Bond Strength Ratio Research Articles

Bond Behavior of Plain Round Bars in Concrete under Complex Lateral Pressures

The bond behavior of reinforcing bars is highly dependent on confinement conditions and is of great importance in the design and analysis of concrete structures. This paper presents an experimental investigation into the bond behavior of plain round bars subjected to uniaxial and biaxial lateral pressures with different pressure ratios. The bond parameters are analyzed with respect to the average lateral pressure. The results show that the residual and ultimate bond strengths increase with the increase of the average lateral pressure, but their ratio stays invariable. The slip at the ultimate bond stress first reduces remarkably, and then increases gradually with an increase in lateral pressure. Compared with lateral pressure, the bar size and the strength of concrete have little influence on the bond strength ratio. Finally, a constitutive model of bond stress-slip with the lateral pressure effect is presented and shown to correlate well with the experimental data for different pressure ratios and levels.

A Study of Basic Properties of Cellulose Ether Modified Dry-Mixed Mortar

In this paper, the quality evaluation indexes of cellulose ether (CE) modified dry-mixed mortar are proposed by the comparison of properties of contrast mortar. The technical indexes of CE modified mortar include water retention, anti-sliding value, time difference of final set and the tensile bond strength ratio which give a good guidance for the application effect evaluation of cellulose used in dry-mixed mortar.

An Optimal Thermo-Hydro-Mechanical Densification (THM) Process for Densifying Balsam Fir Wood

To better utilize low-density softwood, a thermo-hydro-mechanical densification process performed in an open system was studied to enable the manufacture of densified wood with a hard surface, strong bonding, and good dimensional stability. This study was aimed at optimizing three densification parameters, i.e., compression ratio (CR), temperature, and time, for balsam fir (Abies balsamea (L.) Mill.). The Brinell surface hardness, bond strength, and thickness recovery ratio of densified fir were examined. It was found that the optimal densification parameters were a CR of 60%, a temperature of 230 ºC, and a time of 20 minutes. The surface hardness and bond strength of optimized densified fir were about 30 and 8 MPa, respectively. The thickness recovery ratio of the densified fir after a 2-hour cold water soaking and another 2-hour boiling treatment was about 10%. Because the densified fir in this study was used for indoor applications only, its thickness recovery ratio could be minimal under conditions of use.

Global bond behavior of enamel-coated rebar in concrete beams with spliced reinforcement

This paper presents an experimental study of vitreous enamel coating effects on the bond strength between deformed rebar and normal strength concrete. A total of 24 beam splice beam specimens were tested under 4-point loading with four parameters investigated: rebar size, lap splice length, coating and confinement conditions. As the splice length increases, the ratio of bond strength between coated rebar and black rebar was found to increase from 1.0 to a maximum value of 1.44 and decrease to 1.0. The maximum bond strength ratio corresponds to a splice length over rebar diameter ratio of 20–35 when the maximum elastic stress is developed in enamel-coated rebar. For a splice length over rebar diameter ratio of less than 20, an average of 10% bond strength increase was observed due to confinement provided by transverse stirrups.The concrete beams reinforced with enamel-coated rebar have a greater number of smaller flexural cracks than those containing black rebar since the enamel coated rebar can more effectively receives stress from the concrete.

The effect of particle size on the prediction accuracy of screw withdrawal resistance (SWR) models

Density and internal bond extremely used for prediction face and edge screw withdrawal resistance (SWR). Structural parameters (particle size and density) can strongly affect the mechanical properties of particleboard, but up to date the effect of particle size on SWR were not investigated. In the current study, firstly face and edge SWR were predicted by an exponential function based on density and IB strength. In continue, aspect ratio was added to the earlier models to investigate the effect of particle size on accuracy of these models. The results showed that the particle size strongly affect prediction errors. The effect of aspect ratio on face SWR and edge SWR models changed based on dependent variable (face SWR and edge SWR) and main independent variables (density and internal bond strength). Prediction of screw face withdrawal strength as function of density and aspect ratio showed the lowest error percent. The most error percent obtained for face withdrawal strength based on internal bond strength and aspect ratio.

동결토 전단강도를 활용한 동착강도 산정에 관한 연구

동토기반 말뚝기초의 지지력은 말뚝구조물 표면과 주변 토사의 접촉면에서 발현되는 동착강도에 의해 산정되며, 이는 동착-강도가 동토지반 기초설계를 위한 가장 주요한 설계정수임을 의미한다. 동착강도는 토사종류, 동결온도, 말뚝표면에 수직방향으로 작용하는 지중응력, 재하속도, 말뚝구조물의 표면 거칠기 등 다양한 인자들에 동시다발적인 영향을 받는 것으로 보고되고 있다. 1960년대부터 동토지반 기초설계를 위한 동착강도 산정방법들이 제안되어 왔으나, 대부분 동결온도와 말뚝구조물 표면특성에 대한 영향은 고려하고 있는 반면 동착강도의 주요 영향인자 중 하나인 지중응력에 의한 영향을 고려하지 않고 있어 소정깊이 이상의 말뚝기초 설계를 위한 동착강도 산정방법으로 활용되기에는 한계가 있는 것으로 판단된다. 본 연구에서는 동결온도뿐 아니라 지중응력이 동착강도에 미치는 영향을 파악하기 위하여 직접전단시험기를 활용한 동결토 전단강도 및 동착강도 측정실험을 각각 수행하였다. 실험결과 전단강도와 동착강도는 모두 동결온도 조건이 낮아질수록, 혹은 수직응력 조건이 커질수록 증가하는 경향을 보였다. 전단강도와 동착강도의 정량적 관계분석을 위해 정의된 전단강도와 동착강도의 비 <TEX>$r_s$</TEX>는 초기 동결온도에서는 급격하게 감소하는 경향을 나타냈으나, 동결온도가 낮아질수록 증가하며 수렴구간을 형성해가는 경향을 보였다. 본 연구에서는 최종적인 연구결과로서 동결온도 및 수직응력 조건을 바탕으로 결정된 <TEX>$r_s$</TEX>값을 이용하여 동결토의 전단강도로부터 동착강도를 예측할 수 있는 방법을 제안하고 있다. Bearing capacity of pile foundations in cold region is dominated by adfreeze bond strength between surrounding soil and pile perimeter. It denotes that adfreeze bond strength is the most important design parameter for foundations in cold region. Adfreeze bond strength is affected by various factors like 'soil type', 'frozen temperature', 'normal stress acting on soil/pile interface', 'loading rate', 'roughness of pile surface', etc. Several methods have already been proposed to estimate adfreeze bond strength during past 50 years. However, most methods have not considered the effect of normal stress for adfreeze bond strength. In this study, both freezing temperature and normal stress have been controlled as primary factors affecting adfreeze bond strength. A direct shear box was used to measure adfreeze bond strength between sand and aluminum under different temperature conditions. Based on the test results, the relation between shear strength of frozen sand and adfreeze bond strength have been investigated. The test results showed that both of shear strength and adfreeze bond strength tend to increase with decreasing frozen temperature or increasing confining pressure. The ratio of shear strength and adfreeze bond strength, expressed as <TEX>$r_s$</TEX>, decreased initially frozen section but increased at much lower frozen temperature and there were uniform intervals under the different normal stress conditions. A method for predicting adfreeze bond strength using <TEX>$r_s$</TEX> has finally been proposed in this study.

BOND STRENGTH COMPARISON OF THREE CORE BUILD-UP MATERIALS USED TO RESTORE MAXILLARY INCISOR TEETH

Савремени материјали, међународна научна конференција - Contemporary materials, International scientific conference,Савремени материјали 2010 - научна конференција у Бањој Луци

Measurement of Young's Modulus and Poisson's Ratio of Thermal Barrier Coatings

In gas turbines, thermal barrier coatings (TBCs) applied by air plasma spraying are widely used to lower the temperature of hot components. To analyze the characteristics of TBCs such as residual stress, bond strength, fracture toughness, and crack propagation ratio, the Young's modulus and Poisson's ratio are important parameters. For TBC is a brittle and thin film, it is desirable to evaluate those properties while the coatings are bonded to a substrate. An atmospheric plasma spray MCrAlY bond coat and Yttria stabilized zirconia (YSZ) top coat are deposited onto a nickel-base super alloy GH150 substrate. The Young's modulus and Poisson's ratio are measured by cantilever beam bending with NDI. The method will be developed to test the Young's modulus and Poisson ratio of other multilayer systems.

Effect of rebar coating on corrosion resistance and bond strength of reinforced concrete

The objective of this study is to assess the corrosion resistance of zinc-coated and coating effect on the bond strength between concrete and reinforcing steel. Potentiodynamic polarization method was utilized to determine the corrosion rates of carbon steel and zinc in both pH 12 solution and 3.5 wt% NaCl solution. In addition, cylindrical specimens were cast and exposed to 3.5% NaCl solution and a direct current density (0.5 mA/cm 2) was applied to accelerate the corrosion process. Open circuit potential (OCP), direct current polarization resistance were obtained to evaluate the rebar corrosion. Potentiodynamic polarization curves show that the corrosion rate of zinc is higher than carbon steel in pH 12 solution but lower in 3.5% NaCl solution. The bond strength of uncoated rebar is 5–10% less than zinc-coated rebar before aqueous immersion test. The bond strength decreases with an increase in corrosion rate for uncoated rebar and zinc-coated rebar. After 14-days accelerating corrosion process, the reduction ratio of bond strength for zinc-coated rebar is less than uncoated rebar.

引張試験による重ね継手の強度と変形性能

We conducted the test on the assumption of lap splices that are located at the plasticity hinge area in beams under tensile loading. In order to clarify of the structural characteristic of lap splices in the range of plastisity due to rate the individual effect on that, we investigate the following contents: 1) Relationship between failure mode and spliced arrangement 2) The stiffness of spliced members 3) The structural criterion of the splices to ensure the same performance as non-spliced member 4) Resistance mechanism of splices and share of stress in the splices 5) The stress distributions in spliced main bars 6) The. ratio of bond strength in the straight parts of spliced bars to the total strength of splice The effect of the slope of moment in the members and of the compression strut from the bents of the spliced bars to compression zone of the members on the ductility of lap spliced members should be confirmed by supplementary examination.

Local Concrete‐Steel Bond Behavior at Low Temperature

Experimental studies were conducted on the local bond stress‐slip relationships of deformed bars embedded in confined concrete under monotonic and cyclic loading in the temperature range between −10 °C and −70 °C (+14 °F and −94 °F). The bond behavior between steel reinforcement and concrete under low temperature appears quite different from the bond behavior under normal temperature [+20°C(+68°F)]. The main differences observed are in the values of maximum bond stress and in the relationship between maximum bond stress and concrete compressive strength. Under monotonic loading, the ratio of maximum bond strength at low temperature to that at normal temperature is almost identical to the ratio of the respective concrete compressive strength values.

Surface segregation in binary solid solutions: A theoretical and experimental perspective

We review the various theoretical models for predicting the surface segregation of solute in dulute binary substitutional alloys. Two main factors contribute to the driving force for segregation, surface bond breaking and bulk strain energy, and they may be best expressed in terms of the bond strength ratio e* and the atomic size ratio σ* for the solute atom in the solvent matrix. The e*–σ* representation provides a universal mapping of binary solid solutions into regions of the e*–σ* plane with common surface segregation properties. The various theories predict different boundaries in the e*–σ* plane separating the solute segregation and solvent segregation regions. A comparison of theory with experiment is made for 45 bimetallic alloys. General conclusions concerning the validity of the different theories and future theoretical and experimental directions are made.

Bond and strain energy effects in surface segregation: An atomic calculation

A model for predicting the surface segregation of solute in very dilute binary solid alloys is developed. The two main factors contributing to the driving force for segregation are the bond strength ratio ϵ ∗ and size ratio σ ∗ for the solute atom in the solvent matrix. These differences are accounted for implicity by considering various solid solution systems in bulk and surface configurations and by minimizing the total potential energy of the systems (0 K) through atomic relaxation consistent with the assumed long-range, pairwise interactions between the atoms. In previous studies, these two factors have been treated separately in an “ad hoc” manner and the strain energy due to the odd-size solute atom in the solvent lattice has been estimated using various continuum elasticity models. We demonstrate the short-comings of the conventional approach, in particular the failure of the simple continuum elasticity theory to accurately estimate the elastic driving force. We invent the ϵ ∗−σ ∗ representation which greatly facilitates a comparison of the various theories with one another and with experiments, the usefulness of this representation residing in the important finding that the theoretical boundary separating segregation and non-segregation regions depends only on ϵ ∗ and σ ∗. Comparison of our theory with experiment in 31 cases yields 28 correct predictions.

The effect of state of cure on bond performance for an epoxy resin system

A study of the influence of the state and mode of cure of an epoxy resin, diglycidyl ether of bisphenol A cured with 4,4′-diaminodiphenylmethane, has been made. The state of cure was assessed by differential scanning calorimetry as residual heat of reaction and a transition temperature T* corresponding to either the melting point or the glass transition temperature. The state of cure was varied by controlling both the time and temperature of cure. Bond strengths can be related to either Tg or residual heat of reaction, but the different cure schedules produce different relations; simultaneous measurement of both parameters is necessary to specify the state of cure. Some additional work has been carried out on the effect of delayed cure on bond performance and on the effect of varying the cure schedule for a phenol-formaldehyde adhesive. Both single- and double-overlap joints have been used and a constant single/double bond strength ratio has been found. This constant is different for the two adhesives, reflecting their different behavior in shear.

The influence of layer and bond strengths on the ductility of an all beryllium laminate

A limited study has been made of the effect of layer and bond strengths on the longitudinal tensile failure mode of an all beryllium laminate comprising a ductile (∼ 5% elongation), high purity substrate and an adhering, brittle (<1%), layer. It is proposed that the overall ductility is related to the extent of delamination at the interface which, in turn, is determined by the ratio (R) of bond strength to layer strength. When R is 0.23 extensive delamination along the gauge length is obtained resulting in maximum ductility, but at R=0.41 little separation occurs and the elongation is reduced almost to the minimum, namely that of the brittle layer. A simple calculation indicates that for the material used in this work, the influence on ductility of this mode of failure in the brittle condition may begin to be reduced when the layer is <1/3 of the total composite thickness, when multipoint delamination may be anticipated.

1018 モルタルの接着強さと浮き上がり率との関係(材料・施工)

1018 モルタルの接着強さと浮き上がり率との関係(材料・施工)

PHYSICAL PROPERTIES OF ALLOYS USED IN THE TENSION TEST OF WIRE-ROPES

In the tension test of wire-rope, wire-ropes can not be usually inserted between grips, but fusible alloy is used to cover each wire of the wire-rope, so that the rope may break at its middle portion. Such fusible alloys as Pb-Sb-alloys, Wodd's alloy and Pb- Sb-Zn-alloy are usually used.The most important properties of the alloys are: (1) low melting point (2) high bond strength between the wire-rope and alloy and (3) small amount of creep. When creep is not small, there occures plastic deformation of anchor portion of suspension bridges in which wire-ropes are connected with anchor bolts by fusible alloy.Therefore, the writers analyse experimentally the physical properties, i. e. melting point, bond strength and creep. of Pb-Sb-alloy and Pb-Sn-alloy.Bond strength is measured by steel bar (diameter=15.9mm) instead of wire-ropes. Relation between bond strength and mixing ratio of Pb to Sb or Pb to Sn, relation between bond strength and embedded length, and relation between bond strength and surface conditions of steel bar are tested.As for amount of creep of alloys used in this experiment, creep test is not done, so it is obliged to estimate only by stress-strain curve obtained in compression, but this estimation is considered to be correct according to the analysis by one of the writers in near future, creep test will be performed by the writers and the above estimation will be checked.