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A user-friendly model for the design of single adhesive anchors subjected to tension loading in uncracked concrete is presented. Descriptions of the various types of adhesive anchor systems is included as well as a summary of prev...
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A user-friendly model for the design of single adhesive anchors subjected to tension loading in uncracked concrete is presented. Descriptions of the various types of adhesive anchor systems is included as well as a summary of previously published design models. The development of the user-friendly design model includes a comparison of the model and previously published models to a database including 888 European and American tests. The comparison shows that the simple user-friendly model provides a better fit to the database than more complicated design models previously presented. Although the model is limited to anchors located away from free edges, it provides the basis for development of models which account for the effect of edges, anchor groups, and other design conditions.
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This paper presents the results of a comprehensive test program investigating various factors with the potential to influence the bond strength of polymer - based adhesive anchors. Twenty rod - ucts from 12 manufacturers were incl...
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This paper presents the results of a comprehensive test program investigating various factors with the potential to influence the bond strength of polymer - based adhesive anchors. Twenty rod - ucts from 12 manufacturers were included in the program for a total of 765 tests. To establish a reference bond strength, baseline tests were per - Formed at room temperature for anchors installed in cleaned, dry Holes. Individual factors were isolated through separate test series That maintained baseline conditions, except for the one variable Under consideration.
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The purpose of this research program was to determine the behavior of grouted anchors loaded in tension and to develop rational design procedures for these types of anchors. A grouted anchor was defined as an anchor (headed or unh...
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The purpose of this research program was to determine the behavior of grouted anchors loaded in tension and to develop rational design procedures for these types of anchors. A grouted anchor was defined as an anchor (headed or unheaded) installed into a hole in hardened concrete with a structural grout (cementitious or polymer). Grouted anchors typically have hole diameters at least 50% larger than the anchor diameter. This is different from adhesive anchors that typically use a polymer material with an unheaded anchor installed in a hole diameter less than 50% larger than the anchor diameter. This paper presents the results of 237 tension tests of both headed and unheaded anchors installed using six cementitious and three polymer grouts. Results indicate that the behavior of unheaded grouted anchors is similar to adhesive anchors, whereas the behavior of headed grouted anchors is similar to cast-in-place headed anchors. For some products, a bond failure at the grout/ concrete interface is possible and needs to be considered.
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This research discusses post-installed anchors strengthened by post-installed reinforcement (PRs) under tensile loading. Both types of adhesive and expansion anchors were tested under tensile loading. The PRs are reinforcing bars ...
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This research discusses post-installed anchors strengthened by post-installed reinforcement (PRs) under tensile loading. Both types of adhesive and expansion anchors were tested under tensile loading. The PRs are reinforcing bars that were installed in a vertical and an inclined direction around a single anchor, as different samples separately. In general, the results showed that the PRs in the vertical direction were more effective than those in the inclined direction. It was found that the tensile capacity of the adhesive anchors significantly improved using the PRs. Although, no major enhancement was recorded in the tensile capacity of the expansion anchors. For both types of anchors, the PRs prevented severe concrete breakout failure. Moreover, with the PRs, a higher ductile behavior was observed at both types of anchors. Employing PRs could be a feasible and practical method to strengthen anchorage systems in concrete and prevent severe damages in concrete substrates.
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Post-installed connections are widely used in the rehabilitation, strengthening, and expansion of existing concrete structures. These connections accommodate the connecting of new elements to old concrete using post-installed anch...
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Post-installed connections are widely used in the rehabilitation, strengthening, and expansion of existing concrete structures. These connections accommodate the connecting of new elements to old concrete using post-installed anchoring techniques. Attachment of new segments to concrete beams and columns requires the installation of anchors in slim concrete components. Under this condition, the behavior of connection is severely affected by the small width of concrete elements. Additionally, the behavior of anchors is influenced by the confining effects of stirrups in reinforced concrete elements. In this paper, the tensile behavior of chemical anchor connections in single and group formations of four and six anchors is investigated using the results of 36 individual experiments of adhesive anchors installed in plain and reinforced concrete beams. The key design parameters are embedment depth, section width, and effects of the reinforcement. The results indicate high levels of interaction between all studied parameters. The tensile capacities of the single and groups of anchors are compared against ACI 318 predictions. The main effects of parameters, as well as their interactions, are analyzed and discussed. Based on the test results, several recommendations are provided for the installation of adhesive bonded anchors in narrow concrete components.
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This paper is devoted to the fastening system that consists of a number of anchors of approximately equal effective embedment depth, called "anchor group", embedded into hardened concrete, used to transmit forces transverse to the...
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This paper is devoted to the fastening system that consists of a number of anchors of approximately equal effective embedment depth, called "anchor group", embedded into hardened concrete, used to transmit forces transverse to the anchors from an attachment to the concrete. The anchor group is far from the edges and is subjected to no more than marginal axial forces. Being post-installed, rather than cast-in, the embedded end of each anchor is not hooked, and no nuts, washers, or plates are attached to the embedded shaft. The paper focuses on the transverse forces that can be transmitted across an anchor group from an attachment to the concrete. The paper provides an analytical model for predicting the maximum (ultimate) shear force that an anchor group can bear, thus called "shear strength". The model hence allows the structural designer to predict the shear strength of an anchor group post-installed into concrete. The model is based on five mechanical assumptions, which were established from a wide-ranging numerical analysis. Model predictions turned out to be, on average, 20% lower than the results of experiments performed on cast-in anchor groups borrowed from literature. The comparison verifies model accuracy, considering that the tested anchor groups benefitted from the extra-strength furnished by nuts and washers attached to the embedded shaft. Model predictions were also compared to code provisions; the former resulted to be up to one third of the latter. The paper presents and comments those comparisons, as well as all mathematical development. Applications of the model to wide-ranging case studies is presented and discussed as well.
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A paradigm shift toward the application of artificial intelligence and soft computing methods in developing prediction models has been seen recently for its higher accuracy and its ability to provide generalization. This study aim...
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A paradigm shift toward the application of artificial intelligence and soft computing methods in developing prediction models has been seen recently for its higher accuracy and its ability to provide generalization. This study aims to develop a prediction models for the tensile capacity of the screw and adhesive anchors in thin concrete members with full-thickness embedment depth utilizing artificial neural network (ANN) and gene expression programming (GEP) methods. A total of 175 experimental data were surveyed from previous studies and used in developing the prediction models. Variables implemented in the models are concrete compressive strength, anchor type, anchor diameter, and concrete member thickness. The ANN-based model provided a higher accuracy compared to the GEP model. However, ANN and GEP provided higher accuracy when compared to proposed models based on the concrete capacity design (CCD) method. The ANN model resulted in a reduction of 24% and 19% in COV and RMSE, respectively, compared to the CCD model. A parametric study using ANN indicated that adhesive anchors exhibited three times the capacity of screw anchors on average. The study also showed that, unlike adhesive anchors, screw anchors' capacity is not affected by concrete compressive strength and anchor diameter at 2 in. concrete thickness.
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An experimental study was conducted to investigate the tensile and shear behaviors of post-installed adhesive anchors. The testing program involved 42 specimens of single and groups of 4, 6, and 9 anchors with 150 mm and 200 mm sp...
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An experimental study was conducted to investigate the tensile and shear behaviors of post-installed adhesive anchors. The testing program involved 42 specimens of single and groups of 4, 6, and 9 anchors with 150 mm and 200 mm spacing. The design parameters considered in the investigation were anchor spacing and number of anchors in group. The tensile and shear force-displacement relationships and failure modes of the adhesive anchors together with the effects of design parameters on the responses of the anchors are presented. The test results are compared with those predicted by empirical equations available in the literature including Act 318-14. The comparison study shows that the models proposed by Eligehausen et al. (2006) and Ollgaard et al. (1971) are well predicting the tensile and shear capacities of the adhesive anchors, respectively, despite the ACI design equations which underestimate those capacities. (C) 2015 Elsevier Ltd. All rights reserved.
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In this study, single cast-in-place anchors and retrofit anchors (expansion, undercut, and adhesive) were exposed to five simulated environmental exposure conditions: 1) ultraviolet light; 2) freezing and thawing; 3) corrosion in ...
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In this study, single cast-in-place anchors and retrofit anchors (expansion, undercut, and adhesive) were exposed to five simulated environmental exposure conditions: 1) ultraviolet light; 2) freezing and thawing; 3) corrosion in a pH-neutral salt solution; 4) wetting and drying with simulated acid rain; and 5) combined freezing and thawing, corrosion in a pH-neu-tral salt solution, and wetting and drying. To evaluate the effects of different environmental exposures, the tensile load-deflection behavior of the exposed anchors was compared with that of otherwise identical unexposed anchors. Ultraviolet light exposure did not affect the anchors studied. Freeze-thaw exposure reduced the preload and decreased the initial stiffness of torque-controlled expansion anchors. Salt (corrosion) exposure did not adversely affect the behavior of expansion anchors. Wetting and drying exposure to simulated acid rain did not significantly affect the anchors studied. The combination exposure reduced the stiffness of some torque-controlled expansion anchors. These results show that when expansion anchors are used in concrete subjected to cycles of freezing and thawing, their preload should be checked regularly. The results also imply that in concrete subject to cycles of freezing and thawing while wet, water should be prevented from entering the drilled holes of mechanical anchors.
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