Principal Tensile Strain Research Articles

Evolution Characteristics of Strain and Displacement Fields in Double-Hole Short-Delay Blasting Based on DIC

In the process of porous blasting excavation in engineering projects such as mining, hydropower stations, and tunnels, the delay time between adjacent blast holes significantly influences the characteristics of rock fracture and fragmentation. In order to visually explore the changing characteristics of strain and displacement between adjacent blast holes under different delay times, polymethyl methacrylate (PMMA) plates were used to simulate rock materials, and 2D digital image correlation (2D-DIC) testing methods were employed to measure the explosive strain field with different delay times (0 µs, 5 µs, 15 µs, 40 µs, 70 µs) for dual holes. Full-field principal strain cloud maps and displacement fields of PMMA boards in two-dimensional spatial coordinates were obtained, and the representative monitoring points were analyzed. The experimental results show that the maximum values of the first compressive principal strain peak and the first tensile principal strain peak at the connecting center of the two holes exist at a delay time of 0~40 µs under blasting conditions with the same hole distance and single hole charge. At the center point of the connection between the two holes, the interval time between the two principal strain peaks decreases with the increase in delay time. The maximum principal strain on the central vertical line of the connection line decreases exponentially with the increase in hole distance, and the attenuation trend increases first and then decreases with the delay time between 0 and 40 µs. At the peak of strain, the maximum average displacement of the connecting center of the two holes exists in the delay time between 0 and 40 µs. With the increase in delay time, the displacement trend between the two explosion holes gradually changes from shear to tension, and the vulnerable damage area increases, which makes the communication between the two explosion holes easier. This study can provide a basis for the precise selection of delay times between blasting holes in engineering.

Effects of carbonation modification on shear performance of recycled aggregate concrete beams: Test and mechanism analysis

The effective use of recycled aggregates (RAs) in construction significantly contributes to environmental preservation and the conservation of non-renewable natural resources. However, RAs typically exhibit inferior performance relative to natural aggregates (NAs). To improve the quality of RAs, carbonation modification has been introduced as an eco-friendly and practical method. This study explores the shear performance of concrete beams that incorporate various replacement ratios (30 %, 50 %, 70 %, and 100 %) of carbonated recycled aggregates (CRAs). The experiment employed Digital image correlation (DIC) system to evaluate the stress distribution on the concrete surface within the shear span section. The evaluation of shear performance was conducted through comprehensive analysis includes load-deflection curve, steel strain, the width of the primary diagonal crack, average principal tensile strain, orientation of principal directions, average shear strain, and shear deflection. A practical approach was adopted to separate the shear strength contributions of transverse steel (Vs) and concrete (Vc), based on transverse steel strains along the primary diagonal crack. Results indicate that carbonated recycled aggregate concrete (CRAC) beams demonstrate enhanced shear performance in comparison to recycled aggregate concrete beams. Shear strength significantly decreases with replacement rates exceeding 70 %. Furthermore, the experimental results were compared against shear strength with the design codes, and shear deflection with existing models.

A Noninvasive Clinical Method to Measure in Vivo Mechanical Strains of the Lamina Cribrosa by OCT

To measure mechanical strain of the lamina cribrosa (LC) after intraocular pressure (IOP) change produced 1 week after a change in glaucoma medication. Cohort study. Adult glaucoma patients (23 eyes, 15 patients) prescribed a change in IOP-lowering medication. Noninvasive OCT imaging of the eye. Deformation calculated by digital volume correlation of OCT scans of the LC before and after IOP lowering by medication. Among 23 eyes, 17 eyes of 12 persons had IOP lowering ≥ 3 mmHg (reduced IOP group) with tensile anterior-posterior Ezz strain= 1.0% ± 1.1% (P= 0.003) and compressive radial strain (Err)=-0.3% ± 0.5% (P= 0.012; random effects models accounting inclusion of both eyes in some persons). Maximum in-plane principal (tensile) strain and maximum shear strain in the reduced-IOP group were as follows: Emax= 1.7% ± 1.0% and Γmax= 1.4% ± 0.7%, respectively (both P < 0.0001 vs. zero). Reduced-IOP group strains Emax and Γmax were significantly larger with greater % IOP decrease (P < 0.0001 and P < 0.0001, respectively). The compliances of the Ezz, Emax, and Γmax strain responses, defined as strain normalized by the IOP decrease, were larger with more abnormal perimetric mean deviation or visual field index values (all P ≤ 0.02). Strains were unrelated to age (all P ≥ 0.088). In reduced-IOP eyes, mean LC anterior border posterior movement was only 2.05 μm posteriorly (P= 0.052) and not related to % IOP change (P= 0.94, random effects models). Only Err was significantly related to anterior lamina depth change, becoming more negative with greater posterior LC border change (P= 0.015). Lamina cribrosa mechanical strains can be effectively measured by changes in eye drop medication using OCT and are related to degree of visual function loss in glaucoma. Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.

In vitro effect of horseshoe length on hoof wall deformation, expansion, and strain

Abstract Shoeing techniques have the potential to affect hoof growth, causing abnormal hoof conformations, which in turn put affected horses at risk for lameness and injury. Racehorses are often shod with shorter shoe branches which may predispose them to underrun heel hoof conformation. Horseshoe branch length was tested to determine the effect on hoof wall deformations, expansion, strain and fetlock extension during midstance limb loading. Our hypotheses were that shortening of the shoe branch length would increase fetlock extension, increase compressive strains at the heel, and change principal strain directions in a proximodorsal direction. Nine cadaveric forelimbs were loaded in vitro to simulate mid-stance from walk to canter loads. Analysis of variance was used to assess the effect of horseshoe (no shoe, short shoe, full shoe, and long shoe) on outcome variables. Hoof wall expansion and lateral hoof wall distortion did not differ among treatments. Principal compressive hoof wall strain magnitudes were greater than principal tensile strain magnitudes. As shoe length increased principal compressive strains decreased, except for the middle quarter location; shear strains increased for distal locations and decreased at the proximal heel location; and principal strain directions viewed on the lateral side of the right hoof rotated in a counterclockwise direction at middle and distal quarter locations. Results do not provide evidence that a shorter shoe increases fetlock extension. Additionally, as the shorter shoe had similar strain results to that of an unshod hoof, it is unclear if a shorter shoe could lead to the development of abnormal hoof conformations. Other factors that may play a role in changes of hoof conformation including surface type, amount of exercise and frequency of trimming as well as other planes within the xyz coordinate system for the fetlock and hoof should be investigated.

Investigation and measurement of old building response to the overlapped shield tunnel of multiple schemes in the sandy cobble stratum

Ground movements due to tunneling are becoming increasingly critical as buildings are located around construction sites. This study proposes a new combined reinforcement method using a foundation grouting oblique pipe roof. The former improves the bearing capacity of the subsoil, and the latter blocks the transmission of soil deformation, which weakens the influence of construction during overlapped tunnel under-crossing. Based on this new method, a case study of the shield tunneling response to an old building in Line 6 of China’s Chengdu Metro is presented. Additionally, three-dimensional numerical models without reinforcement, traditional foundation grouting reinforcement, and the new combined reinforcement schemes were compared. The numerical simulation performance was verified using a set of field instrumentation data, which demonstrated that the old building response to the overlapped tunnels was under control, and the maximum deformation, angular distortion, and principal tensile strain of the building were 5.25 mm, 5.10 × 10–6 rad/m, and 0.0081%, respectively. Compared with the traditional reinforcement scheme, the deformation, angular distortion, and principal tensile strain in the combined reinforcement scheme were reduced by 54.78%, 71.02%, and 70.22%, respectively. These results have important implications for the design and construction of shield tunnels and their response to old buildings.

Flexural–shear deformation theory (FSDT) for modeling of mechanical responses of RC beams strengthened in shear with ETS-FRP bars

The flexural–shear deformation theory (FSDT) approach for simulating the shear behavior of reinforced concrete (RC) beams strengthened in shear with embedded-through section fiber-reinforced polymer (ETS-FRP) bars is developed in this study. The key feature of the FSDT approach is to mix both flexural and shear deformation parameters constituted in the beam into an algorithm, which is able to simplify the analysis and shorten the computation time. Most of the formulations adopted in the model are built on the basis of mechanics by applying a few common theories involved in stress and strain fields. Particularly, to couple the participation of the ETS-FRP strengthening system into the developed FSDT, the newly developed bonding-based mechanism between the ETS-FRP bar and concrete is used. The calculation outcome produces the vertical strain (εv), which is the main parameter used to determine the resistance of shear reinforcement. The shear contribution of concrete is derived via the concrete principal tensile strain (ε1). Then, the minimized discrepancy between shear forces induced by flexural (VT) and shear actions (Vtotal) is the condition for termination of the calculation. Through the broad corroboration of the developed model to the experimental data with respect to structural responses, excellent agreement and high accuracy are found. To offer prospects for the design practice of ETS-strengthened beams, a parametric study on the effects of important design variables is implemented against the results assessed by a guideline released by the American Concrete Institute (ACI). Consequently, the proposed FSDT approach provides more insight into the responses of ETS-strengthened beams than the ACI guideline, which is helpful for practitioners.

Constitutive laws of softened UHPC in biaxial tension–compression: Experimental study using a planar bi-directional element tester

Ultrahigh-performance concrete (UHPC) has been gradually applied in bridge and building engineering to replace traditional reinforced concrete (RC). More realistic simulations are required for the design of structures. However, a two-dimensional constitutive model for UHPC is lacking. Tsinghua University developed a planar bidirectional element tester (PBET) that can perform tests on various structural types of element specimens. In this study, one nonreinforced UHPC element specimen under uniaxial compression and ten nonreinforced UHPC element specimens under biaxial tension and compressive coupling condition were tested using PBET. The compressive stress–strain relationship was established based on the uniaxial compressive test. By analyzing the test results, the softening effect of the principal tensile strain on the peak compressive stress and strain of UHPC was evaluated. Stress and strain softening coefficients were proposed, and the constitutive law of softened UHPC under compressive stress was modified and verified using the test results, which contributes to the improvement and development for the two-dimensional constitutive law for UHPC.

Verification of Truss-Arch model unified for RC beams with stirrups using shear database

A shear strength analysis model called “Truss-Arch Model Unified (TAMU)” was proposed for shear-critical reinforced concrete (RC) beams with transverse reinforcement. The TAMU has its roots in the Compatibility Strut-and-Tie Model (C-STM) which is a computational modeling approach for the overall force–deformation analysis of deep beams. The TAMU simplified the C-STM so that a limited analysis can be executed by hand methods of analysis to predict the maximum load-carrying capacity of RC deep beams. While the tensile stress of concrete is generally taken into account to evaluate the shear strength of RC beams, the TAMU limit analysis focuses on the strength reduction of the principal diagonal concrete arch due to the transverse principal tensile strain. In the present study, a shear database is assembled from previous works reported in the literature to further substantiate the validity of the TAMU approach. The shear database consists of tested RC beams with shear reinforcement whose shear span-depth ratios (a/d) are between 0.5 and 4.5. Comparative TAMU analysis results show satisfactory agreement with the ultimate strengths observed in 460 RC beam tests regardless of D- and B-regions, demonstrating the method’s ability to predict the maximum load-carrying capacity for shear-critical beams. Additionally, the TAMU approach shows better accuracy and consistency against the database compared to AASHTO sectional shear design methods. The probability of reasonable prediction of the TAMU method is 92% in d-regions and 78% in B-regions, respectively, which is significantly higher than those of AASHTO sectional shear design methods, especially in d-regions. Thus, the TAMU method may be a viable improvement as an alternative strength analysis method for shear-critical RC beams with transverse reinforcement.

Finite Element Model-Computed Mechanical Behavior of Femurs with Metastatic Disease Varies Between Physiologic and Idealized Loading Simulations.

Femurs affected by metastatic bone disease (MBD) frequently undergo surgery to prevent impending pathologic fractures due to clinician-perceived increases in fracture risk. Finite element (FE) models can provide more objective assessments of fracture risk. However, FE models of femurs with MBD have implemented strain- and strength-based estimates of fracture risk under a wide variety of loading configurations, and "physiologic" loading models typically simulate a single abductor force. Due to these variations, it is currently difficult to interpret mechanical fracture risk results across studies of femoral MBD. Our aims were to evaluate (1) differences in mechanical behavior between idealized loading configurations and those incorporating physiologic muscle forces, and (2) differences in the rankings of mechanical behavior between different loading configurations, in FE simulations to predict fracture risk in femurs with MBD. We evaluated 9 different patient-specific FE loading simulations for a cohort of 54 MBD femurs: strain outcome simulations-physiologic (normal walking [NW], stair ascent [SA], stumbling), and joint contact only (NW contact force, excluding muscle forces); strength outcome simulations-physiologic (NW, SA), joint contact only, offset torsion, and sideways fall. Tensile principal strain and femur strength were compared between simulations using statistical analyses. Tensile principal strain was 26% higher (R 2 = 0.719, P < .001) and femur strength was 4% lower (R 2 = 0.984, P < .001) in simulations excluding physiologic muscle forces. Rankings of the mechanical predictions were correlated between the strain outcome simulations (ρ = 0.723 to 0.990, P < .001), and between strength outcome simulations (ρ = 0.524 to 0.984, P < .001). Overall, simulations incorporating physiologic muscle forces affected local strain outcomes more than global strength outcomes. Absolute values of strain and strength computed using idealized (no muscle forces) and physiologic loading configurations should be used within the appropriate context when interpreting fracture risk in femurs with MBD.

One-dimensional fiber beam-column model and two-dimensional fixed crack model for numerical simulation of UHPC structures

Ultra-high performance concrete (UHPC), with much higher compressive strength, tensile strength and ultimate tensile strain than normal concrete, has been experimentally investigated and applied in engineering structures more and more widely. However, there are few numerical models appropriate for the accurate and efficient simulation of UHPC or reinforced UHPC (R/UHPC) flexural members including beams and columns as well as shear-critical members such as shear walls till now, which brings obstacles to the analysis and design of UHPC structures. In this study, the uniaxial skeleton and hysteretic rules for UHPC under tensile and compressive loads are first proposed and verified by material tests. The formulas to calculate all the basic parameters in the model are put forward for convenient use. Then the fiber beam-column model for flexure-dominated UHPC members is established in ABAQUS 2017 software and six R/UHPC column specimens subjected to cyclic load are simulated. Based on simulation results, the equations of transition curves in the uniaxial rules are determined, which have significant influence on the predicted hysteresis curves. On the other hand, a new two-dimensional fixed crack based constitutive model for shear-critical UHPC members is further proposed and implemented in ABAQUS 2017 software by considering the compressive softening due to principal tensile strain and shear stress–strain relationship along cracks of UHPC. Finally, ten R/UHPC shear wall specimens under cyclic loads as well as four R/UHPC deep beams under monotonic loads are simulated and the accuracy of the proposed 2D model for UHPC is validated.

Orthosis and Foot Structure Affect the Fifth Metatarsal Principal Strains During Simulated Level Walking

Background: Fractures of the proximal fifth metatarsal bone are common injuries in elite athletes and are associated with high rates of delayed union and nonunion. Structural features of the foot may increase fracture risk in some individuals, emphasizing the need for intervention strategies to prevent fracture. Although orthotic devices have shown promise in reducing fractures of the fifth metatarsal bone, the effect of orthosis on fifth metatarsal strains is not well understood. Purpose: To quantify the effects of different foot orthotic constructs on principal tensile strains in the proximal fifth metatarsal bone during cadaveric simulations of level walking. An additional purpose was to investigate the relationships between structural features of the foot and corresponding strains on the fifth metatarsal bone during level walking. Study Design: Controlled laboratory study. Methods: A total of 10 midtibial cadaveric specimens were attached to a 6 degrees of freedom robotic gait simulator. Strain gauges were placed at the metaphyseal-diaphyseal junction (zone II) and the proximal diaphysis (zone III) during level walking simulations using 11 different foot orthotic configurations. Images of each specimen were used to measure structural features of the foot in an axially loaded position. The peak tensile strains were measured and reported relative to the sneaker-only condition for each orthotic condition and orthotic-specific association between structural features and principal strains of both zones. Results: In total, 2 of the 11 orthotic conditions significantly reduced strain relative to the sneaker-only condition in zone II. Further, 6 orthotic conditions significantly reduced strain relative to the sneaker-only condition in zone III. Increased zone II principal strain incurred during level walking in the sneaker-only condition showed a significant association with increases in the Meary’s angle. Changes in zone III principal strain relative to the sneaker-only condition were significantly associated with increases in the Meary’s angle and fourth-fifth intermetatarsal angle. Conclusion: The use of orthotic devices reduced principal strain relative to the condition of a sneaker without any orthosis in zone II and zone III. The ability to reduce strain relative to the sneaker-only condition in zone III was indicated by increasing values of the Meary’s angle and levels of the fourth-fifth intermetatarsal angle. Clinical Relevance: Clinicians can use characteristics of foot structure to determine the proper foot orthosis to potentially reduce stress fracture risk in high-risk individuals.

Interactive Effects of Five Dental Implant Design Parameters on the Peak Strains at the Interfacial Bone: A Finite Element Study.

The aim of this study was to evaluate and compare the effect of changing five macrostructural design parameters of dental implants on the peak strains experienced by the interfacial bone. Five geometric variables, including three body-related (implant length, diameter, and taper) and two thread-related (thread depth and thread angle) parameters, were defined. The alveolar bone was modeled as a block with anisotropic and linearly elastic properties with 20-mm height and 12-mm buccolingual and mesiodistal dimensions. Oblique occlusal loads (100-N vertical and 20-N horizontal) were applied to the abutment surface. A total of 162 models with different designs were defined by implementation of a full-factorial design. The peak values of the compressive and tensile principal strains in the cortical and cancellous bones were calculated by finite element analysis (FEA). Implant diameter and length had maximum and minimum effects on the peak compressive and tensile strains at the cortical interface, respectively. Implant diameter and thread depth had maximum and minimum effects on the maximum compressive strain at the cancellous interface, while thread angle and length had maximum and minimum significant effects on the maximum tensile strain at the cancellous interface. The interaction of thread parameters and taper has the greatest effect on the peak compressive and tensile strains at the cancellous interface and also on the peak tensile strain at the cortical interface, while body-related parameters are more effective on the peak compressive strain at the cortical interface.

Study on the Adaptability of Shield Tunnel Segments Orthogonal Crossing Grade III Loess Ground Fissure Section

Taking the Xi’an rail transit line orthogonal crossing the ground fissure section as the engineering background, the structural properties and adaptability of the shield tunnel lining segment under the ground fissure environment are carried out. Using the finite element numerical simulation method, combined with the relevant model tests that have been carried out by predecessors, the damage characteristics of shield tunnel lining segment structure under the action of the ground fissure are revealed. The results show that shield tunnel structure is mainly shear deformation, with local bending deformation. Secondly, the principal tensile stress and principal tensile strain at the arch waist and arch foot of segment ring intersecting with ground fissure section are the largest. The relative dislocation between the rings of the shield tunnel near the ground fissure in the hanging wall is the largest, and the opening of arch top ring seam near the ground fissure in the footwall is the largest. Finally, the conventional shield tunnel lining segment structure cannot be directly used in the ground fissure site with a vertical dislocation of 200 mm.

On the Mechanical and Electrical Properties of the Composite Structure of PVC Membrane and Thin-Film Battery under Biaxial Tension

This paper aims to study the mechanical and electrical properties of the composite structure of PVC film and film cell under biaxial tension. The saddle PVC membrane structure with thin-film battery was obtained by biaxial tensile tests carried out on the composite structure along the fiber direction and at an angle of 45 degrees to the fiber, respectively. The deformation of the film cell and PVC membrane materials was tested using digital image technology, and the voltage of the film cell was tested using a multimeter. The results showed that the tensile strain occurred in both membrane batteries and PVC membrane at different loading levels, and the former was always less than the latter. At a tensile load with the ultimate load ratio of 60%, it was only at the film cell’s outer edge that the stripping occurred. Under the illumination of a stable light source, the film cell voltage decreased gradually with the increasing tensile load. No more than 10% of the cell voltage drop occurred when the membrane material, the principal tensile strain of the cell, and the cell’s expansion area ratio were less than 3.1%, 2.8%, and 1.03, respectively. The experimental results show that the film cell can be applied to the saddle membrane structure by controlling the appropriate load.

Assessment of Intravertebral Mechanical Strains and Cancellous Bone Texture Under Load Using a Clinically Available Digital Tomosynthesis Modality.

Vertebral fractures are the most common osteoporotic fractures, but clinical means for assessment of vertebral bone integrity are limited in accuracy, as they typically use surrogate measures that are indirectly related to mechanics. The objective of this study was to examine the extent to which intravertebral strain distributions and changes in cancellous bone texture generated by a load of physiological magnitude can be characterized using a clinically available imaging modality. We hypothesized that digital tomosynthesis-based digital volume correlation (DTS-DVC) and image texture-based metrics of cancellous bone microstructure can detect development of mechanical strains under load. Isolated cadaveric T11 vertebrae and L2-L4 vertebral segments were DTS imaged in a nonloaded state and under physiological load levels. Axial strain, maximum principal strain, maximum compressive and tensile principal strains, and von Mises equivalent strain were calculated using the DVC technique. The change in textural parameters (line fraction deviation, anisotropy, and fractal parameters) under load was calculated within the cancellous centrum. The effect of load on measured strains and texture variables was tested using mixed model analysis of variance, and relationships of strain and texture variables with donor age, bone density parameters, and bone size were examined using regression models. Magnitudes and heterogeneity of intravertebral strain measures correlated with applied loading and were significantly different from background noise. Image texture parameters were found to change with applied loading, but these changes were not observed in the second experiment testing L2-L4 segments. DTS-DVC-derived strains correlated with age more strongly than did bone mineral density (BMD) for T11.

Automated crack detection and measurement based on digital image correlation

The acquisition and evaluation of the crack behaviour in experiments on quasi-brittle materials, such as concrete, mortar, or masonry is essential for understanding their structural behaviour. This publication presents a fully automated procedure to detect cracks and measure crack kinematics in laboratory experiments instrumented with digital image correlation (DIC). Crack lines are extracted using well-established image processing methods showing excellent agreement with the physical crack pattern. In contrast to most existing crack detectors that rely on pixel intensities of true images, the presented crack detection is based on the DIC principal tensile strain field what allows the extraction of much finer cracks and more reliable crack locations. The crack widths and slips are measured using the DIC displacement field accounting for local rotations of the specimen. Additionally, automated visualisations of the crack kinematic measurements including data smoothing are presented. Several sensitivity analyses evaluating the performance and the uncertainty of the crack detector and the crack kinematic measurements have been conducted. These analyses show that the obtained results depend on the DIC configuration and that the procedure is limited in the case of very closely spaced cracks. With appropriate DIC parameters, the procedure allows detecting crack locations with high precision and measuring crack kinematics very accurately even in large-scale experiments with complex crack patterns.

Load transfer across a mandible during a mastication cycle: The effects of odontogenic tumour.

The extent to which load transfer in a diseased mandible with odontogenic tumour might influence the potential risk of pathological fracture has scarcely been investigated. The study sought to investigate the quantitative deviations in load transfer across healthy and cancer-affected (diseased) mandibles having odontogenic tumours. The effect of size of the tumours (small: 9 mm diameter, large: 19 mm diameter), and variation in bone mechanical (elastic) properties of the mandible on load transfer in cancer-affected mandibles during a mastication cycle have been investigated. Based on patient-specific computed tomography-scan datasets, detailed three-dimensional finite element models of healthy and diseased mandibles were developed. High stresses of 25-30 MPa and strains ∼700 µε were observed in the healthy mandible during the right molar bite. However, marginal deviations were observed in principal stress distributions in the diseased mandibles with small- and large-sized tumours, as compared to the healthy mandible. Maximum principal strains of ∼1474 µε were found in the body region adjacent to the symphysis region for small-sized tumour. Whereas for large-sized tumour, maximum strains of ∼2700 µε were observed in the right buccal regions. Reduction in Young's modulus due to different stages of odontogenic tumours had a localised effect on the principal stress distributions, but triggered an abrupt increase in the principal tensile strains. It appears that there is a potential risk of pathological fracture for large-sized odontogenic tumour, owing to high tensile stresses and strains.

Prediction on the plantar fascia strain offload upon Fascia taping and Low-Dye taping during running

BackgroundTaping is commonly prescribed to treat plantar fasciitis for runners by virtue of its alleged ability to offload the plantar fascia and facilitate positive injury prognosis. Our study aimed to investigate how different taping methods could change the loading on the plantar fascia during running using computational simulations. MethodsA finite element foot model was modified from a previous version to fit the study's purpose. The model featured twenty bones, bulk soft tissue, foot muscles, ligaments/tendons, and a solid part representing the plantar fascia. A runner performed several running trials under one untaped condition and two taped conditions—Low-Dye taping and Fascia taping, which were implemented by a physiotherapist using the Kinesio tapes. The captured motion data were processed to drive a scaled musculoskeletal model and calculate segmental kinematics, foot muscle force, and joint reaction force. These variables were then input as the boundary/loading conditions for finite element analyses of running. The principal tensile strain on the plantar fascia, subtalar eversion, and navicular height during the stance phase were averaged across five trials of each condition and compared using Friedman's test. ResultsMaximal subtalar eversion did not differ among conditions (p = 0.449). Fascia taping significantly reduced maximal strains on the fascia band (p = 0.034, Kendall's W = 0.64–0.76) and increased the navicular height (p = 0.013, Kendall's W = 0.84) compared with nontaping. There were no significant differences in all outcome variables between Low-Dye taping and nontaping (p = 0.173–0.618). ConclusionFrom a mechanical point of view, our study provided quantitative evidence to support the application of taping treatments for overstrained plantar fascia. The untensed fascia band by Fascia taping could be a potential indicator of pain relief for the runners. However, a prospective study targeting the patient population would be needed to address the point. The Translational Potential of this ArticleThe study quantified the loading status of the plantar fascia during running and provided mechanical evidence to support the usage of taping as a mean to reduce fascial strain, thus possibly controlling injury risks for the runners. The results of the study also highlighted the importance of selecting specific taping methods based on individuals' needs.

Triaxial Concrete Constitutive Model for Simulation of Composite Plate Shear Wall–Concrete Encased: THUC3

A new triaxial constitutive model [Tsinghua University Concrete Three-dimensional (THUC3)] of concrete was developed for high-fidelity finite-element (FE) simulation of composite plate shear wall–concrete encased (C-PSW/CE), which has been adopted as the lateral force-resisting system in numerous ultrahigh-rise buildings. In this formulation, a uniaxial constitutive model of concrete was introduced. The following five key features of concrete were included in the proposed model: compressive softening of unconfined and confined concrete, tension softening, pinching effect, shear softening, and strength degradation due to principal tensile strain. A triaxial constitutive law was also illustrated based on a fixed crack assumption. By assuming that the stress of the concrete can be decoupled in the crack coordinate system upon initial cracking, the triaxial constitutive law was assembled from the aforementioned uniaxial stress–strain relations. A new formulation is proposed to achieve strain decomposition and stress assembly in three-dimensional stress space. The numerical implementation of the stress update algorithm in an ABAQUS user material (UMAT) subroutine was illustrated. The modeling scheme and material constitutive laws of reinforcing bars, steel plates, and studs were also introduced. Subsequently, the developed triaxial constitutive model was validated at the material level by simulating the cyclic behavior of concrete and reinforced concrete (RC) specimens. The developed FE model showed good accuracy in simulating the hysteretic behavior, ultimate capacity, and residual strain in cyclic tensile loading. Two flexural critical C-PSW/CE tests, Specimens C30-5 and C40-5, were also completed and reported in this research, and 18 shear critical C-PSW/CE tests were collected from the existing literature. These tests were simulated to further validate the developed model at the structural level. Comparisons indicated that the proposed model showed a reasonable level of accuracy in terms of ultimate capacity, energy consumption, and failure mode. In addition, the modeling of studs by a nonlinear connector element is recommended based on comparisons between the test and FE results. The current AISC provisions for shear capacity of C-PSW/CE specimens were also evaluated relative to the computational and experimental results.

Image-based anatomical reconstruction and pharmaco-mediated bone remodeling model applied to a femur with subtrochanteric fracture: A subject-specific finite element study

Patient-specific finite element (FE) models are constructed in a way that boundary conditions, material and geometric FE models respect the unique characteristics of the patients, offering a more reliable and realistic structural analysis. This study presents an image-based construction process of a patient-specific FE model applied to a femur with a subtrochanteric fracture. Available procedures are systematized and described in greater depth aiming to investigate the difficulties and possibilities in the development of this type of model. A set of image processing techniques (segmentation, labeling, morphological operations and registering) were performed for volumetric reconstruction and registration of femoral fragments by assessing computed tomography (CT) images in a semi supervised procedure. The CT numbers feed the FE mesh with a non-homogeneous distribution of elasticity modulus. A FE analysis and a bone remodeling simulation with pharmacological stimulus based on the dynamics of bone cells populations were also developed for this study. The FE analysis revealed that the principal stresses provided results close to those obtained using a generic homogeneous model, with a difference of about 2%. In contrast, principal strains presented significant differences, up to 12 and 21 % for the maximum tensile and compressive principal strain values, respectively. The critical values of tensile principal strains were located in the superior part of the femoral neck, a typical region of femoral fractures, and maximum principal strains 2 and 3 (compressive) were concentrated in the diaphyseal region, rather close to the actual fracture. These results corroborate previous works indicating that the strain-based failure criterion is more successful in capturing the bone fracture sites when compared to stress-based criteria. The attempt to reconstruct the material state before the failure as implemented here constitutes an innovative way to analyze and reconstruct bone fractures. In the bone remodeling simulation, the inclusion of an antiresorptive agent stimulus produced cortical bone thickening, an increase in the BMD biomarker, and an overall increase in the bone ash density, just as expected in an osteoporosis therapeutic treatment. In conclusion, this study highlights the advantages of subject-specific FE models compared to generic ones in the study of abnormal clinical cases, evaluation of fracture risk, and optimization of surgical intervention. On the other hand, the high level of human intervention and expertise involved in patient-specific FE analyses hinders the incorporation of this technique into clinical practice.