• Magazine of the Korea Concrete Institute
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• v.11 no.1
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• pp.191-200
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• 1999

The shear behavior of simply supported reinforced concrete deep beams subject to concentrated loads has been scrutinized experimentally to verify the influence of the structural parameters such as concrete strength, shear span-depth ratio, and web reinforcements. A total of 42 reinforced concrete deep beams with compressive strengths of 250 kg/$cm^2$ and 500 kg/$cm^2$ has been tested at the laboratory under one or two-point top loading. The shear span-depth ratio have been taken as three types of 0.4, 0.8 and 1.2, and the horizontal and vertical shear reinforcements ratio, ranging from 0.0 to 0.57 percent respectively. In the tests, the effects of the shear span-depth ratio, concrete strength and web reinforcements on the shear strength and crack initiation and propagation have been carefully checked and analyzed. From the tests, it has been observed that the failures of all specimens were due to shear and the shear behaviors of specimens were greatly affected by inclined cracks from the load application points to the supports in shear span. The load bearing capacities have changed significantly depending on the shear span ratio, and the efficiency of horizontal shear reinforcements were increased as the shear span-depth ratio decreased. The test results have been analyzed and compared with the formulas proposed by previous researchers and the design equation from the code. While the shear strengths obtained from the tests showed around 1.4 and 1.9 times higher than the values calculated by CIRIA guide and the domestic code, they were closely coincident with the formulas given by de Paiva's equation.

• Structural Engineering and Mechanics
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• v.5 no.6
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• pp.729-741
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• 1997

Cracked reinforced concrete in compression has been observed to exhibit lower strength and stiffness than uniaxially compressed concrete. The so-called compression softening effect responsible is thought to be related to the degree of transverse cracking and straining present. It significantly affects the strength, ductility and load-deformation response of a concrete element. A number of experimental investigations have been undertaken to determine the degree of softening that occurs, and the factors that affect it. At the same time, a number of diverse analytical models have been proposed by various this behavior. In this paper, the softened truss model thoery for low-rise structural shearwalls is employed using the principle of the stress and strain transformations. Using this theory the softening parameters for the concrete struts proposed by Hsu and Belarbi as well as by Vecchio and Collins are examined by 51 test shearwalls available in literature. It is found that the experimental shear strengths and ductilities of the walls under static loads are, in average, very close to the theoretical values; however, the experiment shear strengths and ductilities of the walls under dynamic loads with a low (0.2 Hz) frequency are generally less than the theoretical values.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.33 no.6
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• pp.411-417
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• 2009

The transient shear stress response of an electrorheological fluid is investigated experimentally. The characteristic time constants of an electrorheological fluid sheared between two concentric cylinders were obtained under various electric field strengths and shear rates. Also, two experimental modes are adopted to investigate the effect of the shear flow on the dynamic behavior of the fluid; one is that the electric field is induced before shearing, and the other is the electric field is induced after shearing. From the difference in the response time between two modes, the cluster formation time were obtained. The response times were decreased with the increase of the shear rate, irrelatively of the electric field strength. The cluster formation time were monotonically increased with increase of shear rate, and thereafter, were converged with a certain value.

• Geomechanics and Engineering
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• v.35 no.2
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• pp.209-219
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• 2023

This paper presents numerical investigations into the particle crushing effect on the shear properties of gravel under direct shear condition. A novel particle crushing model was developed based on the octahedral shear stress criterion and fragment replacement method. A series of direct shear tests were carried out on unbreakable particles and breakable particles with different strengths. The evolutions of the particle crushing, shear strength, volumetric strain behavior, and contact force fabric during shearing were analyzed. It was observed that the number of crushed particles increased with the increase of the shear displacement and axial pressure and decreased with the particle strength increasing. Moreover, the shear strength and volume dilatancy were obviously decreased with particle crushing. The shear displacement of particles starting to crush was close to that corresponding to the peak shear stress got. Besides, the shear-hardening behavior was obviously affected by the number of crushed particles. A microanalysis showed that due to particle crushing, the contact forces and anisotropy decreased. The mechanism of the particle crushing effect on the shear strength was further clarified in terms of the particle friction and interlock.

• The korean journal of orthodontics
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• v.25 no.2 s.49
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• pp.223-233
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• 1995

The purpose of this study was to evaluate the effects of surface conditioning with $10\%$ polyacrylic acid, etching with $38\%$ phosphoric acid, and polishing with a slurry of pumice on shear bond strengths of light-cured glass ionomer cement, chemically cured glass ionomer cement, and a composite resin to enamel, and to observe the failure patterns of bracket bondings. Shear bond strengths of glass ionomer cements were compared with that of a composite resin. Metal brackets were bonded on the extracted human bicuspids after enamel surface treatments, and samples were immersed in the $37^{\circ}C$ distilled water bath, and shear bond strengths of glass ionomer cements and a composite resin were measured on the Instron machine after 24hrs passed, and the deboned samples were measured in respect of adhesive remnant index. Scanning electron micrographs were taken of enamel surfaces after various treatments. The data were evaluated and tested by ANOVA and Duncan's multiple range test, and those results were as follows. 1. Shear bond strength of light-cured glass ionomer cement showed statistically higher than that of chemically cured glass ionomer cement. 2. Shear bond strengths of light-cured and chemically cured glass ionomer cements to enamel treated with $10\%$ polyacrylic acid and $38\%$ phosphoric acid showed statistically higher than those with a slurry of pumice. 3. According to scanning electron micrographs, enamel surface conditioned with $10\%$ polyacrylic acid is slightly etched and cleaned, that etched with $38\%$ phosphoric acid is severely etched, and that polished with a slurry of pumice is irregulary scretched and not completely cleaned. 4. After debonding, light-cured glass ionomer cement to enamel treated with $10\%$ polyacrylic acid showed less residual materials on the enamel solace than composite resin to enamel etched with $38\%$ phosphoric acid. 5. There was no significant difference in the shear bond strength of light-cured glass ionomer cement to enamel treated with $10\%$ polyacrylic acid and that of composite resin to enamel etched with $38\%$ Phosphoric acid.

• The Journal of Advanced Prosthodontics
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• v.1 no.1
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• pp.41-46
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• 2009

STATEMENT OF PROBLEM. The poor chemical bonding of a denture base resin to cast titanium framework often introduces adhesive failure and increases microleakage. PURPOSE. This study evaluated the shear bond strengths of a heat cure denture base resin to commercially pure titanium, Ti-6Al-4V alloy and a cobalt-chromium alloy using two adhesive primers. MATERIAL AND MATHODS. Disks of commercially pure titanium, Ti-6Al-4V alloy and a cobalt-chromium alloy were cast. Specimens without the primer were also prepared and used as the controls. The shear bond strengths were measured on a screw-driven universal testing machine. RESULTS. The primers significantly(P < .05) improved the shear bond strengths of the heat cure resin to all metals. However, the specimens primed with the Alloy $primer^{(R)}$(MDP monomer) showed higher bond strength than those primed with the MR $bond^{(R)}$(MAC-10 monomer) on titanium. Only adhesive failure was observed at the metal-resin interface in the non-primed specimens, while the primed specimens showed mixed failure of adhesive and cohesive failure. CONCLUSIONS. The use of appropriate adhesive metal primers makes it possible not only to eliminate the need for surface preparation of the metal framework before applying the heat cure resins, but also reduce the need for retentive devices on the metal substructure. In particular, the Alloy $primer^{(R)}$, which contains the phosphoric acid monomer, MDP, might be clinically more acceptable for bonding a heat cure resin to titanium than a MR $bond^{(R)}$, which contains the carboxylic acid monomer, MAC-10.

• Structural Engineering and Mechanics
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• v.73 no.2
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• pp.143-152
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• 2020

Deep coupling beams are more prone to suffer brittle shear failure. The addition of steel fibers to seismic members such as coupling beams can improve their shear performance and ductility. Based on the test results of steel fiber reinforced concrete(SFRC) coupling beams with span-to-depth ratio between 1.5 and 2.5 under lateral reverse cyclic load, the shear mechanism were analyzed by using strut-and-tie model theory, and the effects of the span-to-depth ratio, compressive strength and volume fraction of steel fiber on shear strengths were also discussed. A simplified calculation method to predict the shear capacity of SFRC deep coupling beams was proposed. The results show that the shear force is mainly transmitted by a strut-and-tie mechanism composed of three types of inclined concrete struts, vertical reinforcement ties and nodes. The influence of span-to-depth ratio on shear capacity is mainly due to the change of inclination angle of main inclined struts. The increasing of concrete compressive strength or volume fraction of steel fiber can improve the shear capacity of SFRC deep coupling beams mainly by enhancing the bearing capacity of compressive struts or tensile strength of the vertical tie. The proposed calculation method is verified using experimental data, and comparative results show that the prediction values agree well with the test ones.

• Restorative Dentistry and Endodontics
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• v.30 no.4
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• pp.283-293
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• 2005

The purpose of this study was to evaluate the effect of dual bonding technique by comparing microshear bond strength between two different luting methods of resin cement to tooth dentin. Three dentin bonding systems(All-Bond 2, One-Step, Clearfil SE Bond), two temporary cements (Propac, Freegenol) were used in this study. In groups used conventional luting procedure, dentin surfaces were left untreated. In groups used dual bonding technique, three dentin bonding systems were applied to each dentin surface. All specimens were covered with each temporary cement. The temporary cements were removed and each group was treated using one of three different dentin bonding system. A resin cement was applied to the glass cylinder surface and the cylinder was bonded to the dentin surface. Then, micro-shear bond strength test was performed. For the evaluation of the morphology at the resin/dentin interface, SEM examination was also performed. 1. Conventional luting procedure showed higher micro-shear bond strengths than dual boning technique. However, there were no significant differences. 2. Freegenol showed higher micro-shear bond strengths than Propac, but there were no significant differences. 3. In groups used dual bonding technique, SE Bond showed significantly higher micro-shear bond strengths in One-Step and All-Bond 2 (p<0.05), but there was no significant difference between One-Step and All-Bond 2. 4. In SEM observation, with the use of All-Bond 2 and One-Step, very long and numerous resin tags were observed. This study suggests that there were no findings that the dual bonding technique would be better than the conventional luting procedure.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.2A
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• pp.259-267
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• 2008

The ultimate strengths of reinforced concrete deep beams are governed by the capacity of the shear resistance mechanism composed of concrete and shear reinforcing bars, and the structural behaviors of the beams are mainly controlled by the mechanical relationships according to the shear span-to-effective depth ratio, flexural reinforcement ratio, load and support conditions, and material properties. In this study, a simple indeterminate strut-tie model reflecting all characteristics of the ultimate strengths and complicated structural behaviors is presented for the design of simply supported reinforced concrete deep beams. In addition, a load distribution ratio, defined as a magnitude of load transferred by a vertical truss mechanism, is proposed to help structural designers perform the design of simply supported reinforced concrete deep beams by using the strut-tie model approaches of current design codes. In the determination of a load distribution ratio, a concept of balanced shear reinforcement ratio requiring a simultaneous failure of inclined concrete strut and vertical steel tie is introduced to ensure the ductile shear failure of reinforced concrete deep beams, and the prime design variables including the shear span-to-effective depth ratio, flexural reinforcement ratio, and compressive strength of concrete influencing the ultimate strength and behavior are reflected upon based on various and numerous numerical analysis results. In the companion paper, the validity of presented model and load distribution ratio was examined by employing them to the evaluation of the ultimate strengths of various simply supported reinforced concrete deep beams tested to failure.

• Steel and Composite Structures
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• v.29 no.2
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• pp.273-286
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• 2018

In recent years, significant progress has been made in developing design rules for stainless steel members, while the investigation on bolted connections is relatively limited, in particular at elevated temperatures. In this paper, experimental and numerical investigations on stainless steel bolted connections at ambient and elevated temperatures from the literature were reviewed. Firstly, the research program that focused on structural behavior of cold-formed stainless steel (CFSS) bolted connections at elevated temperatures carried out by the authors were summarized. Over 400 CFSS single shear and double shear bolted connection specimens were tested. The tests were conducted in the temperature ranged from 22 to $950^{\circ}C$ using both steady state and transient state test methods. It is shown that the connection strengths decrease as the temperature increases in the similar manner for the steady state test results and the transient state test results. Generally, the deterioration of the connection strengths showed a similar tendency of reduction to those of the material properties for the same type of stainless steel regardless of different connection types and different configurations. It is also found that the austenitic stainless steel EN 1.4571 generally has better resistance than the stainless steel EN 1.4301 and EN 1.4162 for bolted connections at elevated temperatures. Secondly, extensive parametric studies that included 450 specimens were performed using the verified finite element models. Based on both the experimental and numerical results, bearing factors are proposed for bearing resistances of CFSS single shear and double shear bolted connections that subjected to bearing failure in the temperature ranged from 22 to $950^{\circ}C$. The bearing resistances of bolted connections obtained from the tests and numerical analyses were compared with the nominal strengths calculated from the current international stainless steel specifications, and also compared with the predicted strengths calculated using the proposed design equations. It is shown that the proposed design equations are generally more accurate and reliable than the current design rules in predicting the bearing resistances of CFSS (EN 1.4301, EN 1.4571 and EN 1.4162) bolted connections at elevated temperatures. Lastly, the proposed design rules were further assessed by the available 58 results of stainless steel bolted connections subjected to bearing failure in the literature. It is found that the proposed design rules are also applicable to the bearing resistance design of other stainless steel grades, including austenitic stainless steel (EN 1.4306), ferritic stainless steel (EN 1.4016) and duplex stainless steel (EN 1.4462).