Statement of Problem: Evaluation of new adhesives efficacy in bonding orthodontic brackets to enamel has led to different results. The new measuring method, micro-Shear bond Strength, is preferred as an accurate method due to its ability to reduce confounding factors.Purpose: The purpose of this study was to evaluate and compare the micro-Shear bond Strength of three different adhesive systems for enamel surface preparation before bracket bonding.Materials and Method: In this experimental study, 90 extracted premolars were randomly divided into three groups of 30. Transbond XT was bonded to enamel after enamel surface preparation with acid etch in the first (control) group, Transbond plus self-etch primer in second group, and Adper prompt L-pop self-etch adhesive in third group. Then each group was randomly divided into two subgroups of 15. Micro-Shear bond test was performed after 24 hours (T1) and 3-months (T2). Bond failure mode was also evaluated according to Adhesive Remnant Index (ARI). Two way ANOVA and Tukey tests were used for bond Strength evaluation in groups, and mode of bond failure was analyzed with Kruskall Wallis and Mann Whitney tests.Results: The highest bond Strength was found in acid etch group (29.17 MPa). Difference of bond Strength at two intervals was statistically significant in all groups ( p <0.001). Bond Strength difference between T1 and T2 was also significant in three groups ( p <0.001). However changes over time in three groups did not reveal any significant differences ( p = 0.091). Bond failure analysis demonstrated significant differences in ARI between groups.Conclusion: Bond Strength of acid etch group was the highest and self etch primer showed higher bond Strength than self etch adhesive group. Less adhesive remnant was found in self etch group.

Background & Aim: More than 30 years has passed since introduction of glass-ionomer cement as a dental restorative material, luting cement and liner. Although they are sensitive to moisture and desiccation during the initial setting stages, relative poor physical properties because of chemical bonding to tooth substrate, and long-term esthetic quality, they are recommended for restoring anterior and posterior primary teeth, cervical lesions and root caries of permanent teeth. In this study, Shear bond Strength of Fuji II was compared with of ariadent glass-ionomer cements. Materials & Methods: Thirty intact extracted primary molars were prepared for this study. Selected teeth were divided in two groups of 5. Sample were free of caries, fracture, crack, discoloration or any structural abnormality. The dentin of buccal surface of teeth were exposed by microtome apparatus. The surface was conditioned by polyacrylic acid (10%) for 20 seconds. Glass ionomer cements (Fuji II, and Ariadent) were prepared in a plastic cylinders (15 of each) and attached to the dentin of teeth horizontally. Shear bond stength of materials was measured by instron (Model 1159).Results: Mean Shear bond Strength of Ariadent cement was 4.2±1.9 Mpa while 7.4±1.5 Mpa was of Fuji II cement (P=0.000).Failure mode was similar between two cements (P=ns). The most prevalent type of failure mode was cohesive failure leaving a firmly attached thin and homogenous layer of cement to dentin, in both groups.Conclusion: It appears that Shear bond strenght of Ariadent cement to primary tooth is much lower than of Fuji II.

Shear failure of structural elements such as beams and columns is considered as a brittle failure. Accordingly, the design standards provide conservative equations for determining Shear Strength to ensure to delay of this abrupt failure. In this regard, the AISC 360 Standard provides equations to determine the Shear Strength of encased composite members considering the steel contribution, the reinforced concrete contribution, and the Strength of the steel section in combination with the transverse reinforcement. The AISC 360 conservatively ignores the combination of the Shear Strength of steel section and reinforced concrete to determine the Shear Strength of encased composite members due to insufficient research. This study investigates the Shear behavior of encased composite (EC) columns experimentally and numerically. Short EC columns in which their behavior is governed by Shear are tested considering several design variables, including the concrete compressive Strength, the steel ratio, the shape of the steel core, the ratio of longitudinal reinforcement, the transverse reinforcement spacing, and the level of the composite action. Failure mode, the crack pattern, the load-displacement response, the nominal Shear Strength of EC columns, the yield condition of steel core, and the effects of key variables on the Shear Strength of EC columns are presented and discussed. The results of this study show that the exclusion of steel section or reinforced concrete contribution leads to a significant underestimation of the Shear Strength of encased composite members. Out of the considered design variables, the transverse reinforcement ratio, concrete compressive Strength, and steel core ratio are the most influential variables affecting the Shear behavior of EC columns.

Investigating non-linear behavior of structures in order to evaluating vulnerability and determining performance level of existing structures is very important. Because of deep beams dimensions and also cost and time limitation and complexity of applying boundary conditions in lab, it is better to use software and non-linear analysis. In this paper the behavior of deep beams with lightweight and normal concrete and Shear length to height ratio of 0.5, 1, 1.5 and 2 and also height of 30, 45, 60 and 90 centimeters is studied using Abaqus software. Results of non-linear analysis show that normalized Shear Strength decreases with increase in height in both groups of beams and this decrease can be seen in all Shear length to height ratios. Comparing experimental results with truss methods available in codes shows that all methods are conservative in small height beams and safety margin reduces with increase in height. Results are non-conservative in CSA method in Shear length to height ratio of 0.5 and in normal concrete, and with increase in Shear length to height, predicted Shear Strength by CSA method is much more than Strength obtained from analysis.

Consolidated-drained triaxial compression tests were conducted to compare the stress-strain and volume change response of sands and clayey sands reinforced with discrete randomly distributed polypropylene fibers. The influence of various test parameters such as fiber content (0. 0%, 0. 5% and 1. 0% by weight), clay content (0%, 10% and 20% by weight), relative density (50% and 90%) and confining pressure (100 kPa, 200 kPa and 300 kPa) were investigated. It has been observed that addition of clay particles to the sands decreased the Shear Strength of samples. Also, increase in clay content reduced dilation and increased compressibility of the mixed soil. Addition of the fiber to both sands and clayey sands samples improved the Shear Strength and increased ductility and axial strain at failure point.

Nowadays, the use of steel plate Shear walls, as an effective seismic resisting system, has been of great interest in enhancing the lateral Strength and stiffness of buildings both in renovation and seismic rehabilitation of existing concrete and steel structures. In the present research, the Shear Strength and stiffness of steel plate Shear walls in various configurations of stiffeners, including horizontal, vertical, and horizontal– vertical, were investigated by finite element method and finally semi-empirical relations were presented in this regard. The results indicated that the Shear Strength and stiffness of stiffened SPSWs were well predicted by the proposed relations, but increasing the number of stiffeners above a certain range will not have a significant effect on enhancing the stiffness and Strength.

In this study, non-linear behavior of diagonally stiffened steel plate Shear walls as a seismic resisting system has been investigated, and theoretical formulas for estimating Shear Strength capacity of the system have been proposed. Several validated analytical finite element models of steel Shear walls with various stiffener dimensions are generated to verify and compare the analytical and theoretical outcomes. Non-linear transient analysis under monotonic loading are carried out and the pushover curves of the models are obtained. It is observed that the diagonal stiffeners have been able to reduce the buckling effects of the infill steel plate, and they have increased the elastic Shear buckling Strength and the ultimate Shear capacity of the system in comparison with the un-stiffened thin steel plate Shear walls, and there are good agreements between the propounded theoretical method and the analytical results.

Aim: The aim of this study was to compare the etching effect of porcelain with Hydrofluoric acid (HF) one Shear bond Strength using one coat bond and self cure composite.Methods & Materials: The study was conducted experimentally using observation as its technique. 40 porcelain cubes were prepared and assigned into 4 groups. Group I specimens were treated with 35% phosphoric acid.Subsequently one coat bond was applied to bond the bracket, group II specimens were made fresh with fine diamond bur, treated with a 35% phosphoric acid and one coat bond was applied to bond the bracket, group III specimens were treated with a 20% hydroflouric acid (HF) and Nomix composite bond was applied to bond the bracket, group IV specimens were treated with a 40% HF acid and the same procedure in the group III was followed. The Instron machine was used at a crosshead speed of 0.5 mm/min to test the Shear bond Strength.Result: The Shear Strength was 2.47±1.8Mpa for group I, 5.64±2.6Mpa for group II, 3.28±1.8Mpa for group III and 3.03±2.6 for group IV. The overall difference between the four groups was statistically significant (P<0.05). Conclusion: The use of fine diamond bur and 35% phosphoric acid for Etching and use of one coat bond can achieve a successful bond between either use only phosphoric acid or 20% HF acid-Etched with No mix composite and 40% HF acid etched with No mix composite.

The use of high-Strength concrete in reinforced concrete slabs is becoming popular in Australia and other countries. Current design provisions of AS3600 and other major codes throughout the world are based on empirical relationships developed from tests on low-Strength concrete. In this paper, the experimental results from four research studies are used to review the existing recommendations in design codes for punching Shear failure of slabs. Design codes referred in this study are AS3600 and CEB-FIP MC 90. In AS3600 the punching Shear Strength is expressed as proportional to fc1/2. However in CEB-FIP MC 90 punching Shear Strength is fc1/3 .It is shown that the present provisions assumed to be proportional to in AS3600 are applicable up to 100 MPa.