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This paper proposes a simple and practical method for retrofitting deficient (non-seismic detailed) exterior beam-column joints based on fixing steel plates and angles around the joint with different configurations. Six half-scale exterior RC beam-column joints were tested under quasi-static cyclic loading with a constant axial load on the column. The experimental program included two control specimens representing code-detailed and deficient joints in addition to four retrofitted specimens. The proposed retrofit methods were designed to compensate the lack of joint transverse reinforcement using different steel arrangements (X-shape, horizontal plates) and the short development length of beam bars using angles tied by external or internal anchors. One of the retrofit methods is applicable in the presence of a transverse beam. The test results showed that the deficient joint exhibited brittle joint shear failure, unlike the code-detailed joint which failed by flexure in the beam. The proposed retrofitting methods effectively prevented the brittle joint shear failure and increased the joint strength, ductility, stiffness, and energy dissipation. A softened strut and tie model was applied and modified to predict the joint shear strength of control and retrofitted joints and it showed a good agreement when compared with the experimental results.

Reinforced concrete deep beams are structural members having depth much greater than normal in relation to their span, while the thickness in the perpendicular direction is much smaller than either span or depth. The strength of deep beams is usually controlled by shear, rather than flexure. In this study, the previous researches related to reinforced concrete deep beams will be reviewed. These researches approximately started in the second half of the past century. Large numbers of researchers studied the behavior of concrete deep beams and the determination of their capacity. Some of these researches are experimental investigations carried out by testing a number of deep beams with variation in some parameters, while the others are theoretical to estimate deep beam capacity by developing some theories and suggestion of equations for calculating its capacity and comparisons were made with those adopted by some codes. Because of the large number of these researches, their review requires large part of this study, and because the prior studies elaborately reviewed the pioneer researches, only the researches made since year 2000 will be reviewed in this study.

Stainless steel reinforcing rebars and prestressing strands are viable alternatives to carbon steel materials for prestressed concrete structures in extremely aggressive environments. They offer better durability and require less maintenance. This study experimentally investigated the transfer length and prestress losses of 15.2-mm- (0.6-in.-) diameter Duplex High-Strength Stainless Steel (HSSS) strands as well as the shear and flexural behavior of two full-scale 12.8-m- (42-ft-) long AASHTO Type II concrete girders prestressed with HSSS strands and reinforced with duplex stainless steel rebars. The girders were made composite by adding a deck slab. One girder was tested in shear at both ends while the other girder was tested in flexure. Experimental shear and flexural behavior of the girders exhibited a constant increase in load carrying capacity up to failure. The failure mode for the shear tests was web shear, and for the flexural test was rupture of the HSSS strands. Both girders tested in shear and flexure failed in a progressive manner as they exhibited adequate warning through noticeable deflection, excessive cracking, and large reserve strength from first cracking to failure. The applicability of AASHTO LRFD provision for stainless steel reinforcing materials was investigated. AASHTO LRFD equations for flexural resistance were modified to cover rupture of strand failure mode. Experimental shear strength and flexural strength of the girders were greater than the predicted values by AASHTO shear equations and modified AASHTO flexural equations, respectively.

This article conducts a theoretical and experimental analysis of three dimensional (3D) finite element (FE) model to anticipate the shear strength, load–deflection, and crack pattern of fourteen Hybrid Glass Fiber Reinforced Polymers (GFRP)/Steel Bars in Reinforced Concrete Beams without stirrups by ANSYS. The reinforced concrete beams are simply supported. All beams cross-sections were of 120 mm breadth and variable depth; the overall length was 2300 mm with a clear span of 2000 mm without stirrups. In this paper, the adopted variables are; concrete compressive strength ( f c ' ), shear span to depth ratio (a/d), depth of beam (d), and the reinforcement ratio (ρ). In hybrid GFRP/steel reinforced concrete beams, the experiments demonstrate a significant improvement in ductility and an apparent decrease in deflection and deformation of the beams. In contrast, during cracking initiation and propagation, better performance is found in hybrid GFRP/steel reinforced concrete beams. A comparison is conducted between the results of the ANSYS and the experiment to ensure that the finite element model is accurate. Additionally, each parameter's effect was described and compared to experimental results. The FE models’ theoretical conclusions are in acceptable agreement with the experimental outcomes.

Joints that represent locations of discontinuity were the prominent factors affecting the overall behavior of precast segmental bridges. In this study, the steel shear key was designed, which was used to transmit the shear stress of the joints. To study the mechanical characteristics of the steel shear keyed joints in the construction and finished states, direct shear experiments and numerical analysis were carried out. The experimental results showed that the steel shear keyed joints had a high bearing capacity and good ductility. Under the action of confining stress, the joints relied on the mechanical occlusion between the steel keys to transmit the shear forces. When the load-displacement curve entered the horizontal stage, it can still bore large relative deformation, and the bearing capacity did not decrease. In the construction state, the inelastic deformation of the steel shear key should be used to control the design value of the temporary load. In the finished state, the bearing capacity of joints should be controlled by the direct shear strength of the steel shear key, which can be calculated according to the shear formula. The shear strength of the material and size of the steel shear key are the main factors affecting the bearing capacity of steel shear keyed joints.

This paper presents a semi-empirical model to estimate the ultimate shear strength of steel fiber-reinforced concrete (SFRC) beams without shear reinforcement using the gene expression programming (GEP) technique. An extensive, reliable dataset consisting of the data of 266 SFRC beams with no stirrups was established for the development of this model. The most effective variables including the compressive strength ( f c ' ), ratio of shear span-to-effective depth ( a / d ), ratio of flexural reinforcement ( ρ ), and fiber factor ( F ) were employed as input parameters in the GEP-based modeling. The accuracy of the proposed model was verified by its ability to predict a portion of data that had not been used in the training phase. Moreover, the performance of the model was evaluated using different statistical criteria. Sensitivity analysis and parametric studies were conducted on the proposed model to determine its ability to correctly consider the effect of input parameters for predicting the ultimate shear strength. In addition, the proposed model was compared with some other models proposed in the literature, and it was found that the proposed model demonstrates the best performance and accuracy among the considered shear strength prediction models.

In the UHPC-steel composite bridge deck, the thickness of UHPC layer is usually only 40–50 mm, so short headed studs are used for shear connection of the interface between UHPC and steel deck. In this paper, the refined finite element (FE) model of push-out specimen is established to explore failure mode of the stud connection, damage concentration location of UHPC and load-slip behavior of UHPC-steel interface. Verified against the existing test results, FE parameter analysis is conducted, and shear strength formula and load-slip relationship of short headed stud embedded in UHPC are proposed. With the consideration of reduction effect of group studs, the shear strength formula of single stud can be used to simplify the calculation safely. A nominal shear stress S-N curve with 95% survival probability is proposed, fitted by the International Institute of Welding (IIW) recommended method. Based on the fracture mechanics method, a fatigue life evaluation formula of stud under influence of multiple factors is established. By the comparative analysis between the proposed formulas and the existing codified formulas for stud connection in ordinary concrete, the recommended formula for the fatigue strength of stud in UHPC is proposed.

This paper describes a simple analytical tool for the calculation of the shear strength of r.c. rectangular members with shear reinforcement and subjected to only truss mechanism. The proposed method considers simplified stress fields and evaluates the shear strength of members subjected to axial force, bending moment and shear force by means of the application of the static theorem of limit analysis. Unlike most of the formulations proposed in codes and in other research studies, the proposed method considers a single physical model to explain the resistance to axial force, bending moment and shear force, and simultaneously satisfies the equilibrium under all the above internal forces. The paper identifies basic points of the N-M-V ultimate domain and reports relations and procedures to calculate the values of the internal forces of these points as well as the internal forces of the points in between. The method is applied to a set of beam and column members and a comparison is drawn between the shear strength resulting from the simplified method and that from a more complex non-linear mathematical program proposed in the past by the same author. Finally, to prove the value of the method and define the field of reliable application, the proposed method is applied to members tested in laboratory by other researchers and characterised by different geometric and mechanical properties. The obtained results are also compared with those deriving from other methods present in the literature.

Summary Objective This study aimed to evaluate the failure incidence of brackets with at least six months follow-up between self-etch primer and conventional etch/primer, as well as to investigate the clinical duration of the bonding process and the amount of adhesive remnant index (ARI). Methods Electronic search was conducted in databases including PubMed, Scopus, Web of Science, ProQuest, ClinicalTrials.gov, and ICTRP (International Clinical Trials Registry Platform). The electronic search targeted only randomized clinical trials and was limited from January 2000 to June 2021. Delphi list is used to evaluate the risk of bias and Stata Version14.2 software was used. This systematic review was conducted according to the guidelines of the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) and recorded on the Ethics Committee of Research Institute of Dental Sciences, SBMU (IR.SBMU.DRC.REC.1398.240). Results Out of 2288 extracted studies, 30 of them entered the full-text evaluation process. According to the inclusion criteria, 15 studies entered this systematic review. Containing 607 participants and 10,563 brackets/teeth. All the included studies were of randomized clinical trials (RCT) design with either parallel or split-mouth design. Comparing the two groups, the risk difference effect (RD) = 0.007 CI 95% (−0.004,0.018) indicated a neglectable difference in the risk of bracket failure during treatment between the two groups. The index I2 = 53.9% indicated moderate heterogeneity in the results. Furthermore, the P-value = 0.007 indicated statistical insignificance between the two interventions in terms of failure rate. The clinical duration of bonding time analysis were equal to SMD _Cohen = −2.67 CI95% (−3.49, −1.85), which indicated a statistically significant reduction in clinical process time, using the self-etch primer. Data synthesis for adhesive remnant index could not be conducted due to heterogeneity among included studies. Conclusions There was no difference between the self-etch primer and conventional etch/primer in bracket debonding at a medium level of evidence, However, there was statistically significant reduction in clinical bonding time using self-etch primer.

Cold-formed steel (CFS) purlins and studs with staggered web perforations have been used in construction to improve the thermal efficiency of buildings. The perforations adversely affect structural properties of the members, especially their shear strength. Accurate shear strength predictions of such members is a challenging task, which is not easily solved by the traditional methods. This paper explores five machine learning (ML) boosting algorithms, including gradient boosting regressor (GBR), extreme gradient boosting (XGBoost), light gradient boosting machine (LightGBM), gradient boosting with categorical features support (CatBoost), and adaptive boosting (AdaBoost), as tools for predicting the elastic shear buckling loads and the ultimate shear strength of CFS channels with staggered web perforations. The models were developed using open-source software and a large dataset of finite element simulation results with 3512 samples for each property. The models’ optimal hyperparameters were established through an extensive tuning process to ensure their best performance measured using the robust ten-fold cross-validation method. The elastic buckling loads and the ultimate shear strengths predicted by the developed models compared excellently with the simulation results, with CatBoost being the most accurate model in predicting both properties. The models’ accuracy exceeded the accuracy of the existing descriptive equations. The CatBoost models were inspected by evaluating the relative feature importance and partial dependence of the model-predicted targets from features, which aligned well with the mechanics-based knowledge and confirmed the ability of the models to capture the underlying physics. The predictions of the developed boosting machines were compared with those of previously developed ML models, which allowed for ranking the models and selecting the most accurate ones. Resistance and safety factors for the shear strength predicted by the ML models were determined using the AISI S100-16 w/S2-20 provisions. A Python-based interactive notebook was created for rapid and accurate predictions of the elastic shear buckling loads and the ultimate shear strengths of the slotted channels using the developed models.

The use of mechanical metamaterials in engineering applications is often limited because of uncertainty regarding their deformation behavior. This uncertainty necessitates large safety factors and assumptions about their behavior to be included in mechanical designs including metamaterials, which detracts from their greatest benefit, viz. their ultralight weight. In this study, a yield envelope was created for both a bending-dominated and a stretching-dominated cellular material topology to improve the understanding of the response of cellular materials under various load types and orientations. Experimental studies revealed that the shear strength of a cellular material is significantly lower than that predicted by Mohr’s criterion, necessitating a modification of the Mohr’s yield criterion for cellular materials. All topologies experienced tension–compression anisotropy and topology orientation anisotropy during loading, with the stretching-dominated topology experiencing the largest anisotropies.

The paper presents a novel kind of carbon foam composites reinforced by chopped glass fibers. Microstructure, mechanical properties and thermal insulation of the composites have been investigated by scanning electron microscopy, universal testing machine and laser thermal constant analyzer, respectively. Results showed that carbon foam composites had a spherical and closed-cell structure; chopped glass fibers were uniformly distributed in the carbon matrix along different directions. The mechanical properties exhibited optimum with the 7% glass fiber additives, 11.27 MPa of shear strength, higher than that of pure carbon foams by as much as 111%. Compressive and shear fracture were both characterized by gradient brittleness. Many tiny open-pores existed in carbon foams with a certain amount of glass fiber additives, giving rise to the higher thermal conductivity. Nevertheless, carbon foam composites possessed good thermal insulation, 0.311 W·m−1·K−1 at room temperature, and 1.04 W·m−1·K−1 in 800 °C at the most.

In the recent decades, blasts and gas explosions at the off-site of oil and gas plants have increased leading to destruction of important concrete structures, essential equipment and loss of human life. In response, structural engineers have come up with different ways of reinforcing beams of concrete structures using fiber reinforced polymers composite materials to produce blast resistant structures to minimize the impact of the blast loads, due to their unique and individual characteristics like high flexural and shear strength. This paper seeks to research the dynamic behavior, response and performance of reinforce concrete beams strengthened with Carbon Fiber Reinforced Polymer composites when subjected to blast loading. The study aims at proposing a design model of strengthening reinforce concrete beams with Carbon Fiber Reinforced Polymer in supporting concrete structures at off-site oil and gas plants against hydrocarbon explosions. Carbon Fiber Reinforced Polymer composites exhibit higher modulus of elasticity, higher energy absorption capacity, resistant to all forms of alkali and higher tensile strength compared to all other fiber reinforced polymers reinforcements and therefore the need to assess its capacity in protecting concrete structures at oil and gas plants against dynamic loads. The research will be carried out through numerical analysis using the finite element analysis computer program, ANSYS.

Various modes of compacting the asphalt concrete mixture can create mechanically different behaviour of the prepared specimens and can alter its sustainability. An attempt has been made in the present assessment to prepare asphalt concrete specimens by implementation of three modes of compaction, the gyratory, the roller, and the Marshall hammer. The specimens were prepared at the target bulk density of Marshall method at optimum asphalt content. Extra specimens were prepared at 0.5 % asphalt below and above the optimum. Core specimens have been obtained from the roller compacted slab samples. The specimens were tested for the Marshall stiffness, tensile, and shear strength. It was observed that at optimum asphalt content, the indirect tensile strength declines by (18.8 and 70.5) % for gyratory and roller compacted specimens respectively as compared with hammer compacted specimens. At optimum asphalt content, the shear strength declines by (70.5 and 82.2) % while Marshall stiffness declines by (10.2 and 44.8) % for hammer and roller compacted specimens as compared with that of gyratory compacted specimen. Specimens prepared by gyratory compaction are less susceptible to the change in the testing temperature as compared with other modes of compaction. It is recommended to consider the mode of compaction to suit the required design property of sustainable asphalt concrete mixture.

This paper investigates the performance of four different strengthening techniques used to improve the shear capacity of RC beams. Three of the four strengthening techniques used were near-surface mounted (NSM) using carbon fiber-reinforced polymer (CFRP) strips, welded wire mesh (WWM) and textile reinforced epoxy mortar (TREM). The fourth strengthening technique consisted of a u-shape jacket made of ultra-high performance fiber-reinforced concrete (UHPFRC). Seven RC beams made of self-compacted concrete (SCC) were tested using a four-point bending setup. One beam was designed with sufficient shear reinforcement and served as the control in this study while the remaining six beams were cast with sufficient shear reinforcement in one half and no shear reinforcement in the other half. One beam was tested as a shear deficient control without any strengthening. The remaining five beams were strengthened with NSM-CFRP strips at 90°, NSM-CFRP strips at 45°, NSM-TREM strips, NSM-WWM strips and UHPFRC jacketing. The test results of all proposed strengthening techniques showed an increase in the shear strength of the RC beams by 47%–56% compared to using steel web reinforcement. The increase in the shear capacity of RC beams using 15 mm UHPFRC jacket was comparable to the other strengthening techniques. The UHPFRC jacket is considered a promising technique that could be utilized in the repair and rehabilitation of shear deficient RC beams. In addition to increasing shear capacity, the strengthened RC beams' mode of failure altered from brittle shear failure to ductile flexural failure with increased stiffness. Analytical modeling was conducted to predict the shear capacity of tested beams, with results that closely matched experimental observations.

The Laser-Powder Bed Fusion (L-PBF) based AlSi7Mg parts are adopted for the aerospace industries, especially for making antenna, RF components, gyroscopes, and waveguides. The primary use of additive manufacturing in the aerospace industry is because it enables producing very lightweight components with complex designs. However, the mechanical properties of manufactured L-PBF components are not yet fully validated because numerous challenges posed by the process itself and defects that occur on the manufactured materials by L-PBF. In this research, to further elucidate the printing mechanism of AlSi7Mg lightweight alloy a detailed investigation was carried out to analyze the influence of print orientation on the physical, morphological, and mechanical behavior of L-PBF based AlSi7Mg parts. AlSi7Mg parts were manufactured with various print orientations from vertical, inclined and horizontal. The fabricated parts were analyzed for microstructural behavior using an optical microscope (OM), and scanning electron microscope (SEM) with energy dispersive X-ray analysis (EDAX) proving the elemental composition of the AlSi7Mg parts were studied. Mechanical testing such as tensile, hardness, wear, fracture toughness, and shear tests was carried out for various orientations manufactured in order to evaluate their properties. The vertically-oriented AlSi7Mg parts shows 13.8 %, 58.4 % and 7.9 % higher tensile, toughness and shear strength when compared with the horizontally-oriented parts. But the maximum wear resistance was observed in the horizontal parts and it was 52.9 % higher wear resistance than the vertical parts. The results can be used as a guide in the aerospace industry in order to design components with high structural integrity.

Effects of fluid dynamics on cells are often studied by growing the cells on the base of cylindrical wells or dishes that are swirled on the horizontal platform of an orbital shaker. The swirling culture medium applies a shear stress to the cells that varies in magnitude and directionality from the center to the edge of the vessel. Computational fluid dynamics methods are used to simulate the flow and hence calculate shear stresses at the base of the well. The shear characteristics at each radial location are then compared with cell behavior at the same position. Previous simulations have generally ignored effects of surface tension and wetting, and results have only occasionally been experimentally validated. We investigated whether such idealized simulations are sufficiently accurate, examining a commonly-used swirling well configuration. The breaking wave predicted by earlier simulations was not seen, and the edge-to-center difference in shear magnitude (but not directionality) almost disappeared, when surface tension and wetting were included. Optical measurements of fluid height and velocity agreed well only with the computational model that incorporated surface tension and wetting. These results demonstrate the importance of including accurate fluid properties in computational models of the swirling well method.

There is a limited design guidance for practitioners regarding the shear design equations of circular-concrete members with fiber reinforced polymer (FRP) reinforcements, especially the case of incorporating FRP bars and spirals. The objective of this study is to enhance the methods used for estimating the shear capacity of reinforced concrete (RC) beams with FRP bars and spirals. A database of 44 circular concrete beams reinforced with FRP bars tested under shear were compiled from different experimental studies. Two proposed models based on approaches developed for rectangular sections, to predict the shear capacity of beams without and with stirrups, were compared with the selected available shear design equations. The shear strength estimated using the proposed models are slightly more accurate. The comparison indicates that the shear capacity of FRP-reinforced concrete members with circular cross sections may be determined with the V cf and Vsf approaches developed for rectangular sections provided that certain modifications are made to take into account the effective shear depth, equivalent breadth, the mechanical properties and geometry of GFRP spirals.

The impact of reinforced concrete beam-column joints on the shear strength of a building under cyclic loading depends on the types of joints applied. This study considers models of the uniaxial and biaxial joint shear strength of exterior beam-column joints. Prediction models of the uniaxial shear strength under uniaxial cyclic loading based on ACI 352, ASCE 41, and gene expression programming (GEP) have been developed. The ACI 352, ASCE 41, and GEP formulas have the potential to achieve improved results. This study considers a means by which to improve the results of previous models through a proposed deep neural network (DNN) model with three hidden layers among the artificial neural network structures. The R-squared value and mean absolute error determined through this DNN model are 97.94% and 34.13% for the uniaxial model and 98.28% and 2.70% for the biaxial model, respectively. These results indicate that the DNN model is more suitable than the ACI 352, ASCE 41, and GEP models for joint shear strength predictions.

In this study, experiments were carried out to evaluate the seismic performance of a hybrid prestressed precast concrete (HPPC) system devised to ensure the integrity of precast concrete (PC) beam-column joints by introducing the post-tensioning method. A total of four full-scale HPPC beam-column joints were fabricated, and the presence of a topping slab, a post-tensioned length, and a type of tendon were set as the main variables. The quasi-static cyclic loading tests were performed to analyze the load-story drift ratio response, failure mode, ductility, residual deformation, and energy dissipation capacity of each specimen. The seismic performance of the specimen was then quantitatively evaluated based on the acceptance criteria of the ACI 374 report. The shear strength estimation model for the HPPC beam-column joints was also proposed and the proposed model was verified in detail using the test results.

Existing physics-based methods for estimating the lateral strength of reinforced concrete (RC) columns lack generalization capabilities, where the methods for predicting the shear strength of shear- and flexure-shear-critical columns cannot be used to predict the flexural strength of flexure-critical columns, and vice versa. This paper proposes a nature-inspired, metaheuristic, least squares-support vector machine for regression (LS-SVMR) model for enhancing the generalization of lateral strength prediction of RC columns. The metaheuristic LS-SVMR model is a hybrid computational intelligence approach, which integrates LS-SVMR to elucidate the nonlinear mapping between influential factors and the lateral strength with a nature-inspired metaheuristic optimization algorithm, called coupled simulated annealing (CSA), to efficiently tune the hyper-parameters and facilitate the training process. The generalization performance is validated by comparison with several machine learning (ML) models using cross-validation strategies and with commonly used physics-based approaches as well as by successfully modeling the physical processes associated with variation of lateral strength of flexure-, shear-, and flexure-shear-critical columns when input predictors vary.

Cross-laminated timber (CLT) is produced from renewable bio-composite material and has been gaining popularity in building industry largely due to easily customised panellised construction technique, which is fast, efficient, minimises construction risk and waste. CLT is often considered as a sustainable alternative to traditional construction materials, and can be used to complement steel and concrete to build a sustainable future. CLT is reported to provide excellent resistance against both out-of-plane and in-plane loading but rolling shear properties have been recognized as one of the critical parameters that often controls the design resistance when CLTs are subjected to out-of-plane loading scenario. Rolling shear characteristics are highly dependent on wood species, sawing patterns and width-to-thickness ratio (wl/tl) of a single lamella. This paper presents a thorough investigation on rolling shear properties of two types three-layer CLT panels (CL3/105 and CL3/135) produced by XLam from Australian Radiata Pine. Rolling shear properties were measured using two test methods i.e. short-span four-point bending test and planar shear test. Typical rolling shear failures were observed in samples tested using short-span bending method and rolling shear stresses were evaluated by using various analytical methods. Planar shear samples also failed in rolling shear, as expected, and showed comparable results. Existing theoretical approaches were used to evaluate the rolling shear properties with a characteristic rolling shear strength of 2.0 MPa and shear modulus of 65.5 MPa for the considered Radiata Pine CLT panels. In addition, an empirical equation has been proposed based on the rolling shear results for other similar species published in literature and the current observations were compared against the proposed equation.

A numerical analysis model should consider the indirect connection’s shear strength to evaluate buildings’ seismically strengthened effect by embedded and perimeter steel moment frames with the indirect connection. The seismic design code for the Korean school facilities does not support the particular indirect connection’s design information, recommends to secure through the experiment. This paper investigates the shear strength of bolted indirect connections of the steel retrofit method per the experimental results. The bolted indirect connection for the embedded steel retrofit method dissipated most indirect connection energy, excluding the connection steel plate and post-installed anchors as flexural behavior. Regardless of the lack of concrete shear strength due to the post-installed anchors, it was not observed the cracks in the column. In contrast, the bolted indirect connection of the perimeter steel retrofit method was confirmed as the only vertical cracks due to the post-installed anchors in the column and the indirect connection. This indirect connection is that the post-installed anchors resisted the shear force as shear behavior. According to these experimental results, the shear-resistant capacity of bolted indirect connections of the embedded and perimeter steel retrofit methods was proposed.

This paper presents experimental and numerical investigations related to the block shear mechanism of double-lap welded connections. The experiment investigation includes 36 specimens composed of 3.0 mm and 6.0 mm thick mild carbon steel SS275 plates with varying block lengths and widths. It is found that the tension fracture in block shear of welded connection tends to be curved along the critical plane. The numerical results shows that the stress triaxiality effect in increasing the tensile stress over the critical tension plane, and thus the tension resistance component increases. This paper also examines the accuracy of various block shear strength equations given in the design codes as well as the literature. Topkaya’s equation is found to be significantly more accurate than other block shear strength equations for the tested specimens. Nonetheless, it is recommended to use the reduced tensile coefficient to ensure both safe margin and the accuracy.

The physical and mechanical properties of soft coal body constitute one of the most important factors inducing coal wall spalling. In order to explore the mechanical essence of coal instability disaster and stability enhancement of water injection, the 7# coal in Huainan mining area is taken as the research object. Firstly, the distribution characteristics of coal particle size, point-load strength, original water content, microstructure characteristics, and shear strength of coal under different water contents are measured by laboratory tests. Then, based on the test results, the cementation morphology and force evolution law of granular coal water in coal body are analyzed using liquid bridge theory. The results show the following: (1) With the increase of particle size, the mass ratio of granular coal increases gradually. The percentage of particle coal with particle size less than 2.5 mm accounts for 47.157%, fractal dimension is 2.172, and uniaxial compressive strength and tensile strength are 3.822 MPa and 0.165 MPa, respectively. (2) The coal body is dry (the original moisture content is 1.336%), containing a large number of loose particles, pores, fissures, and other microfabrics. This “low water content and multiporosity” feature is the essential reason for its low strength, fragmentation, and instability and disaster. (3) In the process of water content increasing from 0.966% to 26.580%, the shear stress-displacement curve of coal body gradually changes from softening type to hardening type, and the failure type transitions from brittleness to ductility. The cohesive force increases first and then decreases, while the angle of internal friction almost has no change. (4) After reasonable water injection, the shape of liquid bridge in coal body changes into capillary tube, and the liquid bridge force reaches the maximum value, which transforms from a highly unstable bulk to a stable continuum. The research results have important theoretical significance and practical value for the safe and efficient mining of soft coal seams.

Cross-laminated timber is a wood product with excellent fire resistance and mechanical performance that is often used in tiny houses. Using the ASTM standard E564, the shear performance of cross-laminated timber wall panels, with and without openings, were investigated in this study. The specimens were made of spruce-pine-fir IIc lumber and installed on a test platform using high-strength bolts passing through them. This connection mode limited the displacements obtained in the test, primarily the shear displacements and rocking displacements. By comparing the static load test data of the three specimens with openings and the one without an opening, it was found that openings reduced the shear strength and shear stiffness. For the same sized rectangular opening, the shear stiffness of the cross-laminated timber panel was less when the wider side was horizontal (normal to the direction of the applied force). The shear stiffness of the cross-laminated timber wall panels can be effectively improved by reinforcing the areas near the openings with metal sheets. With reinforcement, the shear strength did not change drastically, but the damage to the cross-laminated timber wall panels was significantly reduced.

Dense continuous oxide layers of semi-solid Al6061 complicate joints; therefore, ultrasound is introduced to break the continuous oxide layer. In this study, stacked semi-solid Al6061 samples were compressed with the application of ultrasound at the semi-solid metal formation temperature. The distribution of oxide layer and the shear strength near the bonding surface were used to analyze the connection effect of the interface. Results indicate that the continuous oxide layer can be broken by ultrasound and bonding strength can be improved. Compared with the sample simply processed with thermo-compression, the ultrasound-affected sample (100-ms working cycle, 10-ms operation period in each cycle, and 2.4-kW operation power) shows a 310% increase from 10.1 to 41.4 MPa in shear strength of the interface between semi-solid samples and a 29.7% reduction from 0.976 to 0.685 in oxide continuity degree. The results of this study can be applied in the additive manufacturing of semi-solid Al6061.

Concrete beams reinforced with rectangular spiral shear reinforcement instead of the ordinarily closed stirrups have been recently extended. However, this extension has never been addressed for light-weight concrete structural elements. An experimental program is conducted in this research to investigate the shear performance of light-weight concrete beams that are transversely reinforced with continuous rectangular spirals. Four groups, including 20 specimens, were constructed where the groups contain two different shear span to depth ratios of 2.0 and 1.5 and have two different spiral spacing of 200 mm and 150 mm. Five different inclination angles of the spiral reinforcement were considered for each group: 85°, 80°, 77.2°, 75o, and 72.5°. The beams were tested under static four-point loading. Test results have shown that using rectangular spiral reinforcement has enhanced the shear capacity and deflection of the test specimens. Shear strength enhancement has ranged from 3% up to 47% compared to the ordinarily closed stirrups. Test results have also shown that the angle of inclination, which would result in the best performance, is influenced by the shear span to depth ratio. The optimum angles were found 85° and 75°, for the shear span to depth ratio of 2.0 and 1.5, respectively.

Summary Objective The aim of this in vitro study was to evaluate the effects of enamel deproteinization on the shear bond strength of a self-etching primer Transbond Plus™(TBP), with different application times of sodium hypochlorite (NaOCl 5.25%), primarily and secondarily on the adhesive remnant index score. Materials and methods One hundred twenty-five freshly extracted human premolars were randomly and blindly divided into five groups according to the enamel surface preparation, as follows (n = 25): group 1(control): Etching with 37% phosphoric acid for 15 seconds + Bonding; group 2 (control): TBP™ without NaOCl, group 3: 60 seconds NaOCl + TBP™, group 4: 30 seconds NaOCl + TBP™, group 5: 15 seconds NaOCl + TBP™. The same composite resin was used (Transbond XT™) to bond the orthodontic metal brackets. After the immersion of the teeth in distilled water at 37 °C for 24 hours the shear bond strength was measured using the universal testing machine and the adhesive remnant index score (ARI) was evaluated under an optical microscope (25 × ). Results The mean SBS values (in MPa) of the groups were respectively: group 1: 13.03 ± 5.36; group 2: 12.28 ± 3.06; group 3: 12.38 ± 4.55; group 4: 12.98 ± 5.76; and group 5: 11.73 ± 5.67. Enamel deproteinization increased the SBS for groups 3 and 4, but no statistically significant difference was found between the five groups (P = 0.883). Group 1 showed the highest ARI scores, with 52% of the teeth retaining all the adhesive (score 3). However, for all the other groups, scores 0 and 1 were predominant, with less than half of the adhesive or no adhesive at all remaining on the teeth. Conclusions Enamel deproteinization with sodium hypochlorite (5.25%) and the variation of its application time has no effect on the SBS of the self-etching primer Transbond Plus ™.

Although, international codes such as (CSA-S806-12) and (ACI-440-15) proposed shear design provisions for concrete beams reinforced with (FRP), many researchers are still investigating this case. Most of the available research investigated either beam without stirrups or beam with stirrups. The purpose of this study is to propose a unified formula for the prediction of the shear strength of FRP reinforced beams with and without stirrups. A collected experimental database of 553 shear tests on FRP reinforced concrete beams was used to develop a new formula to predict the shear strength using genetic programming technique. The accuracy of the proposed formula was compared with that measured during testing and calculated using the models available from literature. The new proposed formula showed more accurate predictions than the models from the literature, besides that, it is much simpler than them.

Staggered rectangular perforations (slots) are provided in the webs of cold-formed steel (CFS) beams and columns to reduce their thermal conductivity and improve the energy efficiency of CFS buildings. The perforations adversely affect the structural characteristics of the members, especially those governed by the web parameters, such as the shear strength and shear buckling. This paper presents machine learning (ML) models to predict the elastic shear buckling load and the ultimate shear strength of CFS channels with slotted webs. Support vector machine (SVM), decision tree (DT), random forest (RF), and k-nearest neighbor (KNN) regressors were trained using a large dataset of numerical results with 3512 samples. An extensive search was conducted to find optimal hyperparameters of the models that result in the best predictions and prevent overfitting. The models’ performances were evaluated employing the ten-fold cross-validation method to make more data available for training and reduce bias and variance. The SVR, DT, and RF models demonstrate good prediction accuracy, which exceeds the accuracy of the existing descriptive equations. Relative feature importance was evaluated using the permutation and SHAP methods for each model. Partial dependence of the buckling load and the shear strength from the channel features was assessed. The predictions of the developed ML models were also compared with the predictions of previously developed artificial neural networks (ANNs). The comparisons demonstrated that ANNs showed higher accuracy in predicting the elastic buckling load, whereas the SVR model provided the most accurate shear strength predictions.

In modular steel buildings, factory prefabricated volumetric modules are assembled onsite to form permanent buildings. The inter-module connections provide a path for load transfer between modules. In this study, the detailed working mechanisms of different load-transfer components in endplate-type inter-module connections are investigated systematically. The effectiveness of commonly used simplified models for inter-module connections is evaluated, and a simplified analytical model with multiple springs is proposed on the basis of cooperative working interactions. The results indicate that the tensile strength of inter-module connections is dramatically lower than the compressive strength, and the moment transfer abilities are closely correlated with the tensile strengths. The horizontal shear resistance is provided initially through contact friction between connected columns, and the shear strength calculations need to consider the contribution of axial loads in module columns. Vertical dislocations between horizontally arranged modules are resisted through inclusion of a continuous gusset plate. The vertical shear resistance of interior inter-module connections can then be calculated based on the shearing action of the intermediate gusset plate within the gap region between horizontally connected columns. The out-of-plane prying deformation at endplates and different stiffnesses and strengths at different load-transfer components lead to nonuniform rotations between connected columns in the connections. The proposed model can effectively simulate the detailed load-transfer abilities of inter-module connections and can be easily applied to the structural analysis of modular steel buildings.

In the present study, an experimental study was performed to investigate the direct shear behavior of precast panel connections using steel fiber-reinforced cementitious mortar shear keys. The main experimental parameters included the volume fraction of steel fibers adopted for the connections and the details and configurations of the cast-in-place shear keys. The volume fractions of steel fibers were in the range of 0.75–1.5%. In total, four series with 22 push-off test specimens were fabricated and tested with various shear key configurations. The experimental results obtained were analyzed and discussed in detail to examine the effects of various parameters on the shear behavior of the panel connections. On the basis of the experimental results and theoretical shear transfer mechanism, an analytical model to predict the shear strength of the panel connections with shear keys was proposed, and its predictions showed a good correlation with the experimental results.

This paper presents an experimental investigation on a novel prefabricated concrete wall system with horizontally placed hollow core panels. Compared with traditional clay bricks, prefabricated concrete hollow core panels have the advantages of convenient quality control, reduced self-weight, fast installation, low labour cost, and high load-bearing capacity. In this study, nine full-scale wall specimens (i.e., two under compression, five under compressive and lateral loads, and two under compressive and cyclic lateral loads), which were extracted from an apartment project, were prepared and tested. As evidenced by the experiments, the load-bearing capacities of the walls could satisfy the design requirement. In general, the failure occurred in the panel-to-panel connections, panel-to-frame connections, and corners of openings. The openings (i.e. windows and doors) substantially reduced the compressive and shear capacities and resulted in a more ductile failure. The pinching effect was apparent for wall specimens under cyclic loads, and the energy dissipation capability of the wall was reduced when a door opening was set. The design standard for masonry walls was adopted to estimate the axial compressive and shear strength owing to the unavailability of a design standard specifically for the new type of hollow-core walls. The predicted strength was generally significantly lower than the experimental strength, revealing a large safety margin for engineering applications.

In this study the effectiveness of near surface mounted (NSM) rope and strip in shear strength of reinforced concrete beams was experimentally investigated. Fifteen reinforced concrete (RC) beams (150 mm × 250 mm × 1200 mm) (width × thickness × length) designed to fail in shear were constructed and tested. The following parameters were considered in each configuration: CFRP orientation angle, the spacing between CFRP and the strengthening scheme to study the load displacement behavior of RC beams strengthened by NSM Rope and Strip FRP. The results showed that NSM CFRP rope is an effective technique in strengthening of reinforced concrete beams. Using inclined CFRP ropes or strips have the largest load carrying capacity compared to all other configurations where the ultimate load capacity increased by (150–170%) of the control specimen depending on the spacing between CFRP. The inclined NSM CFRP ropes or strips have changed the type of failure in the strengthened specimens from brittle shear to a flexural shear failure.

Literature includes several empirical models to predict shear capacity of steel fiber-reinforced concrete (SFRC) beams. However, some of these models were calibrated based on small database of experiments or include data for beams failed in flexure. This study utilizes a database of 241 tests of SFRC beams failed in shear along with gene expression programming (GEP) to establish more accurate and reliable predictions. Independent variables included in the GEP were fiber factor, longitudinal reinforcement ratio, concrete cylinder compressive strength, and shear span-to-depth ratio. The model provides an average ratio (vtest/vpredicted) of 1.00, a coefficient of variation of 24%, and a root mean square error of 1.33 MPa. The proposed model provides a higher accuracy when compared to existing models in the literature. The study also presents a reliability analysis study to evaluate the safety level embedded in the proposed model. By comparing the safety level of the proposed model to the safety level in reinforced concrete beams without shear reinforcement according to ACI 318-19 equation, a strength reduction factor of 0.5 instead of 0.75 is proposed to achieve consistent safety level with conventional reinforced concrete. Additionally, a varying strength reduction factor with respect to shear span-to-depth is also proposed.

Reinforced concrete slabs are an important component of high-rise buildings as they are designed to withstand the loads they are subjected to. Concrete slabs, on the other hand, may fail due to punching shear, which is one of the most serious risks in the slab column connection. This kind of failure, which is difficult to predict, occurs almost instantaneously and can have disastrous consequences. This research aims to examine how high-strength flat slabs act under vertical loads, as well as how openings affect flat slab punching shear strength. To do so, ABAQUS uses a series of non-linear numerical models to simulate the punching shear effect on reinforced concrete flat slabs and to investigate the effects of the various sizes and locations of the openings and the constitutive modeling of concrete on the punching shear stress of the connections. To begin with, the experimental results of Marzouk and Chen were used to perform the initial calibration of the finite element model. The effect of the openings presents in a flat slab with different positions and sizes and distances of 0d, 1d, 2d, 3d, 4d, and 5d far from the column in parallel position was determined by the analysis of 42 internal connections under incremental vertical load, while the connection without opening was used as a reference in each case. The shear strength was reduced by up to 9.6 percent as a result of an opening located at 2d distance from the column. This result is unaffected by the number of openings. The experimental and numerical results are also used to evaluate the accuracy of the various code equations available for predicting flat slab punching shear capacity. Eurocode prediction is more accurate than Canadian standard.

Shear connectors in composite beam are used to ensure proper connection between concrete slab and steel beam. Headed stud shear connectors are the types most commonly used in composite constructions. Despite its popularity, this type of connectors has presented some drawbacks, notably its installation technique which demands many requirements. Recently, several shear connectors have been developed as an alternative to studs. The aim of the present paper is to present a study of a new type of OMEGA-shaped connector that is easy to design, fabricate and install. The geometry of the connector proposed allows good concrete confinement and provides high flexural stiffness. Experimental push-out tests have been carried out on OMEGA connectors and on headed studs to study their strength, ductility and failure mode. A comprehensive comparison between the two types of connector was established, which showed that the OMEGA connector proposed provides greater strength against shearing and uplifting. Thus, it can be used as an alternative to the conventional connector (headed studs) used in composite steel-concrete beams. The finite element models (FEM) of the push out test were developed using Abaqus software to conduct a parametric study on various dimensions of the OMEGA connector and different concrete strengths to evaluate their influences on the shear capacity and failure mechanism of the steel-concrete connection. It was concluded that the shear strength and failure mode of the OMEGA connector was relatively affected by increasing the shear area and concrete compressive strength, without significant impact on connection ductility. Based on the results obtained from the parametric study, a general equation for predicting the shear strength of the OMEGA connectors was introduced.

Purpose The aim of this study was to evaluate in vitro, the shear bond strength (SBS) and adhesive remnant index (ARI) of pit and fissure sealants (PFS) after enamel conditioning with different new-generation self-etching (SE) agents; additionally, enamel etching patterns were assessed. Methods Healthy unerupted third molars surgically removed for therapeutic reasons (n = 25p/g), were randomly assigned to six groups. Conventional etching (CE) or SE was applied prior to pit and fissure sealants bonding. Enamel conditioned surfaces were evaluated by SEM at × 500, × 1000, and × 2000 magnification to determine etching patterns. Subsequently, 25 PFS blocks (3 × 2 × 1.5 mm) p/g were bonded to enamel surface. Samples were stored in water at 37 °C for 24 h, previous to SBS and ARI test. One-way ANOVA and Tamhane statistic tests were used for SBS; while Mann–Whitney U and Kruskal–Wallis were employed for ARI (p ≤ 0.05). Results For SBS test, CE_PFS_3M and SE1_PFS_Shofu groups showed the lowest values (8.74 ± 4.02 and 8.75 ± 3.90, respectively). The highest scores were observed in SE_PFS_Kuraray group (13.46 ± 5.83). Significant differences in SBS and ARI assessments were found. All experimental groups showed type 1 etching pattern. Conclusion The etching pattern was less pronounced in self-etching groups, which showed an equal or superior in vitro performance compared to conventional etching agents. The clinical use of self-etching agents could be recommended before pit and fissure sealants application in new dental protocols. The best in vitro performance was observed when both applied materials, self-etching agent and pit and fissure sealant have 10-methacryloyloxydecyl dihydrogen phosphate in their chemical composition.

In this study, the experimental finding of two half-scale interior prefabricated Reinforced Concrete column to Steel beam (RCS) sub-assemblage with proposed joint formations with and without web panel in the junction is presented. Previous researches about RCS have been performed to study shear strength of steel web panel in the joint by modeling joint component, however rarely have been conducted to evaluate joint shear resistance experimentally. Over the past 30 years, noticeable analytical and experimental assessments have been performed on the cast in place RCS joints, but seldom have been done on the prefabricated RCS. The steel beams in the proposed joint are attached to the expanded steel plates that were mounted on the joint edge. The thickness of beam flanges was increased to amplify the concentrated horizontal force transfer to the panel zone. The samples were subjected to a cyclic lateral load with displacement control. The cracking pattern, hysteresis curves, joint deformation, stiffness changes, and energy absorption were determined. The existence of the steel web panel in the panel zone significantly increases the shear strength of the panel zone and considerably reduces joint deformation. Shear strength enhancement due to existence of steel web panel determined by comparing connections with and without steel web panel in the joint.

BACKGROUND: The thin-walled regions (TIWRs) of intracranial aneurysms have a high risk of rupture during surgical manipulation. They have been reported to be predicted by wall shear stress and pressure (PS) based on computational fluid dynamics analysis, although this remains controversial. In this study, we investigated whether the oscillatory shear index (OSI) can predict TIWRs. METHODS: Twenty-five unruptured aneurysms were retrospectively analyzed; the position and orientation of the computational fluid dynamics color maps were adjusted to match the intraoperative micrographs. The red area on the aneurysm wall was defined as TIWR, and if most of the regions on the color map corresponding to TIWR were OSI low (lower quartile range), time-averaged wall shear stress (TAWSS) high, or PS high (upper quartile range), each region was defined as a matched region and divided by the total number of TIWRs to calculate the match rate. In addition, the mean values of OSI, TAWSS, and PS corresponding to TIWRs were quantitatively compared with those in adjacent thick-walled regions. RESULTS: Among 27 TIWRs of 25 aneurysms, 23, 10, and 14 regions had low OSI, high TAWSS, and high PS regions (match rate: 85.2%, 37.0%, and 51.9%), respectively. Receiver operating characteristic curve analysis demonstrated that OSI was the most effective hemodynamic parameter (area under the curve, 0.881), followed by TAWSS (0.798). Multivariate analysis showed that OSI was a significant independent predictor of TIWRs (odds ratio, 18.30 [95% CI, 3.2800e102.00], P < 0.001). CONCLUSIONS: OSI may be a unique predictor for TIWRs. Low OSI strongly corresponds with TIWRs of intracranial aneurysms.

This research project aims to propose an innovative analytical method to evaluate steel plate shear wall with partial length connection to vertical boundary element which lacks the connection at the middle height of VBE. In this type of steel shear walls, reducing the length of the connection between infill and vertical boundary element results in a reduction in the flexure and stiffness demand on the vertical boundary elements. Push-over loading was carried out on four small-scale designed test specimens so as to investigate the quality of tension field formation in web plate by changing not connected length ratio. Then numerical model was employed to develop comprehensive study on web plate stress state due to the formation of tension field by changing not connected length ratio. Firstly, the formation of parallel tension strips in the infill plate of the steel shear wall with different partial length connections to vertical boundary elements in specified range of lack of connection was confirmed. Based on aforementioned experimental and numerical study evidence, governing equations have been developed for this analytical solution, including panel shear strength, tension field inclination angle and minimum stiffness requirements in vertical boundary elements.

This paper presents the results of an experimental investigation on the fire response of steel beams and their bolted flange plate (BFP) connections. Using sub-frame assembly, full-scale steel beams with various BFP beam-to-column joints were examined under the ISO 834 standard fire condition. The failure modes, as well as the structural and thermal responses of the beam and the BFP connections were studied. The findings of the experimental studies indicate that the beam flexural failure occurs at the temperature range of 670–700°C when the mid-span deflection exceeds the limitation value specified in the BS-476. The BFP connections fail when the temperature exceeds 760°C, while the beam experiences deflections larger than span/20. The results also show that the bolt hole bearing and the bolt shear control the failure of the BFP connection in fire conditions. The BFP connection detail has a considerable effect on the fire response of the beam, e.g., increasing bolt shear strength in the BFP connection can improve the fire resistance and rating of the beam and its connections in steel moment-resisting frames.

Aims: Wall shear stress (WSS) has been considered a major determinant of aortic atherosclerosis. Recently, non-obstructive general angioscopy (NOGA) was developed to visualize various atherosclerotic pathologies, including in vivo ruptured plaque (RP) in the aorta. However, the relationship between aortic RP and WSS distribution within the aortic wall is unclear. This study aimed to investigate the relationship between aortic NOGA-derived RP and the stereographic distribution of WSS by computational fluid dynamics (CFD) modeling using three-dimensional computed tomography (3D-CT) angiography. Methods: We investigated 45 consecutive patients who underwent 3D-CT before coronary angiography and NOGA during coronary angiography. WSS in the aortic arch was measured by CFD analysis based on the finite element method using uniform inlet and outlet flow conditions. Aortic RP was detected by NOGA. Results: Patients with a distinct RP showed a significantly higher maximum WSS value in the aortic arch than those without aortic RP (56.2±30.6 Pa vs 36.2±19.8 Pa, p =0.017), no significant difference was noted in the mean WSS between those with and without aortic RP. In a multivariate logistic regression analysis, the presence of a maximum WSS value more than a specific value was a significant predictor of aortic RP (odds ratio 7.21, 95% confidence interval 1.78-37.1, p =0.005). Conclusions: Aortic RP detected by NOGA was strongly associated with a higher maximum WSS in the aortic arch derived by CFD using 3D-CT. The maximum WSS value may have an important role in the underlying mechanism of not only aortic atherosclerosis, but also aortic RP.

Objectives: To investigate the effect of Co-curing versus Staged-curing and No-bonding on retention of different resin-based sealants (RBS). Study design: For shear bond strength (SBS) and microleakage tests, 90 extracted premolars were divided equally into 3 groups (I, II, III). Each group was further subdivided equally into 3 subgroups (a, b, c). No-bonding subgroups did not receive a bonding agent, Staged-curing subgroups received a bonding agent that was cured before sealant application, while Co-curing subgroups received a bonding agent that was cured after sealant application. Seal-it was applied for group I, Helioseal-F for group II and Clinpro for group III. SBS buttons were tested using Instron machine, while microleakage specimens were examined using micro-CT. Results: Clinpro showed the highest SBS values in Staged-curing and No-bonding groups (8.72±2.39, 12.51±3.16) respectively. Staged-curing was significantly greater in SBS values than those for other groups (P

We prepare several silicalite composite materials in which foamed ceramics and glass ceramics were connected together without any interlayer. Purple soil and shale residue were used as raw materials to prepare the foamed ceramics that constituted the thermal insulation layer in the silicalite composite materials. The glass ceramics were prepared from waste glass added with 0, 5, 10, 15, 20 and 25 wt% SiO2, which formed the decorative layer in the composite materials. The bonding mechanism of the thermal insulation layer and the decorative layer, and the influence of SiO2 content on the properties of glass ceramics and composite materials were investigated via XRF, XRD, SEM, EDS, etc. The results indicated that the best properties of glass ceramics and composite materials could be achieved at the addition of 20 wt% SiO2. The bulk density, bending strength and coefficient of thermal expansion of the glass ceramics were 2.775 ± 0.015 g cm-3, 58.5 ± 1.2 MPa and (5.65 ± 0.2) × 10-6 m m-1 K-1, respectively. The shear strength and tensile strength of the composite material reached 0.877 ± 0.025 MPa and 0.798 ± 0.02 MPa, respectively.

To evaluate the proportion of microleakage (PM), shear bond strength (SBS), and the fissure sealant (FS) interface by scanning electron microscopy (SEM) in three kinds of FS when the enamel surfaces were contaminated with saliva.198 sound third molar teeth were randomly divided into three pretreatment condition groups (n = 66): dry, saliva contamination removed by cotton pellet, or saliva removed by air-drying. A resin-based FS (Clinpro™), amorphous calcium phosphate-containing FS (Aegis®), or glass ionomer-based FS (Fuji Triage®) was applied on the treated enamel, and PM and SBS were assessed. Two specimens from each group were observed with SEM. p values 0.05 was considered statistically significant.Glass ionomer-based FS showed the highest PM in all three surface conditions (p values 0.05 were considered statistically significant). No significant difference in PM was observed between resin-based FS and amorphous calcium phosphate-containing FS (p 0.05). Resin-based FS showed significantly greater SBS in all three surface conditions compared to glass ionomer-based FS. SEM observations showed that saliva contamination led to gaps at the enamel-sealant interface.Neither cotton pellet-drying nor air-drying effectively removed saliva from the contaminated enamel surface. Glass ionomer-based FS showed the highest PM and the lowest SBS in contaminated and noncontaminated conditions. The highest SBS was obtained with resin-based FS.

A number of models have been proposed to estimate the shear strength of steel fiber reinforced concrete (SFRC) beams. Nevertheless, the previous models have not been widely accepted in terms of consistency and applicability. This study presents a mechanical model to estimate the shear strength of SFRC slender beams without shear reinforcements. The basic assumptions of the proposed model are agreeable with that of the Critical Shear Crack Theory (CSCT), which has been effectively verified by extensive experimental measurements. The calculation of shear strength considers the contributions of various shear-resisting mechanisms, including the shear resistance provided by the compression zone, residual tensile strength and dowel action in main reinforcements, while neglecting the shear resisted by the aggregate interlock. To obtain the shear resistance provided by residual tensile stress along the critical shear crack and determine the neutral axis depth, a compact constitutive law is presented for the residual tensile stress of SFRC with determined crack width. The impact of steel fibers on each shear-transfer action is studied and considered in the formula of each shear-resisting mechanism. The proposed mechanical model can estimate the shear strength of SFRC slender beams without shear reinforcements, the deformation capacity and the location of the critical shear crack. For design purposes, a simplified model is also presented considering the relation between various shear-resisting mechanisms and critical shear crack. The accuracy of mechanical model and simplified model is extensively verified by comparing predicted values of proposed models and previous eight models with experimental data of the two databases.

Cold-formed stainless-steel (CFSS) sections are increasingly popular for architectural and structural applications, especially in the corrosive environment due to its resistance to corrosion and other various benefits. The combination of stainless-steel material properties and the lightweight section properties makes the CFSS section the right choice for offshore steel structures. The demand for the stainless-steel sections in the construction industry is limited to a certain extent due to the higher cost; thus, the optimal use of stainless steel is vital. Openings to the web of CFSS Lipped Channel Beams (LCB) are introduced to facilitate the building services to reduce the floor height. Subsequently, the shear capacity is reduced due to the reduction of the web area. However, only very limited researches have been conducted so far to predict the reduced shear capacity of CFSS LCBs with circular web opening. Hence, this paper addresses a numerical study to investigate the shear behaviour and strength of cold-formed austenitic grade 1.4301 and duplex grade 1.4462 stainless steel LCB sections with unreinforced circular web openings. A detailed parametric study was carried out by developing 180 Finite Element Analyses (FEA) models to establish a wide-ranging shear strength database following the validation process with available shear test results. The analysis of the numerical results showed that the currently available reduction factor equations are either conservative or unsafe to use for the CFSS LCBs with circular openings. Hence, three sets of equations with different approaches to predict the shear capacity of CFSS LCBs with circular web opening are developed and presented in this paper.