcing bar diameter. In the experiments, beam specimens were loaded in positive bending with the splice in a constant moment region. In consequence, as the bar diameter increased, bond strength and ductility reduced but, however, the stiffnesses of the beams (resistance to deflection) increased. Morever, a empirical equation was obtained to calculate the bond strength of reinforcement and this equation was compared with Orangun et al. (1977) and Esfahani and Rangan (1998). There was a good agreement between the values computed from the predictive equation and those computed from equations of Orangun et al. (1977) and Esfahani and Rangan (1998).

• 한국정밀공학회:학술대회논문집
• /
• 한국정밀공학회 2002년도 추계학술대회 논문집
• /
• pp.804-807
• /
• 2002

In general, the reinforcement of a structure is performed with cylinders. In this study, it is attempted to analyze the circular reinforcement with fins. And the maximum stress and deflection is investigated fur the circular reinforcement between two plates. The shape of models are : one which has only circular reinforcements of different diameters and one which has circular reinforcements with fins and one which has fin of same length and circular cylinders of different diameters. And in each model, there are two kinds; one is with upper and lower plates and the other with none. The results shows that the maximum stress is less in the model of circular reinforcement with fins than that in the model without fins. And the maximum stress of a model without upper and lower plate is less than that of a model with plates.

• Computers and Concrete
• /
• 제29권3호
• /
• pp.145-159
• /
• 2022

In this study, the extreme learning machine and deep learning models were devised to estimate the bond strength of corroded reinforcement in concrete. The six inputs and one output were used in this study. The compressive strength, concrete cover, bond length, steel type, diameter of steel bar, and corrosion level were selected as the input variables. The results of bond strength were used as the output variable. Moreover, the Analysis of variance (Anova) was used to find the effect of input variables on the bond strength of corroded reinforcement in concrete. The prediction results were compared to the experimental results and each other. The extreme learning machine and the deep learning models estimated the bond strength by 99.81% and 99.99% accuracy, respectively. This study found that the deep learning model can be estimated the bond strength of corroded reinforcement with higher accuracy than the extreme learning machine model. The Anova results found that the corrosion level was found to be the input variable that most affects the bond strength of corroded reinforcement in concrete.

• 대한치과기공학회지
• /
• 제42권2호
• /
• pp.91-98
• /
• 2020

Purpose: This study is to compare the flexural strength and modulus by inserting a mesh and stick type fiberglass reinforcement into resin specimens. Methods: Wax specimens (length 64 mm, width 39 mm, thickness 5 mm) are prepared according to ISO 20795-1:2013. Mesh type and stick type glass fiber reinforcements were prepared. The prepared wax specimens were used plaster and flask for investment. The flask was separated and the wax was removed. The heat curing resin was injected into the flask, and then a mesh type and stick type fiberglass reinforcement were inserted. The prepared resin specimen was cut into three equal parts (length 64 mm, width 10 mm, thickness 3.3 mm). The mesh type glass fiber reinforcement (MT group) and the stick type glass fiber reinforcement (ST group) were classified into two groups. The prepared specimen was measured using a universal testing machine (UTM). The data were analyzed by Mann-Whitney U test, and the significance level was set to 0.05. Results: In the flexural strength, the ST group was higher than the MT group, and there was a significant difference between the two groups (p<0.05). In the flexural modulus, the ST group was higher than the MT group, and there was a significant difference between the two groups (p<0.05). Conclusion: The stick-type glass fiber inreased the flexural strength than the mesh-type glass fiber reinforcement.

• Structural Engineering and Mechanics
• /
• 제5권4호
• /
• pp.355-368
• /
• 1997

Fiber reinforced plastic (FRP) rods are used as reinforcement (prestressed or not) to concrete. FRP composites can also be combined with steel to form hybrid reinforcing rods that take advantage of the properties of both materials. In order to effectively utilize these rods, their bond behavior with concrete must be understood. The objective of this study is to characterize and model the bond behavior of hybrid FRP rods made with epoxy-impregnated aramid or poly-vinyl alcohol FRP skins directly braided onto a steel core. The model closely examines the split failure of the concrete by quantifying the relationship between slip of the rods resulting transverse stress field in concrete. The model is used to derive coefficients of friction for these rods and, from these, their development length requirements. More testing is needed to confirm this model, but in the interim, it may serve as a design aide, allowing intelligent decisions regarding concrete cover and development length. As such, this model has helped to explain and predict some experimental data from concentric pull-out tests of hybrid FRP rods.

• Advances in concrete construction
• /
• 제14권2호
• /
• pp.79-92
• /
• 2022

The amount and configuration of transverse reinforcement are known as critical parameters that significantly affect the lateral confinement of concrete, the ductility capacity, and the plastic hinge length of RC columns. Based on test results, this study investigated the effect of the three variables on structural indexes such as neutral axis depth, lateral expansion of concrete, and ductility capacity. Five reinforced concrete column specimens were tested under cyclic flexure and shear while simultaneously subjected to a constant axial load. The columns were reinforced by two types of reinforcing steel: rectangular hoops and spiral type reinforcing bars. The variables in the test program were the shape, diameter, and yield strength of transverse reinforcement. The interactive influence of the amount of transverse reinforcement on the structural indexes was evaluated. Test results showed that when amounts of transverse reinforcement were similar, and yield strength of transverse reinforcement was 600 MPa or less, the neutral axis depth of a column with spiral type reinforcing bars was reduced by 28% compared with that of a column reinforced by existing rectangular hoops at peak strength. While the diagonal elements of spiral-type reinforcing bars significantly contributed to the lateral confinement of concrete, the strain of diagonal elements decreased with increases of their yield strength. It was confirmed that shapes of transverse reinforcement significantly affected the lateral confinement of concrete adjacent to plastic hinges. Transverse reinforcement with a yield strength exceeding 600 MPa, however, increased the neutral axis depth of normal-strength concrete columns at peak strength, resulting in reductions in ductility and energy dissipation capacity.

• 대한건축학회논문집:구조계
• /
• 제35권8호
• /
• pp.123-130
• /
• 2019

Recently, it is required to develop a monitoring technology that combines an FBG sensor as a means for continuously monitoring whether reinforcing effect of FRP is maintained on FRP reinforced structural members. However, most existing researches focus on the insertion of FBG sensors into bar-shaped FRPs, and there is insufficient study on the details strip-type FRPs combined with FBG sensors. Therefore, in this paper, it is studied to develop a reinforcement in which a FBG sensor is combined with a FRP strip. Especially, combination of FRP and FBG sensor. For this, a series of experiments were performed to find the adhesive strength of fiber-FRP-epoxy joints, the tensile strength of FBG sensor part with reflection-lattice, and the performance depending on the connection method of FRF and FBG sensor. As a result of the study, it was found that a minimum strength of $216.15N/mm^2$ is required for incorporating FBG sensors in FRP using epoxy. It is considered that the adhesion length of epoxy joints should be more than 50mm. When the FBG sensor is attached to the FRP strip as an epoxy, it is considered appropriate to use the complete attachment and the sensor non-attachment method.

• Geomechanics and Engineering
• /
• 제5권3호
• /
• pp.187-194
• /
• 2013

The most soil anchor works have been concerned with the uplift problem on embedded in non-reinforced soils under pullout test. Symmetrical anchor plates are a foundation system that can be resisting tensile load with the support of around soil in which symmetrical anchor plate is embedded. Engineers and authors proved that the uplift response can be improved by grouping the symmetrical anchor plates, increasing the unit weight, embedment ratio and the size of symmetrical anchor plates. Innovation of geosynthetics in the field of geotechnical engineering as reinforcement materials found to be possible solution in symmetrical anchor plate responses. Unfortunately the importance of reinforcement in submergence has received very little attention by researchers. In this paper, provision of tensile reinforcement under embedded conditions has been studied through uplift experiments on symmetrical anchor plates by few researchers. From the test results it has been showed that the provision of geogrid reinforcement system enhances the uplift response substantially under uplift test although other results are such as increase the ultimate uplift response of symmetrical anchor plate embedded using geosynthetic and Grid Fixed Reinforced (GFR) and symmetrical anchor plate improvement is very dependent on geosynthetic layer length and increases significantly until the amount of beyond that further increase in the layer length does not show a significant contribution in the anchor response.

• KCI Concrete Journal
• /
• 제14권2호
• /
• pp.86-91
• /
• 2002

This paper presents an experimental study to investigate the behavior of mechanical anchorage of reinforcing bars in concrete members. Three kinds of mechanical anchorage which are a kind of headed reinforcements are considered in this study. Total seven specimens were prepared to consider the effects of anchoring methods (Type A, Type B and Type C) and anchorage lengths of the reinforcing bars (14 $d_{b}$, 12 $d_{b}$, 9 $d_{b}$). Pullout tests conforming to ASTM were carried out to assess the effects of several variables on anchoring strength of bars. Based on the test results, it was concluded that the behavior of the specimen anchored by the mechanical anchorage with the anchor-age length of 12 $d_{b}$, is as good as, or better than that of the specimen anchored by 90-degree standard hook.rd hook.

• 한국건축시공학회:학술대회논문집
• /
• 한국건축시공학회 2019년도 추계 학술논문 발표대회
• /
• pp.110-111
• /
• 2019

In ACI 318-19 published recently, the conditions and development length equation to use the headed deformed bars were changed considerably. Although the use of the larger-diameter(No.14 and 18) headed deformed bars isn't yet permitted, the use of the high strength(80,000psi) headed deformed bars is permitted and the effect of bar-diameter($d_b$) on the development length is increased considerably. Therefore, structures using larger-diameter headed deformed bars will be expected to be affected by this code change. We will study the effect of the code change on the development design and find out the design optimization method to minimize the effect of the changed conditions and development length equation.