Anchorage System Research Articles

Performance of Prestressed Anchor Cables Supporting Deep Foundation Pit of a Subway Station during Spring Thaw

Based on the deep foundation pit for a subway station in Changchun (China), a 3D numerical model of water–heat coupling in a prestressed pile anchor system was established to determine its performance in freezing and thawing seasons in alpine areas. Its reliability was confirmed using field monitoring data on the prestressed anchor cables, which demonstrated changes in surface subsidence, anchor cable axial force, and pile horizontal displacement during spring thaw. The results demonstrated different degrees of elevation of the ground surface at the beginning of the spring thaw depending on whether the ground surface was at 2, 5, or 8 m from the pit excavation surface. Moreover, they demonstrated the occurrence of melting and surface subsidence when the temperature rises above 0°C, and that the axial force of the anchor cables fluctuates at the beginning of spring thaw but stabilizes in its middle and late stages. The phenomenon of pile horizontal displacement during the spring thaw could be roughly divided into three stages, with the second stage resulting in the most significant displacement. These results can provide certain reference for deep foundation pit projects in alpine areas.

In Situ Concrete Bridge Strengthening Using Ductile Activated NSMR CFRP System

Novel and complex structural solutions are often challenging to introduce in the building industry since they may provide unconventional and less verified behavior combined with several novel and unique failure modes. A desired safety level may be difficult to verify due to the lack of knowledge related to failure modes and their variation. This study introduces a method that may provide a first step toward addressing such challenges. Five laboratory tests were done on a novel ductile response-controlled anchor system used for prestressed CFRP NSMR strengthening. These results were used as a basis for further implementation in a pilot project where an in situ cast concrete bridge was strengthened with the developed system. A particular focus was dedicated to the capability of the designed system response to provide a consistent load/deformation curve, yielding threshold, and yielding regime. The novel system enabled response tailoring to the specific pilot project. Installation and prestressing procedure worked as desired, where losses in the fully prestressed system, after three weeks, were approximately 0.2 to 1.6 kN (0.2–1.3 mm). In situ proof loading of all strengthening systems (20 anchor systems) was done to eliminate any possible failure modes below the proof-loading level. It was performed with no signs of distress.

Cast-in and post-installed rebar anchorage systems in RC column foundation joints: System specific assessment and design

For assessment and design of post installed reinforcing bar (rebar) anchorages in reinforced concrete (RC) construction, two different approaches (i) conventional RC approach and (ii) fastening technology approach, coexist. For high strength adhesive systems, it is likely that the design anchorage lengths obtained using the fastening technology approach are significantly smaller in comparison to that obtained using the conventional RC approach. The main reason for this gap between the two approaches is, that while conventional RC approach considers qualified post installed (PI) systems as equivalent to cast in straight systems (CIS), PI systems are considered to be system specific in fastening technology. The system specific consideration of PI rebar anchorages in fastening technology makes it possible to take advantage of the higher bond strengths of the innovative adhesive systems, which is not possible in conventional RC design.This paper considers a comparison of the available approaches for assessment of rebar end anchorages in RC column foundation joints (CFJ). To this end, the benchmark test data generated by the authors [1] is used for the comparative discussions in the background of possible modes of failure. To include system specific definition of bond resistance in conventional RC approach, the potential of the system specific bond model in fastening technology to replace the general bond model in conventional RC practice for rebar anchorages is discussed. The alternate possibility of evolving the existing bond model in RC practice for including system specific consideration is also discussed. It is observed that the system specific definition of bond resistance within the framework of RC design practice is more suitable for rebar end anchorages. A proposal for failure hierarchy based assessment approach employing this system specific definition is made in this paper. The proposed approach is successfully validated to demonstrate its capability to assess both the failure loads and failure modes in a realistic manner, irrespective of the type of anchorage (cast in or post installed). The proposed approach is in concurrence with RC design practice and at the same time does not conflict with fastening technology. The presented is thus, a comprehensive breakthrough towards harmonizing the coexisting design concepts for rebar end anchorages.

Orthodontic miniscrew supported correction of partially impacted mandibular 2nd molar- A case report

A wide range of clinical procedures have been introduced and practiced to correct mesially inclined mandibular molars which is a common situation among young adults, occurring usually due to inadequate space in the arch for its eruption. There are two major treatment options available for the correction of impacted / partially impacted molars and this depends on several factors. The objective was to treat a 15-year-old male patient having a lower right partially impacted 2nd molar using skeletal anchorage system. The lower right 3 molar was surgically excised, and the partially impacted 2 molar was uprighted using an orthodontic miniscrew which was placed between lower right 1 and 2 premolars on the mesial side. The use of skeletal anchorage system has an excellent advantage over conventional methods since there is prevention of unwanted movement of anchor teeth leading to successful correction without any delay in the treatment duration.

Efficiency of innovative strengthening techniques and anchorage systems using different materials on flexure performance of R.C beams

This research offers an experimental program that investigates the flexural performance of strengthened reinforced concrete (RC) beams using various techniques. To delay the onset de-bonding of the strengthening system, the novel anchorage system is proposed and examined. Innovative Externally Bonded in Groove technique (EBIG) was introduced to protect the FRP strips from exposure to vandalism, damage, and temperature. Ten half-scale RC beams were cast, a reference beam in addition to nine RC strengthened beams. Strengthened beams were fortified utilizing either Near Surface Mounted (NSM) system or Externally reinforced Bonded (EB) technique using glass fiber at the bottom face of the strengthened beams, whereas one of those beams was strengthened by Externally Bonded in Groove (EBIG). Five test parameters were considered in this research; the strengthening technique used, type of NSM bars, amount of steel bars used, proposed end anchors of steel bars, and the wrapping configurations. The results included the capacity, first cracking load, deflection at different loading levels, cracking pattern, and mode of failure. The stiffness and ductility of strengthened beams were offered and compared. In comparison to the control beam, the strengthened beams with different systems displayed a gain in capacity that ranged from 42% to 105%. Additionally, results demonstrated the superiority of the NSM as a strengthening technique over any other technique, especially the NSM-steel bar which had an innovative end anchorage. An analytical study was applied using the ACI 440.2R-17 design guidelines to compare with the experimental results, the analytical results showed a good prediction. As well, nonlinear finite element models of the tested beams were created using the ANSYS-V22 to validate the structural behavior of those beams according to their capacities, fracture patterns, and deflection characteristics. A good accord between numerical and experimental results was achieved.

Experimental Study on the Flexural Behavior of Large-Scale Reinforced Concrete Beams Strengthened with Prestressed CFRP Plates

Carbon fiber–reinforced polymer (CFRP) systems have been widely used to strengthen concrete structures. To further study the flexural strengthening of concrete beams with prestressed CFRP plates, flexural tests of large-scale reinforced concrete beams were performed, and a tensioning and anchorage system suitable for engineering applications was used in this study. The effects of the prestressing level, strengthening amount, type, and bonding position of the prestressed CFRP plate on the flexural behavior were investigated. The test results showed that the cracking load, yielding load, and ultimate load of all prestressed strengthened beams could reach 2.25–3.38 times, 1.27–1.53 times, and 1.24–1.61 times those of the unstrengthened beam, respectively. The postcracking stiffness, cracking load, and yielding load could be increased by increasing the prestressing level and strengthening the amount of the prestressed CFRP plate. However, a high prestressing level of 50% could lead to a premature intermediate debonding of the CFRP plate before yielding of the steel reinforcements and a reduction in the ultimate load. The use of a low-strength prestressed CFRP plate could achieve a strengthening efficacy similar to that of a high-strength CFRP plate before yielding of the steel reinforcements, whereas the low-strength CFRP plate reduced the ultimate load by 25 kN compared with the high-strength one. The prestressed CFRP plate bonded on the two sides provided a lower flexural strengthening efficacy than that bonded on the bottom of the beam owing to the shorter force arm and the nonuniform stress of the side-bonded CFRP plate.

Recent protocol of the sendai surgery-first (SSF) approach: Clinical and scientific perspectives

The treatment protocol of Surgery-First has gradually evolved, since our team employed it for the first time twenty-years ago. In this article, we describe every step of the current Sendai Surgery-First (SSF) approach protocol, in detail. Two major differences between the recent and old protocol, exists, which are (1) In the recent protocol, placement of brackets and passive surgical wires is no longer required before jaw surgery, and (2) only surgical hooks are needed to be bonded to the lateral teeth. Further, the duration of surgical splint use has been significantly shortened. Instead of a surgical splint, a posterior build-up in the maxillary dentition is used to secure a vertical stop. These considerations allow patients to undergo treatment in a more comfortable manner. However, the skeletal anchorage system (SAS) using the orthodontic miniplate for postoperative orthodontics remains unchanged. Based on many SSF approach cases, we have confirmed that the SAS can predictably improve unstable and complicated occlusion immediately after surgery, and reliably achieve treatment goals. Therefore, our SSF approach has the distinguishing feature of having a wider range of indications than other Surgery-First approaches. Furthermore, in regard to scientific perspectives, dynamic systemic changes in bone metabolic activity of the SSF approach is also discussed. The C-reactive protein levels increase immediately after surgery, followed by an increase in the C-terminal telopeptide type I collagen levels, which is associated with osteoclastic activity, indicating bone resorption. After this, alkaline phosphatase, and bone-specific alkaline phosphatase levels, which are associated with osteoblastic activity, increase with a peak at 1 month and then decrease gradually to preoperative levels by 6 months. During the early postoperative period, osteocalcin-positive cells, such as osteogenic precursors, appear in the peripheral blood and are involved in the bone healing process after surgery through the systemic acceleration phenomenon. Therefore, orthognathic surgery induces regional and systemic accelerated phenomena, which, in turn, causes rapid orthodontic tooth movement, resulting in reduced treatment duration with the SSF approach.

A novel laparoscopic surgical robot (LSR) based on double-leg ultrasonic motor (DUM)

Magnetic anchor and guidance system has been widely used in laparoendoscopic single-site surgery with the benefit of small wound, wide field of vision (FoV), and convenience for repeated positioning. This paper introduces a novel three DoF laparoscopic surgical robot (LSR) based on double-leg ultrasonic motor (DUM) which features small dimension, fast response, and high positional precision. Piezoelectric ceramic (PZT) plates can excite longitudinal and bending coupled vibration of DUM and the two phase in-plane three order bending vibration can form traveling wave to drive DUM rotor. DUM stator is optimized by non-dominated sorting genetic algorithm-II for good consistency of two working mode frequencies and negligible influence of adjacent interference modes on working modes, which improves motion stability and driving efficiency. The mechanical characteristic of DUM under different chamfer parameters has been studied through comparative experiments and the design of robot prototype is completed further. For clockwise and counterclockwise rotation, the maximum no-load rotary speeds are 333.75 and 335.77 rpm, and the maximum output torques are 2 and 1.6 N mm. The experimental platform for FoV measurement is built to verify that LSR can adjust the posture to obtain suitable surgical FoV, indicating that the application of DUM in LSR has significant advantages and great potential.

Nasal Septum Changes in Adolescents Treated with Tooth-Borne and Bone-Borne Rapid Maxillary Expansion: A CBCT Retrospective Study Using Skeletal Tortuosity Ratio and Deviation Analysis.

Using three-dimensional (3D) images, this study evaluated the impact of Rapid Maxillary Expansion (RME) on changes in Nasal Septal Deviation (NSD). Cone-beam computed tomography (CBCT) scan of 40 children with transverse maxillary deficiency, who received tooth-borne (TB) RME or bone-borne (BB) RME, were included in this investigation. Two CBCT scans were performed: one before to appliance installation (T0) and one after a 6-month retention period (T1). The analysis was performed by dividing the actual length of the septum by the desired length in the mid-sagittal plane to measure NSD based on the tortuosity ratio (TR). Subjects in the TB group showed a statistically significant reduction (p < 0.05) of the TR value from T0 to T1, according to the paired Student t test. Subjects in the BB group showed similar findings, with a statistically significant reduction (p < 0.05) of the TR value from T0. No statistically significant differences were found between the mean changes of TR between TB group and BB group. RME may have some effects in reducing the degree of NSD; however, no differences were found between RME performed with TB and BB anchorage systems.

Reinforced concrete beams externally strengthened by CFRP rods with steel plate, anchorage bolts, and concrete jacketing

This study proposed a new scheme for the retrofitting of Reinforced Concrete (RC) beams using Carbon Fiber Reinforced (CFRP) rods restrained using steel plates and anchorage bolts called the mechanical anchorage system (MAS). This system also employed an external concrete jacket to cover the MAS and CFRP rods. The performance of the proposed technique was experimentally assessed using the four-point flexural testing of retrofitted beams under incremental cyclic load using a dynamic actuator. A total of eight beams were cast and tested in different configurations to determine the effectiveness of the design parameters including the number of CFRP rods, the contribution of MAS, and concrete jacketing (CJ) in terms of load capacity, cracking, failure mode, and ductility. The results revealed that the efficiency of the proposed retrofitting system was achieved by increasing the load capacity of retrofitted beams and preventing the premature debonding failure of CFRP rods. Although de-bonding can occur on the surface between the old and new concrete, the utilization of a perfect adhesive epoxy on the concrete contact surface led to sufficient bonding between the two surfaces. Therefore, overall, the proposed strengthening technique can be considered a reliable method to enhance the performance of RC beams without the risk of de-bonding.

Mortar cure-dependent effects on adhesive anchor systems loaded in tension

This paper presents a large experimental campaign and the corresponding analysis quantifying mortar curing effects on the pull-out performance of bonded anchor systems. Standard confined pull-out tests were performed on two commonly used adhesive anchor systems. The two investigated bonded anchor systems were based on different materials, where the mortar of the first bonded anchor system (BAS-VE) was a vinyl-ester based product and the second bonded anchor system (BAS-EP) contained an epoxy-based mortar. In order to isolate the mortar curing effects on the anchor performance, a mature concrete was used as base material minimizing well-known aging and curing effects related to the substrate, concrete. In total, 93 pull-out tests were performed for various curing times in order to characterize influences on bond strength, stiffness, and peak displacement. Depending on the product specifications and corresponding approval documents, tests were carried out in a time-range of a few minutes up to three months after the anchor installations. Measured temperature (and humidity histories) of the environment have been utilized for predicting the mortars’ degree of cure for each structural anchor test. The results show a cure-dependent behavior in BAS-VE and BAS-EP. Although the bond strength fails to increase significantly after reaching the manufacturer approved minimum curing time, the stiffness shows an increase for longer cured anchors.

Modern Anchorage Systems in Orthodontics.

Anchorage has been a vital topic since the origin of orthodontics. In the orthodontic process, gentle, constant pressure is applied to the teeth that need to be moved against the other teeth, which serve as the anchoring unit. The anchoring teeth must be completely stable. The introduction of temporary anchorage devices to the orthodontic field hasmade it possible to overcome conventional anchorage and its limitations. Mini implants have widened the horizon of the orthodontic field. Skeletal anchorage has, to a large degree, replaced conventional anchorage in a situation where anchorage is considered either critical, insufficient, or likely to result in undesirable side effects such as vertical displacements generated by intermaxillary force systems. Over the last few years, anchorage control with mini-implants has acquired plenty of significance in the clinical management of orthodontic patients. The mode of anchorage facilitated by these implant systems has a unique characteristic owing to their temporary use, which results in a transient, albeit absolute anchorage. The foregoing properties, together with the recently achieved simple application of these screws, have increased their popularity, establishing them as a necessary treatment option in complex cases that would have otherwise been impossible to treat. This comprehensive review aimsto present and discuss the historical view, clinical uses, benefits, and drawbacks of the mini-screw implants used to obtain a temporary anchorage for orthodontic applications. Topics to be discussed include classification, types and properties, types of screw, head, and thread, their clinical applications, sites, and placement method selection.

Design and Haemodynamic Analysis of a Novel Anchoring System for Central Venous Pressure Measurement.

In recent years, treatment of heart failure patients has proved to benefit from implantation of pressure sensors in the pulmonary artery (PA). While longitudinal measurement of PA pressure profoundly improves a clinician's ability to manage HF, the full potential of central venous pressure as a clinical tool has yet to be unlocked. Central venous pressure serves as a surrogate for the right atrial pressure, and thus could potentially predict a wider range of heart failure conditions. However, it is unclear if current sensor anchoring methods, designed for the PA, are suitable to hold pressure sensors safely in the inferior vena cava. The purpose of this study was to design an anchoring system for accurate apposition in inferior vena cava and evaluate whether it is a potential site for central venous pressure measurement. A location inferior to the renal veins was selected as an optimal site based on a CT scan analysis. Three anchor designs, a 10-strut anchor, and 5-struts with and without loops, were tested on a custom-made silicone bench model of Vena Cava targeting the infra-renal vena cava. The model was connected to a pulsatile pump system and a heated water bath that constituted an in-vitro simulation unit. Delivery of the inferior vena cava implant was accomplished using a preloaded introducer and a dilator as a push rod to deploy the device at the target area. The anchors were subjected to manual compression tests to evaluate their stability against dislodgement. Computational Fluid Dynamics (CFD) analysis was completed to characterize blood flow in the anchor's environment using pressure-based transient solver. Any potential recirculation zones or disturbances in the blood flow caused by the struts were identified. We demonstrated successful anchorage and deployment of the 10-strut anchor in the Vena Cava bench model. The 10-strut anchor remained stable during several compression attempts as compared with the other two 5-strut anchor designs. The 10-strut design provided the maximum number of contact points with the vessel in a circular layout and was less susceptible to movement or dislodgement during compression tests. Furthermore, the CFD simulation provided haemodynamic analysis of the optimum 10-strut anchor design. This study successfully demonstrated the design and deployment of an inferior vena cava anchoring system in a bench test model. The 10-strut anchor is an optimal design as compared with the two other 5-strut designs; however, substantial in-vivo experiments are required to validate the safety and accuracy of such implants. The CFD simulation enabled better understanding of the haemodynamic parameters and any disturbances in the blood flow due to the presence of the anchor. The ability to place a sensor technology in the vena cava could provide a simple and minimally invasive approach for heart failure patients.

Effect of prestressed anchorage system on mechanical behavior of squeezed soft rock in large-deformation tunnel

Active support with the prestressed anchorage system as the core can improve the physical and mechanical properties of a squeezed large-deformation tunnel by increasing the confining pressure of the surrounding rock in time, which has a positive effect on the tunnel excavation and displacement control. In this study, triaxial tests were conducted to investigate the properties of carbonaceous-slate samples obtained from the typical large-deformation section of Muzhailing highway tunnel. The results indicated that the rock samples’ elastic modulus E and cohesion c increased with the confining pressure within a certain range. Considering the realization of the above rules of E and c, the secondary development of the FLAC3D built-in strain-softening model was achieved to establish a soft-rock constitutive model considering the changes in the surrounding rock parameters with respect to the confining pressure. After validating the proposed constitutive model, the effects of the prestressed anchorage system with different parameters on the mechanical behaviors of squeezed soft rock in Muzhailing tunnel were studied via numerical simulations, and the results indicated that with the increases in the prestress, anchor-cable length, and density, the displacement of the surrounding rock decreased and the disturbance ranges of E and c narrowed, with a slowing trend. In addition, the combination form of short and long anchor cables also affected the displacement of the surrounding rock. After comparing the effects on the displacement control and the parameters improvement of surrounding rock, the key parameters of prestressed anchorage system applied in Muzhailing highway tunnel were determined. Subsequently, the proposed prestressed birdcage cable system with the suggested parameters were applied in the typical large-deformation section of Muzhailing highway tunnel. Monitoring data indicated that the maximum displacement of the tunnel section decreased from 529 mm under passive support to 229 mm under active support, confirming that the prestressed birdcage cable system had a good displacement-control effect. This study could help popularize the prestressed anchorage system in tunnelling engineering and provide guidance for the design of key parameters when combating large-deformation disasters in squeezed soft rock highway tunnels with a high geo-stress.

Enhancement of the bond behaviour between sand coated GFRP bar and normal concrete using innovative composite anchor heads

Anchor heads could efficiently address the bond weakness between Fibre-Reinforced Polymer bars and concrete. This experimental study enhanced the bond behaviour between GFRP bars and concrete using three innovative anchorage systems made from glass fibre cloth and epoxy resin. A direct pullout test was used to study the bond-slip performance between the bar and the concrete. Test variables were GFRP bar diameter (3 diameters), concrete compressive strength (20.4 and 40.2 MPa), and anchor system (three different types). Based on the test results, in low-strength concrete (i.e. 20.4 MPa) samples, the anchor system efficiency was not promising, and the failure occurred between the concrete and anchors. However, for higher strength concrete (i.e. 40.2 MPa) samples, the ultimate developed tensile load increased between 14 and 68% for different bar sizes and anchorage systems compared to the unanchored control specimens.

A case study on the feasibility of using static-cast fibre-reinforced concrete electric poles fully reinforced with glass fibre reinforced polymer bars and stirrups

This study experimentally investigates the structural performance of full-scale reinforced concrete utility poles fully reinforced with glass fibre reinforced polymer (GFRP) bars. The weak bond strength between GFRP bars and concrete in full-scale structures has been addressed by using an innovative anchorage system. Furthermore, fibre-reinforced concrete (FRC) was successfully used to enhance the crack propagations of GFRP-reinforced concrete poles. Three poles were constructed from FRC, while one was constructed with normal concrete (NC) as a benchmark. Polypropylene (PP) and crimped polyolefin-based macro-synthetic (CPO) fibres were used. An innovative anchorage system was used to increase the bond strength between longitudinal bars and the concrete. Crack initiation and pattern, load-carrying capacity and vertical deflections of GFRP reinforced FRC poles were obtained and compared with their normal concrete counterparts. According to the results, the PP-FRC pole showed better crack propagation performance, while the CPO-FRC showed higher stiffness than the normal concrete poles. In addition, regardless of the concrete type, the permanent deformation of all GFRP reinforced concrete poles after different stages of loading were significantly smaller than those of typical steel reinforced concrete poles.

Effectiveness of Fan Anchors in Preventing Debonding in FRP-Strengthened Steel Members

Fibre Reinforced Polymers (FRPs) are extensively employed to strengthen existing structures because of their several advantages over other strengthening techniques. On the other hand, the premature debonding of FRP reduces its effectiveness in strengthening steel structures. Anchoring FRP composites is an effective solution to delay or even prevent their debonding. Very limited anchorage methods, however, have been introduced for FRP-strengthened steel structures and the need for an effective anchorage system remains. Fan anchor has been validated as one of the remedies against debonding failure in FRP-strengthened concrete structures. Considering the advantages that fan anchors offer, the use of fan anchors for FRP-strengthened steel structures is proposed and evaluated in this paper. Since FRP-steel joints have a different bond-slip law than FRP-concrete joints and the strengthened steel members are prone to buckling-debonding interactions, this study focuses on the efficiency of fan anchors in delaying FRP debonding by assuming that an adequate mechanical connection between the dowel and the steel substrate is provided. Three experimental studies involving shear, flexural and buckling strengthening of steel components were simulated through finite element modelling, and fan anchors were added to the models after validation. The effect of fan anchors on strength, failure mode and FRP's strain distribution of the models was examined. The study showed that the fan anchor was successfully able to delay debonding mode, which increased the strength and ductility and exploited a higher strain capacity of FRP plates.

An innovative frictional anchorage system for flat CFRP ribbon strips

Unidirectional carbon fibre-reinforced polymer (CFRP) materials represent a promising alternative to steel because of their lightweight, high tensile strength, and excellent corrosion and fatigue resistance. Stress-ribbon structural systems define the potential application object of unidirectional flat CFRP strips. However, anchorage difficulties make this idea problematic—the typical gripping systems are inefficient for anchoring the CFRP ribbons because of the tremendous thrust forces-induced stress concentration. Thus, the innovative frictional spiral anchorage system of the flat CFRP strips is the object of this study, which formulates the design principles for the frictional joins. Furthermore, the proposed theoretical model minimises the gripping system size, satisfying the CFRP strength limitation when the developed modified Archimedean spiral determines the shape of the contact surface. This work experimentally demonstrates the theoretical concept’s adequacy—the mechanical resistance prediction error does not exceed 7% in the loading range covering the service load conditions. In addition, the manuscript presents several examples of frictional gripping systems, including the stress-ribbon pedestrian bridge prototype, and provides further insights into the frictional anchorage systems.

Research on the reasonable anchorage length and failure characteristics of resin anchorage system

In order to better analyze the pullout failure characteristics of the resin anchorage system and determine the reasonable anchorage length, the mixed particle contact model based on the Parallel Bond model has been creatively proposed in particle flow code. Then, the model has been used to establish the pullout model under different surrounding rock conditions and different anchorage lengths, the maximum bearing capacity, the final failure characteristics, interaction mechanism of the anchorage system have been analyzed by pullout experiments, and the reasonable anchorage length is further analyzed based on the critical anchorage length and the impact of anchorage system failure on surrounding rock. The results show that: (1) The improved mixed particle contact model can better characterize the strength characteristics of surrounding rock, and reproduce the failure phenomenon of anchorage system under pullout load; (2) Under different surrounding rock conditions, the damage degrees of the anchorage systems when theyreaches their maximum bearing capacity are different, and the damage of the anchorage system in weak rock often means that the rock around the anchorage agent is damaged in a large range.The way of lengthening the anchorage length (The anchorage length exceeds the critical anchorage length) should be adopted in the weak rock environment; (3)In this paper, the corresponding reasonable anchorage lengths under the conditions of strong rock, sub- strong rock and weak rock are 22 cm, 32 cm and 137.8 cm respectively.

Developing a hybrid FRP-concrete composite beam

Current materials engineering trends put forward the development of efficient structural solutions. The steel replacement with fiber-reinforced polymers (FRP) exemplifies the key to the corrosion problem. However, the relatively low deformation modulus of typical FRP materials raises the deformations of the structural components. Together with the self-weight reduction increasing the kinematic displacements, the latter issue makes developing hybrid structures comprising compression-resistant concrete and high-performance in tension FRP profiles important. Although such hybrid systems are applicable for bridge engineering, the uncertainty of the inter-component bonding properties complicates developing these innovative structures, including the design models. The typical solution focuses on the local bond improvement, e.g., employing FRP profile perforation and mechanical anchorage systems. However, this study introduces an alternative solution, using the stress-ribbon bridge structural system for creating the hybrid beam prototype, which combines the synthetic fiber-reinforced concrete slab and pultruded FRP profile fixed on the supports. This work exemplifies the structural development concept when the finite element (FE) modeling outcome defines the target reference of the design procedure. Thus, on the one hand, this innovative structure simplifies the corresponding numerical (FE) model, which assumes the perfect bond between the components of the hybrid beam system. On the other hand, the solution to the support problem (resulting from a low resistance of pultruded FRP profiles to transverse loads) improves the structural performance of the bridge prototype, doubling the structure’s flexural stiffness and load-bearing capacity regarding the weak concrete supports’ system. The bending tests proved the adequacy of this solution in describing the design reference for further development of the proposed structural concept.