Behavior of corroded bonded fully prestressed and conventional concrete beams

AbstractPrestressed concrete is widely used in the construction buildings. And corrosion of steel is one of the most important and prevalent mechanisms of deterioration for concrete structures. Consequently the capacity of post-tension elements decreased after exposure to corrosion. This study presents results of the experimental investigation of the performance/behavior of bonded fully prestressed and conventional concrete beams, with 40MPa compressive strength exposed to corrosion. The experimental program of this study consisted of three fully prestressed and two conventional concrete beams with overall dimensions equal to 150×400×4500mm. The variables were considered in terms of corrosion exposure effect, prestressed level, and corrosion location effect for fully prestressed beams. Mode of failure, cracking width/distribution, ultimate load and the corresponding deflection of each beam were recorded. The results showed that the fully prestressed beam in comparison with conventional beam was considered to be even more resistance to corrosion because it was perceived to be crack-free as a result of prestressing. Also the mention deterioration incident in fully prestressed beams fully corrosion exposure level unnoticed that deterioration incident in partially corrosion exposure level. The most of deterioration incident in fully prestressed beam acts on compression of non-prestressed steel reinforcement. Because the bonded tendons are less likely to corrode. Cement grout/duct is a barrier to moisture and chloride penetration, especially plastic duct without splices. The theoretical analysis based on strain compatibility and force equilibrium gave a good prediction of the deformational behavior for fully prestressed beams

Behavior of corroded bonded partially prestressed concrete beams

Prestressed concrete is widely used in the construction industry in buildings. And corrosion of reinforcing steel is one of the most important and prevalent mechanisms of deterioration for concrete structures. Consequently the capacity of post-tension elements decreased after exposure to corrosion. This study presents results of the experimental investigation of the performance and the behavior of partially prestressed beams, with 40 and 80 MPa compressive strength exposed to corrosion. The experimental program of this study consisted of six partially prestressed beams with overall dimensions equal to 150 × 400 × 4500 mm. The variables were considered in terms of concrete compressive strength, and corrosion location effect. The mode of failure, and strain of steel reinforcement, cracking, yield, ultimate load and the corresponding deflection of each beam, and crack width and distribution were recorded. The results showed that the partially prestressed beam with 80 MPa compressive strength has higher resistance to corrosion exposure than that of partially prestressed concrete beam with 40 MPa compressive strength. Not big difference in deterioration against fully/partially corrosion exposure found between partially prestressed beams at the same compressive strength. The most of deterioration incident in partially prestressed beam acts on non prestressed steel reinforcement. Because the bonded tendons are less likely to corrode, cement grout and duct act as a barrier to moisture and chloride penetration, especially plastic duct without splices and connections. The theoretical analysis based on strain compatibility and force equilibrium gave a good prediction of the deformational behavior for high/normal partially prestressed beams. Keywords: Beam, Corrosion, Deterioration, Partially prestressed, High strength concret

Effect of infill wall on the ductility and behavior of high strength reinforced concrete frames

AbstractThis paper presents an experimental study for the behavior and ductility of H.S.R.C frames with infill wall under the effect of cyclic load. The experimental program was conducted on four specimens (frames). The parameters are studied change panel of frame from non infill to infill, change thickness of infill wall and change type of bricks. The dimension of frames is selected to represent half scale frames and tested under cyclic loading. All specimens of experimental program are tested in the reinforcement concrete testing laboratory at the Housing and Building National Research Center – Cairo.From the representation and the analysis of the obtained results, the main conclusions are pointed out; the lateral load resistance for infilled frames F2, F3 and F4 with infill wall (red bricks) thickness 12, 6cm and cement bricks 12cm, respectively was greater than the bare frame (F1) by about 184%, 61% and 99%, respectively. The ductility factor for infilled frames F2, F3 and F4 was less than the bare frame (F1) by about 57%, 51% and 46%, respectively

Characterization and Efficacy of A Novel Formula of Insulin Chitosan Layered Duple Hydroxide-Nanohybrid for Oral Administration

The development of an oral insulin therapy remains an ultimate goal to both enhance ease of use, and to provide therapeutic advantages rooted in its direct delivery to the portal vein and liver. The current study aimed to develop a novel formula for insulin oral administration against experimental diabetes in rats. Entrapped insulin (INS) between chitosan nanoparticles (CSNPs) and layered duple hydroxide (LDH) (LDH-INS-CSNPs) was chemically prepared, and characterized by X-ray diffraction, Fourier transformation infrared, high-resolution transmission electron microscope, field emission scanning electron microscope and Zeta potential measurements. The insulin release study was conducted in vitro, while the oral hypoglycemic effect of LDH-INS-CSNPs was investigated in vivo in diabetic rats. The prepared formulas revealed a variation in the spectra of characterization methods. The insulin entrapment between LDH and chitosan avoided the burst release of insulin and acid denaturation in the stomach and enzymatic degradation throughout the gut. Consequently, the blood glucose level of LDH-INS-CSNPs formula exhibited a marked hypoglycemic effect. The present work showed that the LDH-INS-CSNPs formula had a protective effect against enzymatic degradation, reduced insulin initial burst release, and enhanced bioavailability through the oral administration route. Interestingly, the presented formula could be an oral antidiabetic agent alternative to injectable insulin