Wyniki wyszukiwania - Biblioteka Nauki

1

A new design of a photonic crystal fiber with a beam shaping effect and flexible management of dispersion and confinement loss

100%

Huang Y. , Jiang P. , Yang H. , Yu M.

Optica Applicata

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2014

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tom Vol. 44, nr 3

375--387

EN

A new design of a guiding-index photonic crystal fiber which possesses a beam shaping effect and flexible control of dispersion has been proposed in this paper. It can shape a Gaussian beam into a circular hollow beam with certain dimension, which can be used in optical communication systems with a Cassegrain antenna to improve transmission efficiency by avoiding the loss of energy caused by the subreflector center reflection. In addition, its dispersion and confinement loss can be changed in a broad range by slightly adjusting structural parameters under condition that the hollow beam dimension remains about the same. Fairly practical properties, zero dispersion or flattened dispersion, can be obtained when structural parameters are set appropriately. A series of models with different parameters are analyzed and compared. Results of numerical simulation show that the ultra-low dispersion of 1.802 ps/km/nm can be obtained when λ = 1.31 μm. Several modest design parameters are given as well.

2

Thermal behavior of hollow and solid steel beamswith different boundary conditions

63%

Daud H. A. , Daud S. A. , Al-Azzawi A. A.

Computer Assisted Methods in Engineering and Science

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2021

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tom Vol. 28, no. 3

171--191

EN

The thermal behavior of hollow steel structural members due to the temperature increasehas not been investigated and discussed in many design codes. This work presents a studyof the hollow and solid steel beams’ carrying capacity under elevated temperatures. Thematerial properties of such beams decline under the temperature expected to increasethe moments on the beams. The finite difference technique is selected first to analyze theproblem. The solved problems cover beams under concentrated point load levels with dif-ferent end conditions such as cantilever, pin roller, and both ends fixed. The beam response(deflection, bending moment, and normal force) is examined. The finite element analysiswas conducted using the DIANA FEA software to study the same problem incorporatingmaterial and geometric nonlinearities. It was found that both finite difference and finiteelement analysis solved the problem accurately when the temperature was under 500C.It was also found that when the temperature was applied to the beam bottom face thedeflection was smaller than when the temperature was applied to the side faces only andthe whole section.

3

A study on the deflection and crack layout in a hollow slab bridge

51%

Wang S. , Wang D.

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tom Vol. 69, nr 3

541--555

EN

This paper conducts research based on the hollow slab members in the reconstruction and expansion project of expressways, two types of numerical finite element models with and without considering bond-slip relationship of reinforcement and concrete are established, and verified by tests. The distribution characteristics of crack spacing in reinforced concrete beams are studied. The results show that the bond-slip characteristics of reinforced concrete have little effect on the load-deflection characteristics of 8m hollow slab beam. Due to the influence of the bond-slip relationship of reinforced concrete, the load-deflection curve is partially serrated, while without considering the bond-slip relationship of reinforced concrete, the load-deflection curve is smooth. In the numerical model without considering the bond-slip characteristics, almost all damage occurs in the longitudinal direction, and the distribution characteristics of cracks can’t be accurately determined. Regardless of whether the bond-slip is considered or not, the macroscopic characteristics of the stress distribution is: smaller near the support and larger at the mid-span. As secondary flexural cracks expand, models with and without consideration of bond-slip characteristics can’t calculate crack spacing based on the stress distribution characteristics of the reinforcement.

4

Shear stresses of hollow lightweight concrete beams made with wood waste

51%

Alharishawi S. S. C. , Rajaa N. , Shihab L. A.

Archives of Civil Engineering

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2021

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tom Vol. 67, nr 1

657--672

EN

Hollow Lightweight Concrete (HLC) beams are gaining popularity due to low cost and low weight as compared with the Solid Lightweight Concrete (SLC) beams. HLC and SLC beams decrease in weight, without losing strength and durability. Flexural and shear behavior of reinforced HLC and SLC beams made with sawdust under two-point load is investigated in this study. The ultimate deformation efficiency and shear resistant mechanism of HLC beams are discussed experimentally and compared with other SLC beams. The beams, tested in this research, are rectangular. Beams were designed and constructed as 12 * 23 * 100 cm. Six concrete beam models were prepared including three SLC beams without the hollow and the other three HLC beams poured hollow 50 * 7.5 cm throughout the all beam of 100 cm. All beams were split according to the distance between vertical stirrups, these stirrups were divided into three specimens 45, 13, and 6 cm. By analyzing six experimental test beams, in this research, investigated the effect of diverse factors on the shear of beams. On comparison with normal concrete beams, this work describes the failure of mechanism, process, and ductility. The first crack loads, ultimate loads, load-deflection behavior, crack patterns and shapes of failure were investigated in this study. The experimental results show the ultimate performance of HLC beams are pure shear and controlled by yielding tension and compression steel bars. Also, it is found that the measured size and configuration of the hollow opening had an effect on the load-carry capacity and mid-span deflection of HLC beams. Thus, the design and construction details of beams can be additionally customized to reduce the total cost and weight of the HLC beams.

5

Laboratory tests of solid and hollow concrete beams made with glass waste

51%

Alharishawi S. S. C. , Rajaa N. , Jabur A. R.

Archives of Civil Engineering

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2023

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tom Vol. 69, nr 4

5--20

EN

The application of used glazed waste in concrete production can improve the performance of the structure of the building. Flexural and shear behavior and action of reinforced Hollow Glass Concrete Beams (HGCB) and Solid Glass Concrete Beams (SGCB) made with glass waste under a two-point load are studied in this paper. In this work, 6 reinforced concrete solid and hollow beams were tested under a four-point bending test to evaluate and calculate the flexural behavior of SGCB and HGCB. For that purpose, Beams were prepared with 1000 mm length, 230 mm height, and 120 mm. All beams were divided into groups and named according to the space stirrups steel bar. The experimental work investigates five main variables which are: first: the comparison between SGCB and HGCB with the concrete beams made with glass waste (Glass Concrete Beam GCB), second: comparison between Solid Concrete Beams for Normal Concrete Beams (NCB), and GCB, three: comparison between Hollow Concrete Beams for NCB and GCB, four: the comparison between HGCB and HCB, last: the comparison between SGCB and SCB. The test results indicated that GCB was offered higher strength than NCB, but the load-slip behavior of all specimens is similar for both types of concretes, and the bond strength is not influenced by steel specimens. Furthermore, the results of this study indicated that the contribution of GCB to the load is indicated to be considerable. The results indicate that the hollow opening affected the ultimate load capacity and deflection of HGCB.