Bolt System Research Articles

Influence of the intramedullary nail locking method on the stiffness of the bone-implant system

Purpose: Bone fractures are one of the most commonly seen problems in veterinary traumatology. The authors of this study strive to find a new intramedullary nail, which is intended for treating femoral bone fractures for canine patients. The purpose of this study was to analyze biomechanical parameters of the intramedullary nails, which use a new bolt system concept. Methods: Dissected femoral bones of a large breed dog were cut in order to simulate interfragmentary gap, and then the bones were stabilized using intramedullary nail with locking bolts. Bone-nail systems were subjected to cyclic loading using force which corresponds to the load on the femoral bone in the first few days after surgery. Micro-CT scans were taken of the bone samples around implant in order to determine deformation and structural parameters of bone tissue. Results: The calculation of the bone-nail system stiffness was done through analysis of the force displacement curves recorded during experimental studies. Using monocortical locking bolts resulted in smaller stiffness of the bone-nail system than using bicortical locking bolts. Conclusions: The results obtained in this study can indicate that the intramedullary nail could work well when used for treatment of bone fractures in dogs. The authors focused on using monocortical bolts which provides good stability and adequate biomechanical environment. Described fixation method is easily adjustable to a particular patient individual parameters.

A novel slip-critical blind bolt: Experimental studies on shear, tensile and combined tensile–shear resistances

This paper presents the results of a series of experimental tests on a novel Slip-Critical Blind Bolt (SCBB) system recently improved by the second author, which can be used to connect an H-beam to a hollow section column. The connection specimens were subjected to monotonic loading under tension, shear and combined tension and shear in order to study their behavior and strength at the component level. Importantly, the plates separating loads and the slip resistances of the SCBB specimens were checked against the nominal values specified by relevant Chinese codes. The test specimens were found to exhibit stable (constant) bolt pretension for at least half an hour after tightening, at values that could be up to 20% higher than the design pretension specified by the code. The test plates separating loads were on average about 45% higher than the nominal tensile strength of the connection computed using the existing design equation. The ultimate tensile loads of the SCBB assemblies were the ultimate strength of the bolt shanks. The ultimate shear loads associated with the shear fractures of the bolt and sleeve were found to be much higher than the nominal shear strength, typically about three times. Under shear or combined tension and shear, the slip resistance can be estimated conservatively using the existing design equations. A bolt group factor may be needed as the shear resistance of a connection having more than one bolt in series tends to be smaller than the arithmetic sum of the individual resistances.

Analytic Study on the Force Transfer of Full Encapsulating Rock Bolts Subjected to Tensile Force

Full encapsulating rock bolts are widely used in mining and civil engineering to keep the stability of underground excavations. Nevertheless, decoupling at the interface between the bolt and grout (first interface) still occurs. To disclose the loading mechanism of the bolting system and preventing decoupling at the first interface, experimental and analytic studies were conducted in this paper. First, a nonlinear shearing-slipping law is used to describe the coupling and decoupling behavior of the first interface. Then, this shearing-slipping law is merged into the anchorage body. Following this, the whole loading process is divided into two components: elastic period and elastic-plastic period. Consequently, the analytic force-deformation relation of bolts is obtained. To confirm the rationality of this solution, experimental tensile tests on bolts were performed. It shows that there was a good match between analytic results and experimental tests. With the confirmed analytic solution, a parameter study is performed to investigate the impact of shearing-slipping parameters on the bolting performance. It indicates that increasing the shearing strength of the first interface and the shearing slipping have a positive impact in improving the bearing capacity of bolts. Inversely, the softening coefficient for the post-failure stage has a negative impact on determining the bearing capacity of bolts. Overall, the shearing strength of the first interface has a major impact in determining the loading performance of bolts.

Design and Structure Analysis of a CNC Laser Engraver Machine

This study aims to design a CNC machine to perform the laser engraving process (called the CNC Laser Engraver Machine). The design stage starts from the laser module unit as an input at the design stage of the 3-Axis CNC Machine to drive the laser. The main geometry of the machine is designed referred to the laser position i.e. workspace and laser height with respect to the engraving table. Then the geometry of the Z-Axis unidirectional laser drive unit is determined to assist when adjusting the laser height of the engraving table. Then the geometry of the laser drive unit in the direction of X-Axis and Y-Axis is designed to move on the engraving area, and then the geometry of the engraving table is designed. After the design is complete, the design is validated by analyzing the structure of the machine based on the conditions and workload of the machine to obtain the appropriate dimensions and materials. The design and structure analysis of the CNC Laser Engraver Machine is carried out by using the CAD software. The design results of the CNC Laser Engraver Machine consist of 5 units i.e. Laser Engraver Module Unit, Z-Axis Unit, X-Axis Unit, Y-Axis Unit and Engraving Table Unit which are mounted with a bolt system. This CNC Laser Engraver machine designed has a workspace of 310 mm x 390 mm in the X-Y plane with the laser height in the Z-Axis direction can be adjusted 10 mm to 60 mm above the engraving table. The total dimensions of this CNC Laser Engraver Machine are 585 mm x 533 mm x 350 mm with a total weight about 22 kg.

Application of automated integrated geotechnical monitoring system in support of rib pillars of large cross-section and length in the Iletsk rock salt field

The Iletsk rock salt field development for 200 years has been carried out is a disordered manner. Alongside open pits, a few underground mines were operated (Elizavetinskaya, Mariinskaya) but not for long and were flooded soon. The flooding of those mines and Mine No. 1 later on was explained by their occurrence inside the top jointed and karstic salt core. Mining safety and efficiency under conditions of flooded Mine 1, as well as actual mining operations on the second and third levels of Mine 2 is ensured by means of handling some geomechanical problems. In the course of the stress–strain assessment in a rib pillar of large cross-section and extension, it was recorded that the load on the rock bolting system in the pillar grew but the deformation studies in the pillar edges showed no straining. The obtained results make it possible to draw a conclusion that the existing rock bolting system performs the duty: it distributes load between rock bolts and holds small pieces of rock salt between the rock bolts in case of inrush. The former function is especially critical for the reliable operation of the whole support system in the conditions of plasticity. The average increment in the load applied to the rock bolting system is estimated as 120 kg per month, or 1.5 ton per year. The integrated geotechnical monitoring system allows recording and display of deformation and incremental loading of support in pillars. The linear patterns of the obtained data make it possible to predict the load increase and to adjust the mining process flows if necessary.

Influence of Driving Direction on the Stability of a Group of Headings Located in a Field of High Horizontal Stresses in the Polish Underground Copper Mines

This paper investigates the problem of stability in a group of headings driven in high horizontal stress fields in the copper ore mines of the Legnica-Glogow Copper Belt (LGCB). The headings are protected with the roof bolting system. This problem is of high importance due to special safety regulations which apply in mining workings serving as airways and haulageways. The analysis was performed for a group of four headings driven in the geological and mining conditions of the Polkowice-Sieroszowice mine. The stability of the headings was evaluated with the use of Finite Element Method (FEM). The parameters of the rocks used in the numerical modeling have been determined on the basis of the Hoek–Brown classification, with the use of the RocLab 1.0 software. The parameters of the stress field have been identified on the basis of in situ measurements, which were performed in the Polkowice-Sieroszowice mine in 2012. The measurements were carried out with the use of the overcoring method, which is a stress relief method. A CSIRO HI probe was used as the measuring device. The tests were carried out on three measuring points, on which six successful tests were performed. The measurements confirmed the presence of high horizontal stresses in the rock mass. Numerical modeling was performed using the Phase2 v.8.0 software, in a triaxial stress state and in a plane strain state. The rock mass was described with an elastic-plastic model with softening. Numerical analyses were based on the Mohr–Coulomb failure criterion. It was assumed that the optimal measure of the stability of the group of headings is the range of the formed zone of yielded rock mass in the excavation roof. Numerical simulations have shown that the direction of driving the headings in the field of increased horizontal stresses may be of key importance for the stability of the headings in LGOM mines. The greatest extent of the yielded rock mass zone in the excavation roof occurred when the group of headings was driven in the direction perpendicular to the direction of the maximum horizontal stress component σH. The obtained results served to provide an example of the application of a roof bolting system to protect headings driven in unfavorable conditions in a high horizontal stress field.

Safety profile of an intracranial multimodal monitoring bolt system for neurocritical care: a single-center experience.

Intracranial multimodality monitoring (iMMM) is increasingly used in acute brain-injured patients; however, safety and reliability remain major concerns to its routine implementation. We performed a retrospective study including all patients undergoing iMMM at a single European center between July 2016 and January 2020. Brain tissue oxygenation probe (PbtO2), alone or in combination with a microdialysis catheter and/or an 8-contact depth EEG electrode, was inserted using a triple-lumen bolt system and targeting normal-appearing at-risk brain area on the injured side, whenever possible. Surgical complications, adverse events, and technical malfunctions, directly associated with iMMM, were collected. A blinded imaging review was performed by an independent radiologist. One hundred thirteen patients with 123 iMMM insertions were included for a median monitoring time of 9 [3-14] days. Of those, 93 (76%) patients had only PbtO2 probe insertion and 30 (24%) had also microdialysis and/or iEEG monitoring. SAH was the most frequent indication for iMMM (n = 60, 53%). At least one complication was observed in 67/123 (54%) iMMM placement, corresponding to 58/113 (51%) patients. Misplacement was observed in 16/123 (13%), resulting in a total of 6/16 (38%) malfunctioning PbtO2 catheters. Intracranial hemorrhage was observed in 14 iMMM placements (11%), of which one required surgical drainage. Five placements were complicated by pneumocephalus and 4 with bone fragments; none of these requires additional surgery. No CNS infection related to iMMM was observed. Seven (6%) probes were accidentally dislodged and 2 probes (2%) were accidentally broken. Ten PbtO2 probes (8%) presented a technical malfunction after a median of 9 [ranges: 2-24] days after initiation of monitoring and 4 of them were replaced. In this study, a high occurrence of complications related to iMMM was observed, although most of them did not require specific interventions and did not result in malfunctioning monitoring.

Erratum: “Experimental study on dynamic and static performance of a new type of pressure-absorbing energy bolt system” [AIP Adv. 11, 075124 (2021)

Erratum: “Experimental study on dynamic and static performance of a new type of pressure-absorbing energy bolt system” [AIP Adv. 11, 075124 (2021)

Cyclic behaviour of a novel steel beam-to-prefabricated CFST column connection with threaded sleeve bolts

As the conventional connection configurations of the steel beam to concrete-filled steel tubular (CFST) column are complex and unfriendly in practice, the application of the blind bolting system in steel beam-to-CFST column connection has been investigated in recent years. However, the blind bolted connections to CFST columns are generally classified as being pinned or semi-rigid and of partial strength due to the susceptibility to outward deformation of the tube wall. This paper developed a novel rigid and full-strength bolted connection of steel beam to prefabricated CFST column embedded with threaded sleeve bolts. Tests on five connection specimens are conducted to experimentally study the cyclic behaviour of the proposed sleeve bolted connections. The experimental parameters include the anchorage details of the sleeve bolt, the thickness of the end plate and level of axial load. To investigate the seismic performance of the proposed connections, the failure modes, hysteretic curves, connection rotation and ductility, stiffness and strength degradation, and energy dissipation capacity are presented and analyzed. The testing results prove that the proposed connection details have a strong influence on the cyclic behaviour and the moment-rotation behaviour of the novel connections. According to EC3, the proposed connection configurations behave as being rigid and of full-strength for non-sway frame. The component-based method is also proposed to predict the initial stiffness of the connections. The experimental and analytical results can provide a reference to promote the application of the novel sleeve bolted connections in engineering practice.

Experimental study on dynamic and static performance of a new type of pressure-absorbing energy bolt system

Rock burst support of deep rock mass has always been a difficult problem in geotechnical engineering. Aiming at the problem of rock burst in deep rock mass, a new type of pressure yielding and energy-absorbing bolt system is designed in this paper. The energy absorption characteristics of laminated spring members with different wall thicknesses were studied by the static axial compression test and drop hammer dynamic impact test. The experimental results show that under static axial compression, the laminated spring experiences three stages: elastic, yielding, and plastic strengthening; with the increase in the wall thickness, the energy absorbed by the laminated spring increases gradually. Under the action of impact kinetic energy, with the increase in the wall thickness and impact height, the attenuation time of pressure absorption energy increases, while the tray and nut do not change, and the bolt does not extend and bend. The ANSYS static numerical simulation analysis shows that the center of the top circle of the laminated spring component is the center, and the plastic zone radiates outward; the LS-DYNA numerical simulation shows that most of the impact kinetic energy of the drop hammer is absorbed by the laminated spring component, and the rest is small. The partial energy is borne by the bolt body. Therefore, the laminated spring component can effectively absorb the impact kinetic energy, achieve the effect of active pressure and energy absorption, and avoid the bolt being broken so as to avoid the bolt body bearing all the impact kinetic energy and damage.

Grouting Technique for Gob-Side Entry Retaining in Deep Mines

The retained rib displacement accounts for roughly 80% of rib-to-rib convergence in gob-side entry retaining in deep coal mines, which shows significant nonsymmetrical feature and long-term rheological phenomenon. Affected by mining-induced stress, cracks spread widely, and broken zones expand beyond the anchoring range. Without grouting and supplementary support in retained rib, the surrounding rock-support load-bearing structure will be in a postpeak failure state, and the anchoring force of the bolting system will be greatly attenuated. After grouting, the compressive strength of grouting geocomposite specimen is significantly higher than the postpeak residual strength of the intact coal specimen, and it is partially restored compared to that of the intact coal specimen. The ductility of the fractured coal specimen increases after grouting, and it has stronger elasticity and plasticity. Broken rock block can become a whole with coordinated bearing capacity, and its stability is improved after grouting. The grouting technique could restore the integrity and strength of the fractured retained coal rib, repair the damaged bolting structure, and make the surrounding rock and supporting structure become an effective bearing structure again. The research result shows that it is feasible to restore the bearing capacity of the retained coal rib by grouting technique.

High-strength mechanical joints under combined mechanical and medial loads

This paper introduces a test method for joined hot-dip galvanized steelwork test specimens. The specimens joined by means of a lock bolt system were subjected to a simultaneously combined mechanical and medial loading. This was achieved by combining a vibration testing machine and a condensation chamber that was expanded by an electrolyte dosing unit. The electrolyte was dosed on one side of the specimen in the area around the lock bolt head. The zinc dissolution is locally accelerated in the area around the joining element possibly due to superimposed bimetal and crevice corrosion. In addition, the electrolyte enters the space between the joined steel sheets and initiates corrosion processes there, too. Besides the expected zinc ions, potassium ions were also detected in the collected electrolyte by means of elemental analysis. These are originally part of the friction-increasing coating.

Theoretical dynamic displacement analysis for rock bolt with surrounding rock-soil body

To analyze rock-bolt dynamic mechanics, one theoretical model has been put forward based on several assumptions. At the interface of the bolt and surrounding rock-soil body, the coupling of a linear spring and a damper is used for the bolt system. The coefficient k of the spring and the damper coefficient η are key parameters between the rock-soil body and bolt. The elastic and viscoelastic kinematic equations are established, and the displacement control equations are binary second-order partial-differential equations that can be simulated by numerical methods. One example shows the displacement curves with input waves; the displacement decays with different distributions. The curves of different times were simulated, and it was found that as the ratio value of the coefficient k of the spring and elastic modulus E increases, the displacement-decay-ratio speed increases per unit length. The same is true for the ratio values of the damper coefficient η and elastic modulus E. The theoretical model can also be used to solve the impact-force problems.

Numerical study on the resistance of thread-fixed one-side bolts: Tensile and bearing strength

In steel structures, owing to technological aspects, frequently bolting access is difficult. To overcome these issues, technological research has proposed in the last decades several blind bolt systems that allow the installation of a bolt working only on one side of the connection. The simplest type of blind bolt is the thread-fixed one side bolt (TFOSBs), in which the connecting elements are fastened through threaded holes, and the connection is assured by the contact between bolt and hole threads. This type of bolting system is very easy to apply, but, currently, there are only a few design rules available.While the mechanical behaviour of TFOSBs is conceptually easy to understand, there are still some specificities that need to be accounted for and deserve specific investigations. A first aspect regards the behaviour in tension that must be characterized properly because it depends on some local effects such as the threads’ bending both bolt and hole. Similarly, regarding the behaviour in shear, due to the lack of confinement in the nut area, as already shown for similar bolt typologies, the bearing resistance may be lower compared to standard assemblies. To provide design rules for the behaviour of TFOSBs in tension and shear, in this paper, FE models and parametric studies are developed. The collected data are used to provide a prediction of the resistance of these fasteners, suggesting design rules of immediate applicability developed along the same lines of Eurocode 3 part 1.8 provisions. The results obtained suggest that, compared to standard bolt assemblies, an average reduction of 15% of the bearing resistance should be considered for the design of TFOSBs. Instead, for what regards the behaviour in tension, the shank necking failure of the bolt be achieved only by assuring minimum bolt screwing depths, which are suggested in this paper, confirming similar proposals already available in technical literature. Conversely, provided that the failure of the hole’s threads is accepted a reduction coefficient of the tensile resistance to be used in design, ranging from 0 to 1, has been proposed based on the FE studies’ results.

A component model for column face in bending of extended HolloBolt connections

Extended HolloBolt (EHB) is a practical anchored blind bolting system for concrete-filled steel sections. One of the failure modes of EHB connections is the bending of the column face component. Up to date, no analytical model to estimate the strength and stiffness of this component have been proposed. This paper aims to develop such model to capture the principal aspects of the overall behaviour of the component, such as its strength and stiffness at different key stages, to represent the component behaviour. The component strength is assumed to be provided by the steel hollow section plate bending and the anchored action. The steel hollow section plate strength models were developed based on the yield line theory. The anchored strength was considered equivalent to the load required to initiate a concrete cone failure. The component stiffness models were formulated using elastic springs, one at each bolt location. The component stiffness was taken equal to the summation of springs stiffness as they act in parallel. The overall bending behaviour of the component was represented by a quad-linear model. The stiffness of the post yield parts of the model was considered as a percentage of the initial stiffness of the component. The model was validated with the available data in the literature and they provided reliable results, which can be considered as a benchmark for the design of EHB connections. This model can be later extended and generalized for other similar blind bolts connections.

Fatigue deformation and damage characteristics of bolting system under stress-controlled cyclic pullout

This study explored the fatigue mechanical properties and acoustic emission (AE) characteristics of bolting system under cyclic pullout tests controlled by different upper stress levels. A novel compression-pull load conversion device was designed to precisely apply cyclic pullout load on bolting system. Strain gauges and AE sensors were employed to capture the surface strain variations of rock bolts and microfracture development during static and cyclic testing. The fatigue strength, deformation, axial/shear stress distributions and AE characteristics of the bolting system were comprehensively investigated. Fatigue threshold, an important value determining the service life of a bolting system, was supposed to be lower than 85% of the static strength in this study. The bolt residual slip strain curve was S-shaped and comprised three stages: the initial stage, constant-velocity stage and acceleration stage. The constant-velocity stage accounted for most of the fatigue life and was the main stage of fatigue development. The fatigue failure of the anchorage system was presumably controlled by the entire static stress–strain process, and the residual strain at fatigue failure corresponded to the peak strain at the peak stress under static loading. The anchorage fatigue damage development completely coincided with the residual strain evolution, and the turning points were identical between the different deformation stages. Based on the residual slip strain development, nonlinear inverted S-shaped cumulative fatigue damage models were proposed for different upper stress levels. A comparison of the results from different samples revealed that the damage evolution was highly dependent on the upper stress level. The fatigue life of the bolting system decreased as the upper stress level increased due to the increased steepness of the second stage and the decreased proportion of the second stage to the entire fatigue process.

Experimental and numerical investigation of crack propagation in bolting systems strengthened with resin-encapsulated rock bolts

Rock reinforcement design necessitates a clear understanding of the initiation and propagation of cracks in the bolting system. To better understand the mechanism, we performed laboratory pull-out tests on resin-encapsulated rock bolts. Numerical models on a 1:1 scale were built using the discrete element method. The microscopic parameters of the model were calibrated based on unconfined compression tests and ring shear tests. The model allows us to visualize the progressive failure of a bolting system strengthened with resin-encapsulated rock bolts and elucidates the role of the anchorage length in controlling crack propagation. Comparisons indicate that the physical and numerical results are consistent. The results show that increasing the anchorage length improves the bondability and strength of the bolting system and restrains the complete debonding of the rock bolt from the cement mortar. At the same time, it also facilitates the conversion of shear cracks to tensile cracks. However, the shear crack of the resin is the dominant effect in the bolting system. In addition, the results reveal how factors such as boundary confining pressure, resin thickness, and cement-mortar strength affect crack initiation and propagation.

Studying the performance of fully encapsulated rock bolts with modified structural elements

Numerical simulation is a useful tool in investigating the loading performance of rock bolts. The cable structural elements (cableSELs) in FLAC3D are commonly adopted to simulate rock bolts to solve geotechnical issues. In this study, the bonding performance of the interface between the rock bolt and the grout material was simulated with a two-stage shearing coupling model. Furthermore, the FISH language was used to incorporate this two-stage shear coupling model into FLAC3D to modify the current cableSELs. Comparison was performed between numerical and experimental results to confirm that the numerical approach can properly simulate the loading performance of rock bolts. Based on the modified cableSELs, the influence of the bolt diameter on the performance of rock bolts and the shear stress propagation along the interface between the bolt and the grout were studied. The simulation results indicated that the load transfer capacity of rock bolts rose with the rock bolt diameter apparently. With the bolt diameter increasing, the performance of the rock bolting system was likely to change from the ductile behaviour to the brittle behaviour. Moreover, after the rock bolt was loaded, the position where the maximum shear stress occurred was variable. Specifically, with the continuous loading, it shifted from the rock bolt loaded end to the other end.

Monitoring of corrosion-induced damage to bolted joints using an active sensing method with piezoceramic transducers

Ensuring adequate tightening of bolted joints is necessary since they are more prone to corrosion in a harsh environment under insufficient preload. To this end, this paper first conducted an accelerated electrochemical corrosion experiment to expedite the corrosion process of bolted connections over different periods. The results show that as the corrosion time is extended, the overall dimensions of the bolt system remarkably decrease. Moreover, according to the mass loss of the bolted joints in 3.5% NaCl solution, the rate of corrosion continuously changes. Then, a real-time monitoring approach based on active sensing was utilized to evaluate the corrosion conditions of bolted joints. The stress wave generated by one piezoceramic transducer propagates through the bolted joints and is captured via another transducer that acts as a sensor. The energy corresponding to the stress wave signal declines during the corrosion process, and the normalized wavelet packet energy index is used to evaluate the degree of damage to the bolted joints. Overall, the health status of the bolted joints is significantly affected by the corrosion time. The proposed active sensing method can accurately monitor the corrosion process of bolted joints. The experimental results verify the feasibility and practicality of the real-time, piezoceramic transducer-enabled method for monitoring the structural health of corroded bolted joints.

Corrosion and Chloride Diffusivity of Reinforced Concrete Cracked under Sustained Flexure

This research discusses the chloride diffusivity of concrete as well as corrosion performance of rebars in cracked and uncracked states. Prismatic concrete specimens with two water-to-cement ratios, two concrete cover thicknesses with and without steel fibers were used. Three-point flexural loading was applied to form cracks and cracks were sustained by a bolt system. Half-cell potential and corrosion rate measurements were carried out following wetting - drying cycles in chloride environment which were continued for 80 weeks. The positive effects of lower water-to-cement ratio and greater cover depth were found to be surpassed by existence of cracks in concrete.