Pullout Resistance Research Articles

Mechanical properties of combined packable and high-filled flowable composite used for the fixed retainer: an in vitro study

BackgroundClinicians often utilize both flowable and packable composites concurrently in bonding fixed retainers. Thus, this study aimed to assess the synergistic effect of these composites in the bonding process.MethodsThis in vitro study divided specimens into three groups: flowable composite (nano-hybrid, Tetric N-Flow, Ivoclar Vivadent), packable composite (nano-hybrid, Tetric N-ceram, Ivoclar Vivadent), and combined use of flowable and packable composite. Shear bond strength (SBS), adhesive remnant index (ARI), and wire pull-out resistance were compared among the groups. Statistical analyses were conducted using ANOVA and Tukey tests to compare study groups. Additionally, Chi-square and Kruskal-Wallis tests were employed to analyze the ARI index among the groups.ResultsANOVA results indicated no statistically significant differences among test groups (P = 0.129) regarding SBS. However, a significant difference existed between flowable and packable composite groups (P = 0.01) regarding ARI scores. Among the study groups, flowable composite exhibited the highest frequencies of ARI scores of 1 and 2, whereas packable composite showed the highest frequency of ARI scores of 0. The combined group had higher frequencies of ARI scores of 0 and 1 compared to the flowable composite. The wire pull-out test revealed that the combined application of flowable and packable composite resulted in significantly lower detachments compared to the packable composite alone (P = 0.008). However, no significant differences were observed in the comparisons between the flowable-packable (P = 0.522) and combined-flowable (P = 0.128) groups.ConclusionThe combined use of flowable and packable composites for fixed retainers demonstrated adequate shear bond strength and ideal ARI scores, suggesting it as a suitable adhesive system for bonding orthodontic fixed retainers.

Experimental and Numerical Evaluation of Pullout Resistance of a Polymeric Strap

Experimental and Numerical Evaluation of Pullout Resistance of a Polymeric Strap

Experimental research on pull-out behavior of steel-UHPC composite beams with new composite dowels connectors

In order to study a new type of steel-UHPC composite connector, a total of 16 steel-UHPC composite connectors with steel dowels and studs and steel-UHPC composite connectors with steel dowels without studs were designed and manufactured, and the pull-out test, finite element simulation and theoretical analysis were carried out. The load-slip curve, ultimate pull-out bearing capacity, crack development law of the UHPC layer and crack growth trend of the steel-UHPC interface were experimentally studied. The influence of the type of connector, the height of the steel dowel and the inclination angle of the steel dowel on the ultimate pull-out bearing capacity and failure mode of the specimens were compared by parameter analysis. The test results are compared with the finite element analysis results to verify the accuracy of the finite element model. A simplified calculation formula for the pull-out bearing capacity was proposed. The results showed that the failure modes of 16 specimens were the shear failure and axial tensile failure of the UHPC, both of which were ductile failures. The bearing capacity in the elastic stage and ultimate bearing capacity of the steel dowel connector with headed studs were higher than those of the steel dowel connector. After adding headed studs, the pull-out bearing capacity of the specimens could be increased by about 49% ∼ 84%. When the longitudinal steel bars were added to the bottom of the steel dowel connector with headed studs, the ductility in the loading stage and ultimate bearing capacity of the specimen could be improved. The steel dowel composite connector with headed studs with a steel dowel height of 100 mm and an inclination angle of 65° had better pull-out resistance.

Biomechanical Properties of Novel Porous Scaffold Core and Hollow Lateral Hole Pedicle Screws: A Comparative Study in Bama Pigs.

Screw loosening is a common complication of internal fixation of pedicle screw. Therefore, the development of a pedicle screw with low loosening rate and high biosafety is of great clinical significance. This study aimed to investigate whether the application of a porous scaffold structure can improve the stability of pedicle screws by comparing the biomechanical properties of novel porous scaffold core pedicle screws (PSCPSs) with those of hollow lateral hole pedicle screws (HLHPSs) in a porcine lumbar spine. Thirty-two pedicle screws of both types were implanted bilaterally into the L1-4 vertebrae of four Bama pigs, with our newly designed PSCPSs on the right and HLHPSs on the left. All the Bama pigs were sacrificed 16 weeks postoperatively, and the lumbar spine was freed into individual vertebrae. Biomechanical properties of both the pedicle screws were evaluated using pull-out tests, as well as cyclic bending and pull-out tests, while the mechanical properties were assessed using three-point bending tests. The data generated were statistically analyzed using paired-sample t-tests and two independent sample t-tests. We found that the maximal pull-out forces before and after cyclic bending of the PSCPSs (1161.50 ± 337.98 N and 1075.25 ± 223.33 N) were significantly higher than those of the HLHPSs (948.38 ± 194.32 N and 807.13 ± 242.75 N) (p < 0.05, p < 0.05). In 800 cycles of the bending tests, neither PSCPS nor HLHPS showed loosening or visible detachment, but their maximal pull-out forces after cyclic bending tests decreased compared to those in cycles without cyclic bending tests (7.43% and 14.89%, respectively), with no statistical significance (p > 0.05 and p > 0.05, respectively). Additionally, both screws buckled rather than broke in the three-point bending tests, with no statistically significant differences between the maximal bending load and modulus of elasticity of the two screws (p > 0.05 and p > 0.05, respectively). Compared with the HLHPSs, the PSCPSs have greater pull-out resistance and better fatigue tolerance with appropriate mechanical properties. Therefore, PSCPSs theoretically have significant potential for clinical applications in reducing the incidence of loosening after pedicle screw implantation.

Auxetic fixation devices can achieve superior pullout performances compared to standard fixation concepts

Despite bone screws being the most commonly inserted implant in orthopaedic surgery, 10% of fracture fixation failure is a result of screw migration or pullout. In this study, the effect of four auxetic structures on the pullout performance of a novel unthreaded bone fastener was investigated through experiments and numerical simulations. The auxetic fasteners included the re-entrant, rotating squares, missing rib, and tetrachiral structures. Parametric CAD models were developed for each, and polymer samples manufactured using a stereolithography process. Pullout testing using bone analogue material found the rotating squares fastener to achieve superior pullout resistance 2.5 times that of the non-auxetic control sample. With a pullout to push-in force ratio of 33.7, this fastener achieved high pullout resistance with a low insertion force improving ease of installation. The Poisson’s ratio of the structure was determined using image analysis to be −1.31, similar to the missing rib and re-entrant types. The low axial stiffness of 12.1 N mm−1 for the rotating squares fastener was the reason for superior performance, allowing axial and resulting transverse strain to be initiated at relatively low load. The effect of increased diametral interference was investigated, and the re-entrant structure found to be superior with pullout resistance improved by 342%. This work provides a foundation for further development of unthreaded auxetic bone fasteners, which have the potential to replace screws for some orthopaedic applications and significantly reduce the prevalence of pullout as a failure mode.

Enhancing spinal bone anchor pull-out resistance with an L-shaped anchor.

The success rate of spinal fusion surgery is mainly determined by the fixation strength of the spinal bone anchors. This study explores the use of an L-shaped spinal bone anchor that is intended to establish a macro-shape lock with the posterior cortical layer of the vertebral body, thereby increasing the pull-out resistance of the anchor. The performance of this L-shaped anchor was evaluated in lumbar vertebra phantoms (L1-L5) across four distinct perpendicular orientations (lateral, medial, superior, and inferior). During the pull-out experiments, the pull-out force, and the displacement of the anchor with respect to the vertebra was measured which allowed the determination of the maximal pull-out force (mean: 123 N ± 25 N) and the initial pull-out force, the initial force required to start motion of the anchor (mean: 23 N ± 16 N). Notably, the maximum pull-out force was observed when the anchor engaged the cortical bone layer. The results demonstrate the potential benefits of utilising a spinal bone anchor featuring a macro-shape lock with the cortical bone layer to increase the pull-out force. Combining the macro shape-lock fixation method with the conventional pedicle screw shows the potential to significantly enhance the fixation strength of spinal bone anchors.

Study of the dynamic interactions between helix-stiffened cement mixing piles and soft soil under oblique incidence of SV waves in arbitrary space

Helix stiffened cement mixing (HSCM) piles are extensively utilized in soft soil sites due to their excellent seismic and pullout resistance. Initially, the equivalent nodal force formulas for each face under the oblique incidence of SV waves in any spatial direction are derived based on the viscous-spring artificial boundary. The method's applicability in studying pile–soil interactions is verified based on existing pile–soil tests. Subsequently, the HSCM pile–soil model is constructed using finite element software through a Python program. Various analyses of accelerations, relative displacements, soil reactions, and pile–soil dynamic p-y curves are conducted using two different directions of incidence angles (horizontal and vertical) and various types of seismic waves. Subsequently, the backbone line of the dynamic p-y curve is plotted, revealing the pile–soil interaction mechanism under spatial oblique incidence. Finally, Matlock's formula is modified to ensure its applicability to pile–soil interactions under spatially oblique incidence. The results demonstrate that loading the Kobe wave causes the peak acceleration in the x direction, the peak pile–soil relative displacement, and the peak pile-side soil reaction force to increase by 22.64 %, −18.90 % and 18.42 %, respectively, compared to those of the El Centro wave.

Numerical evaluation of dimension effects of cold-drawn shape memory alloy crimped fiber on pullout resistance

A finite-element (FE) pullout model was developed and validated by a previous experimental pullout test of cold-drawn shape memory alloy (SMA) crimped fiber. Then, how the crimped fiber dimensions, such as the diameter, wavelength, embedded wave, and wave depth, influence its pullout behavior is investigated. The FE results indicate that the fiber diameter must be large enough to produce a good flexural rigidity. The recommended diameter is about 1.0 mm. However, it should note that the pullout resistance is not improved much for thicker fiber. The short wavelength is more effective than the long one because of the higher maximum pullout stress and the more peak points. The more embedded waves produce the higher pullout resistance; however, the increasing pullout resistance is slowed down when the maximum pullout stress exceeds the yield strength. A 5-embedded wave is proposed to produce a reasonable pullout resistance whereas satisfying the economically used material. Finally, deep-crimped fiber generates a higher pullout resistance than shallow-crimped fiber. Based on the effect of the dimensions on the pullout behavior, an optimum dimensions concept is proposed for crimped fiber.

Enhance the performance of steel-wood composite screw connections with fast-curing adhesive

In composite floors composed of the H-steel and the wood panel, screw connection is one of the design keys. In this paper, the method of using fast-curing epoxy resin to anchor the screw tip was proposed, and six sets of pull-out tests and five sets of push-out tests of epoxy-wood-combined anchored screws were conducted to analyze the influence of the effective meshing length and the epoxy meshing ratio on the connection performance, respectively. Firstly, compared with ordinary screws, the pull-out stiffness and strength of epoxy-anchored screws were increased by 79.8 % and 153.9 %, respectively. Secondly, compared with the ordinary screw connection, the initial shear stiffness and capacity of the steel-wood composite connection were increased by 60.0 % and 22.8 % when the epoxy meshing ratio was 0.25, respectively. Thirdly, the modified effective meshing length of epoxy-anchored screws was proposed. Finally, based on the calculation formula for screws with two plastic hinges in Eurocode 5, the two parameters of pull-out resistance and yield moment for the screw were modified, thus improving the calculation accuracy of shear capacity for combine-anchored screw connections by about 21.0 %.

Study on the characteristics and influence factors of pull-out resistance of vetiver root in expansive soil

Study on the characteristics and influence factors of pull-out resistance of vetiver root in expansive soil

A novel capitate bone Ilizarov external fixator for treating Kienböck’s disease: an anatomical and biomechanical study

This study aims to measure anatomical data of the capitate bone, develop an external fixator for treating late-stage osteonecrosis of lunate through Ilizarov technique, and evaluate its biomechanical performance. We selected eight wrist joint specimens to measure various parameters of the capitate bone, including its length, the distance from the junction of capitate head and body to the proximal end, as well as the width of its proximal head and distal body. Additionally, we measured these same indicators in 107 patients who had undergone wrist X-ray examination. Based on our measurements, we categorized the capitate bone into two groups and designed two types of capitate bone Ilizarov external fixator (CIEF) for it. Then, we compared it with the orthofix external fixator (OEF) through dynamic fatigue biomechanical experiments and pull-out resistance experiments. The results of the measurement revealed two categories of general patterns in the capitate bone. The first type maintains a consistent longitudinal axis between the proximal and distal ends. The second type is characterized by its proximal end being close to the radial side and its distal end being close to the ulnar side. In the dynamic tensile fatigue test, CIEF-A and CIEF-B had smaller maximum displacement values compared to the OEF (P < 0.05). In the anti-pull-out experiment, both CIEF-A and CIEF-B exhibited higher maximum pull-out force than the OEF (P < 0.05). CIFE is a treatment for advanced osteonecrosis of the lunate bone. It is specifically designed to align with the anatomical characteristics of the capitate bone, providing excellent biomechanical properties and a simple clinical procedure. However, additional clinical experiments are needed to confirm its effectiveness in the future.

Pull-Out Resistance of Rebar Stake Depending on Installation Conditions and Compaction Levels of Agricultural Soil

Pull-Out Resistance of Rebar Stake Depending on Installation Conditions and Compaction Levels of Agricultural Soil

Effect of silica fume on Pullout capacity and corrosion resistance of hook bars in the external beam-column concrete joint

Purpose This study aims to determine the effect of replacing a portion of the cement in the concrete mixture with silica fume (SF) on the corrosion resistance of reinforcing bars, the compressive strength of concrete and the tensile strength of hook bars in both corroded and non-corroded external joints of structures. The external beam-column connection was studied because of its critical role in maintaining structural continuity in all three directions and providing resistance to rotation. Design/methodology/approach In external concrete joints, the bars at the end of the beams are often bent at 90° to form hooks that embed in columns. Owing to the importance of embedding distance and the need to understand its susceptibility to corrosion damage from chloride attack, a series of experiments were conducted on 12 specimens that accurately simulate real-site conditions in terms of dimensions, reinforcement and hook bars. SF was replaced with 10% and 15% of the weight of cement in the concrete mixture. To simulate corrosion, the specimens were subjected to accelerated corrosion in the laboratory by applying a low continuous current of 0.35 mA for 58 days. Findings The results revealed the effect of SF in improving the compressive strength of concrete, the pullout resistance of the hook bars and the corrosion resistance. In addition, it showed an apparent effect of the corrosion of reinforcing bars in reducing the bonding strength of hook bars with concrete and the effect of SF in improving this strength. Originality/value It was noted that the improvement of the results, achieved by replacing 10% of the weight of cement with SF, was significantly close to the results obtained by replacing 15% of the SF. It is recommended that an SF ratio of 10% be adopted to achieve the greatest economic savings.

Predicting the Pullout Resistance of Denti-Steel Strips Embedded in Cohesionless Soil

Predicting the Pullout Resistance of Denti-Steel Strips Embedded in Cohesionless Soil

Pull-out resistance of connected K-wires for osteosynthesis: development of a numerical model

A predictive finite element model was developed to investigate the best configuration of a fixation pins system consisting of two K-wires inserted in a synthetic model (Sawbones®) at different angles and secured to a connecting rod. Two key parameters were considered to determine the best configuration delivering the higher pull-out strength and lower pull-out length: the diameter and insertion angle. Results show that as the diameter and insertion angle increased, the pull-out force increased, while the pull-out length decreased. Results are successfully compared with available experimental data in literature. This model can be used as an alternative to experimental study.

Pull-out performance of grouting sleeve connection with short studs shear keys in modular steel building

In this paper, a new type of grouting sleeve connection joint with short studs shear key is proposed for the connection of high-rise modular steel structures. To study the tensile properties of the grouting connection in the modular structure, seven groups of 21 specimens were tested by push-out test. The results show that: (1) The axial bearing capacity of the specimen with a diameter of 16 mm studs is between 3549.2 kN and 3922.4 kN, and the anchorage strength is between 15.07 MPa and 16.66 MPa; (2) The bearing capacity of the connection consists of four parts, including the shear capacity of the studs, the shear capacity of the studs weld collar, the friction and bonding force of the interface. The shear capacity of the stud provides about 65 % of the bearing capacity; (3) The ultimate displacement ranges from 4.69 mm to 6.93 mm, and the ductility coefficient is 2.42–3.05. Then, combined with the test and simulation, the force mechanism of the connection is analyzed, and the design suggestion and the calculation method of the bearing capacity of the connections are put forward. Compared with the existing grouting connection joints, the bond strength of the connection proposed in this paper is 26.7 % higher, showing stronger pull-out resistance.

Effect analysis of uneven thickness of resin annulus on anchorage failure of cable bolt and uniformity guarantee device

Resin grouted cable bolts are widely used in the control of surrounding rock in underground engineering such as roadways and tunnels. This study conducted theoretical analysis and laboratory experiments to investigate the influence mechanism and characteristics of the uneven thickness of the resin annulus on the anchorage performance of the cable bolt, and developed an effective method for controlling the uneven thickness. The theoretical analysis of the shear stress distribution in the resin annulus under tension revealed that, when the thickness of the resin annulus is uniform, the shear stress in the resin annulus and interface around the cable bolt has balanced distribution overall. When the resin annulus thickness is uneven, the shear stress level is higher in the thinner area compared with the thicker area of the resin annulus. The pullout test results for cable bolt specimens anchored with different resin annulus thicknesses reveal that, as the thickness uniformity of the resin annulus decreases, the pullout load of the anchored specimen decreases to different degrees. According to the structure of the cable bolt and the resin anchoring construction characteristics, the resin annulus thickness uniformity guarantee device (RATUGD) was designed. The results obtained by a device working effect experiment reveal that the RATUGD can significantly improve the thickness uniformity of the resin annulus, and the pullout resistance of the anchored specimen is also ensured when the device is used. This study elucidated the influence mechanism of an uneven resin annulus on the anchoring performance of a cable bolt to a certain extent. Additionally, technology that ensures the resin annulus uniformity is proposed to further ensure and enhance the support effect of a resin grouted cable bolt on the surrounding rock of underground engineering such as roadways and tunnels.

Integrating Root Morphology Based on Whole-Pullout Test of Model Roots: A Case Study

To investigate the sensitivity and significance of different morphological characteristics of plant root systems on vertical pullout resistance, this study considered four main influencing factors: the number of lateral roots, taproot length, the branching angle of the lateral root, and the unit weight of the soil around the root. PC plastic model roots were employed to conduct a vertical pullout orthogonal experiment. A comprehensive μX theoretical analysis method based on the whole root system pullout test was applied for a stress analysis on root segments. Based on the results, the factors affected the vertical pullout resistance of plant root systems in the order of number of lateral roots &gt; taproot length &gt; unit weight of soil around the root &gt; branching angle of the lateral root. When the number of lateral roots increased from 2 to 3, the vertical pullout resistance increased by 64%. Also, when the taproot length increased from 50 to 60 cm, the vertical pullout resistance increased by up to 46%. Furthermore, the unit weight of soil around the roots had a positive linear correlation with vertical pullout resistance. Based on the results, the number of lateral roots and the taproot length were the primary factors affecting the magnitude of the root system’s vertical pullout resistance. When selecting plants for slope protection, plant types with a larger number of lateral roots and longer taproots should be considered as the two most significant factors for achieving a better slope protection methodology.

Effects of cyclic loading on soil-geogrid interaction characteristics

The benefits of geosynthetic-reinforced soil systems over conventional earth-retaining structures are now well established. These reinforced systems are often subjected not only to static loads, but also to seismic and/or traffic loads, in which case the effects of repeated loading on soil-geosynthetic interaction characteristics should be properly considered. This study investigates the behaviour of a geogrid typically used for soil reinforcement under cyclic pullout loading through load-controlled laboratory pullout tests. To examine the influence of cyclic loading amplitude, number of cycles and static pullout force acting on the geogrid at the onset of cyclic loading, distinct loading patterns are considered. A well-graded residual soil from granite is used as backfill material. A comparison between the cyclic and monotonic pullout response of the reinforcement is then established in order to identify any potential strength loss attributed to cyclic loading. The experimental results show that the ultimate pullout resistance of the geogrid embedded in medium dense residual soil from granite may be adversely affected by cyclic loading. The cumulative cyclic displacements of the reinforcement are more pronounced during the initial loading cycles, but tend to stabilize with the increasing number of cycles when the soil is densely compacted. In the presence of dense soil, the cyclic strains of the geogrid specimen are particularly significant at the front section and almost negligible towards the back end.

Influence of Fines Content and Pile Surface Characteristics on the Pullout Resistance Performance of Piles.

In this study, the direct shear test and model pullout test results are presented to assess the impact of soil fines content and shear resistance characteristics of the pile-soil interface on the pullout resistance of drilled shafts. The direct shear test on the soil-pile interface was conducted based on the pile surface simulated using sandpaper with three roughness types (#24, #40, and #400) and varying fines content. The direct shear test results of soil showed that the internal friction angle decreased by about 29% and the cohesion increased by about 110% when the fine powder content increased from 5% to 30%. Specifically, in the case of soil-sandpaper (#24), the interface friction angle decreased by about 31%, and the adhesion increased by about 16%. The sandpaper with a roughness of #40 and #400 also showed a similar trend. Normalizing the shear strength parameters from the direct shear test demonstrated an intersection between the normalized curves of the friction angle and cohesion (or adhesion) within a specific fines content range. This suggests that shear strength parameters play a significant role based on fines content. Analyzing the normalized index using model pullout test results indicated the necessity to evaluate the contribution of friction angle and cohesion (or adhesion) of the shear surface, taking into account the fines content of the soil for predicting pile pullout resistance.