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Article

Faezeh Nejati Barzoki, Ghanbar Ali Sheikhzadeh, Morteza Khoshvaght Aliabadi and Ali Akbar Abbasian Arani

The purpose of this paper is to investigate thermohydraulic characteristics of turbulent flow of water (4,000 = Re = 10,000) in a rectangular channel equipped with…

Abstract

Purpose

The purpose of this paper is to investigate thermohydraulic characteristics of turbulent flow of water (4,000 = Re = 10,000) in a rectangular channel equipped with perforated chevron plat-fin (PCPF) with different vortex generators (VGs) shapes.

Design/methodology/approach

First, three general shapes of VGs including rectangular, triangular and half circle, are compared to each other. Then, the various shapes of rectangular VGs, (horizontal, vertical and square) and triangular VGs, (forward, backward and symmetric) are evaluated. To comprehensively evaluate the thermohydraulic performance of the PCPF with various VG shapes, the relationship between the Colburn factor and the friction factor (j/f) is presented, then a performance index (η) is applied using these factors.

Findings

Results show that the enhanced models of the PCPF, which are equipped with VGs, have higher values of j/f ratio and η as compared with the reference model (R). Further, the half-circle VG with the lowest pressure drop values (about 2.4% and 4.9%, averagely as compared with the S and ST vortex generators), shows the highest thermohydraulic performance among the proposed shapes. The maximum of performance index of 1.14 is found for the HC vortex generator at Re = 4,000. It is also found that the square and forward triangular VGs, have the best thermohydraulic performance among the rectangular and triangular VGs respectively and the highest performance index of 1.13 and 1.11 are reported for these VGs.

Originality/value

The thermohydraulic performance of the PCPF with different vortex generators VGs shapes have been investigated.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. ahead-of-print no. ahead-of-print
Type: Research Article
ISSN: 0961-5539

Keywords

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Article

Faezeh Nejati and S.A. Edalatpanah

The purpose of this paper is to investigate the effect of steel and carbon fibers on the mechanical properties of light concrete in terms of tension strength, compressive…

Abstract

Purpose

The purpose of this paper is to investigate the effect of steel and carbon fibers on the mechanical properties of light concrete in terms of tension strength, compressive strength and elastic modulus under completely dry and wet conditions.

Design/methodology/approach

In this study, the lightweight concrete made of Light Expanded Clay Aggregate (LECA) as coarse aggregate and sand as fine aggregate was used. To achieve a compressive strength of at least 20 MPa, microsilica was used 10 percent by weight of cement. In order to compensate for the reduction of tension strength of concrete, steel and carbon fibers were used with three volume ratio of 0.5, 1 and 1.5 percent in concrete. The results of concrete specimens were studied at the age of 7, 28, 42 and 90 days under controlled dry and wet conditions.

Findings

The results showed that the addition of steel and carbon fibers to the concrete mixture would reduce the drop in slump. Also, the use of steel and carbon fibers plays a significant role in increasing the tension strength of the specimens. Furthermore, the highest increase in tension strength of steel and carbon fiber samples was 83.3 and 50 percent, respectively, than the non-fibrous specimen when evaluated at 90 days of age. Moreover, the steel and carbon fiber increased the water absorption of the samples. Adding steel and carbon fibers to a lightweight concretes mixture containing LECA aggregates plays a significant role in increasing the modulus of elasticity of the samples. The highest increase in the elastic modulus of steel and carbon fibers was 18.9 and 35.4 percent, respectively, than the non-fibrous specimen at 28 days of age.

Originality/value

In this paper, the authors investigated the mechanical properties of steel fiber and carbon reinforced concrete. Also, according to the conditions of storage of samples and the age of concrete (day), the experiments were carried out on samples.

Details

International Journal of Structural Integrity, vol. 11 no. 2
Type: Research Article
ISSN: 1757-9864

Keywords

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Article

Faezeh Nejati, Mahmood Hosseini and Amir Mahmoudzadeh

Almost design code is required for repairability of the buildings after a major earthquake. One such idea is “directed-damage design” (DDD), which means guiding the damage…

Abstract

Purpose

Almost design code is required for repairability of the buildings after a major earthquake. One such idea is “directed-damage design” (DDD), which means guiding the damage to some pre-decided parts of the structural system. To use the DDD idea for creation of repairable buildings, in this study, a structural system with seesaw motion with respect to a central massive support has been considered for steel buildings with square plan, and the bottom ends of the all circumferential columns at the lowest story have been equipped with double-ADAS (DADAS) dampers, which dissipate a great portion of the seismic input energy. The purpose of this paper is to investigate the hysteretic behavior of DADAS dampers by using finite element analysis. At first, a set of regular steel multistory buildings with five stories have been designed based on the conventional code provisions. Then, the structures of the designed buildings have been changed into the structure with seesaw motion by using, at the base level of the building, a massive central column, eliminating other middle columns, and equipping circumferential columns with DADAS dampers.

Design/methodology/approach

For repairability buildings in the last three mentioned studies a set of orthogonal strong girders, in the form of grid, has been used. In the present study, the number of bays in the considered building is four in both directions. A major modification has been made in the yielding-plate energy dissipating elements of the circumferential columns, which makes their manufacturing and installation much practical as illustrated in the following sections of the paper.

Findings

In the proposed rocking structural system for regular multistory steel buildings, creation of the possibility of rocking motion has been done by using a space truss resting on a huge central hinge support at base level with a series of circumferential energy dissipating columns at that level.

Originality/value

One such idea is DDD idea, which means guiding the damage to some pre-decided parts of the structural system.

Details

International Journal of Structural Integrity, vol. 8 no. 3
Type: Research Article
ISSN: 1757-9864

Keywords

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