Anchor Depth Research Articles

Cyclic loading test for brick masonry veneer anchored to reinforced concrete walls

Despite the importance of seismic design for brick masonry veneer anchored to reinforced concrete (RC) backup walls, the effects of several design parameters on the seismic capacity of such nonstructural component remain unexplored. In this study, material tests and cyclic loading tests were performed to investigate the seismic performance of connection for the brick masonry veneer wall anchored to a RC back-up wall under excitation. To this end, tensile tests were first carried out for each element comprising the unit connection to investigate the basic material strengths. A cyclic loading test was then performed on brick-tie-concrete subassembly to investigate the seismic capacity of the unit connection subjected to seismic loads. The major test parameters included the type and embedded depth of veneer anchor, type of mechanical fastener, compressive strength of concrete, and use of insulation. Based on the material strengths and unit specimen strength, the failure mode and seismic capacity of the unit connection for brick veneer anchored to concrete block were evaluated. The test results showed that the presence of the insulation significantly affected the seismic capacity. Based on the test results, design recommendations were proposed to improve the prescriptive design or general design in current practice for brick masonry veneer walls.

Theoretical and experimental studies on air-inflated rubber dam anchored on sidewall of the rigid base

A theoretical study was conducted to investigate the cross-sectional configurations and the tensile forces of an air-inflated rubber dam anchored on the sidewall of the rigid base. A series of large-scale model tests were conducted using rubber dam models with a cross-sectional perimeter of 1.0 m and a length of 8.5 m. The results obtained from the analytical solutions agree well with those obtained from model tests. It is found that there is an optimum height of the rubber dam, especially for larger anchor depth with the increase of the inflated air pressure. The smaller the anchoring depth the higher the optimum inflated air pressure. The contact length between the rubber dam and the rigid base gradually decreases with the increasing inflated air pressure. The greater the anchor depth, the faster the contact length decreases to zero. Generally, the tensile force linearly increases with the increase of the normalized air pressure and the decrease of the anchor depth.

Numerical modeling of open-ended piles

Deep foundations are generally used when significant loads are applied, and the site conditions do not allow for the implementation of soil reinforcement processes. This research focuses on studying the behavior of piles in a frictional environment, used as foundations for offshore structures in dense sands, involving anchor depths and overloads significantly higher than those encountered in onshore applications. The bearing capacity of open-ended driven piles plays a crucial role in this study. Therefore, a series of tests were conducted in the literature on model piles in a calibration chamber, which is considered a tool for physical modeling, allowing for significant penetration of instrumented model piles under confinement conditions similar to those experienced by real piles. Emphasis is placed on predicting the ultimate load capacity of open-ended piles using numerical methods. Calculations were performed using the finite element code PLAXIS to numerically reproduce the same shear stresses as those measured on the model during various phases of the experiment. The approach aims to validate the documented experiments in the literature and compare the ultimate load capacity of an open-ended pile to that of a closed-ended pile. Our study is limited to the case of a single pile, subject to static and axial force. The results show that it is possible to achieve a good agreement between the experiment and the numerical modeling with a relatively simple model, provided that the soil parameters are chosen correctly and the interface stiffness is adequately simulated.

Study on Bond Anchorage Behavior of Small-Diameter Rebar Planting under Medium and Low Cycle Fatigue Loads

In this paper, we describe how, through the combination of field testing and finite element simulation, the bonding and anchoring performance of small-diameter rebar under the action of medium and low cycle fatigue load was studied and the corresponding conclusions were obtained: ① Through the test, the performance parameters of the 6 mm and 8 mm rebar planting specimens were obtained after the rebar was subjected to 10,000, 50,000 and 100,000 times of medium and low cycle fatigue loading at depths of 10d, 15d and 20d. The analysis shows that the medium and low cycle fatigue load has a significant effect on the elastic ultimate load, elastic ultimate slip and ultimate slip of the small-diameter rebar planting specimens. With the increase in fatigue loading times, the elastic ultimate load of the rebar specimen decreased continuously, and the elastic ultimate slip and ultimate slip showed an increasing trend. By increasing the anchor depth, the influence of fatigue load on the anchoring performance parameters of the rebar planting specimen can be reduced. Under the influence of the upper ultimate condition of 100,000 times of fatigue loading, the ultimate load and failure mode of the planted bars basically did not change compared with the control specimens without fatigue loading. ② Based on the performance parameters of the rebar planting specimens obtained from the field test, the bond–slip constitutive relationship of the adhesive–rebar interface of the small-diameter rebar planting under the medium and low cycle fatigue load is analyzed and proposed. The F-U relationship of the spring element under the fatigue load is defined to simulate the bond–slip behavior of the adhesive–rebar interface. The finite element simulation results are in good agreement with the field test results. ③ Through a large number of finite element numerical simulation results, the elastic ultimate load calculation formulas of 6 mm and 8 mm diameter rebar planting specimens under medium and low cycle fatigue loads are obtained.

Influence of parameters on the ultimate penetration depth of a double-plate vertically loaded anchor in soft clay

To make a new type of double-plate vertically loaded anchor (DPVLA) penetrate into clay deeper, the influence of parameters on the ultimate penetration depth of DPVLAs in soft clay should be investigated. The expression of the ultimate penetration depth applicable to DPVLAs in clay was determined in terms of the formula of the ultimate penetration depth of anchors with a wedge-shaped section. Based on the drag penetration tests, the movement direction of the bottom fluke of DPVLAs with different lengths of the bottom fluke and different included angles was obtained. By the finite-element method, the upper bound solutions of bearing capacity factors of DPVLAs with different included angles and different lengths of the bottom flukes were also obtained, which correspond to the maximum penetration depth induced by the initial orientation of the anchor. According to the determined expression of the ultimate penetration depth of DPVLAs, the ultimate penetration depth of DPVLAs with different included angles and different lengths of the bottom fluke in clay can be calculated. The results showed that increasing the length of the bottom fluke can increase the ultimate penetration depth when the included angles were the same for DPVLAs not only in the clay with zero strength at the seabed but also in the clay with uniform strength. However, when the length of the bottom fluke is the same, increasing the included angle of DPVLAs in clay can significantly reduce the ultimate penetration depth.

Numerical Investigation of the Formation of a Failure Cone during the Pullout of an Undercutting Anchor.

Previously published articles on anchors have mainly focused on determining the pullout force of the anchor (depending on the strength parameters of the concrete), the geometric parameters of the anchor head, and the effective anchor depth. The extent (volume) of the so-called failure cone has often addressed as a secondary matter, serving only to approximate the size of the zone of potential failure of the medium in which the anchor is installed. For the authors of these presented research results, from the perspective of evaluating the proposed stripping technology, an important aspect was the determination of the extent and volume of the stripping, as well as the determination of why the defragmentation of the cone of failure favors the removal of the stripping products. Therefore, it is reasonable to conduct research on the proposed topic. Thus far, the authors have shown that the ratio of the radius of the base of the destruction cone to the anchorage depth is significantly larger than in concrete (~1.5) and ranges from 3.9-4.2. The purpose of the presented research was to determine the influence of rock strength parameters on the mechanism of failure cone formation, including, in particular, the potential for defragmentation. The analysis was conducted with the finite element method (FEM) using the ABAQUS program. The scope of the analysis included two categories of rocks, i.e., those with low compressive strength (<100 MPa) and strong rocks (>100 MPa). Due to the limitations of the proposed stripping method, the analysis was conducted for an effective anchoring depth limited to 100 mm. It was shown that for anchorage depths <100 mm, for rocks with high compressive strength (above 100 MPa), there is a tendency to spontaneously generate radial cracks, leading to the fragmentation of the failure zone. The results of the numerical analysis were verified by field tests, yielding convergent results regarding the course of the de-fragmentation mechanism. In conclusion, it was found that in the case of gray sandstones, with strengths of 50-100 MPa, the uniform type of detachment (compact cone of detachment) dominates, but with a much larger radius of the base (a greater extent of detachment on the free surface).

Tensile performance of cast-in headed anchors in ambient-temperature cured fly ash-based geopolymer concretes with varying fracture energies

The performance of cast-in headed anchors subjected to tensile loading in ambient-temperature cured fly ash-based geopolymer concrete was investigated in this research. Varying sizes of anchors were installed in geopolymer concrete at effective embedment depths ranging between 40 mm and 90 mm. The new experimental results were compared with those of a previous study on the tensile performance of anchors in geopolymer concrete with similar compressive and tensile strengths, but different fracture energy and elastic modulus. The influence on the concrete cone capacity and its angle due to the varying anchor head size ratio and fracture energy were evaluated in detail. A 43% difference in fracture energy between the two geopolymer concrete mixes translated to 17% increase in concrete cone capacity of the tested anchors. Moreover, the obtained results were compared with the existing prediction models, the Linear Fracture Mechanics (LFM), and Concrete Capacity Design (CCD) models, as well as the design models by ACI 318 and AS 3850.1. The results showed that most of the existing models overestimate the concrete cone capacity of anchors tested in this study and the test-to-prediction ratios depend on the effective embedment depth of anchors. After statistical analysis of experimental results, a new modified equation was proposed to extend the use of the existing CCD model to anchors installed in geopolymer concrete studied in this article.

Analysis of air‐inflated rubber dam for flood‐fighting at the subway entrance

AbstractThe air‐inflated rubber dam is innovatively adopted in this paper for temporary flood‐fighting at the subway entrance. Numerical studies using the FLAC2D software are carried out to investigate the behavior of the proposed structure. Laboratory model tests are also conducted to verify the accuracy of the numerical model. The results from the model tests agree well with those from the numerical analysis. Parametric studies are carried out to investigate the influences of the external floodwater head, inflated air pressure, and anchor position on the performance of the proposed air‐inflated rubber dam. It is found that the external floodwater head reduces the tensile force but nonlinearly increases the height of the rubber dam. The inflated air pressure has no obvious effect on the cross‐section of the rubber dam but heavily influences the ultimate flood‐fighting height and tensile force. An optimum design line for the inflated air pressure of the rubber dam is provided. A deeper anchor position results in a smaller ultimate flood‐fighting height. A rubber dam design with a lower anchor depth that has to satisfy the requirements of the anchor bolt is therefore concluded.

Comparison of biomechanical properties associated with the diameter and insertion depth of bone anchors in the femoral condyle of toy breed cadaver dogs

Comparison of biomechanical properties associated with the diameter and insertion depth of bone anchors in the femoral condyle of toy breed cadaver dogs

An experimental study to determine the optimum depth of steel anchors in RC subjected to shear force

Unlike existing in-plane strengthening RC shear-walls, anchors are used in strengthening of RC buildings to attach out-of-plane RC shear-walls or steel profiles. It is necessary to know the shear capacity as well as the ductile and nonlinear behavior of the anchor bolts as a connector to be used in the transfer of the shear force between the existing and new elements in strengthening. Considering that the existing RC structures in Türkiye are designed, according to the earthquake codes, with C14 concrete compressive strength until 1998, C18-20 until 2007, C20 until 2018 and also C25 after 2018, knowing the optimum anchorage depth depending on the concrete strength is of great importance in the strengthening analyzes of these structures. In this study, it was aimed to determine the shear performance and optimum anchorage embedment depth of steel sleeve expansion anchor bolts in RC. For this purpose, a total of 72 push-shear tests were conducted on M10 bolts for 6 different classes of low and normal strength concrete and 4 different anchorage depths. As a result of the experiment, it was observed that the shearing capacity of the anchor bolts increased with the increase of concrete strength and anchorage depth. However, for an optimum anchorage embedment depth, it has been observed that the anchor shear capacity reaches the maximum and remains constant without being affected from increment of the embedment depth and the change in concrete strength.

Optimal Calculation Method for Buried Depth of Ground Anchor of Carrying Rope of Material Ropeway of Transmission Line

The article adopts the soil weight method to propose an optimized calculation method for the buried depth of the ground anchor of carrying rope of material ropeway of transmission line, considering the shallow burial and deep burial situations. In the case of different soil types and conditions, the angle between the carrying rope and the horizontal ground, etc., a calculation process was designed to determine the minimum buried depth of ground anchor that meets the requirements of anti-pulling stability. The calculation result meets the construction safety requirements of ground anchor burying, and provides a calculation basis for the construction of ground anchor burying of carrying rope of material ropeway of transmission line.

Experimental Study on Bearing Capacity of Normal‐ and High‐Strength Steel Screw Anchors

In order to study the bearing capacity of high‐strength steel screw anchors, six groups of screw anchors with different parameters are carried out in in situ construction and tensile capacity test, and the load‐displacement curves of screw anchors with different parameters are obtained. The bearing mechanism, design method, and key design parameters of screw anchors are analyzed. Meanwhile, the test results are compared with theoretical calculation and numerical simulation, respectively. The results show that the drawing capacity of high‐strength screw anchor calculated by the existing standard theoretical calculation formula is conservative. The load capacity of high‐strength steel screw anchor is significantly higher than that of ordinary strength steel screw anchor. Taking steel strength, buried depth, quantity, distance, and diameter as the influencing factors, parametric analysis is conducted on the uplift capacity of high‐strength steel screw anchor in this paper. The embedding depth of screw anchor, the number, spacing, and diameter of anchor plates have significant influence on the drawing capacity of screw anchor. The construction technology of high‐strength steel screw anchor is reliable, and the bearing capacity is good, which can be applied in the soft‐soil power transmission line projects, such as bog and coastal beach. Meanwhile, the research results can provide reference for the design and construction of screw anchor foundation.

Seismic pullout behavior of cast-in-place anchor bolts embedded in plain concrete: Damage plasticity based analysis

The seismic pullout strength of the cast-in-place anchor bolts embedded in the plain concrete is a function of the accumulated tensile damage during the load reversals. The present study deals with the seismic tension analysis of the cast-in-place anchor bolts considering the resultant stiffness and strength degradation phenomena. In this way, a nonlinear fracture-based damage plasticity model is developed and implemented in the Abaqus code. Primarily, the validity and accuracy of the developed constitutive model are assessed based on the existing pullout tests. Then, the developed framework is utilized to assess the seismic pullout response of the anchor bolts with a low embedded depth-to-diameter ratio (hedb⩽10). Assumed parametric study space contains several plain slabs with various anchor diameters, embedded depths, and compressive concrete strengths. Based on the observations, the seismic load results in significant degradation of stiffness (damage) and pullout strength. The seismic-induced damage is increased when the compressive concrete strength and the embedded anchor depth are increased. However, the slender anchors undergo lower damage than the stubby ones. The size effect phenomenon in the concrete material leads to distinct behavior of the cast-in-place anchor bolts with various embedded depth-to-diameter ratios. Considering the crack patterns of the modeled slabs, the degraded stiffness state at the end of the seismic loading step increases the inclination angle of the pullout cracks during the monotonic loading step. The inclination angle of the cracks is detected to be a function of the embedded depth-to-diameter ratio.

Study on shear stress distribution of glass fiber reinforced polymer soil nail in foundation pit support pullout test

To solve the problem of reinforcement bolt corrosion caused by the safe stability problem in geotechnical engineering, and engineering red line in geotechnical engineering, the fiber-reinforced composite material is gradually applied to the civil engineering field, and glass fiber reinforced polymer has high strength, light quality, corrosion resistance, the advantages of easy cutting has been widely used. In this paper, the stress distribution and deformation characteristics of GFRP anchors in the process of pipe pulling are studied through the excavation tube pulling test of GFRP anchors in actual working conditions. Secondly, the performance difference between the GFRP bolt and reinforced bolt in foundation pit engineering is analyzed. The results show that the axial force of the GFRP anchor bolt decays fastest near the anchor head, and decreases with the increase of anchor depth The shear stress distribution is convex. With the increase of the drawing load, the shear stress peak will increase, and the influence range of the shear stress will also increase. With the increase of the load, the shear stress peak of the GFRP bolt and the anchor solid will shift to the position far away from the anchor head.

Connection Strength of Undercut Anchorage Stone Cladding

Experiments were conducted on seventy-two stone panels to investigate the connection strength of undercut anchorage stone cladding. The following factors were considered in this study: the stone type, the distance between the hole center and the edge of the plate, the hole depth and the diameter and type of the undercut anchor. The results show that the stone type and anchor depth are the factors that most strongly influence the anchorage strength. The distance between the hole center and the edge of the plate are secondary factors. The connection strength increases when the distance between the hole center and the edge of the plate from 40 mm to 60 mm. The anchorage strength of percussion anchor is approximately 10% higher than that of a screw-in anchor under the same conditions.

Free-Fall Penetration Behaviors of A New Dynamically Installed Plate Anchor in Marine Clay

A new dynamically installed plate anchor, the Flying Wing Anchor®, has been developed as a sustainable anchor concept for deep-water offshore wind turbines. The anchor is firstly installed by free-fall penetration and then followed by drag embedment. If the anchor is subjected to environmental loads, it dives deeper to mobilize a higher capacity. This study presents a series of free-fall penetration tests with model anchors in different weights to assess the anchor behavior during the free-fall penetration performance in one-layer soil with a constant shear strength profile. Anchor velocities and embedment depths were measured by a magnetometer. An energy-based model and a force-based model were calibrated against the test results of model anchors with different weights. Based on the calibrated force-based model, a series of design charts were developed to estimate the embedment depth of anchors in different sizes and with different impact velocities in various marine clays. The framework to plot design charts presented herein can be potentially applied to other dynamically installed anchors to predict embedment depth in engineering practice.

Hysteretic Response of Tilt-Up Concrete Precast Walls with Embedded Steel Plate Connections

Many connection systems are available that can transfer tension and shear loads from a precast concrete wall panel to a floor slab. However, due to the insufficient anchor depth in relatively thin precast concrete panels, it is difficult to attain adequate ductility and stiffness to ensure structural integrity. Based on the authors’ previous research results, the supplementary reinforcement of embedded steel plates in precast concrete wall panels can enhance stiffness while maintaining allowable displacement and ductility. In this study, three full-size tilt-up precast concrete panels with embedded steel plates were fabricated. Lateral cyclic loads were applied to full support structures consisting of a precast concrete wall panel and a foundation. The test results were compared with the results predicted using existing code equations found in the American Concrete Institute 318-14 and the Prestressed Concrete Institute Handbooks. The test results confirm that the supplementary reinforcement of thin precast concrete wall panels can provide (i) the required strength based on current code equations, (ii) sufficient ductility, and (iii) the energy dissipation capacity to resist cyclic loading.

Experimental and analytical investigation of chemical anchors’s behaviour under axial tensile

In this study, to observe the behavior of chemical anchors embedded in concrete under the tensile effect, 108 different anchor specimens were prepared with different parameters as concrete compressive strength, reinforcement bar diameters, anchor depths, sizes of drilled holes, cleanliness of the drilled holes. Pull-out tests were conducted and obtained data were examined with the axial-load capacities and the failure situations. Finally, the depth of anchors, compressive strength and reinforcement diameter were observed to increase the axial-load-bearing capacity. The specimens cleaned with water could bear more axial loads than cleaned using air. For the anchors installed without cleaning the holes, a significant decrease was observed in the axial-load carrying capacities compared to the other two conditions. The ANN algorithm exhibited a 78.3% prediction success compared with other algorithms. The empirical relations in the literature were found to have limited level of prediction success rates according to the ANN's results.

Pryout capacity of headed stud anchor groups with stiff base plate: 3D finite element analysis

AbstractConcrete pryout failure mode of a group of relatively shallow embedded anchors welded to a steel base plate has not been extensively investigated in the past. Therefore, the failure mechanism and resistance of such anchor groups needs to be clarified. In this paper a three‐dimensional (3D) finite element parametric study for quadruple (2 × 2) anchor groups loaded in shear with no influence of edges is carried out. In the study, embedment depth of anchors and anchor spacing in both directions are varied. The results show that the increase of anchor spacing perpendicular to the shear load direction has no major influence on the concrete pryout capacity, whereas the increase in anchor spacing parallel to the loading direction significantly increases the pryout capacity. For anchor spacing greater than a particular threshold value, the pryout resistance of a group of anchors is approximately equal to the resistance of a single anchor multiplied by the number of anchors. Based on the results of the study, a design formula for anchor group failing in pryout is proposed and compared with the current design code recommendations.

All-Suture Anchor Settling After Arthroscopic Repair of Small and Medium Rotator Cuff Tears

Background: All-suture anchors are increasingly being used in rotator cuff repair. However, there are debates on the micromotion of all-suture anchors. Purpose: To perform rotator cuff repair on patients with rotator cuff tears and different shoulder bone mineral densities (BMDs) and investigate (1) where the anchor is located under the cortex, (2) if there is any anchor migration settling during follow-up, and (3) if structural outcome differs according to shoulder BMD. Study Design: Cohort study; Level of evidence, 3. Methods: We retrospectively investigated 88 patients who underwent arthroscopic single-row repair for small- to medium-sized rotator cuff tears (age [mean ± SD], 58.8 ± 7.1 years) from 712 cases of rotator cuff tendon repair between November 2015 and February 2018. Inclusion criteria were as follows: use of an all-suture anchor; preoperative shoulder BMD; and magnetic resonance imaging (MRI) conducted preoperatively, 2 days after surgery, and 10 months after surgery. Patients were excluded from the study if they underwent open rotator cuff repair (n = 118), got surgery with a double-row technique (n = 178), underwent surgery with anchors other than the all-suture type (n = 273), received anchor insertion in sites other than the greater tuberosity owing to concomitant procedures such as biceps tenodesis and subscapularis repair (n = 29), did not take preoperative shoulder BMD (n = 15), had more than a large-size tear (n = 6), and were lost to follow-up (n = 5). After compression of the all-suture anchor during surgery, the strands were pulled multiple times to ensure that the anchor was fixed onto the bone with appropriate tension. BMD was measured before surgery. Depth to anchor (DA), anchor settling, and repaired rotator cuff integrity were measured with MRI. Patients were categorized into 3 groups: group A (BMD, <0.4 g/cm2; n = 31), group B (BMD, 0.4-0.6 g/cm2; n = 32), and group C (BMD, >0.6 g/cm2; n = 25). A total of 65 patients had follow-up MRI. On the basis of rotator cuff tendon integrity, patients were categorized into either a sufficient thickness group (group S, Sugaya classification grade II or lower; n = 44) or an insufficient thickness group (group I, Sugaya classification grade III or higher; n = 21). Results: On time-zero MRI, the DA differed significantly among groups (group A, 3.62 ± 2.02 mm; group B, 5.18 ± 2.13 mm; group C, 6.30 ± 3.34 mm) (P = .001). The DA was deeper in patients with a higher BMD at time zero (r = 0.374; P = .001), but the DA did not differ at follow-up MRI (mean, 10.3 months after surgery). On follow-up MRI, anchor settling tended to increase with deeper time-zero DA (r = 0.769; P < .001). Anchor settling was significantly different among groups (group A, 1.33 ± 1.08 mm; group B, 2.78 ± 1.99 mm; group C, 3.81 ± 2.19 mm) (P = .001). The proportion of patients with sufficient thickness in each group did not show a statistical difference (group A, 70.8%; group B, 72.7%; group C, 57.9%) (P = .550). Conclusion: In conclusion, this study confirmed that the postoperative site of anchor insertion in arthroscopic single-row rotator cuff repair with all-suture anchors was located farther from the cortex in patients with higher shoulder BMD and closer to the subcortical bone in patients with lower BMD. On follow-up MRI, no further settling occurred past a certain distance from the cortex, and there was no significant difference in anchor depth or integrity of the rotator cuff tendon based on shoulder BMD. Therefore, minimal settling in the all-suture anchor did not show clinical significance.