Steel Nails Research Articles

Influence of gap size, screw configuration, and nail materials in the stability of anterograde reamed intramedullary nail in femoral transverse fractures

Femoral shaft fractures are among the most severe injuries of the skeleton. They are associated with high morbidity and mortality. The most appropriate treatment depending on the type of fracture and location level should be chosen.A finite element model of the femur has been developed, analyzing various types of fractures in the subtrochanteric and diaphyseal supracondylar area, with several gap sizes, being stabilized with a single combination of screws for the intramedullary nail. The mechanical strength of the nail against bending and compression efforts was studied comparing two materials for the nail: stainless steel and titanium alloy.Beside the finite elements (FE) simulations, a clinical follow-up was carried out, considering a sample of 55 patients, 24 males, and 31 females, with mean age of 52.5 years. Localizations of fractures were 22 in the right femur and 33 in the left one, respectively.A good agreement between clinical results and the simulated fractures in terms of gap size was found. Non-comminuted fractures have a mean consolidation time of 4.1 months, which coincides with the appropriate mobility at fracture site obtained in the FE simulations, whereas comminuted fractures have a higher mean consolidation period estimated in 7.1 months, corresponding to the excessive mobility at fracture site obtained by means of FE simulations.The obtained results between both nail materials (stainless steel and titanium alloy) show a higher mobility when using titanium nails, which produce a higher rate of strains at the fracture site, amplitude of micromotions and bigger global movements compared to stainless-steel nails. Steel nails provide stiffer osteosyntheses than the titanium nails.In conclusion, anterograde locked nail is particularly useful in the treatment of a wide range of supracondylar fractures with proximal extension into the femoral diaphysis.

Utilization of soil nailing technique to increase shear strength of cohesive soil and reduce settlement

This article deals with the assessment of the soil nailing technique with a vertical inclusion to improve the geotechnical parameters of cohesive soil. A series of unconfined compression tests and direct shear tests were carried out to establish the stress–strain relationship and strength characteristics of the reinforced clay sample by vertical steel nails. The shear strength performance of the new composite material was tested by varying the number of vertical inclusions, the embedment depth and the alignment radius. The results confirmed that the vertical bars/inclusions shared the vertical applied load with clay. Increase in the number of vertical inclusions significantly increases the shear strength and the stiffness with a remarkable reduction in settlement. When the clay samples were reinforced with six inclusions along the perimeter, the shear strength was increased to 231% for the embedment depth ratio equal to 0.85. To obtain the optimum effect in eliminating shear failure, the vertical inclusions should be extended to a deeper zone with sufficient numbers. It has been found that the vertical inclusions significantly influence the shear strength, and the brittle or general shear failure of the unreinforced sample can be diverted to partial/plastic shear failure.

Torque Penetrometric Test for the in-situ characterisation of historical mortars: fracture mechanics interpretation and experimental validation

The assessment of historical structures requires appropriate knowledge of the behaviour of the investigated materials. Concerning masonry, its mechanical characterisation is a challenging task, since its composite nature requires the careful evaluation of the behaviour of its material components. In particular, the experimental assessment of the strength of existing mortar in historical structures still encounters several difficulties. This study investigates a novel Minor Destructive Testing (MDT) technique virtually equivalent to the vane test used for soils. The instrumentation, called herein Torque Penetrometric Test (TPT), is composed of a steel nail with four protruding teeth and a torque wrench. The test consists in inserting the toothed nail into a mortar joint and then applying a torque by means of a dynamometric key, until reaching the failure of the material. This work presents a novel interpretation theory based on basic concepts of fracture mechanics and applied to the micro-mechanical analysis of the stress state induced by the instrument on the investigated mortar. The proposed interpretative theory is validated through the execution of experimental tests in the laboratory and in a historical masonry building. The test proves to be effective for a quick in-situ MDT evaluation of the strength of existing mortars.

Life Cycle Inventory Analysis of the Wood Pallet Repair Process in the United States

SummaryThis study developed gate‐to‐gate life cycle inventory (LCI) data for the repair of 48 by 40 inch (1,219 by 1,016 millimeter [mm]) stringer‐class wood pallets in the United States. Data were collected from seven wood pallet repair facilities. Approximately 1.98 FBM (foot, board measure) (4.67E‐03 cubic meters) of lumber were used for repairing each 48 by 40 inch (1,219 by 1,016 mm) stringer‐class wood pallet, the majority (97%) recovered from damaged pallets received by the pallet repair facilities. Repair equipment powered by electricity made the largest contribution to greenhouse gas (GHG) emissions. Steel nails used for the pallet repair had the largest contribution to GHG emissions among the material inputs, while use of recovered lumber yielded the largest GHG emissions credits. Overall, the repair process for a 48 by 40 inch (1,219 by 1,016 mm) stringer‐class wood pallet had GHG credits rather than a positive GHG emission due to the GHG offsets from co‐products.

Comparison study of compound fractures of tibial shaft treated by titanium and stainless steel interlocking nails

<p class="abstract"><strong>Background:</strong> <span lang="EN-IN">The purpose of the present study was to compare the outcomes of compound fractures of tibia shaft managed by Solid Titanium and Stainless Steel interlocking intramedullary nailing.</span></p><p class="abstract"><strong>Methods:</strong> <span lang="EN-IN">This is a retrospective study of 45 patients with 45 open fractures of tibia shaft operated primarily by either Solid Titanium or Stainless steel tibia interlocking nail</span>.<strong></strong></p><p class="abstract"><strong>Results:</strong> <span lang="EN-IN">In Our Study we had 45 patients with 45 open tibial fractures. All were male. 35 patients were from 20-50 years age group. Mean age was 36.4 years. In this study of 45 open tibial fractures following strict protocol of thorough debridement, primary wound closure and Solid Titanium or stainless steel interlocking nailing; it was observed at final follow up that patients operated by titanium nail compared to stainless steel had 6.45% vs. 14.29% infection rate, 12.9% vs. 21.89% rate of non-union and 3.22% vs. 7.14% screw breakage rate. According to modified ketenjian’s criteria in our study out of 31 patients operated by Titanium interlocking nail 17 (54.84%) excellent, 10 (32.26%) Good, 3(9.68%) fair and 1(3.22%) poor functional results while out of 14 patients managed by stainless steel nail 8 (57.14%) excellent, 3 (21.43%) good, 1 (7.14%) fair and 2 (14.28%) poor functional results. </span></p><p class="abstract"><strong>Conclusions:</strong> <span lang="EN-IN">In open tibial fractures titanium interlocking implants offer lower complication rate as compared to stainless steel implants and better overall patient outcome.</span></p>

Investigation of atmospheric corrosion layers on historic iron nails by micro‐Raman spectroscopy

In this study, some Ottoman low carbon steel nails from a 16th century brick masonry dome of Kiliç Ali Pasha Bath in Istanbul and from a 19th century stone dwelling in Phocaea Izmir were studied for their long term corrosion characteristics. Their corrosion layers were examined with a Senterra Bruker micro‐Raman spectrometer and Tescan Vega model Scanning Electron Microscopy (SEM) with Inca X‐Stream 2 Energy‐Dispersive X‐ray spectroscopy (EDX). Powdered samples scraped from the corrosion layers were studied by X‐ray powder diffraction and Fourier transform infrared spectroscopy. The corrosion layer consisted of two main sub‐layers, namely an ‘inner corrosion layer’ including a ‘reaction front’ and a ‘transformed medium’ which included the depositions from the surrounding media. Peak intensities of X‐ray powder diffraction traces were not proportional to the abundance of oxides and oxyhydroxides in the corrosion layer, most probably because of their partly amorphous and nano‐size nature. Inner corrosion layer and transformed medium layers were studied in detail by micro Raman spectroscopy at 532 nm, 0.2 mW, 200 s. The Protective Ability Index (PAI) of the corrosion layers were expressed as the ratio of isotropic goethite band thickness to the thickness of reaction front composed of other oxides and oxyhydroxides being magnetite, maghemite, hematite, lepidocrocite, distinguished by micro‐Raman which is a unique method for phase identification. PAI was then estimated to be ~6–10 for 16th century nails and ~3 for 19th century nails. Corrosion mechanisms and PAI were concluded to be affected by compositional characteristics of artefacts and their atmospheric conditions. Copyright © 2016 John Wiley & Sons, Ltd.

Advanced interlocking systems to improve heavy-load-bearing characteristics of flexible intramedullary nailing

Flexible intramedullary nailing (FIN) is a minimally invasive and widespread standard method for osteosynthesis of pediatric long bone fractures. In the case of unstable fractures of the lower extremity, interlocking systems need to be used to prevent axial shortening and subsequent perforation of the nail at its insertion site. In the present study, four different screw-fixed interlocking systems for FINs (Hofer TwinPlug with two 3-mm titanium interlocking screws, Hofer FixPlug with 3-mm titanium interlocking screw, Hofer Plug with 3.5-mm titanium interlocking screw, and Hofer Plug with 3-mm titanium interlocking screw) in comparison with the commonly used Ender stainless steel nails (locked with 3.5-mm screw) were experimentally investigated in cadaveric lamb tibiae, regarding their load characteristics and failure modes in the case of heavy loading. The specimens were subjected to sequential axial cyclic loading of 5000cycles with stepwise increase of the load amplitude until failure. Migration of locking screws and internal damage of bone tissue was quantified by micro-computed tomography (CT) imaging. Ender nails failed on average at a peak load of 800 N, TwinPlugs at 1367 N, FixPlugs at 1222 N, Plugs 3.5mm at 1225 N and Plugs 3.0mm at 971 N. TwinPlugs, FixPlugs, and Plugs 3.5mm failed in a slow manner over several hundred loading cycles, whereas Ender nails and Plugs 3.0mm exhibited abrupt failure without any prior indication. Our results confirm that axial stability of FIN can be further improved by screw-fixed plugs by simultaneously avoiding shortcomings of an eye-locked system, which the Ender nails are. Considering biomechanical results, plug interlocking systems with 3.5-mm screws should be favored over conventional Ender nails and plugs with 3-mm screws.

Experimental Tuna Farming in the Sultanate of Oman

Tuna are among a very large group of large and medium-oceanic fish and they are an important food source globally. They are also unusual fish because they are warm blooded fish and they need large amounts of oxygen. The fluctuations in tuna catch and price has led to focus on the farming of tuna in large floating cages in many countries, like South Australia, Turkey, Croatia, Mexico, Panama and other countries mainly for the Japanese market. In the Mediterranean they farm blue fin tuna, yellow fin tuna and big-eye are farmed in Mexico and the yellow fin tuna have been farmed on a pilot scale in the Sultanate of Oman by cage Culture Company. To farm tuna several stages have to be practiced, starting from preparation of cages, fishing, transferring of the live fish to the towing cages and to the farming site, feeding, harvesting, processing, packaging and exportation. In Oman, two types of cages were used in this process, towing cages and fattening cages, and with nets of 30meters depth, fixed on cages of 48meters diameter. Fishing was practiced using Purse-Seineships in areas around 50-70 kilometers away from the farming sites, nets were kept open to avoid killing of fish, which transferred under water to the towing cages then to the fattening cages. The speed of ship didn’t exceed 4 nots/hour through the whole journey. Tuna arrives to the farming site in a state of stress and seize eating for up to 3 weeks even if an attempt is made to feed them. After this period, tuna start feeding greedily large quantities of food with high oils content such as Sardine. When caught fish weight ranges from 25-40 KG, and there is no need to gain more weight but to increase the percentage of fat. In the Sultanate we used sardines, as the Omani sardine is characterized by high oil content. Feeding was distributed manually to the cage until the tuna stop eating. The fish lose about 20% of its weight during transportation and fasting stage, then compensate the loss and increase the percentage of oil in the flesh. Generally the universal calculated food conversion ratio is 1-20 as the fresh fish used in feeding has high proportion of water. Harvesting process is a delicate process and should be organized well and requires accuracy and speed at work, relies on the use special collection net to collects almost the required number and detain it in the cage. Professional divers have to dive and swim with a hold of fish. The caught tuna then lifted from the waterslide on the smooth floating portion to reduce friction with the fish’s body. Followed by quick killing of fish by putting steel nail in the brains of the fish to reduce stress and avoid burning of the meat. The second step is the insert of steel wire in the spinal cord after cutting the head using an electrics a win order to ensure the full death of the fish. Fish are then placed in ice water to ensure cooling of the meat and quality; the last stage is to transfer the fish to the factory for processing and exportation. Normally harvesting should not take more than 2-3 minutes to keep the meet to the highest quality or Shesimi grade for the Japanese market. Dealing with farmed tuna inside the processing plant should be in a way that maintains fish quality and maintain me at temperature internally and externally and determine the quality of meat in terms of the percentage of the fats in fish flesh.

Biomechanical performance of retrograde nail for supracondylar fractures stabilization.

The study compared the biomechanical performance of retrograde nail used to stabilize supracondylar fracture (three different levels) by means of finite element analysis. Three different nail lengths (200, 260, and 300mm) of stainless steel and titanium nails were under consideration. Intact femur model was reconstructed from Digital Imaging and Communications in Medicine images of Thai cadaveric femur scanned by computed tomography spiral scanner, whereas geometry of retrograde nail was reconstructed with the data obtained from three-dimensional laser scanner. The retrograde nail was virtually attached to the femur before nodes and elements were generated for finite element model. The finite element models were analyzed in two stages, the early stage of fracture healing and the stage after fracture healing. The finding indicated that purchasing proximal locking screw in the bowing region of the femur may be at risk due to the high stresses at the implant and bone. There were no differences in stress level, elastic strain at a fracture gap, and bone stress between stainless steel and titanium implant. Since the intramedullary canal requires reaming to accommodate the retrograde nail, the length of retrograde nail should be as long as necessary. However, in case that the retrograde nail can be accommodated into the intramedullary canal without reaming, the longer retrograde nail can be used.

Load-slip behaviour of steel-cross laminated timber (CLT) composite connections

Connecting cross laminated timber (CLT) panels to steel girders using mechanical connectors (e.g. screws and bolts) is an attractive and novel method for developing a fully prefabricated and sustainable hybrid steel-timber composite (STC) floor that can also facilitate future dismantling and recycling of its structural components. Since the structural performance of composite floors (including STC systems) is significantly influenced by strength and stiffness of slab-to-girder composite joints, this study characterises the load-slip behaviour and failure modes of steel-CLT timber composite joints by conducting push-out tests on three different types of STC connections with high-strength bolts, coach screws or a combination of glue and coach screws. Furthermore, the effect of reinforcing the CLT slabs by using steel nail plates on the strength and stiffness of STC joints is evaluated. Empirical models for capturing load-slip behaviour of steel-CLT composite joints with dowel (i.e. screw and bolt) connectors are derived from non-linear regression of experimental data and simple formulae for the strength and stiffness of steel-CLT composite joints with dowel connectors are proposed. Moreover, 1D beam on inelastic foundation finite element (FE) models of the dowel STC connectors are developed and validated against experimental results.

Treatment of pediatric femoral shaft fractures by stainless steel and titanium elastic nail system: A randomized comparative trial

PurposeLiterature suggests that the lower modulus of elasticity of titanium makes it ideal for use in children compared with stainless steel. Better fracture stability was observed in association with titanium nails on torsional and axial compression testing. However, stainless steel nails are stiffer than titanium counterparts, which may provide a rigid construct when fixing paediatric femoral shaft fractures. Complications have been observed more frequently by various researchers when titanium nails are used for fracture fixation in patients with increasing age or weight. The concept of this study was to compare the functional outcome after internal fixation with titanium elastic nail system and stainless steel elastic nail system in paediatric femoral shaft fractures. MethodsThe study was conducted on 34 patients admitted in the department of orthopaedics, LLRM Medical College & SVBP Hospital, Meerut, India from January 2013 to August 2014. We included patients aged 5–12 years with fracture of the femoral shaft, excluding compound fractures, pathological fractures and other lower limb fractures. Patients were treated by titanium (n = 17) or stainless steel (n = 17) elastic nail system and followed up for one year. The clinical parameters like range of motion at hip and knee joints, time to full weight bearing on the operated limb and radiological parameters like time to union were compared between two groups. A special note was made of intra- and post-operative complications. Functional outcomes were analysed according to Flynn criteria. ResultsBased on the Flynn criteria, 59% of patients had excellent results, 41% had satisfactory results, and no one showed poor results. There was no clinically significant difference between the two groups with respect to time to union and full weight bearing. But the incidence of puncture of the opposite cortex while inserting the nail and trying to advance it through the diaphysis during operation is greatly different. Only one such case was observed in titanium group but five in stainless steel group. ConclusionMajority of paediatric femoral shaft fractures are now treated operatively by elastic stable intramedullary nails. Operative intervention results in a shorter hospital stay and has economic and social benefits over conservative treatment. The cost of stainless steel nail is one third the cost of titanium nail. However, the clinico-radiological results are not significantly different between titanium and stainless steel nails at one year follow-up as observed by our study.

Pelvic pressure changes after a fracture: A pilot cadaveric study assessing the effect of pelvic binders and limb bandaging

Pelvic pressure changes after a fracture: A pilot cadaveric study assessing the effect of pelvic binders and limb bandaging

Are stainless steel elastic nails the solution to heavier children with femoral shaft fractures?

Background: The use of titanium elastic intramedullary nails for the treatment of femoral shaft fractures, in children weighing 45 kg, has been questioned due to the increased rates of malunion. Our aim was to see if the mechanical properties of stainless steel elastic nails provided enough fracture stability to justify their use in heavier children. Materials and Methods: Twenty pediatric femoral Sawbones®, fixed with titanium or stainless steel elastic nails, were tested. The bending stiffness and moments of the constructs were calculated at increasing loads, along with the angle of fracture deformation. From these estimates of maximum permitted body weight for each nail type were extrapolated. Results: Steel nails created significantly stiffer constructs than titanium in both the coronal and sagittal planes (P < 0.0001). Steel nails allowed bigger sagittal bending moments before losing acceptable alignment, compared to titanium (P < 0.0001). However, in the coronal plane, the difference was not statistically significant (P = 0.457). The estimated body weights extrapolated in the sagittal plane were 45 and 61 kg, in titanium and steel, respectively. In the coronal plane, they were 42 and 44 kg. Discussion: As steel has nearly twice the Young's modulus of titanium, it seems logical that fractures fixed with steel nails would be stiffer and fail at higher loads. However, it is unclear why steel did not outperform titanium in the coronal plane. A theory was proposed that unequal nail slip from the insertion sites might be a contributing factor to these findings. Conclusion: Pediatric femoral shaft fractures fixed with elastic steel nails provide significantly stiffer constructs than those fixed with titanium. However, there is an increased risk of malunion in the coronal plane, in children weighing 45 kg, regardless of material used, possibly due to unequal nail slip at the distal entry points.

BLANQUEAMIENTO CORALINO DE 1990 EN EL PARQUE NACIONAL NATURAL CORALES DEL ROSARIO (CARIBE, COLOMBIANO

At the beginning of June 1990 a coral-bleaching event was detected in the Islas del Rosario reefs, Colombian Caribbean. A preliminary survey of the Isla Grande northern barrier, and of the Caño Ratón and Isla Pavitos south reefs slopes resulted in a list of 19 affected species, which includes scleractinians, zoantideans and milleporins. Bleached colonies accounted for less than 10% of the total observed. The species most affected were Montastrea annularis and Porites astreoides. The recovery process was followed during a five month period in 20 Montastrea annularis, 3 Acropora palmata and 3 Acropora cervicornis colonies . The bleached patches (injuries) of each colony were meassured, demarked with steel nails and their evolution monitored at monthly intervals. Total mortality was observed in 52% of the injures, incomplete recovery in 40%, and no apparent change in the remaining 8% of the colonies. The coral- bleaching event was coincident with an unusual rise in water temperature (31°C to 32°C) between May and June 1990. As the high temperatures lasted until October of the same year (&gt;30°C), these arÿpressumed to be the main cause of the bleaching phenomenon. The possible role of light as a concomitant factor is-also discussed.

Sensitivity and adaptability of methanogens to perchlorates: Implications for life on Mars

In 2008, the Mars Phoenix Lander discovered perchlorate at its landing site, and in 2012, the Curiosity rover confirmed the presence of perchlorate on Mars. The research reported here was designed to determine if certain methanogens could grow in the presence of three different perchlorate salt solutions. The methanogens tested were Methanothermobacter wolfeii, Methanosarcina barkeri, Methanobacterium formicicum and Methanococcus maripaludis. Media were prepared containing 0%, 0.5%, 1.0%, 2%, 5% and 10% wt/vol magnesium perchlorate, sodium perchlorate, or calcium perchlorate. Organisms were inoculated into their respective media followed by incubation at each organism׳s growth temperature. Methane production, commonly used to measure methanogen growth, was measured by gas chromatography of headspace gas samples. Methane concentrations varied with species and perchlorate salt tested. However, all four methanogens produced substantial levels of methane in the presence of up to 1.0% perchlorate, but not higher. The standard procedure for growing methanogens typically includes sodium sulfide, a reducing agent, to reduce residual molecular oxygen. However, the sodium sulfide may have been reducing the perchlorate, thus allowing for growth of the methanogens. To investigate this possibility, experiments were conducted where stainless steel nails were used instead of sodium sulfide as the reducing agent. Prior to the addition of perchlorate and inoculation, the nails were removed from the liquid medium. Just as in the prior experiments, the methanogens produced methane at comparable levels to those seen with sodium sulfide as the reductant, indicating that sodium sulfide did not reduce the perchlorate to any significant extent. Additionally, cells metabolizing in 1% perchlorate were transferred to 2%, cells metabolizing in 2% were transferred to 5%, and finally cells metabolizing in 5% were transferred to 10%. All four species produced methane at 2% and 5%, but not 10% indicating some success in adapting cells to concentrations higher than 1%. The results reported here indicate that the presence of perchlorate on Mars does not rule out the possible existence of methanogens.

Control of the micromovements of a composite-material nail design: A finite element analysis

BackgroundIntramedullary nail fixation is the most accepted modality for stabilizing long bone midshaft fractures. The commercially used nails are fabricated from Stainless Steel or Titanium. Composite-materials (CM) mainly carbon-fiber reinforced polymers (CFRP) have been gaining more interest and popularity due to their properties, such as modulus of elasticity close to that of bone, increased fatigue strength, and radio-opacity to irradiation that permits a better visualization of the healing process. The use of CFRP instead of metals allows better control of different directional movements along a fracture site. The purpose of this analysis was to design a CM intramedullary nail to enable micromovements as depicted on a finite element analysis method. MethodsWe designed a three-dimentional femoral nail model. Three CFRP with different laminates arrangements, were included in the analysis. The finite element analysis involved applying vertical and horizontal loads on each of the designed and tested nails. ResultsThe nails permitted a transverse micromovement of 0.75mm for the 45° lay-up and 1.5mm for the 90° lay-up for the CM, 1.38mm for the Titanium and 0.74mm for the Stainless Steel nails. The recorded axial movements were 0.53mm for the 45° lay-up, 0.87mm for the 90° lay-up, 0.46mm for the unsymmetrical lay-up CM, 0.046 for the Titanium and 0.02 for the Stainless Steel nails. Overall, the simulations showed that nail transverse micromovements can be reduced by using 45° carbon fiber orientations. Similar results were observed with each metal nails. InterpretationWe found that nail micromovements can be controlled by changing the directional stiffness using different lay-up orientations. These results can be useful for predicting nail micromovements under specified loading conditions which are crucial for stimulating callus formation in the early stages of healing.

On the delamination phenomenon in the repair of timber beams with steel plates

This paper presents a non-invasive technique for the repair of ancient wooden floors. Steel plates are glued on one side only by epoxy-adhesive into longitudinal grooves in order to allow the free swelling and shrinkage of the wood in the direction transversal to the plate glueing surface, thus reducing the risk of plate delamination. A set of high strength steel nails provides load transmission from the steel plates to the wooden beam in the case of loss of adhesion due to fire or delamination. This technique was used to repair a precious beam in a 15th-century wooden floor in Palazzo Calini (Brescia, Italy). The technique requires particular attention because it might be affected by the delamination of the glued reinforcement due to stress concentration, which occurs at the end of the repairing element or at any cracks in the repaired beam. Results of experimental studies on delamination phenomenon investigated by means of the Moiré interferometry analysis are also presented. These show that the risk of plate debonding can be markedly reduced by the capability of the sapwood to develop plastic strain. The wooden floor has been monitored for more than fourteen years, confirming the effectiveness of the adopted technique.

Investigating the effect of nailed sleepers on increasing the lateral resistance of ballasted track

Up to now, various techniques such as using dual-block sleeper, frictional sleeper, safety cap installation, Xitrack utilization and so forth have been proposed in order to improve the lateral resistance of ballasted railway tracks. In all existing methods, no engagement has been considered for track subgrade in this regard. In this paper, benefiting from the steel-driven nails, a new technique called “nailed sleeper” is introduced for enhancing the lateral resistance of concrete sleepers. In this regard, a 3D numerical model of ballasted track with single tie (sleeper) was developed using ABAQUS software and it was validated using laboratory single tie (sleeper) push test (STPT) results. Thereafter, by inserting two steel nails in the concrete tie of the model, some sensitivity analyses were conducted on the effective parameters of nails such as length, diameter, location through the sleeper and the elasticity modulus of the subgrade. In the next stage, from a structural point of view, the effect of the nail presence on the flexural and shear behavior of B70 concrete sleeper was controlled based on Australian design code AS 1085.14 requirements. As a result of the numerical and analytical analyses, the most appropriate dimensions and locations of nails were defined. Finally, after constructing a nailed B70 sleeper and installing it in a test track, its lateral resistance was evaluated under cyclic loading, and the obtained results were compared with common B70 sleeper at the same track. Consequently, it was observed that using a pair of nails of 40mm in diameter and 1500mm in length can increase the lateral resistance more than 200% compared to the normal condition. This technique can be efficiently used for horizontal anchoring the curved ballasted railway tracks.

Improving stability of elastic stable intramedullary nailing in a transverse midshaft femur fracture model: biomechanical analysis of using end caps or a third nail.

BackgroundElastic stable intramedullary nailing (ESIN) is accepted widely for treatment of diaphyseal femur fractures in children. However, complication rates of 10 to 50 % are described due to shortening or axial deviation, especially in older or heavier children. Biomechanical in vitro testing was performed to determine whether two modified osteosyntheses with end caps or a third nail could significantly improve the stability in comparison to classical elastic stable intramedullary nailing in a transverse femur fracture model.MethodsWe performed biomechanical testing in 24 synthetic adolescent femoral bone models (Sawbones®) with a transverse midshaft (diaphyseal) fracture. First, in all models, two nails were inserted in a C-shaped manner (2 × 3.5 mm steel nails, prebent), then eight osteosyntheses were modified by using end caps and another eight by adding a third nail from the antero-lateral (2.5-mm steel, not prebent). Testing was performed in four-point bending, torsion, and shifting under physiological 9° compression.ResultsThe third nail from the lateral showed a significant positive influence on the stiffness in all four-point bendings as well as in internal rotation comparing to the classical 2C configuration: mean values were significantly higher anterior-posterior (1.04 vs. 0.52 Nm/mm, p < 0.001), posterior-anterior (0.85 vs. 0.43 Nm/mm, p < 0.001), lateral-medial (1.26 vs. 0.70 Nm/mm, p < 0.001), and medial-lateral (1.16 vs. 0.76 Nm/mm, p < 0.001) and during internal rotation (0.16 vs. 0.11 Nm/°, p < 0.001). The modification with end caps did not improve the stiffness in any direction.ConclusionsThe configuration with a third nail provided a significantly higher stiffness than the classical 2C configuration as well as the modification with end caps in this biomechanical model. This supports the ongoing transfer of the additional third nail into clinical practice to reduce the axial deviation occurring in clinical practice.

Dowel Type Joints of Round Timber Exposed to Static and Cyclic Tension Forces

Timber constructions made of round timber are becoming increasingly popular nowadays. They concern both non-pedestrian and pedestrian bridges, watchtowers and playground equipment. If these constructions are designed with a truss supporting system, the element joints are often made of bolts with slotted-in steel plates. Joints in round timber do not have sufficient support in existing Eurocodes. The problem is also in the characterization of cyclically loaded round timber joints (fatigue loading in wood). The aim of this paper is to present the results of static and dynamic tensile tests of round timber bolted joints with slotted – in steel plates along the grains. Some of these round timber joints samples were reinforced in the timber part (near the bolt) with different components (screws, special washers, steel bands, performed steel plates and nails). The main reason of the reinforcing of the joints was to increase the carrying capacity and safety of these joints in tension. Based on the results of static and dynamic round timber bolted joints tests, reinforcement of the bolted joints significantly increased joint carrying capacity and reliability.