Area Of Beams Research Articles

Implementation of problem based learning model assisted by powerpoint and space building props on the surface area of cubes and beams in fourth grade students SDN Teluk Pucung I

One of the efforts to overcome students' low understanding of the material surface area of cubes and blocks is through the application of innovative learning models. The research aims to improve students' understanding of the material of the surface area of cubes and blocks through Problem Based Learning models assisted by powerpoint media and props for building cubes and blocks. The study used the collaborative classroom action research model of Kemmis Mc Taggart. The participants of the study were 16 students consisting of 10 female students and 6 male students in grade VI SDN Teluk Pucung I. Researchers collected data through observation, interview, and test techniques. Observation and interview techniques are useful for obtaining data on the implementation of research. Meanwhile, test techniques are used to measure students' understanding in the form of description questions. Researchers analyze data through three stages, namely reducing data, presenting data, and drawing conclusions. The data that has been analyzed is then validated through triangulation techniques. Research findings show an improvement in reading skills in each cycle. Referring to the research findings, the researcher concluded that the application of the Problem Based Learning model assisted by powerpoint media and teaching aids for building cubes and blocks can increase students' understanding of the material surface area of cubes and blocks

Experimental and numerical investigation of the hysteretic behavior of reinforced concrete column-steel beam interior joints under low seismic intensity levels

For the composite frame structure of concrete column and steel beam, a connection structure based on ribbed angle steel connector (RASC) is proposed, and the hysteresis performance and force transmission mechanism of this new type of composite joint are studied. Through quasi-static experimental research, the influence of beam and column cross-sectional dimensions on the bearing capacity, energy dissipation capacity, stiffness degradation, ductility, and failure form of the frame structure was analyzed. The results of experimental and finite element analysis show that the failure forms of this joint under low-cycle repeated loading are mainly manifested as the shear failure of concrete in the core area of beams and columns and sliding failure between angle steel connectors and steel beams, and the hysteresis curves of the joints are similar to those of frame beams and columns, respectively.

Power amplification in the core area of radial carpet beams

We investigate the power redistribution in radial carpet beams (RCBs). We show that RCBs have increased power in the core area, which surrounds the central patternless area, as they propagate. We present both theoretical and experimental evidence that RCBs self-amplify in the core area due to their radial expansion. We examine the power carried by a main intensity spot of different RCBs produced by the diffraction of a plane wave from amplitude/phase radial gratings with sinusoidal/binary transmission profiles. We find that the core area, which has a complex intensity distribution, increases in power as the beam propagates. This feature distinguishes RCBs from other beams and makes them self-amplifying-like beams. Thus, the power amplification in RCBs is an internal effect caused by the continuous transfer of power from the patternless area to the core area. The power transfer to the core area also improves the stability of the beam in turbulent environments such as the atmosphere, making it a promising candidate for atmospheric optical communication. We discuss the practical realization of RCBs with a finite-radius beam and a radial grating. We define a “power amplification length” as the propagation distance at which the outer radius of the core area of the beam equals the beam radii at the grating. For instance, for the beam radii of 5 and 50 cm at the grating with 20 spokes, the values of these distances are 230 m and 23 km, respectively.

MENINGKATKAN HASIL BELAJAR MATEMATIKA MELALUI PEMBELAJARAN KOOPERATIF TIPE SCRAMBLE DENGAN PENDEKATAN CTL

The purpose of this study was to improve students' mathematics learning outcomes through Scramble Type Cooperative Learning Model with Contextual Teaching and Learning (CTL) approach in class VIII SMP Negeri 2 Latambaga. The research method used was Classroom Action Research. The results showed that by looking at the results of the second cycle test, the average student score was 85.23 with classical learning completeness of 87.5%. When compared to the first cycle test results with an average student score of 79.96 and classical learning completeness of 78.12%, there was an increase in the average score of 5.74 and learning completeness of 9.38%. After seeing the test results, the results of observations of students and teachers during the teaching and learning process, it was concluded that this research was stopped in cycle II. This is because the success indicator of this research has been achieved, namely classical learning completeness has been more than 80% of students obtained a score ≥ 68 (KKM that has been determined), namely 87.5% of students have obtained a score ≥ 68. So it can be concluded that the implementation of the Scramble Type Cooperative learning model with the Contextual Teaching and Learning Approach can improve student learning outcomes in mathematics subjects, especially in the basic competencies of calculating the surface area and volume of cubes and beams of class VIII students of SMP Negeri 2 Latambaga.

Study on mechanical properties of poplar timber bending members of ancient buildings strengthened with CFRP sheets embedded

The reduction of the section area of timber beams in ancient buildings leads to the decline of their flexural mechanical properties. In order to study the effect of the reinforcement method with near-surface mounted CFRP sheets, three groups of 14 scaled poplar timber beam specimens were designed for static loading tests, and the strengthening effects of the new members replacing the damaged members and the concealed CFRP sheets strengthening the damaged members were compared. The results show that the ultimate flexural capacity and flexural stiffness of the strengthened timber beams are significantly improved compared with the simulated damaged beams; the bending performance of the optimum strengthened timber beam is equivalent to that of the undamaged beam. The distribution of the section strain of the strengthened timber beam along the height of the beam section basically conforms to the plane section assumption. A formula for calculating the ultimate flexural capacity of poplar timber beams strengthened with CFRP sheets is proposed. The calculated results are in good agreement with the experimental results.

Stochastic FE analysis of stress concentrations in curved glulam beams due to the uncertainty of material direction

When curved glulam beams are subjected to bending, tension perpendicular to grain is introduced. In this work, Monte-Carlo analysis is conducted to study the influence of the annual-ring orientation of individual board on stress concentration in the radial direction. A virtual cutting program is developed which simulates the sawing processes of boards and yields a database of sawn boards, each with a characterized material direction with respect to the pith location. Lamellas are randomly selected from the database to construct curved glulam beams in FE models for Monte-Carlo simulation. Parameters including lumber diameter distribution, taper function, orthotropic elastic properties are considered for four common wood genera in Europe: spruce, pine, larch, and beech.Statistical analysis shows that when the annual-ring effect is considered, the average radial stress in the middle height area of the glulam beams can reach up 1.56 times (even higher on the middle width and height area) compared to the common practice, where wood is usually simplified as transverse isotropic material. Such stress concentration, which can trigger early damage of the structure, indicates an underestimation of stress perpendicular to grain in common practice. Moreover, parameter studies show that the stress redistribution depends not only on the mechanical properties of wood species but also on the width of the board layer.

Gaussian beam diffraction from radial structures: detailed study on the diffraction from sinusoidal amplitude radial gratings.

In this work, we report a comprehensive theoretical investigation on the diffraction of a Gaussian beam from structured radial apertures. In particular, the study of near- and far-field diffraction of a Gaussian beam from an amplitude radial grating having a sinusoidal profile provides new theoretical insights and possible applications. We observe a high self-healing feature at far-field for the Gaussian beam in the diffraction from amplitude radial structures. It is also shown that by increasing the spokes number of the grating, the strength of the self-healing decreases, and reforming of the diffracted pattern into a Gaussian beam occurs at longer propagation distances. The energy flow towards the central lobe of the diffraction pattern and its dependence on the propagation distance are also investigated. In the near-field regime, the diffraction pattern is very similar to the intensity distribution in the central area of the radial carpet beams generated in the diffraction of a plane wave from the same grating. It is shown that by optimally choosing the waist radius of the Gaussian beam, in the near-field regime, it is possible to have a petal-like diffraction pattern, which has been experimentally used in multiple-particle trapping. Compared to radial carpet beams, since in this case there is no energy in the geometric shadow of the radial spokes of the grating, the main part of the power of the incident Gaussian beam is transferred to the main intensity spots of the petal-like pattern, which significantly increases the multi-particle trapping efficiency. We also show that regardless of the grating spokes number, at the far field, the diffraction pattern becomes a Gaussian beam, and its power share reaches 2/3 of the total power passed through the grating.

Effects of a single introduction of pamidronate on intact bone under the conditions of the experimental model of the treatment of tuberculosis ostitis

BACKGROUND: Information about the features of intact bone tissue of the contralateral segment in the treatment of tuberculous osteitis is absent in the literature.
 AIM: Study of the features of intact bone tissue in the conditions of complex treatment of experimental tuberculous osteitis.
 MATERIALS AND METHODS: On an experimental model of tuberculous osteitis of the condyle of the right femur (Mycobacterium tuberculosis H37Rv) in 21 rabbits, the morphometric characteristics of the contralateral femurs, representatively selected from 4 groups, were studied: group (control) who did not receive either surgical or medical treatment; groups 24 radical surgical removal of the focus, supplemented: No. 2 antituberculosis therapy, group 3 antituberculosis therapy and a single injection of bisphosphonates (pamidronate), group 4 a single injection of bisphosphonates. In autopsy material studied: the area of bone tissue, the thickness of bone beams, the number of osteoblasts, osteocytes, osteoclasts and the proportion of their active forms.
 RESULTS: The following features were revealed in intact samples of different groups: group 1 the minimum area of bone tissue and the thickness of the beams, the maximum number of osteoblasts, including active ones, the average number of osteocytes; groups 2 and 3 average values of the area and thickness of bone beams, the average number of osteoblasts, the pool of osteocytes is represented mainly by inactive cells; groups 3 and 4 the minimum value of active osteoblasts; group 4 the maximum thickness of the bone beams, a greater total number of osteoblasts and osteocytes. No osteoclasts were found in any group.
 CONCLUSIONS: Different ratios of bone tissue area, thickness of bone beams, and osteoforming cellular elements in animals receiving different treatment indicate both the systemic effect of a specific process and the drug effect of anti-tuberculosis drugs and bisphosphonates on uninfected bones.

Multitarget Wireless Power Transfer System Using Metasurface for Quasi-Bessel Beams With Large Half Power Beam Length

We propose a multitarget wireless power transfer (WPT) system using a transmissive metasurface with quasi-nondiffraction Bessel beams. To provide similar powers for more different targets, a special metasurface is designed to achieve uniform energy distributions in the nondiffraction area of Bessel beams, which can increase the half-power beam length (HPBL) by 10% compared with ordinary Bessel beams. A transmissive metasurface unit with transmission coefficient of more than 90% and a phase shift range greater than 360° are presented to form the metasurface at 10 GHz, which further ensures the high efficiency of the generated Bessel beams. Various receiving parameters are analyzed at the energy receiving end to reduce the influence between different targets. Receiving antennas that can harvest energy are designed with different apertures at 10 GHz, and the system efficiencies with different receiving apertures and different spaces between the receiving targets are analyzed to determine the appropriate receiving parameters. Finally, a multitarget metasurface WPT system based on the quasi-Bessel beams is fabricated. Simulation and experimental results show that the system can achieve almost equal WPT efficiency for five targets. More than 91% of the incident power can be modulated to form the quasi-Bessel beams, and the efficiency of each target is greater than 4.4% for the simulated results and greater than 3.3% for the measured results. Analysis of the designed rectifier circuit further proves the rationality of the proposed WPT system, which can be used for multiple charging targets and maintain a uniform power transfer efficiency. The quasi-Bessel beams achieve the high-efficiency multitarget WPTs and simplify the circuit design of receiving targets, making WPT applicable to more scenarios.

PENGARUH PENGGUNAAN BAJA RINGAN PROFIL HOLLOW TERHADAP KUAT LENTUR BALOK BETON

When a load given to a concrete beam, the upper part of the beam will receiving compressive force, while the bottom holds tensile force. The maximum compressive force in the upper part of the beam gradually decreases to zero at the neutral line and then turns into tensile force that increases to maximum at the bottom fiber of the beam. The bottom part of the concrete below the neutral line does not receive any compressive forces, so it works as a conductor for tensile forces to the reinforcement. This study was intended to determine the effect of inserting hollow steel longitudinally to the tensile area of concrete beams in order to increase the load capacity and reduce the volume of concrete simultaneously. In this study, a one-point pressure test experiment was carried out using a Loading Frame with a sample of 28 days old concrete block with f'c = 21.04 MPa measuring 12cm x 18cm x 250cm. The reinforcement configuration is 4Ø10mm with fy = 450Mpa. The beams are casted in 3 variations consist of 2 samples each, which are normal beams, beams with 4x2 hollow steel profiles, and beams with 4x4 hollow steel profiles. The hollow profile steel was not removed during the test. From laboratory tests, it was found that although the reinforced hollow beam cracked early, the load capacity increased and 7.41% lighter than normal beam. Meanwhile, from the calculation simulation concluded, that to match the strength of hollow beams reinforced with hollow profile steel, solid beams need to be more ductile so that the dimensions need to be enlarged and become more expensive. This indicate that the voids in the tensile area of the beam are economically benefit while the stiffness of the concrete beam remain the same and even increasing flexural strength when a hollow profile steel inserted.

Flexural Behavior of Two-Span Continuous CFRP RC Beams.

This paper investigates the feasibility of replacing steel bars with carbon-fiber-reinforced polymer (CFRP) bars in continuous reinforced concrete (RC) beams. A numerical model is introduced. Model predictions are compared with the experimental results that are available in the literature. A comprehensive numerical investigation is then performed on two-span CFRP/steel RC beams with ρb2 = 0.61–3.03% and ρb1/ρb2 = 1.5, where ρb1 and ρb2 are tensile bar ratios (ratios of tensile bar area to effective cross-sectional area of beams) over positive and negative moment regions, respectively. The study shows that replacing steel bars with CFRP bars greatly improves the crack mode at a low bar ratio. The ultimate load of CFRP RC beams is 89% higher at ρb2 = 0.61% but 7.2% lower at ρb2 = 3.03% than that of steel RC beams. In addition, CFRP RC beams exhibit around 13% greater ultimate deflection compared to steel RC beams. The difference of moment redistribution between CFRP and steel RC beams diminishes as ρb2 increases. ACI 318-19 appears to be conservative, and it leads to more accurate predictions of moment redistribution in CFRP RC beams than that in steel RC beams.

Ductility of Concrete Beams Reinforced with FRP Rebars

Concrete beams reinforced with FRP rebars have greater durability than standard steel reinforced elements. The main disadvantage of using FRP rebars is the low ductility of elements which may be unacceptable in certain situations. There are several different ways of increasing the ductility of concrete elements, which are analyzed in this paper. They are compared based on efficiency, influence on durability and ease of construction. Less analyzed and tested methods are given more attention to try and expand the current knowledge and possibilities. For methods that lack experimental data, theoretical analysis is undertaken to assess the possible influence of that method on the increase in ductility. Ductility was obtained by calculating bending moment–curvature diagrams of cross sections for different reinforcement layouts. One method that lacks experimental data is confining the compressive area of beams with tensile FRP reinforcement. Theoretical analysis showed that confining the compressive area of concrete can significantly increase the ductility and bending capacity of beams. Since experimental data of beams reinforced with FRP rebars in tension and confined compressive area is sparse, some suggestions on the possible test setups are given to validate this theoretical analysis. Concrete beams reinforced with FRP can be detailed in such a way that they have sufficient ductility, but additional experimental research is needed.

Numerical simulation of damage patterns in the plastic hinge area of fire protected (SFRM) steel beams and its effect on their fire resistance

AbstractSprayed Fire‐Resistive Materials (SFRMs) are low strength, brittle materials used as passive fire protection on steel structural members. Their main drawback is that they can develop significant damage when the underlying steel member is subjected to mechanical deformations. The current study addresses numerically the damage patterns of the passive fire protection that could arise at the plastic hinge area of IPE steel beams and their effect on the fire resistance of the member. Initially, a numerical method that combines the smeared crack model and the discrete crack concept is implemented for the simulation of the mechanical behavior of the fire protective material and the prediction of the damage it sustains. The results of the mechanical analysis, considering the parameters of cross‐section height, SFRM thickness, monotonic or cyclic loading and presence of geometric initial imperfections, suggest that the damage pattern, which is a result of the combination of interface delamination and crack formation in the body of the material, can be categorized in two basic forms. In the sequel, a heat transfer analysis is conducted on the steel beams, under standard ISO‐834 thermal load, taking into account the damage derived by the mechanical analysis, in order to assess the reduction in the fire resistance of the beams, compared to the corresponding beams with an intact fire protection layer or without any fire protection.

Static Behavior of a Retractable Suspen-Dome Structure

A new design of a radially retractable roof structure based on the concept of the suspen-dome is proposed in this paper. The radially foldable bar structure is strengthened by the lower cable-strut system to obtain a higher structural stiffness. Then the comparison of the static behavior between the retractable suspen-domes and their corresponding foldable bar shell with quadrangular mesh is discussed. Moreover, the effects of different structural and geometric parameters, such as the rise-to-span ratio, the cross-section area of beams, cables and struts, and the pre-stress level of the lower cable-strut system, on the nodal displacements and member forces are investigated systematically. The results show that higher structural stiffness is anticipated with the introduction of cable-strut systems into the hybrid structure. When the rise-to-span ratio is equal to 0.2, the maximal nodal displacement of the suspen-dome reaches the minimal value. The increase of the cross-section area of steel beams contributes an enormous amount to the structural stiffness. Increasing cable and strut sections has little impact on the mechanical behavior of suspen-domes. Moreover, the prestress level of cable-strut systems has a slight influence on the nodal displacements and member forces. Parametric analysis can be regarded as an essential basis for the optimization of the design of a retractable suspen-dome structure.

ASSESSMENT OF PRECAST WIDE U BEAM-COLUMN SYSTEM FOR MITIGATION OF STRUCTURAL FAILURE FROM SEISMIC HAZARD IN THAILAND

A large number of low to moderate earthquake incidents have been witnessed in the northern and western parts of Thailand. These incidents usually lead to various damage levels in various structures. Therefore, a sufficient lateral force resisting structures should be designed for the construction in such earthquake-prone areas. This paper presents the relevance of using a typical composite wide U beam-column system for mitigation of structural failure and collapse from the seismic hazard in Thailand. The investigated composite structural system consists of precast U beams, precast columns, and cast-in-situ concrete over the precast U beams and in the joint regions. The system also includes post-tensioning in the cast-in-situ area of the composite beams. The system has widely been used in low- to mid-rise commercial building in Thailand. In order to scrutinize the seismic performance of the system, a half-scale specimen of the post-tensioned precast U beam-column joint was tested under an incremental displacement-controlled lateral cyclic load. The laboratory test revealed the drift capacity, damage pattern, strain development in the rebars etc. of the precast wide U beam-column interior joint. Based on the obtained drift capacity, displacement-based assessment of the system was carried out. In addition, the observed damages on the tested structure were evaluated using damage grading criteria for building subjected to earthquake. The assessment showed a high potential of the post-tensioned precast wide U beam-column system to mitigate the structural failure and collapse from the earthquake hazard. However, some improvements in the current seismic performance of the system are required to employ the system in high seismic zones.

Application of modern GIS technologies for inventory of protective forest strips, identification of waterlogged areas

Earlier there were conducted the studies of the climatic, soil, environmental and economic characteristics of natural landscapes and agricultural land in Krasnodar Territory, for example, Dinskoy district. It is located on the territory of the V-natural landscape. There were shown the results of study of the qualitative state of field-protective forest belts and their influence on the processes of expansion of land area waterlogged arable land using GIS technology as a tool of information-cartographical support of researches. The identification of forest strips in GIS was carried out, their area was determined, the types of forest strips were established, the condition and degree of damage were assessed, the area of beams whose growth is due to the violation of the natural watercourse was determined. There have been identified the areas and sites of necessary repair works and laying of new forest strips, areas and sites of field-protective forest strips that prevent natural water flow and which are planned for cutting down. The capital investments in the laying, restoration and uprooting of damaged and planned forest strips are calculated. The use of GIS technologies in the study makes it possible to increase the accuracy of the results of the assessment and forecast of the development of degradation processes, reduces the cost of research, and ensures an increase in efficiency of land use in agricultural production.

Effects of Longitudinal and Transverse Direction Opening in Reinforced Concrete Beam: The State of Review

The implementation of hollow cores in beams is getting popular nowadays because of its practical advantages. The reduction of disadvantages in the beams with an opening is based on the engineers’ knowledge and practical experiences too. Most of the researchers have started to learn about the hollow beams and also, the strengthening of these beams. Based on the reviews on various journals in the field of hollow beams, this article investigates the effect of shape, size, and position of opening and reviews the strengthening of hollow beams. Finally, it brings a judgment with the suggestions to provide hollow beams and the future scope for the research in the area of hollow beams.

Finite Element Analysis on Shear Behavior of High-Strength Bolted Connectors under Inverse Push-Off Loading

High-strength bolted shear connectors (HSBSCs), which can be demounted easily and efficiently during deconstruction, are recommended to replace the conventional steel studs in steel–concrete composite beams (SCCBs) to meet the requirements of sustainable development. The existing investigations on the behavior of HSBSCs mainly focus on the positive moment area of composite beams, in which the concrete slab is in compress condition. In this paper, a three-dimensional finite element model (FEM) was developed to investigate the performance of HSBSCs subjected to inverse push-off loading. Material nonlinearities and the interactions among all components were included in the FEM. The accuracy and reliability of the proposed FEM were initially validated against the available push-off test results. Load-carrying capacity and load–slip response of the HSBSCs under inverse push-off loading were further studied by the verified FEM. A parametric study was carried out to determine the influence of the concrete strength, the diameter and tensile strength of bolt and the clearance between the concrete slab and the bolt as well as the bolt pretension on the shear performance of HSBSCs. Based on the extensive parametric analyses, design recommendations for estimating the shear load at the first slip and load-bearing resistance of HSBSCs were proposed and verified.

Seismic design of the double-cell accordion-web reduced beam section connection

The Accordion-Web Reduced Beam Section (AW-RBS) connection consists of a corrugated web, replacing the flat web, within a limited area near the column face, which reduces the beam flexural strength and forces the plastic hinge to form in the corrugated zone. This paper presents a seismic design procedure in the framework of the U.S. design standards for a double-cell AW-RBS connection, which consists of two box sections oriented such that an accordion web is formed within a limited area in the beam. The analytical evaluation of the flexural strength of the beam with a corrugated web was first presented. Then, a step-by-step design method was proposed to size the connection. Quasi-static cyclic tests were conducted on two relatively identical specimens including double-cell AW-RBS connections. A detailed numerical model of a connection with deep beams and columns designed in accordance with the proposed design procedure was developed and a nonlinear analysis was performed to investigate the seismic response of the connection and verify the adequacy of the proposed design method for the beam sizes frequently used in steel moment-resisting frames. The results confirmed the satisfactory response of the double-cell AW-RBS connection under cyclic loading. The stable plastic hinge formed in the reduced area of beams as predicted in design and no yielding was observed in the beam-to-column groove weld. The findings of the numerical simulations confirmed that the AW-RBS connection with deep beams and columns could potentially exceed the plastic rotation limit for ductile moment connections without significant instability and strength degradation.

LEARNING TRAJECTORY PEMBELAJARAN LUAS PERMUKAAN KUBUS DAN BALOK

Learning trajectory merupakan alur pemikiran siswa yang dihasilkan dari Hypothetical learning trajectory (HLT). Learning trajectory yang dihasilkan pada pembelajaran materi luas permukaan kubus dan balok dapat dijadikan dasar bagi guru dalam mengembangankan model, metode serta bahan ajar yang akan digunakan dalam pembelajaran. Metode penelitian yang digunakan adalah metode penelitian design research yang bertujuan mengembangkan local instruction theory melalui kerjasama antara peneliti dan guru dalam meningkatkan kualitas pembelajaran. Metode design research terdiri dari tiga tahapan yaitiu pre experimen, teaching experiment dan restropective analysis. Teknik pengumpulan data yang digunakan dalam penelitian ini adalah dokumentasi, wawancara dan observasi, dan tes. Data yang diperoleh selanjutnya dianalisis secara deskriptif. Analisis data hasil dokumentasi, wawancara, observasi, dan tes dilakukan secara kualitatif.