Bar Anchorage Research Articles

Development of A New Model on PC Segmental Retaining Wall Using Solid Bar Anchors and Fin Fish

The development of transportation infrastructure is very important for economic growth. In the context of the construction of precast concrete (PC) segmental retaining walls, the use of innovative technologies such as solid bar anchors and fish fins is the main focus of improving the efficiency and reliability of the structure. This research aims to develop a new model that optimizes the use of solid bar anchors and fin fish in PC segmental retaining walls, with the hope of improving structural performance and extending the service life of the wall. The research methodology includes literature studies, development of mathematical models based on soil mechanics and finite element theory, and numerical simulations using PLAXIS software. The results show that the MSE Wall system with solid bar anchors and fin fish meets the SNI Geotechnical No. 8460 standard of 2017, with safety factors of high bolling, shear, and ground carrying stability. The use of a crossbar necklace configuration with a center to center (ctc) distance of 30 cm provides greater tensile strength than a ctc of 50 cm. This research is expected to make a significant contribution to the development of construction technology that is more efficient, economical, and sustainable.

Experimental investigation on the tension lap splices used in the joints of precast RC foundation piles

AbstractThe joints between precast reinforced concrete pile segments in deep foundations are typically mechanically lockable. They include anchor bars embedded inside the ends of each segment, forming lap splices with the main bars. Because of their particular technology, these lap splices are somewhat different from traditional lap splices, as shown in the first part of this paper, where the impact of their specific characteristics on the tensile behavior of the joints is discussed. The experimental section presents the results of 19 tensile tests on these lap splices and compares them with established theoretical models. The roles of various parameters (lap length, type and amount of confining reinforcement, type of anchor bars, and concrete cover thickness) are investigated. One of the major findings indicates a significantly lower lap capacity when using plain‐bar spirals compared to closed‐ribbed stirrups. Additionally, at low stress levels, the models tend to be unconservative. Building on this insight, a modified model is proposed for lap splices provided with plain‐bar spirals.

Study on the Nodal Composite Bearing Performance of Nontruncated PHC Pipe Pile and Bearing Platform.

In this paper, low circumferential reciprocating load foot-scale tests were performed on two nontruncated PHC B 600 130 tubular piles with bearing nodes to characterize the damage process and morphology of the specimens and to investigate the load-carrying performance of the members. The test results reveal that under the action of tensile-bending-shear loading, the bearing concrete in the node area buckles and is damaged, the anchored reinforcement in the node area yields, the constraint is weakened, an articulation point is formed, and the node rotational capacity increases. When the embedment depth increases from 200 mm to 300 mm, the ultimate bearing capacities of the positive and negative nodes increase by 31.04% and 36.16%, respectively. A numerical simulation is used to verify the test results. Considering the four types of piles without truncated nodes, the numerical simulation is used to analyze the node-bearing capacity at different embedment depths. Finally, a preferred node type is proposed as follows: a terminal plate welded anchor bar and pipe pile core-filled longitudinal reinforcement anchored into the bearing node, with a preferred embedment depth of 250 mm.

Numerical analysis of the effect of bar anchorage length on bond behavior in pull-out test

This paper presents a numerical simulations of a pull-out test conducted using ABAQUS software. The purpose of the simulations was to evaluate the effect of anchorage length on the bond behavior of ribbed bars in this test, based on the experiments performed. The interaction at the bar-concrete interface was modeled using a contact cohesive surface and calibrated bond-slip curves obtained from experiments. Material models were defined using mechanical parameters obtained from in-house tests on concrete and steel. The analysis shows that the bond behavior is significantly influenced by the anchorage length. Numerical simulation results demonstrate excellent convergence with laboratory tests, both in terms of the bond-slip curve and material behavior

Impact of Confinement on Bar Anchorage in Relocated Plastic Hinges

Impact of Confinement on Bar Anchorage in Relocated Plastic Hinges

Experimental analysis of the effect of bar anchorage length on bond behavior in pull-out test

The article presents bond tests performed using the pull-out method. The experiments were designed to evaluate the effect of anchorage length on the bond in this test. The analysis shows that the length of the bar-concrete interface significantly influences the bond behavior. It determines the type of bond failure, affects the distribution and value of stresses in the bar, and projects the bond-slip curve, which is a key result of the pull-out test

Study on Mechanical Response Characteristics of Anchor under Dynamic Disturbance

The roadway surrounding rock is often subjected to severe damage under dynamic loading at greater mining depths. To study the dynamic response of prestressed anchors, the damage characteristics of anchor solids with different prestresses and number of impacts under dynamic and static loads were investigated by improving the Hopkinson bar equipment. The effect of prestress on stress wave transmission was obtained, and the laws and reasons for axial force loss under static and dynamic loads were analyzed. The damage characteristics of anchor solids were determined experimentally. The results show that with an increase in prestress from 15 to 30 MPa, the peak value of the stress wave gradually increases and the decay rate gradually decreases. Shear damage occurred at the impact end of the specimen, combined tension and shear damage occurred at the free end, and fracture occurred in the middle. With an increase in the number of impacts, the damage to the anchor solid specimens gradually increased, and the prestressing force gradually decreased. After impact, the axial force of the various prestressed anchor solid specimens gradually increased; however, the anchor bar with a 17 MPa prestressing force had the slowest rate of axial force loss during impact, withstanding a greater number of impacts. In on-site applications, after three explosions, the displacement on both sides of the tunnel supported by 17 MPa prestressed anchor rods could be controlled within 0.3 m, with an average displacement of 206, 240, and 283 mm, respectively, increasing by 16.5% and 17.9%. This study, based on theoretical analysis and laboratory research combined with field application provides guidance for the anchor support of a dynamic loading tunnel.

Investigation on the dynamic characteristics of anchor rods considering size effect and pull-out loads based on IIR-FDM

When the surrounding rock of tunnel anchor bars has boundaries, the signals obtained from non-destructive testing (NDT) of anchor rods will be simultaneously affected by size effects and pull-out loads, leading to potential misinterpretation of the test results. In order to accurately assess the anchorage quality of anchor rods under this interference, NDT and numerical simulations of anchor rods subjected to different anchorage quality were conducted under the influence of size effects and pull-out loads. A signal filtering method, which combines the infinite impulse response-finite difference method, was proposed for identify the impact of size effects. The study analyzed the variations in wave velocity and fundamental frequency of anchor rods with anchorage defects and intact anchor rods under the influence of size effects and pull-out loads. The results indicate that the IIR-FDM method, in comparison to the traditional wavelet method, provides better agreement between the calculated wave velocities and existing findings. With the increase of size effect, the wave velocity and amplitude ratio of the anchor rods decrease, and the fundamental frequency increases first and then decreases. As the working load on the anchor rods increases, the wave velocity initially decreases, then rises, while the fundamental frequency initially increases and then experiences a slight decrease. The presence of anchorage defect results in an increase in the wave velocity and amplitude ratio of the anchor rods, while causing a decrease in the fundamental frequency. This effect of defects on wave velocity and fundamental frequency is more pronounced at lower loads. The wave velocity after IIR-FDM processing has a small error with the simulated wave velocity, indicating the reliability of the processing method.

Field test of GFRP bar anti-floating anchor slurry-rock interface bonding performance

Based on fiber Bragg grating (FBG) sensing and monitoring technology, the slurry-rock interface bonding characteristics of glass fiber reinforced polymer (GFRP) anti-floating anchor and steel anti-floating anchor were investigated through the field pull-out destructive test of GFRP bars and steel anti-floating anchor. The differences in slurry-rock interface bonding properties between GFRP anti-floating anchor and steel anti-floating anchor were defined. In addition, the distribution law of shear stress and axial stress at the slurry-rock interface of the GFRP anti-floating anchor was revealed along the anchoring depth. The results showed that the axial stress at the slurry-rock interface of the GFRP anti-floating anchor is maximum at the hole opening and decreases as depth increases. The axial stress reduces to zero at the anchorage depth of about 2.4 m. The shear stress at the slurry-rock interface increases and then decreases. The slurry-rock interface bonding curve of the GFRP anti-floating anchor is approximately a straight line, while the slurry-rock interface bonding curve of the steel anti-floating anchor is a broken line with an obvious inflection point. Comparing different materials and types of anti-floating anchors indicate that the bond performance of steel anti-floating anchors is slightly higher than that of GFRP anti-floating anchors, and the bond strength of anti-floating anchors’ slurry-rock interface improves with the increase of anchor bar diameter. The synergistic effect among anchor bars, grout, and rock mass of the GFRP anti-floating anchor exceeds that of the steel anti-floating anchor. Using the finite element software ABAQUS to GFRP anti-floating anchor rod on rock interface bonding performance simulation, the simulation results was coincident with the test result.

Analysis of transverse constraint force mechanics of anchor rods based on higher order theory

Abstract Research on the mechanical properties of transverse constraint force of anchor support under different loads can help to improve work safety. In this paper, based on the higher-order shear deformation theory, the higher-order whole-local theory of anchor rods is established with full consideration of the transverse normal strain. The geometric and physical equations in the intrinsic relationship are given for the wet thermodynamic behavior of anchor rods’ transverse restraining force. The equilibrium equations of the whole-local are constructed by combining them with the principle of virtual displacement. The analytical solution of the anchor core material was calculated by applying Navier’s method. The boundary displacement conditions of the anchor core material were solved. The anchor core material was modeled by combining it with ABAQUS finite element software. The mechanical analysis was carried out from the two perspectives of the buckling problem under thermal load and the parameter change of the transverse restraining force, respectively. It was found that when the thickness of the anchor bar increased from 20 mm to 50 mm, the radial displacement of the upper layer decreased by 52.95%, and there was no significant change in the positive stress at the upper and lower interfaces. The peak value of the upper interface shear stress decreases significantly from 0.55MPa to −1.41MPa when the anchor laying method is changed from a single layer to four layers. The combination of higher-order theory with ABAQUS software can effectively analyze the change of transverse constraint force of the anchor support, which can help improve its safety.

Effectiveness of FRP bar anchors for prestressed concrete members

Prestressed concrete members are widely used around the world to realize different types of structure, including bridges and skyscrapers. Steel strands are generally employed to apply a compression force into the concrete. Recently, fiber-reinforced polymer (FRP) composite bars have been considered for replacing traditional steel strands in specific applications. The main advantage of FRP bars is their resistance to corrosion. Furthermore, they may have a higher tensile strength-to-weight ratio and fatigue resistance compared to steel strands. Although using prestressed FRP bars may entail for advantages over traditional steel solutions, the anchorage system is an open issue for this technology. Indeed, the anchorage should guarantee a high level of tensile stress into the bar and, at the same time, avoid local failures.In this paper, the preliminary results of an experimental campaign comprising tensile tests of glass and carbon FRP bars with different anchors are provided and discussed. The experimental campaign was aimed at investigating the effectiveness of newly developed wedges in properly anchoring the composite bars. Tensile test results and modes of failure are discussed, shedding light on the main parameters that affect the mechanical behavior of the bars considered.

Experimental hysteretic behavior of CFST column-foundation connections with novel detailing in embedded region

This paper presents a novel CFST column-foundation connection detail to improve stress transfer and damage control. To achieve this aim, seven specimens were created in the lab in three different configurations: exposed connection (base plate), embedded connection without reinforcement, and embedded connection with reinforcement. These specimens were subjected to cyclic lateral load and constant axial load tests. The effect of using internal reinforcement (including reinforcing anchor bar and internal tube) and external reinforcement (including shear studs, external diaphragm, and through diaphragm) in the embedded region on the reduction of the embedded depth was assessed. Performance indices of the tested connections, including the stiffness, lateral loading capacity, energy-dissipation capacity, ductility, and strain distribution of steel tubes, were analyzed based on hysteresis and pushover graphs. The test data demonstrated that all the specimens experienced flexural failure, and consequently, the local buckling of the steel tube was observed in all experiments with the exception of the specimen that had an exposed connection. The specimens with reinforcement in the embedded region had acceptable behavior with ductility coefficients higher than 4.8. The seismic response of the connection with the novel detail showed that the performance indices of the connection with reinforcing anchor rebars and reinforcing internal steel tube in the embedded region were considerably higher than those of the connection without reinforcement in the embedded region and the one in the exposed form. Moreover, the depth at which the connection is embedded was reduced by up to 0.7 times the diameter of the column due to the utilization of reinforcement in the embedded region.

Experimental Study on the Mechanical Properties of Vertical Corrugated Pipe Grout Anchor Connection Joints

Prefabricated buildings’ quality, safety, and construction efficiency are closely related to the connections between various prefabricated components. This study optimizes the design of corrugated pipe-restrained grout anchor lap connections, further simplifying the construction methodology while ensuring reliable connection performance. The objective is to achieve cost savings and accelerate construction progress. A pull-out test of this new type of joint is conducted, generating two sets of 17 specimens each. The research examines the effects of grouting material strength, grout anchor steel bar anchorage length, and U-shaped stirrup spacing on the connection performance of corrugated pipe grout anchor connections. The results indicated that the specimens primarily experience two types of failure: anchorage failure with steel bar pull-out and steel bar tensile failure without anchorage failure. The strength of the grouting material and the anchorage length of the grout anchor steel bar positively correlate with bond anchorage performance. U-shaped stirrups contribute to restraint and enhance the bonding force between the corrugated pipe, grouting materials, and the grout anchor steel bar to a certain extent.

Performance of the Cement Grouting Material and Optimization of the Mix Proportion for the Free Section of the Prestressed Anchor Bar.

Increasing the water-cement ratio and water-reducer dosage of cement slurry enhances its fluidity. However, a high water-cement ratio diminishes the beneficial effects of water reducers on fluidity. The stone content of the slurry decreases as the water-reducer dosage increases. Additionally, the water-cement ratio significantly affects stone content. However, when the water-cement ratio exceeds a threshold value, stone content decreases. Furthermore, the threshold value of the water-cement ratio decreases with increasing water-reducer dosage. Without the addition of the water reducer, as the water-cement ratio increases the overall integrity of the grout stone decreases. The addition of the water reducer alters the surface pore distribution, wherein "uniform small pores" change to "localized large pores." Based on the multi-objective optimization of Matlab, the recommended optimal mix composition for a slow-setting cement slurry is a water-cement ratio of 0.25 and water-reducer dosage of 1.5%. With the use of this optimized mix composition, the stone content and compressive strength increase by 7.8% and 145.6%, respectively, compared to those obtained using the recommended mix ratio in the specifications. Additionally, all relevant performance parameters meet the requirements specified by previous standards.

Experimental Study on the Relationship between the Degree of Surrounding Rock Fragmentation and the Adaptability of Anchor Support

Taking the roadway peripheral rock anchoring unit as the research object, the rock compression test containing the anchor solid was carried out to analyze the influence of the degree of peripheral rock fragmentation and the anchor support method on the mechanical properties of the rock body. The test results showed that the smaller the size of the structural surface, the more a greater number of anchor rods were needed, which in turn provided better support. With the increase in the size of the structural surface, the uniaxial compressive strength and modulus of elasticity of the specimen showed a gradual decrease. Numerical tests of the uniaxial compression of rock containing cohesive units showed that the deformation of the specimen near the anchor bar was significantly reduced, while the main rupture surface was blocked, and an obvious reinforcement zone was formed near the anchor bar. Under the double-anchor condition, the anchor tension stress was more obvious, the reinforcement zone was wider, and the rock rupture surface was strongly blocked, all of which made its reinforcement effect the more obvious. This double-anchor condition showed that the anchoring effect of the anchor rods on the specimens was reflected in two aspects of reinforcement and crack stopping. The denser the anchor rods, the wider the reinforcement zone and hence the more likely that the superposition effect will occur, which allowed the anchor rods to play a greater supporting role in stabilizing the rock. The research results can provide a theoretical basis for the design of anchor support and early warning prediction of destabilization damage in the fractured surrounding rock of coal mine roadways.

Complete Removable Prosthesis Stabilized on Implants: Interest and Use of the Locator® Attachment

The complete removable denture retained by implants is a widely used therapeutic option, recognized for its functional and psychological esthetic rendering. Currently, the practitioner has an arsenal of retention systems at his disposal (axial attachments, anchor bars...) and since 2000, the Locator® attachment has been added to the large number of axial attachments. Thus, this article proposes to describe it and to expose, through two clinical cases, the process of its placement.

Experimental Study on Drilled Shaft Reinforcing Bar Anchorage in Footings

Experimental Study on Drilled Shaft Reinforcing Bar Anchorage in Footings

Lateral Load Behavior of C-PSW/CFs Using Steel Members as Boundary Elements

Composite plate shear walls/concrete-filled (C-PSW/CFs), also known as SpeedCore systems, are a relatively new structural member in American codes and standards. Prior research has focused primarily on C-PSW/CF walls with either flange/closure plates or filled composite members as boundary elements. Walls without boundary elements have also been studied, but they are no longer permitted by the American Institute of Steel Construction (AISC 341-22). The reason is that composite walls without boundary elements do not provide adequate ductility for seismic design. This paper presents the results of experimental and numerical studies conducted to evaluate the cyclic lateral load behavior of C-PSW/CFs using hot-rolled structural steel members as boundary elements. The steel web plates of the C-PSW/CF specimens were connected to each other using threaded tie bars with double nut connections. Composite interaction between the steel and concrete infill was achieved using the tie bars and additional shear studs welded to the boundary elements. The composite walls were embedded and anchored to reinforced concrete foundation blocks using welded deformed bar anchors. The experimental investigations focused on the cyclic lateral load-drift responses including test observations and limit states, moment-rotation response of the plastic hinge and the section moment-curvature relationship, overall lateral stiffness, strength, and displacement ductility. The experimental results show that the specimens exceeded their nominal flexural capacities calculated using the plastic stress distribution method or fiber-based section modeling using measured material properties. The specimens had plastic hinge rotation capacity greater than 0.028 rad. and displacement ductility ratio greater than 5.2. Detailed 3D nonlinear inelastic finite element models and simpler fiber-based macro models of the tested specimens were developed and benchmarked using experimental results. The detailed 3D finite element models can reasonably simulate the global and local behavior of the specimens, and are recommended for conducting further parametric studies of composite wall design details. Simpler fiber-based macro models can efficiently simulate the cyclic lateral load behavior of the specimens, and are recommended for modeling C-PSW/CFs while simulating the behavior of multi-story building structures.

Field experimental study on the pull-out characteristics of a new type of expanding shell bolt

Rock bolt foundation is becoming increasingly popular for transmission line engineering in mountainous areas due to the ability to maximize rock foundation bearing performance, reduce foundation size and burial depth, and save investment. However, failure modes such as pull-out of bolt can lead to insufficient utilization of bearing capacity of rock bolt. To overcome this problem, a new form of expanding shell bolt is proposed and the effect of several variables including grouting materials, bolt diameter, site weathering degree, and anchoring depth are investigated in this study. The results indicate that the new expanding shell bolt may significantly increase the pull-out bearing capacity compared to common rock bolts, due to the built-in effect between the bottom part of bolt and the rock on the hole wall. The effect of grouting material and anchoring length on the shell anchor's uplift bearing capacity is minimal. Considering that the ultimate tensile strength when the anchor bar breaks depends on the diameter of the steel bar, increasing the diameter of the anchor bar will effectively improve the pull-out characteristics of the bolt. The failure mode of anchor rods is also influenced by the rock layers. Rock layers with lower weathering levels have stronger embedding force, and the expansion head can effectively play a role. Due to the group anchor effect, the ultimate uplift bearing capacity of group anchor foundation in rocks is not simply the sum of the bearing capacity of each one, but must be multiplied by the group anchor coefficient. This coefficient is close to 0.9 in moderately weathered and strong-medium weathering sites. Finally, the calculation method for ultimate pullout force of expanding shell bolt is established. The feasibility of this method is verified by comparing on-site test values and calculated values.Author keywords: Rock bolt; Expanding shell bolt; Pull-out bearing capacity; Failure mode; Group anchor effect.

Experimental study on anchorage performance and mechanism of hooked bars with a pre-yield anchorage failure

In RC exterior beam-column joints, reliable anchorage of beam bars using hooked bars is a common approach to ensure sufficient joint rotation capability. The anchorage failure criterion and the influence of axial load and side cover on anchorage strength are unclear with the limitings of the existing test setup and test approach. Twenty-two simulated beam-column joint tests with hooked bars anchorage were therefore conducted. A specially designed test setup was proposed to ensure the simultaneous failure of hooked bars within a specimen, while a novel approach was employed to separate the anchorage force of the hook portion into bearing and bond forces based on stress distribution measurement. The experimental results show that the anchorage strength of hooked bars and hook portion bearing strength increase as side cover thickness and axial load increase, which may potentially alleviate joint congestion. Additionally, the study identifies that the hook portion bearing strength dominates the anchorage failure mechanism of hooked bars, prompting the proposal of an anchorage failure criterion. Based on this criterion, models for anchorage strength and anchorage force-slip relationship were proposed, which are applicable to hooked bars with varying inner bend diameters in actual structures. To examine the safety and validity of the proposed equation for anchorage strength, it was compared against a hooked bar test database with 363 anchorage specimens, as well as several existing models. The database analysis showed potential safety risks with the GB50010-2010 model. Notably, the proposed model demonstrated the highest accuracy in predicting the anchorage strength of hooked bars.