Support Load Research Articles

Equivalent Moment of Inertia Based on Integration of Curvature

This paper evaluates the benefits of computing deflection with an equivalent moment of inertia based on integration of curvature to account for changes in member stiffness along the span. Results are evaluated for steel and fiber-reinforced polymer reinforced (FRP-reinforced) concrete flexural members with different loading arrangements and support conditions. Closed-form solutions of integrated expressions for deflection are expressed in terms of an equivalent moment of inertia Ie′ and compared to deflection computed with an effective moment of inertia Ie based on the stiffness at the critical section. Results from this comparison are validated with measured deflections from an experimental database for FRP-reinforced concrete. Current code-related approaches are also compared to the experimental database. It is shown herein that the use of an integration-based expression for the moment of inertia can lead to improved prediction of deflection, though the use of an effective moment of inertia based on member stiffness at the critical section gives a reasonably conservative estimate of deflection in many cases. The benefits of taking account of changes in stiffness along the member span are more evident when low reinforcing ratios are used in combination with FRP reinforcement, and use of the integration-based expression Ie′ may be warranted when deflection control is critical in such cases.

Perioperative oxygen therapy and oxygen utilization

Tissue hypoxia is a key trigger for organ dysfunction. The maintenance of adequate tissue oxygenation is therefore of particular importance during major surgery. In this review, we discuss the physiological basis and the rationale underlying the recent concepts of perioperative oxygen therapy. Adequate tissue oxygenation is vital for optimal tissue healing in the surgical context. Nevertheless, the definitive proof for a beneficial effect of perioperative oxygen therapy with an increase in inspired oxygen has not been established. In contrast, optimization of oxygen delivery (DO2), using either or both fluid loading and inotropic supports, to prevent tissue hypoxia in relation to an increased oxygen consumption (VO2) could improve outcome. In this context, the use of central venous oxygen saturation (ScvO2), which reflects important changes in the DO2/VO2 relationship and of central venous-to-arterial carbon dioxide difference, to address adequacy of oxygen utilization, has shown promising results. Adequacy of oxygen delivery to tissue oxygen metabolic demand is essential during the perioperative period. The benefit of perioperative oxygen therapy is rather optimizing the DO2 than increasing inspired oxygen. Improving DO2 has been demonstrated in the perioperative period to reduce both morbidity and mortality. Adaptation of DO2 to O2 consumption using specific goals seems promising.

Structure and mechanical properties of low temperature magnetron sputtered nanocrystalline (nc-)Ti(N,C)/amorphous diamond like carbon (a-C:H) coatings

This paper reports on the structure and mechanical properties of ~ 2 μm thick nanocomposite (nc-) Ti(N,C)/amorphous diamond like carbon (a-C:H) coatings deposited on 100Cr6 steel substrates, using low temperature (~ 200 °C) DC reactive magnetron sputtering. The carbon content was varied with acetylene partial pressure in order to obtain single layer coatings with different a-C:H carbon phase fractions. The nanocrystalline Ti(N,C) phase is approximately stoichiometric for all coatings and the a-C:H phase fraction increases from 31 to 47 at.% as the coatings stoichiometry changed from TiC 1.34 N 0.51 to TiC 2.48 N 0.48, respectively. TiC 1.34 N 0.51 coatings showed the highest nanoindentation hardness (H) of ~ 14 GPa and a modulus (E r) of ~ 144 GPa; H reduced to < 6 GPa and E r to < 70 GPa for TiC 2.48 N 0.48 coatings. nc-Ti(N,C)/a-C:H coatings are promising candidates for applications where better matching of the modulus between a relatively low modulus substrate, hard loading support layer and low modulus-high H/E ratio top layer is required.

DEVELOPMENT OF A DECISION SUPPORT SYSTEM FOR SOLVING CONTAINER LOADING PROBLEMS

The globalization of supply chains and rising fuel costs are forcing container carriers both to minimize the number of trips and to maximize available container space. This makes container loading (CL) a critical process especially in real‐life applications. Container loading (CL), which is a difficult problem to be solved, has many applications in container transportation and distribution industries. This article presents a container loading support system (CLSS). The proposed CLSS composes of three main components, including a hybrid Bees Algorithm as the main computational algorithm, the graphical user interface (GUI) and a simulation program. The aim of the designed system is to make the packing pattern more visible to the user in order to simplify the loading process. An illustrative example ‐a CL problem from literature ‐ is also provided to introduce the operation of the system and to prove its efficiency.

Structural quality of soils cultivated with coffee and pasture in an environmental protection area

Studies of soils in Environmental Protection Areas (EPAs) are of great importance, because they are an essential component of ecosystems, directly interfering in environmental sustainability. The objective of this study was to evaluate the structural quality of soil cultivated with coffee and used as pasture in the Capituva's River microbasin, which is located in the Environmental Protection Area in Coqueiral, south of the state of Minas Gerais. Uniaxial compression test (preconsolidation test) and soil resistance to penetration were used. Undisturbed samples were taken from the surface layer (0-5 cm) of the soils in the area: a typic dystrophic Red Latosol (LVd - Oxisol), a typic eutrophic Red Argisol (PVe - Ultisol), and a typic dystrophic Haplic Cambisol (CXbd - Inceptisol). A significant linear positive correlation was observed between the results of the preconsolidation test and soil resistance to penetration. Load bearing capacity of soil could be estimated accordingly by means of penetration resistance for LVd, PVe, and CXbd. Cambisol - CXbd showed lower loading support capacity and resistance to penetration than LVd and PVe, due to the better crop management in this soil that resulted in higher physical quality which accounts for higher production and environmental sustainability.

Fractionized calibration of the sample stage used in an AFM-probe mechanical testing system

Atomic force microscope (AFM) is increasingly used to measure the micro/nanoscale or local mechanical properties of materials and structures. This leads to the calibration and control of its sample's stage to become an important issue, especially for a precise measurement of the displacement load and the deflection of the AFM cantilever beam. In this paper, the temporal speckle pattern interferometry (TSPI) is applied to fractionally calibrate a piezoelectric transducer (PZT)-typed sample stage in our AFM-probe micro/nano mechanical testing system. The calibration includes two parts: one for fractionized calibration of the sample stage which is used to provide the displacement loading and sample support, and the hierarchy displacement calibration with a range from micrometers to several nanometers based on the sequence analysis of the TSPI, the other for calibration of the AFM-probe testing system by which the relationship between the displacement of the sample stage and the deflection of the cantilever beam of the AFM-probe system is obtained. The system's performance is demonstrated by testing the coupling deformations of two microcantilever beam samples and the AFM-probe testing system.

The effects of fluid loading and elastic supports on the transmission of low-frequency noise through a single-pane window

The transmission of low frequency noise (LFN) through a structural element is explored in the current study by coupling the finite element method (FEM) with the boundary element formulation (BEM). The techniques of component mode synthesis are applied to adjust the stiffness matrix in the FEM formulation. The effect of the elastic boundary conditions on the transmission of sound through a rectangular window is then investigated numerically. Parametric studies have been carried out to examine the effects of natural frequencies, fluid loading and dimensions of the elastic structures on the transmission of LFN. The coupled FEM/BEM formulation is particularly useful to study the structural responses due to LFN below 200 Hz because relevant parametric studies can be conducted numerically avoiding the need of performing tedious and expensive experimental measurements. It has been demonstrated in the numerical simulations that the effects of fluid loading and elastic mounting conditions are particularly important for computing the transmission of airborne excitations through elastic windows with frequency below 125 Hz.

Inotropes in goal-directed therapy: Do we need 'goals'?

There is substantial evidence to demonstrate the benefits of goal-directed hemodynamic optimization using fluid loading or inotropic support or both to improve outcome during major surgery. However, until now, only limited pathophysiological data have been available to explain this benefit. The maintenance of adequate tissue perfusion and global oxygen delivery is an essential goal for therapy. In an interesting study, Jhanji and colleagues provided additional data that emphasize the roles of optimization of intravascular fluid status and low doses of inotropes to improve microvascular blood flow and tissue oxygenation. This commentary aims to highlight some issues raised by this important study and provides additional elements to further position these results.

Multicentric retrospective clinical study on the clinical application of mini implant system

Introduction: Mini-implant system is applicable to areas of narrow space and area requiring temporary loading support. The purpose of this st udy was to evaluate the clinical outcome of a mini-implant system as well as the application of mini-implant system in the dental c linical field. Materials and Methods: The patients who had been operated from Jan 2007 to Dec 2007 in the four dental facility including Seoul National University Bundang Hospital were enrolled. To evaluate the factors associated with the clinical outcome, the patients were clas sified according to gen- der, age, area of surgery, type of implant, diameter and length of the implant, and the purpose of the mini-implant system appl ication. Results: From 147 implants, only three implants failed, one of them was for temporary loading. There were no serious surgical or prosthe tic compli- cations in this study. Conclusion: An analysis of the preliminary data revealed a satisfactory clinical outcome. However, more long-term evaluation of narrow ridg e type as well as the patient' s satisfaction on the use of a provisional type mini-implant system is needed.

Role of the residual Na + ions on the dispersion of WO x species on titania nanotubes by in situ thermo-Raman study

Titania nanotubes synthesized by alkali hydrothermal method were used to support 5–20 wt.% of WO x by wet impregnation method. Samples were characterized by in situ thermo-Raman spectroscopy, electronic microscopy and X-ray diffraction. Initially and below 400 °C, WO x species have octahedral coordination as isolated species. After annealing at 500 °C, the nanotubular support collapsed and transformed into anatase. This event released Na + ions that reacted with surface WO x species converting into sub-nanometric sodium tungstate (Na 2WO 4) particles, homogeneously dispersed on the support. At higher temperature, that is at 700 °C and 800 °C, Na 2WO 4 nanoparticles were detected on samples with W content ≤10 wt.%, whereas a mixture of Na 2WO 4 and Na 2W 2 O 7 was obtained on samples with W content above 15 wt.%. A very thin layer of sodium tungstate covered the titania (anatase or rutile, depending on W loading) support after annealing at 800 °C yielding core–shell particles, with titania phase in the core and Na 2WO 4 and/or Na 2W 2O 7 on the shell.

Finite element study of scaffold architecture design and culture conditions for tissue engineering

Tissue engineering scaffolds provide temporary mechanical support for tissue regeneration and transfer global mechanical load to mechanical stimuli to cells through its architecture. In this study the interactions between scaffold pore morphology, mechanical stimuli developed at the cell microscopic level, and culture conditions applied at the macroscopic scale are studied on two regular scaffold structures. Gyroid and hexagonal scaffolds of 55% and 70% porosity were modeled in a finite element analysis and were submitted to an inlet fluid flow or compressive strain. A mechanoregulation theory based on scaffold shear strain and fluid shear stress was applied for determining the influence of each structures on the mechanical stimuli on initial conditions. Results indicate that the distribution of shear stress induced by fluid perfusion is very dependent on pore distribution within the scaffold. Gyroid architectures provide a better accessibility of the fluid than hexagonal structures. Based on the mechanoregulation theory, the differentiation process in these structures was more sensitive to inlet fluid flow than axial strain of the scaffold. This study provides a computational approach to determine the mechanical stimuli at the cellular level when cells are cultured in a bioreactor and to relate mechanical stimuli with cell differentiation.

Repetitive beam-like structures: Distributed loading and intermediate support

Theory is developed for the elastostatic transfer matrix analysis of a repetitive beam-like structure subject to point-wise distributed loading, with and without an intermediate support; this complements previous work in which loading is applied at one end only and reacted at the other. State-vectors are expressed in terms of participation coefficients of the eigen- and principal vectors, leading to the simplest description of the evolution of nodal displacement and force components as one moves along the structure, in terms of powers of the Jordan canonical form. Inaccuracy due to ill-conditioning is explained in terms of powers of greater than unity eigenvalues.

Web buckling of lightsteel beams strengthened with CFRP subjected to end-bearing forces

The web-crippling failure becomes critical at the loading points or supports of beams where concentrated bearing forces are applied. This paper presents the test results on CFRP-stiffened lightsteel beam (LSB) under end-bearing loads. A series of laboratory tests were conducted. Three types of strengthening methods were used; applying CFRP plates on the outer side or inner side or both sides of the web. It was found that the CFRP strengthening significantly increases the web-buckling capacity especially for those with large web depth-to-thickness ratio. Simple models are proposed to predict the improved performance due to CFRP strengthening.

Tribological properties of graded diamond-like carbon films on Ti ion-implanted aluminum substrate

Titanium ions are implanted into the aluminum substrate prior to deposition of the Ti interlayer and DLC graded film produced by magnetron sputtering in order to enhance the structural continuity between the soft substrate and graded DLC film. The Ti-implanted substrate not only strengthens loading support but also improves adhesion with the overlying film. The total thickness of the functionally graded film on the Al substrate reaches over 10 μm and it has a hardness value of ~ 11 GPa. The graphitic network in DLC film helps to reduce the friction coefficient while the graded design disperses the stress during wear and loading.

The effective elastic thickness of the India Plate from receiver function imaging, gravity anomalies and thermomechanical modelling

The range and the meaning of the effective elastic thickness (EET) in continental areas have been subject to controversy over the last two decades. Here we take advantage of the new data set from the Hi-CLIMB seismological experiment to re-estimate the EET of the India Plate along a south–north profile extending from the Ganges basin to central Tibet. Receiver functions give a high-resolution image of the base of the foreland basin at ∼5 km depth and constrain the crustal thickness, which increases northwards from ∼35 km beneath the indo-gangetic plain to ∼70 km in southern Tibet. Together with available data sets including seismic profiles, seismological images from both INDEPTH and HIMNT experiments, deep well measurements and Bouguer anomaly profiles, we interpret this new image with 2-D thermomechanical modelling solutions, using different type of crustal and mantle rheologies. We find that (1) the EET of the India Plate decreases northwards from 60–80 to 20–30 km as it is flexed down beneath Himalaya and Tibet, due to thermal and flexural weakening; (2) the only resistant layer of the India Plate beneath southern Tibet is the upper mantle, which serves as a support for the topographic load and (3) the most abrupt drop in the EET, located around 200 km south of the MFT, is associated with a gradual decoupling between the crust and the mantle. We show that our geometrical constraints do not allow to determine if the upper and lower crust are coupled or not. Our results clearly reveal that a rheology with a weak mantle is unable to explain the geometry of the lithosphere in this region, and they are in favour of a rheology in which the mantle is strong.

Kinetic parameter estimation for supported vanadium oxide catalysts for propane ODH reaction: Effect of loading and support

Kinetic parameters are estimated for a sequential Mars van Krevelan (MVK) reaction model occurring over several supported vanadium oxide (vanadia) catalysts involved in the propane oxidative dehydrogenation (ODH) reaction. The estimated kinetic parameters, pre-exponential factors and activation energies, are used to understand the effect of vanadia loading and oxide support. The pre-exponential factors and vanadia normalized pre-exponential factors vary with vanadia loading and oxide support. The monotonic increase in normalized pre-exponential factors with vanadia loading and the variation of pre-exponential factors with oxide support appears to be related to the change in acidity/basicity of the catalyst and the redox nature of the catalyst, respectively. The activation energy for propene degradation does not significantly change with catalyst; however, the activation energy for propane oxidation is different for the V 2O 5/Al 2O 3 catalyst. It appears that two important considerations are required for the development of an efficient propane ODH catalyst: a high rate constant associated with the propane oxidation reaction, and a high ratio of the rate constant for propene formation to degradation reaction. Based on the observations in the present study it is proposed that a higher TiO 2 support surface area will assist in increasing the propane oxidation activity and propene yield.

Oligosaccharide synthesis on a soluble, hyperbranched polymer support via thioglycoside activation

The synthesis of linear and branched di-, tri- and tetramannosides on a commercially available hyperbranched polyester as a soluble, high loading support is described. Glycosylation products were isolated in 26–63% yield as mixtures of anomers after total hydrolytic degradation of the polymer. All polymer-bound intermediates were purified through simple extraction or precipitation. Solution-phase NMR and MALDI-TOF were used to monitor the progress of the reaction directly on the hyperbranched polymer support.

Graph representation for structural topology optimization using genetic algorithms

This paper proposes a graph representation for evolutionary structural topology design. Based on graph theory, a valid topology in the design domain is represented by a connected simple graph and each edge of the graph is defined by a cubic Bézier curve with varying thickness. The graph is defined to have connecting paths between loading regions and support regions of the structure, to ensure a physically meaningful connected structure. Each path is formed by one or more Bézier curves in order to allow more local control of the shape. A real-valued chromosome encoding and decoding scheme and a partition crossover method are also developed based on graph theory. The graph representation GA is applied to structural topology optimization problems and its performance is compared with those of other methods. Compared with the power-law approach, the present graph representation GA can generate clearly defined and distinct geometries and perform a global search, but it requires more computational cost. The numerical results also demonstrate the improved performance of the present graph representation over that of the Voronoi-bar representation in terms of connectivity of the geometry and convergence speed. It is suggested that this graph representation method is both physically meaningful and computationally effective in the framework of topological optimum design using GAs.

Probabilistic Estimation of the Fatigue Life of an Electric Car Bogie Frame

Bogie frames of electric cars play an important role as a structural member for the support of vehicle loading. To guarantee more than 25 years' durability, a lot of study has been carried out for the prediction of the fatigue life of the bogie frame in experimental and theoretical domains. One of the new methods being applied in recent years for rolling stock structures is a reliability-based approach. In this paper, using one of these methods, we estimate fatigue life of the bogie frame of an electric car, which was developed by the Korea Railroad Research Institute. First of all, we have carried out tensile fatigue tests with several types of specimens: as-welded, ground on weld toe, reinforcement-removed and post weld heat treated specimens for each type aforementioned. In addition, we perform the probabilistic distribution tests of the S-N curves for the ground specimens. Normal, lognormal and Weibull distributions are used to model the distributions. Along with the obtained S-N relations, we use two approaches to evaluate the fatigue life of the bogie frame. In the first approach probabilistic distribution of the S-N curve is used. The S-N curves are obtained in function of failure percent from the specimen tests. Then the fatigue life is estimated by use of Miner-Palmgren hypothesis. In the second approach, load spectra measured by strain gauges are approximated by a two variable Weibull distribution. And a limit state function for the criterion of failure is derived by use of Miner-Palmgren hypothesis. The fatigue life is evaluated by a reliability engineering method.

On the application of beam-column interaction formulae to steel members with arbitrary loading and support conditions

An investigation on dealing with the application of the so-called Level 1 and Level 2 beam-column interaction formulae to isolated steel members with arbitrary loading and end support conditions is reported. The issues addressed concern mostly the importance, both in terms of safety and accuracy, of adopting appropriate “equivalent moment factor” (Cm) values. Only the in-plane behavior of members subjected to axial compression and major or minor axis bending is investigated, but several load combinations and support conditions are dealt with. The strength estimates provided by the Level 1 and Level 2 interaction formulae are presented, discussed and compared with “exact” values, obtained from second-order plastic zone analyses performed by means of the FEM code, ABAQUS. On the basis of such comparative studies, several conclusions are drawn concerning the safety and accuracy of the strength estimates yielded by the two interaction formulae and, in particular, it is shown that significant improvements can be achieved by adopting “exact” Cm values. Moreover, some attention is paid to issues related to the proper choice or determination of these “exact” Cm values.