EFFECTS OF XYLAZINE (ALPHA 2-ADRENERGIC AGONIST) ON THE STRESS RESPONSE TO IMMOBILIZATION AND HEAT IN RATS

Fayed, A.H.,Zakaria, A.D.,Hedaya, S.A.,El-Ashmawy, I.M. Asian Australasian Association of Animal Productio 1994 Animal Bioscience Vol.7 No.3

The effect of xylazine administration on plasma cortisol, prolactin, glucose and packed cell volume (PCV) responses to immobilization and heat stress was investigated. Immobilization of rats for 2 hours by ligation of the fore and hind legs strongly caused approximately two-fold increase in plasma cortisol and prolactin levels. Plasma glucose and PCV were not significantly changed. Pretreatment of immobilized rats with xylazine (20 mg/kg body weight i.m.) resulted in approximately 20% reduction in both plasma cortisol and prolactin concentrations. A marked hyperglycemia and increase in the PCV value was observed. On the other hand, rats exposed to acute heat stress ($40^{\circ}C$, and 60% relative humidity) for 2 hours, also developed two fold increase in both plasma cortisol and prolactin concentrations and the pretreatment with xylazine caused a 20% reduction in the levels of both hormones. Plasma glucose level was not significantly changed in heat stressed rats but it was markedly increased after pretreatment with xylazine. PCV was significantly incrcased under heat stress and pretreatment with xylazine induced a pronounced elevation in this value. It was suggested that stimulation of cortisol and prolactin secretion in response to immobilization or heat stress can be partially reduced by an alpha 2-adrenergic agonist.

Evaluate the effect of steel, polypropylene and recycled plastic fibers on concrete properties

Fayed, Sabry,Mansour, Walid Techno-Press 2020 Advances in concrete construction Vol.10 No.4

The impacts of reinforcing concrete matrix with steel fibers, polypropylene fibers and recycled plastic fibers using different volume fractions of 0.15%, 0.5%, 1.5% and 2.5% on the compressive and tensile characteristics are experimentally investigated in the current research. Also, flexural behavior of plain concrete (PC) beams, shear performance of reinforced concrete (RC) beams and compressive characteristics of both PC and RC columns reinforced with recycled plastic fibers were studied. The experimental results showed that the steel fibers improved the splitting tensile strength of concrete higher than both the polypropylene fibers and recycled plastic fibers. The end-hooked steel fibers had a positive effect on the compressive strength of concrete while, the polypropylene fibers, the recycled plastic fibers and the rounded steel fibers had a negative impact. Compressive strength of end-hooked steel fiber specimen with volume fraction of 2.5% exhibited the highest value among all tested samples of 32.48 MPa, 21.83% higher than the control specimen. The ultimate load, stiffness, ductility and failure patterns of PC and RC beams in addition to PC and RC columns strengthened with recycled plastic fibers enhanced remarkably compared to non-strengthened elements. The maximum ultimate load and stiffness of RC column reinforced with recycled plastic fibers with 1.5% volume fraction improved by 21 and 15%, respectively compared to non-reinforced RC column.

Improving Bond Performance of Near-Surface Mounted Steel Ribbed and Threated Rods in the Concrete

Sabry Fayed,Emrah Madenci,Yasin Onuralp Özkiliç,Mohamed H. Zakaria 한국콘크리트학회 2024 International Journal of Concrete Structures and M Vol.18 No.2

In this study, the experimental findings of twenty pull-out tests on the bond efficiency of threaded/ribbed steel rods used in near-surface mounting (NSM) are presented. On a groove (20 × 20 mm) that was slotted in one of the sides of a concrete block measuring 250 × 250 × 200 mm, a pull-out experiment was performed. The primary factors are the slot-filling materials (substrate concrete and epoxy paste), bonded length (equal to 5, 7, 10, and 15 times the rod diameter), surface pattern conditions (conventional ribbed reinforcing rebar and threaded bolt), use of nuts or rings welded at the free end of the bonded length, and use of straight or spiral wire welded along the length of the bonded length. The tested specimens' ultimate bond strength, slip, bond stress–slip response, failure patterns, stiffness, and ductility are recorded and assessed. The results showed that the ultimate bond strength and corresponding slip of ribbed rods cemented with epoxy were higher by 11.11% and 199%, respectively, than those of ribbed rods submerged in the substrate. Over the controls, all NSM epoxy-rods exhibited a greater ductility. As the bonded length increased, the ultimate bond strength of NSM rods fell by 12–32%. As the bonded length increased, the stiffness decreased. On the other hand, the ductility of NSM epoxy-rods increased as the bonded length increased. All applied schemes such as nuts, rings, longitudinal bars, and spiral bars significantly improved the ultimate bond strength (maximum = 25.93%) and corresponding slip (maximum = 166.67%) of NSM threaded rods as compared to the control ones.

Optimal location of a single through-bolt for efficient strengthening of CHS K-joints

Amr Fayed,Ali Hammad,Amr Shaat 국제구조공학회 2024 Structural Engineering and Mechanics, An Int'l Jou Vol.89 No.1

Strengthening of hollow structural sections using through-bolts is a cost-effective and straightforward approach. It’s a versatile method that can be applied during both design and service phases, serving as a non-disruptive and budget-friendly retrofitting solution. Existing research on axially loaded hollow sections T-joints has demonstrated that this technique can amplify the joint strength by 50%, where single bolt could enhance the strength of the joint by 35%. However, there's a gap in understanding their use for K-joints. As the behavior of K-joints is more complex, and they are widely existent in structures, this study aims to bridge that gap by conducting comprehensive parametric study using finite element analysis. Numerical investigation was conducted to evaluate the effect of through bolts on K-joints focusing on using single through bolt to achieve most of the strengthening effect. A full-scale parametric model was developed to investigate the effect of various geometric parameters of the joint. This study concluded the existence of optimal bolt location to achieve the highest strength gain for the joint. Moreover, a rigorous statistical analysis was conducted on the data to propose design equations to predict optimal bolt location and the corresponding strength gain implementing the verified by finite element models.

Taxonomic implications of multivariate analyses of Egyptian Ononis L. (Fabaceae) based on morphological traits

Abdel Aziz A. Fayed,Azza M. H. El-Hadidy,Ahmed M. Faried,Asmaa O. Olwey 한국식물분류학회 2019 식물 분류학회지 Vol.49 No.1

Numerical taxonomy is employed to determine the phenetic proximity of the Egyptian taxa belong- ing to the genus Ononis L. A classical clustering analysis and a principal component analysis (PCA) were used to separate 57 macro- and micromorphological characters in order to circumscribe 11 taxa of Ononis. A clus- tering analysis using the unweighted pair-group method with the arithmetic means (UPGMA) method gives the highest co-phenetic correlation. Results from clustering and PCA revealed the segregation of five groups. Our results are in line, to some certain degree, with the traditional sub-sectional concept, as can be seen in the group- ing of the representative members of the subsections Diffusae and Mittisimae together and the representative members of the subsections Viscosae and Natrix. The phenetic uniqueness of Ononis variegata and O. reclinata subsp. mollis was formally established. However, our findings contradict the classic sectional concept; this opin- ion was suggested earlier in previous phylogenetic circumscriptions of the genus. The most useful characters that provide taxonomic clarity were discussed.

Flexural strengthening of RC beams using externally bonded aluminum plates: An experimental and numerical study

Elsamak, Galal,Fayed, Sabry Techno-Press 2021 Advances in concrete construction Vol.11 No.6

This research investigated the flexural strengthening of RC beams using Aluminum plates (AP). An experimental program including 8 RC beams were carried out. The width and depth of the beam were 150 and 300 mm respectively while the effective span of the beam was 1560 mm. The tensile reinforcement ratios of the beams were 0.38 and 0.548%. The external APs ratios (the cross sectional area of AP to the beam cross sectional area) were 0.10, 0.37 and 0.74% while the AP length to the beam length was 0.93. A Finite element analysis (FEA) was investigated to study many variables that influenced on the ultimate load and the behavior of the AP-strengthened beams such as AP length, using shear connectors, using various techniques of the end anchorages and using anchored/unanchored U-shaped APs. It was noticed that the improvement ratios of the ultimate load and the ductility of strengthened beams with tensile reinforcement ratio of 0.38% was better than the beams with tensile reinforcement ratio of 0.548%. The AP length to the beam span ratio had a significant effect on the ultimate load, the ductility and the failure mode of the beams. The ultimate deflection and the ultimate load of the AP strengthened beams that used shear connectors increased by 165 and 54 % respectively compared to the beam without shear connectors. Using U-shaped AP jacket accompanied with end anchorages enhanced the ultimate load by 109%. The ultimate load of the beams with bolted U-shaped AP jacket increased by 128%.

Multilevel Percutaneous Vertebroplasty (More than Three Levels) in the Management of Osteoporotic Fractures

Zidan, Ihab,Fayed, Ahmed Abdelaziz,Elwany, Amr The Korean Neurosurgical Society 2018 Journal of Korean neurosurgical society Vol.61 No.6

Objective : Percutaneous vertebroplasty (PV) is a minimally invasive procedure designed to treat various spinal pathologies. The maximum number of levels to be injected at one setting is still debatable. This study was done to evaluate the usefulness and safety of multilevel PV (more than three vertebrae) in management of osteoporotic fractures. Methods : This prospective study was carried out on consecutive 40 patients with osteoporotic fractures who had been operated for multilevel PV (more than three levels). There were 28 females and 12 males and their ages ranged from 60 to 85 years with mean age of 72.5 years. We had injected 194 vertebrae in those 40 patients (four levels in 16 patients, five levels in 14 patients, and six levels in 10 patients). Visual analogue scale (VAS) was used for pain intensity measurement and plain X-ray films and computed tomography scan were used for radiological assessment. The mean follow-up period was 21.7 months (range, 12-40). Results : Asymptomatic bone cement leakage has occurred in 12 patients (30%) in the present study. Symptomatic pulmonary embolism was observed in one patient. Significant improvement of pain was recorded immediate postoperative in 36 patients (90%). Conclusion : Multilevel PV for the treatment of osteoporotic fractures is a safe and successful procedure that can significantly reduce pain and improve patient's condition without a significant morbidity. It is considered a cost effective procedure allowing a rapid restoration of patient mobility.

Flexural strengthening of RC one way solid slab with Strain Hardening Cementitious Composites (SHCC)

Basha, Ali,Fayed, Sabry,Mansour, Walid Techno-Press 2020 Advances in concrete construction Vol.9 No.5

The main aim of the current research is to investigate the flexural behavior of the reinforced concrete (RC) slabs strengthened with strain hardening cementitious composites (SHCC) experimentally and numerically. Seven RC slabs were prepared and tested under four-points loading test. One un-strengthened slab considered as control specimen while six RC slabs were strengthened with reinforced SHCC layers. The SHCC layers had different reinforcement ratios and different thicknesses. The results showed that the proposed strengthening techniques significantly increased the ultimate failure load and the ductility index up to 25% and 22%, respectively, compared to the control RC slab. Moreover, a three dimensional (3D) finite element model was proposed to analyze the strengthened RC slabs. It was found that the results of the proposed numerical model well agreed with the experimental responses. The validated numerical model used to study many parameters of the SHCC layer such as the reinforcement ratios and the different thicknesses. In addition, steel connectors were suggested to adjoin the concrete/SHCC interface to enhance the flexural performance of the strengthened RC slabs. It was noticed that using the SHCC layer with thickness over 40 mm changed the failure mode from the concrete cover separation to the SHCC layer debonding. Also, the steel connectors prevented the debonding failure pattern and enhanced both the ultimate failure load and the ductility index. Furthermore, a theoretical equation was proposed to predict the ultimate load of the tested RC slabs. The theoretical and experimental ultimate loads are seen to be in fairly good agreement.

Parametric studies on punching shear behavior of RC flat slabs without shear reinforcement

Galal Elsamak,Sabry Fayed 사단법인 한국계산역학회 2020 Computers and Concrete, An International Journal Vol.25 No.4

This paper proposed a numerical investigation based on finite elements analysis (FEA) in order to study the punching shear behavior of reinforced concrete (RC) flat slabs using ABAQUS and SAP2000 programs. Firstly, the concrete and the steel reinforcements were modeled by hexahedral 3D solid and linear elements respectively, and the nonlinearity of the used materials was considered. In order to validate this model, experimental results considered in literature were compared with the proposed FE model. After validation, a parametric study was performed. The parameters include the slab thickness, the flexure reinforcement ratios and the axial membrane loads. Then, to reduce the time of FEA, a simplified modelling using 3D layered shell element and shear hinge concept was also induced. The effect of the footings settlement was studied using the proposed simplified nonlinear model as a case study. Results of numerical models showed that increase of the slab thickness by 185.7% enhanced the ultimate load by 439.1%, accompanied with a brittle punching failure. The punching failure occurred in one of the tested specimens when the tensile reinforcement ratio increased more than 0.65% and the punching capacity improved with increasing the horizontal flexural reinforcement; it decreased by 30% with the settlement of the outer footings.

Flexural Behavior of Cracked RC Beams Retrofitted with Strain Hardening Cementitious Composites

Ali Basha,Sabry Fayed,Galal Elsamak 대한토목학회 2019 KSCE Journal of Civil Engineering Vol.23 No.6

In the present research, the efficiency and the effectiveness of different Ultra High Performance Strain Hardening Cementitious Composites (UHP-SHCC) schemes for flexure retrofitting of a cracked RC beams were investigated experimentally, numerically and analytically. The experimental program consisted of six RC beams. The control specimen was loaded until failure. The middle third part of the control specimen was replaced with UHP-SHCC, then, it was loaded again until failure. The other five beams were loaded until 52% of the failure load of the control beam, then they were retrofitted with a layer of UHP-SHCC casted at tension side. The main parameters were thickness and the reinforcement ratio of UHP-SHCC layer with two different lengths of UHP-SHCC layer. The test results showed that using UHP-SHCC layer is a highly effective technique to increase the flexural capacity and the ductility of RC beams. As the reinforcement ratio of the layer increased, the flexural capacity increased. The flexural capacity of the beams with a layer length of 75% beam span was less than the capacity of the beams having a layer length equal to the beam span. Analytical and numerical results agreed with the experimental results.