Hoop Strain Research Articles

Behavior of high-burnup BWR UO2 fuel with additives under reactivity-initiated accident conditions

ABSTRACT Fuels with additives are expected to provide enhanced fuel performance in fission gas retention owing to their large grain size, which elongates fission gas migration path. To investigate behavior of the fuels during a reactivity-initiated accident (RIA), RIA-simulated experiments OS-1 and LS-4 were performed on ADOPT (chromia- and alumina-doped UO2) fuel of 64 GWd/t and chromia-doped UO2 fuel of 48 GWd/t, respectively. The OS-1 rod failed at a fuel enthalpy increase of 160 J/g due to pellet–cladding mechanical interaction failure, which was the lowest failure limit among the test results ever obtained at the NSRR on high-burnup fuels from 40 to 65 GWd/tU. Comparison of the hydride morphologies in the cladding metallic layer between the rods subjected to the past NSRR tests suggests the contribution of radially oriented hydrides during base irradiation to the low failure limit. The LS-4 rod survived for a peak fuel enthalpy increase of 549 J/g, which resulted in cladding deformation of ~2.4% in the residual hoop strain and FGR of 1.4–6.1%. Whereas the low fission gas release exhibits the effect of additives, the cladding deformation is within the range explained by the deformation mechanism essentially identical to those recognized for high-burnup undoped fuels.

Effect of Aggregate Size on the Axial Compressive Behavior of FRP-Confined Coral Aggregate Concrete.

Using locally available raw materials for preparing concrete, such as coral reefs, seawater, and sea sand, is conducive to compensating for the shortage of construction materials used on remote islands. Jacketing fiber-reinforced polymer (FRP), as passive confinement, is a practical approach to enhance the strength, ductility, and durability of such coral aggregate concrete (CAC). Rational and economical CAC structural design requires understanding the interactions between the CAC fracture process and FRP confinement. The coral aggregate size is the critical parameter of their interaction since it affects the crack propagation of CAC and FRP confinement efficiency. This study conducted axial compression tests on FRP-confined CAC cylinders with varying coral aggregate sizes and FRP confinement levels. The test results indicate that the coral aggregate sizes affected the unconfined CAC strength. In addition, the dilation behavior of FRP-confined CAC varied with aggregate sizes, showing that CAC with smaller coral aggregate featured a more uniform hoop strain distribution and larger FRP rupture strain. These coupling effects are epitomized by the variation in the transition stress on the stress–strain curve, which makes the existing stress–strain models not applicable for FRP-confined CAC. A modified stress–strain model is subsequently proposed. Finally, the practical and environmental implications of the present study are discussed.

Effects of azimuthal temperature distribution and rod internal gas energy on ballooning deformation and rupture opening formation of a 17 × 17 type PWR fuel cladding tube under LOCA-simulated burst conditions

ABSTRACT In order to contribute to better modeling and evaluation of fuel fragmentation, relocation, and dispersal expected under loss of coolant accident (LOCA) conditions, LOCA-simulated cladding burst experiments were performed on as-received nonirradiated 17 × 17 type Zircaloy-4 cladding specimens that were internally pressurized. The experiments were designed to terminate at burst occurrence to focus on ballooning and rupture opening formation and to investigate the effects of various factors. The postburst cladding hoop strain decreased with the increase in azimuthal temperature difference (ATD) of the cladding, as found previously. The rupture opening size increased with the increase in ATD and the increase in energy of the pressurized gas stored inside the pressure boundary of the test sample system. Comparison with the existing database, which included tests on irradiated rods containing fuel pellets, suggested that formation of the rupture opening was influenced by the characteristic behavior of high burnup fuels, such as limited gas migration in the cladding tube due to fuel–cladding bonding and interaction of the ejected fuel fragments with the cladding tube.

A novel seawater and sea sand concrete-filled CFRP-carbon steel composite tube column: Seismic behavior and finite element analysis

The seismic behavior of a novel seawater and sea sand concrete (SSC)-filled carbon fiber-reinforced polymer (CFRP)-carbon steel composite tube (SFSCT) column under combined axial compression and reversed cyclic loadings was studied in this paper. This structure makes use of seawater and sea sand resources, and CFRP was adopted to isolate the corrosion by chloride ions on the steel tube. Tests of eight composite columns were carried out. The test parameters include the axial compression ratio, the number of CFRP layers and the bonding direction. The test results revealed that all of the specimens displayed superb seismic performance with a drift ratio over 4%. The failure of the SFSCT column exhibits a typical compressive-flexural failure mode. Compared with the results of the SSC-filled steel tube columns, the hoop strain of the specimen under additional CFRP confinement is reduced by 1.6 times, and the flexural strength and drift capacity increase by 22% and 17%, respectively. A fiber model was created by finite element analysis, and parametric studies of the main design parameters were performed. The effects of the steel tube and CFRP on the seismic performance were evaluated. Using experiments and finite element analysis, the relationships among the drift capacity, axial compression ratio and confinement level were investigated. A design method for predicting the drift capacity of SFSCT columns was proposed.

Development and evaluation of fuel performance analysis code FuSPAC

The nuclear fuel rod should maintain self-sustainable nuclear fission, as the first safety barrier to prevent the leakage of radioactive products. The fuel rod performance analyses are essential to ensure reliable long-term operation of fuel rod. In this work, the fuel performance analysis code FuSPAC is developed based on the commonly used 1.5-dimensional method for UO2 ceramic fuel with Zirconium cladding. The physical and numerical models used in FuSPAC code are described. By comparing the predicted values from FuSPAC code with the available in-reactor fuel rod experimental data and the numerical results from the well-recognized FRAPCON code, the capacity of FuSPAC code on the prediction of fuel pin and cladding under long term irradiation conditions are validated from five aspects, including fission gas release behaviour, thermal behaviour, rod internal void volume, cladding corrosion and cladding hoop strain, showing good accuracy in the behaviour analysis of the irradiated UO2 fuel rod.

Finite element analysis of square FRP-Concrete-Steel columns under concentric compression

The first objective of this paper is to propose a simple but rational and effective refinement to the concrete damage plasticity model (CDPM) used in the finite element (FE) analysis of confined concrete columns, in particular the damage parameter for columns with a post-peak descending path. The proposed damage parameter is based on an existing one, refined to account for the confinement effect. The FE analysis results demonstrate that the proposed damage parameter enables much more accurate tracing of the stress–strain paths of normal as well as high strength concrete columns confined by circular or square fibre-reinforced polymer (FRP) tube. The second objective is to use the resulting FE methodology to study the square FRP-Concrete-Steel columns tested previously by the first two authors, which had an outer FRP tube and an inner steel tube, both square. The FE analysis results confirm the experimental finding that the rotated inner steel tube typically led to better performance than the conventionally placed inner tube. At a given axial strain, the rotated configuration results in a larger area of high axial stresses in the concrete, corresponding to the area of higher confining pressures, but a lower maximum hoop strain (in the middle of the flat side) of the FRP tube.

Strain localization analysis using digital image correlation for PVA fiber-reinforced concrete-filled FRP tubes under compressive loading

This study presents the outcomes of the first experimental study on the strain localization of polyvinyl alcohol (PVA) fiber-reinforced concrete-filled fiber-reinforced polymer (FRP) tubes (CFFTs). 24 CFFT specimens were prepared and tested with various instrumentations, such as linear variable differential transformer (LVDT) and strain gauges (SGs), to record required full-field strains, i.e., axial, lateral and Von Mises strains. The strain evolutions over the surface of the specimens were recorded during axial compression loading. The FRPs were prepared with carbon, S-glass or basalt fiber to examine the influence of the fiber type and confinement stiffness on the behavior and strain localization of CFFTs. The evolution of Von Mises strains was determined and studied under axial compression. The obtained results show that although the general pattern of localization for both CFFTs without and with PVA fiber is nearly similar, the characteristics of the localization are different. The expansion of shear zone for insufficiently basalt FRP (BFRP)-confined concrete is more localized compared to the more homogenized behavior of sufficiently FRP-confined concrete. However, insufficiently BFRP-confined PVA fiber-reinforced concrete exhibits less localized behavior compared to insufficiently BFRP-confined plain concrete, which is due to the influence of the internal fibers on the concrete cracking behavior. At FRP rupture, hoop strains vary along the height and around the perimeter of the specimens, which results in the inability of SGs to consistently capture the actual hoop rupture strain.

Investigating the performance of stone columns in an extremely soft clay—A case study

SummaryStone columns are used to improve soft soils; however, they fail through bulging, punching, and lateral expansion when the soil is extremely soft. The present study investigated the performance of stone columns in an extremely soft clay (ESC) through the addition of the appropriate geosynthetic materials. Field test was conducted for the foremost purpose of obtaining the optimal spacing between the consecutive stone columns and therefore prevents the failures of stone columns in ESC soils. The study further examined the failure modes of stone columns for the case of ESC soils. The computer programming software FLAC 3D was used for modeling and simulation, while Auto CAD was used to draw needed geometries of the case study. The results revealed that the full encasement of the stone column with suitable geogrids, optimal spacing, and proper design of cushion will enable the efficient use of stone columns as a composite foundation in ESC. The considered appropriate thickness of the cushion was found to be 30 cm, and this cushion helps the embedded soft clay soils to work together with the installed encased stone columns in ESC soils. The center‐to‐center (optimal) spacing between two consecutive stone columns showed optimal performance at distance S ≤ 5d of the diameter of the stone column. These findings show that stone column encased with suitable geogrids and optimal spacing will improve the bearing capacity, reduce settlement, and decrease the lateral deflection as well as hoop strain of the foundation.

Experimental study and design of bond behavior in concrete-filled steel tubes (CFST)

Steel plate-concrete (SPC) and concrete filled steel tube (CFST) push out test specimens are conducted to study the nature of the bond behavior between the steel tube and concrete and the according contribution of each component (chemical adhesion, micro-interlocking and friction). A total of 10 SPC specimens considering lateral normal pressure applied on the concrete and 18 circular CFST specimens with reversed loading have been carried out, where the surface roughness of the steel tube and the length of the specimens have been considered as variables. The chemical adhesion contributions are obtained through the SPC specimens without normal pressures. The micro-interlocking and friction can be calculated through both the SPC and CFST specimens. The micro-interlocking coefficient concept has been proposed and determined together with the friction coefficient through SPC test specimens with normal pressures. Both the micro-interlocking and friction component contribution to the bond behavior can be determined through the steel tube hoop strain from the CFST specimens and the obtained coefficient accordingly. The bond mechanism of CFST specimen has been systematically and quantitively explained by analyzing the full-history developments of the chemical adhesion, micro-interlocking and friction components. A bond-slip constitutive model considering both the physical significance and prediction accuracy has been proposed and verified, which may promote refined numerical analysis.

Analytical Analysis to Predict the Generated Stresses and Strains of Laminated Composite Tube due to Internal Pressure

The aim of this study is to build a MATLAB code to predict the interlaminar radial strains, and stresses developed in a laminated composite tube. This code is only valid for symmetrical laminated composite tubes. The code can solve for tube that is subjected to uniform internal pressure. The written MATLAB code can save time and money compared to experiments and finite element simulations. Then, this code is validated with other published mentioned articles in this study. Good agreement is achieved which it means the built code can be used for the cases that agree with a symmetrical condition. The code is run to solve for radial, hoop, and shear strains. Also, it is used to solve for axial, radial, hoop, and shear stresses.

Study on mechanical response of steel pipe jacking considering the effect of pipe sticking

Pipe sticking is frequently occurred during the pipe jacking in rock strata due to the blockages accumulated in the annulus gap. The frictional resistance induced by surrounding rocks increased sharply, and the total jacking force might exceed the pipe structural capacity. Through the in-situ monitoring and direct shear tests, the influence of the pipe sticking on the deformation and frictional properties of the steel pipe jacking was analyzed. In the severe pipe sticking, the contact pressure acting on the pipe exceeded 1 MPa, and significant radial compression took place. The hoop strain of the pipe contacting with the blockages illustrated a tensile state, while the pipe contacting with the slurry or groundwater exhibited compressive strain. In the direct shear tests, the frictional properties of the steel pipe-rock interface under five contact conditions were evaluated. Experimental results revealed that the pipe-rock friction coefficient under the blockages exhibited as high as 0.6, and the blockages in annulus gap were the main reason for the increase in frictional resistance. In addition, the causes of the pipe sticking were analyzed, and measures were implemented to resolve the pipe sticking issue.

Experimental and theoretical study on concrete-filled T-shaped steel tubular columns under uniaxial eccentric compression

This paper presents an experimental and theoretical study on concrete-filled T-shape steel tubular (CFTST) beam-columns. Four full-scale slender beam-columns with slenderness ratio of 33.7–39.1 were tested under uniaxial eccentric compressive loads. In addition, three stub columns with the same cross-sections were axially compressed to investigate the confinement effect. Failure mode, axial displacement, lateral deflection, axial strain and hoop strain were obtained to understand the structural behavior of CFTST beam-columns. For beam-columns bended about the symmetric axis, torsion was not observed but a slight rotation of the neutral axis that was no longer parallel to the centroid axis was found by analyzing the experimental results. A fiber element model for CFTST beam-columns was developed and verified for parametrical analysis. The effects of key parameters, such as material properties, cross-section dimensions, loading angle and slenderness ratio, on the behavior of stub and slender beam-columns were investigated. Finally, theoretical models were proposed to estimate the interaction curve and the load-carrying capacity of CFTST beam-columns. The prediction matches well with the experimental results.

Behavior of confined concrete columns with HSSSWR meshes reinforced ECC jacket under uniaxial compression

This paper presents experimental and analytical studies on the uniaxial compressive properties and failure mechanics of confined concrete columns with a novel strengthening system, high-strength stainless steel wire rope (HSSSWR) meshes reinforced engineering cementitious composite (ECC) jacket. The effects of the formula of ECC, spacing of lateral HSSSWRs and concrete strength were considered in this experimental study. Test results showed this strengthening system can confine concrete columns effectively due to good bond performance between the jacket and concrete, which changed the concrete failure mode from brittleness to ductile failure and resulted in effective improvements in bearing capacity, deformation capacity, ductility and energy absorption capacity. Multiple fine cracks were observed in the confined concrete columns, which indicated the excellent crack-width controlling ability of the jacket. By embracing path-independence assumption and modifying the relationship of hoop strain and vertical strain for concrete columns confined by HSSSWR meshes reinforced ECC jacket, an analytical model for predicting the load–displacement curve of the HSSSWR meshes reinforced ECC confined concrete columns was developed. The predicted results by using the proposed analytical model were found in good agreement with the experimental results.

An investigation into the effect of pre-bending on the tube hydro-forging technology

THFG is an advanced technology to manufacture tubular components with complex cross-sections. Meanwhile, curved axis often exists in such components, which is formed by pre-bending steps before THFG. However, the effect of pre-bending on the subsequent THFG, especially on the critical internal pressure required to inhibit wrinkling, has not been clarified yet. Considering the difference in the cold work-hardening and the thickness distribution caused by pre-bending, the change rule between the critical internal pressure and the hoop strain was re-established based on the energy method. It is found that the cold work-hardening has a great influence on the change rule. Subsequently, by solving the three-dimensional mechanics condition of single and double curvature differential segments respectively, the distribution of hoop strain after THFG was obtained by combining pre-bending. Pointing out that the initial thickness has an obvious effect on the hoop strain distribution, while the cold work-hardening is almost negligible. The maximum hoop strain was brought into the change rule between critical internal pressure and hoop strain, then, a new analytical model between the critical internal pressure and the punch stroke considering pre-bending was built. The critical internal pressure considering pre-bending is determined by that of outer straight wall, and its value is always greater than the critical internal pressure without considering pre-bending under the same punch stroke. With the reduction of bending radius, the critical internal pressure distinction between considering and not considering pre-bending will be greater. Moreover, the smaller the friction coefficient also will lead the distinction to be more prominent. In this work, our proposed new prediction model of critical internal pressure is meticulously demonstrated, which can improve the accuracy by 74% at least when existing the pre-bending.

Full-Field Displacement Measurement Method of Metal-As-Insulation Pancake at Liquid Nitrogen Temperature

In situ measurement of metal-as-insulation (MI) high temperature superconductor (HTS) pancake deformation gives insight to its actual mechanical state. Measurement of hoop strain for inner / outer turn of MI pancake is usually made by strain gauges. This measurement is however local and faces electromagnetic compatibility (EMC) and thermal issues. Non-contact full-field displacement measurement is an interesting alternative solution. This technique is based on digital image correlation (DIC), which derives the displacement field in specified region of interest (ROI) by correlation between the deformed state image and the reference state image. In this article, we present a novel DIC experiment setup for displacement measurement of MI pancake in cryogenic cooling. The setup is validated by a cooling test of 304 stainless steel disc. Then, it is used for cooling test of MI pancake made of co-wound copper beryllium - 304 stainless steel tapes. Both tests are done at 80 K by conduction cooling using liquid nitrogen. Finally, experimental results are compared to numerical results obtained from an analytical formulation of the mechanical equilibrium using generalized plane strain assumption.

Medial meniscus extrusion and stage are related to the size of spontaneous osteonecrosis of the knee in patients who underwent high tibial osteotomy

PurposeSpontaneous osteonecrosis of the knee (SONK) causes acute atraumatic knee pain, and meniscus tears may be associated with the pathogenesis of SONK. The purpose of this study was to investigate the relationship of the type of meniscus tear and medial meniscus extrusion with SONK on the medial femoral condyle in patients who underwent surgical treatment with high tibial osteotomy due to severe knee pain. MethodsWe enrolled 98 patients with 102 knees who underwent medial opening wedge high tibial osteotomy (OWHTO) under the diagnosis of medial femoral condyle osteonecrosis at our hospital from December 2003 to January 2020. Based on the Koshino classification, cases of SONK were classified as stage 1–4. The relationships of demographic data, X-rays and MRI images, including femorotibial angle (FTA), meniscus tear type, and medial meniscus extrusion (MME), with the stage and volume of SONK were investigated. ResultsNinety-eight patients (29 males and 69 females), with an average age at surgery of 69.2 ± 9.6 years and Body mass index(BMI) of 61.0 ± 17.6 kg/m2. In 102 cases of SONK, 11 knees, 18 knees, 46 knees, and 27 knees were classified as stage 1–4, respectively. The mean SONK volume was 2161.61 µm (range 95.67–7484.68 µm) on preoperative MRI. The preoperative FTA (mean 180.86°, range 172–187°) was not associated with the stage or volume of SONK. Meniscus tears were found in all cases of SONK and consisted of 2 degenerations, 2 horizontal tears, 0 vertical tears, 40 radial tears, 4 complex tears, and 54 medial meniscus posterior root tears (MMPRTs). In addition, 99% (101/102) of knees showed more than 3 mm of meniscus extrusion. Although the meniscus tear type was not associated with SONK stage, there was a high rate of tears that caused disruption of the hoop strain, such as MMPRTs (52.9%) or radial tears (39.2%). MME was significantly related to SONK volume (r = 0.387, p < 0.001). ConclusionAll patients with SONK had coexisting meniscus tears, most menisci had medial extrusion, and a positive correlation was observed between MME and SONK volume.

Investigating the graded-index influence on elastic responses of axisymmetric pressurized and heated thick-walled functionally graded material of cylindrical vessel

This article presents the influence of a graded-index on the elastic responses of an axisymmetric pressurized and heated thick-walled functionally graded material (FGM) cylindrical vessel under plane strain conditions. It is assumed that the inside surface/outside surface of a cylinder is made up of ceramic /metal. The temperature-independent thermo-mechanical parameters of an FGM cylinder are described by using the rule-of-mixture with the function of radius. The profiles of thermo-mechanical material characteristics are assumed to vary continuously and gradually along the thickness direction of a cylinder. The numerical solutions of the thick-walled FGM cylinder governing differential equations are examined by using the non-linear shooting and fourth-order Runge-Kutta approaches. The thermo-elastic solutions of the thick-walled FGM cylinder over the radial direction are computed using Jupiter, Python open-access software, and graphically reported. The analytical solutions (AS) of a ceramic cylinder are compared with numerical solutions (NS) of an FGM cylinder (n = 0) to validate the proposed method. The results reveal that the graded-index n has a higher influence on the profiles of dimensionless hoop stress, dimensionless axial stress, dimensionless radial displacement, hoop strain, radial strain, and thermo-mechanical material properties in the dimensionless radial direction of an FGM cylinder. Nevertheless, the graded-index has an insignificant impact on dimensionless radial stress across the dimensionless radial direction of an FGM cylinder. Based on these findings, it is recommended that graded-index is an important parameter which can be used to regulate the responses of FGM structures under thermal and mechanical loading conditions.

Experimental study on the mechanical properties of corroded RC columns repaired with large rupture strain FRP

This paper presents experimental results of the mechanical properties of corroded reinforced concrete (RC) columns repaired with large rupture strain (LRS) fiber-reinforced polymer (FRP). This work seeks to evaluate the effects of corrosion-induced damage, including concrete cracks and rebar buckling, on the confinement effectiveness of LRS-FRP. A total of sixteen RC columns were corroded to different extents by an electrochemical method and then repaired by wrapping them with FRP. A series of monotonic axial compression tests were conducted on these repaired specimens that were characterized by their corrosion conditions and FRP confinement rigidities. The test results show that LRS-FRP confinement effectively enhanced the mechanical properties of corroded RC columns. However, the existence of corrosion weakened the rebar cross-sections and further damaged the confined inner concrete, significantly influencing the compressive strength and ductility of the repaired RC columns. In addition, rebar buckling was more pronounced at higher corrosion rates, which affected the hoop strain distribution of the FRP and further reduced its confinement effectiveness. The existing ultimate condition models for confined concrete are also validated by the current test results, indicating that satisfied predictions can be made as the corrosion effects on confinement effectiveness are properly considered in these models.

3D modelling of coupled electromagnetic-mechanical responses in REBCO coils involving tape inhomogeneity

Electromagnetic and mechanical properties are crucial components of high-temperature superconducting magnet in high-field applications. In this research, in order to predict the multi-field behaviors of REBCO coils during the ramping process, the coupled electromagnetic-mechanical model is constructed with consideration of the strain and magnetic field dependences of the critical current of coated conductors (CCs). The 3D modelling is used to characterize the longitudinal in-homogenous critical current of a CC, which also allows for handling the coil with local defects. To verify the reliability of the coupled model, a comparison of numerical simulations with experiments for a small REBCO coil is first performed with special attention on the hoop strain evolution during the magnetization process. On this basis, the coupled model is then utilized to study the influences of local critical current non-uniformity defined by a Gaussian statistical distribution. The numerical analysis shows that, the tape inhomogeneity has an obvious impaction on decreasing the critical current of REBCO coil. And in high-field scenario, the calculated critical current of coil is highly reduced when the mutual interaction between electromagnetic and mechanical fields is considered. Afterwards, a detailed comparative study is carried out in studying the screening current effects of REBCO coil with and without taking the tape inhomogeneity into account. Finally, the effects of cooling-down process, co-winding materials and local defects are investigated to understand their role in electromagnetic-mechanical response of high-field REBCO coils.

Numerical modeling of floating geosynthetic-encased stone column–supported embankments with basal reinforcement

The performance of the floating geosynthetic-encased stone column–(GESC)-supported embankments with basal reinforcement was examined using a 3-dimensional (3D) hydro-mechanical coupling finite element model. Comprehensive parametric analyses were performed on the governing factors such as consistency of substratum soil, tensile stiffness of basal reinforcement and encasement, and embankment height. The results indicated that a higher embankment load is transferred to the surrounding soil when a GESC was constructed on a weaker substratum. This causes larger increases in the settlement and lateral displacement of the GESC on the weaker substratum. The tensile strain of the basal reinforcement and hoop strain in the encasement also increases. In addition, high tensile stiffness in basal reinforcement and encasement is necessary to ensure feasible settlement reduction in a floating GESC-supported embankment with basal reinforcement.