Lateral Compressive Stress Research Articles

Hydrogen-Induced Microstructure Changes in Zr/Nb Nanoscale Multilayer Structures

Zr/Nb nanoscale multilayer coatings (NMCs) were studied after hydrogenation in a gaseous environment at 400 °C. The hydrogen distribution and content were determined by pressure and hydrogenation time. Increasing the pressure from 0.2 to 2 MPa resulted in different hydrogen distribution within the Zr/Nb NMCs, while the concentration remained constant at 0.0150 ± 0.0015 wt. %. The hydrogen concentration increased from 0.0165 ± 0.001 to 0.0370 ± 0.0015 wt. % when the hydrogenation time was extended from 1 to 7 h. The δ-ZrH hydride phase was formed in the Zr layers with Zr crystals reorienting towards the [100] direction. The Nb(110) diffraction reflex shifted towards smaller angles and the interplanar distance in the niobium layers increased, indicating significant lateral compressive stresses. Despite an increase in pressure, the nanohardness and Young’s modulus of the Zr/Nb NMCs remained stable. Increasing the hydrogen concentration to 0.0370 ± 0.0015 wt. % resulted in a 40% increase in nanohardness. At this concentration, the relative values of the Doppler broadening variable energy positron annihilation spectroscopy (S/S0) increased above the initial level, indicating an increase in excess free volume due to hydrogen-induced defects and changes. However, the predominant positron capture center remained intact. The Zr/Nb NMCs with hydrogen content ranging from 0.0150 ± 0.0015 to 0.0180 ± 0.001 wt. % exhibited a decrease in the free volume probed by positrons, as demonstrated by the Doppler broadening variable energy positron annihilation spectroscopy. This was evidenced by opposite changes in S and W (S↓W↑). The microstructural changes are attributed to defect annihilation during hydrogen accumulation near interfaces with the formation of hydrogen–vacancy clusters and hydrides.

Factors controlling the heterogeneity of shale pore structure and shale gas production of the Wufeng–Longmaxi shales in the Dingshan plunging anticline of the Sichuan Basin, China

Shale gas exploration in the Dingshan plunging anticline of the Sichuan Basin, China, has uncovered substantial Wufeng–Longmaxi shale reserves. However, substantial variations exist in shale gas content and production among the wells in this region. We investigated the geological factors and mechanisms influencing shale pore structure heterogeneity and shale gas content and production in the area. We conducted comprehensive analyses of mineralogy, geochemical characteristics, and petrophysical properties on the Late Ordovician Wufeng Formation–Early Silurian Longmaxi Formation shales. Shale samples were collected from a shallow well, Anwen-1, located in proximity to the Qiyueshan thrust fault within the Dingshan plunging anticline. Additionally, samples from Dingye (DY) 1 and DY 3 wells, located at varying distances from the thrust fault, were examined. We also integrated previously published data from two correlative sections in the southeastern margin of the Sichuan Basin, each at different distances from the thrust fault. The pore volume, specific surface area, and porosity of the shales were positively correlated with their total organic content (TOC). However, strong lateral compressive stress, often occurring near the regional thrust fault, attenuated the linear relationship between TOC and pore volume/porosity. Lateral compressive stress did not significant affect shale porosity and pore structure when the distance from the regional thrust fault exceeded approximately 15 km. The specific surface area of the shale was less affected by compressive stress. Moreover, carbonate cementation reduced porosity by sealing shale matrix pores and natural microfractures, reducing nanopore connectivity. Consequently, shale gas production is not solely influenced by shale gas content but is also significantly affected by carbonate cementation. Therefore, shale reservoirs located at relatively long tectonic distances from regional thrust faults (approximately 15 km) within the Dingshan plunging anticline exhibit high pore volume, porosity, and shale gas content, rendering them favorable for shale gas exploration.

Analysis of the stress state at the contours of underground horizontal workings of elliptical cross-section shape subjected to all-round uniform pressure

The results of the research to determine the stress state on the contours of underground horizontal excavations, the cross-section of which has the form of an ellipse of any size and shape are presented. When changing the intensity of tensile uniform pressure applied to the points of elliptical shape cross-section excavation contours, the given values of excavation depths, ellipse parameters and rock side spreading coefficient values, the areas of the contours with tensile and compressive stresses are identified. If the depths of workings of the considered form of cross-section change, the areas where tensile and compressive stresses act at given values of the intensity of tensile uniform pressure applied to the points of working's contours, ellipse parameters and values of the coefficient of rock lateral spreading are highlighted. The graphical images of the normal tangential stresses, acting on the contours of the considered workings are given. The ranges of intensity of the tensile uniform pressure, at which, depending on the depth of excavation, values of ellipse parameters and the coefficient of rock lateral spread, tensile and (or) compressive stresses act in the points of excavation contours have been determined. The given relations and results can be applied to calculate the values of the permissible values of all-round uniform pressure in the points of the workings contours and to determine the permissible depths of their embedding. As a criterion for determining the values of these values, the condition of absente on the contours of excavations of points in which the normal tangential stresses exceed the limits of tensile and compression strength of the rock can be accepted.

The functional switching on the operating modes of a piezoelectric semiconductor bipolar junction transistor via mechanical loadings

A nonlinear model was developed on piezoelectric bipolar junction transistors (PS-BJTs) subjected to mechanical loadings by disregarding the assumption of low injection and the approximation of depletion layer. It was found that a PS-BJT subjected to different mechanical loadings can exhibit distinct carrier flow directions, for example, a remarkable transition for an n+pn-type PS-BJT from a transistor unit with amplification capability to two parallel connected PN junctions by applying a pair of lateral tensile or compressive stresses at the emitter and collector interfaces. Further in-depth analysis revealed that shielding effect produced by base region carriers greatly varies according to different loading mode, which leads to changing degrees of mechanical reconstruction on emitter junction barrier. Consequently, an artificial electron pathway (AEP) is formed at the emitter junction by a specific loading configuration. It is just due to the form change of AEP to produce distinct carrier flow directions, which can realize multifunctional switching of electronic devices. In addition, we also found an interesting phenomenon that an AEP can be directly constructed to penetrate the emitter junction by applying mechanical loadings in the longitudinal direction such that electrons in emitter region can travel across the emitter interface directly to the collector region without regulated by the base current. Under that situation, the PS-BJT resembles a parallel combination of a PN junction and an NN junction. This research provides novel insights into the mechanical modulation of piezoelectric electronic devices and the design of novel logic circuits.

Flexural gravity wave interaction with an articulated heterogeneous plate within the paradigm of blocking dynamics

Surface gravity waves interact with the flexural waves to generate the flexural gravity waves whose characteristics are triggered for higher values of lateral compressive stress to generate multiple propagating wave modes. This investigation examines the scattering of obliquely incident flexural gravity waves due to articulation in two semi-infinite heterogeneous floating elastic plates in finite water depth within a blocking dynamics regime. The dispersion curve demonstrates the existence of three propagating wave modes within the blocking limits. The canonical eigenfunction expansion method used for a single propagating mode is generalized to account for multiple propagating wave modes within the limits of blocking periods. The energy relation is established using the conservation of wave energy flux and Snell's law of refraction, which depends upon the angles and amplitude of the scattered waves along with the wave energy transfer rates. The amplitude of scattering coefficients (energy transfer rate) goes beyond the unit, where the corresponding energy transfer rate (scattering coefficients) diminishes for specific wave periods. Subsequently, complete wave reflection occurs for oblique waves beyond a critical angle of incidence for a fixed period and prior to a critical angle of incidence at a higher angle of incidence. Removable discontinuities occur at the blocking and saddle points, while a jump discontinuity appears due to a change in the incident wave mode in the scattering coefficients. Surface plots reveal the irregular pattern of plate deflection for the period within the blocking limits. Linear time-dependent plate displacement is simulated in two and three dimensions.

Modeling of Void‐Mediated Cracking and Lithium Penetration in All‐Solid‐State Batteries

AbstractAll‐solid‐state batteries (ASSBs) are expected to have an exceptional energy density and safety owing to the possibilities of direct usage of lithium as an anode and the suppression of dendrites by a solid‐state electrolyte (SSE). However, recent experiments unveil discharging‐induced voids in lithium‐SSE interfaces and charging‐induced cracks in SSE, wherein lithium penetration occurs. To avoid such cell failures, a theoretical model rendering high‐credibility simulations is needed to assist ASSB designs. Herein, such a model coupling the electrochemical processes and mechanical responses of an ASSB are proposed, in which the kinetics of voids and cracks are the key ingredients. Numerical simulations based on the model reveal that void growth is the result of stripping with disparate diffusivity in the surface layer and the bulk of lithium. They bring about the non‐uniform distribution of Li+ during electroplating, a damage zone near the interface, SSE cracking, and then lithium plating in the cracks. It is noted that the cracks and lithium dendrites revealed by the simulations are very similar to those observed in in situ experiments and that a high stack pressure cannot inhibit cracking and lithium penetration. Instead, suitable lateral compressive stresses can prevent SSE from cracking and therefore inhibit lithium dendrites.

Finite-Element Modeling of FRP-Confined Noncircular Concrete Columns Using the Evolutionary Potential-Surface Trace Plasticity Constitutive Model for Concrete

The compressive behavior of fiber-reinforced polymer (FRP)-confined concrete columns with a noncircular cross section has been investigated through extensive experimental, analytical, and numerical research, but a unified theoretical/numerical approach that can accurately predict both their section-average behavior and local concrete behavior is not yet available. In noncircular columns under axial compression, the concrete is typically under a nonuniform stress state of three-dimensional (3D) compression, with the lateral compressive stresses being the reactive stresses from the confining device (i.e., passive confinement). The authors of the present paper recently developed a plasticity constitutive model for concrete under general 3D compressive stresses, which possesses a potential surface with an evolutionary deviatoric trace that can accurately capture the results of existing compression tests of concrete cubes under nonuniform, passive confinement. This paper explores the application and capability of this evolutionary potential-surface trace (EPT) plasticity constitutive model in finite-element (FE) analysis of FRP-confined square, rectangular, and elliptical plain-concrete columns under concentric compression. The section-average behavior of all the selected noncircular columns predicted by these FE analyses was close to the existing experimental data. The numerical results obtained with the EPT plasticity constitutive model were then examined in detail to achieve an improved understanding of local concrete behavior in FRP-confined noncircular columns.

Lateral compression of lipids drives transbilayer coupling of protein condensates.

Protein phase separation that is restricted to a two-dimensional lipid membrane has recently gained much attention due to its involvement in various cellular processes. Two popular in vitro model membrane systems, giant unilamellar vesicles (GUVs) and supported lipid bilayers (SLBs), have been used to study it. However, due to the accessibility to only one side of the membrane in these systems, protein phase separation on both sides of the membrane remains unexplored. Here, we introduce a freestanding planar lipid membrane array as an effective platform to study membrane-associated protein phase separation. Protein condensates on the membrane display liquid-like features, and environmental stimuli, such as salt concentration and temperature, effectively control the observed phase separation results in our system with the application of several intrinsically disordered proteins. Interestingly, we observe transbilayer coupling of protein condensates such that protein-rich domains on one side of the membrane are found to colocalize with those on the other side of the membrane. How do these protein phases communicate across the lipid bilayer? Based on data from lipid probe partitioning and photobleaching experiments, we hypothesize that protein condensation on the membrane exerts lateral compressive stress on the underlying lipids, driving the formation of lipid domains with reduced fluidity. Specifically, lipid domains with reduced fluidity and increased lipid packing, formed by protein condensation on each membrane leaflet, are attracted to one another, leading to transbilayer coupling of protein condensates. These findings suggest a previously unknown mechanism by which cellular signals from one membrane leaflet, triggered by membrane-associated protein phase separation, can be transferred to the opposing leaflet.

Experimental Study and Failure Criterion Analysis of Rubber Fibre Reinforced Concrete under Biaxial Compression-Compression

In order to examine the biaxial compression-compression properties of rubber fibre reinforced concrete (RFRC), an experimental study on RFRC under different lateral compressive stresses was carried out by considering different rubber replacement rates and polypropylene fibre contents. The failure modes and mechanical property parameters of different RFRC working conditions were obtained from the experiment to explore the effects of rubber replacement rate and polypropylene fibre content on the biaxial compression-compression properties of RFRC. The following conclusions were drawn. Under the influence of lateral compressive stress, the biaxial compression-compression failure mode gradually developed from a columnar pattern to a flaky pattern, suggesting that the incorporation of rubber and polypropylene fibres into the concrete resulted in a significant change in the development of cracks. For different rubber replacement rates and polypropylene fibre contents, the vertical compressive stress exhibited the same developing trend under the influence of lateral compressive stress. Specifically, the lateral compressive stress imposed the minimum effect on the vertical compressive stress when the rubber replacement rate and polypropylene fibre content were 20% and 0.4%, respectively, and imposed the maximum effect when the rubber replacement rate and polypropylene fibre content were 20% and 0%, respectively. With the increase of rubber replacement rate, the vertical peak stress was significantly reduced, which implies that an appropriate amount of polypropylene fibres can increase the vertical peak stress to a certain extent. Then, the biaxial compression-compression mechanism of RFRC was analysed from the microscopic level by using scanning electron microscope (SEM). Meanwhile, based on Kupfer’s biaxial compression-compression failure criterion and the octahedral stress space, a biaxial compression-compression failure criterion for RFRC was proposed, which was proven to have good applicability. The research results of this study provide important theoretical basis for the engineering application and development of RFRC.

Experimental study on direct shear performance of prefabricated splicing joints of ultrahigh-performance concrete

Splicing joints are the weak link of precast ultrahigh-performance concrete (UHPC) segmental bridges (PUSBs). Thus, this paper conducts direct shear tests on eight groups of UHPC keyed joints to investigate the shear performance of the interface of the key. The effects of lateral compressive stress (σn) and the number of keys on the shear performance are also examined. In addition, the load–displacement curves, failure modes, cracking loads, and ultimate loads of the specimens with different parameters are presented. After that, the direct shear capacity of the joints is theoretically analyzed based on the test results and relevant specifications, and a formula for calculating the direct shear capacity is derived. The results show that the failure mode of the UHPC keyed joints is primarily brittle failure. Moreover, the failure mode is the direct shear failure along the interface of the key when the lateral compressive stress is low; however, it is the local crushing of concrete in the key when the lateral compressive stress is high. Additionally, the direct shear capacity of the specimens increases linearly with raising the lateral compressive stress. The direct shear capacity of the double-keyed joints is 17.4–29.3 % higher than that of the single-keyed joints under the same conditions. The values calculated by specifications NF P-18 710 and Eurocode 2 2011 are lower than the experimental ones. The experimental data are evenly distributed on both sides of the curve calculated by specification JSCE 2008 when the lateral compressive stress is low, posing potential hazards in this case. The value predicted by specification AASHTO 2003 is also higher than the experimental value. Finally, we derive a formula for calculating the direct shear performance of the UHPC keyed joints utilizing Mohr’s stress circle theory, and it can be applied to engineering design with high accuracy.

First-principles study of the microstructure evolution of the diamond (110) surface with the adsorption of Fe atoms

Understanding the diamond graphitization mechanism is an essential subject in manufacturing research since it helps elucidate the reason for the material removal. Our work addressed the mechanism of Fe-induced graphitization of diamond (110) surfaces (Dia-(110)-Surf) by first-principles calculations. The results pointed out that Fe atoms adsorbed at hollow sites could acquire the most stable configuration on the Dia-(110)-Surf. Meanwhile, the Fe adatom could change interlayer binding energies of CC bonds of various layered. As the amount of Fe atoms increased, the weakening/enhancement effect of CC bonds tended to be apparent. Interestingly, Fe adatoms not only changed interlayer binding energies of CC nearby but also affected the dissociation direction of the surface microstructure. The weakened CC bonds could provoke the flattening of the sixfold chair ring structure of C atoms. The extension direction of the sixfold chair ring structure changed from horizontal to oblique, resulting in eliminating lateral compressive stress. It might be the origin of the Fe-induced graphitization of Dia-(110)- Surf. Moreover, the migration behaviors of the Fe atom have been studied. It could be inferred that the migration activation energy and movement direction of Fe adatoms were associated with the material removal rate.

3D lattice meso-scale modelling of the effect of lateral compression on tensile fracture processes in concrete

The effect of lateral compressive stresses on the cracking process in tension is rarely considered in fracture models for quasi-brittle materials such as concrete. In this study, this effect is investigated by means of a meso-scale lattice approach in which a damage-plasticity constitutive model is combined with an auto-correlated random field of strength and fracture energy. In the first part of the analyses, the lattice approach is compared with experimental results in tension and compression, which shows a good agreement between simulations and experiments. Then, cells with periodic lattices and periodic boundary conditions are loaded in two steps. Firstly, compression is applied. Next, the cell is extended in the lateral direction while keeping the compressive stress constant. It is shown that with increasing compressive stress applied, the post-peak energy dissipation in tension increases. Postprocessing of the results of the analyses reveals that this increase is due to greater frictional energy dissipation and greater number of cracks than for pure tension.

Characterization of high-strength concrete under monotonic and fatigue mode II loading with actively controlled level of lateral compression

The fatigue behavior of plain concrete has been studied for decades, usually under compressive or tensile loading. Shear loading (mode II) has been almost completely neglected in the past. In contrast to cylindrical compression tests, this type of loading offers the advantage of precise load determination and a small, well-defined fracture surface. This paper presents a comprehensive experimental campaign of 66 shear tests, which was conducted to systematically investigate the monotonic, cyclic, and fatigue response of high-strength concrete under mode II loading. Since the material behavior under shear stress is strongly dependent on the concurrent lateral compressive stress, a new test setup was developed which allows simultaneous control of compressive and shear loading. One potential utilization for these shear fatigue tests is the validation of a promising hypothesis that suggests that the development of fatigue damage in concrete at subcritical load levels is governed by a cumulative measure of shear sliding. The qualitative influence of the lateral compressive loading on the displacement and damage development, fracture behavior, and fatigue life is analyzed and discussed. The test results indicate that there is no influence of the lateral compressive load level on the shear fatigue life, as long as the increase in shear strength is considered. Furthermore, concrete under mode II loading seems to have a longer fatigue life than concrete in standard cylindrical specimens under compressive loading.

Enhancement of oil repellency on hyperbolic microarrays by compressive bending of elastomeric films

Applying elastic deformation to modulate the microscale surface shapes of films is an efficient way to prepare samples with various geometric designs. Tensile stress can be applied by stretching films, and it can increase the pitches of line arrays or the diameters of pillar arrays on a film surface. However, it is difficult to apply lateral compressive stress to films because films buckle during compression. In this study, we exploit bending to apply lateral compressive stress to the surface of a film. To accomplish this, we use arrays of microhyperbolic pillars or lines that have inversely tapered shapes in the upper region and widened bottoms. By using deformation of elastomeric films and a subsequent replication process, we fabricate microhyperbolic structures with decreased pitches and increased pattern heights. In addition, the deformation of microarrays by compressive stress can enhance oil repellency by increasing the sharpness of the inversely tapered shapes. Using this concept, we demonstrate the enhancement of oil repellency on patterned surfaces prepared by compressive bending of microarrays. Furthermore, we provide selective oil repellency by modulating the compressive stress on a single line array. The concept of compressive bending can be applied widely to decrease the dimensions of arrays and modulate surface shapes for greater oil repellency.

Study on the mechanical behavior of L‐shaped concrete‐filled steel tubular columns under axial compression

AbstractIn this paper, a total of six different ribbed and two nonribbed L‐shaped concrete‐filled steel tubular (CFST) short columns are designed; finite element modeling and calculations are carried out and verified with measured results. The optimal ribbing method among the ribbing methods applied is proposed. The mechanisms of the longitudinal stress of the concrete, longitudinal stress of the outer steel tube, and lateral compressive stress of the concrete for the L‐shaped CFST short column without ribs and with the optimal ribbing method are compared and analyzed. The results show that the optimal ribbing method involves setting half‐width longitudinal stiffening ribs in the middle of the two wide sides of the L‐shaped steel tube. The stiffening ribs can delay the occurrence of local buckling failure of the steel tube, thus strengthening the restraining effect of the steel tube on the concrete and improving the uniformity of the longitudinal stress of the core concrete. In addition, based on an analysis of a large number of parameters, four methods for calculating the bearing capacity of nonribbed L‐shaped CFST short columns are compared. A design formula for the bearing capacity of ribbed L‐shaped CFST columns is proposed by considering the improvement in the concrete performance. The calculation results agree well with the finite element and experimental results, and the error is <5%.

An experimental study and failure mechanism analysis on dynamic behaviors of plain concrete under biaxial compression-compression

In order to explore the dynamic mechanical properties of concrete under biaxial compression-compression, a true triaxial instrument was used to conduct an experimental study on the dynamic mechanical properties of plain concrete under biaxial compression-compression. Eight different lateral compressive stresses (0 MPa~14 MPa) and four strain (10−5/s, 10−4/s, 10−3/s and 10−2/s) rate were considered. From this, the effects of lateral compressive stress and loading strain rate on the biaxial compression-compression properties of concrete were compared and analyzed by obtaining the failure modes, principal compressive stress-strain curves and related mechanical characteristic parameters of plain concrete under different loading conditions. The research results show that: with the increase of lateral compressive stress, the failure modes of concrete were developed from columnar failure at low lateral compressive stress to sheet-like failure at high lateral compressive stress. With the increase of lateral stress, the development trend of concrete failure mode decreased gradually under the influence of strain rate. With the increase of lateral compressive stress, the variation range of concrete principal compressive stress decreased first and then tended to be relatively stable under the influence of strain rate. With the increase of strain rate, the increase range of concrete principal compressive stress decreased under the influence of lateral compressive stress. The influence mechanism of lateral compressive stress and strain rate on biaxial compression-compression performance of concrete was analyzed. Meanwhile, based on Kupfer biaxial compression failure criterion, a biaxial compression dynamic failure criterion model considering the effect of loading strain rate on plain concrete was proposed. The research results provided an important theoretical basis for the application and development of concrete engineering.

Numerical and Experimental Study on End Effect of Waste-Soil Samples under Uniaxial Compression

In order to investigate the influence of end effect on the waste-soil sample strength under uniaxial compression, the influence law of end effect on the uniaxial compression strength is numerically simulated by the FLAC3D software, and the reliability of the numerical model is verified by comparing it with the test results. Based on the above model, the influence of end effect on the lateral displacement and stress state of waste-soil samples is simulated, and the formation mechanism of end effect under uniaxial compression is revealed. The results show that, when the friction coefficient increases from 0 to 0.4, the uniaxial compression strength and percentage of triaxial compression units first increase rapidly and then slowly and then finally remain invariant. With the increase of the friction coefficient, the lateral displacement of the sample is significantly reduced. On the end surface, the nearer to the edge one is, the greater the decrease is. The triaxial compression region on the axis section is triangular in distribution; with the increase of the friction coefficient, this region increases first rapidly and then slowly and then finally remains invariant. The end effect produces lateral compression stress by reducing the lateral displacement of the end surface of samples, and lateral compression stress causes the sample to enter the triaxial compression state. With the increase of the friction coefficient, the triaxial compression region increases gradually, and thus, the uniaxial compression strength of the entire sample increases.

Analysis of Biaxial Mechanical Properties and Failure Criterion of Self-Compacting Concrete

Biaxial compression-compression, biaxial tension-compression and compression-shear tests were carried out on self-compacting concrete (SCC) using the rock true triaxial machine and compression-shear hydraulic servo machine to explore the biaxial mechanical properties of SCC. The failure modes and stress-strain curves of SCC under different loading conditions were obtained through experiment. Based on the comparison with the biaxial loading test data of ordinary concrete, the following conclusions are drawn: the failure modes and failure mechanisms under biaxial compression-compression and biaxial tension-compression are similar between SCC and ordinary concrete. Under compression-shear loading, the oblique cracks formed on the lateral surface of the specimen parallel to the shear direction gradually increased and the friction marks on the shear failure section were gradually deepened with the increase of axial compression ratio. The development trend of the stress-strain curve in the principal stress direction was not related to the lateral stress. Under the influence of lateral compressive stress, the principal compressive stress of SCC was increased by 55.78% on average; under biaxial tension-compression, the principal tensile stress of SCC had a maximum reduction of 62.79%; and under the compression-shear action, the shear stress of SCC had a maximum increase of 3.35 times. Compared with the biaxial stress test data of ordinary concrete, it can be seen that the lateral compressive stress had a more significant effect on the principal stress of SCC under biaxial loading. Subsequently, the strength criterion equations of SCC under biaxial loading were proposed based on the principal stress space and octahedral space stress respectively, which have shown good applicability in practice.

A plasticity constitutive model for concrete under multiaxial compression

Structural members with confined concrete are becoming increasingly popular in civil engineering applications because of their superior strength and ductility. In these structural members, the concrete is subjected to dilation-induced (passive) lateral compressive stresses from the confining device (e.g., a steel tube). Existing research has led to theoretical models that predict closely the stress–strain behavior of concrete under uniform confinement (e.g., concrete in circular steel tubes under concentric axial compression), but theoretical models with a similar capability have not been achieved for the more common situation of concrete under non-uniform confinement (e.g., concrete in rectangular steel tubes). This paper presents a three-dimensional (3D) plasticity constitutive model that is accurate in predicting the stress–strain behavior of concrete in various scenarios of confinement. In the proposed model, a well-established open strength surface with associated open yield surfaces is combined with a hardening/softening rule compatible with both plastic volumetric compaction and dilation. In addition, a novel potential surface with a triangle-like deviatoric trace is proposed and calibrated with available experimental data of non-uniformly confined concrete. The implementation of the constitutive model in finite element analysis with an enhanced stress-return algorithm suitable for the novel potential surface is explained. While the focus of the present work is on monotonic compression-dominated loading, the model can be combined with fracture and damage theories to depict the behavior of concrete under tension-dominated and cyclic loading conditions. The performance of the proposed model is evaluated by comparing its predictions with a wide range of experimental data covering uniform active, uniform passive, and non-uniform passive confinement conditions, which demonstrates the capability and high accuracy of the proposed model.

Validation of Relative Motion Measurement Method of Lateral Compression Pelvic Fractures During Examination Under Anesthesia.

To determine if the relative distance between the acetabular teardrops on unstressed and lateral compressive stress examination under anesthesia (EUA) pelvic fluoroscopic images is reproducible between independent reviewers. Retrospective database review. Level 1 trauma center. Fifty-eight patients with a lateral compression type 1 pelvic ring injury who underwent EUA. Validation of EUA objective measurements between blinded, independent reviewers using interclass and intraclass correlation coefficients. There was excellent interobserver and intraobserver reliability between all reviewers. Values for each intraclass correlation coefficients (including 95% confidence intervals) were between 0.96 (0.95-0.098) and 0.99 (0.99-0.99) for all measurements. P values were <0.0001 for all measured parameters. The relative change in distance between the acetabular tear drops during lateral compressive EUA of lateral compression type 1 pelvic injuries is reliable between independent reviewers. This allows for accurate, objective measurement of pelvic motion independent of patient size or body habitus. Diagnostic Level III. See Instructions for Authors for a complete description of levels of evidence.