Plate Load Research Articles

Genetic analysis instrumentation innovations built into the SeqStudio ™ Flex Genetic Analyzers

The new Applied Biosystems™ SeqStudio ™ Flex Series Genetic Analyzer have improved the benchmark for research use only for Capillary Electrophoresis (CE) by providing innovative approaches to enhanced hand-free operation, flexibility, ease of use, data quality and connectivity. This newly designed 8 or 24 capillary system supports fragment sizing and DNA sequencing applications providing scientists with medium throughput technology for use in research applications. The steps from system set-up to size or base-called data have been simplified with hardware functionality and user-friendly software enhancements designed into this new CE system.We will discuss innovations related to ease of use including one button start-up, an on-board computer with touchscreen, intuitive software, easier to use capillary arrays, and desktop and cloud-based plate manager software. Innovations related to increased flexibility include continuous plate loading, automated plate linking that be able to maintain traceability from sample to result when using barcoded plates, urgent sample reprioritization, fragment and sequencing samples be run on the same plate, and multi-user support will also be discussed. In addition, gold standard fragment analysis and sequencing data quality has been enhanced through innovative algorithms providing autospectral calibrations, and off-scale recovery of data for fragment analysis. Innovative service and support functionality including remote troubleshooting with instrument system login capability, and on-board instrument help videos are included. Finally, we will touch upon new connectivity, which includes Thermo Fisher connect for remote monitoring, analysis, and data sharing as well as other functionality such as voice commands and Wi-Fi capability that the system will provide. The following summarizes highlights from the developmental validation performed to demonstrate the functionality of SeqStudio ™ Flex Series Genetic Analyzer.

Equations for Calculating the Foundation Settlement of Zhanjiang Formation Gray Clay Considering the Influence of Multiple Factors

The Zhanjiang Formation gray clay has physical properties similar to the muddy clay of other areas, such as a large void ratio and high-water content. At the same time, it also has mechanical properties that differ from muddy clay in other areas, such as high strength and low compressibility. When calculating the foundation settlement, the equation that calculates the foundation settlement as suggested by the code tends to produce values of compression modulus that are too small, which leads to larger calculated values. This study investigated the relationship between the pressure and deformation of Zhanjiang Formation gray clay foundations with different densities, water content, and stress histories by means of a plate loading model test. It revealed the influence of these factors on the deformation modulus, and the quantitative relationship between this modulus and the density of soils, water content, and the over consolidation ratio was established. In doing so, the aforementioned quantitative relationship was applied to the equation which calculated the foundation settlement as suggested by the current code, thereby proposing a pertinent formula relevant to Zhanjiang Formation gray clay foundations. The formula was subsequently applied to two engineering examples, and the settlement amounts output were in agreement with actual measured values, indicating it is reasonable and feasible for practical application. Therefore, it can provide a reference for the calculation of foundation settlements across the coastal area of Beibu Gulf.

Critical Loads of Uniformly Compressed Orthotropic Rectangular Plate on an Elastic Base

Introduction. The problem of critical loads of a compressed orthotropic rectangular plate on an elastic base was considered. The following orthotropy parameters were set for the plate: Poisson coefficients, Young's modules for the main directions, and the shear modulus of the plate material. The components of the compressive load were uniformly distributed along two opposite edges of the plate and acted parallel to the coordinate axes. The edges of the plate were loosely pinched or pivotally supported. Cases were also considered when two parallel edges of the plate were free from loads, and the other two were freely pinched or pivotally supported.Materials and Methods. The problem was studied on the basis of a system of nonlinear Kármán-type equilibrium equations. The critical values of the load parameter were determined from a linearized problem based on a trivial solution. At the same time, the variational method in combination with the finite difference method was used to solve the boundary eigenvalue problem.Results. The problem was reduced to solving a parametric linear boundary eigenvalue problem. In case of boundary conditions of a movable hinge support, exact formulas of eigenvalues and eigenfunctions were given. While in case of free edge pinching, a variational method was used in combination with a finite-difference method, and a computer program for solving the problem was built. It was established that one or two eigenfunctions expressing the deflection of the plate could correspond to the critical value of the compressive load parameter at which the stability of the compressed plate was lost. The results of numerical calculations of the critical values of the compressive load at different values of the orthotropy parameters were presented, and graphs of the corresponding equilibrium forms were constructed. For the case of a long orthotropic plate on an elastic base, it was established that the main term of the asymptotic expansion of the solution to the linear eigenvalue problem was determined from the problem of critical loads of a compressed beam on an elastic base with an elastic modulus that coincides with the elastic modulus of the plate in the longitudinal direction.Discussion and Conclusions. The problem of critical loads of an orthotropic plate compressed in two directions lying on an elastic base was investigated. As the compressive load component increased along one direction, the critical value of the load compressing the plate along the other direction decreased. If an orthotropic plate was compressed by a load along a direction that corresponded to a greater bending stiffness, then the critical value of the loss of stability was greater than the critical value of the compressive load acting along the direction of a lesser bending stiffness. The presence of an elastic foundation increased the bearing capacity of the compressed plate.

Size-Dependent Buckling and Post-Buckling Analysis of the Functionally Graded Thin Plate Al-Cu Material Based on a Modified Couple Stress Theory.

Size-dependent functionally graded material thin plate buckling and post-buckling problems are considered using the framework of the MCST (Modified Couple Stress Theory). Based on modified couple stress theory and power law, the post-buckling deflection and critical buckling load of simply supported functionally graded material thin plate are derived using Hamilton’s minimum potential energy principle. The analysis compares the simulation results of linear buckling and nonlinear buckling. Innovatively, a power-law distribution with scale effects is considered. The influences of scale effect parameters l and power-law index parameters k on buckling displacement, load, and strain energy of plates have been investigated. In this article, it is found that the critical buckling displacement, critical buckling load, and buckling strain energy increase with increases in the power-law index parameters k. The membrane energy decreases as the power-law index parameter increases. If the upper and lower layers are swapped, the opposite result is obtained. In comparison, the scale effect parameter is more influential than the power-law exponent. The critical buckling displacement in the x-direction is not affected by scale effects. The critical buckling load, the membrane energy, and buckling strain energy increase as the scale effect parameter increases. Scale effects increase material stiffness compared with traditional theory, and the power-law index parameters affect FGM properties such as elastic modulus, Poisson’s ratio, density, etc. Both scale effects parameters and power-law index parameters have important effects on the mechanical behavior of materials.

Full-scale test of Direct-buried Cable in Sand under Repetitive Loading

Direct-buried cable construction can minimize cumbersome processes, thereby decreasing construction time and cost. However, there is no regulation on burial depth that consider the long-term performance of backfilling soil for direct-buried cables. This study examines the mechanical response of direct-buried cables subjected to repetitive loads. This experimental study uses a full-scale chamber to replicate field construction. The stress on the cable, vertical displacement on the surface, and shear wave velocity between loading plate and cable are continuously monitored during 10,000 repetitive loading cycles. A miniature electrical cone is used to indirectly quantify the initial relative compaction. Repetitive loading densifies the soil around the cable, increasing stress on the cable and accumulating vertical strain. The trends are more pronounced with lower initial relative compaction. The shear wave velocity increases during repetitive loading, suggesting a change in the earth pressure coefficient. Applied stress – vertical strain allows the estimation of resilient modulus. These observations will provide a better understanding of the mechanical response of backfilling soil. Additionally, the uniaxial compression test of the underground power cable made for direct burial is conducted to measure the displacement of the cable insulator under the field condition obtained from the full-scale test. Then mechanical stability of the cable is investigated based on the axial displacement of the cable insulator.

Analysis of Flexural Bearing Capacity and Failure Mode of Precast LSFRC Pavement Slab

To promote practical use of the top-and-bottom layered steel fiber reinforced concrete (LSFRC) plates, an appropriate constitutive model is selected using ABAQUS software to analyze the bearing capacity, failure pattern, and deformation of the LSFRC plates. An LSFRC plate model is established for the analysis and calculation. Meanwhile, a test was carried out to measure the bearing capacity of 10 LSFRC plates. The results show that, after going through the elastic stage, crack growth, and failure stage, when the maximum crack width reaches 0.1 mm, the load of the LSFRC plates can be used as the ultimate bearing load. When failure appears to be bending the LSFRC plates, the neutral axis will shift upwards, showing a pseudoplastic failure. There is a larger tensile stress area after the first crack appears at the bottom of the steel fiber concrete. The change before and after the maximum load is relatively gentle. After becoming plastic, the plate witnesses a rapid crack growth on its bottom. With similar results from the test and numerical simulation, small errors can be minimized by further analysis to provide a more accurate model for the subsequent bearing capacity analysis of the LSFRC plates.

Estimating the Buckling Load of Steel Plates with Center Cut-Outs by ANN, GEP and EPR Techniques

Steel plates are used in the construction of various structures in civil engineering, aerospace, and shipbuilding. One of the main failure modes of plate members is buckling. Openings are provided in plates to accommodate various additional facilities and make the structure more serviceable. The present study examined the critical buckling load of rectangular steel plates with centrally placed circular openings and different support conditions. Various datasets were compiled from the literature and integrated into artificial intelligence techniques like Gene Expression Programming (GEP), Artificial Neural Network (ANN) and Evolutionary Polynomial Regression (EPR) to predict the critical buckling loads of the steel plates. The comparison of the developed models was conducted by determining various statistical parameters. The assessment revealed that the ANN model, with an R2 of 98.6% with an average error of 10.4%, outperformed the other two models showing its superiority in terms of better precision and less error. Thus, artificial intelligence techniques can be adopted as a successful technique for the prediction of the buckling load, and it is a sustainable method that can be used to solve practical problems encountered in the field of civil engineering, especially in steel structures.

Post buckling responses of carbon nanotubes’ fiber reinforced and nanoclay modified polymer matrix hybrid composite plate under in-plane buckling load using the higher order shear deformation theory

The buckling response of carbon nanotubes’ fibers (CNTs’ fibers) reinforced and nanoclay modified polymer matrix hybrid nanocomposite plates under in-plane buckling loads (IBLs) is studied using the efficient finite element method (FEM) based on a higher order shear deformation theory (HSDT). The conventional carbon fibers are reinforced in polymer matrix materials of cross-ply and angle-ply CNTs’ fibers reinforced and nanoclay modified polymer hybrid nanocomposite plates. The material properties are discussed using modified Halpin-Tsai relationships. An interactive MATLAB program based on FEM is developed to evaluate the critical buckling load (CBL) of a hybrid nanocomposite plate through a minimum potential energy approach. The hybrid nanocomposite plates subjected to in-plane buckling loads (IBLs) are studied in detail for their linear and nonlinear responses with respect to the critical buckling load (CBL) and variations in (a) load ratio of the laminated hybrid plate, (b) amplitude ratio, (c) carbon nanotubes’ fibers and nanoclays’ particles, (d) inplane buckling loads such as uniaxial, biaxial, shear, uniaxial with shear, and biaxial with shear, (e) stacking sequences, (f) buckling modes, and (g) length-to-diameter ratio. The results of the simulations are in fairly good agreement with the previously published sources.

Field Test Study on Vertical Bearing Characteristics of Coal Rock

Coal rock is rarely used as the foundation bearing strata. For buildings located on coal rock, it is a reasonable and feasible way to obtain the vertical bearing characteristics of coal rock through field tests. Three plate load tests and two bi-directional load tests were carried out, and the design parameters of the vertical bearing capacity of the shallow foundation and the deep foundation were obtained, respectively. The plate load test results show that the pressure–settlement curve of coal rock is a steep-drop-type, and the deformation modulus decreases with the increase of the pressure. The bi-directional load test results show that the unit tip resistance-displacement curve of coal rock is a steep-drop-type, and the load transfer function of the unit tip resistance is an ideal elastic–plastic curve, and the displacement value corresponding to the ultimate bearing capacity is about 1% of the pile diameter. The load transfer function of the unit side resistance of coal rock is a hyperbolic curve. The equivalent pile top load–settlement curve obtained according to the load transfer functions of the unit tip resistance and the unit side resistance is consistent with the equivalent conversion results of the bi-directional load test method.

Prediction of transverse stability of composite micro-curvature plates

This article is focused on the instability of marine composite micro-curvature plates subjected to transverse load, which is different from the axial loading case. The jump instability mechanism of orthogonal laminated plates has been analyzed, and transverse stability is predicted through the modified formula. Based on the classical elastic stability theory, suitable transverse stability analysis models for cylindrical and spherical shells are proposed. The instability load of the plate is predicted theoretically. The influential factors of the instability load are methodically analyzed based on an orthogonal experiment. Finally, according to the correlation analysis results of design variables, the calculation formula of the instability load is appropriately modified by considering the chord length of the plate. The obtained results show that the thickness has the most significant effect on the instability load, followed by the radius and the chord length. The instability load formula based on the elastic stability theory does not consider the chord length, which leads to low accurate results for the case of unclosed structures such as spherical crown plates. A comparison study confirms that the predicted results by the modified formula are generally closer to the experimentally observed data for the unclosed micro-curvature plate. In the present investigation, the load-bearing capacity of plates is evaluated in conjunction with the theory, nonlinear numerical simulation, and experimental research. Further, it can be applied to the theoretical prediction of the instability load for composite micro-curvature plates.

FIELD TESTS OF SOILS DURING THE INVESTIGATION WORKS

The study of road bases located on subsidence soils is a relevant issue because even though these soils demonstrate considerable strength in a dry state when soaked, they can exhibit sudden subsidence, which can lead to irreparable consequences during the operation of the highway. This article presents the results of laboratory studies of physical and mechanical properties of the soil, the results of field tests of the embankment by plate load test, which in combination provide a completer and more accurate picture of the state of the soil for further design of the highway with minimal costs and losses.

Mesoscale numerical investigation on the size effect of concrete uniaxial compressive strength under different contact friction

• The concrete mesoscale concretization model is established to consider the heterogeneity of meso-components. • The effect of contact friction on the compressive failure behavior of concrete is studied. • Increasing the friction coefficient makes the size effect more pronounced. • A modified size effect law DHF-SEL is established. The purpose of this work is to examine the quantitative influence of contact friction on the compressive strength of concrete and the corresponding size effect under uniaxial compression. The concrete mesoscale concretization model (CMCM) is established to consider the heterogeneity of meso-components based on the statistical distribution and local spatial correlation theory. The interaction between concrete and steel loading platens is evaluated by defining the contact friction behavior. The uniaxial compression behavior of concrete with different cross-section diameters, height-diameter ratios, and friction coefficients is simulated to analyze the quantitative effect of contact friction. The numerical results show that the hoop effect caused by contact friction constrains the lateral deformation and damage initiation at the loading boundaries of concrete, thus increasing the compressive strength; when the friction coefficient μ = 0 , the slight size effect is mainly caused by the wall effect, while when the friction coefficient μ > 0 , the severe size effect is primarily driven by the contact friction constraint; increasing the friction coefficient improves the sensitivity of compressive strength to sample size, making the size effect more pronounced. The Size Effect Law considering the diameter, height-diameter ratio and friction coefficient (DHF-SEL) is proposed based on the classical Bažant size effect law and CMCM, and then verified with the numerical results and experimental data.

A New Shear Locking-Free Quadrilateral Plate Element for Free Vibra-tion and Eigen-Buckling Analysis

A new plate element has been formulated by simply adding one degree of freedom for each node on the basis of the classical ACM element, based on a modified first-order shear deformation plate theory, which assumes that the plate deflection has bending and shearing components, with two rotations defined by differentiations of bending deflections. This new element, with 16 degrees of freedom, exhibits no locking effect, and is appropriate for both thin and thick plates.
 To assess the performance of the newly developed plate element, it has been applied to the prediction of natural frequencies and critical bucking loads of square plates with various thickness ratios and boundary conditions. Comparisons with available analytical and numerical solutions in open publication show that the new element leads to highly accurate solutions in free vibration and eigen-buckling analysis with good convergence, and can be competitive with existing plate elements.

Lime Treatment of Lake Texcoco Clays with Some Insights on the Application of Deep Mixing Columns

The soils across Lake Texcoco (LT) basin are notorious for the presence of highly compressible salt-affected lacustrine clays. The geological formation of the area accompanied by the unmonitored flow of water from Mexico City region has resulted in a unique sodium-rich clay that is highly plastic (plasticity index~200), and impermeable ( k~1.5 × 10−9 m/s) and possesses low compressive strength (unconfined compressive strength < 10 kPa). Over the last few decades, the entire basin has settled at an average of 13.2 cm per year and will continue further with increased loads as a result of rapid urbanization. In planning a solid foundation for the airport, as well as developing the surrounding area, trial sections were built to analyze the effect of quicklime (CaO) on the natural clay s physical, chemical, and engineering properties through laboratory testing. The lab-scale investigations were accompanied with field measurements using the variable energy dynamic cone penetrometer (DCP) and plate load tests. Additionally, a numerical analysis of the effect of deep mixed columns (DMC) to reduce consolidation settlement was performed. The numerical analysis comprised of various DMC stabilizers, loading pressures, column lengths, and area replacement ratios. DMC lengths were observed to be the most dominant parameter to reduce consolidation settlements. Settlement reduction was more sensitive to the area replacement ratio for end-bearing columns, and to the loading pressures for floating columns. Based on the stabilizers evaluated, a combination lime and Portland cement performed the best across all loading pressures and column lengths. Other stabilizer combinations also had a remarkable effect on limiting the consolidation settlement.

Behavior of floating stone columns reinforced with geogrid encasement in model tests

The bearing capacity and deformation characteristics of floating stone columns were complicated and are not thoroughly understood. In the present study, a series of experimental model tests of floating stone columns under vertical plate loading was performed. This study investigated the influence of geogrid encasement on the behavior of floating stone columns and provided valuable insight into the load-displacement behavior, bulging deformation, load transfer mechanism, and the radial stress of the geogrid encasement. The test results show that the bearing capacity of the floating stone column was significantly improved due to the geogrid encasement. The column with longer encasement showed higher stiffness at large settlements. The bulging deformation pattern of the column changed with different encasement lengths. More vertical pressure transferred from the top of the column to the bottom of the column due to the existence of the geogrid encasement. The fully encased stone columns developed high radial stress and achieved effective confinement of the column. The bearing capacities of the floating-encased stone columns with different encasement lengths were controlled by bulging deformation instead of penetration failure, which gave confidence that the floating-encased stone columns were an effective method for field construction in extensive soft soils.

ON THE QUESTION OF THE STABILITY OF SHELLS, PLATES AND RODS

Strict, often conflicting requirements are imposed on modern engineering structures. On the one hand, they must be light, and on the other hand, their load-bearing capacity must be high. The exhaustion of the bearing capacity often occurs due to the loss of stability of structural elements: shells, plates and rods. There are no reliable formulas for determining the critical loads of plates and, moreover, shells. The purpose of this paper is to find such formulas. A new approach to solving stability problems is used, based on the assumption that at the moment of stability loss, the axial compressive force decreases. Based on this approach, by the energy method using the relations of the general linear theory of thin-walled shells, formulas were obtained for calculating the axial critical forces of cylindrical shells with hinged and rigidly embedded ends, rectangular plates and rods. The results of critical load calculations using these formulas are in good agreement with the experimental data. The results of an experimental study of the stability of cylindrical shells reinforced with stringers under axial compression are presented. Conclusions are drawn and recommendations are given on the use of the proposed approach for further study of the stability of thin-walled structures.

Isogeometric Analysis of Graphene-Reinforced Functionally Gradient Piezoelectric Plates Resting on Winkler Elastic Foundations.

In this paper, the refined plate theory (RPT), Hamilton’s principle, and isogeometric analysis (IGA) are applied to investigate the static bending, free vibration and buckling behaviors of functionally graded graphene-platelet-reinforced piezoelectric (FG-GRP) plates resting on a Winkler elastic foundation. The graphene platelets (GPLs) are distributed in polyvinylidene fluoride (PVDF) as a power function along the plate thickness direction to generate functionally gradient materials (FGMs). The modified Halpin–Tsai parallel model predicts the effective Young’s modulus of each graphene-reinforced piezoelectric composite plate layer, and the rule of the mixture can be used to calculate the effective Poisson’s ratio, mass density, and piezoelectric properties. Under different graphene distribution patterns and boundary conditions, the effects of a plate’s geometric dimensions, GPLs’ physical properties, GPLs’ geometric properties and the elastic coefficient of the Winkler elastic foundation on deflections, frequencies and bucking loads of the FG-GRP plates are investigated in depth. The convergence and computational efficiency of the present IGA are confirmed versus other studies. Furthermore, the results illustrate that a small amount of GPL reinforcements can improve the FG-GRP plates’ mechanical properties, i.e., GPLs can improve the system’s vibration and stability characteristics. The more GPL reinforcements spread into the surface layers, the more effective it is at enhancing the system’s stiffness.

EVALUATION OF PLATE LOAD TEST RESULTS: A CASE STUDY IN ANKARA/TURKEY

Plate load test is widely used for bearing capacity and settlement calculations of foundations. In this study, 6 plate load tests were carried out to determine the bearing capacity and settlement of the foundation. High-speed railway project will be constructed in related area. The project location is in Ankara/Turkey. Bearing capacity of the station platform building foundation was determined according to plate load test and finite element analysis. Finite element analysis (FEM) software, Plaxis 2D, was used for the understanding of the settlement behaviour of soil. Soil strength and deformation parameters were determined according to plate load test and finite element analysis. Elasticity theory was used for analytical solutions. Field measurements, finite element analysis (FEM) results and analytical solution were compared at final of the study. Finite element analysis (FEM) and elasticity theory settlement calculation results have a strong correlation with field observations.

Macro-mesoscopic Dynamic Responses of Turfy Soil under Multilevel Cyclic Loading with Different Waveforms Based on the Discrete Element Method

Turfy soil is a special soil with numerous undecomposed plant fibers and humus, which can be considered a soil-fiber mixture. In this paper, the macro-mesoscopic dynamic responses of turfy soil subjected to multilevel cyclic loading with different waveforms (triangular, square, sinusoidal) were investigated employing the discrete element method (DEM). The microscopic parameters of the DEM model were confirmed by laboratory tests and calibration procedures. The hysteresis between the applied and measured stress on the loading plates was discussed to determine the appropriate frequency before simulation. Macroscopically, the discrepancies, including the velocity of the loading plates, the deformation of the specimen, and sample size effect were investigated under these three waveform loadings. Microscopically, the differences in energy, coordination number, average normal contact force between pure and turfy soil, internal force alternation and bending degree of fibers in turfy soil were studied to disclose the discrepancies in macroscopic behaviors with different waveforms. Simulation results illustrate that square waveforms can excite the support of the soil matrix by plant fibers in turfy soil to a greater extent. This study is beneficial for further understanding the mechanical behaviors of soil-fiber mixtures under the action of different forms of cyclic loads in safety engineering.

Effect of steel fibers on the shear behavior of Self-Compacting reinforced concrete deep Beams: An experimental investigation and analytical model

The shear behavior of reinforced concrete deep beams made of self-compacting concrete with different volume fractions of discrete macro steel fibers (0.5%,1.0%, and 1.5%) is studied. All the beams are tested at shear span to depth ratio of 1.0, and the effect of loading plate width on shear carrying capacity is also studied. Similarly, the effectiveness of steel fibers in improving the shear behavior is compared with the beams made of plain concrete and the beams with 0.3% web reinforcement in both horizontal and vertical directions. Test results revealed that the addition of macro steel fibers significantly improved the performance of deep beams, particularly first cracking load, ultimate shear capacity, ultimate deformation, and ductility. However, the addition of steel fiber more than 1.0% volume fraction did not increase the ultimate shear capacity. A simplified analytical model is proposed to predict the ultimate shear capacity of steel fiber reinforced concrete deep beams. The existing cracking strut and tie method (CSTM) is extended to include the effect of fibers, and a simplified fiber-reinforced cracking strut and tie method (FR-CSTM) is proposed. Predictions of FR-CSTM are compared with CSTM and two-parameter kinematic theory (2PKT). The comparisons of predictions with test results and existing models show that the proposed method can capture the ultimate shear capacity of deep beams with reasonable accuracy.