Combined Axial Loading Research Articles

Numerical investigation of corroded middle‐high strength pipeline subjected to combined internal pressure and axial compressive loading

AbstractBuried oil and gas pipelines may face the threat of geological disasters such as landslides, faults, and floods. However, long‐term buried oil and gas pipelines often have corrosion defects, which bring greater challenges to the safe operation of pipelines. In this study, via the finite element analysis method validated by the testing results, the blasting pressure of a middle‐high strength pipeline with corrosion defects under an axial compressive load, the distribution of the von Mises stress on the pipeline surface, and the local buckling behavior of the pipeline were studied. In the analysis of the influencing factors, the axially compressive load, the size of the corrosion defects, and the characteristics of the pipeline material were studied. Based on 437 sample points, an artificial neural network was adopted to predict the burst pressure of a pipeline with corrosion defects. By comparing the prediction results with the numerical simulation results, the accuracy verification of the prediction model was conducted. When the axially compressive load increases to a certain value, the burst pressure of a pipeline with corrosion defects will begin to decrease rapidly as the axial compressive load increases. The larger the size of the corrosion defect, the smaller the burst pressure of the pipeline. The depth and length of the corrosion defect have a significant influence on the blasting pressure. The lower the steel grade of the pipeline, the smaller the Y/T ratio, and the lower the bursting pressure of the pipeline. Both the axial compressive load and the size of the corrosion defect affect the failure mode of the pipeline. When the corrosion defect's size is small and the axial compressive load is small, the pipeline material fails. When the corrosion defect's size is large enough, and the axial compressive load is large enough, the pipeline is prone to structural instability. An increase in the axial compressive load and the decrease in the corrosion defect's size cause the local stress concentration of the corrosion defects to become more significant. When the axial compressive load on the pipeline is small, the increase in the axial compressive load does not affect the bursting pressure of the pipeline, but it greatly increases the degree of the local buckling of the pipeline. A decrease in the depth and width of the corrosion defects and an increase in their length results in the local buckling of the pipeline becoming more severe.

Development of axial compression and combined axial compression and torque loading configurations to reproduce strain in the implanted femur during activities of daily living

Femoral strain is indicative of the potential for bone remodeling (strain energy density, SED) and periprosthetic femoral fracture (magnitude of principal strains) after total hip arthroplasty (THA). Previous modeling studies have evaluated femoral strains in THA-implanted femurs under gait loads including both physiological hip contact force and femoral muscle forces. However, experimental replication of the complex muscle forces during activities of daily living (ADLs) is difficult for in vitro assessment of femoral implant or fixation hardware. Alternatively, cadaveric tests using simplified loading configurations have been developed to assess post-THA bone mechanics, although no current studies have demonstrated simplified loading configurations used in mechanical tests may simulate the physiological femoral strains under ADL loads. Using an optimization approach integrated with finite element analysis, this study developed axial compression and combined axial compression and torque testing configurations for three common ADLs (gait, stair-descent and sit-to-stand) via matching the SED profile of the femur in THA-implanted models of three specimens. The optimized simplified-loading models showed good agreement in predicting bone remodeling stimuli (post-THA change in SED per unit mass) and fatigue regions as compared with the ADL-loading models, as well as other modeling and clinical studies. The optimized simplified test configurations can provide a physiological-loading based pre-clinical platform for the evaluation of implant/fixation devices of the femur.

Behavior of steel-reinforced composite concrete columns under combined axial and lateral cyclic loading

This study presents the experimental and numerical investigations on structural steel-reinforced concrete (SRC) columns under combined axial and lateral cyclic loadings. The main parameters evaluated are the peak lateral strength, mode of failure, hysteretic response, stiffness degradation, and energy dissipation potential of SRC columns. A parametric study has been conducted using a finite element software ABAQUS to predict the flexural capacity of the SRC columns under varying axial load levels and to evaluate the reliability of the design guidelines of Eurocode 4 (2004) and AISC 360-16 (2016) in predicting the axial load (P) - bending moment (M) interaction behavior of SRC columns. In the tension damage regions, the experimental and numerical data points mostly lie within or on the unfactored P-M envelopes of both these standards. However, the data points are found to fall outside the P-M envelopes in the compression damage region. For the SRC columns designed to fail in the compression damage, the Eurocode 4 (2004) provisions showed a more reliable prediction of the failure loads under the uniaxial bending condition.

Fatigue life prediction for the AISI 4340 steel under multiaxial variable-amplitude loading with respect to the calculated rainflow damage based on the path length

The high-cycle fatigue life with respect to the multiaxial variable-stress amplitude was evaluated by applying the newly proposed total path length method for calculating the stress amplitude. Variable-stress-amplitude fatigue tests were conducted for verification based on the combined axial and torsional loads on AISI 4340 steel. The fatigue test load waveform denoted that the stress amplitude, mean stress, and load direction varied within one loop. The obtained lives were shorter than those predicted using the Wang–Brown method, longer than those predicted using the PDMR method, and comparable to those predicted using the total path length method.

Analysis of beam-column elements on non-homogeneous soil using the differential transformation method

This paper describes an analytical approach to conduct an analysis of beam-column elements with generalized end-boundary conditions on a homogeneous or non-homogeneous Pasternak elastic foundation. The mathematical formulation utilized herein is that presented by the senior author in a recent work. The differential equation (DE) governing the behavior of the beam-column element is solved using the differential transformation method (DTM). The DTM offers practical advantages over other conventional approaches when solving the proposed structural model. The proposed formulation provides the flexibility to account for i) combined lateral and axial load at the ends of the element, ii) homogeneous or non-homogeneous soil, iii) Pasternak elastic foundation, and iv) an external arbitrary transverse load acting on the element. The effects of various slenderness ratios, pile-soil stiffness ratios, and classical and semirigid boundary conditions can be easily studied with the proposed formulation. Examples are presented to validate the accuracy of the model and its applicability over a wide range of analyses.

Using composite yield mechanism to mitigate seismic damage to exposed steel column base connections

A novel exposed column base (ECB) connection, featuring composite yield mechanism (i.e., a combination of anchor rod and base plate yielding), has been recently proposed in Japan for optimum seismic performance. This paper focused on investigating the effects of using composite yield mechanism on damage mitigation for ECB connections. In doing so, four two-thirds scale specimens, with different base connection configurations, were tested under combined flexure and axial load. Their performances were assessed and compared in terms of damage evolution, moment-rotation relationship and energy dissipation. The experimental results showed that for ECB connection with composite yield mechanism, both anchor rod and base plate will actively contribute to the moment resistance and energy dissipation. This can successfully postpone the interior anchor rod yielding and fracture, compared to the ECB connection with anchor rod yield mechanism. Meanwhile, the strain demands on exterior plate can be also released compared to the ECB connection with base plate yield mechanism. The relative contributions from anchor rod and base plate of ECB connection with composite yield mechanism can be controlled by changing the exterior plate thickness. In addition, an analytical method was proposed to predict the yield and ultimate moment strength for the Composite Yield ECB connection based on the principle of virtual work. The difference between predicted and measured moment strength is within 15%, showing the validity of the proposed method for moment strength prediction.

Experimental seismic behavior of ultra-high performance concrete columns with high strength steel reinforcement

Ultra-High Performance Concrete (UHPC) is an advanced cementitious composite material that exhibits high ductility and durability with superior mechanical properties, e.g. compressive strength in excess of 22 ksi (150 MPa) and sustained post-cracking tensile strength greater than 0.7 ksi (5 MPa). These characteristics have promoted UHPC to be considered for new construction applications specially for next-generation bridge structures. Currently, UHPC is commonly used in limited structural applications, such as joints and connections between precast structural elements. However, there is a growing interest in larger UHPC applications and new designs of full structural members as the UHPC market keeps growing and material becomes more available. One potential application for structural elements is full UHPC columns, which is the focus of this study. This paper presents an experimental investigation of the structural and seismic behavior of large-scale full UHPC columns reinforced with conventional and high strength steel reinforcement. The UHPC columns were tested under combined axial and quasi-static cyclic lateral loading at the University of Nevada, Reno. The testing program included four columns where the seismic performance of three different columns with grade 100 reinforcement is compared with a reference UHPC column with regular grade 60 reinforcement. Thus, the varied experimental parameters included the longitudinal reinforcement ratio and grade as well as the transverse reinforcement ratio. Results demonstrate that UHPC columns have reasonable ductility and drift capacity. Moreover, higher reinforcement ratio or grade is needed to better utilize the superior mechanical properties of UHPC and recommended to inform future design.

Cyclic behavior of damage-controllable steel fiber reinforced high-strength concrete reduced-scale frame structures

To obtain desirable damage-controllable frame structures, three 1/3-scale, 2-bay, 2-story steel fiber reinforced high-strength concrete frames with high-strength steel rebars were fabricated and tested under combined axial load and cyclic lateral load. Under the principle of equal strength design, three types of columns with different arrangements of longitudinal rebars were designed (i.e., the first only reinforced with HRB 600 MPa high-strength steel rebars, the second reinforced with hybrid HRB 600 MPa high-strength and 1200 MPa ultra-high-strength (UHS) steel rebars, and the third only reinforced with UHS steel rebars), while the beams were generally reinforced with HRB 600 MPa steel bars. The test results reveal that all frames exhibited comparative seismic performance and represented acceptable residual deformation before a lateral drift of 3%, which can be a promising alternative to traditional frames. Incorporating UHS rebars in frame columns could make the inter-story displacement distribution relatively uniform, which would avoid the damage concentration in the bottom floor and the collapse of the structure. Compared to the frame merely with HRB 600 MPa rebars in the column, the frames with UHS rebars showed a positive lateral stiffness in a considerable deformation range after the formation of the plastic hinge in the beam, and the residual displacement and residual crack width were effectively controlled. The proposed ideal load-deformation behavior of the damage-controllable frame can clearly reflect the failure mechanism of the structure, and the secondary stiffness ratios of different stages can be obtained to accurately evaluate the damage control performance of the structure at different stages.

Experimental study on seismic behavior of full scale square concrete filled steel tubular stocky columns

This study mainly presented a pseudo-static experiment on two full-scale square CFST short columns with the cross-sectional width of 600 mm under combined constant axial load and cyclic lateral load. The seismic performance of the two full-scale CFST columns were investigated. Meanwhile, the plastic hinge length of the specimens was discussed. The test results presented that the specimens suffered bend-shear failure. The local buckling of steel tube occurred at the end of the specimens and the core concrete crushed. The safety redundancy of lateral bearing capacity decreased in full-scale specimen. By the method of physical observation, the plastic hinge length Lp1 was determined mainly according to the range of the local buckling of steel tube. There had a great difference between the prediction of plastic hinge lengths by the existing calculation model and the plastic hinge lengths obtained by the test.

Behavior of GFRP strengthening masonry walls using glass fiber composite anchors

This paper presents experimental and theoretical investigations on the short-term behavior of stone masonry walls constructed with lime mortar. The walls were strengthened using unidirectional GFRP (Glass fiber reinforced polymers) sheets to resist out-of-plane loads. Two methods of anchorage were used to enhance the behavior of strengthened stone masonry walls by preventing premature peeling-off of the GFRP sheets caused by GFRP debonding. Nine GFRP strengthened limestone masonry wall specimens including two control specimens were tested under combined constant low axial load levels and out-of-plane bending caused by two point monotonic loading. All the specimens have height-to-thickness (h/t) ratio of 7.1. The main variables investigated were GFRP reinforcement ratio, arrangement of GFRP, axial load level, and anchorage method. The strengthened walls showed an improvement in the out-of-plane performance which was significantly enhanced by anchorage. The increase in wall ultimate load carrying capacity reached 100%.

Contact probabilities of an angular ball bearing under a combined axial and radial load

A contact probability model of an angular ball bearing is developed in this study by means of multi-body dynamics and a spherical grid division method. The model is used to analyze the contact probability of a ball surface of a typical angular ball bearing under different loading conditions. It is found that the contact probability of the ball with the inner and outer races of the bearing under a pure radial loading will have the largest probability distribution along the ball's circular profile intersecting the two contact points between the ball and the inner and outer races. Whilst the axial load on the ball bearing plays a decisive role in the stable distribution of the contact probability of the ball under various combinations of axial and radial loads. The study also shows that a steady-state wear will accumulate on the ball surface and the raceways when a large constant axial load is applied to the angular ball bearing.

Mechanical behavior of strain-hardening cement-based composites (SHCC) subjected to torsional loading and to combined torsional and axial loading

Strain-hardening cement-based composites (SHCC) are a novel class of fiber-reinforced concretes which exhibit high tensile strain capacity prior to failure localization. Although the tensile behavior of SHCC has been a matter of study in numerous research works, the behavior of these composites under other loading modes has scarcely been investigated. The article at hand addresses the mechanical behavior of two types of normal-strength SHCC subject to uniaxial tension, torsion, and combinations of torsional and axial loading. The SHCC under investigation were made with polyvinyl-alcohol (PVA) and ultra-high molecular weight polyethylene (UHMWPE) fibers, respectively. Digital Image Correlation (DIC) was applied to evaluate the multiple cracking process and crack opening modes in conjunction with the axial and torsional loading histories. The study demonstrates the suitability of torsion experiments to assess the multi-axial and shear performance of SHCC, highlights the relation between multiple cracking and transfer capacity for shear forces, and emphasizes the importance of the type of reinforcing fibers on the shear strength and ductility of such composites.

Experimental Investigation and Plasticity Modeling of SS316 L Microtubes Under Varying Deformation Paths

Abstract In this paper, results for SS316 L microtube experiments under combined inflation and axial loading for single and multiloading segment deformation paths are presented along with a plasticity model to predict the associated stress and strain paths. The microtube inflation/tension machine, utilized for these experiments, creates biaxial stress states by applying axial tension or compression and internal pressure simultaneously. Two types of loading paths are considered in this paper, proportional (where a single loading path with a given axial:hoop stress ratio is followed) and corner (where an initial pure loading segment, i.e., axial or hoop, is followed by a secondary loading segment in the transverse direction, i.e., either hoop or axial, respectively). The experiments are designed to produce the same final strain state under different deformation paths, resulting in different final stress states. This difference in stress state can affect the material properties of the final part, which can be varied for the intended application, e.g., biomedical hardware, while maintaining the desired geometry. The experiments are replicated in a reasonable way by a material model that combines the Hill 1948 anisotropic yield function and the Hockett–Sherby hardening law. Discussion of the grain size effects during microforming impacting the ability to achieve consistent deformation path results is included.

Data-Driven Approach to Predict the Plastic Hinge Length of Reinforced Concrete Columns and Its Application

AbstractInelastic response of reinforced concrete columns to combined axial and flexural loading is characterized by plastic deformations localized in small regions, which are idealized as plastic ...

Comparison of Open Anterior Syndesmotic Repair Augmented With Suture-Tape and Trans-syndesmotic Screw Fixation: A Biomechanical Study

The treatment of syndesmotic injuries with ankle fractures is controversial. The purpose of this study was to compare the biomechanical properties of open anterior syndesmotic repair with those of screw fixation. Ten matched pairs of human cadaver specimens were subjected to open syndesmotic repair or screw fixation. Each specimen underwent initial intact physiologic loading, consisting of 10 cycles of external torsional loading with a peak torque of 7.5 Nm at 0.05 Hz. Injuries of the anterior inferior tibiofibular ligament, tibiofibular interosseous membrane, and deltoid ligament were applied to each specimen. Postfixation cyclic loading consisted of 50 cycles of combined axial and external rotation loading with peak torques of 750 N and 7.5 Nm at a rate of 0.05 Hz. After postfixation loading, each specimen underwent failure loading by external rotation at 0.25 degrees/second. Failure torque and failure angle were measured. The paired t test and Wilcoxon signed-rank test were used to analyze the data. Mean failure torques were 95.63 Nm in the open anterior syndesmotic repair augmented with suture-tape group and 108.61 Nm in the screw group. Mean failure angles were 34.93 degrees in the open anterior syndesmotic repair augmented with suture-tape group and 43.55 degrees in the screw group. These data were not statistically significantly different between the groups (p= .7682 and .4133, respectively). Open anterior syndesmotic repair augmented with suture tape for ankle syndesmotic injury provides similar torsional strength to that of screw fixation. Therefore, this technique can be considered as an alternative treatment option for syndesmosis injury.

Mechanical behavior of thin tubes under combined axial compression and bending

In practical application, pipelines will inevitably experience bending and compression during manufacture, transportation and offshore installation. The mechanical behavior of tubes under combined axial compression and bending loads is investigated using experiments and finite element method in this paper. Tubes with D/t ratios in the range of 40 and 97 are adopted in the experiments. Then, the ultimate loads and the local buckling modes of tubes are studied. The commercial software ABAQUS is used to build FE models to simulate the load-shortening responses of tubes under combined loads. The results acquired from the ABAQUS simulation are compared with the ones from verification bending experiment, which are in good agreement with each other. The models in this paper are feasible to analyze the mechanical properties of tubes under combined axial compression and bending loads. The related results may be of interest to the manufacture engineers.

A parametric study on the stability of fiber reinforced rubber bearings under combined axial and shear loads

Fiber Reinforced Bearings (FRBs) have proven to be a valuable rubber-based base isolation technology in which flexible fiber reinforcements are used to replace the steel layers commonly adopted for the manufacturing of Laminated Rubber Bearings (LRBs). Thanks to the low weight and cost of FRBs, these devices could prove to be instrumental for the promotion of base isolation applications to houses and residential buildings of developing countries of the world in seismic regions. This study is based on the results of a large set of Finite Element Analyses (FEAs) aimed to assessing the performance of FRBs under combined axial and shear loads. The aim of this work is that of filling a lack of knowledge regarding the lateral displacement capacity of FRBs: research studies available in literature do not consider the effects of axial pressure, material properties, primary and secondary shape factors on the response of these devices under combined axial and lateral loads. Conclusions of this study underline that the simple design formula commonly adopted for the design of FRBs underestimate the effect of the axial pressure in limiting the lateral displacement capacity of the bearings. Moreover, available simplified formula, do not offer an accurate estimate of the force response of these bearings under combined loads. Additional FEAs are needed to extend the results of this study to bearings of other shapes, including circular and square isolators.

Techniques for management of hyperextension bicondylar tibial plateau fractures.

Hyperextension bicondylar tibial plateau (HEBTP) fractures are a subset of tibial plateau fractures that primarily affect the sagittal alignment of the tibial condyles. They comprise less than 20% of all bicondylar injuries [ [1] Gonzalez LJ Lott A Konda S Egol KA. The Hyperextension Tibial Plateau Fracture Pattern: A Predictor of Poor Outcome. J Orthop Trauma. 2017; 31: e369-e374 Crossref PubMed Scopus (13) Google Scholar ]. They have been described following both high and low energy mechanisms [ 1 Gonzalez LJ Lott A Konda S Egol KA. The Hyperextension Tibial Plateau Fracture Pattern: A Predictor of Poor Outcome. J Orthop Trauma. 2017; 31: e369-e374 Crossref PubMed Scopus (13) Google Scholar , 2 Firoozabadi R Schneidkraut J Beingessner D Dunbar R Barei D. Hyperextension Varus Bicondylar Tibial Plateau Fracture Pattern: Diagnosis and Treatment Strategies. J Orthop Trauma. 2016; 30: e152-e157 Crossref PubMed Scopus (22) Google Scholar , 3 Zhao R Lin Z Long H Zeng M Cheng L Zhu Y. Diagnosis and treatment of hyperextension bicondylar tibial plateau fractures. J Orthop Surg Res. 2019; 25 (14): 191 Crossref Scopus (6) Google Scholar , 4 Chouhan DK Chand Saini U Kumar Rajnish R Prakash M Complex bicondylar tibial plateau fractures with reversed tibial slope - Our experience with a fracture-specific correction strategy. Trauma Case Rep. 2019; 28100256 Google Scholar ]. In these injuries, a combined axial and varus load is imparted to the knee which results in compressive forces to the anterior portion of the tibial plateau and tension across the posterior plateau. Given the varus alignment of the knee and tether of the posterolateral knee capsuloligamentous complex, there is asymmetric concentration of force to the medial plateau resulting in a characteristic injury pattern that is often more severe on this side [ 5 Chiba T Sugita T Onuma M Kawamata T Umehara J. Injuries to the posterolateral aspect of the knee accompanied by compression fracture of the anterior part of the medial tibial plateau. Arthroscopy. 2001; 17: 642-647 Abstract Full Text Full Text PDF PubMed Scopus (21) Google Scholar , 6 Yoo JH Kim EH Yim SJ Lee BI. A case of compression fracture of medial tibial plateau and medial femoral condyle combined with posterior cruciate ligament and posterolateral corner injury. Knee. 16. 2009: 83-86 Google Scholar , 7 Tomás-Hernández J Monyart JM Serra JT Vinaixa MR Farfan EG García VM Feliu EC. Large fracture of the anteromedial tibial plateau with isolated posterolateral knee corner injury: case series of an often missed unusual injury pattern. Injury. 2016; 47: S35-S40 Abstract Full Text Full Text PDF PubMed Scopus (13) Google Scholar ]. Regardless of mechanism, a common characteristic of these injuries is anteromedial metaphyseal comminution and loss of the normal posterior slope of the medial, and often, lateral side. The average anatomic medial proximal tibial angle (MPTA) is 87o (range 85-900); the average posterior proximal tibial angle (PPTA) is 810 (range 77-84o) [ [8] Paley D. Normal Lower Limb Alignment and Joint Orientation. In Paley D, editor. Principles of Deformity Correction 1st ed. Berlin: Springer-Verlag; 2003, p. 1-18. Google Scholar ]. Anatomic reduction of the articular surface and restoration of sagittal and coronal alignment must be achieved at surgery and maintained until union.

Shear Strength of Reinforced Concrete Columns Retrofitted by Glass Fiber Reinforced Polyurea

Aged structures and structures constructed based on outdated non-seismic design codes should be retrofitted to enhance their strength, ductility, and durability. This study evaluates the structural performance of reinforced concrete (RC) columns enhanced via polyurea or glass fiber reinforced polyurea (GFRPU) strengthening. Four RC column specimens, including a reference specimen (an unstrengthened column), were tested to evaluate the parameters of the strengthening materials and the strengthened area. The tests were carried out under a combined constant axial compressive load and quasi-static cyclic loading. The experimental results show that the composite strengthening provides lateral confinement to the columns and leads to enhanced ductility, shear-resistance capacity, and dissipated energy. The shear strength provided by the composites depends on the degree of lateral confinement achieved by the composite coating. The specimens finally failed through the development of diagonal tension cracks within the potential plastic hinge regions. The specimen treated with GFRPU strengthening showed greater strength and dissipated more energy than the specimen treated with polyurea strengthening. Furthermore, by modifying ATC-40, this study proposed an equation to estimate the shear capacity provided by the composites.

Comparison of Open Syndesmotic Repair and Trans-syndesmotic Screw Fixation: A Biomechanical Study

Category:Trauma; AnkleIntroduction/Purpose:We hypothesized that open syndesmotic repair for ankle syndesmotic injury would provide adequate strength. The purpose of this study was to compare the biomechanical properties of open syndesmotic repair with those of screw fixation.Methods:Ten matched pairs of human cadaver specimens were subjected to open syndesmotic repair or screw fixation. Each specimen underwent initial intact physiologic loading, consisting of 10 cycles of external torsional loading with a peak torque of 7.5 Nm at 0.05 Hz. Post-fixation cyclic loading consisted of 50 cycles of combined axial and external rotation loading with peak torques of 750 N and 7.5 Nm at a rate of 0.05 Hz. After post-fixation loading, each specimen underwent failure loading by external rotation at 0.25 degrees/second. Failure was defined as a sudden decrease in the torque-degree curve. Failure torque and failure angle were measured. The paired t-test and Wilcoxon signed-rank test were used to analyze the data.Results:Mean failure torques were 95.63 Nm in the open syndesmotic repair group and 108.61 Nm in the screw group. Mean failure angles were 34.93 degrees in the open syndesmotic repair group and 43.55 degrees in the screw group. These data were not statistically significantly different between the two groups (p = 0.7682 and 0.4133, respectively).Conclusion:Open syndesmotic repair for ankle syndesmotic injury provides similar torsional strength to that of screw fixation. Therefore, this technique can be considered as an alternative treatment option for syndesmosis injury.