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RISS 인기검색어
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- 저자 : Pourhaji, Pardis (검색결과 5 건)
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Strengthening of concrete structures with buckling braces and buckling restrained braces
Mazloom, Moosa,Pourhaji, Pardis,Farash, Abbas Moosa,Sanati, Amir Hossein Techno-Press 2018 Structural monitoring and maintenance Vol.5 No.3
The purpose of this article is to strengthen concrete structures using buckling and non-buckling braces. Connection plates are modeled in three shapes including the effect of 1.5t hinge zone length, 2t one and without the zone (1.5t-CP, 2t-CP and WCP). According to the verification performed with ABAQUS software, the connection plates which are superior in ductility and strengthening are found. The results show adding steel braces in concrete moment frames increase the strength and stiffness of the structures up to about 12 and 3 times, respectively. The frame strength increased about 21 and 25 percent with considering the effect of 2t hinge length in connection plates compared to 1.5t-CPs and WCPs. Also the ductility of retrofitted frames with 2t-CP improved 2.06 times more than WCP ones. Thus, 2t-CP sample is the best choice for connecting steel braces to concrete moment frames for retrofitting them. Afterwards, optimum conditions for elemental coating in braces with no buckling are assessed. The length of concrete coatings could be reduced about 30 percent, and buckling did not occur. Therefore, the weight of restraining coating decreased, and its performance improved. It is worth noting that BRBs could be constructed with only steel materials, which have outer steel tubes too. In fact, only the square cross sections of the tube profiles are appropriate for removing the filler concrete, and the rectangular ones are prone to buckle around their weak axis.
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Moosa Mazloom,Pardis Pourhaji,Oveys Afzali-Naniz 국제구조공학회 2021 Structural Engineering and Mechanics, An Int'l Jou Vol.80 No.1
In this paper, the effects of different replacement levels of halloysite nanotube (HNT), colloidal nano-silica (CS), micro-silica (MS), and the combination of them on the fresh and hardened properties of self-compacting lightweight concrete (SCLC) are studied. Four factors including water to binder ratio (w/b) with two levels of 0.35 and 0.45, CS with three replacement levels of 1, 3 and 5%, MS with the replacement level of 10% and HNT with three replacement levels of 1, 2 and 3% were chosen. The fresh properties of SCLCs were observed in terms of slump flow diameter and time, J-ring diameter, Vfunnel time and U-box tests. The hardened properties were determined through mechanical properties including compressive strength, tensile strength, modulus of elasticity and flexural strength. The non-destructive tests including electrical resistivity and water absorption were executed too. Moreover, the effects of MS, CS and HNT contents on the fracture energy of SCLC samples were studied. The results displayed that the mentioned properties for the SCLC specimens containingMS, CS and HNT improved, but the superior performance was obtained in binary mixes, which were created by adding both MS and CS simultaneously. The optimal conditions for having the best results were obtained when the amounts of MS and CS were 10% and 3%, respectively.
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Studying the effects of CFRP and GFRP sheets on the strengthening of self-compacting RC girders
Mazloom, Moosa,Mehrvand, Morteza,Pourhaji, Pardis,Savaripour, Azim Techno-Press 2019 Structural monitoring and maintenance Vol.6 No.1
One method of retrofitting concrete structures is to use fiber reinforced polymers (FRP). In this research, the shear, torsional and flexural strengthening of self-compacting reinforced concrete (RC) girders are fulfilled with glass fiber reinforced polymer (GFRP) and carbon fiber reinforced polymer (CFRP) materials. At first, for verification, the experimental results were compared with numerical modeling results obtained from ABAQUS software version 6.10. Then the reinforcing sheets were attached to concrete girders in one and two layers. Studying numerical results obtained from ABAQUS software showed that the girders stiffness decreased with the propagations of cracks in them, and then the extra stresses were tolerated by adhesive layers and GFRP and CFRP sheets, which resulted in increasing the bearing capacity of the studied girders. In fact, shear, torsion and bending strengths of the girders increased by reinforcing girders with adding GFRP and CFRP sheets. The samples including two layers of CFRP had the maximum efficiencies that were 90, 76 and 60 percent of improvement in shear, torsion and bending strengths, respectively. It is worth noting that the bearing capacity of concrete girders with adding one layer of CFRP was slightly higher than the ones having two layers of GFRP in all circumstances; therefore, despite the lower initial cost of GFRP, using CFRP can be more economical in some conditions.
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Moosa Mazloom,Pardis Pourhaji,Masoud Shahveisi,Seyed Hassan Jafari 국제구조공학회 2019 Structural Engineering and Mechanics, An Int'l Jou Vol.72 No.1
In this research, the vulnerability of some reinforced concrete frames with different stories are studied based on the Park-Ang Damage Index. The damages of the frames are investigated under various earthquakes with nonlinear dynamic analysis in IDARC software. By examining the most important characteristics of earthquake parameters, the damage index and vulnerability of these frames are investigated in this software. The intensity of Erias, velocity spectral intensity (VSI) and peak ground velocity (PGV) had the highest correlation, and root mean square of displacement (Drms) had the lowest correlation coefficient among the parameters. Then, the particle swarm optimization (PSO) algorithm was used, and the sinusoidal waves were equivalent to the used earthquakes according to the most influential parameters above. The damage index equivalent to these waves is estimated using nonlinear dynamics analysis. The comparison between the damages caused by earthquakes and equivalent sinusoidal waves is done too. The generations of sinusoidal waves equivalent to different earthquakes are generalized in some reinforced concrete frames. The equivalent sinusoidal wave method was exact enough because the greatest difference between the results of the main and artificial accelerator damage index was about 5 percent. Also sinusoidal waves were more consistent with the damage indices of the structures compared to the earthquake parameters.
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Assessing the ductility of moment frames utilizing genetic algorithm and artificial neural networks
Mazloom, Moosa,Afkar, Hossein,Pourhaji, Pardis Techno-Press 2018 Structural monitoring and maintenance Vol.5 No.4
The aim of this research is to evaluate the effects of the number of spans, height of spans, number of floors, height of floors, column to beam moment of inertia ratio, and plastic joints distance of beams from columns on the ductility of moment frames. For the facility in controlling the ductility of the frames, this paper offers a simple relation instead of complex equations of different codes. For this purpose, 500 analyzed and designed frames were randomly selected, and their ductility was calculated by the use of nonlinear static analysis. The results cleared that the column-to-beam moment of inertia ratio had the highest effect on ductility, and if this relation was more than 2.8, there would be no need for using the complex relations of codes for controlling the ductility of frames. Finally, the ductility of the most frames of this research could be estimated by using the combination of genetic algorithm and artificial neural networks properly.
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