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1
Zheng, Guozhi, Naitian Zhang, and Songtao Lv. "The Application of Fractional Derivative Viscoelastic Models in the Finite Element Method: Taking Several Common Models as Examples." Fractal and Fractional 8, no. 2 (2024): 103. http://dx.doi.org/10.3390/fractalfract8020103.
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This paper aims to incorporate the fractional derivative viscoelastic model into a finite element analysis. Firstly, based on the constitutive equation of the fractional derivative three-parameter solid model (FTS), the constitutive equation is discretized by using the Grünwald–Letnikov definition of the fractional derivative, and the stress increment and strain increment relationship and Jacobian matrix are obtained by using the difference method. Subsequently, we degrade the model to establish stress increment and strain increment relationships and Jacobian matrices for the fractional derivative Kelvin model (FK) and fractional derivative Maxwell model (FM). Finally, we further degrade the fractional derivative viscoelastic model to derive stress increment and strain increment relationships and Jacobian matrices for a three-component solid model and Kelvin and Maxwell models. Based on these developments, a UMAT subroutine is implemented in ABAQUS 6.14 finite element software. Three different loading modes, including static load, dynamic load, and mobile load, are analyzed and calculated. The calculations primarily involve a convergence analysis, verification of numerical solutions, and comparative analysis of responses among different viscoelastic models.
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Sayed, Ahmed M. "Numerical Analysis of the Perforated Steel Sheets Under Uni-Axial Tensile Force." Metals 9, no. 6 (2019): 632. http://dx.doi.org/10.3390/met9060632.
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The perforated steel sheets have many uses, so they should be studied under the influence of the uniaxial tensile load. The presence of these holes in the steel sheets certainly affects the mechanical properties. This paper aims at studying the behavior of the stress-strain engineering relationships of the perforated steel sheets. To achieve this, the three-dimensional finite element (FE) model is mainly designed to investigate the effect of this condition. Experimental tests were carried out on solid specimens to be used in the test of model accuracy of the FE simulation. Simulation testing shows that the FE modeling revealed the ability to calculate the stress-strain engineering relationships of perforated steel sheets. It can be concluded that the effect of a perforated rhombus shape is greater than the others, and perforated square shape has no effect on the stress-strain engineering relationships. The efficiency of the perforated staggered or linearly distribution shapes with the actual net area on the applied loads has the opposite effect, as it reduces the load capacity for all types of perforated shapes. Despite the decrease in load capacity, it improves the properties of the steel sheets.
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Wang, Yunyang, Shengwei Sun, Liqing Zhang, and Yandong Jia. "Compressive Behaviors of Thin-Walled Steel Tube Stub Columns Filled with Self-Compacting Concrete Containing Recycled Aggregate." Materials 16, no. 18 (2023): 6088. http://dx.doi.org/10.3390/ma16186088.
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Natural resources have been excessively consumed, and large amounts of construction wastes have been generated, owing to the fast development of civil industry, causing crucial environmental issues. Therefore, reusable construction waste fabricated into recycled concrete offers a good strategy to solve this issue. Thus, this article first develops thin-walled steel tubes stub columns filled with self-compacting concrete containing recycled coarse aggregate. Afterwards, the compressive behaviors of the columns when undergoing axial compression loading to failure are explored. Subsequently, the effect of types of self-compacting concrete and wall thickness on failure modes and the relationships between load and displacement/strain is discussed comprehensively. Moreover, models of load–displacement/strain behaviors are proposed. The results show that columns with identical wall thicknesses containing both natural and recycled coarse aggregate display similar failure modes, mainly presenting as local buckling and rupture. The shape of the load–displacement/strain curves for identical wall thicknesses are almost the same. Nevertheless, the maximum load and stiffness of columns containing recycled coarse aggregate are lower than those of columns containing natural coarse aggregate. Additionally, the maximum loads corresponding to wall thickness of 1.2 mm and 3.0 mm are decreased by 18.4% and 5.8%, respectively. Moreover, the proposed models can reasonably evaluate the relationships between load and displacement/strain. This paper demonstrates that thin-walled steel tubular columns containing recycled coarse aggregate present positive compressive behaviors and thus exhibit great potential for developing environmentally friendly and sustainable civil infrastructures.
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Ding, Fa Xing, Zhi Wu Yu, and Jin Ping Ou. "Elasto-Plastic Analysis of Concrete-Filled Circular Steel Tubular Stub Columns after Exposed to High Temperatures." Key Engineering Materials 400-402 (October 2008): 763–68. http://dx.doi.org/10.4028/www.scientific.net/kem.400-402.763.
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Based on the research achievements of the mechanical properties of concrete at uniaxial compression and steel at uniaxial tension after exposed to high temperatures, the axisymmetric- triaxial-compressive stress-strain relationships of concrete and multiaxial stress-strain relationships of steel after exposed to high temperatures was suggested. Based on continuum mechanics, the mechanical model of concentric cylinders of circular steel tube with concrete core of entire section loaded after exposed to high temperature was determined. By applying Elasto-Plastic Analysis Method, theoretical calculation formulas for composite elastic modulus and composite stress-strain relationships of concrete-filled circular steel tubular (CFST) stub columns were proposed and a FORTRAN program was developed and the load-axial strain relationships of CFST stub columns after exposed to high temperatures were analyzed. The analysis results were in reasonable agreement with the experiment ones from references.
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Stich, Jean-Francois, Monideepa Tarafdar, Patrick Stacey, and Cary L. Cooper. "E-mail load, workload stress and desired e-mail load: a cybernetic approach." Information Technology & People 32, no. 2 (2019): 430–52. http://dx.doi.org/10.1108/itp-10-2017-0321.
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PurposeUsing e-mail is a time-consuming activity that can increase workload stress. The purpose of this paper is to investigate the relationship between the individual’s e-mail load, workload stress and desired e-mail load, drawing from the cybernetic theory of stress.Design/methodology/approachBased on prior theory, the authors first hypothesized relationships among e-mail load, workplace stress and desired e-mail load. The authors then tested these relationships on a sample of 504 full-time workers in the USA, using survey data and covariance-based structural equation modeling techniques.FindingsThe authors find that higher e-mail load is associated with higher workload stress; higher workload stress is associated with lower desired e-mail load; lower desired e-mail load is associated with lower e-mail load; and higher workload stress is associated with higher psychological strain, higher negative emotions and lower organizational commitment.Originality/valueThe study provides a novel understanding of workload stress due to e-mail load, through the lens of cybernetic theory. It contributes to the e-mail overload and technostress literatures by conceptualizing desired e-mail load as a potential outcome of workplace stress and as a regulator for e-mail load. For practitioners, the study highlights the importance of managing employees’ e-mail load to prevent the negative effects of workplace stress and associated strains.
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Jia, Hui Ji, Lian Fa Yang, and Jian Wei Liu. "Establishment of Stress-Strain Relationships of Tailor-Welded Tubes via DIC Method Based on Uniaxial Tensile Tests." Key Engineering Materials 611-612 (May 2014): 475–82. http://dx.doi.org/10.4028/www.scientific.net/kem.611-612.475.
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Tailor-welded tubes are widespread in aircraft and automotive industries due to their advantages of low cost, reduction in part weight and flexibility in mass production. It is necessary to obtain the stress-strain relationship of tailor-welded tubes to study deformation behaviors of tubes and simulate deformation tests of tubes. Then a method via digital image correlation (DIC) method based on uniaxial tensile test (UTT) is proposed in this paper to establish stress-strain relationship of tailor-welded tubes. Material parameters of tailor-welded tubes obtained from three methods, i.e. the method based on UTT, the iso-strain method based on a rule of mixtures and the proposed method, were compared in this paper. To assess the accuracy of material parameters obtained from these three methods, UTTs were simulated, and load-displacement curves and maximal loads obtained from simulations were compared with those obtained from UTTs. In simulations of UTTs, finite element models of specimens of sole parent metal and mixed specimens were established, respectively. The results show that: When HAZ included in the specimen has large proportion of the specimen, the proposed method is more reliable than the iso-strain method based on a rule of mixtures on determining the material parameters of the weld; load-displacement curve and maximal load obtained from the proposed method are more close to those obtained from UTT than those obtained from the method based on UTT.
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Cheng, Yang-Tse, and Che-Min Cheng. "Relationships between initial unloading slope, contact depth, and mechanical properties for conical indentation in linear viscoelastic solids." Journal of Materials Research 20, no. 4 (2005): 1046–53. http://dx.doi.org/10.1557/jmr.2005.0141.
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Using analytical and finite element modeling, we studied conical indentation in linear viscoelastic solids with either displacement or load as the independent variable. We examine the relationships between initial unloading slope, contact depth, and viscoelastic properties for various loading conditions such as constant displacement rate, constant loading rate, and constant indentation strain rate. We then discuss whether the Oliver–Pharr method for determining contact depth, originally proposed for indentation in elastic and elastic-plastic solids, is applicable to indentation in viscoelastic solids. We conclude with a few comments about two commonly used experimental procedures for indentation measurements in viscoelastic solids: the “hold-at-peak-load” technique and the constant indentation strain-rate method.
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Kim, Sung-Hu, Kyoung-Bong Han, Kwang-Soo Kim, and Sun-Kyu Park. "Stress–strain and deflection relationships of RC beam bonded with FRPs under sustained load." Composites Part B: Engineering 40, no. 4 (2009): 292–304. http://dx.doi.org/10.1016/j.compositesb.2008.12.003.
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Zhou, Ling Yuan, and Li Qiao. "Ultimate Load Analysis of Reinforced Concrete Beam with Finite Element." Advanced Materials Research 243-249 (May 2011): 1340–45. http://dx.doi.org/10.4028/www.scientific.net/amr.243-249.1340.
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A efficient 3D beam element based on the distributed nonlinearity theory is proposed for nonlinear analysis of reinforcement concrete structures. The sections consist of reinforcing steel and concrete in this formulation and the section stiffness matrices are calculated through the integration of stress-strain relations of concrete and the accumulation of reinforcing steel effect. The force-based formulation is adopted in the evaluation of the element stiffness matrix and the element state determination. The improved Kent-Park model is adopt for the stress-strain relation of concrete, and uniaxial stress–strain relationships proposed by Mander is introduced for reinforcing steel. Finally, the ultimate load of a cantilever reinforced concrete beam subjected to a lateral load was analyzed with the proposed formulation to illustrate its accuracy and computational efficiency.
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Alatshan, Faesal, Siti Aminah Osman, Roszilah A. Hamid, and Fidelis Mashiri. "Residual compressive strength of locally corroded circular CFST stub columns: An experimental study." IOP Conference Series: Earth and Environmental Science 1369, no. 1 (2024): 012036. http://dx.doi.org/10.1088/1755-1315/1369/1/012036.
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Abstract Circular concrete-filled steel tubular (CFST) columns are widely used in civil engineering structures due to their high strength, stiffness, and ductility. However, these columns are susceptible to local corrosion damage, which can reduce their load-carrying capacity and durability. This paper presents an experimental investigation of the impact of local corrosion on the residual compressive strength of CFST stub columns. The experimental program included 9 CFST columns, which were divided into two groups: G1 and G2. G1 specimens were subjected to actual electrochemical corrosion, while G2 specimens were subjected to mechanical damage to simulate the corrosion effect. The experimental results included the tested columns’ corrosion profiles, failure modes, load-strain relationships, and load-carrying capacities. The main findings of this paper show that: (1) Different heights and thicknesses of corrosion profile representing the non-uniform localized corrosion. (2) Failure modes were mainly affected by the localized damage conditions, where the buckling occurred in the affected area. (3) Load-strain relationships exhibited elastic behavior initially, followed by nonlinear plastic behavior until reaching their ultimate compressive capacity. (4) The mechanical damage method can reasonably approximate the corrosion damage in CFST columns. This paper provides useful insights into the structural behavior of locally damaged CFST short columns.
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Gao, Jin He, and Hiroshi Tagawa. "Development of Passive Energy Dissipation Device with U-Shaped Steel Damper Based on Quasi-Linear Motion Mechanism." Advanced Materials Research 446-449 (January 2012): 2656–60. http://dx.doi.org/10.4028/www.scientific.net/amr.446-449.2656.
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This paper presents a new energy dissipation device for earthquake protection of structures. The proposed device, which uses a quasi-linear motion mechanism, achieves dissipation of seismic energy into the structure through yielding of U-shaped steel dampers. Consequently bracing members are subjected to only tensile force. Cyclic loading tests of the portal moment frames with the proposed device are conducted. Results and discussions are presented with emphasis on key features which affect energy dissipation capability. The lateral load and story drift angle relationships show that the proposed device provides stable and reasonably large energy dissipation capability. The effect of pre-tension applied to the bracing members is also examined through the brace axial strain and lateral load relationship.
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Fafitis, A., and Y. H. Won. "A Multiaxial Stochastic Constitutive Law for Concrete: Part I—Theoretical Development." Journal of Applied Mechanics 59, no. 2 (1992): 283–88. http://dx.doi.org/10.1115/1.2899518.
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An incremental three-dimensional constitutive relation for concrete has been developed. The linear anisotropic and path-dependent behavior is modeled by updating the stiffness matrix at each load increment. The material is assumed incrementally elastic and the six elastic moduli E11, E12 .... E33 are expressed in terms of both the tangential hydrostatic and deviatoric stiffness whereas the three tangential shear moduli are expressed in terms of the deviatoric stiffness only. The hydrostatic and deviatoric stiffness are determined from uniaxial stress-strain relationships by employing the space truss concept. The unaxial stress-strain relationships are in a sense the stress-strain relationships of the members of the truss, and they were based on a rheological stochastic model developed earlier. The predictions of the model compare favorably with experimental data reported by various investigators. Complex loading paths are reproduced with acceptable accuracy as is demonstrated in the second part of this paper.
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Xu, Baoxing, and Xi Chen. "Determining engineering stress–strain curve directly from the load–depth curve of spherical indentation test." Journal of Materials Research 25, no. 12 (2010): 2297–307. http://dx.doi.org/10.1557/jmr.2010.0310.
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The engineering stress–strain curve is one of the most convenient characterizations of the constitutive behavior of materials that can be obtained directly from uniaxial experiments. We propose that the engineering stress–strain curve may also be directly converted from the load–depth curve of a deep spherical indentation test via new phenomenological formulations of the effective indentation strain and stress. From extensive forward analyses, explicit relationships are established between the indentation constraint factors and material elastoplastic parameters, and verified numerically by a large set of engineering materials as well as experimentally by parallel laboratory tests and data available in the literature. An iterative reverse analysis procedure is proposed such that the uniaxial engineering stress–strain curve of an unknown material (assuming that its elastic modulus is obtained in advance via a separate shallow spherical indentation test or other established methods) can be deduced phenomenologically and approximately from the load–displacement curve of a deep spherical indentation test.
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Ali, Balhassn S. M., Tom H. Hyde, and Wei Sun. "Small Two-Bar Specimen Creep Testing of Grade P91 Steel at 650°C." High Temperature Materials and Processes 35, no. 3 (2016): 243–52. http://dx.doi.org/10.1515/htmp-2014-0188.
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AbstractCommonly used small creep specimen types, such as ring and impression creep specimens, are capable of providing minimum creep strain rate data from small volumes of material. However, these test types are unable to provide the creep rupture data. In this paper the recently developed two-bar specimen type, which can be used to obtain minimum creep strain rate and creep rupture creep data from small volumes of material, is described. Conversion relationships are used to convert (i) the applied load to the equivalent uniaxial stress, and (ii) the load line deformation rate to the equivalent uniaxial creep strain rate. The effects of the specimen dimension ratios on the conversion factors are also discussed in this paper. This paper also shows comparisons between two-bar specimen creep test data and the corresponding uniaxial creep test data, for grade P91 steel at 650°C.
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Ter-Martirosyan, Zaven G., Armen Z. Ter-Martirosyan, and Huu H. Dam. "Settlement and Bearing Capacity of Rectangular Footing in Reliance on the Pre-Overburden Pressure of Soil Foundation." Applied Sciences 11, no. 24 (2021): 12124. http://dx.doi.org/10.3390/app112412124.
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This article presents a solution for the quantitative evaluation of the stress–strain state (SSS) and the bearing capacity of rectangular foundations, factoring in the unit weight of the soil mass and different values of pre-overburden pressure (POP). In order to assess the SSS of the soil subgrade below a rigid rectangular footing under a uniformly distributed load, the authors applied the Boussinesq basic solution for an elastic half-space subjected to a vertical point load on its surface. As a result, the formulas for vertical stress, mean stress, shear strain, and volumetric strain for any point in Cartesian coordinates (x, y, z) and foundation settlement were determined. Additionally, the application of Hencky’s system of physical equations, with non-linear dependencies between mean stress and volumetric strain as well as deviator stress and shear strain, along with the experimental curves, depicts the relationships between bulk modulus and volume stress, and shear modulus and shear stress. The authors point out the non-linear behavior of the subgrade soil and propose a method for estimating the bearing capacity of a rigid rectangular foundation.
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Glisson, Richard R., Douglas S. Musgrave, Robert D. Graham, and Thomas P. Vail. "Validity of Photoelastic Strain Measurement on Cadaveric Proximal Femora." Journal of Biomechanical Engineering 122, no. 4 (2000): 423–29. http://dx.doi.org/10.1115/1.1287162.
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Rosette strain gages indicate shear and principal strains at specific points, whereas photoelastic coatings provide shear strain information over a broad area. Information regarding bone loading and load transfer from a prosthetic implant to adjacent bone can be obtained using either strain-measuring technique on loaded femora. This study compared proximal femoral strains derived from photoelastic coatings to those obtained from rosette strain gages applied directly to the bone in order to determine the relationships between photoelastic shear strains and rosette shear and principal strains. Photoelastic shear strains underestimated rosette shear strains and exceeded the larger of the rosette principal strains. Principal strains derived from photoelastic coatings augmented with strain separator gages underestimated their rosette counterparts in most instances. Correlation was strong and nearly linear for all measures, indicating that photoelastic coatings can accurately express proportional strain changes despite imperfect agreement in absolute strain magnitudes. The best agreement between absolute strain magnitudes occurred in the proximal medial, or calcar, region. Understanding the relationships between the various measures obtained using the two strain measurement methods will allow more accurate estimates of actual strains to be made from photoelastic coatings. [S0148-0731(00)01704-0]
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Mandorino, Mauro, António J. Figueiredo, Gianluca Cima, and Antonio Tessitore. "Predictive Analytic Techniques to Identify Hidden Relationships between Training Load, Fatigue and Muscle Strains in Young Soccer Players." Sports 10, no. 1 (2021): 3. http://dx.doi.org/10.3390/sports10010003.
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This study aimed to analyze different predictive analytic techniques to forecast the risk of muscle strain injuries (MSI) in youth soccer based on training load data. Twenty-two young soccer players (age: 13.5 ± 0.3 years) were recruited, and an injury surveillance system was applied to record all MSI during the season. Anthropometric data, predicted age at peak height velocity, and skeletal age were collected. The session-RPE method was daily employed to quantify internal training/match load, and monotony, strain, and cumulative load over the weeks were calculated. A countermovement jump (CMJ) test was submitted before and after each training/match to quantify players’ neuromuscular fatigue. All these data were used to predict the risk of MSI through different data mining models: Logistic Regression (LR), Random Forest (RF), Support Vector Machine (SVM). Among them, SVM showed the best predictive ability (area under the curve = 0.84 ± 0.05). Then, Decision tree (DT) algorithm was employed to understand the interactions identified by the SVM model. The rules extracted by DT revealed how the risk of injury could change according to players’ maturity status, neuromuscular fatigue, anthropometric factors, higher workloads, and low recovery status. This approach allowed to identify MSI and the underlying risk factors.
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Yuslinda, Yuslinda, and Cut Meuthia Rani. "COMPARASION PLASTIC BEHAVIOR OF BOX GRIDER BRIDGE WITH MULTIPLE BOX AND CELLULAR BOX CROSS SECTIONS." Jurnal Teknik Sipil 24, no. 1 (2024): 873. http://dx.doi.org/10.26418/jts.v24i1.76313.
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This study compares plastic deformation behavior in box girder bridges with multiple boxes and cellular box cross-sections. The cross-section's shape significantly influences the girder's post-yield behavior despite being designed to have the exact yield moment. Steel's stress-strain relationship undergoes linear behavior until the yield stress is reached, followed by strain hardening. This study aims to assess the impact of strain hardening on the plastic behavior of girder box bridges.Two types of box girder sections, multiple box and cellular box, are designed with equivalent yield moments. The analysis is conducted with and without strain hardening calculations to evaluate plastic moment, inelastic area length, shape factor, and moment-curvature relationship. The design and analysis follow RSNI T-03-2005 standards using SAP 2000 v.15.Results indicate that multiple box sections exhibit more prominent plastic moments and inelastic area lengths than cellular box sections. Strain hardening calculations show significant increases in plastic moments for both section types. Graphical comparisons highlight the differences in moment-curvature relationships between models with and without strain hardening. Understanding the impact of strain hardening on plastic behavior provides valuable insights for designing and assessing box girder bridges, ensuring structural safety and performance under load conditions.
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Derr, J. S., and M. A. Persinger. "Geophysical Variables and Behavior: LXXVI. Seasonal Hydrological Load and Regional Luminous Phenomena (UFO Reports) within River Systems, the Mississippi Valley Test." Perceptual and Motor Skills 77, no. 3_suppl (1993): 1163–70. http://dx.doi.org/10.2466/pms.1993.77.3f.1163.
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We hypothesized that an equilibrium in seasonal variations between water load and both seismicity and reports of odd, spherical, luminous phenomena within the river basin should result in systematic but phase-lagged relationships between these variables. Within 320 km of the confluence of the Mississippi System, the monthly variation of a specific and major class of UFO reports (which appear to represent luminous phenomena that are generated by tectonic strain) peaked 3 to 4 months ( r = 0.87) after the river crested. The phase lag between these luminous phenomena and seismic activity within the same region was about 6 months. The results support the model that river load-induced strain and fluid percolation into and diffusion within the earth's crust promote the production of natural luminous phenomena.
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Liu, Gege, Yahong Zhang, and Xinong Zhang. "Equivalence relationship between a three-axis centrifugal test load and flight load." International Journal of Computational Materials Science and Engineering 07, no. 01n02 (2018): 1850011. http://dx.doi.org/10.1142/s2047684118500112.
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For aircraft flying with high accelerations and high acceleration change rates in three-dimensional space, load simulation tests are usually carried out in a three-axis centrifuge with three degrees of freedom. A triaxial centrifugal test that simulates the actual flight environment must reflect the real effect of the flight load on the structure. An acceleration analysis model of a three-axis centrifuge in body coordinates is established to meet this requirement. The spatial distribution of the acceleration and the effects of kinematic parameters on acceleration are analyzed. Using the acceleration analysis model, the displacement equivalence and strain energy equivalence relations of a beam in a centrifugal environment and actual flight environment are studied. Moreover, equivalence relationships meeting requirements are proposed and validated for a specific example. The distribution of the acceleration and the equivalence relations of the two environments are the basis for the ground simulation of flight loads.
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Zhao, Kang, Hui Wang, Houchuan Li, Yang Wei, Jinwei Lu, and Guofen Li. "Experimental and Numerical Analysis of Shear Performance of 16 m Full-Scale Prestressed Hollow Core Slabs." Infrastructures 10, no. 1 (2024): 2. https://doi.org/10.3390/infrastructures10010002.
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To investigate the shear performance of 16 m span prestressed hollow core slabs, shear tests were conducted on three pre-tensioned prestressed hollow core slabs with the same shear-to-span ratio. A systematic analysis was performed on the failure modes, crack development patterns, load–deflection relationships, and load–strain relationships of the prestressed hollow slabs. The test results indicate that all specimens experienced shear-compression failure under the same shear-to-span ratio (2.71). The main diagonal shear cracks were distributed within a range of 1.35 m to 1.95 m from the beam ends, with crack angles approximately between 45° and 55°. Finite element software ABAQUS was used for detailed numerical simulation of the tests. By comparing the failure modes and load–displacement curves, the reliability and applicability of the finite element model were verified.
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Zinck, Christopher B., Prasobh Raveendram Thampy, Eva-Maria E. Uhlemann, et al. "Variation among strains of Borrelia burgdorferi in host tissue abundance and lifetime transmission determine the population strain structure in nature." PLOS Pathogens 19, no. 8 (2023): e1011572. http://dx.doi.org/10.1371/journal.ppat.1011572.
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Pathogen life history theory assumes a positive relationship between pathogen load in host tissues and pathogen transmission. Empirical evidence for this relationship is surprisingly rare due to the difficulty of measuring transmission for many pathogens. The comparative method, where a common host is experimentally infected with a set of pathogen strains, is a powerful approach for investigating the relationships between pathogen load and transmission. The validity of such experimental estimates of strain-specific transmission is greatly enhanced if they can predict the pathogen population strain structure in nature. Borrelia burgdorferi is a multi-strain, tick-borne spirochete that causes Lyme disease in North America. This study used 11 field-collected strains of B. burgdorferi, a rodent host (Mus musculus, C3H/HeJ) and its tick vector (Ixodes scapularis) to determine the relationship between pathogen load in host tissues and lifetime host-to-tick transmission (HTT). Mice were experimentally infected via tick bite with 1 of 11 strains. Lifetime HTT was measured by infesting mice with I. scapularis larval ticks on 3 separate occasions. The prevalence and abundance of the strains in the mouse tissues and the ticks were determined by qPCR. We used published databases to obtain estimates of the frequencies of these strains in wild I. scapularis tick populations. Spirochete loads in ticks and lifetime HTT varied significantly among the 11 strains of B. burgdorferi. Strains with higher spirochete loads in the host tissues were more likely to infect feeding larval ticks, which molted into nymphal ticks that had a higher probability of B. burgdorferi infection (i.e., higher HTT). Our laboratory-based estimates of lifetime HTT were predictive of the frequencies of these strains in wild I. scapularis populations. For B. burgdorferi, the strains that establish high abundance in host tissues and that have high lifetime transmission are the strains that are most common in nature.
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Suparp, Suniti, Ali Ejaz, Kaffayatullah Khan, Qudeer Hussain, Panuwat Joyklad, and Panumas Saingam. "Load-Bearing Performance of Non-Prismatic RC Beams Wrapped with Carbon FRP Composites." Sensors 23, no. 12 (2023): 5409. http://dx.doi.org/10.3390/s23125409.
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This study investigated the influence of CFRP composite wrapping techniques on the load–deflection and strain relationships of non-prismatic RC beams. A total of twelve non-prismatic beams with and without openings were tested in the present study. The length of the non-prismatic section was also varied to assess the effect on the behavior and load capacity of non-prismatic beams. The strengthening of beams was performed by using carbon fiber-reinforced polymer (CFRP) composites in the form of individual strips or full wraps. The linear variable differential transducers and strain gauges were installed at the steel bars to observe the load–deflection and strain responses of non-prismatic RC beams, respectively. The cracking behavior of unstrengthened beams was accompanied by excessive flexural and shear cracks. The influence of CFRP strips and full wraps was primarily observed in solid section beams without shear cracks, resulting in enhanced performance. In contrast, hollow section strengthened beams exhibited minor shear cracks alongside the primary flexural cracks within the constant moment region. The absence of shear cracks was reflected in the load–deflection curves of strengthened beams, which demonstrated a ductile behavior. The strengthened beams demonstrated 40% to 70% higher peak loads than control beams, whereas the ultimate deflection was increased up to 524.87% compared to that of the control beams. The improvement in the peak load was more prominent as the length of the non-prismatic section increased. A better improvement in ductility was achieved for the case of CFRP strips in the case of short non-prismatic lengths, whereas the efficiency of CFRP strips was reduced as the length of the non-prismatic section increased. Moreover, the load–strain capacity of CFRP-strengthened non-prismatic RC beams was higher than the control beams.
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Bodrov, I. G., and A. Yu Shishelova. "The typology of mechanisms of adaptation to the cognitive load on the variability of heart rate dynamics." Experimental Psychology (Russia) 11, no. 3 (2018): 78–93. http://dx.doi.org/10.17759/exppsy.2018110306.
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While analyzing heart rate variability there were detected two types of visceral adaptation to cognitive activities: the first one is characterized by decrease of tension index (Baevskiy, 1984) and increase of heart rate variability at a cognitive load, along with increased power of regulatory effects on the heart rate; the second one is defined by higher heart rate variability, higher power of regulatory effects before the cognitive load and increase of the strain index during cognitive load in the absence of other significant changes. It is peculiar for people related to these types to possess different correlation relationships between the indices of sensory-motor reactions and heart rate variability.
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Clark, S. K., and R. N. Dodge. "Nonlinear Cord-rubber Composites." Tire Science and Technology 18, no. 3 (1990): 191–200. http://dx.doi.org/10.2346/1.2141699.
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Abstract An analytical method is proposed for the prediction of load-deflection and stress-strain relations in two-dimensional elastomeric composites where the properties are highly nonlinear. Such materials are represented by various textile cords used as reinforcements in a rubber matrix. The analytical procedure involves a forward prediction process for simultaneous nonlinear equations and can readily be implemented for automated computer use. Experiments on nonlinear tubes are reported and computation of load-deflection relationships observed in those experiments are compared with experimental data. The predictions generally agree with the observed behavior.
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Englander, Zoë A., Brian C. Lau, Jocelyn R. Wittstein, Adam P. Goode, and Louis E. DeFrate. "Patellar Tendon Orientation and Strain Are Predictors of ACL Strain In Vivo During a Single-Leg Jump." Orthopaedic Journal of Sports Medicine 9, no. 3 (2021): 232596712199105. http://dx.doi.org/10.1177/2325967121991054.
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Background: There is little in vivo data that describe the relationships between patellar tendon orientation, patellar tendon strain, and anterior cruciate ligament (ACL) strain during dynamic activities. Quantifying how the quadriceps load the ACL via the patellar tendon is important for understanding ACL injury mechanisms. Hypothesis: We hypothesized that flexion angle, patellar tendon orientation, and patellar tendon strain influence ACL strain during a single-leg jump. Specifically, we hypothesized that patellar tendon and ACL strains would increase concurrently when the knee is positioned near extension during the jump. Study Design: Descriptive laboratory study. Methods: Models of the femur, tibia, ACL, patellar tendon, and quadriceps tendon attachment sites of 8 male participants were generated from magnetic resonance imaging (MRI). High-speed biplanar radiographs during a single-leg jump were obtained. The bone models were registered to the radiographs, thereby reproducing the in vivo positions of the bones, ligament, and tendon attachment sites. Flexion angle, patellar tendon orientation, patellar tendon strain, and ACL strain were measured from the registered models. ACL and patellar tendon strains were approximated by normalizing their length at each knee position to their length at the time of MRI. Two separate bivariate linear regression models were used to assess relationships between flexion angle and patellar tendon orientation and between ACL strain and patellar tendon strain. A multivariate linear regression model was used to assess whether flexion angle and patellar tendon strain were significant predictors of ACL strain during the inflight and landing portions of the jump. Results: Both flexion angle and patellar tendon strain were significant predictors ( P < .05) of ACL strain. These results indicate that elevated ACL and patellar tendon strains were observed concurrently when the knee was positioned near extension. Conclusion: Concurrent increases in patellar tendon and ACL strains indicate that the quadriceps load the ACL via the patellar tendon when the knee is positioned near extension. Clinical Relevance: Increased ACL strain when the knee is positioned near extension before landing may be due to quadriceps contraction. Thus, landing with unanticipated timing on an extended knee may increase vulnerability to ACL injury as a taut ligament is more likely to fail.
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Ahn, Jeong-Hoon, and Dongil Kwon. "Derivation of plastic stress–strain relationship from ball indentations: Examination of strain definition and pileup effect." Journal of Materials Research 16, no. 11 (2001): 3170–78. http://dx.doi.org/10.1557/jmr.2001.0437.
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The ball indentation technique has the potential to be an excellent substitute for a standard tensile test, especially in the case of small specimens or property-gradient materials such as welds. In our study, the true stress–true strain relationships of steels with different work-hardening exponents (0.1–0.3) were derived from ball indentations. Four kinds of strain definitions in indentation were attempted: 0.2sinγ, 0.4hc/a, ln[2/(1 + cosγ)], and 0.1tanγ. Here, γ is the contact angle between the indenter and the specimen, hc is the contact depth, and a is the contact radius. Through comparison with the standard data measured by uniaxial tensile testing, the best strain definition was determined to be 0.1tanγ. This new definition of strain, in which tanγ means the shear strain at contact edge, reflected effectively the work-hardening characteristics. In addition, the effects of pileup or sink-in were considered in determining the real contact between the indenter and the specimen from the indentation load–depth curve. The work-hardening exponent was found to be a main factor affecting the pileup/sink-in phenomena of various steels. These phenomena influenced markedly the absolute values of strain and stress in indentation by making the simple traditional relationship Pm/σR ≈ ≈ 3 valid for the fully plastic regime.
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Niinomi, M., T. Akahori, M. Nakai, et al. "Quantitative relationship between microstructural factors and fatigue life of Ti-5Al-2Sn-2Zr-4Cr-4 Mo (Ti-17) fabricated using a 1500-ton forging simulator." MATEC Web of Conferences 321 (2020): 11015. http://dx.doi.org/10.1051/matecconf/202032111015.
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The microstructures, tensile properties, and fatigue lives of the forged Ti-17 using a 1500-ton forging simulator subjected to different solution treatments and a common aging treatment under both load- and strain-controlled conditions to evaluate high cycle fatigue and low cycle fatigue lives, respectively were examined. Then, the tensile properties, microstructures, and relationships between fatigue lives and the microstructural factors were discussed. The fatigue limit under load-controlled conditions increases with increasing solution treatment temperature up to 1143 K, which is in the (α + β) region. However, it decreases with further increase in the solution treatment temperature to 1203 K in the b region. The fatigue ratio at fatigue limit is increasing with decreasing solution treatment temperature, namely increasing the volume fraction of the primary α phase, and it relates well qualitatively with the volume fraction of the primary α phase when the solution treatment temperature is less than the b transus temperature. The fatigue life under strain-controlled conditions to evaluate the low cycle fatigue life increases with decreasing solution treatment temperature, namely increasing the volume fraction of the primary α phase. The fatigue life under strain-controlled conditions to evaluate the low cycle fatigue life relates well quantitatively with the tensile true strain at breaking of the specimen and the volume fraction of the primary α phase for each total strain range.
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Wheeler, L. N., W. A. Take, N. A. Hoult, and H. Le. "Use of fiber optic sensing to measure distributed rail strains and determine rail seat forces under a moving train." Canadian Geotechnical Journal 56, no. 1 (2019): 1–13. http://dx.doi.org/10.1139/cgj-2017-0163.
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Rayleigh backscatter fiber optic sensing permits dynamic strains to be measured along an optical fiber with a gauge spacing and temporal resolution sufficient for rail applications. However, this sensing technology is highly sensitive to vibration. A 7.5 m long section of rail was instrumented with optical fiber and strain measurements were recorded during passage of a freight train slowed to 8–11 km/h. This strategy to minimize rail vibration was successful in permitting distributed dynamic rail strains to be measured under freight car loading. The measured rail strains were used to determine the rail shear forces, which were then used with the static wheel loads to determine the rail seat load for 14 consecutive sleepers as the train passed over the field monitoring site. These data were then combined with measurements of dynamic rail displacement captured using digital image correlation to infer the rail seat load–deflection relationships for individual sleepers. These relationships were observed to provide significantly more detailed information about unsupported voids and the sleeper contact stiffnesses than the traditional consideration of the relationship between applied load and rail deflection and highlights how track behavior at a monitored location can be dependent on the conditions and behavior of neighbouring sleeper.
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Sreedhara, B. M., M. Rahul Raj, Geetha Kuntoji, Sujay Raghavendra Naganna, and Zaher Mundher Yaseen. "Stress-Strain Relationships and Failure Load Analysis of Cement-Stabilized Rammed Earth under Concentric and Eccentric Loading Using Finite Element Modelling." Advances in Civil Engineering 2022 (August 2, 2022): 1–9. http://dx.doi.org/10.1155/2022/2722831.
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Among many alternative building materials, soil in the form of rammed Earth is the most ancient construction material and technology. Large-scale application of the rammed Earth technology in the construction industry requires the assessment of its strength and failure behaviour. Therefore, this study focused on performing a nonlinear stability analysis of cement-stabilized rammed Earth (CSRE) specimens having a height-to-thickness (H/T) ratios—3 and 4 and loaded under varying degrees of eccentricities 0, 1/3, 1/6, and 1/12. The maximum compressive strength and the stress-strain behaviour of the CSRE specimens were determined through finite element (FE) modeling. The experimental results of the cement-stabilized rammed Earth (CSRE) have been obtained from literature for validation by FE simulation. As the H/T ratio was increased from 3 to 4, the load-bearing capacity of the CSRE specimens increased by 2.91% under concentric loading condition; however, when the eccentricity of load application was swapped from 0 to 1/12, 1/6, and 1/3, the load-bearing capacity decreased incrementally. The results of the FE analysis of the specimens showed that the compressive strength and elastic properties of the CSRE specimens did not differ significantly. The stress-strain relationships were nonlinear and elastic properties were affected by soil textural composition and density.
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Al Amli, Ali Sabah, Nadhir Al-Ansari, and Jan Laue. "Study Numerical Simulation of Stress-Strain Behavior of Reinforced Concrete Bar in Soil using Theoretical Models." Civil Engineering Journal 5, no. 11 (2019): 2349–58. http://dx.doi.org/10.28991/cej-2019-03091416.
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Nonlinear analysis for reinforced concrete members (R.C.) with two types of bars also with unsaturated and saturated soils was used to represent the models. To control the corrosion in the steel bar that used in R.C. member and decrease the cost, the geogrid with steel bar reinforcement are taken in this study to determine the effect of load-deflection and stress-strain relationships. The finite element method is used to model the R.C. member, bars and soil. A three-dimensional finite element model by ABAQUS version 6.9 software program is used to predict the load versus deflection and stress versus strain response with soil. The results for the model in this study are compared with the experimental results from other research, and the results are very good. Therefore, it was concluded that the models developed in this study can accurately capture the behavior and predict the load-carrying capacity of such R.C. members with soil and the maximum stresses with strains. The results show plastic strain values in the R.C. member with saturated soil are larger than their values in unsaturated soil about (54%, 58%, and 55% and 52%) when the geogrid ratios are (without geogrid, 60%, 40% and 20%) respectively, with the same values of stresses.
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Ramulu, Malothu, and Arkanti Krishnaiah. "The Effect of Die Channel Angles and their Combination on Plastic Deformation of Pure Copper during Equal Channel Angular Pressing Using Finite Element Modelling." Advanced Engineering Forum 31 (February 2019): 63–69. http://dx.doi.org/10.4028/www.scientific.net/aef.31.63.
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It was investigated the effect of die channel angles and their combination on plastic deformation of pure copper during ECAP under friction and frictionless conditions using 2-D elastic-plastic finite element modelling. A sound knowledge obtained for the plastic deformation (material flow) and understood the relationships between plastic deformations. The modelling results suggested that strain inhomogeneity was lesser in channel angle 120o than channel angle 90o and pressing load as well as strain decrease with increasing die channel angle. The friction influence in case of combination of channel angles was negligible as compare to individual channel angles. The strain generation and distribution was more uniform in case of combination of channel angles as compare to individual channel angles.
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Zhang, Zhongwei, Yufeng Liu, Longbiao Li, and Daining Fang. "Modeling Tensile Damage and Fracture Behavior of Fiber-Reinforced Ceramic-Matrix Minicomposites." Materials 13, no. 19 (2020): 4313. http://dx.doi.org/10.3390/ma13194313.
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Evolution of damage and fracture behavior of fiber-reinforced mini ceramic-matrix composites (mini-CMCs) under tensile load are related to internal multiple damage mechanisms, i.e., fragmentation of the brittle matrix, crack defection, and fibers fracture and pullout. In this paper, considering multiple micro internal damage mechanisms and related models, a micromechanical constitutive stress–strain relationship model is developed to predict the nonlinear mechanical behavior of mini-CMCs under tensile load corresponding to different damage domains. Relationships between multiple micro internal damage mechanisms mentioned above and tensile micromechanical multiple damage parameters are established. Experimental tensile nonlinear behavior, internal damage evolution, and micromechanical tensile damage parameters corresponding to different damage domains of two different types of mini-CMCs are predicted. The effects of constitutive properties and damage-related parameters on nonlinear behavior of mini-CMCs are discussed.
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Mensah, Comfort, Zhenqing Wang, Alex Osei Bonsu, and Wenyan Liang. "Effect of Different Bond Parameters on the Mechanical Properties of FRP and Concrete Interface." Polymers 12, no. 11 (2020): 2466. http://dx.doi.org/10.3390/polym12112466.
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This paper presents double shear tests performed to investigate factors influencing the bond behavior between basalt fiber-reinforced polymer (BFRP), glass fiber-reinforced polymer (GFRP) laminate, and concrete blocks. In detail, thirty-six twin concrete blocks strengthened with the aforementioned FRP types were tested to evaluate the influence of FRP length, width, and thickness, and their bonding behavior. The 2D-DIC (digital image correlation) technique and several strain gauges bonded along the laminate were used to measure the strain distributions of the FRP-to-concrete interface. The failure mode, ultimate load, load–slip, strain distribution, and bond–slip relationships between the laminates and concrete were analyzed. Furthermore, bond–slip curves were compared with some other existing literature models. The results from the experiment showed that the ultimate load, peak bond stress, and slip increased with the increase in the BFRP and GFRP laminates length, width, and thickness. The values of peak shear stress and the corresponding maximum shear slip were significantly different because of the above-mentioned factors’ influence on them. The bond interface that contributes to the bearing of the shear load may grow to an extent and later shift from the loaded end when debonding progresses. Finally, the fractured surfaces of the failed FRP laminates were examined using scanning electron microscope (SEM), revealing that FRP rupture, debonding in concrete, and debonding in an adhesive–concrete interface were the main failure types.
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Chen, Ke Ping, Jin Yuan Liu, and Bing Xiang Yuan. "Environmental Safety Analysis for Slope under the Situation with and without Load on Top Surface." Advanced Materials Research 356-360 (October 2011): 2114–17. http://dx.doi.org/10.4028/www.scientific.net/amr.356-360.2114.
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In order to study the effect of dilation angle ψ to the stability of slope, a numerical model was founded in plane strain mode by FLAC3D for homogeneous soil slope. The safety factors and slip planes were obtained for different dilation angles, and the relationships of dilation angle, safety factor and slip plane were analyzed for different situations with and without load on the top surface.
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Hobbs, S. J., J. Mather, C. Rolph, and J. Richards. "The effects of limb posture on relationships between in vitro radial hoof strain, load and joint angles." Equine Veterinary Journal 41, no. 3 (2009): 229–32. http://dx.doi.org/10.2746/042516409x395967.
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Hong, Junqing, Shaofeng Zhang, Hai Fang, Xunqian Xu, Honglei Xie, and Yuntian Wang. "Structural performance of textile reinforced concrete sandwich panels under axial and transverse load." REVIEWS ON ADVANCED MATERIALS SCIENCE 60, no. 1 (2021): 64–79. http://dx.doi.org/10.1515/rams-2021-0015.
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Abstract The performance of textile reinforced concrete composite panels (TRCCPs) under the action of pseudo-static load up to collapse was evaluated. The test of TRCCPs under axial and transverse loading was conducted, and the results were compared with those for steel wire mesh reinforced-concrete composite panels (SMRCCPs). Ceram-site concrete was utilized as the panel matrix owing to its lightweight and insulation characteristics. The ultimate load bearing capacity, load-deformation and load-strain relationships, and failure modes were discussed and investigated in comparison with the findings of non-linear finite-element-model (FEM) analysis and the analytic method on the basis of the reinforced concrete (RC) theory. The analysis results indicate that TRCCP is suitable for use as a potential structural member for a wall or slab system of buildings, and the typical RC theory can be applied to predict the ultimate load bearing capacity if modified suitably.
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Bu, Jianqing, Zhibo Guo, Jiren Zhang, and Yanzhe Zhang. "Experimental Study on the Damage Mechanism of Reinforced Concrete Beams Based on Acoustic Emission Technique." Applied Sciences 13, no. 16 (2023): 9207. http://dx.doi.org/10.3390/app13169207.
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The purpose of this paper is to investigate the developmental process of internal damage in prestressed concrete beams under static loading conditions. We conducted static loading tests on two prestressed reinforced concrete beams and one ordinary reinforced concrete beam. Acoustic emission (AE) technology was employed to dynamically monitor the entire process of the test beams simultaneously. The energy and ring count AE characteristic parameters were studied, and the frequency domain characteristics of acoustic emission signals from three test beams were analyzed. The actual failure process of the test beams was compared with the AE characteristic parameters and the waveform frequency distribution. Furthermore, the corresponding relationships between the actual failure process and the AE characteristic parameters were analyzed. Additionally, the frequency distribution of waveforms was examined. The obtained data, including deflection, strain, and prestress variation within the beams, were combined with theoretical calculations to explore the damage development law of simply supported reinforced concrete beams during the entire failure process. Comparative studies revealed a strong correlation between the actual failure processes of the three test beams and the AE characteristic parameters as well as the waveform frequency distribution. The strain variation trend of the ordinary reinforced concrete beam closely matched the AE signal characteristics, with the critical load often occurring at around 40% of the ultimate load. The strain and deflection variations of the prestressed reinforced concrete beams exhibited a robust correspondence with the AE signal characteristics. The critical load typically manifested at approximately 80% of the ultimate load. The ultimate load of the prestressed reinforced concrete beams decreased by approximately 20% under cyclic loading conditions compared to hierarchical loading.
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Robinson, Paul S., Tony W. Lin, Paul R. Reynolds, Kathleen A. Derwin, Renato V. Iozzo, and Louis J. Soslowsky. "Strain-Rate Sensitive Mechanical Properties of Tendon Fascicles From Mice With Genetically Engineered Alterations in Collagen and Decorin." Journal of Biomechanical Engineering 126, no. 2 (2004): 252–57. http://dx.doi.org/10.1115/1.1695570.
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Tendons have complex mechanical behaviors that are nonlinear and time dependent. It is widely held that these behaviors are provided by the tissue’s composition and structure. It is generally thought that type I collagen provides the primary elastic strength to tendon while proteoglycans, such as decorin, play a role in failure and viscoelastic properties. This study sought to quantify such structure-function relationships by comparing tendon mechanical properties between normal mice and mice genetically engineered for altered type I collagen content and absence of decorin. Uniaxial tensile ramp to failure experiments were performed on tail tendon fascicles at two strain rates, 0.5%/s and 50%/s. Mutations in type I collagen led to reduced failure load and stiffness with no changes in failure stress, modulus or strain rate sensitivity. Fascicles without decorin had similar elastic properties to normal fascicles, but reduced strain rate sensitivity. Fascicles from immature mice, with increased decorin content compared to adult fascicles, had inferior elastic properties but higher strain rate sensitivity. These results showed that tendon viscoelasticity is affected by decorin content but not by collagen alterations. This study provides quantitative evidence for structure-function relationships in tendon, including the role of proteoglycan in viscoelasticity.
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Su, H., A. Cornec, and K. H. Schwalbe. "Engineering Treatment Model (ETM) for Crack Driving Force Estimation of Structures With Stress Concentration." Journal of Pressure Vessel Technology 115, no. 2 (1993): 164–70. http://dx.doi.org/10.1115/1.2929511.
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A simple relationship for estimating the limit load of a structure with a crack located in a zone with high stress-strain concentration has been suggested using Neuber’s relation. Then, based on the engineering treatment model (ETM), a method for calculating the crack driving force in the structure with a stress concentration was developed. It has also been proved that under deformation plasticity theory and monotonic loading, the ETM can be justified theoretically. Relationships between ETM and other engineering methods have also been established. The predictions by ETM agree well with the test results of full-scale pressure vessels with corner cracks at the joint between cylinder and nozzle.
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Krawczyk, Jacek, Wojciech Gurdziel, Włodzimierz Bogdanowicz, and Krzysztof Flisiński. "Temperature Influence on Stress-Strain Relationship of Al-Cu-Fe Crystal-Quasicrystal Composites." Solid State Phenomena 163 (June 2010): 282–85. http://dx.doi.org/10.4028/www.scientific.net/ssp.163.282.
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The columnar composites obtained “in situ” through solidification of Al61Cu27Fe12 alloy by the Bridgman method were studied. It has been verified that the matrix consisted of cubic single crystal β phase and the reinforcement of icosahedral quasicrystal ψ phase and monoclinic crystal λ phase, which have the form of rods. This kind of composites will be named the Al-Cu-Fe crystal-quasicrystal (CQ) composites. The effect of heating from a temperature of about 100°C to about 650°C on the stress-strain relationships σ(ε) of parallel samples was studied. Additionally, the σ(ε) relationship was defined in cyclic load-unload tests at different temperatures. The composites were examined by powder X-ray diffraction and scanning electron microscope.
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Loitz, B. J., and R. F. Zernicke. "Strenuous exercise-induced remodelling of mature bone: relationships between in vivo strains and bone mechanics." Journal of Experimental Biology 170, no. 1 (1992): 1–18. http://dx.doi.org/10.1242/jeb.170.1.1.
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Mature bone can adapt to strenuous exercise, but no study has correlated the changes in bone in vivo strains, remodelling and mechanical properties that occur as a consequence of strenuous training. Therefore, we examined exercise-related remodelling and in vivo strains in the tarsometatarsus (TMT) of three groups of adult (post-physial closure) White Leghorn roosters: basal control (30 weeks of age), age-matched control (39 weeks) and exercise (39 weeks). Exercise birds ran for 1 h a day, 5 days a week for 9 weeks at 70–75% of predicted maximum aerobic capacity. During treadmill locomotion, in vivo strains were recorded from miniature rosette strain gauges implanted on anterior, medial and lateral TMT cortices. TMT mechanical properties were measured with three-point bending tests to failure. Cortical morphometry was digitized from photographic slides of a 1-mm thick mid-diaphysial cross section of each bone. Exercise and age-matched control TMTs had significantly greater cortical area and maximum load than had basal controls. Exercise axial strains significantly exceeded basal and age-matched control strains along the anterior and lateral surfaces. Age-matched control anterior axial strain was twice that of the basal control. The mature bone remodelling suggested that the structural properties optimized by exercise-induced remodelling may differ from those optimized by age-related remodelling. The findings support the osteoregulatory role of strain but contradict earlier data suggesting that strain magnitudes do not change significantly with age or exercise.
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Taukoor, Vashish, Cassandra J. Rutherford, and Scott M. Olson. "A semi-empirical relationship for the small-strain shear modulus of soft clays." E3S Web of Conferences 92 (2019): 04005. http://dx.doi.org/10.1051/e3sconf/20199204005.
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The small-strain shear modulus (Gmax) is a soil property that has many practical applications. The authors compiled a database of Gmax measurements for 40 normally consolidated to slightly overconsolidated low to high plasticity clays. Using these data, the authors propose a semi-empirical relationship between Gmax, effective stress (σ'v or σ'c), preconsolidation stress (σ'p) and in-situ void ratio (e0) for four ranges of plasticity index (Ip): Ip < 30%, 30% ≤ Ip < 50%, 50% ≤ Ip < 80% and 80% ≤ Ip < 120%. With results from bender element tests on a Gulf of Mexico clay subjected to multiple load-unload consolidation loops, the authors were able to validate the proposed relationships for 30% ≤ Ip < 50% and 50% ≤ Ip < 80%. The proposed relationship for 30% ≤ Ip < 50% and 50% ≤ Ip < 80% captures changes in laboratory Gmax resulting from variations in effective stress (σ'c), maximum past stress (σ'v,max), and void ratio. The proposed relationships are a simple and efficient tool that can provide independent insight on Gmax if the stress history of a clay is known, or on stress history if Gmax is known.
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Benedetty, Carlos Alberto, Ingrid R. Irreño, Juan J. Martinez, Luiz C. Almeida, Leandro M. Trautwein, and Pablo A. Krahl. "Ultimate capacity prediction of RC and SFRC beams with low shear span-depth ratio using NLFEA and inverse analysis." Revista de la construcción 21, no. 3 (2022): 717–36. http://dx.doi.org/10.7764/rdlc.21.3.717.
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In this study, the capacity and ultimate behavior of Reinforced Concrete (RC) and Steel Fiber Reinforced Concrete (SFRC) beams are evaluated. Nonlinear Finite Element Analysis (NLFEA) and the inverse analysis technique were used to model its structural response using the ATENA finite element software. The smeared crack approach, the crack band model, and advanced constitutive models were used to reproduce concrete fracture. The analyzed beams were subjected to rupture in a four-point bending test setup. The relationship between the shear span and the depth of the beams was 1.5. Four scenarios were analyzed, RC beams with and without stirrups, and SFRC beams without stirrups with volumes of 0.57% and 0.76%. The results obtained in the modeling are discussed in terms of the ability of the models to numerically reproduce the relationships: load versus displacement, load versus strain, crack patterns, and failure modes. The analysis techniques allowed to reproduce the experimental response of the beams with good agreement. They show great potential to solve structural engineering problems
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Dudko, Olga V., Victoria E. Ragozina, and Anastasia A. Lapteva. "Mathematical Modeling the Nonlinear 1D Dynamics of Elastic Heteromodular and Porous Materials." Materials Science Forum 945 (February 2019): 899–905. http://dx.doi.org/10.4028/www.scientific.net/msf.945.899.
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Approaches to mathematical modeling of nonlinear strain dynamics in heteromodular and porous materials are discussed; the mechanical properties of media are described in terms of the simple piecewise linear elastic models. Several nonstationary 1D boundary value problems show that the singularity of model relationships gives rise to shock waves and centered Riemann waves in generalized solutions. Nonstationary load modes leading to the listed nonlinear effects are indicated separately for heteromodular and porous media.
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Bagbag, A. A., B. M. Lehane, and J. P. Doherty. "Settlement of deep footings in reconstituted sand." Canadian Geotechnical Journal 56, no. 3 (2019): 449–59. http://dx.doi.org/10.1139/cgj-2017-0574.
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The paper examines methods for predicting the settlement of deep footings in reconstituted sand. Results from vertical load tests on deep circular plates within a laboratory pressure chamber are interpreted using data from triaxial tests, cone penetration tests (CPTs), and pressuremeter tests obtained for the same reconstituted sand. A simple nonlinear CPT-based relationship is shown to match the response observed in the plate tests and be consistent with finite element analyses as well as other comparable physical tests. The relationships between foundation stiffness and the sand’s small-strain stiffness, its stiffness at 50% mobilized strength, and its response to pressuremeter loading are also explored. Comparisons with full-scale tests in the field reveal a strong effect of ageing on foundation stiffness, which appears to be better captured by small-strain stiffness than CPT end resistance. Measurements confirm that vertical loading of a deep plate is analogous to the expansion of a spherical cavity.
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Ding, Hongli, Chun Zhang, Yinjie Zhao, and Jian Yu. "A Load Estimation Method Based on Surface Crack Distribution Images of Reinforced Concrete Beams." Buildings 15, no. 6 (2025): 922. https://doi.org/10.3390/buildings15060922.
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The preliminary assessment of structural status in reinforced concrete (RC) using visual indicators like surface cracks serves as the primary step in formulating maintenance and reinforcement strategies. To enhance the efficiency of load identification and damage assessment, this study proposes a novel method for determining external load levels on RC beams using structural surface crack distribution images. First, crack distribution characteristics are extracted using image segmentation techniques. Subsequently, mechanical responses of the beam under different load levels are acquired through the finite element method (FEM). Then, this study develops a novel correlation index model by analyzing the relationships between crack distribution images and strain distribution images from the FEM, enabling accurate identification of the load level that best matches the actual crack distribution. Finally, a preliminary assessment of the damage state is conducted through elastoplastic analysis of the RC beam under the optimal load level. Verification analysis based on multiple experimental beam datasets under different load levels demonstrates that the mean absolute percentage error of the method is 10.98%, and the damage assessment results are in good agreement with the crack distribution images.
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Pang, Yu-Yang, Gang Wu, Zhi-Long Su, and Xiao-Yuan He. "Experimental study on the carbon-fiber-reinforced polymer–steel interfaces based on carbon-fiber-reinforced polymer delamination failures and hybrid failures." Advances in Structural Engineering 23, no. 11 (2020): 2247–60. http://dx.doi.org/10.1177/1369433220911167.
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The failure mode is crucial to the interfacial bond performance between carbon-fiber-reinforced polymer plates and steel substrates. Existing studies mainly focused on the cohesive failures in the adhesive; however, research on other types of failure modes is still limited. In this article, a series of single-shear bonded joints are prepared to investigate the bond behaviors of the carbon-fiber-reinforced polymer–steel interfaces based on carbon-fiber-reinforced polymer delamination failures and hybrid failures. Three kinds of adhesives—which have different tensile strengths and elastic moduli—and two kinds of carbon-fiber-reinforced polymer plates—which have different interlaminar shear strengths—are used to evaluate the influencing factors of carbon-fiber-reinforced polymer–steel interfaces. The three-dimensional digital image correlation technique is applied to measure the strain and the displacement on the surface of each specimen. The obtained test results include the strain distribution, the ultimate load, the failure mode, the load–slip curves, and the bond–slip relationships. For the carbon-fiber-reinforced polymer delamination mode, the results show that the load at the debonding stage is closely related to the interlaminar shear strength of the carbon-fiber-reinforced polymer plate, and the higher the interlaminar shear strength is, the greater the load. However, for the hybrid mode, the load of the whole test process is independent of the interlaminar shear strength of the carbon-fiber-reinforced polymer plate.
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Oukaili, Nazar K. Ali, and Iqbal Fadhil Peera Al-Hawwassi. "SHORT TERM DEFLECTION OF ORDINARY, PARTIALLY PRESTRESSED AND GFRP BARS REINFORCED CONCRETE BEAMS." Journal of Engineering 16, no. 01 (2010): 4631–52. http://dx.doi.org/10.31026/j.eng.2010.01.19.
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The behavior of structural concrete beams is studied under short-term loading. A computer program developed originally by Oukaili to evaluate curvature is modified to evaluate the deflection for flexural structural concrete members. The program deals with actual stress-strain relationships of concrete and steel. The analysis is based on requirements of equilibrium and compatibility of strain in concrete and reinforcement. The proposed model is used in conjunction with the step by step analysis for small loading increments that allows the determination of the history of strain and stress in concrete with prestressing steel or non-prestressing reinforcement only or prestressing and non-prestressing reinforcement together. The evaluation of curvatures for the structural member involves iterations for computing the strains vectors at each analysis step. Newmark's numerical integration is used to evaluate the deflection of the member depending on the curvature values. The stress-strain model that was proposed by (Korpenko et al. 1986) is used and compared with experimental data and other analytical models for each of concrete and steel. The comparison showed good agreement between the model used and the experimental data. This relationship is used in SECTION program and presented in this study. The analytical results for load-deflection diagram are compared with available experimental data. The comparison has shown good agreement.
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Liu, Xing Hui, Chuan Xiao Liu, Shuai Zhuang, Long Wang, and Shu Seng Lin. "Laboratory Studies on Acoustic Emission Characteristics to Coal Dynamic Response under Variable Accelerative Load." Applied Mechanics and Materials 580-583 (July 2014): 623–27. http://dx.doi.org/10.4028/www.scientific.net/amm.580-583.623.
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To simulate the fracture of the coal under impact load, uniaxial pressure test of coal which retrieved from KongZhuang coal mine-DaTun coal and electricity Company of China coal group was done in the manner of strain control which rest with a function of uniform variable acceleration. Through researches on the stress-strain relationships and acoustic emission characteristics, the relationship between ring count rate and time series was founded, and the process before failure of coal was divided into four stages: low-level ringing count rate, higher level, highest level and peaceful period. Through the comparison and analysis, it is founded that acoustic emission characteristics in the stage of higher level of ringing count rate can be regarded as a basis for the prediction of coal fracture. According to three obvious rise stages of acoustic emission signal in the process before failure of coal, growth factor of climbing speed is introduced and the values are calculated between 2 to 4, and it is conferred that the value of is proportional to compressive strength of coal and loading rate. It is of great significance for the prediction of coal fracture by acoustic emission characteristics in the stage of new cracks.