Beam Cross Section Research Articles

Insights into Calcium Phosphate Formation Induced by the Dissolution of 45S5 Bioactive Glass.

Although models have been proposed to explain the mechanisms of bioglass (BG) dissolution and subsequent calcium phosphate (CaP) mineralization, open questions remain. The processes in which phase transition occurs in aqueous solutions and their dynamics remain underexplored partly because traditional instruments/techniques do not allow for direct observations at the adequate time and length scales at which such phase transformations occur. For instance, given the crucial role of the silica gel in CaP formation during BG dissolution, uncertainty exists about how such a silica gel forms on the BG surface. In the case of CaP formation driven by BG dissolution, questions can also be added, i.e., how CaP develops into an apatitic-like structure, how many transient phases there are, and, in general, phenomena occurring in the solid-liquid interface during BG dissolution. Several approaches were taken to study CaP mineralization driven by BG dissolution, mainly examining the solid-liquid interface and the BG after-reaction surface. This paper focuses on gaining insight into silica gel formation on the BG's surface during dissolution. Electron microscopy techniques were used, including scanning electron microscopy and focused ion beam cross sections. Other analysis techniques, such as time-of-flight secondary ion mass spectrometry, were utilized. Cross sections of reacted BG-blocks gave essential insights into the BG dissolution, particularly its strong dependency on experimental conditions, and tentative evidence has shown that soluble silica from BG dissolution may not reprecipitate/repolymerize on BG blocks' surface; thus, we wonder where it precipitates. Additionally, complementary analysis techniques determined that CaP, during BG dissolution, transitions from amorphous calcium phosphate to a calcium-deficient nanocrystalline apatitic structure with minimal contents of Si4+ and Na+ ions that may be molecularly part of CaP. The Hench model has been the core guide for BG dissolution and subsequent CaP formation for many years. However, this study shows tentative evidence that contributes to and somewhat differs from it.

Разрушение хрупких балок при антисимметричном четырехточечном изгибе

The nucleation of cracks in structural elements during their service life is due to the degradation of the material or the presence of hidden defects. The structure therefore loses its original load-bearing capacity and fails under significantly lower external loads. As a rule, the fracture of structures due to crack growth occurs under mixed loading. In this paper, an eccentric beam of rectangular cross-section with an edge crack subjected to antisymmetric four-point loading is considered. By changing the position of the crack relative to the center of the beam, it is possible to obtain the entire range of mixed fracture modes: I+II, pure I and pure II modes. Using the finite element method, stress intensity coefficients for modes I and II of failure, as well as T-stresses, were obtained for different geometric parameters of the beam and different loading conditions. The length of the crack, its position relative to the beam center, and the length of the short span were varied. The methods commonly used for calculating T-stresses were analyzed. In the element closest to the crack tip, strong displacement oscillations, not mentioned in the literature, are observed, therefore to determine T-stresses with the highest possible accuracy it is suggested to calculate them from displacements, cutting off the 3-4 nodes closest to the crack tip. Experimental studies of the fracture toughness of ebonite in a mixed mode were carried out. For each type of loading and geometry, 3-5 identical specimens were tested. The tests were carried out under static load until the specimens were completely destroyed. In all experiments, the crack initiation angle and critical load were recorded. Six failure criteria were used to predict both failure direction and critical load: the generalized maximum tangential stress criterion, the extended maximum tangential strain criterion, the generalized strain energy density criterion, the generalized maximum averaged stress criterion, the maximum elastic energy release rate criterion and the generalized maximum elastic energy release rate criterion. The results obtained demonstrate good agreement between the experimental values of critical loads and the numerical calculations. The error in determining the crack initiation angle does not exceed 5%. Considering that the experimental results agree with the predictions of failure criteria for the beam subjected to antisymmetric four-point bend loading, this type of a beam specimen can be used to study mixed-type fracture in the elements manufactured from engineering materials, such as, for example, plexiglass, ebonite, and getinax.

Study of the Impact of Loads on the Deformation of Building Structures using Differential Equations

The paper investigates the influence of different types of loads on the deformation of building structures, particularly beams, using second-order differential equations that allow modeling deformation processes. For this purpose, we considered two beam deflection equations under concentrated and distributed loads. Several experiments were conducted under different geometrical conditions (variable parameters of the beam cross-section, length, and loads). The solutions were studied using graph-analytical methods: constructing a graph of solutions reflecting the system's behaviour, a hodograph allowing tracking of additional nuances of the studied process, and amplitude and phase-frequency characteristics. The influence of conditions on the nature of system behavior is determined. The study's results can be used to optimise design solutions in construction.

Basic properties of solidified organic liquids at a cryogenic temperature for electron microscopic visualization and sample preparation of dispersion systems.

It is challenging to image structures in liquids for electron microscopy (EM); thus, low-temperature imaging has been developed, initially for aqueous systems. Organic liquids (OLs) are widely used as dispersants, although their cryogenic EM (cryo-EM) imaging is less common than that of aqueous systems. This is because the basic properties (e.g., vapor pressure, density, and amorphousness) of OL in the solid state have not been extensively investigated, preventing the determination of whether or not the observed structure is free from artifacts. Herein, I summarized physical data related to the phase change, and the solid density at 77 K and sublimation speed for some OLs were measured independently, to discuss the applicability of OLs for cryo-EM. Among various OL properties, the sublimation temperature, pressure, and rate, and crystallinity are important for cryo-EM. The sublimation-related properties are used to judge whether the OL is stable during storage, observation, and sample preparation such as etching. These properties were calculated, and the calculated sublimation speed matched with that measured by cryo-SEM movie imaging. Crystallinity was estimated using the difference between the extrapolated temperature-dependent liquid density and the solid density of frozen OLs measured in liquid nitrogen. Artifacts observed upon freezing were exemplified by focused ion beam cross-sections of OL-in-water emulsions, and cracks, voids, and wrinkles are found in the OL phase at a large shrinkage ratio. The study findings show that the applicability of OLs largely differs for structural isomers and that appropriate OLs are required for the cryo-EM imaging of nonaqueous systems.

Dependence of the distribution of absorbed electron flux energy in matter on the beam cross section

Dependence of the distribution of absorbed electron flux energy in matter on the beam cross section

Experimental, Numerical and Analytical Evaluation of Load-Bearing Capacity of Cold-Formed S-Beam with Sectional Transverse Strengthening.

The article provides information about strengthening cold-formed thin-walled steel beams made of the sigma profile. An innovative concept for sectional transverse strengthening of thin-walled beams subjected to concentrated forces was investigated. The proposed solution's novelty lies in attaching the sectional transverse strengthening to the beam's cross-section, employing a point crimping technique. This technique requires a specific modification of the cross-section edges, necessitating double-lipped flanges. This strengthening method is innovative, as it has not been previously applied to cold-formed structures. Typically, strengthening is achieved using other cold-formed elements or materials, such as timber, lightweight concrete, or CFRP tapes. The laboratory experimentally validated the proposed method using short- and medium-length beams. The experimental results were then compared with the results of the numerical analyses and the conventional design approach described in EC3. The results demonstrated the feasibility of implementing this type of strengthening, its reliability under load, and the confirmation of an increase in the load-bearing capacity of the experimental samples by 11-24%.

Experimental measurement of transverse spin dynamics in the nonparaxial focal region

Abstract The superposition of complex optical fields in three-dimension is the basis of several non-trivial wave phenomena. Significant among them are the non-uniform (inhomogeneous) polarization distribution and their topological character, leading to the emergence of transverse spin angular momenta spin-momentum locking, and their dynamics. These aspects are experimentally measured in the nonparaxial focal region of a circularly-polarized Gaussian input beam. A dielectric mirror, kept in the focal region, is axially scanned to obtain the phase and polarization variations in the retroreflected output beam using an interferometer and spatially-resolved Stokes parameter measurements. The identification of phase and polarization singularities in the beam cross-section and their behaviour as a function of the mirror position enabled us to map and study the phase-polarization variations in the nonparaxial focal region. The lemon-monstar type polarization patterns surrounding the C-point singularity in the output beam are identified and tracked to study the transverse spin dynamics and spin-momentum locking for the right- and left- circular polarization of the input beam. Direct measurement of the input beam polarization helicity-independent and helicity-dependent aspects of the transverse and longitudinal spin angular momenta in the nonparaxial focal region are the significant findings reported here. The proposed and demonstrated measurement method allows us to investigate the nonparaxial focal region in more detail and has the potential to unravel other intricate optical field effects.

Orbital angular momentum at the tight focus of a circularly polarized Gaussian beam

When tightly focusing a circularly polarized optical vortex, a phenomenon of spin-to-orbit conversion has been known to occur. As a rule, the longitudinal component of the spin angular momentum (SAM) vector is assumed to be converted into the longitudinal component of the orbital angular momentum (OAM) vector. In this work, we show that, due to the focusing, the original longitudinal SAM component, averaged over the beam cross-section, is partly converted to the transverse SAM component. In a similar way, the original longitudinal energy flow is partly converted, upon focusing, to the azimuthal component. Meanwhile, the longitudinal component of the OAM vector, averaged over the entire beam cross-section at the focus, increases exactly by the magnitude of the (canonical) averaged azimuthal orbital energy flow at the focus. We show that, upon focusing, the azimuthal energy flow is formed at the focus due to the fact that a right-handed circularly polarized light wave generates two optical vortices: a transverse left-handed circularly polarized vortex with topological charge 2 and a longitudinal vortex with topological charge 1.

Accuracy verification of protoacoustic measurements in a heterogeneous phantom by an optical hydrophone.

Protoacoustics has emerged as a promising real-time range measurement method for proton therapy. Optical hydrophones (OHs) are considered suitable to detect protoacoustic waves owing to their ultracompact size and high sensitivity. In our previous research, we demonstrated that the time-of-arrival (TOA) measured by an OH showed good agreement with the simulated ground truth in a homogeneous medium. The purpose of the study was to experimentally evaluate the accuracy of the TOA and compression peak pressures detected by the OH. Protoacoustic waves that undergo the typical distortions occurring in the human body were investigated. In such cases, the use of small detectors such as OHs is desirable to minimize the effects of detector size and directivity. A 100-MeV proton pencil beam emitted from a fixed-field alternating gradient accelerator was irradiated onto a homogeneous water phantom and a water phantom with a half- or full-sized silicone plate downstream of the Bragg peak (BP) or a bone plate that covered half of the beam cross-section in the beam path. The OH was shifted 70mm laterally across the beam axis downstream of the BP to measure the protoacoustic waves. The k-WAVE acoustic wave transport simulation was employed as the ground truth. The TOA and the first compression peak pressures were compared between the simulation and experiment. The TOA deviation against the ground truth was primarily attributed to alignment errors of the measurement devices and phantoms, with deviations of<1mm. The peak pressure distribution closely resembled the ground truth, with FWHM differences of 0.0%-3.0% for the tested geometries. The OH was able to determine the TOA and peak pressures with sufficient accuracy in heterogeneous phantoms, even without considering the effect of the size of the detector or directivity on the measurements.

Optimum design of reinforced concrete beam sections with JAYA algorithm

Section design is an important process for designing reinforced concrete structures because of the existence of factors such as bearing capacity and cost. After defining the initial cross sections for reinforced concrete elements, reinforcement amounts are calculated within the framework of certain rules and regulations. In the classical method, optimum cost and reliable structure can be designed by trial and error. Designing with the classical method is quite time-consuming. As in different fields, metaheuristic algorithms are employed to civil engineering applications to reach the optimum solution. In this study, unlike other examples from the literature, the optimum cost design of reinforced concrete beam cross-section was done, adding torsional moment to bending moment and effects of shearing force through the use of the JAYA algorithm. The optimum cost design of a reinforced concrete beam section under the effects of torsional moment, bending moment and shear force is performed. The design is done according to the rules specified in ACI 318 (Building code requirements for structural concrete), as it is well-known and used in many international projects. For the purpose of this study, cross-sections of 10 different reinforced concrete beam cross-sections were designed under 5 different loads for 2 different concrete classes through MATLAB software, with the aim of finding the optimum beam cross-section. A reinforced concrete beam is designed under different torsional loads and for different concrete classes and it is aimed to find the optimum beam cross-section. It shows the effect of torsional force on reinforced concrete beam cross section and reinforcement by using different torsional loads. It was observed that the algorithm used tends to approach the optimum result, increasing the area of concrete with lower unit cost or reducing the distance between stirrups. It was concluded that Jaya algorithm performs effectively with respect to optimizing reinforced concrete beams. The algorithm used can be applied to different reinforced concrete elements.

Spin-orbit interaction-mediated measurement of surface chirality.

The spin-orbit (σ - l) interaction in a focused-reflected beam of light results in spatially nonuniform polarization in the beam cross section due to the superposition of orthogonal field components and polarization-dependent interface reflection coefficients. Polarization filtering the output beam leads to an interchangeable transformation of l=∓2 charge vortex into two (∓) unit charge vortices, for σ = ±1 circular polarization of the input Gaussian beam. This transformation follows a trajectory, named optical vortex trajectory, that depends on the input beam's σ and hence the l and reflecting surface characteristics. The vortex trajectory is used here to quantify both the sign and the magnitude of the chiral parameter of a quartz crystal. The Jones matrix-based simulation anticipates the chirality-dependent vortex trajectory that matches with experimental measurements.

Study on economic design and construction program of steel-hybrid combined girder bridge

In order to make full use of steel tensile and concrete compressive properties, combined beam cross-section stress-strain distribution characteristics and cross-section characteristics and loading procedures are closely related. At present, the cross-section form of I-beam combined with concrete panel is widely used, and the strength of the upper flange of the steel beam of the supported combined beam and the strength of the concrete panel of the unsupported combined beam have not been fully utilized. Through the theoretical analysis of different loading methods of combined beam strain stress distribution, so as to optimize the cross-section form, the proposed supported combined beam using the lower inverted T-shaped cross-section combined with the form of concrete panels, in the given actual engineering cases can obtain a higher elastic ultimate bearing capacity and can save 9.5% of the amount of steel. The unsupported loading method of I-beam combination beams can use lower grade concrete for better economy. Making full use of the neutral axis position change to design the combined beam cross-section is operable, inverted T-shaped steel beams combined with concrete panel combined beams is a way to save steel and reduce the construction of welded joints, with significant economic benefits.

Comparison between simplified and refined models for deflection in continuous reinforced concrete T-beams

Verification of the Serviceability Limit State for allowable displacements is a mandatory step in the design of a reinforced concrete (RC) beam. In order to proceed this verification, simplified methods recommended by Design Codes or analytical models can be employed. In these models, the variation in flexural stiffness due to the concrete cracking is the primary factor to be considered. A “T” cross-section beam present greater stiffness compared to a rectangular section of equal height and area. The concentration of more area at one end of the section raises questions about whether this type of section exhibits the same behavioral response as the rectangular section when applying the models for predicting deflection as indicated by Codes. In this work, a comparative study of different simplified methods and finite element (FE) models used for calculating deflections in reinforced concrete T-beams is performed. Simplified methods employed are the one recommended by Brazilian Code ABNT NBR 6118, and the Bilinear method recommended by the fib Model Code. Two FE models are adopted, in which the material nonlinearities are considered by means of moment-curvature diagrams, these based on the simplified methods. The deflections obtained by the different models are compared for several examples of continuous RC T-beams at service, by varying the beam geometry and the reinforcing ratio. The results are analyzed for short-term deflections and long-term deflections. In the end of this work, differences between the models are pointed and recommendations regarding the use of then are drawn for this specific section type.

Study on the Beam Section and Joint Configuration of Payload Frame of Special Vehicle

Abstract With the increasing demand for series of special equipment, light-weight and high-payload capacity along with high mobility have become the major trends in the development of the new generation of special vehicles. The key to achieving high-payload capacity in thin-walled special vehicles lies in the successful application of annular frame beams. This paper focuses on the structural forms of typical annular frames of thin-walled special vehicle, with a particular emphasis on the study of beam cross-sections and beam joint configurations. By applying the Optistruct shape optimization method, improvements to configuration parameters were made to achieve the optimal structural form. A simulation comparison with traditional structural forms was conducted, and the results demonstrate that the new beam cross-section and beam joint configurations can significantly reduce the payload stress level and increase the payload strength while reducing thickness, meeting the high payload characteristic requirements of thin-walled special vehicles.

Size-dependent thermoelastic damping model for vibrating circular cross-sectional micro/nanobeams according to Moore-Gibson-Thompson thermoelasticity theory

Abstract Motivated by the limitations of classical models in capturing the behavior of materials at the micro/nanoscales, this work proposes an analytical formulation for thermoelastic damping (TED) in circular cross-sectional micro/nanobeams with size-dependent mechanics and heat transfer. This model incorporates small-scale effect through the modified couple stress theory (MCST) for mechanics and the Moore-Gibson-Thompson (MGT) model for heat conduction. To accomplish this objective, the initial step involves introducing the general equations of the MCST and MGT model. Following the establishment of the MGT model, the temperature variations throughout the beam are obtained by solving the heat equation. Additionally, by implementing the principles of the MCST, the model incorporates size-dependent constitutive relations. Finally, the research employs the energy dissipation (ED) approach to render a mathematical expression for TED in tiny beams with circular cross section. This relation, expressed as an infinite series, accounts for size-dependent effects by incorporating the MCST and MGT model. In the section dedicated to numerical results, the initial step involves verifying the accuracy of the proposed model through a validation study. Next, the section showcases various numerical results, focusing on how the MCST and MGT model affect the temperature distribution and TED value. The acquired results underscore that the influence of the MCST and MGT model on the amount of TED in small-sized circular cross-sectional beams cannot be disregarded.

Experimental studies of the strength of reinforced concrete beams with a restored protective layer

The article presents the results of experimental studies to assess the strength of reinforced concrete beams with varying degrees of destruction of the protective layer of the working longitudinal reinforcement, followed by its restoration with a repair mixture. The test results of three series of prototypes, three samples in each series, are presented. Within the series, prototypes were made with the same longitudinal reinforcement, and the samples in each series differed in the degree of destruction of the protective layer of the longitudinal working reinforcement in the transverse bending zone. The samples were tested as freely supported beams loaded in the span by two identical concentrated forces. The results obtained made it possible to evaluate the role of longitudinal reinforcement, depending on the degree of destruction of its protective layer, in ensuring strength, forming a stress-strain state and the nature of destruction of reinforced concrete beams of rectangular cross-section in transverse bending zones.

Influence of electron radiation of spring barley seeds on phytopathogenic microflora

Under the conditions of a model pot experiment, the effect of electron irradiation on the phytopathogenic microflora of plant roots and leaves was studied. The studies were carried out on spring barley seeds of the Vladimir variety (reproduction 1), affected by helminthosporiosis (pathogen Bipolaris sorokiniana Shoem.), (natural infectious background). This pathogen causes root rot and leaf spot. The grain was irradiated using a wide-aperture electron accelerator “Duet” with a mesh plasma cathode and the output of the generated beam of a large cross-section into the atmosphere in doses of 1, 2, 3, 4 and 5 kGy. The total administered dose was increased by changing the number of pulses. The radiation dose rate was 100 Gy/pulse, the electron energy was 130 keV (mode 1) and 160 keV (mode 2). The depth of dose absorption did not exceed 300 μm. Based on the conducted studies on the effect of electron irradiation on root rot (pathogen Bipolaris sorokiniana) of spring barley, it was noted that in the tillering and heading phases, when irradiating seed material with a dose of 2 kGy in mode 1 (130 keV), the disease incidence and prevalence decreased by more than 1.5 times compared to the non-irradiated control. In the phase of full grain maturity, the highest value of root infestation (45–50%) and prevalence (95–100%) of Bipolaris sorokiniana were recorded, but statistically significant differences between the irradiated variants and the control were absent. The records of the damage of vegetative plants showed that in the tillering phase, for all irradiation variants in mode 1, the degree of damage to leaves 1–3 increased by 23% compared to the control, and in the heading phase, the degree of damage to the upper leaves (1–3) exceeded the control when irradiated at doses of 2–5 kGy (mode 1) and 1–5 kGy (mode 2) – 2.1–2.8 times for 1 leaf, 1.9–2.0 times for 2 leaves and 1.2 times for 3 leaves.

Neuroanatomy of the vertebrobasilar perforators: implications for aneurysm treatment.

The anatomy of vertebrobasilar perforators has been widely studied in human cadavers, with most reports found in the neurosurgical literature. These arterial perforators are extremely hard to visualize consistently with traditional two-dimensional digital subtraction angiography, but are reliably visible with cross sectional cone beam CT techniques. A clear understanding of this specific neurovascular anatomy and pathology is essential for informed treatment decisions. This review analyzes the anatomy of vertebrobasilar perforators with a focus on practical implications for aneurysm treatment, particularly flow diversion.

Enhancing fire performance of glulam beams through thermal treatment, inorganic impregnation, and densification techniques

The present research investigates a novel, environmentally benign modification method for improving the fire performance of Chinese fir that grows quickly and at low density. This wood is known for its susceptibility to burning and rapid loss of load-bearing capacity in fires. After thermal treatment, inorganic impregnation, and densification, Chinese fir was utilized as the fire-exposure surface for glulam beams. Three sides of full-size members were subjected to fire tests lasting 60 and 90 minutes. Considering the gluelines' thermal conductivity, the improved glulam beams' fire performance was thoroughly evaluated using the finite element program ABAQUS. The study found that the composite modification approach enhanced the weight percentage and mass density of the wood laminates by 32.53 % and 67.87 %, respectively. After 60 min of fire exposure, the charring rates on the exposed surface of the members with the modified laminates were 13.5 % and 27.8 % lower than those of standard glulam beams, indicating a considerable improvement in fire resistance. Greater post-fire residual cross-sectional area and improved fire resistance performance were correlated with an increase in the quantity of modified laminates. The composite modified glulam beams showed a noticeable temperature gradient, which was explained by higher density and specific heat capacity and consequently improved overall fire resistance, according to finite element analysis. The corner effect on the glulam beam cross-section became more evident with prolonged heating, while the gluelines had minimal impact on overall heat transfer.

A quantitative classification criterion for beam-to-column rigid connections in steel braced frames

As the key part of the force-transfer path in a steel frame, a reasonable modeling method of beam-to-column connections in the structural analysis model is crucial. From the designer’s perspective, a rational and accurate classification of beam-to-column connections is an invaluable basis for improving modeling efficiency and design accuracy. Although some investigations led by Eurocode 3 (EC3) have provided a systematic and quantitative approach for classifying beam-to-column connections, it is not sufficiently developed for general steel braced frames. In this paper, based on a modified analytical model of the beam-to-column connection substructure that accounts for the effect of braces, the rotational stiffness demand of the beam-to-column rigid connection is derived from the perspectives of structural lateral stiffness and stability. The quantitative relationship is established between the rotational stiffness demand and the relative stiffness of the braces. The accuracy and reasonability of the proposed analytical model and stiffness demand are verified using finite element models (FEMs) at both the story and structure levels. Particularly, the effect of the non-linear behavior of beam-to-column connections on the structural response under high-intensity earthquakes is further comparatively analyzed in the context of seismic design. The results demonstrate that, a beam-to-column connection can be modeled as a continuous rigid connection in non-linear analysis only if it simultaneously satisfies the following requirements: the rotational stiffness meets the demand proposed in this study, and the bending capacity is designed to be overstrength compared to the beam cross-section.