Cyclic Axial Loading Research Articles

Influence of screw head diameter on ex vivo fixation of equine lateral condylar fractures with 5.5 mm cortical screws.

To determine the influence of screw head diameter on equine condylar fracture fixation with 5.5 mm cortical screws. Ex vivo, biomechanical study, blinded, matched-pair design. Fifteen pairs of equine third metacarpal (MC3) bones. Lateral condylar fractures were simulated by parasagittal osteotomies and repaired pairwise by 2 × 5.5 mm cortical screws of 8 mm (standard) or 10 mm (modified) head diameter. Interfragmentary compression at maximum screw insertion torque was measured. The instrumented specimens were pairwise stratified for biomechanical testing under the following modalities (n=5): (1) screw insertion torque to failure, (2) quasi-static axial load to failure, and (3) cyclic axial load to 2 mm displacement followed by failure. Tests (1) and (2) were analyzed for yield, maximum, and failure torque/angle and load/displacement, respectively. Number of cycles to 2 mm displacement and failure was assessed from test (3). Maximum insertion torque was greater, and failure angle smaller, when constructs repaired with modified screws were tested (8.1 ± 0.5 vs. 7.4 ± 0.5Nm; P=.0047 and 550 ± 104 vs. 1130 ± 230; P=.008). Axial yield (7118 ± 707 vs. 5740 ± 2267 N; P=.043) and failure load (12 347 ± 3359 vs. 8695 ± 2277 N; P=.043) were greater for specimens repaired with modified screws. No difference was detected between constructs in the number of cycles to 2 mm displacement. Condylar MC3 osteotomies repaired with modified 5.5 mm cortical screws sustained greater maximal hand torque insertion, smaller insertion failure angle and 1.4 fold greater quasi-static failure forces than constructs repaired with standard 5.5 mm screws. Use of modified screws with larger heads may improve the fixation of condylar fractures in horses. These results provide evidence to justify clinical evaluation in horses undergoing fracture repair.

Supination Adduction Vertical Medial Malleolar Fracture Fixation with Buttress Plating vs a Novel Screw-Only Construct: A Cadaveric Biomechanical Study.

Supination adduction ankle fractures are unique among rotational ankle fractures as plate constructs are more commonly used than independent screws for medial malleolar fixation. The purpose of this study was to compare fracture displacement between plate fixation to a novel screw-only construct using a cadaveric biomechanical early-weightbearing model for the treatment of vertical medial malleolus fractures. Six nonosteoporotic fresh-frozen cadaver shanks and feet in matched pairs underwent a vertical osteotomy of the medial malleolus to simulate the supination adduction type injury. Osteoporosis was measured using DEXA scans. One specimen from each pair was fixed with a one-third tubular buttress plate and the other with screw-only fixation. The specimens were then axially loaded for 100 000 cycles to simulate protected weightbearing, and subsequently loaded to failure in supination. Stiffness, fracture displacement, and load to failure were recorded. Statistical significance was set at P <.05. There were no measurable differences in displacement between the 2 constructs during axial cyclic loading after 100 000 cycles (plate, 0.74 ± 0.09 mm; screws, 0.79 ± 0.18 mm; P = .225). During supination and axial load to failure, the plate outperformed the screw construct. For load to failure (2 mm displacement) at the fracture site, the plate group failed at 716 ± 240 N, whereas the screw group failed at 567 ± 237 N (P = .015). During load to catastrophic failure, the plate group outperformed the screw group (plate, 6011 ± 1646 N; screws, 4578 ± 1837 N; P = .002). For vertical medial malleolar fractures, the screw-only construct demonstrated no statistical difference when compared to buttress plating for cyclical axial loading, simulating early weightbearing in a boot. However, buttress plating is 21% to 24% stronger than the screw-only fixation construct in overall strength and prevention of catastrophic failure when loading in a supinated position. The screw-only construct is biomechanically similar to a buttress plate when simulating early protected weightbearing. This suggests that early weightbearing as tolerated in a controlled ankle motion boot beginning 2 weeks postoperatively is mechanically safe for this fracture pattern and does not result in unacceptable amounts of fracture displacement. This construct may be useful as a less invasive treatment modality for the treatment of vertical medial malleolus fractures in select patients.

Medial Locking Plate Can Increase the Fixation Stability of Vertical Femoral Neck Fracture in Young Adults?

Vertical femoral neck fractures in young adults are usually caused by a high-energy trauma. These injuries are difficult to stabilize due to significant shear forces acting on the fracture site. Their treatment is challenging and has a high risk of complications, such as fixation failure, malunion, nonunion and avascular necrosis of the femoral head. In recent years, several studies have focused on the use of direct reduction of vertical femoral neck fractures in young adult patients. This technique allows for anatomical reduction as well as the placement of an intra-articular implant to avoid shear forces at the fracture site. The aim of this study was to evaluate, based on in vitro experimental tests, the biomechanical stability provided by three different fixation methods: (i) dynamic hip screw with derotation screw, (ii) cannulated screws with a conventional medial bone plate and (iii) cannulated screws with a locked medial bone plate. For the biomechanical tests, these techniques were applied to reduce the vertical osteotomy performed on synthetic bones for later verification of the mechanical behavior under axial cyclic loading and destructive axial loading. There were no statistical differences in stiffness, micromovement displacement and mechanical strength during the biomechanical comparison of the fixation methods. Therefore, we conclude that the use of a conventional medial bone plate associated with cannulated screws, with a transverse trochanteric screw, supports the mechanical demand while the fracture is healing and this option can be used to stabilize vertical femoral neck fractures in young patients.

Field investigation into the performance of pipe pile in soft clay under static and cyclic axial loads

We performed a field investigation into the effective stress, the shaft friction at the pile–soil interface, and the pile-end base resistance of a 29.5 m long prestressed concrete pipe pile in soft clay under static and cyclic loadings (50 000 cycles). Our results indicate that under low-level cyclic loading (CLR ≤ 0.2, where CLR is the ratio of cyclic load amplitude to the ultimate capacity), the pore water pressure at the pile–soil interface initially accumulates with the number of cycles, followed by gradual dissipation after reaching its maximum value. The effective stress also initially decreases and then increases. The shaft friction increases after cyclic loading. Owing to axial load redistribution, the base resistance decreases with the number of cycles. When the pile is subjected to high-level cyclic loading (CLR ≥ 0.5), the pore water pressure at the pile–soil interface keeps accumulating while the effective stress continues to decrease, leading to the degradation of shaft friction. The base resistance increases as a result of axial load redistribution. In particular, we analyzed the effects of the static load level and the cyclic load level on the changes shaft friction.

Effects of the clearance between the core plate and restraining part on the structural performance of the buckling‐restrained brace using steel mortar planks

AbstractThe clearance between the core plate and the restraining part of the buckling‐restrained brace using steel mortar planks (BRBSM) considerably affects the failure mode and hysteretic characteristics of the brace. A clearance adjustment construction is proposed for the BRBSM which can control the clearance through partially pasting clearance adjustment materials and polishing the mortar plank surface. First, the clearance adjustment construction workflow and quality control are demonstrated, and it is verified that the clearance can be assured by fabricating specimens. Further, the effects of the difference in clearance between the core plate and restraining part on the structural performance of the BRBSM in terms of failure behaviour, increase strength ratio, buckling mode and cumulative plastic strain energy ratio are evaluated by conducting a cyclic axial loading test.

On the interaction of axial and bending loads in the weld root fatigue strength assessment of load-carrying cruciform joints

Current design standards and recommendations incorporate the nominal stress system for assessing the fatigue strength capacity of load-carrying cruciform (LCX) joints with the fillet welds and failing from the weld root. Thus far, bending-loaded joints have not been addressed in these standards. The aim of the present study is to investigate the fatigue performance of LCX joints subjected to cyclic axial and bending loads. Firstly, fatigue test data sets of such joints subjected to axial loading and bending loads in the adjoined plate component are extracted from the literature, and statistical analyses are carried out to evaluate the fatigue strength capacity using the nominal weld stresses (NWSs). Secondly, experimental fatigue tests are carried out on LCX joints made of ultra-high-strength steel (UHSS) grade using constant amplitude loading and subjected to combined axial and bending load to study the load interaction effects on the fatigue strength capacity. The results showed that the FAT36 detail category for the weld root failures is applicable for bending-loaded joints when applying NWSs calculated on the basis of effective throat thickness of weld and assuming linear-elastic stress distribution over the joint section. The effective notch stress analyses showed unconservative results for the tested joints, when applying FAT225 design curve with the reference radius of rref = 1.0 mm.

Peritalar Kinematics Restored with Combined Subtalar Fusion and Medial Ligament Reconstruction in a Simulated Advance Progressive Collapsing Flatfoot Deformity Model

Category:Midfoot/Forefoot; OtherIntroduction/Purpose:Progressive collapsing flatfoot deformity (PCFD) leads to a disruption of the medial peritalar ligaments with progressive loss of the medial arch and further valgus alignment of the subtalar and tibiotalar joints. This ultimately leads to peritalar instability with subtalar and tibiotalar osteoarthritis. Conventional joint sparing reconstruction methods alone may not correct the valgus heel alignment. Some have suggested subtalar fusion (SF) with or without combined medializing calcaneal osteotomy (MCO) as an option. Although SF provides a more effective correction of hindfoot alignment, a resultant increase in valgus moment arm with a larger strain on the medial ankle ligament has been reported. The study aim is to investigate the efficacy of a combined MCO with SF and medial tibionavicular ligament (TNL) reconstruction on restoring peritalar stability.Methods:Ten fresh-frozen cadaveric foot specimens were employed to create a severe PCFD model. Reflective markers were placed on the tibia, talus, navicular, calcaneus, and first metatarsal. A multiple-camera motion capture system (OptiTrack, Prime13) was utilized to document peritalar joint kinematics. Severe AAFD model was created by sectioning the medial capsuloligamentous complex followed by cyclic axial loading. Sequential surgical procedures were performed, including MCO, SF, MCO + SF, and MCO + SF + medial tibionavicular ligament (TNL) reconstruction. Subtalar joint coronal angle, tibiotalar coronal angle, forefoot abduction axial angle, and talo-first metatarsus (Meary's) lateral angle were calculated for each sequential procedure and compared to the severe flatfoot model. The kinematic changes were calculated between groups utilizing a custom MatLab code and statistical significance was determined using a one-way ANOVA and a Tukey's multiple comparison test.Results:The subtalar joint valgus angle of the severe PCFD model (mean 8.1°) was significantly reduced by the MCO+SF+TNL reconstruction (mean 3.2°, p = 0.019). The tibiotalar joint valgus angle of the severe flatfoot model (mean 4.4°) was significantly reduced by the MCO (mean 1.0°, p = 0.04), but increased after combined MCO with SF (mean 2.5°, p = 0.01). The increased valgus tibiotalar angle of the MCO+SF was reduced by adding TNL reconstruction (mean 0.75°, p = 0.027). Forefoot abduction angle was found to be significantly reduced in all reconstruction methods compared to the severe flatfoot model. Meary's angle was also significantly improved after the MCO+SF and MCO+SF+TNL reconstruction (P= 0.015 and 0.006, respectively).Conclusion:Although addition of SF to MCO improved forefoot abduction and Meary's angles of advanced PCFD model, it resulted in increased tibiotalar valgus angle. The subsequent increase in medial ligament strain may be reduced by adding TNL reconstruction which can support medial stability while improve kinematics in all planes. Addition of TNL may be considered when performing SF for correction of PCFD, especially when a residual valgus heel alignment remains.

Mechanical Properties of Soft Rocks Subjected to Water‐Rock Reaction and Cyclic Pressure

Studying the mechanical properties of soft rocks subjected to water and cyclic loading would contribute to a better understanding of the stability analysis of soft rock engineering under the conditions of storm and carrier dynamics. In this paper, two soft rocks from Southwest China (i.e., muddy siltstone and silty mudstone) were selected as test samples. Uniaxial compressive tests were applied to investigate the strength and deformation characteristics under water‐rock reactions. Meanwhile, triaxial tests were carried out to analyse the fatigue damage and failure characteristics by applying cyclic axial loading under different confining pressures. The results indicated a reduction in the uniaxial compressive strength (UCS) under saturated conditions, which is correlated with the disintegration resistance of soft rocks. Moreover, the samples exhibited a softening phenomenon due to water absorption and rock expansion, decreasing the elastic modulus. The triaxial tests demonstrated that axial strain accumulated with the number of loading cycles due to fatigue and even failed when applying increased cyclic loading with certain cycles. The cohesion decreased during cyclic loading, but the friction angle was relatively independent of the number of cycles. In addition, reductions in the dynamic elastic modulus and shear modulus decreased with increasing loading time. This study indicated that water and cyclic loadings could cause significant degradation of the strength and stiffness of soft rocks, which need to be considered carefully during the engineering utilization of such materials.

Low-cycle fatigue life prediction assessment of notched aluminum 2024-T3 under cyclic axial loading

ABSTRACT This paper investigates the fatigue behavior of notched 2024-T3 aluminum alloy under axial cyclic loading considering the combination of initiation and propagation phases. Several models based on the critical plane concept are used to predict the fatigue life in the initiation phase. A new method is presented to predict the initial crack length of the hole-type notch and edge-cut type notch specimens. Comparison of the experimental and estimated fatigue lives revealed that there is an acceptable agreement between these two results in the low-cycle fatigue life ranges.

Crack paths in multiaxial fatigue of C45 steel specimens and correlation of lifetime with the thermal energy dissipation

The work reports the observed fatigue damage of C45 steel specimens tested in a previous work under multiaxial loading conditions and its relationship with the thermal energy dissipation which has been used in the last decades to estimate the uniaxial fatigue behavior of metals. For this purpose, fatigue data relevant to thin-walled samples made of quenched and tempered C45 steel tested under completely reversed combined axial and torsional cyclic loadings with different biaxiality ratios and phase-shift angles have been analysed. The analyses of crack paths at the initiation point of failure were performed after a 50% stiffness loss that corresponded to a crack size ranging from 7 to 15 mm; afterwards, the characteristic crack paths of each loading condition were analysed by using a digital microscope to identify the orientation of the crack initiation plane. After having broken all fatigue tested specimens under static tensile loading, the fracture surfaces were inspected close to the crack initiation point using a digital microscope. Despite the stress states and fatigue damage mechanisms dependent on the load condition, the Q parameter applied to the present experimental results proved to correlate all multiaxial fatigue test results in a single fatigue scatter band.

Improved description of low-cycle fatigue behaviour of 316L steel under axial, torsional and combined loading using plastic J-integral

Low-cycle fatigue behaviour and fatigue crack kinetics of the 316L austenitic stainless steel were studied under cyclic axial, torsional and in-phase combined loading using hollow cylindrical (tubular) specimens with a small hole for crack initiation. The concept of plastic.J-integral was used, which was shown in previous studies to unify the crack growth rate data for several different materials. Dependencies of Jp on crack length were determined by extensive finite element modelling considering non-linear material behaviour according to the cyclic stress–strain curve. Locally deflected cracks were modelled in accordance with amplitudes of the axial and torsional components of combined loading. The measured crack growth rate diagrams for all types of loading and for various loading amplitudes were unified using amplitude of Jp. Fatigue lives under torsional loading were much longer than under axial loading for the same equivalent plastic strain amplitude, which was explained by higher crack driving forces in terms of Jp under axial loading than under torsional loading. Fatigue lives estimated by crack propagation based on a master curve in terms of Jp,a were in a good agreement with those obtained experimentally under all types of loading. The used concept can reduce the experimental program to obtaining of material data only for axial loading, which can then be used for prediction of behaviour under in-phase multiaxial loading. The von Mises formula for multiaxial low-cycle fatigue loading εeq,p2 = εp2 + γp2 / 3 was modified so that the fatigue lives under axial, torsional and combined loading were characterized in a matching way. Using the formula εp,Nf2 = εp2 + γp2 / 25, the fatigue life data fell on a single Coffin-Manson curve.

Development of a hysteretic model for steel members under cyclic axial loading

Steel members present complex nonlinear behaviors due to the asymmetry of the seismic responses of steel members in tension and compression. This research proposed a hysteretic model for predicting the nonlinear behaviors of hot-rolled steel members under cyclic axial loading. The proposed hysteretic model overcomes the notable limitations of the existing hysteretic model and presents considerable advantages. There are a set of linear segments involved in the proposed hysteretic model and each segment is explicitly defined. The recommended values for the empirical parameters included in the proposed hysteretic model are determined through an optimization analysis based on the genetic algorithm. Compared with the available results of the steel members tested previously by other investigators, the proposed hysteretic model is found to be able to accurately predict the hysteretic curves, peak axial resistances and hysteretic energy dissipations of the steel members. The result comparisons indicate that the proposed hysteretic model realistically presents the complex physical behaviors of members including buckling effects in compression, pinching effects in tension reloading excursion, degradation of post-buckling strength, and degradations of subsequent buckling strength. It is also found that the proposed hysteretic model with the parameters properly selected can successfully replicate the hysteretic responses of the steel members tested previously in spite of their differences in cross-sectional shapes, slenderness ratios and end boundary conditions. Moreover, the genetic algorithm enables to identify the approximate parameters included in the mathematical expressions of the proposed hysteretic model with little computational effort.

Seismic behavior and damage assessment of concrete‐filled steel tube columns in diagrid structures

SummaryDiagrid structures have become an innovative and attractive choice for high‐rise buildings due to their high rigidity and esthetic appearance. Inclined concrete‐filled steel tube (CFST) columns, as the main load‐carrying members of diagrid structures, are supposed to be subjected to axial tension and compression loads. However, few studies have investigated the seismic behavior and damage assessment of CFST columns under axial cyclic loading. This study presents experimental results for eight circular CFST columns under axial cyclic loading. Based on the observed damage evolution, a damage assessment model for CFST columns subjected to axial cyclic loading was developed using a nonlinear combination of stiffness degradation and hysteretic energy dissipation. The contributions of the maximum response and cyclic loading effects to the damage were specified by introducing combination coefficients, which can be determined from a proposed equation based on the aspect ratio and confinement index of the CFST columns. Finally, the corresponding relationships between the range of the damage index and the degree of damage of CFST columns under different performance levels were established, which can provide the necessary basis for economic loss assessment and repair of earthquake‐damaged diagrid structures.

A novel seawater and sea sand concrete-filled FRP-carbon steel composite tube column: Cyclic axial compression behaviour and modelling

This paper presents an experimental investigation of a novel seawater and sea sand concrete (SSC)-filled fibre-reinforced polymer (FRP)-carbon steel composite tube column (SFSCT) subjected to cyclic axial compression loadings. The proposed structure is covered with FRP on both the inner and outer walls of a traditional carbon steel tube to solve the corrosion problem of seawater and sea sand concrete and to improve considerably the mechanical properties of the structure at the same time. Cyclic axial compression tests for 12 SFSCTs and 2 concrete-filled steel tubes were carried out. The thickness and type of FRP were used as variables to assess the mode of failure, envelope, plastic strain and stiffness at unloading. The results show that FRP can confine effectively the lateral expansion of concrete. Carbon fibre-reinforced polymer (CFRP) has a better confinement performance than basalt fibre-reinforced polymer (BFRP). According to the different confinement mechanisms of the internal and external layers of FRP on concrete, a more reasonable cyclic stress–strain model was proposed, and the superiority of the proposed model was verified by comparison with the experimental results.

Biomechanical analysis of the role of hinge support fixators on hinge stability in medial closing wedge distal femoral osteotomy

BackgroundThis study aimed to examine the hinge-stabilizing biomechanical effects of hinge support fixators, applied for lateral hinge fractures sustained following distal femoral osteotomy. MethodsMedial closing wedge distal femoral osteotomy was performed using a locking plate on 10 cadaveric limbs. The limbs were divided into two groups: the non-fracture group and the lateral hinge fracture group. A cyclic axial load of 400 N was applied to the knee to keep it extended and flexed at 45°. The hinge-stabilizing effects of adding a screw or a short support plate to the lateral fracture site were examined by measuring the translation and rotational angles of the anterodistal and posterodistal hinge positions as well as the surface strains of the medial locking plate. FindingsTranslation and rotation in the fracture group were significantly more pronounced than in the non-fracture group, at the anterodistal and posterodistal positions. Translations at both positions were significantly reduced, by adding the support plate, during both extension and 45-degree flexion in the fracture group. The rotation at the posterodistal position upon extension and the anterodistal position upon 45-degree flexion was significantly reduced by the support plate. The surface strain of the medial plate in the fracture group was significantly reduced by the support plate upon both extension and 45-degree flexion. InterpretationLateral hinge fractures caused abnormal hinge movements, which were significantly reduced by the short support plate. A short support plate could be used if a hinge fracture occurs during distal femoral osteotomy, to improve lateral hinge stability.

ОБЕСПЕЧЕНИЕ ГЕРМЕТИЧНОСТИ В СОЕДИНЕНИЯХ ДЕТАЛЕЙ С НАТЯГОМ

Work objective is to solve the urgent problem of increasing the tightness and reliability of pressure couplings during their operation under dynamic loads. &#x0D; Theoretical and experimental studies assessing the impact on the tightness due to roughness nature of mating surfaces and three types of coatings: soft, double-layer and hard have been undertaken. The joints were tested under the influence of axial cyclic load and torque on a bench for accelerated testing.&#x0D; It is established that tightness of pressure couplings during operation under dynamic loads significantly depends on the parameters of microgeometry and physical and mechanical properties of the mating surface material that determine their actual contact area. Recommendations for preparing the surfaces of parts before pressure coupling assembling have been developed.&#x0D; It is proved that the use of regular microrelief and soft galvanic coatings of mating surfaces have a significant effect on the tightness of pressure couplings.

Angular stable locking in a novel intramedullary nail improves construct stability in a distal tibia fracture model

IntroductionIntramedullary nails are frequently used for treatment of unstable distal tibia fractures. However, insufficient fixation of the distal fragment could result in delayed healing, malunion or nonunion. Recently, a novel concept for angular stable nailing was developed that maintains the principle of relative stability and introduces improvements expected to reduce nail toggling, screw migration and secondary loss of reduction. The aim of this study was to investigate the biomechanical competence of the novel angular stable intramedullary nail concept for treatment of unstable distal tibia fractures, compared to a conventional nail locking in a human cadaveric model under dynamic loading. Materials and methodsTen pairs of fresh-frozen human cadaveric tibiae with a simulated AO/OTA 42-A3.1 fracture were assigned to 2 groups for reamed intramedullary nailing using either a conventional (non-angular stable) Expert Tibia Nail (ETN) with 3 distal screws or the novel Tibia Nail Advanced (TNA) system with 2 distal angular stable locking low-profile retaining screws. The specimens were biomechanically tested under conditions including initial quasi-static loading, followed by progressively increasing combined cyclic axial and torsional loading in internal rotation until failure of the bone-implant construct. Both tests were monitored by means of motion tracking. ResultsInitial nail toggling of the distal tibia fragment in varus and flexion under axial loading was lower for TNA compared to ETN, being significant in flexion, P = 0.91 and P = 0.03. After 5000 cycles, interfragmentary movements in terms of varus, flexion, internal rotation, axial displacement, and shear displacement at the fracture site were all lower for TNA compared to ETN, with flexion and shear displacement being significant, P = 0.14, P = 0.04, P = 0.25, P = 0.11 and P = 0.04, respectively. Cycles to failure until both interfragmentary 5° varus and 5° flexion were significantly higher for TNA compared to ETN, P = 0.04. ConclusionFrom a biomechanical perspective, the novel angular stable intramedullary nail concept provides increased construct stability and maintains it over time while reducing the number of required locking screws without impeding the flexibility of the nail itself and resists better towards loss of reduction under dynamic loading, compared to conventional locking in intramedullary nailed unstable distal tibia fractures.

The insidious risk of periprosthetic fracture in clinically functional total hip arthroplasties: A biomechanical study of willed joints.

Femoral bone quality is a major risk factor of periprosthetic fracture after total hip arthroplasty (THA), which has mortality similar to native hip fractures but higher short-term morbidity. The goal of this study was to quantify cortical strains at the site of expected Vancouver Type-B periprosthetic fracture as a function of bone mineral density, femoral stem material, and fixation method using a series of 29 autopsy-retrieved, clinically asymptomatic hip joints with THA. Periprosthetic bone mineral content and density was assessed using dual-energy X-ray absorptiometry by Gruen Zone. Specimens then underwent combined cyclic axial and torsional loading, increasing incrementally from 100 N and ±1 Nm to peaks of 700 N and ±5 Nm. All specimens experienced significantly higher strains on the lateral surface than on the anterior surface, indicating that the bending loads in the frontal plane, rather than axial/torsional loads, had the predominant effect. Multiple significant relationships (p = 0.04, p = 0.02) were found between predicted periprosthetic strains calculated from radiographic measurements and observed principal strains. Though THA in the present study were in successful clinical service, the produced results indicated that some femurs with rigid cemented or noncemented implants were potentially at high risk for Vancouver Type-B fractures, which may be predicted radiographically.

Experimental and Finite-Element Studies of Buried Pipes Connected by a Bellow Joint under Cyclic Shear Loading

AbstractIn an accompanying paper, pipes that were connected by a bellow joint were examined under cyclic axial loading. The results show that the bellow connection can significantly reduce the axia...

A study on the behaviour of offshore suction bucket foundations under cyclic axial compressive loading

ABSTRACT Suction bucket foundations of offshore wind turbines (OWTs) are subjected to cyclic loads induced by wind and waves. The behaviour of buckets embedded in saturated sandy soil subjected to cyclic axial compression was studied using a finite element (FE) model. Accumulation of permanent soil deformations and excess pore water pressure in saturated sandy soil due to cyclic axial compression were taken into account by a fully coupled two-phase model combined with a hypoplastic constitutive model with intergranular strain. The Kozeny–Carman relationship was adopted for porosity–permeability dependence. The main focus was dedicated to the changes in load transfer via components of bucket with increasing number of load cycles. Loads that led to progressive failure, attenuation and shakedown behaviour were described. Effects of soil permeability and density, load frequency and amplitude, the bucket aspect ratio on the load transfer and bearing mechanism of the bucket were presented.