Dissertations / Theses on the topic 'Adhesive anchors'

The thesis presents the main characteristics of the mechanical behaviour of adhesive anchors installed in concrete. They are the mechanisms of failure, the relationship between applied pull-out load and slip of the anchor and the stresses and strains in each of the three components (steel-resin-concrete). The study is primarily experimental but theoretical and finite element analyses are also included. These main characteristics are dependent on the adhesion and wetting phenomena across the resin-concrete and resin-steel interfaces, and on a series of parameters relating to geometry, properties of materials and methods of installation. The principal conclusions obtained are: a) The combined mode of failure involving concrete, resin tensile and interfacial bond failure, is the most probable provided that the resin has a high adhesive strength and that the anchor diameter is larger than the minimum value necessary to prevent steel failure, which can be calculated. b) The sequence of failure in the combined mode is concrete failure in the upper part, bond failure in the remaining part of the anchor, and resin tensile fracture at the bottom of the anchor. c) The values of pull-out load normalized with respect to concrete strength can be regarded as independent of concrete strength. Therefore, a limit state design criterion for adhesive anchors in any concrete substrate can be established. d) The values of anchor displacement normalized with respect to concrete strength vary linearly with it. Based upon this, a simple mathematical function can be determined, which allows the calculation of the displacement of any adhesive anchor. This can be used as a design criterion for the limit state of serviceability of the particular system.

Various anchorage systems including both cast-in-place and post-installed anchors have been developed for fastening both non-structural and structural components to concrete structures. The need for increased flexibility in the design of new structures and strengthening of existing concrete structures has led to increased use of various metallic anchors in practice. Although millions of fasteners are used each year in the construction industry around the world, knowledge of the fastening technology remains poor. In a sustainable society, buildings and structures must, from time to time, be adjusted to meet new demands. Loads on structures must, in general, be increased to comply with new demands, and the structural components and the structural connections must also be upgraded. From the structural connection point of view, the adequacy of the current fastenings for the intended increased load must be determined, and inadequate fastenings must either be replaced or upgraded. The current design models are generally believed to be conservative, although the extent of this behavior is not very clear. To address these issues, the current models must be refined to allow the design of new fastenings and also the assessment of current anchorage systems in practice. The research presented in this thesis consists of numerical and experimental studies of the load-carrying capacity of anchors in concrete structures. Two different types of anchors were studied: (I) cast-in-place headed anchors, and (II) post-installed adhesive anchors. This research focused particularly on the tensile load-carrying capacity of cast-in-place headed anchors and also on the sustained tension loading performance of post-installed adhesive anchors. The overall objective of this research was to provide knowledge for the development of improved methods of designing new fastening systems and assessing the current anchorage systems in practice. For the cast-in-place headed anchors (I), the influence of various parameters including the size of anchor head, thickness of concrete member, amount of orthogonal surface reinforcement, presence of concrete cracks, concrete compressive strength, and addition of steel fibers to concrete were studied. Among these parameters, the influence of the anchor head size, member thickness, surface reinforcement, and cracked concrete was initially evaluated via numerical analysis of headed anchors at various embedment depths. Although these parameters have considerable influence on the anchorage capacity and performance, this influence is not explicitly considered by the current design models. The numerical results showed that the tensile breakout capacity of headed anchors increases with increasing member thickness and/or increasing size of the anchor head or the use of orthogonal surface reinforcement. However, their capacity decreased considerably in cracked concrete. Based on the numerical results, the current theoretical model for the tensile breakout capacity of headed anchors was extended by incorporating several modification factors that take the influence of the investigated parameters into account. In addition, a supplementary experimental study was performed to verify the numerically obtained findings and the proposed refined model. The experimental results corresponded closely to the numerical results, both in terms of failure load and failure pattern, thereby confirming the validity of the proposed model. The validity of the model was further confirmed through experimental results reported in the literature. Additional experiments were performed to determine the influence of the concrete compressive strength and the addition of steel fiber to concrete on the anchorage capacity and performance. These experiments showed that the anchorage capacity and stiffness increase considerably with increasing concrete compressive strength, but the ductility of the anchor decreases. However, the anchorage capacity and ductility increased significantly with the addition of steel fibers to the concrete mixture. The test results also revealed that the tensile breakout capacity of headed anchors in steel fiber-reinforced concrete is significantly underestimated by the current design model. The long-term performance and creep behavior of the post-installed headed anchors (II) was evaluated from the results of long-time tests on adhesive anchors under sustained loads. In this experimental study, adhesive anchors of various sizes were subjected to various sustained load levels for up to 28 years. The anchors were also exposed to several in-service conditions including indoor temperature, variations in the outdoor temperature and humidity, wetness (i.e., water on the surface of concrete), and the presence of salt (setting accelerant) additives in the concrete. Among the tested in-service conditions, variations in the outdoor temperature and humidity had the most adverse effect on the long-term sustained loading performance of the anchors. Based on the test results, recommendations were proposed for maximum sustained load levels under various conditions. The anchors tested under indoor conditions could carry sustained loads of up to 47% of their mean ultimate short-term capacities. However, compared with these anchors, the anchors tested under outdoor conditions exhibited larger creep deformation and failure occurred at sustained loads higher than 23% of their mean ultimate short-term capacities. Salt additives in concrete and wet conditions had negligible influence on the long-term performance of the anchors, although the wet condition resulted in progressive corrosion of the steel. Based on the experimental results, the suitability of the current testing and approval provisions for qualifying adhesive anchors subjected to long-term sustained tensile loads was evaluated. The evaluations revealed that the current approval provisions are not necessarily reliable for qualifying adhesive anchors for long-term sustained loading applications. Recommendations were given for modifying the current provisions to ensure safe long-term performance of adhesive anchors under sustained loads.

La technique des ancrages par scellement chimique consiste à sceller une tige filetée dans un trou foré dans le béton durci grâce à une résine polymère. Les principaux avantages de cette technique sont la facilité d’installation et les propriétés mécaniques élevées de la résine à température ambiante. Grâce à l’adhérence de la résine, ce type d’ancrage peut être dimensionné pour avoir des performances similaires voire supérieures de celles des autres systèmes d’ancrages (mécaniques et coulés en place). En revanche, à hautes températures, e.g. incendie, l’adhérence de la résine se dégrade rapidement menaçant la capacité de l’ancrage à supporter les charges appliquées. Cela crée un risque sur les vies et les biens dans le bâtiment. Plusieurs accidents se sont produits comme l’effondrement du Big Dig Tunnel aux USA (2006) et le tunnel Sasago au Japon (2012) qui ont montré l’importance d’avoir des méthodes d’évaluation fiables de ce type d’ancrages. L’objectif de cette thèse est d’établir une méthode d’évaluation et une méthode de dimensionnement afin d’assurer la tenue structurale des ancrages par scellement chimique en situation d’incendie. L’étude est structurée en quatre parties :i. Protocoles expérimentaux pour les essais au feu des chevilles chimiques. Des essais d’arrachements au feu ont été réalisés sur des chevilles chimiques (résine époxy). Les profils de températures le long de l’ancrage ont été déterminés expérimentalement pour différentes configurations d’essais. Ensuite, ces profils thermiques ont été exploités comme données d’entrée pour calculer la résistance des chevilles par la méthode Pinoteau (intégration des résistances). Cette étude a permis de préciser les conditions expérimentales à utiliser pour l’évaluation des chevilles chimiques au feu.ii. Proposition d’un modèle de dimensionnement basé sur des calculs thermiques en utilisant la méthode des éléments finis en 3D. Les profils de température correspondant aux différentes configurations d’un ancrage dans le bâtiment ont été calculés à l’aide des propriétés thermophysiques des matériaux Eurocode pour le béton et l’acier. La modélisation en 3D a été comparée à la modélisation en 2D plane utilisée communément dans la littérature. Les deux approches ont été comparées aux mesures expérimentales et couplées avec la méthode Pinoteau pour évaluer l’influence de la méthode de modélisation sur le résultat de l’intégration des résistances. Suite à la validation du modèle 3D, des investigations thermiques ont été conduites sur d’autres paramètres pouvant influencer les essais au feu des chevilles chimiques. Cette étude a permis de valider la méthode de calcul en 3D comme la méthode la plus représentative du problème d’une cheville chimique au feu.iii. Validation de la méthode Pinoteau pour le dimensionnement des chevilles chimiques au feu en utilisant le modèle de dimensionnement proposé précédemment. Les calculs de la résistance au feu de trois chevilles chimiques différentes ont été comparés à des essais d’arrachement. Cette étude menée sur une large gamme de tailles de chevilles a permis de valider l’utilisation de l’intégration des résistances pour le dimensionnement.iv. Etude du comportement des chevilles chimiques dans le béton fissuré à hautes températures. Une méthode d’évaluation a été développée afin de déterminer la réduction de la résistance d’adhérence liée à la fissuration du béton, à hautes températures (chauffage électrique). Des essais ont été faits sur des chevilles chimiques (résine époxy) dans le béton fissuré et non-fissuré à température ambiante et à hautes températures. La réduction de la résistance avec l’augmentation de la température a été investiguée. Cette étude a permis d’obtenir une bonne répétabilité des résultats grâce à l’augmentation du nombre d’essais et le bon contrôle du scénario thermique appliqué
The technique of bonded anchors consists of fastening a threaded rod in a drilled hole in hardened concrete by polymer adhesives. The main advantages of this technique are ease of installation and the high mechanical properties of the adhesive at ambient temperature. Due to the adherence of the adhesive resin, this type of anchors can be designed to ensure similar or even higher performances compared to other anchor systems (mechanical and cast-in). However, at high temperatures, e.g. fire situation, the adherence of the adhesive degrades rapidly. Fire decreases the adherence of the adhesive and leads to the inability of the anchor to support the fixed objects. This creates a risk on the lives and goods inside the building. Several accidents occurred like the collapse of the Big Dig Tunnel in the USA (2006) and the Sasago tunnel in Japan (2012) and highlighted the importance of having reliable evalutation methods of this type of anchors. The objective of this thesis is to establish an assessment and a design method to ensure the structural resistance of bonded anchors in fire situations. This project is structured into four main parts:i. Experimental protocols for fire tests on bonded anchors. Pull-out fire tests were conducted on bonded anchors (epoxy adhesive). Temperature profiles along the embedment depth of anchors were determined experimentally for different test configurations. Then, these temperature profiles were used as entry data to calculate the fire resistance of anchors using Pinoteau’s method (Resistance Integration Method). This study allowed to precise the experimental conditions to be adopted for fire evaluation of bonded anchors. ii. Proposition of a design model based on transient thermal calculations using finite element method in 3D. Temperature profiles were calculated using the thermophysical material properties of concrete and steel in the Eurocode. 3D modelling was compared to 2D modelling commonly used in the literature. Both approaches were compared to measurements during fire tests and coupled with Pinoteau’s method to assess their impact on the calculation of fire resistance of anchors. Following the validation of the 3D model, thermal investigations were conducted on other parameters that could influence fire tests of bonded anchors. This study allowed to validate the 3D modelling approach as the most representative of the problem of bonded anchors exposed to fire.iii. Validation of Pinoteau’s method for the design of bonded anchors under fire by using the previously proposed design model. Calculations of fire resistance of three different bonded anchor products were compared to pull-out tests. This study conducted on a wide range of anchor sizes lead to the validation of the Pinoteau’s Method for the design of bonded anchors.iv. Study of the behavior of bonded anchors in cracked concrete at high temperatures. An assessment method was developed to determine the reduction of bond strength due to cracked concrete, at high temperatures (electrical heating). Tests were conducted on bonded anchors (epoxy adhesive) in cracked and uncracked concrete, at ambient and high temperatures. The evolution of the reduction with temperature increase was investigated. This study ensured a good repeatability of test results due to the increased testing potential and the good control of the applied heating scenario

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One of the most important principles in the connections design is the continuous search for simple solutions. Maximum economy in the precast construction is achieved with simple connection elements, with adequate performance and quick installation. One of the alternatives to be considered during the project to improve the simplicity in the column production is to avoid holes and cuts in the formwork. Projections and holes in the forms are laborious and reduce its lifecycle. Then, in order to make the column production process easier, this work aims study the alternative of using chemical adhesive for fastening the corbel reinforcement after casting the column. The work presents a literature review about the main concepts that are important to this solution: Connections design, chemical anchors, corbels and strut and tie models. The research also contains an experimental program with 3 tests full scale specimens with equal dimensions short corbels. Were tested 2 postinstalled corbels with the main tie reinforcement fastened with adhesive anchor and 1 cast in corbel with the main tie reinforcement anchored with hooked 90 º bars. The cast in corbel (specimen A) was designed according to the recommendations of the standards NBR6118:2014 e NBR9062:2006, 1 post-installed corbel (specimen B) was designed with the same anchorage length of the cast in corbel and the other post-installed corbel was designed according to the recommendations of the chemical adhesive producer. This way, was possible evaluate the influence of the anchorage length in the corbel behavior and the safety of the solution comparing with a cast in corbel. The anchorage length did not influence the corbel behavior during the test. The specimen A presented the ultimate load of 400 kN, specimen B 340 kN and specimen C 377 kN. All of the specimens presented failure by flexure-tension in a ductile manner and ultimate loads higher than foreseen by standards and calculation models. The post-installed specimens (B and C) had a similar behavior, presented higher crack width and were less stiffer than the specimen A. Specimens B and C also presented an inclined crack in the anchorage region of the column that alert to a different stress distribution in the anchorage region. Thus the solution of post-installed corbels with adhesive anchors presented a satisfactory performance, further research is needed in order to reduce the crack widths in the corbel region and avoid the cracks in the column.
Um dos princípios mais importantes no projeto de ligações é a busca contínua por soluções simples. A máxima economia em uma construção pré-moldada é atingida quando os elementos de ligação são razoavelmente simples, com um desempenho adequado e com uma montagem rápida. Uma das alternativas a ser considerada durante o projeto, visando melhorar a simplicidade na produção de pilares, é evitar furos e saliências nas fôrmas. Projeções que requerem furações e recortes nas fôrmas são trabalhosas e reduzem sua vida útil. Assim, com o intuito de facilitar o processo produtivo de pilares com consolos, o presente trabalho visa estudar a alternativa de utilizar adesivos químicos para a instalação das barras que compõe a armadura e concretagem do consolo em etapa posterior à execução do pilar. O trabalho apresenta uma revisão bibliográfica acerca dos principais conceitos que são importantes para esta solução: comportamento de ligações, ancoragens químicas, consolos e modelos de bielas e tirantes. A pesquisa também traz um programa experimental no qual foram ensaiados três modelos em escala real com consolo curto de mesmas dimensões, dois consolos com armadura do tirante ancorada com ancoragem química e um consolo monolítico com armadura ancorada com gancho dobrado a 90º. O consolo monolítico (modelo A) foi projetado atendendo os requisitos das normas NBR 6118:2014 e NBR 9062:2006. Um modelo (modelo B) com ancoragem química foi projetado com o mesmo comprimento de ancoragem do modelo monolítico e outro modelo (modelo C) com ancoragem química foi projetado conforme as recomendações do fabricante do adesivo químico. Desta forma, foi possível avaliar, através da comparação entre os modelos, a influência no comportamento do comprimento de ancoragem e a segurança desta solução em comparação com um consolo monolítico. O comprimento de ancoragem não apresentou influência no comportamento dos consolos pós-instalados. O modelo A apresentou carga última de 400 kN, o modelo B de 340 kN e o modelo C de 377 kN. Todos os modelos apresentaram ruptura por tração na flexão de forma dúctil e cargas últimas maiores que o previsto por normas e modelos de cálculo Os modelos com ancoragem química (B e C) tiveram comportamento similar, apresentaram maior abertura de fissuras e menor rigidez em comparação com o modelo monolítico. Os modelos B e C também apresentaram uma fissura inclinada no pilar na região da ancoragem, que atenta para uma distribuição de tensões diferente na região da ancoragem. A alternativa de consolos com ancoragens químicas mostrou comportamento satisfatório, no entanto, a solução ainda necessita de maiores estudos, principalmente no sentido de se reduzir a abertura de fissuras no consolo e combater o aparecimento de fissuras no pilar.

Les systèmes d’ancrages adhésifs sont utilisés dans plusieurs applications en génie civil, notamment en réhabilitation et réparation des ouvrages d’infrastructure tels que des dalles de ponts, chaussées, tunnels, barrages, murs, poteaux, ainsi que dans certains travaux d’exploration géologique et minière. Un système d’ancrage adhésif comprend trois composants : l’élément d’ancrage : une barre d’armature ou une tige filetée ; le matériau adhésif : polymérique, cimentaire ou hybride ; et le substrat : en béton ou en maçonnerie. Les charges imposées sur les barres d’ancrage sont transmises au substrat par adhérence chimique (réactions) et liaison mécanique (interlock) entre les composants mentionnés. Le modèle de design d’adhérence uniforme établit que la performance structurale d’un système d’ancrage adhésif est déterminée par la contrainte de l’adhérence (τ), développée sur toute la surface de contact, entre les composants à l’intérieur du trou d’ancrage. Ce projet, en partenariat avec l’entreprise AMBEX, étudie et évalue la performance des systèmes d’ancrage avec adhésifs en matériau cimentaire, par rapport au comportement sous chargement continu. Pour ce faire, on a ancré des barres d’armature dans un substrat en béton conventionnel. Les deux adhésifs étudiés sont les cartouches d’ancrage AAC et ARC. On a tenu compte des paramètres géométriques et d’installation en assurant la rupture de l’adhérence lors des essais d’arrachement. On a évalué deux conditions en service: température ambiante (21ºC) et élevée (43ºC). On a effectué des essais statiques de traction et des essais sous chargement soutenu. Les résultats sont présentés dans des graphiques « chargedéplacement-temps », afin d’établir des prédictions futures de comportement. Le projet montre les avantages des ancrages adhésifs en matériau cimentaire, tels que le taux de fluage très faible sous chargement soutenu, et quelques limitations aussi, comme la variabilité des résultats à l’arrachement pour les ancrages avec la cartouche AAC.
Abstract : Adhesive anchoring systems are used in many civil engineering applications, including rehabilitation and repair of infrastructure such as bridge decks, roadways, tunnels, dams, walls, columns, and in some geological explorations and mining. An adhesive anchoring system consists of three components: the anchor: a reinforcing bar or a threaded rod; the adhesive material: polymeric, cementitious or hybrid; and a substrate of concrete or masonry. The loads applied on the anchor rods are transmitted by a chemical adhesion to the substrate (reactions) and mechanical interlock between the components mentioned. The design pattern of uniform adhesion establishes that the structural performance of an adhesive anchoring system is determined by the bond strength (τ) developed across the contact surface, between the components within the anchor hole. This project, in partnership with AMBEX, investigates and assesses the performance of an anchoring system, with an adhesive of cementitious material, related to the creep behaviour. To achieve this, steel rebars were anchored in a conventional concrete substrate. Two adhesives were evaluated: AAC and ARC cartridges. Geometrical and installation parameters were taken into account, to ensure bond failure during pullout tests. Two service conditions were studied: room temperature (21ºC) and high temperature (43ºC). Static tensile tests and creep tests were performed. The results are presented in graphs “load-displacement-time”, in order to make predictions of future behavior. The project shows the advantages of adhesive anchors made of cementitious material, as a feeble creep rate at sustained load, and also some limitations, as the variability of tension test results for anchors tested with AAC cartridge.

碩士
國立屏東科技大學
土木工程系所
100
This study investigates the behaviors of chemical adhesive anchors and mechanical anchors under tension and seismic forces. The experimental parameters mainly include the concrete strength 20.6 MPa. The experimental results show in a dry environment, we implanted the M12 chemical adhesive anchors into the concrete, the maximum tension average is 47.63 KN. In the tests on effects of damp environment, the maximum tension average is 41.584 KN, which is 86% of the dry state. Subject the anchors to the sinusoidal-tension loads with 0.1Hz. The experimental results show in the simulated seismic tension tests, the results show the displacement of chemical adhesive anchors has also followed to a linear increase or decrease with the tension changes. The displacement and tension of 1/2” mechanical anchors is non-linear and displacement failure apparent. The study finds the tension in chemical adhesive anchors is stronger than in mechanical anchors. According to the results, we must consider chemical adhesive anchors impairment in the damp environment, and strengthen mechanical anchors anchorage system to increase its shock resistance.

碩士
逢甲大學
土木及水利工程研究所
88
Since steel structures are increasingly used in all kinds of constructions, proper anchorage between the concrete components becomes an important task for the civil engineers. Steel-to-concrete anchors can be classified as cast-in-place anchors and post-installed anchors. The latter, in general.provide better flexibility in construction than the former. However, current design standards do not contain rational design recommendations for most of the post-installed anchors. Therefore, the main objective of this research is to study the behavior of the post-installed adhesive anchors. Firstly, research papers concerning anchors are reviewed in order to determine the representative factors that influence the behavior of adhesive anchors. Three factors including anchor size, embedment length, and concrete compressive strength are found to be the most significant factors. Then the effects of such factors on the failure capacity and failure mode of the anchors are investigated by means of a series of pull-out tests. Finally, the test results are analyzed and compared with the results from other literature. The experimental results indicate that as the increase of anchor size, embedment length, or concrete compressive strength, the anchor capacity raises. Among these three factors, the embedment length influences the failure capacity and failure mode the most. Once the embedment length exceeds a certain depth (which seems to be a factor of anchor diameter), anchor steel fracture occurs and the anchor system reaches its ultimate capacity. Combined cone-bond failure or cone failure takes place when the embedment length is moderate or short. If embedment length is relatively short, bond failure happens.

碩士
逢甲大學
土木及水利工程研究所
89
Since steel structures are increasingly used in all kinds of construction, the study of steel-to-concrete anchorage becomes an important task for both the engineers and researchers. The major objective of this research is to study the behavior of chemically adhesive anchors under static and dynamic loading. Ultimate capacity and failure mode of anchors system are to be predicted by finite element analysis. Material tests and a set of anchor pull-out tests are also performed in order to determine the correct material properties for finite element analysis as well as to provide extra data for evaluating analysis model. By comparing the analysis results with some experimental results verifies that the developed analysis model can predict the anchor behavior to an acceptable degree. Among various influential factors, embedment length of anchor, anchor size, concrete strength, and loading cycle are selected to investigate for the dynamic analysis. It is shown by the analysis results that deeper embedment length or larger anchor diameter both increase the loading cycle of an anchor system. However, higher concrete strength makes very slight improvement on the overall capacity of anchor system.

碩士
逢甲大學
土木工程所
95
Chemically adhesive anchors are widely used in all kinds of construction for their convenience and high performance. Since earthquakes occur frequently in Taiwan, and the post-earthquake capacity of anchors is not well-discussed by engineers and researchers, the major objectives of this research are to determine the post-earthquake capacity of adhesive anchors and to estimate that how many cycles of load an anchor could endure before it fails. Both experimental tests and finite element analysis are performed to obtain the tensile capacity of adhesive anchors and to investigate the influence of seismic loadings on the anchors. It is found from the experimental results that an anchor can resist more than 70 thousands load cycles of cyclic load of 19.4 kN (about 88% of ultimate capacity of that anchor) before failure. And the residual tensile capacity of an anchor already sustained 3 millions cycles of smaller load level (14.5 kN) can still reach its ultimate tensile capacity. The finite element analysis results show that concrete in an anchor system starts to crack at the very early stage of the seismic loading, but the area of crack is confined within a small region and never expand during the rest loading cycles. Besides, the residual tensile capacity of an adhesive anchor is not different than the ultimate tensile capacity if one, two, or three complete cycles of seismic loading are applied to the anchor. This phenomenon indicates that the anchor capacity is not influenced by only few seismic cycles.

碩士
逢甲大學
土木及水利工程所
91
Adhesive anchors are increasingly applied to various structural constructions and reinforcements due to their high strength and good reliability. However, the design specifications for such anchors are not yet well-developed. Moreover, there is very little work done to study the behavior of adhesive anchors with insufficient edge distance. Therefore, the main objective of this study is to investigate the behavior of near-edge adhesive anchors by means of experimental tests. Concrete strength, embedment length and adhesive are three major parameters taken into consideration. It is found from the test results that the capacity of adhesive anchors with insufficient embedment length would increase 3.6kN to 7.2kN when the strength of concrete raises from 20.7MPa to 27.6MPa. Insufficient edge distance definitely causes a reduction in the capacity of anchors. However, this reduction becomes insignificant for the anchors embedded in concrete of higher strength or embedded with sufficient length. The embedment length not only influences the capacity of anchors but also affects the failure mode of anchors. Only the anchors with sufficient embedment length would fail in steel fracture. Besides, the capacity and failure mode both vary when the adhesives used are different. Three design procedures are selected to calculate the predicted capacity of anchors in order to evaluate their applicability to adhesive anchors. The comparison between the calculated values and the test results shows that the design equations proposed by ACI 318 building code yield better prediction.

Post-installed anchoring systems are used extensively in Massachusetts Department of Transportation (MassDOT) projects due their ease of attachment to existing structures. However, recommendations on materials from various manufacturers are currently lacking for certain situations such as long-term tension loading. The purpose of the investigation presented in this thesis was to provide guidance on the use of anchoring systems to MassDOT. This research project evaluated the behavior of adhesive and cementitious bonded anchoring systems per the Stress-versus-Time-to-Failure approach found in the provisional standard AASHTO TP-84 in order to provide recommendations pertaining to the test method. Supplemental short-term anchor pullout tests were conducted using the best performing materials as evaluated by AASHTO TP-84 to study the effects of certain in-service and installation parameters on bond strength. The parameters studied included installation direction and extreme in-service temperatures. Polymer characterization testing of adhesive products were also conducted in order to comment on technique usefulness for field quality assurance/quality control of field installed bonded anchor materials.

碩士
國立成功大學
土木工程學系專班
96
This study investigates the behaviors of chemical adhesive anchors under combined tension and shear forces. The 288 chemical adhesive anchors are tested in this study. The experimental parameters mainly include the concrete strength (140kgf/cm2, 210 kgf/cm2, and 280 kgf/cm2), the burying depth of anchors (12.5cm and 18cm), the distance from the edge of model (10cm and 20cm), and different kinds of force (pure tension、pure shear and combination of both). The experimental results show the distance from edge affects the anti-tension, anti-shear strength of anchors very much. If the distance is too short, the concrete would break and it’s unable to display the anticipated strength. The results also show the distance from edge affects nothing if the distance is longer than 15cm. This result of experiment find the stronger the concrete is, the bigger the strength of chemical adhesive anchors are According to the results, the burying depth of anchors is proportion to the anti-tension strength. However, if the burying depth of anchors is less than 12.5cm, it is unable to achieve the anticipated anti-tension strength, and it has a great effect on the design and anti-tension strength. This study also finds the anchors wouldn’t up to the ultimate anti-tension strength and break unless the concrete strength is big enough and the burying depth of anchors is deep enough. According to the results, the experienced formula of anti-tension and anti-shear of chemical adhesive anchors is also proposed in this study.

This thesis describes an experimental study on the long-term creep behaviour of adhesive anchors under sustained tensile loads in combination with different environmental exposures. A comprehensive background and literature review is presented, focusing on various bond stress models for adhesive anchors, factors affecting their bond behavior, and an overview of available testing standards and evaluation criteria. The experimental program comprises of 82 test specimens. The specimens consist of a cylindrical shaped concrete block of 300 mm (12 inch) in diameter and 200mm (8 inch) in depth, with 15M (No. 5) deformed steel bar post-installed to an embedment depth of six times the bar diameter or 125mm (5 inch). Three types of adhesives were used for anchor installation: Type-A a fast setting two component methyl methacrylate adhesive, Type-B a fast setting two part epoxy adhesive, and Type-C a standard set two part epoxy adhesive. The study is divided into four phases. Phase I consists of 27 static pullout tests to determine the yield strength (fy) and the maximum tensile capacity of each anchor system under three exposure conditions. Phase II and Phase III consist of 36 specimens tested under sustained load levels of 40%fy (32kN) and 60%fy (48kN)under normal laboratory conditions (room temperature) and moisture exposure, respectively. Phase IV consists of 9 specimens tested under sustained load with a load level of 40%fy (32kN) with exposure to freeze/thaw cycling. All sustained load tests lasted for a period of at least 90 days. The results of the static pullout testing showed that specimens with epoxy based adhesive exhibited stronger bond strength, forcing the anchor to fail by rupture prior to bond failure. Under sustained load testing, specimens with standard set epoxy based adhesive showed insignificant creep displacement under room conditions, however, when exposed to moisture noticeable creep displacements were recorded. Specimens with both fast setting epoxy and methyl methacrylate based adhesives showed higher creep displacements under environmental exposure (moisture, freeze/thaw) versus those kept at room temperature. Displacement data from creep testing were analysed and projected over a service life span of 50 years for room temperature exposure, and for 10 years for moisture and freeze/thaw exposures. Based on the analysis results, the service life of different anchor systems was estimated. An integrated qualification and testing protocol is proposed for the creep behavior of adhesive anchors under various environmental exposures.

碩士
逢甲大學
土木工程所
93
ABSTRACT The connection between steel and concrete elements is an important subject for civil engineers. Anchors are widely adopted in the steel-to-concrete connections in a variety of applications such as the construction, maintenance and retrofit of new or damaged structures. In recent years, the adhesive anchors are increasingly used to various structural applications due to their high strength and convenience. However, there is a lack of the design specifications for such anchors. Moreover, there is very little work done to study the behavior of adhesive anchors with insufficient edge distance under either static or dynamic loads. Therefore, the main objective of this research is to investigate the behavior of near-edge adhesive anchors under static and seismic loadings by means of experimental tests. Hopefully, the results would be helpful to the development of design and construction specifications of adhesive anchors. In order to understand the effect of insufficient edge distance and seismic loads on the behavior of adhesive anchors, 24 groups of experimental tests are performed. Concrete strength, edge distance and loading conditions are three major parameters taken into consideration. It is found from the test results that due to different edge distances, different failure types of adhesive anchors may occur. Adhesive anchors reach their ultimate capacity when the edge distance exceeds 1.5 times of the embedment length. Under this situation, the capacity of anchors is controlled by steel strength and steel anchors fail in fracture. While the edge distance becomes smaller, the anchor capacity is controlled by concrete strength and concrete edge breakage, or combined cone-bond failure happens. This research also attempts to evaluate the applicability to adhesive anchors of ACI 318 Building Code by comparing the calculated values based on the design procedures proposed by ACI Code with the experimental results. The comparison shows that the calculated values of ACI Code are in the conservative side. And the calculated values tend to be much lower than the test results if the edge distance is smaller.

碩士
國立中央大學
土木工程學系在職專班
104
Taiwan currently follows the standards stipulated in the ISO/IEC 17025 General Requirements for the Competence of Testing Laboratories for the quality assessment of construction materials. By commissioning TAF accreditation laboratories, the level of quality control and technical competency of laboratories can be ensured. However, accreditation laboratories can only assess the properties of submitted test samples. The advantage is that contracting parties can freely select a suitable TAF accreditation laboratory. The disadvantage is that the reports provided by these accreditation laboratories are only applicable to the specimens submitted by the contracting party, and test results lack representativeness. Moreover, the authenticity of the samples provided by the contracting party is not accounted for, and therefore the quality of construction materials during and after construction cannot be assessed. Only by adopting the accreditation system of ISO/IEC 17020 inspection bodies to establish relevant accreditation items, and commissioning these inspection bodies to conduct inspections before, during, and after construction activities can technical competency and construction quality be effectively improved. Consequently, the inspection results can be used to verify the pre-construction design effectiveness of the owner or the licensed design professional, the mid-construction quality control mechanism of contractors, and the post-construction quality assurance mechanism of related construction units. The purpose of the present study was to discuss the development conditions and trends of the TAF inspection bodies in Taiwan. In addition, the effectiveness of these inspection bodies on post-installed adhesive anchors in concrete was investigated. To supply references for ISO/IEC 17025 testing Laboratories intended to upgrade to ISO/IEC 17020 inspection bodies.

Adhesive anchorage systems have found widespread use in structural applications, including bridge widening, concrete repair and rehabilitation, and barrier retrofitting. Because these applications typically require adhesive anchorage systems to be installed outdoors, the effects of climate conditions and day-to-day temperature fluctuations on adhesive behavior and performance should be considered. The purpose of this thesis is to simulate pullout tests of adhesive anchorage systems for threaded rod and reinforcing bars and to emulate effects under various temperature conditions through the use of finite element analysis. Results from the finite element simulation are then compared to the physical tests conducted at UMass Amherst to determine the validity of the finite element model and to assess any notable differences in adhesive anchor performance in hot, cold, and ambient temperatures. In addition, differences in adhesive stresses when anchoring threaded rod versus reinforcing steel are evaluated.

This thesis describes part of the work associated with Project 0-6719 sponsored by the Texas Department of Transportation (TxDOT). The primary objective of the project is to examine the feasibility of strengthening older continuous multi-span steel girder bridges through the use of post-installed shear connectors. Bridges potentially eligible for retrofit have noncomposite floor systems, where the concrete slab is not attached to the steel girders with shear connectors. Many of these bridges were designed in the 1950's and 1960's for loads smaller than the standard design loads used today. A secondary objective of the project, and the main focus of this thesis, is to examine the design of post-installed shear connectors for fatigue. Of particular interest in this study is the adhesive anchor, given its convenient installation procedure but relatively poor fatigue performance in previous tests. The objectives of this thesis were to quantify the fatigue strength of the adhesive anchor, as well as quantify the shear force and slip demands on adhesive anchors in realistic bridge conditions. In regards to the first objective, twenty-six direct shear fatigue tests were performed on adhesive anchors. Each test was conducted on a single adhesive anchor in order to capture its individual cyclic load-slip behavior. Results indicate that adhesive anchors have considerably higher fatigue strength than conventional welded shear studs, making partial composite design feasible in the strengthening of older steel bridges. In regards to the second objective, analytical and computational studies were conducted on composite beams with adhesive anchors. Results show that the shear force and slip demands are typically smaller than the endurance limits determined from direct-shear testing. This suggests that fatigue failure of adhesive anchors under service loads may not be a primary concern. Based on the results, preliminary recommendations for the design of adhesive anchors for fatigue are provided.
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