Standard Strength Test Research Articles

Sifat Mekanik Komposit Serat Pelepah Kelapa Sawit sebagai Penguat Komposit Terhadap Kekuatan Tarik dan Impak

Palm fronds are solid waste from oil palm plantations that contain a lot of natural fibers. One of the utilization efforts that can be done is to optimize palm frond fiber waste into composite materials. The use of natural fiber mixtures in composites has produced stronger materials, which can serve as alternative materials for car bumpers. This research was conducted with the aim of knowing the value of impact toughness, tensile strength, and the type of failure that occurs in the fracture cross section. In this study, composites were made using palm frond fibers and polyester resin. The volume fraction variation applied is 30% fiber and 70% matrix with fiber lengths of 20 mm, 40 mm, and 60 mm. Impact toughness testing refers to ASTM E23 standard and tensile strength testing refers to ASTM D638 standard. The impact toughness value obtained in the 20 mm variation was 0.0065 J/mm², 40 mm was 0.0108 J/mm², and the 60 mm variation had the highest value of 0.0164 J/mm². The tensile strength value obtained in the 20 mm variation is 6.18 MPa, the 40 mm variation is 8.26 MPa, and the 60 mm variation has the highest value of 16.45 MPa. Analysis of the fracture cross section is categorized as a splitting fracture in multiple areas and the fracture cross section also shows the occurrence of fiber pull out after the fracture.

Effects of Different Test Positions on Quantitative Muscle Strength of Wrist and Finger Flexor Muscle Groups and Its Standardization.

To explore the effects of different test positions on quantitative muscle strength of wrist and finger flexor muscle groups and to establish a standardized muscle strength test protocol for each muscle group. Forty healthy subjects (12 males and 28 females) were recruited. A portable digital quantitative muscle strength tester, Micro FET2TM, was used to measure the flexor muscle strength of each finger and the wrist joint at the 30° extension, 0° neutral, and 30° flexion, respectively. Palmar abduction strength of the thumb was measured at 30° and 60°, respectively. Ten subjects were randomly selected from the 40 subjects, and the quantitative muscle strength of each muscle group was tested again by the same operator after an interval of 10 to 15 days. Except for the fact that in males, there was no significant difference in flexor muscle strength of thumb and wrist joint between 30° of wrist extension and neutral 0° position, the muscle strength of the other fingers flexion and wrist palmar flexor showed the following characteristics：30° of wrist extension > neutral 0° position > 30° of flexion, and the PAST was 30°>60°; The flexor muscle strength of all the subjects was thumb > index finger > middle finger > ring finger > little finger; All muscle strength values of male were greater than those of female, and the difference was statistically significant (P<0.05); There was no significant difference between the left and right side muscle strength values of all subjects (P>0.05). The reliability of muscle strength values measured at different times in 10 subjects was good. The quantitative muscle strength of each muscle group of the hand and wrist is affected by the test position, and a standardized and uniformed test position should be adopted in the actual identification. Micro FET2TM has good reliability for hand and wrist quantitative muscle strength testing. The 30° extension of the wrist can be used as the best standardized test position for the flexion muscle strength of each finger and wrist joint. The 30° position can be used as the best standardized test position for PAST.

Microfabrics impact on rock salt geomechanical diversity – an experimental investigation

Geomechanical studies of rock salt serve as the foundation for designing and ensuring the long-term stability of storage caverns. Research conducted in recent years has shown that rock salt exhibit highly variable mechanical parameters. Even macroscopically similar rock salt samples from the same formation have very different mechanical parameters in standard strength tests. In this paper, the effect of microfabrics on the mechanical behaviour of rock salt was studied using a uniaxial compression device with simultaneous observation under a microscope. The tests were carried out on rock salt samples, previously tested on standard uniaxial compression (UCS). Tested samples showed different strength values despite macroscopic similarity and similar anhydrite content. The tests revealed that the microfabrics, such as fluid inclusions and anhydrite crystals distributed along the halite grain boundaries, play a significant role in the strength of a rock salt sample. Four types of grain boundaries were recognized in both group of samples: (1) dominated by anhydrite crystals with a small number of fluid inclusions (FIs), (2) with FIs prevailing over anhydrite crystals, (3) only with FIs, and (4) without anhydrite crystals or FIs. The experimental uniaxial compression tests in microscale (mUCS) showed that the damage process is initiated by FIs activity at the halite grain boundaries and consists of three main stages. The samples dominated by anhydrite crystals at halite grain boundaries were characterised by the highest mUCS. Conversely, if FIs prevail at the grain boundaries the lowest mUCS values were registered. Therefore, anhydrite crystals located along halite grain boundaries influenced the mechanical behaviour and deformation process. On the contrary, anhydrite crystals dispersed within halite grains had no impact on failure and mechanical parameters. The experiment showed that apart from impurity content, the distribution of these impurities within halite grains should be examined during geomechanical evaluation of rock salt samples. Thus, the overall strength of rock salt samples determined in standard test results from the local variations of petrological features in micro- and macro scale.

Small-scale laboratory tests for quantifying aggregate interlocking in short-panelled concrete pavements

In the present study, a simple and reliabe small-scale laboratory test to assess the performance of aggregate interlocked joints in short-panelled concrete pavements in terms of LTE is proposed. In the proposed test method, conventional standard flexural strength test beam specimens (100×100× 500mm) are used for understanding the performance of aggregate interlocking of PQC mix specimens prepared using coarse aggregates of different NMAS and with addition of both micro and macro fibers. The test setup is also modelled in ANSYS FE software. The experimentally obtained LTE is compared with the LTE obtained from the FE model. The field FWD test is conducted for validation. The relative movement is determined from FWD test, and corresponding LTE is determined using the LTE and RM relationship obtained from experimental results using the proposed test apparatus. There exists good linear fit between the LTE determined using proposed test and field FWD test results.

Hydration behavior and microstructure of cement-based materials modified by Field’s metal particles

The hydration of cement-based materials, especially at early ages, directly affects the development of matrix strength and the later durability. In this paper, in order to explore the hydration behavior and microstructure of cement-based composites modified by low melting point Field's Metal Particles (FMP), inverted cone method, standard Vicatometer method, isothermal calorimetry, and compressive strength test, TGA, SEM, and XRD are used to investigate the fresh properties, heat of hydration, matrix strength, hydration products and transition zone between FMP and cement matrix. The results show that the incorporation of FMP can improve the fluidity of cementitious composites by 31.6%, due to the hydrophilicity of FMP. Meanwhile, due to the small heat capacity and large thermal conductivity of low-melting FMP, the heat stored in FMP is naturally released and used to promote hydration reaction when the hydration rate slows down. Additionally, FMP does not affect the types of hydration products in cement-based composites, but the total amount of hydration products increased at 7 d, especially calcium hydroxide (CH). Unexpectedly, FMP can reduce the compressive strength of the hardened paste, due to the large particle size of FMP than cement particles and the presence of directionally growing CH crystals in the interface transition zone between FMP and cement matrix.

Influence of Groundnut Shell Powder on Normal Concrete's Split Tensile Strength

Groundnut shell powder contains significant amounts of the chemical silica (SiO) to be utilized as construction materials. Through the use of groundnut shell powder, this study seeks to determine the split tensile strength of concrete (GSP). With a compressive strength design of f'c =21.7 MPa, the concrete mixture adheres to ACI 2I1.1-91. The aggregate of crushed stone with a maximum diameter of 19.1 mm. Portland cement type I is the type of cement utilized. With a variation of 0%, 5%, 7,5%, 10%, and 12.5%, additional material (GSP) substitutes cement in part. At 14 and 28 days old, concrete is tested for its tensile strength. For each modification, there are three cylindrical test objects, each measuring 30 cm in length and 15 cm in diameter. The split tensile strength of concrete was tested using 14-day-old peanut shell powder, and the results were 1,699 MPa, 1,840 MPa, 1,581 MPa, and 1,510 MPa, respectively. The findings demonstrated that concrete's split tensile strength (f'ct) was 28 days with a fluctuation of 0%; 5%; 7,5%; 10%; and the sequential 12.5% was 1,934; 2,170; 2.265; 1,958; and 1,887 Mpa. Following the findings, the ideal tensile strength value was at a variation of 7.5%, or 2,265 MPa, greater than 0% (1,934 MPa) of 17.11%. The age of 28 days was 7.5% higher than the age of 14 days (1,840 MPa) of 23.10% for the variation's maximum tensile strength. Compared to standard compressive strength test findings, the Split tensile strength value of concrete utilizing GSP is 6.83%

The interaction of loading mode and humidity on the properties degradation of an epoxy adhesive subjected to strength, fracture, and fatigue tests

AbstractHygrothermal aging has a significant impact on the performance of adhesives and bonded joints. However, despite extensive investigations into the aging effect of bonded structures, there is still limited knowledge on how aging affects joint performance as a function of the loading type and the load angle. Accordingly, in this study, an epoxy adhesive was tested under different loading types/angles including tensile and shear standard strength tests, mode I and mode II fracture tests, and fatigue and static Arcan tests. All these experiments were performed for both aged and unaged conditions. To understand the influence of loading angle on the failure response of aged bonded joints, Arcan samples were subjected to mixed mode loading conditions as well. A fractography analysis was conducted to provide a better understanding of the failure mechanism of aged samples loaded at different modes. Based on these results, it was found that mode I (tensile loading conditions) is more sensitive to the aging conditions than mode II (shearing) for all loading types (strength, fracture, and fatigue tests). The influence of moisture on fracture toughness was however less relevant than the strength. The results also showed that for the same loading mode and for the same Arcan joints, the fatigue strength is significantly more degraded by the aging conditions than the static strength.

Analysis of vehicle tire strength test

An experimental investigation is conducted to study the plunger test which represents the standard strength test for vehicle tires. Five different models of main brands are examined. The effect of applied load and internal pressure on the breaking energy of the tire are studied. Standard tensile tests are conducted on the same models to investigate the modes of failure of different specimens and the correlation between both tests.It was found that the increase of the internal pressure leads to a linear decrease in braking energy for all brands. The breaking energy was affected by the viscoelastic behavior of the rubbery components of the tire after the breakdown of the strengthening wires. Using statistical analysis, a correlation was found between the braking energy and the ratio between the elastic modulus and the tensile strength of the tire. This numerical correlation can be used by designers to simulate and predict the performance of the tire at different strength tests. On the other hand, the breaking energy was inversely related to the strain energy density.

A Systematic Review and Meta-Analysis of Strength Recovery Measured by Isokinetic Dynamometer Technology after Anterior Cruciate Ligament Reconstruction Using Quadriceps Tendon Autografts vs. Hamstring Tendon Autografts or Patellar Tendon Autografts.

Background: This systematic review and meta-analysis compared the isokinetic strength of the muscular knee joint between quadriceps tendon autografts (QTAs) and hamstring tendon autografts (HTAs) or patellar tendon autografts (PTAs) after anterior cruciate ligament (ACL) reconstruction by determining the isokinetic angular velocity and follow-up time points. The functional outcomes and knee stability at the same time points were also compared using isokinetic technology. Methods: Two independent reviewers searched the Medline (via PubMed search engine), Scopus, Web of Science and Cochrane Library databases to include full text comparative studies that assessed isokinetic strength test following ACL reconstruction. The DerSimonian and Laird method was used. Results: In total, ten studies were included; seven compared studies QTAs vs. HTAs, and three compared QTAs vs. PTAs. Five studies were included in the meta-analysis. Isokinetic strength data were reported 3, 6, 12 and 24 months after ACL reconstruction. Conclusions: The QTAs showed better and significant results with knee flexion compared with HTAs, similar results to PTAs at 6 and 12 months. While HTAs showed better and significant results with knee extension at 6 months and similar results at 12 months compared to QTAs. Furthermore, a standardized isokinetic strength test must be followed to achieve a more specific conclusion and better clinical comparison among participants.

Long-Term Protective Effect of Human Dystrophin Expressing Chimeric (DEC) Cell Therapy on Amelioration of Function of Cardiac, Respiratory and Skeletal Muscles in Duchenne Muscular Dystrophy

Duchenne Muscular Dystrophy (DMD) is a lethal disease caused by mutations in dystrophin encoding gene, causing progressive degeneration of cardiac, respiratory, and skeletal muscles leading to premature death due to cardiac and respiratory failure. Currently, there is no cure for DMD. Therefore, novel therapeutic approaches are needed for DMD patients.We have previously reported functional improvements which correlated with increased dystrophin expression following administration of dystrophin expressing chimeric (DEC) cells of myoblast origin to the mdx mouse models of DMD.In the current study, we confirmed dose-dependent protective effect of human DEC therapy created from myoblasts of normal and DMD-affected donors, on restoration of dystrophin expression and amelioration of cardiac, respiratory, and skeletal muscle function at 180 days after systemic-intraosseous DEC administration to mdx/scid mouse model of DMD. Functional improvements included maintenance of ejection fraction and fractional shortening levels on echocardiography, reduced enhanced pause and expiration time on plethysmography and improved grip strength and maximum stretch induced contraction of skeletal muscles. Improved function was associated with amelioration of mdx muscle pathology revealed by reduced muscle fibrosis, reduced inflammation and improved muscle morphology confirmed by reduced number of centrally nucleated fibers and normalization of muscle fiber diameters. Our findings confirm the long-term systemic effect of DEC therapy in the most severely affected by DMD organs including heart, diaphragm, and long skeletal muscles.These encouraging preclinical data introduces human DEC as a novel therapeutic modality of Advanced Therapy Medicinal Product (ATMP) with the potential to improve or halt the progression of DMD and enhance quality of life of DMD patients.Graphical Human DEC as a novel therapeutic modality with the potential to improve or halt progression of the DMD disease and enhance quality of life of DMD patients. Graphical abstract represents manufacturing process of the human DEC therapy for the future clinical applications. 1. We report the long-term efficacy of human DEC therapy resulting in increased dystrophin expression and reduced mdx muscle pathology after systemic-intraosseous administration of human Dystrophin Expressing Chimeric (DEC) Cells to the mdx/scid mouse model of DMD. 2. Systemic administration of human DEC therapy resulted in amelioration of cardiac, respiratory and skeletal muscle function as confirmed by echocardiography, plethysmography and standard muscle strength tests respectively. 3. We introduce human DEC as a novel Advanced Therapy Medicinal Product (ATMP) for future clinical application in DMD patients.

Improvement of lateritic soil using shredded plastic bottles for road construction in Jos-South, Plateau State of Nigeria

Some geotechnical properties of lateritic soil treated with plastic shred were assessed. The test method employed involves treating lateritic soil with Plastic shreds in the percentages of 0%, 0.5%, 1.0%, 1.5%, and 2.0% by dry weight of soil. Test carried out include preliminary test, compaction test using British Standard light (BSL) and Unconfined compressive strength (UCS) test and shear strength test. One-way analysis of variance (ANOVA) and Regression Analysis was carried out using Microsoft Office Excel software. Percentage passing BS No 200 sieve (%) was 19.34. The MDD initially increased from its natural value of 1.70 Mg/m3 to 1.77 Mg/m3 at 0.5% PS content, while OMC increased with increase in PS. The UCS increased from 51 kN/m2 for the natural soil to 72 kN/m2 at 0.5% shredded plastic content and thereafter, a decrease in UCS was observed with further increase in the percentage of shredded plastic (1%, 1.5%, and 2%). The angle of internal friction increased by about 11% and the cohesion coefficient increased by 12%; bearing capacity increased generally with an increase in PS from 147 kN/m2 natural to 215 kN/m2 at 2%. ANOVA analysis shows that shredded plastic has a significant effect on the treated lateritic soil. Based on the result obtained, an optimal 2% of PS content improved the index and strength characteristics of the treated soil and is recommended for geotechnical engineering application based on regulatory standards.

Midterm outcome and strength assessment after quadriceps tendon refixation with suture anchors

PurposeQuadriceps tendon ruptures (QTR) occur predominantly in middle-aged patients through violent eccentric contraction that occurs either when trying to regain balance or during a fall on the hyperflexed knee. The aim of this study was to quantify midterm postoperative results, including strength potential measured via standardized strength tests following acute (< six weeks) quadriceps tendon refixation using suture anchors.MethodsAll consecutive patients with QTR who underwent surgical suture anchor refixation between 2012 and 2019 at a single institution with a minimum follow-up of 12 months were retrospectively evaluated. Outcome measures included Tegner Activity Scale (TAS), Lysholm score, International Knee Documentation Committee subjective knee form (IKDC), Knee injury and Osteoarthritis Outcome Score (KOOS) subscales, return to work rates, and Visual Analog Scale (VAS) for pain. Additionally, a standardized clinical examination and an isometric strength assessment of knee extension and flexion were performed.ResultsA total of 17 patients (median age 61.0 [25–75% IQR 50.5–72.5]) were available for final assessment at a mean follow-up of 47.1 ± SD 25.4 months. The majority of patients were male (82.4%) and most injuries occurred due to a fall on the hyperflexed knee (76.5%). The average time interval between trauma and surgery was 12.7 ± 7.5 days. Patients achieved a moderate level of activity postoperatively with a median TAS of 4 (3–5.5) and reported good to excellent outcome scores (Lysholm score: 97 (86.5–100); IKDC: 80.7 ± 13.5; KOOS subscales: pain 97.2 (93.1–100), symptoms 92.9 (82.5–100), activities of daily living 97.1 (93.4–100), sport and recreation function 80 (40–97.5) and knee-related quality of life 87.5 (62.5–100). All patients were able to fully return to work and reported little pain [VAS: 0 (0–0)]. No postoperative complications were reported. Strength measurements revealed a significant deficit of knee extension strength in comparison to the contralateral side (p = 0.011).ConclusionSuture anchor refixation of acute QTR leads to good functional results and high patient satisfaction without major complications. Isometric knee extension strength, however, may not be fully restored compared to the unaffected side.

Mechanical reinforcement of 3D printed cordierite-zirconia composites

In this study, composite ceramic slurries based on submicron-micron-sized cordierite-zirconia were prepared with varied zirconia content. Standard bending strength and fracture toughness testing samples were directly designed and fabricated using stereolithography 3D printing followed by different sintering schemes to study the mechanical reinforcement effect. The physical compositions and microstructures of the samples were characterized. The additively manufactured cordierite-zirconia composites exhibit excellent mechanical properties. Maximum measured bending strength (136 MPa) and fracture toughness (1.8 MPa m1/2) were reached by adding 2 wt% and 6 wt% zirconia, namely an increase of 44% and 66% relative to pure cordierite, respectively. The strengthening and toughening mechanisms of the composites were further explained mainly by microstructural analysis. This study provides an alternative and direct design and manufacturing method for the mechanical measurement and reinforcement of ceramic composite parts based on the use of 3D printing technology.

Technical feasibility of producing binder-free water hyacinth briquettes for domestic energy use

Production of biomass briquettes of good strength and combustion characteristics usually requires the addition of a binder material to the feedstock. This study was aimed at developing a methodology for producing briquettes from water hyacinth at low compression pressures without using a binder material. Fresh water hyacinth was chopped to a maximum length of 3 cm, sun-dried to a moisture content of about 10%, mixed with shredded waste office paper in four water hyacinth to paper proportions on weight basis (100:0, 90:10, 80:20 and 70:30). The mixtures were soaked in water for three days and briquetted using a 6-cylinder screw briquetting machine. The resulting briquettes were subjected to standard strength and combustion tests. A Completely Randomized Design with four treatments replicated five times was used as the experimental design. Results from the study indicate no significant differences in compressed density, relaxed density, relaxation ratio and calorific value between the briquettes. The results further indicate that briquettes made without a binder material have significantly low but adequate shatter resistance, low ignition time, high burning rate and take a longer time to bring water to boil. It can be concluded that good quality water hyacinth briquettes can be produced at low compression pressures without using a binder material. This methodology can potentially increase adoption of water hyacinth briquettes in areas with poor access to binder materials. The originality of the research is the development of a water hyacinth briquetting methodology that does not use binder materials.

Knee Extensor Mechanism Strength and Its Relationship to Patellofemoral Kinematics in Individuals With Arthrofibrosis Within 6Months After Anterior Cruciate Ligament Reconstruction.

Performance in strength and assessment of patellar tracking is important for patients with arthrofibrosis after anterior cruciate ligament (ACL) reconstruction. The study was to examine the difference of patellofemoral kinematics between the affected and the contralateral limb and to evaluate the relationship between knee extensor strength and patellofemoral kinematics in patients with arthrofibrosis after ACL reconstruction. Cohort study (diagnosis); level of evidence, 3. Laboratory. A prospective cohort of 20 patients with arthrofibrosis after ACL reconstruction was recruited. A total of 20 patients who underwent arthroscopic reconstruction of the double-bundle ACL with a hamstring tendon autograft received standardized patellofemoral kinematics testing and knee extensor strength testing within 6months after primary ACL reconstruction. Computed tomography and dual fluoroscopic imaging were used to evaluate in vivo patellofemoral kinematics of affected and contralateral knees during a lunge task. Knee extensor mechanism strength was measured using a handheld dynamometer. A limb symmetry index of knee strength and patellar mobility was calculated and satisfactory performance defined as ≥90%. There was a statistically significant decrease in the range of patellar inferior shift (P = .020; d = 0.81), flexion (P = .026; d = 0.95), lateral tilt (P = .001; d = 1.04), and lateral rotation (P < .001; d = 0.89) in the affected knee compared with the contralateral knee from 15° to 75° of knee flexion. There was a strong positive linear correlation between knee extensor strength and patellar inferior shift (r = .747; P = .008). A knee extensor strength limb symmetry index <90% was 89% sensitive and 9% specific for limited patellar inferior shift. Patients with arthrofibrosis after ACL reconstruction presented decreased patellar mobility in the arthrofibrotic knee compared with the contralateral knee. The strong correlation between knee extensor strength and patellar inferior shift of the arthrofibrotic knee demonstrates the importance of knee extensor strength in the diagnosis and treatment of patients with knee arthrofibrosis. The knee extensor mechanism strength has high sensitivity but low specificity in identifying a decrease in patellar inferior shift in patients with arthrofibrosis after ACL reconstruction.

Estimation of Post-Cracking Dissipation Capabilities of Fiber Reinforced Concretes in Three Point Bending Test Monitored with Application of Digital Image Correlation System.

Concretes with dispersed reinforcement are increasingly used in structural engineering. The basic source of knowledge on their application and design are the Model-Code 2010 guidelines. These guidelines, however, apply mainly to steel rebar reinforcement and are not fully sufficient in the analysis of the load-bearing capacity of elements made of concrete with dispersed reinforcement. Therefore, scientific research in this field is carried out continuously. The main goal of our work is to provide experimental data for the calibration of constitutive models of the cracking mechanics of concrete with reinforcement in the form of steel and polypropylene fibers. This article shows the possibility of using the digital image correlation system (DIC) to achieve this goal. The method of sample preparation and the method of conducting the tests were modeled on the recommendations contained in the PN-EN 14651: 2007 standard. The tests were carried out on prismatic elements with a notch loaded in a three-point bending setup. The results of standard strength tests are presented in the form of column graphs and tables. As an extension, the results of calculations of energy dissipated in fracture process are given. Moreover, the experimentally obtained graphs of the relationship between the force, displacement and crack opening were presented, which were supplemented with the images of crack development obtained with the use of DIC. The development of the crack net is characterized not only qualitatively but also quantitatively as a function of deflection or crack mouth opening displacement. Conclusions concerning the adopted research methodology and the tested materials are presented at the end of the article.

EARLY STRENGTH TESTING AFTER ACL RECONSTRUCTION IMPACTS ISOKINETIC STRENGTH PERFORMANCE AT TIME OF RETURN TO SPORT

Background:The standard of care in ACL reconstruction (ACLR) typically involves standardized strength testing at 6 months or later to assess a patient’s readiness to return to play (RTP) using isokinetic and isometric testing, and functional strength testing. Recent literature suggests that isokinetic knee extension strength should demonstrate 89% limb symmetry index (LSI) or greater prior to returning to sport. However, there is little known on the effects of strength testing early in the rehabilitation process and the relationship to strength test performance at time of RTP.Purpose:The purpose of this study was to examine how early post-operative strength test performance impacts isokinetic strength outcomes at RTP testing in adolescents.Methods:The retrospective cohort study included patients undergoing primary ACLR between 12 and 18 years of age, early post-operative strength measures, and isokinetic dynamometer strength at RTP from July 2017 and April 2019. Data was dichotomized into desired outcomes at 3 months: >70% isometric knee extension LSI, > 20 repetitions on anterior stepdown test (AST), > 90% LSI Y Balance. At RTP testing, isokinetic knee extension strength data was categorized into >89% LSI at 3 speeds (300, 180, 60°/sec). Chi square testing and odds ratio statistics were used to examine association and its magnitude.Results:63 patients met inclusion criteria (38 females; 15.37±1.66 years old). >70% LSI isometric knee extension strength at 3 months showed a significant association (Table 2) and demonstrated the strongest odds of having >89% LSI on isokinetic strength tests at all 3 speeds at RTP with 180°/sec being the highest (OR=14.5; 95% CI=4.25,49.43; p= <0.001). Performance on AST showed a significant association (χ2 (1, n=63) = 17.00, p <0.001), and highest odds at 180°/sec (OR=4.61; 95% CI = 1.59, 13.39, p=<0.001) and 60°/sec (OR= 3.07; 95% CI = 1.10, 8.63, p= 0.04). Combination of performance on isometric strength tests and AST showed a significant association to isokinetic strength at all three speeds, but less predictive then isometrics in isolation. (Table 2). There was no significant relationship between YBR LSI at 3 months and isokinetic strength at 6 months.Conclusion:Standardized strength testing early in rehabilitation can help identify patients that will successfully complete RTP testing. Our results suggest that isometric knee extension strength and timed anterior stepdown test provide meaningful clinical information early in the rehabilitation process. This data also suggests that the use of YBAL for predicting isokinetic strength performance is limited.

Evaluation of Site Variability Effect on the Geotechnical Data and Its Application

Abstract This study focused on evaluating the laboratory measurement errors and site variability due to soil deposition and operator using the following tests: unconsolidated-undrained (UU), Atterberg limits, small direct shear, and California bearing ratio (CBR) tests. Four clay soils with different plasticity indexes (PIs) were tested in the laboratory (PI = 11, 21, 38, 53), in addition to sandy soil and 3 aggregate base materials. Five different operators tested three specimens for each soil type to investigate the effect of operator on testing results. The maximum coefficient of variation (COV) data due to operator were 10.9 %, 7.8 %, 18.2 %, 16.9 %, 19.5 %, and 15.6 % for UU, liquid limit, plastic limit, plasticity index, direct shear, and CBR tests, respectively. The effect of operator and equipment on field testing results was evaluated using 28 cone penetration tests (CPTs) points performed in the same site at different times by two contractors. The spatial variability of CPT data was evaluated for each contactor and both combined. The values of COV for CPT data were different for the two contractors. The average COVs of pile design method and site variability were used to calibrate the Load Resistance Factor Design (LRFD) resistance factor, Φ, which showed high value for lower variability data, and vice versa for high variability data. The operator and equipment variabilities caused Φ to reach 0.24 for CPT data. In addition, the standard penetration test (SPT) and unconfined compressive strength test (qu) were collected from 21 borings and used to evaluate site variability. The value of Φ increased from 0.41, when COV of pile design method was only included, to 0.55, when site variability was included for SPT data. The same scenario was done for qu, in which Φ was increased from 0.34 when including COV of pile design method only to 0.39 when using the average COV of both method and site.

Application of Particle Stiffness Fabric Tensor for Modeling Inherent Anisotropy in Rocks

The mechanical behavior of geo-materials depends on the assemblage structure and fundamental characteristics of constituting particles such as their shape, size and mechanical properties. Anisotropy is an intrinsic macroscopic material property that quantifies the differences in mechanical resistances to loading directions. In this study, the discrete element method (DEM) is used to investigate the anisotropic behavior of geo-materials like rocks. The model considers a fabric tensor characterizing the internal structure of particles associated with the anisotropy. The new fabric tensor proposed in this research is termed the particle stiffness fabric tensor (P-S fabric), which associates the stiffness (k in the traditional DEM) with the anisotropic state parameters. The results show that the discrete nature of the proposed approach allows an effective modelling of the anisotropic behavior of rocks. Numerical experiments are conducted on standard Brazilian tensile strength (BTS) tests with different anisotropic configurations using the PFC2D code. The tensile strength obtained shows that the results based on the proposed particle stiffness fabric tensor have a much better agreement with experimental results compared with conventional numerical modelling approaches.

Handgrip Strength as a Complementary Test for Mobility Limitations Assessment in Acutely Hospitalized Oldest Old.

Clinically viable screening tools for detecting individuals at heightened risk for mobility limitations is warranted. However, it remains unclear in acutely hospitalized patients (>75 years) whether handgrip strength might be a good predictor for "proxy" muscle strength. To examine the reliability and validity of handgrip strength test in acute hospitalized older adults in comparison with other standardized muscular strength tests, and to examine its ability to discriminate between presence and absence of mobility limitations. Cross-sectional study. A total of 234 patients (mean age 87.0 years, 46% women) admitted to a tertiary public hospital between 2016 and 2017 were recruited. Maximal (one repetition maximum) and power muscle output of the upper and lower extremity along with functional capacity (as assessed with Barthel index and the Short Physical Performance Battery [SPPB]), and cognitive function was measured at admission. Functional impairment (mobility limitations) was defined at SPPB ≤7 points. Pearson's correlation and multivariable linear regression were evaluated between handgrip test and maximal and muscle power output as the reference method to assess concurrent validity. Receiver operating characteristic analysis was used to estimate handgrip strength cutoff point for likelihood of mobility limitations to assess predictive validity. Findings show moderate-to-strong correlations between standardized muscular strength (reference methods) and handgrip strength test (r = 0.534-0.725). All muscular strength tests show moderate accuracy (area under curve >0.7). Handgrip strength shows the higher positive predictive value (87%) and, therefore, a lower number of false positives. The overall handgrip strength cutoff point for likelihood of mobility limitations was 18.4 kg for men and women. Handgrip strength may be a useful tool for detecting acutely hospitalized older who are at risk of mobility limitations and could aid in focusing interventions on those with higher risk. Randomized clinical trial: NCT02300896.