Major Stress Components Research Articles

Effect of bidirectional load on seismic performance of jacketed external diaphragm joints of high-strength concrete-filled high-strength steel tube frame

As one of the solutions for promoting green building and building industrialization, the application of high-strength concrete-filled high-strength steel tube (HCFHST) can further improve the structural performance of concrete-filled square steel tube (CFST). The beam-column joints, being a major stress component of the frame structure, influence the overall structure's performance during earthquake activity. In the external diaphragm joint of the frame, the stiffness of the steel tube at the connection between the external diaphragm and the CFST column is insufficient; aiming for this, a new type of jacketed external diaphragm joint (JED joint) connected between HCFHST column and steel beam were proposed in this paper. The ABAQUS was used to establish an analysis model to simulate the seismic performance of the joint accurately, and 5 kinds of bidirectional load conditions corresponding to the actual seismic action were designed to carry out numerical simulation for the evaluation of the seismic behavior of the joints of 17 specimens (4 groups), revealing the influence law of bidirectional load and providing design suggestions. The results showed that the hysteresis curve of the JED joint was full, the ductility coefficient was between 2.41 and 4.11, the equivalent viscous damping coefficient was between 0.48 and 0.6, and the deformation and energy consumption capacity in the joint domain reached the ductility requirements specified in GB 50011 and FEMA-350. According to AISC-LRFD and EC3, JED joints were determined to be semi-rigid. The seismic performance of the JED joint under bidirectional load was superior to that under unidirectional load. For the seismic performance of space joints, the most unfavorable load angle joint is characterized by bidirectional synchronous seismic action in the direction of 45°, edge joints are characterized by bidirectional asynchronous seismic action, and middle joints are manifested as constant load and unidirectional seismic joint action.

Study on stress-based fatigue monitoring methodology for Class 1 nuclear pipe based on the RCC-M code

On-line fatigue monitoring technology plays a key role in the LTO of nuclear power plants, for which the main challenges are: how to gain the thermal shock stress quickly and reliably, how to order the random stress history, and how to do the code-coforming fatigue assessment (eg. the RCC-M Code and ASME Code). Compared to the calculation process of FEM, the numerical technique based on the Green’s function is efficient and reliable. The stress due to a linear radial temperature distribution which was previously classified as a secondary stress is re-classified as a peak stress in the ASME Code while this requirement is not supported in the mainstream FEM software (such as ANSYS and ABAQUS). Traditionally, detection of peaks and valleys in the stress history is simply based on the change on sign of the slope of the major stress component (1-D rain flow) which is not strict compliance with the requirement in the codes. Therefore, a refined strategy for detecting peaks and valleys needs to be developed. In this paper, the Green’s function is used to calculate the thermal shock stress for the TECMAN on-line fatigue monitoring software which is developed by the author's team, and the method to separate the stress due to the linear radial temperature distribution and the 3-D rain flow technology for the random stress history with a multiaxial stress state are discussed. In the study case of a prototypical nozzle under rapid thermal shock, the results show that the simple integration method of the Green's function gives identical results as the conventional FEM, and the maximum axial stress caused by the radial linear temperature distribution under the reference transient accounts for 7.03% of the design specification limit 3Sm. Compared to the design requirements in the ASME Code, the criteria in the RCC-M Code is unnecessarily conservative. When the extreme values of the stress components are obtained almost at the same time, the nonconservative for the 1-D rain flow is limited, while the nonconservative cannot be negligible under a multiaxial stress state.

Effects of transpression on the rocks exposed at the Jhelum Fault Zone in the east of Potwar Basin, Pakistan: implications on the subsurface deformation pattern

Jhelum Fault is the north–south-oriented major structural lineament originating from the Hazara-Kashmir Syntaxis and extending southwards towards the Mangla Lake. Geographic extent, nature and significance of Jhelum Fault are the subjects which have been approached by different researchers in the past. The previous research provides enough evidence for the presence of Jhelum Fault as well as they discourse its surface extent. None of the previous research addresses the subsurface model of this fault; consequently, its surface extent has been ambiguous and variably reported. The current research takes into account both the surface lineament as well as the subsurface behaviour of the deformed strata to draft the most reasonable depiction of this fault. Field data were coupled with satellite image of 1.5 m ground resolution to produce the geological map of the study area at 1:25,000 scale. The subsurface model was created along four traverse lines by considering the lateral extent of the structures and their shifting trends on the geological map. The stratigraphic package was taken from the nearby hydrocarbon exploratory well data (Missakeswal-01 well of OGDCL) as no rocks older than middle to late Miocene were exposed in the area. The consistent through-going map extents of many faults in the study area prove that faults are playing the major role in the tectonic evolution of the Jhelum Fault Zone. In the subsurface model, the same faults show very little stratigraphic throw, which signify the major stress component to be associated more with wrenching than pure compression. Therefore, most faults in the area are of transpressional nature having dominant lateral component with relatively smaller push towards west on steeply east dipping faults. The model also shows the positive flower structure with dominantly west verging fault system with few east verging back thrusts. The subsurface proposed model shows that the Jhelum Fault is extendible southwards to the Mangla Lake in the subsurface; however, it acts like a continuous shear zone on the surface where there all the shearing is accommodated by tight refolded fold axes. The east–west shortening does not exceed 14.5% which shows smaller compression in the study area. The 3D model further clarifies the model by showing the consistency of the fault system along strike.

Size-dependency of the transverse-tensile failure behavior for triaxially braided composites

Coupon specimens of triaxially braided composites suffer significant out-of-plane tension–torsion coupled deformation along the free edges, known as free-edge effect, under uniaxial tensile/compressive loading. The presence of free-edge effect causes variations in the measured stiffness and strength properties with specimen size. In this study, the size-dependent failure behavior of a single-layer triaxially braided composite under transverse tension load is investigated. Experiments are conducted to characterize the stress–strain response and failure pattern of straight-sided coupon specimens with various widths. Digital image correlation is used to monitor the free-edge-effect–induced tension-torsion coupled deformation. An improved meso-scale finite element model is developed to enable simulation of fiber bundle pull-out failure by introducing a fully covered tow-to-tow interface and plastic failure of the pure matrix zone. The model captures the size-dependent stress–strain response, free-edge effect induced premature failure and ultimate failure phenomena of the braided composite. The experimental and numerical results identify the transition of the failure mechanism from one that is dominated by fiber bundle pull-out to one that is dominated by fiber bundle shear as the specimen width is increased. The numerical simulation results reveal the correlation of free-edge effect with the progressive failure behavior, and they aid in identifying the major stress components that are contributing to the failure. The conclusions provide useful insights for the structural design and architecture optimization of triaxially braided composites.

Seismic design and elastic-plastic analysis of the hengda group super high-rise office buildings

The Hengda Group super high-rise building in Jinan City uses the frame-core tube structural system. With a height of 238.3 m, it is above the B-level height limit of 150 m for buildings within 7-magnitude seismic fortification zones. Therefore, it is necessary to apply performance-based seismic design to this super high-rise building. In this study, response spectrum analysis and comparative analysis of the structure are conducted using two software applications. Moreover, elastic time-history analysis, seismic analysis under an intermediate earthquake, and elastic–plastic time-history analysis under rare earthquakes are performed. Based on the analysis results, corresponding strengthening measures are implemented at weaker structural locations, such as corners, wall ends connected to framed girders, and coupling beams connected to framed girders. The failure mode and failure zone of major stress components of the structure under rare earthquakes are analysed. The conclusions to this research demonstrate that weaker locations and important parts of the structure satisfy the requirements for elastic–plastic deformation in the event of rare earthquakes.

An experimental study on the structural behaviour of laminated glass members under combined axial compression and in-plane bending

Laminated glass (LG) is increasingly being used as load carrying components in modern buildings thanks to its relatively good safety performance and aesthetic benefits. This paper presents an experimental study into the applicational scenario of structural LG beam-columns subjected to combined axial compression and in-plane bending, such as LG fins supporting glass facade. The investigated LG specimens consisted of annealed float glass plies bonded together by SentryGlas interlayer. A total of 17 tests were carried out, from which the structural behaviour in terms of load carrying capacity, failure mode, post-breakage strength and deformability of the LG beam-columns were investigated in detail. Through the tests, the failure modes and corresponding mechanisms were identified; the influence of axial compression, laminate number and slenderness ratio on the structural behaviour were assessed; and the major stress components resulting in fracture of glass were analyzed. Based on the test and analytical results, a design N–M interaction domain was proposed to facilitate strength checking of LG beam-columns, and recommendations were made to improve the post-breakage performance. The results obtained are expected to provide supplementary information that is currently lacking in existing literature.

Effects of the residual stress, interfacial roughness and scale thickness on the spallation of oxide scale grown on hot rolled steel sheet

Failure at the interface between a steel substrate and oxide scale was investigated by semi-analytical and finite element numerical simulations. Two major stress components along the interface, i.e., tensile normal stress at the peak and shear stress at the inflection point of the idealized undulated interface, were calculated and used for the failure analysis. The mechanical properties of the oxide scale and steel substrate were experimentally measured by the indentation and uniaxial tensile tests, respectively. Growth and thermal residual stresses accumulated at the oxide scale during cooling were calculated by a coupled numerical-analytical method, which was experimentally validated by measuring the residual stresses in the oxide scales with different thicknesses. The finite element simulation of a four-point bending test was conducted in order to reproduce uncoiling process during which spallation of oxide scale may occur. From the analysis of the simulation results, the two major stress components turned out to be amplified by the roughness of the interface and the residual stresses generated by the growth stress of oxide scale and the thermal mismatch between the oxide and steel substrate during cooling. In addition, the shear stress proved to be a significant factor for the spallation behavior. The effect of scale thickness on the spallation was discussed by using the concept of failure map based on interfacial fracture energy.

Spallation analysis of oxide scale on low carbon steel

Failure at the interface between a steel substrate and the oxide scale was analyzed by finite element simulations. Two major stress components along the interface, i.e., tensile normal stress at the peak and shear stress at the inflection point of the undulated interface geometry, were calculated and used for the analysis. The mechanical properties of the oxide scale and steel substrate were experimentally measured by indentation and by uniaxial tensile tests, respectively. The simulations consist of cooling from 1000°C to room temperature to predict residual stresses accumulated during cooling, followed by additional four-point bending to represent the uncoiling process. The two major stress components were amplified by the roughness of the interface and by the residual stress generated by thermal mismatch between the oxide and the steel substrate during cooling. In addition, the shear stress was proved to be a significant factor for the spallation behavior; this fact had not been well recognized in the previous literature. The finite element simulation showed that the severity of the fracture-inducing stress components increases as the oxide thickness and the period of the idealized undulation decrease; the severity also increases as the amplitude of the roughness increases.

Translational control by eIF2α in neurons: Beyond the stress response.

The translation of mRNAs is a tightly controlled process that responds to multiple signaling pathways. In neurons, this control is also exerted locally due to the differential necessity of proteins in axons and dendrites. The phosphorylation of the alpha subunit of the translation initiation factor 2 (eIF2α) is one of the mechanisms of translational control. The phosphorylation of eIF2α has classically been viewed as a stress response, halting translation initiation. However, in the nervous system this type of regulation has been related to other mechanisms besides stress response, such as behavior, memory consolidation and nervous system development. Additionally, neurodegenerative diseases have a major stress component, thus eIF2α phosphorylation plays a preeminent role and its modulation is currently viewed as a new opportunity for therapeutic interventions. This review consolidates current information regarding eIF2α phosphorylation in neurons and its impact in neurodegenerative diseases. © 2016 Wiley Periodicals, Inc.

Spacing of intermediate diaphragms in horizontally curved steel box girder bridges

Horizontally curved box girder bridges inherently exhibit complex torsional and distortional behavior as well as bending due to the initial curvature. Distortional warping and transverse bending normal stresses, two major stress components resulting from distortion, are generally limited to a specific level for efficient use of the cross section by installing adequate intermediate diaphragms. The objectives of the present study are to develop a curved box beam finite element and to propose tentative design charts for adequate maximum spacing of intermediate diaphragms. The validity of the developed box beam element having nine degrees of freedom per node including two distortional degrees of freedom is verified from a series of thorough comparative studies using conventional shell element models. Extensive parametric studies using the box beam elements are performed and the design charts for the maximum spacing of the intermediate diaphragms are presented. Bridges taken into account are single-span, two-span, and three-span continuous horizontally curved box girder bridges. The design parameters considered are the central angle, the number of spans, the span length, the aspect ratio of the box section, the spacing of the intermediate diaphragms, and the desired ratio of the distortional warping normal stress to the bending normal stress. Unlike the current practice where the ratio of the distortional warping normal stress to the bending stress is fixed to a specific value, the proposed design charts facilitate the determination of the maximum spacing of intermediate diaphragm for various desired stress ratios.

A consideration on intermediate diaphragm spacing in steel box girder bridges with a doubly symmetric section

Diaphragms in box girder bridges are implemented primarily to prevent premature excessive distortional deformation under torsional loading condition. Distortional warping and transverse bending stresses, which are the major stress components resulting from distortion, should be appropriately limited to a specific level for efficient use of the cross-section by installing adequate intermediate diaphragms. The objectives of the present study are to develop a thin-walled box beam finite element and to propose tentative design charts for adequate spacing of intermediate diaphragms. The developed beam element possesses nine degrees of freedom per node and the validity was intensively verified from a series of comparative studies using a conventional shell element. Also, performed herein are extensive parametric studies for continuous box girder bridges of doubly symmetric steel box section. The design parameters taken into account were the desired ratio of the distortional warping normal stress to the bending normal stress, the number of spans, the span length, the aspect ratio of the box section, and the spacing of the intermediate diaphragms. The results were summarized into tentative design charts indicating efficient spacing of intermediate diaphragms for the various stress ratios.

Ice-dynamic conditions of Shirase Glacier, Antarctica, inferred from ERS SAR interferometry

AbstractThe surface velocity field of Shirase Glacier, a fast-flowing East Antarctic outlet glacier, is determined from ERS synthetic aperture radar (SAR) images by means of speckle tracking using phase correlation, a technique which matches small image kernels of two complex SAR images by maximization of the local coherence. Velocity estimates are used to calculate surface strain rates, which are then used to calculate the large-scale, vertically integrated force balance and to determine the major stress components resisting the driving stress. For the whole glacier system, the driving stress is largely balanced by the basal drag, but with contributions from lateral drag up to 15% of the driving stress at the grounding line. Longitudinal stress gradients have only local importance to the balance of forces, limited to an area of a few square kilometers near the grounding line, where they resist the driving stress. In the grounded part of the glacier, >90% of the total ice velocity is due to basal sliding. Comparison with a balance-flux distribution of the Antarctic ice sheet suggests that the glacier in the downstream part of the Shirase drainage basin is close to equilibrium, showing a slight negative imbalance.

ACTH, beta-endorphin, substance P, and corticotrophin releasing hormone in plasma and follicular fluid in hormonally stimulated menstrual cycles for in-vitro fertilization in the human.

Changes in plasma concentrations of ACTH, beta-endorphin (beta-EP) and cortisol have been found to be associated during the human menstrual cycle. Changes in hypothalamic levels of gonadotrophin releasing hormone (GnRH), beta-EP and substance P (SP) have also been associated with the oestrous cycle in the rat. Therefore, an attempt was made to measure the activity of the corticotrophic axis and SP by measuring blood and follicular fluid concentrations of ACTH, beta-EP, SP and corticotrophin releasing hormone (CRH) during the hormonal ovarian stimulation phase for in-vitro fertilization (IVF), in a series of 19 patients. At the plasma level, there was no significant change over treatment days in ACTH (P = 0.1550), beta-EP (P = 0.1137), or SP concentrations (P = 0.5625). CRH was not detectable over treatment days. In addition, there was no significant change in neuropeptide over treatment days between those women who became pregnant and those who did not (P = 0.17 for all). In the follicular fluid, ACTH was not detectable, beta-EP concentration was three times higher than in the plasma, CRH was detectable, and SP concentration was similar to that of plasma. There was no apparent correlation, however, between beta-EP or SP concentrations in the plasma and follicular fluid from a given patient. In conclusion, the absence of changes in the activity of the corticotrophic axis during the hormonal ovarian stimulation suggests that there was no major stress component associated with the stimulation phase of IVF or the occurrence of a pregnancy.

Fissure Characteristics Related to Moisture Adsorption Stresses in Rice

Rice kernels were initially conditioned to three equilibrium relative humidities (ERH) of 46, 62, and 80%, and then exposed to high relative humidity (RH) environments of 65, 86, and 100% for different periods. Kernels were inspected for stress fissures during moisture adsorption. The three major stress components, namely axial, radial, and tangential stresses were studied in relation to failure tensile strength and local strain energy density of distortion using the finite element method. The calculated axial stresses from moisture adsorption were compressive at the surface and tensile at the grain center. The calculated radial stresses in the central section of a grain were always tensile and high at the center and negligibly small at the surface. The behaviors of the tangential stress distributions along the central radius were identical to that of the axial stress along the radius. The calculated stress distributions agreed rather well with stress distributions in a rice kernel as they were hypothesized by Kunze and Choudhury (1972).

Stress transfer in the fibre fragmentation test

The micromechanics of stress transfer has been analysed in a multiple-fibre composite which was subjected to uniaxial tension. The model composite was treated as a three-cylinder assemblage, which consisted of a central fibre, a matrix annulus and a composite medium. Analytical solutions have been derived for all major stress components for the composite with fully bonded fibre-matrix interface. A parametric study was performed on a carbon fibre-epoxy matrix composite. The result suggests that the principal effect of a stiff composite medium surrounding a discontinuous isolated fibre due to the high fibre volume fraction and stiff matrix, is to reduce the efficiency of stress transfer over the central potion of the fibre, while promoting the fibre-matrix interface shear stress concentration at the fibre end region. Practical implications of this observation with respect to fibre fragmentation and interfacial debonding are discussed.

Local effects in plates - theoretical and practical consequences

The term “local effect” denotes local, pronounced, three-dimensional stress states which occur primarily at the boundaries of flat beams and stretched plates made of homogeneous or composite materials, particularly in the regions of notches, cracks, local mechanical and thermal loads, etc., but which may also occur in any other region. These effects are still ignored in common procedures of analytical mechanics and in traditional procedures of experimental stress analysis, despite the fact that they often increase drastically the maximal stress values occurring in critical regions of structures made of homogeneous and composite materials. The most consistent and rapid response to the needs of modern engineering design with respect to local effects has developed within the field of analytical mechanics. The emphasis has been placed on mathematically and physically admissible analytical solutions. The problem is that the developed analytical models and solutions must be tested experimentally and that this task cannot be reliably accomplished by using experimental procedures based on the concept of plane stress state. This paper presents three new analytical/experimental groups of methods developed by the author and his co-workers: isodyne methods, strain gradient methods and thermoelastic methods. The first two methods have been developed to analyze local effects: static and dynamic. The third method was developed to study dynamic strain/stress fields. The presented empirical evidence shows that the isodyne techniques and strain gradient techniques can be used to evaluate major stress components of three-dimensional stress states in plates and beams caused by local effects. This evidence can be used either directly in engineering design, or as a measure to test the predictive power of analytical models and solutions, and in particular, to quantify errors caused by the simplifying assumptions accepted in analytical solutions.