Journal articles on the topic 'External anchorage system'
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1
Zhu, Wanxu, Wei Wei, Fengrong Liu, and Rong Zeng. "Method of Designing a Friction-Based Wedge Anchorage System for High-Strength CFRP Plates." Materials 14, no. 21 (October 27, 2021): 6443. http://dx.doi.org/10.3390/ma14216443.
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The cables of high-strength carbon fiber reinforced polymer (CFRP) plates are starting to be applied to large spatial structures. However, their main anchorage systems rely on the adhesive force, which entails risks to their integrity resulting from aging of the binding agent. In this study, a friction-based wedge anchorage system was designed for CFRP plates. The working mechanism of the proposed anchorage system was explored both theoretically and experimentally. The anti-slip mechanism and condition of CFRP plates were formulated so that the equivalent frictional angle of the contact surface between a CFRP plate and wedges must not be smaller than the sum of the dip angle of the wedge external conical surface and the frictional angle between the wedges and barrel. An analysis of the stress distribution in the anchorage zone of the CFRP plate was conducted using the Tsai-Wu failure criterion, which concluded that the compressive stresses should be reduced on the section closer to the load-bearing end of the anchorage system. Furthermore, the anchorage efficiency coefficient was proposed, which depends on stress concentration coefficients, plate thickness, length of anchorage zone, dip angle of wedge external conical surface, and its frictional angle. Then, it was determined that the minimum length of an anchorage zone for the CFRP plates with various specifications should be at least 49 times larger than the CFRP thickness. A finite element analysis and static tensile tests on six specimens were carried out. The experimental results revealed that the anchorage efficiency coefficient of the optimized anchor reached 97.9%.
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Kita, Hiroki, Shoko Kochi, Yoshimichi Imai, Atsushi Yamada, and Tai Yamaguchi. "Rigid External Distraction Using Skeletal Anchorage to Cleft Maxilla United with Alveolar Bone Grafting." Cleft Palate-Craniofacial Journal 42, no. 3 (May 2005): 318–26. http://dx.doi.org/10.1597/03-152.1.
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Objective Documentation of the application of maxillary distraction osteogenesis using rigid external distraction (RED) with skeletal anchorage combined with predistraction alveolar bone grafting (ABG) in cleft maxilla. Design Case report. Patient A patient with numerous congenital missing teeth and severe maxillary deficiency related to complete bilateral cleft lip and palate with large alveolar bone defect. Intervention The patient received preoperative orthodontic treatment, predistraction ABG, and maxillary distraction osteogenesis using RED with skeletal anchorage. Results Predistraction ABG completely united the cleft maxilla. The united maxilla was successfully advanced by the RED system with skeletal anchorage, despite unsound dentition with numerous congenital missing teeth. Conclusion The present study demonstrates that the combination of predistraction ABG and RED system with skeletal anchorage is effective for the treatment of severe maxillary deficiency related to complete bilateral cleft lip and palate with large bone defect and numerous congenital missing teeth.
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K, Padmanabham,, Rambabu, K, and Sairam, K. "Modelling Studies of Retrofitted Anchorage System in Exterior Beam Column Joint by Supplementary Steel." Saudi Journal of Civil Engineering 6, no. 9 (September 4, 2022): 215–34. http://dx.doi.org/10.36348/sjce.2022.v06i09.001.
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A Nonlinear finite element based ABAQUS modeling studies were conducted to evaluate the performance of exterior Beam Column Joint (BCJ) under quasi-static test loads. Six integrated BCJ models representing different configurations of beam reinforcement anchored in joint are verified by using a novel retrofitting technique called "Post Installation of Supplementary Anchorage" (PISA) by using headed bar as supplementary steel. The configuration of beam reinforcement anchored in column are described by straight bar,90 degree bend ,180 degree hook (confirming to design code IS456:2000) and single head, double head bars (confirming to ACI 318-19, ACI 352R-02 ) and 90 degree long bend of ductile detailing (as per IS 13920-2016). Two series (A&B) of integrated joint specimens representing conventional (series-A) and retrofitted anchorage (series-B) systems are modeled and tested by using ABAQUS software. The test parameters considered are configuration of anchorage system and presence of supplementary anchorage. The test variables representing nonlinear performance of retrofitted joint system are Von Mises stress conditions, Principal tensile stress, Moment-Rotation, Degraded stiffness, Crack mechanics and Damage index. The results shows good improvement of post failure conditions of exterior beam-column joint such as relocation of plastic hinge mechanism and failure mechanics of retrofitted joint system. Also the results validated with experimental program on typical specimens casted and tested. This study imparts useful information on implicit retrofitting methods applied by external means in exterior beam-column joint. It also promotes performance based design principles with viable construction practice.
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Bencardino, Francesco, Vincenzo Colotti, Giuseppe Spadea, and Ramnath Narayan Swamy. "Shear behavior of reinforced concrete beams strengthened in flexure with bonded carbon fibre reinforced polymers laminates." Canadian Journal of Civil Engineering 32, no. 5 (October 1, 2005): 812–24. http://dx.doi.org/10.1139/l05-027.
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The aim of this paper is to clarify the structural performance of reinforced concrete (RC) beams with weak or without any internal shear reinforcement and externally strengthened in flexure with carbon fibre reinforced polymer (CFRP) laminates, when subjected to a shear-dominant-loading regime. Seven RC beams were specifically designed, without and with an external anchorage system, which was carefully detailed to enhance the benefits of the strengthening laminate and counteract the destructive effects of shear forces. All the beams were identical in terms of their geometry, longitudinal internal reinforcement, and concrete strength but varied, to highlight the role of shear behavior, in terms of their internal and external shear reinforcement as well as in their loading test regime. The beams were tested under four-point bending and extensively instrumented to monitor strains, deflection, cracking, load carrying capacity, and failure modes. The structural response of the tested beams has, then, been critically analyzed in terms of deformability, strength, and failure processes that occur under a shear-dominant loading regime. It is shown that with a carefully designed anchorage system, a brittle behavior without yielding of tension steel reinforcement of a flexural strengthened beam can be transformed to a less brittle behavior with yielding of tension steel reinforcement and a well-defined enhancement of structural performance in terms of both deformation and strength. The results presented in this paper should enable engineers to counteract shear failure of externally strengthened beams with little or even no internal shear reinforcement.Key words: carbon fibre reinforced polymer, shear behavior, external flexural strengthening, structural performance.
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Breveglieri, Matteo, Christoph Czaderski, and Julien Michels. "The Gradient Anchorage Method for Prestressed CFRP Strips: from the Development to the Strengthening of an 18 M Long Bridge Girder." Slovak Journal of Civil Engineering 26, no. 3 (September 1, 2018): 29–40. http://dx.doi.org/10.2478/sjce-2018-0018.
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Abstract The external bonding of carbon fiber-reinforced polymer (CFRP) strips by two-component epoxy adhesive on the concrete surfaces of buildings and bridges is a retrofitting method accepted worldwide. The gradient anchorage (GA) is an anchoring method especially developed to anchor prestressed CFRP strips to concrete elements without a need for mechanical clamping after the installation phase. This method takes advantage of the adhesives property to undergo accelerated curing when heated. The results of more than fifteen years of research on the development of the gradient anchorage at the Swiss Federal Laboratories for Materials Science and Technology (Empa) are presented in this paper. The basic principles and application steps are explained, and the main results starting from the development of the technique up to the testing of real scale girders are described, and the new challenges posed by this innovative system are highlighted. The gradient anchorage is a valid alternative to a mechanically anchored system for prestressed FRP (P-FRP).
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Lee, Swoo-Heon, Kyung-Jae Shin, and Hee-Du Lee. "Post-Tensioning Steel Rod System for Flexural Strengthening in Damaged Reinforced Concrete (RC) Beams." Applied Sciences 8, no. 10 (September 29, 2018): 1763. http://dx.doi.org/10.3390/app8101763.
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In this study, a post-tensioning method using externally unbonded steel rods was applied to pre-damaged reinforced concrete beams for flexural strengthening. Nine simply-supported beams, three reference beams and six post-tensioned beams, were subjected to three-point bending. The design parameters observed in this study were the amount of tension reinforcements (3-D19, 4-D19, and 2-D22 + 2-D25; “D” indicates the nominal diameter of the rebar) and the diameters of the external rod (φ22 mm and φ28 mm). A V-shaped profile with a deviator at the bottom of the mid-span was applied to the pre-damaged beams, and a post-tensioning force was added to overcome the low load resistance and deflection already incurred in the pre-loading state. The post-tensioning force caused by tightening the nuts at the anchorage corresponded to a strain of 2000 με in the external rods; this value was approximately equal to the strain caused by torque that two adults can apply conveniently. The post-tensioning system increased the load-carrying capacity and flexural stiffness by approximately 40–112% and 28–73%, respectively, when compared with the control beams. However, the external rods did not yield in the post-tensioned beam with larger steel reinforcements and external steel rods. The external rod with the larger diameter increased the flexural strength more effectively.
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Ma, Rong Quan, Dong Mei Miao, Ming Lei Ma, and Gui Ling Wang. "Integrated Construction Technology of Building Structures with External Thermal Insulation Board." Applied Mechanics and Materials 472 (January 2014): 1057–60. http://dx.doi.org/10.4028/www.scientific.net/amm.472.1057.
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Integrated construction technology is in developing quickly in Chinas civil engineering community. With its space saving and heat insulation properties, people both in cold and hot region both need the thin wall settled structure to avoid burning hot or extremely cold. This article proposed an innovative integrating construction technology that has gained more and more popularity in construction project by adoption of thin wall thermal insulation board. The detail of the anchorage of the structure surface and the board, bond together with a special nail, and the whole system was controlled by the fastening system. It is one type vertical integration strategy and will gain more competition advantages for the construction enterprises.
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Deng, Lang Ni, Hua Chen, and Kan Kang. "Flexural Strengthening of Reinforced Concrete Beams with Prestressed CFRP Plates." Advanced Materials Research 255-260 (May 2011): 3077–81. http://dx.doi.org/10.4028/www.scientific.net/amr.255-260.3077.
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Four medium -scale reinforced concrete beams were constructed and tested to investigate the effectiveness of external poststrengthening with prestressed carbon fiber reinforced polymer (CFRP) plates. The various variables included the strengthening method and the amount of prestressing. The experiments consisted of one control beam, one nonprestressed CFRP-bonded beam, and two prestressed CFRP-bonded beams, all the beams were subjected to four-point bending tests. In comparison to the control beam and the nonprestressed CFRP-bonded beam, the cracking load, yield load, ultimate load and stiffness of the beams with bonded prestressed CFRP plates were increased. The failure mode of the prestressed CFRP-plated beams was not debonding, but concrete crushing. After the debonding of the CFRP plates, the behaviour of the bonded CFRP-plated beams changed to that of unbonded CFRP-plated beams due to the effect of the anchorage system. The ductility of the beams strengthened with CFRP plates having the anchorage system was considered high if the ductility index was above 3.
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Damiani, Marco, Attilio Quadrino, and Nicola Nisticò. "FRP Cables to Prestress RC Beams: State of the Art vs. a Split Wedge Anchorage System." Buildings 11, no. 5 (May 17, 2021): 209. http://dx.doi.org/10.3390/buildings11050209.
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Versatility and high performance in terms of specific stiffness and strength, as well as non-corrosive sensitivity, make FRP (Fiber-Reinforced Polymer) cables a viable alternative to steel ones in the development of prestressing systems. On the other hand, the orthotropic and brittle nature of FRPs could trigger a premature failure of the cable in the anchorage system, for which several solutions have been proposed so far in civil structural applications. In this context, after a preliminary state of the art, the work introduces a split wedge anchorage for FRP (ϕ = 12 mm) cables proposing two different solutions for steel wedges having the external surface: either (1) a constant (3 degrees) slope or (2) a double slope obtained by shaping it with an angle of 3.0 degrees before and then of 3.1 degrees along the most tapered part. The goal was to exploit the nominal cable capacity (257 kN), avoiding stress peaks that cause its premature failure. The proposed solutions have been experimentally tested and, as far as the double angle solution is concerned, the failure loads were equal to 222 and 257 kN, denoting that the proposed solution can reach the cable capacity. Clearly, further investigations are needed to check the variability of the results and eventually improve the system.
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Karnezis, I. A., A. W. Miles, J. L. Cunningham, and I. D. Learmonth. "Axial preload in external fixator half-pins: a preliminary mechanical study of an experimental bone anchorage system." Clinical Biomechanics 14, no. 1 (January 1999): 69–73. http://dx.doi.org/10.1016/s0268-0033(98)00047-3.
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Minami, Katsuhiro, Yoshihide Mori, Kwon Tae-Geon, Hidetaka Shimizu, Miyuki Ohtani, and Yoshiaki Yura. "Maxillary Distraction Osteogenesis in Cleft Lip and Palate Patients with Skeletal Anchorage." Cleft Palate-Craniofacial Journal 44, no. 2 (March 2007): 137–41. http://dx.doi.org/10.1597/04-204.1.
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Objective: Maxillary distraction osteogenesis with the rigid external distraction (RED) system has been used to treat cleft lip and palate (CLP) patients with severe maxillary hypoplasia. We introduce maxillary distraction osteogenesis for CLP patients with skeletal anchorage adapted on a stereolithographic model. Patients: Six maxillary deficiency CLP patients treated according to our CLP treatment protocol had undergone maxillary distraction osteogenesis. Method: In all patients, computed tomography (CT) images were recorded preoperatively, and the data were transferred to a workstation. Three-dimensional skeletal structures were reconstructed with CT data sets, and a stereolithographic model was produced. On the stereolithographic model, miniplates were adapted to the surface of maxilla beside aperture piriforms. The operation performed involved a high Le Fort I osteotomy with pterygomaxillary disjunction. Miniplates were fixed to the maxillary segment with three or four screws and used for anchorage of the RED system. Retraction of the maxillary segment was initiated after 1 week. Results: The accuracy of the stereolithographic models was enough to adapt the miniplates so that there was no need to readjust the plates during surgery. Postoperative cephalometric analysis showed that the direction of the retraction was almost parallel to the palatal plane, and dental compensation did not occur. Conclusions: We performed maxillary distraction osteogenesis with skeletal anchorage adapted on the stereolithographic models. Excellent esthetic outcome and skeletal advancement were achieved without dentoalveolar compensations.
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Yiu, Chun Fai, Yoo-Jun Kim, WoonSeong Jeong, Hung-Lin Chi, and Min-Koo Kim. "A Study on the External Stone Cladding System in Production and Installation Stages: The Case of Hong Kong." Applied Sciences 10, no. 22 (November 19, 2020): 8207. http://dx.doi.org/10.3390/app10228207.
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The successful quality management of the external stone cladding system in production and installation stages is of vital importance to ensure the high quality of the completed system. Nevertheless, little research has been conducted in this area. This research aimed to report the current status of the external stone cladding system in the production and installation stages in Hong Kong. To do so, this paper examines its current practices and major issues occurred through case studies, questionnaire surveys, and interviews. The results revealed the insufficiency in control mechanism and quality control in the system in Hong Kong. Furthermore, the factors to ensure the quality of the two stages were determined. Lastly, this research suggested recommendations on the possible measures to improve the system quality: pre-testing of stone materials and anchorage system, quality assurance of suppliers and manufacturers, regular inspections and audits on production, and continuous site quality supervision and checklist. The findings and outcomes of the research could lead to actions to guarantee steady quality for the stone cladding façade.
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Hao, Jian Bin, and Yu Ming Men. "Mechanical Characteristics of Soil Anchor under Combined Water and Ground Loads." Advanced Materials Research 243-249 (May 2011): 2915–19. http://dx.doi.org/10.4028/www.scientific.net/amr.243-249.2915.
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Gradually, anchor is in the working state of tension, but its stress becomes rather complicated when influenced by some external factors such as water, ground loads, etc. Aiming at the problems that ground additional load or coupling action of water and the additional load are forced on soil slope, the axial strain distributions of anchor tendons were obtained by model test. The change rules of axial strain at anchor head, near to slip plane, and end of the anchorage were analyzed respectively. The results show that under ground loads, the strain of anchor is biggest at the anchor head, and it gradually decreases from outer to inner. Under combined water and ground load, the stress state of the anchor system changes from tension to bending, and the upper anchors are most urgently affected. The experimental results can supply a reference for design and research of soil anchor with similar conditions.
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Park, Nam Kyu, and Jung Hun Lee. "PoC (Proof of Concept) for Performance Monitoring Platform of Container Terminals." Journal of Marine Science and Engineering 8, no. 12 (November 28, 2020): 971. http://dx.doi.org/10.3390/jmse8120971.
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The purpose of this study is to prove the concept of the performance monitoring system of container terminals. PoC (Proof of Concept) is a realization of a certain method or idea in order to demonstrate its feasibility. The port authorities, such as government or local authority, are continually checking the performance of the terminals they invested in and want to reflect it in the development policy. They also want to increase competitiveness by checking performance levels, such as port handling volume, calling ships, resource utilization, and congestion. PPI (Port performance indicators) are classified into four categories: output (production), productivity, utilization, and service. In this study, 15 monitoring indicators for each stage by dividing the process from the ship’s entry to departure are defined. Four indicators, such as ship waiting ratio at anchorage, berth occupancy, storage occupancy, and truck turnaround time, are selected as PoC of monitoring platform. In addition, a method of collecting, processing, and expressing data on these four indicators in real time is presented. There are three steps to create PPI on monitoring platform. The information required for PPI is to be collected from the Port-MIS (Management Information System) and TOS (Terminal Operating System) databases. Second, the collected data from external entities are stored into the database after verification and classification. Third, descriptive PPI, predictive PPI are generated based on the input data. This study provides a 4-tier framework from the conceptual platform with the key elements of data presentation, data process and data interface and middleware. As a result of the study, it is proved to select monitoring indicators, define external entities, define internal elements of the system, develop systems, and present indicator results. However, in the process of collecting data outside the system, we have found there is confidential data of individual terminals. To this end, it is important to establish a mutual cooperation system for data collection.
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Rai, Gopal L. "Advanced Active Prestressed CFRP in RCC Structures." Advanced Materials Research 1129 (November 2015): 290–97. http://dx.doi.org/10.4028/www.scientific.net/amr.1129.290.
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. The need for rehabilitation of reinforced concrete structures is rapidly increasing. Fibre reinforced polymer (FRP) composite materials for concrete structures have high strength-to-weight ratios that can provide high prestressing forces while adding minimal additional weight to a structure. They also have good fatigue properties and exhibit low relaxation losses, both of which can increase the service lives and the load carrying capacities of reinforced concrete structures. Carbon fiber reinforced polymer (CFRP) composite system is integrated system based on carbon fibres and epoxy resins. By prestressing the CFRP laminates, the material is used more efficiently as a part of its tensile capacity is utilised and it contributes to the load bearing capacity under both service and ultimate load condition. This is an ideal technique as it combines the advantage of using noncorrosive and lightweight advanced composite material in the form of FRP laminates with high efficiency offered by external prestressing. An innovative mechanical anchorage system was developed to prestress the FRP laminates directly by jacking and reacting against the RCC structure.This paper describes the use of Prestressed CFRP laminates for strengthening of RCC structures including practical applications on slabs and bridges. Also it elucidates the post strengthening testing carried out for the validation of this technique.
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Feng, Zhe, Tao Ma, Bingxin Tian, Xinxin Jin, and Zilu Yuan. "Effects of Titanium Implant Combined with Nano-Indentation in the Vertical Control of Physiological Anchorage Spee’s Wire System Corrective Technology." Journal of Biomedical Nanotechnology 18, no. 6 (June 1, 2022): 1668–75. http://dx.doi.org/10.1166/jbn.2022.3373.
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In the current research, there was, in the vertical control of physiological anchorage spee’s wire system (PASS) technology, an investigation on the role of titanium implant technology in combination with nano-indentation experiment the present research. The human jaw was selected as the sample to be cut vertically, by doing do, to obtain a test slice of about 2 mm through a cutting machine following the nano-indentation test. The slice was frozen and preserved in normal saline and taken out during the test. 40 outpatients who underwent orthodontic therapy were chosen as the research objects and rolled in a random manner into a control category and an category of observation. Then, mechanical biological therapy (MBT) correction was conducted for the outpatients from the control category and PASS correction therapy based on the nano-indentation experiment was for outpatients from the category of observation. Following therapy, the therapy conditions of these two categories were compared, showing that the load was a fixed value and the depth of the indentation was increasing. Under the action of external force, the periodontal ligament might undergo elastic deformation, changing with duration. Dentition alignment duration, ligation duration, and deligation duration were less for participants in the observation group compared to those in the control category (P less than 0.05). The inclination between the longitudinal plane of the top central incisor and the sella juncture root point plane (UI-SN angle), the spacing between both the top mandibular teeth margin and the nasal root juncture molar seat point (UI-NA distance), and the angle between the upper and lower central incisor tooth axis and the NA connection (UI-NA angle) were all significantly less pronounced in the category of observation than in the control category (P less than 0.05). However, the angle of upper and lower central incisor long axis (UI-LI angle) from the category of observation was hugely greater than that of the control category (P less than 0.05). The value of dental arch width in the category of observation was smaller significantly than the value of the control category (P less than 0.05), and the changes in dental arch width were larger than those in the control category (P less than 0.05). Besides, the measured values of X-ray projections of outpatients from the category of observation were higher at of the control category (P less than 0.05). In conclusion, nano-indentation experiment can accurately match the equipment required in the therapy. The application of titanium materials combined with the vertical control of PASS correction technology can effectively alleviate the clinical symptoms of outpatients so as to improve the therapy effect.
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Mickovski, Slobodan B., and A. Roland Ennos. "The effect of unidirectional stem flexing on shoot and root morphology and architecture in young Pinus sylvestris trees." Canadian Journal of Forest Research 33, no. 11 (November 1, 2003): 2202–9. http://dx.doi.org/10.1139/x03-139.
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Mechanical stresses experienced by a tree during lateral loading may cause alterations in both shoot and root growth (thigmomorphogenesis). Many of the previous studies on this subject have concentrated on shoot responses to lateral loads, while root system responses to stresses caused by external loading have been investigated only in more recent years, and even then only rarely in trees. This study presents the effect of unidirectional stem flexure of young Scots pine (Pinus sylvestris L.) on their root system morphology and architecture. Apart from the changes to the parts of the tree aboveground, unidirectional periodical flexing induced an increase in total root cross-sectional area and larger biomass allocation to the roots parallel to the plane of flexing, which in turn resulted in a larger number of major lateral roots with larger cross-sectional area in the plane of flexing. Since there were no significant differences in root to shoot ratio or the mechanical properties of wood between flexed and unflexed trees in this study, the increase in the lateral resistance in flexed trees was associated with the greater proportion of total root biomass allocated to the proximal major lateral roots, which was an adaptive mechanism for improvement of the trees' anchorage.
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Benetti, Roberta, Tamara Copetti, Stefania Dell'Orso, Edon Melloni, Claudio Brancolini, Martin Monte, and Claudio Schneider. "The Calpain System Is Involved in the Constitutive Regulation of β-Catenin Signaling Functions." Journal of Biological Chemistry 280, no. 23 (April 7, 2005): 22070–80. http://dx.doi.org/10.1074/jbc.m501810200.
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β-Catenin is a multifunctional protein serving both as a structural element in cell adhesion and as a signaling component in the Wnt pathway, regulating embryogenesis and tumorigenesis. The signaling fraction of β-catenin is tightly controlled by the adenomatous polyposis coli-axin-glycogen synthase kinase 3β complex, which targets it for proteasomal degradation. It has been recently shown that Ca2+ release from internal stores results in nuclear export and calpain-mediated degradation of β-catenin in the cytoplasm. Here we have highlighted the critical relevance of constitutive calpain pathway in the control of β-catenin levels and functions, showing that small interference RNA knock down of endogenous calpain per se (i.e. in the absence of external stimuli) induces an increase in the free transcriptional competent pool of endogenous β-catenin. We further characterized the role of the known calpain inhibitors, Gas2 and Calpastatin, demonstrating that they can also control levels, function, and localization of β-catenin through endogenous calpain regulation. Finally we present Gas2 dominant negative (Gas2DN) as a new tool for regulating calpain activity, providing evidence that it counteracts the described effects of both Gas2 and Calpastatin on β-catenin and that it works via calpain independently of the classical glycogen synthase kinase 3β and proteasome pathway. Moreover, we provide in vitro biochemical evidence showing that Gas2DN can increase the activity of calpain and that in vivo it can induce degradation of stabilized/mutated β-catenin. In fact, in a context where the classical proteasome pathway is impaired, as in colon cancer cells, Gas2DN biological effects accounted for a significant reduction in proliferation and anchorage-independent growth of colon cancer.
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Roux, Yannick Le, and Loïc Pagès. "Développement et polymorphisme racinaires chez de jeunes semis d'hévéa (Hevea brasiliensis)." Canadian Journal of Botany 72, no. 7 (July 1, 1994): 924–32. http://dx.doi.org/10.1139/b94-117.
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The major problems (bad anchorage, water stress, and root disease) with the cropping of the rubber tree (Hevea brasiliensis) are related to the architecture of its root system. So, the morphogenetic properties of the various roots that emerge during the development of the young seedlings are described to improve our understanding of the dynamics of root system architecture. In this study, the development of the root system of 12 seedlings grown for 40 days in root observation boxes has been recorded on a daily basis and analysed. Additional observations were also made on plants grown in pots or in the field for a 60-day period. This analysis of the sequential differentiation of the root system allowed us to distinguish five different root types according to their spatial and temporal location at emergence: (i) taproot, (ii) early first-order lateral roots, (iii) acropetal first-order lateral roots, (iv) late first-order lateral roots, (v) second-order lateral roots. Large variations and close relationship were found within the growth and branching characteristics on one hand, and within anatomical characteristics on the other (number of xylem poles, external diameter, and stele diameter). These between-type variations were also observed, to a lesser extent, among roots from the same type. The continuity of these development characteristics, which were shown to be acquired early, led us to characterize a morphogenetic gradient. This gradient is a reference scale to understand the morphological plasticity of the root system growing in other mediums. Key words: root system, development, morphogenesis, anatomy, root observation box, Hevea brasiliensis.
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Zhu, Wen, Fengxuan Wang, Shiyu Sun, and Wenke Jia. "Research progress of FRP in steel and masonry bridge structures reinforcement." Advances in Engineering Technology Research 1, no. 2 (September 24, 2022): 529. http://dx.doi.org/10.56028/aetr.1.2.529.
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Fiber reinforced polymer (FRP) has been widely used in the reinforcement of concrete bridge structures, and it still has a good application prospect in the reinforcement of steel and masonry bridge structures. In order to summarize the research results of FRP in the reinforcement of steel and masonry structures, broaden the ideas of FRP strengthening bridges in China and promote its wide application in the field of bridge structure reinforcement, it is summarized from the aspects of anti-fatigue reinforcement, anti-buckling reinforcement, bearing capacity reinforcement and seismic reinforcement according to the different reinforcement mechanisms. The shortcomings of the existing studies were analyzed, some problems and ideas that can be further studied were put forward. Analysis result shows that the prestressed FRP reinforcement technology has a good application prospect because of its high material strength utilization rate. Generally, the method of prestressing FRP is used to strengthen the bridge steel members with fatigue cracks, and FRP and filler materials are used to form an external reinforcement system to improve the buckling resistance of steel members. FRP reinforcement can improve the bearing capacity and seismic performance of masonry structures. Follow-up studies should be continued to develop standardized prestressed FRP reinforcement and anchorage system with long-term reliable performance, further promote the engineering application of prestressed FRP reinforced steel structures and establish the specification system of FRP reinforced masonry bridges. The durability of FRP reinforced bridges under complex environment and coupling of various factors should be deeply studied.
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Zhu, Wen, Fengxuan Wang, Shiyu Sun, and Wenke Jia. "Research progress of FRP in steel and masonry bridge structures reinforcement." Advances in Engineering Technology Research 2, no. 1 (September 24, 2022): 529. http://dx.doi.org/10.56028/aetr.2.1.529.
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Fiber reinforced polymer (FRP) has been widely used in the reinforcement of concrete bridge structures, and it still has a good application prospect in the reinforcement of steel and masonry bridge structures. In order to summarize the research results of FRP in the reinforcement of steel and masonry structures, broaden the ideas of FRP strengthening bridges in China and promote its wide application in the field of bridge structure reinforcement, it is summarized from the aspects of anti-fatigue reinforcement, anti-buckling reinforcement, bearing capacity reinforcement and seismic reinforcement according to the different reinforcement mechanisms. The shortcomings of the existing studies were analyzed, some problems and ideas that can be further studied were put forward. Analysis result shows that the prestressed FRP reinforcement technology has a good application prospect because of its high material strength utilization rate. Generally, the method of prestressing FRP is used to strengthen the bridge steel members with fatigue cracks, and FRP and filler materials are used to form an external reinforcement system to improve the buckling resistance of steel members. FRP reinforcement can improve the bearing capacity and seismic performance of masonry structures. Follow-up studies should be continued to develop standardized prestressed FRP reinforcement and anchorage system with long-term reliable performance, further promote the engineering application of prestressed FRP reinforced steel structures and establish the specification system of FRP reinforced masonry bridges. The durability of FRP reinforced bridges under complex environment and coupling of various factors should be deeply studied.
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Gora, Abdurra’uf Mukhtar, Jayaprakash Jaganathan, Mohammed Parvez Anwar, and Hau Y. Leung. "Flexural capacity of bi-directional GFRP strengthened RC beams with end anchorages." International Journal of Structural Integrity 10, no. 2 (April 8, 2019): 188–207. http://dx.doi.org/10.1108/ijsi-04-2018-0021.
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Purpose The purpose of this paper is to present the results of experimental and theoretical studies on the flexural capacity of reinforced concrete (RC) beams strengthened using externally bonded bi-directional glass fibre reinforced polymer (GFRP) composites and different end anchorage systems. Design/methodology/approach A series of nine RC beams with a length of 1,600 mm and a cross-section of 200 mm depth and 100 mm width were prepared and externally strengthened in flexure with bi-directional GFRP composites. These strengthened beams were anchored with three different end anchorage systems namely closed GFRP wraps, GFRP U-wraps and mechanical anchors. All these beams were tested with four-point bending system up to failure. The experimental results are compared with the theoretical results obtained using the relevant design guidelines. Findings The experimental results demonstrate a significant increase in the flexural performance of the GFRP strengthened beams with regard to the ultimate load carrying capacity and stiffness. The results also show that GFRP strengthened beams without end anchorages experienced intermediate concrete debonding failure at the GFRP plate end, whereas all the GFRP strengthened beams with different end anchorage systems failed in rupture of GFRP with concrete crushing. The theoretical results revealed no significant difference among the relevant design guidelines with regard to the predicted ultimate moment capacities of the bi-directional GFRP strengthened RC beams. However, the results show that ACI Committee 440 Report (2008) design recommendation provides reasonably acceptable predictions for the ultimate moment capacities of the tested beams strengthened externally with bi-directional GFRP reinforcement followed by FIB Bulletin 14 (2001) and eventually by JSCE (1997). Originality/value The research work presented in this manuscript is authentic and could contribute to the understanding of the overall behaviour of RC beams strengthened with FRP and different end anchorage systems under flexural loading.
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Szlendak, Jerzy K., Agnieszka Jablonska-Krysiewicz, and Dariusz Tomaszewicz. "Assessment of the load capacity of the anchorage system connecting the textured layer with the structural wall of large slab buildings in the lights of experimental research and FEM analysis." MATEC Web of Conferences 174 (2018): 03016. http://dx.doi.org/10.1051/matecconf/201817403016.
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The goal of the article is to compare the results obtained from experimental tests of a new type of anchoring, connecting the texture layer with the structural layer in external wall elements, used in large-panel construction with the results from FEM analysis. Two types of samples were subjected to experimental tests: single-layer uniform concrete and three-layer concrete with embedded point anchors and analogous samples with glued anchors. The test elements used C 12/15 and C 30/37 concrete, 12 mm diameter anchors, made of steel corresponding to the grade of stainless steel screws class 5.8, Sika Anchorfix-1 resin and XPS polystyrene. As for the three-layer samples, when testing, two forces were applied: tearing and shearing due to the detachment of the textured layer. The ANSYS program was used for numerical modelling of the analyzed samples. 3D models were built in which solid elements were used. For steel anchors, the material characteristics were taken as a two-line elasticplastic reinforcement. The Drucker-Prager model was used in the concrete elements, the linear-elastic model was adopted for the resin, and the brittle model according to the linear-elastic fracture mechanics for the polystyrene.
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Cattaneo, Sara, Pietro Crespi, and Luigi Biolzi. "Structural Analysis and Design of Reinforced Concrete Bridge Corbels." Applied Sciences 10, no. 19 (September 25, 2020): 6727. http://dx.doi.org/10.3390/app10196727.
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Post-installed systems for the anchorage of safety barriers to bridge corbels are widely used today thanks to their flexibility and easiness of installation. Because of commonly found in situ boundary constraints, however, the design requirements for post-installed fasteners and rebars are frequently not satisfied or only partially satisfied. This paper assesses the mechanical response of a corbel where an innovative solution concerning the placement of post-installed reinforcement in reinforced concrete members was suggested. With reference to the refurbishment of bridge curbs, which usually requires concrete removal in the damaged top layers, the proposed method was based on the introduction of additional U-shaped post-installed rebars connecting the existing portion of the corbel to the newly cast top layer, in order to allow the transfer of the tension pull-out force exerted by the posts restraining the safety barrier. The layout investigated in this paper consisted of three anchors connecting the baseplate of the post supporting the safety barrier to the corbel (a layout commonly found in Italy). These anchors transfer the external actions (bending moment and shear) to the corbel thanks to the formation of a strut-and-tie system where the U-shaped rebars and the existing reinforcement play a crucial role. A strut-and-tie model of the corbel was presented to allow the use of a simplified approach to assess the safety of the corbel. The tests on real-scale specimens were also modeled numerically and additional models were considered to evaluate the effect of characteristics parameters (i.e., size of the corbel, existing shear reinforcement, etc.) on the overall response of the corbel.
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Letcham, K., and P. Vincent. "U-type mechanical clamping to anchor the CFRP composites in strengthening of RC beams subjected to bending." Composites and Advanced Materials 30 (January 1, 2021): 263498332110035. http://dx.doi.org/10.1177/26349833211003578.
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The present study investigates the performance of U-type clamp anchorage on external strengthening of reinforced concrete beams using carbon fibre-reinforced polymer composites. Unidirectional carbon fibre was used to strengthen the beam having a cross-section of 150 × 200 mm2 and the fabricated U-type clamp was used as a clamping device to enhance the fibre-reinforced polymer (FRP) bonding. To test the beam, four-point bending system was adopted and the experimental parameters were the number of FRP layers. The failure mode of strengthened beams with U-type clamp was very similar (rupture of FRP composites) to the beams without U-type clamp. However, the delamination of FRP was evaded by counteracting the peeling stress development at the edge of fibre. Since the beams strengthened with U-type clamp exhibited more linear behaviour than that of the beams strengthened without U-type clamp, there may be a higher possibility for abrupt/rapid/brittle mode of failure and the ductility index of the beam with U-type clamp confirmed the above behaviour. However, the introduction of U-type clamp enhanced the flexural stiffness and ultimate strength by counteracting the debonding, and the beam with U-type clamp exhibited a maximum of 58.33% and 20.37% enhancement in flexural stiffness and ultimate strength than that of the beam without U-type clamp, respectively. The theoretical strength value of all strengthened beams was evaluated using models proposed in the previous research and compared with experimental results. It is inferred that the use of U-type clamp in FRP strengthening provides economic and structural benefits compared to a beam without U-type clamp.
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Lee, Chu, Lin, Kung, Lin, and Lee. "Root Traits and Biomechanical Properties of Three Tropical Pioneer Tree Species for Forest Restoration in Landslide Areas." Forests 11, no. 2 (February 5, 2020): 179. http://dx.doi.org/10.3390/f11020179.
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Frequent earthquakes, monsoon torrential rains and typhoons cause severe landslides and soil erosion in Taiwan. Hibiscus taiwanensis, Macaranga tanarius, and Mallotus paniculatus are major pioneer tree species appearing on landslide-scarred areas. Thus, these species can be used to restore the self-sustaining native vegetation on forest landslides, to control erosion, and to stabilize slope. However, their growth performance, root traits and biomechanical properties have not been well characterized. In this study, root system and root traits were investigated using the excavation method, and biomechanical tests were performed to determine the uprooting resistance, root tensile strength and Young’s modulus of 1-year-old Hibiscus taiwanensis, Macaranga tanarius, and Mallotus paniculatus seedlings. The results reveal that relative to H. taiwanensis, M. tanarius and M. paniculatus seedlings had significantly larger root collar diameter, longer taproot length, higher root biomass, higher root density, higher root length density, heavier root mass, larger external root surface area, higher root tissue density, larger root volume, longer total root length, and a higher root tip number. Additionally, the height of M. paniculatus seedlings was significantly higher than those of H. taiwanensis and M. tanarius. Furthermore, the uprooting resistance and root tensile strength of M. paniculatus seedlings was significantly higher than those of H. taiwanensis and M. tanarius. Young’s modulus of M. paniculatus and M. tanarius seedlings was also significantly higher than that of H. taiwanensis. These growth characteristics and biomechanical properties demonstrate M. paniculatus and M. tanarius are superior than H. taiwanensis, considering growth performance, root anchorage capability, tensile strength and Young’s modulus. Taken as a whole, the rank order for species selection of these pioneer species for reforestation comes as: M. paniculatus M. tanarius H. taiwanensis. These results, along with knowledge on vegetation dynamics following landslides, allow us to better evaluate the effect of selective removal management of pioneer species on the resilience and sustainability of landslides.
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Zhuang, Ning, Junzhou Chen, Miao Zheng, and Da Chen. "Flexural experimental study on reinforced concrete beams strengthened with carbon fiber-reinforced polymer laminates using anchorage systems." Materials Express 9, no. 8 (November 1, 2019): 923–30. http://dx.doi.org/10.1166/mex.2019.1575.
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Flexural capacity of RC beams gets significant improvement with externally bonded Carbon Fiber-reinforced Polymer (CFRP) sheet. The anchorage system is a valid means to restrain or delay debonding failure caused by stress concentration at the ends of CFRP sheets. In this paper, four RC beams, measuring 150 × 200 × 1900 mm, were examined under four-point bending test. One beam was applied for contrast. And other three were CFRP strengthened with no anchorage, CF anchors (carbon fiber anchors) and U-wraps (U-shaped CFRP wraps). The primary purpose of the experiment was to validate the effectiveness of CF anchors and U-wraps in improving the flexure character of beams strengthened with CFRP sheets. The experimental results revealed that the strengthened beams using anchorage systems performed remarkably in beam ductility, flexural capacity, load-deflection response and failure mode compared with the contrast beam. The anchorage systems were more effective and necessary to enhance the flexural behavior of beams as using CFRP laminates for flexural strengthening.
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Grelle, Stephen V., and Lesley H. Sneed. "Review of Anchorage Systems for Externally Bonded FRP Laminates." International Journal of Concrete Structures and Materials 7, no. 1 (March 2013): 17–33. http://dx.doi.org/10.1007/s40069-013-0029-0.
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Ibrahim, Wael R., and Waleed A. Ali. "Comparison of Anchorage Systems for Externally Bonded FRP Laminates." International Journal of Engineering and Technology 11, no. 6 (December 31, 2019): 1128–35. http://dx.doi.org/10.21817/ijet/2019/v11i6/191106012.
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Zhang, Xue, Zhimin Wu, and Ye Cheng. "An approach of steel plate hybrid bonding technique to externally bonded fibre-reinforced polymer strengthening system." International Journal of Distributed Sensor Networks 14, no. 6 (June 2018): 155014771878645. http://dx.doi.org/10.1177/1550147718786455.
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The strengthening efficiency of externally bonded fibre-reinforced polymer to concrete structure is usually limited owing to the unexpected debonding of fibre-reinforced polymer laminates. In this study, a new steel plate hybrid bonding technique was developed to supply additional anchorage for traditional externally bonded fibre-reinforced polymer strengthening system. With this approach, the fibre-reinforced polymer debonding can be effectively prevented. Moreover, the stress concentration, which probably results in a premature fracture of fibre-reinforced polymer laminates as that performed for available hybrid bonding anchorage techniques, can be eliminated by introducing a steel plate between the mechanical fasteners and fibre-reinforced polymer strips. To verify the effect of this new method, 21 carbon fibre–reinforced polymer–strengthened beams were studied on the flexural behaviours. Test results showed that, compared to available hybrid bonding anchorage techniques, steel plate hybrid bonding is more capable of making the full use of fibre-reinforced polymer laminates and further enhance the ultimate capacity and ductility of externally bonded fibre-reinforced polymer–strengthened beams. Based on the experimental results, the effect of interfacial treatment, ply of carbon fibre–reinforced polymer and mechanical fastener spacing on the failure mode and ultimate load ratio were discussed. Eventually, a simplified analytical procedure was proposed and verified to estimate the flexural resistance of steel plate hybrid bonding – fibre-reinforced polymer–strengthened beam.
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Baryłka, A., and D. Tomaszewicz. "Anchorages bonded system in experimental research and their comparison with FEM models." Journal of Achievements in Materials and Manufacturing Engineering 2, no. 106 (June 1, 2021): 49–55. http://dx.doi.org/10.5604/01.3001.0015.2417.
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Purpose: The topic of this article is the use of anchors bonded in the outer walls of threelayer large slab panel buildings in Poland. Design/methodology/approach: Comprehensive laboratory tests of anchoring systems bonded in various configurations were carried out. On this basis, the theoretical load capacity of the new bonded anchorages can be estimated. Findings: These considerations are the aftermath of the current problem of the former large slab panel buildings in Poland, and more specifically the risk of detachment of the external textured layer in the walls of three-layer large slab panel buildings. Research limitations/implications: The presented variants of experimental research and their comparison with the MES analysis indicate the directions of conduct in strengthening three-layer walls. It should be remembered that the use of additional reinforcement anchorages is practically a necessity, as the next stage of renewing large slab panel buildings is their thermo-modernization. Practical implications: This process results in an increase of the load on the external textured layer, and hence also on hangers. Originality/value: Experimental research is aimed at determining the optimal variant of application of bonded anchors.
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Wang, Hai-Tao, Zhi-Ning Bian, Guo-Wen Xu, Min-Sheng Chen, Hao Xiong, and Sai-Sai Liu. "Flexural Strengthening of Large-Scale RC Beams with Nonprestressed and Prestressed CFRP Using Different Anchorages." Polymers 14, no. 24 (December 15, 2022): 5498. http://dx.doi.org/10.3390/polym14245498.
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Externally bonded carbon-fiber-reinforced polymer (CFRP) technology can be used by different methods based on the anchorage device, CFRP type, and prestressing/nonprestressing. However, a direct comparison between the strengthening efficacies of different methods is still lacking. Seven large-scale RC beams were tested in this study to investigate the influences of the anchorage method, CFRP type, prestress, and prestressing system on the flexural strengthening efficacy of RC beams. The test results showed that the ultimate load increased by 38.3%, whereas the cracking and yielding loads were slightly affected when the anchorage method was enhanced from CFRP U-wraps to wedge-clamp anchors. The CFRP plate and CFRP sheet could provide a rather close flexural strengthening efficacy under the same CFRP strengthening amount. Compared to the nonprestressed CFRP plate, the prestressed CFRP plate was highly superior in improving the flexural behavior of RC beams. The cracking, yielding, and ultimate loads of the prestressed CFRP-strengthened specimens were 57.1%, 22.9%, and 5.9%, respectively, higher than those of the nonprestressed CFRP-strengthened specimen with an effective anchorage. The two types of prestressing systems based on the adhesive-friction anchor and wedge-clamp anchor were proven to be effective for flexural strengthening of RC beams with prestressed CFRP plates, and they could provide almost the same strengthening effect.
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Akbarzadeh Bengar, Habib, and Amir Ali Shahmansouri. "A new anchorage system for CFRP strips in externally strengthened RC continuous beams." Journal of Building Engineering 30 (July 2020): 101230. http://dx.doi.org/10.1016/j.jobe.2020.101230.
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Al-Saawani, Mohammed A., Ahmed K. El-Sayed, and Abdulaziz I. Al-Negheimish. "Mitigation of Concrete Cover Separation in Concrete Beams Strengthened with Fiber-reinforced Polymer Composites." IOP Conference Series: Earth and Environmental Science 1026, no. 1 (May 1, 2022): 012008. http://dx.doi.org/10.1088/1755-1315/1026/1/012008.
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Abstract Strengthening of reinforced concrete (RC) beams using fiber reinforced polymers (FRP) is an effective method that is gaining more acceptance worldwide. However, failure of the strengthened beams at the plate-end region by concrete cover separation (CCS) compromises the effectiveness of such a strengthening system. Among available anchorage systems to remedy such problem, the use of FRP U-wraps at the end region of the externally bonded FRP has the potential to prevent CCS failure. Most studies in the literature suffer from poor design of test specimens and the use of random amounts of FRP anchorage. This resulted in nonconclusive findings and contradicting results on the real effectiveness of FRP U-wraps as an anchorage to prevent plate-end debonding failure. That in turn has been reflected in the lack of reliable design methods for the design of FRP U-wrap anchorage. In this paper, the effect of FRP U-wraps on the mitigation of CCS failure in FRP-strengthened RC beams was experimentally examined and quantified. The study included full-scale RC beams strengthened in flexure using carbon FRP (CFRP) sheets and anchored at the plate-end region using vertical CFRP U-wraps. The test variable was the amount of CFRP U-wrap that is required to achieve complete mitigation of CCS. The test results indicated the effectiveness of FRP U-wraps on mitigating CCS failure once the required area of CFRP U-wrap was placed. Relevant design models were presented and assessed against the experimental results of the current study. The comparisons indicated inaccurate predictions for the area of FRP U-wrap that is required to prevent CCS. This sheds the light on the need for developing a more reliable and accurate method for the design of an end anchorage to prevent CCS failure.
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Al-Atta, B., R. Kalfat, R. Al-Mahaidi, and A. Al-Mosawe. "Influence of anchorage systems on externally-bonded CFRP sheets used for flexural strengthening." IOP Conference Series: Materials Science and Engineering 671 (January 17, 2020): 012105. http://dx.doi.org/10.1088/1757-899x/671/1/012105.
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Mohamed, Khalid, Jamal A. Abdalla, and Rami A. Hawileh. "Experimental and Analytical Investigations of the Use of Groove-Epoxy Anchorage System for Shear Strengthening of RC Beams Using CFRP Laminates." Materials 13, no. 19 (September 30, 2020): 4350. http://dx.doi.org/10.3390/ma13194350.
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Reinforced concrete (RC) beams strengthened in shear with carbon fiber reinforced polymer (CFRP) laminates as externally bonded reinforcement (EBR) usually fail due to debonding. This paper presents an experimental and analytical investigation on the use of groove-epoxy as an anchorage system for CFRP plates and sheets bonded on both sides of shear deficient RC beams. The aim of this study is to assess the effectiveness of using groove-epoxy in enhancing the shear capacity of RC beams. Nine rectangular RC beams were strengthened with CFRP plates and sheets with groove-epoxy anchorage systems of different groove widths and tested under four point bending. It is observed that the RC beams strengthened with the groove-epoxy anchorage system showed an increase in the shear-strength over the unstrengthened control beam up to 112 and 141% for plates and sheets, respectively. Also, the increase of shear-strength contribution of the groove-epoxy system to that of CFRP without grooves ranged between 30–190% for CFRP plates and between 40–100% for CFRP sheets. Generally, the contributions of groove-epoxy on shear-strength decreased with the increase of groove width. Moreover, shear strength prediction models, based on modifications of the ACI440.2R-17 shear model, were developed by incorporating groove factors as a modifier to the FRP shear-strength contribution. The developed models predicted the experimental shear-strength of the tested RC beams with a good level of accuracy, with an average mean absolute percent error (MAPE) = 3.31% and 6.68%, normalized mean square error (NMSE) = 0.072, 0.523, and coefficient of determination R2 = 0.964, 0.691, for plates and sheets, respectively.
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Aules, Wisam, Yasir M. Saeed, and Franz N. Rad. "A novel anchorage system for strengthening slender RC columns with externally bonded CFRP composite sheets." Construction and Building Materials 245 (June 2020): 118423. http://dx.doi.org/10.1016/j.conbuildmat.2020.118423.
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Deng, Lang Ni, Peng Zhang, and Hua Chen. "Flexural Behaviour of RC Beams Strengthened with Prestressed CFRP Plates：Comparisons of Bonded and Unbonded Method." Key Engineering Materials 480-481 (June 2011): 283–87. http://dx.doi.org/10.4028/www.scientific.net/kem.480-481.283.
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In this study, a total of 5 CFRP-strengthened reinforced concrete beams were tested in flexure based on the independent development prestressing anchorage system. The various variables included bonding or no bonding of the CFRP and the amount of prestressing. The experiments consisted of one control beam, two prestressed CFRP-unbonded beams, and two prestressed CFRP-bonded beams, all the beams were subjected to four-point bending tests. The ultimate load, deformation, and CFRP strain were examined. The aim of this investigation was to study the flexural performance of reinforced concrete members strengthened using CFRP plates, employing different CFRP bonding and prestressing methods. The failure mode of the prestressed CFRP-plated beams was not debonding, but concrete crushing or FRP rupture. For the reinforced concrete members strengthened with externally bonded prestressed CFRP plates, after the debonding of the CFRP plates that occurred in the bonded cases, the behaviour of the bonded CFRP-plated beams changed to that of the unbonded CFRP-plated beams due to the effect of the anchorage system. The ductility indices of the beams in an unbonded system were less than that of those in a bonded system.
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Lee, Ming Ju, Ming Gin Lee, Yi Shuo Huang, and Yang Hsin Liang. "Durability of Broken Concrete Specimens Strengthened with CFRP Sheets." Advanced Materials Research 123-125 (August 2010): 1119–22. http://dx.doi.org/10.4028/www.scientific.net/amr.123-125.1119.
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Carbon fiber-reinforced polymer (CFRP) composites are thin laminates that are externally bonded to broken concrete specimens using an epoxy system to increase their load-carrying capacity in this study. This paper reports the test results of broken concrete specimens strengthened with CFRP sheets and subjected to two aggressive environments including ultraviolet (UV) and freeze-thaw cycles. Test results revealed that three different CFRP layers are effective in retrofit on the broken compressive or flexural concrete specimens. The broken concrete specimens repaired with an epoxy and CFRP system could improve their compressive strength, flexural strength or ductility. Both aggressive environment tests didn’t cause obvious degradation to hardness index, compressive or flexural strength. The flexural specimens used half-U coating and anchorage systems were much higher strength than those only wrapped with CFRP sheets on the flat surface.
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Barris, Cristina, Luís Correia, and José Sena-Cruz. "Experimental study on the bond behaviour of a transversely compressed mechanical anchorage system for externally bonded reinforcement." Composite Structures 200 (September 2018): 217–28. http://dx.doi.org/10.1016/j.compstruct.2018.05.084.
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Bae, Sang-Wook, and Abdeldjelil Belarbi. "Behavior of Various Anchorage Systems Used for Shear Strengthening of Concrete Structures with Externally Bonded FRP Sheets." Journal of Bridge Engineering 18, no. 9 (September 2013): 837–47. http://dx.doi.org/10.1061/(asce)be.1943-5592.0000420.
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El-Mandouh, Mahmoud A., Jong Wan Hu, Won Sup Shim, Fathi Abdelazeem, and Galal ELsamak. "Torsional Improvement of RC Beams Using Various Strengthening Systems." Buildings 12, no. 11 (October 24, 2022): 1776. http://dx.doi.org/10.3390/buildings12111776.
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Many structural elements are subjected to a significant torsional moment that affects the structural design and may require strengthening. This paper presents different effective strengthening techniques to enhance the torsional capacity of reinforced concrete (RC) beams. An experimental and numerical investigation was undertaken to evaluate the efficacy of utilizing various strengthening systems. The experimental program included six full-scale RC beams with a cross-section dimension of (150 mm × 300 mm) and a length of 1500 mm, split into one beam without strengthening as a control beam, and six beams strengthened with various materials. The various strengthening materials were wrapped aluminum strips with anchorage bolts, wrapped stainless steel strips with anchorage bolts, wrapped glass fiber reinforcement polymer (GFRP), one layer of wrapped steel wire, and two layers of wrapped steel wire meshes along the beam. The results showed that the ultimate torque of the beam strengthened by wrapped aluminum strips and the beam strengthened by wrapped stainless steel strips was larger than the control beam by about 32% and 40%, respectively, because the strips acted as an external reinforcement. In addition to the strengthening systems, using aluminum strips and stainless steel strips is effective in raising the capacity to a similar degree despite the high cost of the stainless steel strips. The ultimate torque of the beams strengthened by GFRP, one-layered wrapped steel wire meshes, and two-layered wrapped steel wire meshes along the beam is larger than the control beam by about 62%, 118%, and 163%, respectively, in addition to the ultimate angle of twist, which was larger than the control beam by about 53%, 93%, and 126%, respectively. This showed that the strengthening using the two-layered wrapped steel wire meshes along the beam would be very significant in increasing the ultimate torque strength. Moreover, the strengthened beam by two-layered fully wrapped steel wire meshes along the beam developed the highest ductility factor compared to all strengthened beams; in contrast, the beam strengthened by GFRP had less ductility. To verify the outcomes of the experimental tests, a finite-element program, ABAQUS, was performed. Finally, an excellent agreement between the experimental and numerical results was obtained.
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El-Hacha, Raafat, and Khaled Soudki. "Prestressed near-surface mounted fibre reinforced polymer reinforcement for concrete structures — a review." Canadian Journal of Civil Engineering 40, no. 11 (November 2013): 1127–39. http://dx.doi.org/10.1139/cjce-2013-0063.
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The specialized application of prestressing the near-surface mounted (NSM) fibre reinforced polymer (FRP) reinforcement for strengthening reinforced concrete (RC) structures combines the benefits of the FRP reinforcement with the advantages associated with external prestressing. By applying a prestress to the NSM FRP the material is used more efficiently since a greater portion of its tensile capacity is employed. This paper presents a comprehensive review on the performance of RC members strengthened using prestressed NSM FRP reinforcement. Several techniques and anchorage systems developed to prestress the NSM FRP are presented. The static flexural and fatigue performance of RC beams strengthened using prestressed NSM FRP in comparison to non-prestressed NSM is presented. Research on the long-term performance under freeze–thaw exposures and sustained loading is also presented.
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Recupero, Antonino, Nino Spinella, Piero Colajanni, and Cosimo D. Scilipoti. "Increasing the Capacity of Existing Bridges by Using Unbonded Prestressing Technology: A Case Study." Advances in Civil Engineering 2014 (2014): 1–10. http://dx.doi.org/10.1155/2014/840902.
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External posttensioning or unbonded prestressing was found to be a powerful tool for retrofitting and for increasing the life extension of existing structures. Since the 1950s, this technique of reinforcement was applied with success to bridge structures in many countries, and was found to provide an efficient and economic solution for a wide range of bridge types and conditions. Unbonded prestressing is defined as a system in which the post-tensioning tendons or bars are located outside the concrete cross-section and the prestressing forces are transmitted to the girder through the end anchorages, deviators, or saddles. In response to the demand for a faster and more efficient transportation system, there was a steady increase in the weight and volume of traffic throughout the world. Besides increases in legal vehicle loads, the overloading of vehicles is a common problem and it must also be considered when designing or assessing bridges. As a result, many bridges are now required to carry loads significantly greater than their original design loads; and their deck results still deteriorated by cracking of concrete, corrosion of rebars, snapping of tendons, and so forth. In the following, a case study about a railway bridge retrofitted by external posttensioning technique will be illustrated.
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Bencardino, Francesco, and Mattia Nisticò. "A Theoretical Model for Debonding Prediction in the RC Beams Externally Strengthened with Steel Strip and Inorganic Matrix." Materials 14, no. 17 (August 31, 2021): 4961. http://dx.doi.org/10.3390/ma14174961.
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This paper shows a theoretical model for predicting the moment–curvature/load–deflection relationships and debonding failure of reinforced concrete (RC) beams externally strengthened with steel reinforced geopolymeric matrix (SRGM) or steel reinforced grout (SRG) systems. Force equilibrium and strain compatibility equations for a beam section divided into several segments are numerically solved using non-linear behaviour of concrete and internal steel bars. The deflection is then obtained from the flexural stiffness at a mid-span section. Considering the appropriate SRGM-concrete bond–slip law, calibrated on single-lap shear bond tests, both end and intermediate debonding failures are analysed. To predict the end debonding, an anchorage strength model is adopted. To predict intermediate debonding, at each pair of flexural cracks a shear stress limitation is placed at concrete–matrix interface and the differential problem is solved at steel strip–matrix interface. Based on the theoretical predictions, the comparisons with experimental data show that the proposed model can accurately predict the structural response of SRGM/SRG strengthened RC beams. It can be a useful tool for evaluating the behaviour of externally strengthened RC beams, avoiding experimental tests.
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Lau, David T., and Joshua E. Woods. "A concentric tube anchor system for fiber-reinforced polymer retrofit of reinforced concrete structural walls under extreme loads." International Journal of Protective Structures 9, no. 1 (October 4, 2017): 77–98. http://dx.doi.org/10.1177/2041419617732353.
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In reinforced concrete elements strengthened with fiber-reinforced polymer sheets, premature debonding of the fiber-reinforced polymer from the concrete substrate occurs due to lack of anchorage, which reduces the efficiency of the retrofitting system. This article reviews several common anchor systems and describes the development, optimization, and testing of a steel tube anchor in retrofit of reinforced concrete structural elements using externally bonded fiber-reinforced polymer sheets suitable for application to improve resistance against extreme load conditions (e.g. blast, impact, or an earthquake). A detailed review of common anchor designs including the proposed tube anchor based on previous studies on flexure-dominated fiber-reinforced polymer-strengthened reinforced concrete shear walls is presented. In this study, finite element analysis is conducted to verify the observed behavior and better understand the deformation mechanisms of the tube anchor. Finite element modeling is then used to evaluate the influence of different design parameters on its performance and propose a design methodology that can be used to optimize the tube anchor design. To verify the performance of the optimized tube anchor, it is tested in an experimental program on the in-plane seismic strengthening of two shear-dominated squat walls strengthened using fiber-reinforced polymer sheets. Experimental results reveal that the optimized tube anchor performs well in preventing premature debonding and allows the fiber-reinforced polymer composite to achieve a higher level of strain when compared to an alternative anchor system. Finally, a set of design steps for the implementation of the tube anchor in fiber-reinforced polymer retrofit applications for reinforced concrete shear walls are presented.
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de Menezes, Eduardo Antonio Wink, Laís Vasconcelos da Silva, Carlos Alberto Cimini Junior, Felipe Ferreira Luz, and Sandro Campos Amico. "Numerical and Experimental Analysis of the Tensile and Bending Behaviour of CFRP Cables." Polymers and Polymer Composites 25, no. 9 (November 2017): 643–50. http://dx.doi.org/10.1177/096739111702500901.
Full textAbstract:
Due to their high fatigue life, specific strength and specific stiffness in comparison with steel, carbon-fibre reinforced polymer (CFRP) cables have attracted the infrastructure industry interest in recent years, primarily for use as structural tendons. Particularly the oil and gas industry showed interest for application in offshore platform anchorage systems, because of their exceptional corrosion and creep/relaxation behaviour. In such applications, the cables need to be tensioned in service and to be bent around relatively small-diameter spools for transportation and maintenance. Therefore, their tensile and bending behaviour is a subject of great concern. The aim of this work was to perform a test program on 1 × 19 CFRP cables in two different situations: tensile loading and four-point bending loading. Finite element models were developed to simulate both conditions, including frictional contact between the cable wires. A simplified analytical model was also used to predict the cable behaviour in tension. Numerical predictions were compared to experimental data showing relatively good accuracy, unlike the verified analytical model. CFRP cables presented outstanding tensile behaviour, but bending over small radius spools could not reach the performance of steel wire ropes. Furthermore, simulation could only fairly predict bending below strains of μ1,000 μe for the external rods, beyond which the cable presented highly non-linear behaviour that could not be simulated by the numerical model.
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Wang, Xiaogang, Wenwu Fan, Xiangbo Du, and Zhaoxin Fang. "Experimental Study on Structural Degradation of CFRP Strengthened RC Beams Subjected to Weak Interfaces." Open Civil Engineering Journal 10, no. 1 (July 29, 2016): 384–401. http://dx.doi.org/10.2174/1874149501610010384.
Full textAbstract:
The performance of corroded reinforced concrete (RC) beams strengthened with externally bonded carbon fiber reinforced polymer (CFRP) materials may be affected by a weak interface caused either by defective bonding between the new and old concrete in the case of cover replacement or by expansive cracks in the case of direct application. To investigate this effect, thirteen strengthened beam specimens with preinstalled horizontal weak interfaces were designed and tested in monotonic bending. Through analysis of the experimental results, in terms of load deflection curves and the derived bond stress distribution, it was found that intermediate delamination was induced by the weak interfaces, which greatly impaired the integrity of the strengthening system and eventually led to CFRP integral debonding without lateral confinement. Degradation of the shear transfer ability through the interface can be expected due to interfacial weakening, increasing of the CFRP reinforcement ratio and reduction of cover thickness. Crack-induced weak interfaces caused less serious damage at the early stage but induced more dramatic degradation as cracks expanded. U-strip confinement was found to be effective in improving the structural performance of the strengthened beam and preventing CFRP integral debonding. Nevertheless, intermediate delamination cannot be prevented, increasing the risk of CFRP premature rupture and end anchorage failure.
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Duarte, P., J. R. Correia, J. G. Ferreira, F. Nunes, and M. R. T. Arruda. "Experimental and numerical study on the effect of repairing reinforced concrete cracked beams strengthened with carbon fibre reinforced polymer laminates." Canadian Journal of Civil Engineering 41, no. 3 (March 2014): 222–31. http://dx.doi.org/10.1139/cjce-2013-0124.
Full textAbstract:
This paper presents experimental and numerical investigations on the effect of repairing cracks in reinforced concrete (RC) beams prior to strengthening them with carbon fibre reinforced polymer (CFRP) laminates. The experimental campaign comprised flexural tests on three types of full-scale RC beams with T-shaped cross-section: (i) two reference un-strengthened beams, (ii) two CFRP-strengthened beams previously loaded and cracked, and (iii) two CFRP-strengthened beams, previously loaded, cracked and repaired with epoxy resin. The repair and strengthening techniques consisted of respectively injecting the cracks with epoxy resin and applying CFRP laminates according to the externally bonding reinforcement technique. In the numerical study, the structural response of all beams tested was simulated using the finite element software Atena, which features a smeared cracked model constitutive relationship for concrete. A parametric study was carried out in which the influence of material parameters, namely the fracture energy, on the beams structural response was assessed. Experimental results showed that repairing cracks by means of epoxy injection before strengthening them with CFRP laminates provided a considerable increase of stiffness, but only a slight increase of ultimate strength, as failure was triggered by the debonding of the strengthening system at the anchorage zones. In the numerical study a very good agreement with experimental data was obtained. For the repaired and strengthened beams, such agreement was obtained by increasing concrete’s fracture energy when compared to that of the reference beams.
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"Work on the pull-out of anchors based on carbon fibers when arranging external reinforcement systems." Promyshlennoe i Grazhdanskoe Stroitel'stvo, no. 3 (March 2019): 29–34. http://dx.doi.org/10.33622/0869-7019.2019.03.29-34.
Full textAbstract:
Reliable anchoring of carbon reinforcement elements into the body of the structure is one of the most important aspects when designing the strengthening of reinforced concrete structures with the system of external reinforcement based on composite materials. The use of carbon fiber anchoring elements in this case is confirmed by numerous tests, but there are no methodological provisions for the calculation and design of these anchors at the moment. Special experimental studies of the parameters of anchors and their effect on the bearing capacity of the anchorage have been conducted for this purpose. The tests were carried out in two stages, during the experiments the breaking load, the size of the concrete pull-out cone, as well as the nature of the destruction of the anchor were recorded. In addition, the length of the anchorage in the concrete body, the pull-out forces, the maximum deformations of the anchor and the length of the anchorage when introducing the anchor fibers in the external reinforcement system have been defined. According to the results of the experiments, the analysis of the results, in particular, various schemes of destruction of anchors and the impact of the depth of the anchor on them, its diameter, as well as the type of binders was carried out.