فهرست مطالب ramin ehsani

In this paper, the results of Experimental Investigation Determination the Moment Redistribution and Plastic Hinge in continuous concrete Beams by replacing normal Concrete with HPFRCC and reducing the spacing of the stirrups are presented. Eight specimens of beam with reinforced concrete and fiber reinforced cement composites with bending distance were considered as three groups of A, B and C. Group A consisted of two conventional bending beams with standard bending intervals (d/2) (reference sample) and compact (d/4). Group B consists of four beams made of reinforced cement composites reinforced as a layer with non-compressive bending intervals (d/2) and Group C comprises two beams made of reinforced cement composites. Strong fibers were fully compressed (d/2) and compressed (d/4). Experimental results showed that using reinforced cement composite reinforced fibers instead of normal concrete in different parts of beams and the use of compacted stirrups increased the ductility of beams. In the specimens made of HPFRCC with compressive stirrups, bearing capacity, displacement ductility and energy ductility increased by 35, 77 and 83%, respectively, compared to the reference sample. The highest amount of moment redistribution, occurred in the specimen made with HPFRCC in the lower part with 1.51 times the reference beam.

Progressive failure is developed by expanding a local initial failure from one element to another, which ultimately leads to the collapse of the whole structure or a large part of it. This phenomenon causes local damage in structural elements which can result in massive losses and significant damage. Ductility, continuity, and degree of structural expansion are among the parameters that play an important role in reducing such consequences. In this study, the behaviour of a scaled four-span steel frame, with concrete filled steel tubular columns (CFST), was evaluated under progressive failure by removing the middle column. This work was done using the finite element method in ABAQUS. This work was carried out by examining the effect of reinforced triangular plate, haunch and angle steel reinforcements, reduced section in flange and web as well as post-tensioned FRP cables along with sensitivity analysis. The findings indicated that among the proposed anti-collapse methods, the maximum yield strength, the maximum ultimate strength and ductility ratio belong to angle steel reinforcement with 140.24 KN, reinforced triangular plate with 259.6 KN and RBS with 21.16 method. However, in a comprehensive comparison, the method of adding reinforced triangular plate was the best anti-collapse method since it avoids damage to the columns. Additionally, the change in compressive and tensile strength of the concrete did not have much effect on the frame behaviour in the progressive failure. Moreover, the frame with non-concrete columns has a ductility ratio 3 times higher than SRCT case, although the frame with SRCT columns has a 14 percent higher yield strength.

The particular weaknesses of concrete are brittle fracture and lack of material ductility, so using steel reinforcements and discrete fibres are an attempt to overcome this weakness. Strain hardening behaviour under tensile force has made new material HPFRCC as a high performance material with high energy absorption capability and high cracking ability before failure, Therefore the structural application of this composite material in the structural members such as continuous beams to control cracks and improve ductility has come to the believed border. In this paper, the effect of using HPFRCC containing 2% steel fibres on the flexural performance of four large two-span reinforced concrete beams has experimentally been investigated. Two beams were conventional concrete with two different arrangements of stirrups in the central support area and two other beams were companion but made with full HPFRCC composites, all beams with two equal spans of 1800 mm were loaded under concentrated force applied in the middle of the span symmetrical and incrementally. The results indicated that the use of HPFRCC with 2% steel fibre in the specimens increased the ductility, energy absorption, and bearing capacity, as well as an appropriate re-distributing moment in the plastic area of reinforced concrete continuous beam with two spans.

A huge number of deaths in the world are the direct or indirect consequence of a disease which is called atherosclerosis. The disease could be due to an artery blockage by the interaction of an externally second phase with a particle which is entered to the bloodstream. The effect of some most important physical and geometrical affecting parameters on the blockage time of a microchannel due to the impact of a particle and a second moving second phase is investigated. Shan-Chen Lattice Boltzmann multi-phase model is used in present study. It is investigated that the small change in the Capillary number does not affect the dynamics of the mechanism and the procedure steps significantly. But, smaller Capillary numbers cause breaking up the second phase in to more parts and with these smaller parts, the risk of small capillaries blockage in the arterial section of bloodstream decreases significantly. The blockage time will increase by an increase in the ratio of particle size to the channel width and the initial size of the second phase to channel width ratio has the highest effect on the blockage time.