A Study on the Reinforced Fibrous Concrete Elements Subjected to Uniaxial Tensile Loading

Rashid Hameed,Anaclet Turatsinze,Frederic Duprat,Alain Sellier 대한토목학회 2010 KSCE JOURNAL OF CIVIL ENGINEERING Vol.14 No.4

The structural response of prisms of cross section 100×100 mm and length of 500 mm constructed with reinforced fibrous concrete and subjected to pure tensile loading has been presented in this contribution. The main focus was to study the effects of adding different metallic fibers in mono and hybrid form in the conventionally reinforced concrete on the tension stiffening and strain development. Two metallic fibers with different geometrical, mechanical and physical properties were investigated: amorphous metallic straight fibers and carbon steel hooked-end fibers. A total of four concrete mixtures: control, single fiber and hybrid fiber reinforced concretes were prepared. The fibers were investigated at content of 20 kg/m3 for single fiber reinforced concretes, and for hybrid fiber reinforced concrete, at content of 40 kg/m3. Through studying load-deformation response of composites and strain development in steel bar and concrete, it has been found that the metallic fibers improve tension stiffening effect and influence significantly the strain development. The effect of two metallic fibers on tension stiffening was seen to be different at different loading stages. On the other hand, when fibers were used in hybrid form, the behaviour of the composite was improved at all loading stages in terms of tension stiffening and resistance to cracking.

Bond stress-slip Behaviour of Steel Reinforcing Bar Embedded in Hybrid Fiber-reinforced Concrete

Rashid Hameed,Anaclet Turatsinze,Frédéric Duprat,Alain Sellier 대한토목학회 2013 KSCE JOURNAL OF CIVIL ENGINEERING Vol.17 No.7

Experimental study was carried out to evaluate the application of metallic fibers to confine the concrete in column-beam joint. Pullout tests on cubic specimens of size 200 × 200 × 200 mm with deformed steel bar embedded for a fixed length of 5 times the diameter of tested deformed bar were performed under monotonic applied displacement at the tip of the bar (displacement controlled tests). The key variable of the experimental study was the different confining conditions; by ordinary reinforcing steel bars, and by metallic fibers. To confine the concrete by the fibers, two different types of metallic fibers were used; amorphous metallic fibers and carbon steel hooked-end fibers. The fibers were investigated both in mono and hybrid forms. The dosage of fibers in mono fiberreinforced concrete was kept 40 kg/m3. In case of hybrid fiber-reinforced concrete, two concrete compositions were investigated: one containing 20 kg/m3 of each fiber and second containing 40 kg/m3 of each type of fiber. The pullout tests results revealed that both types of fibers contribute to ameliorate the peak bond stress and also to improve the ascending branch of the bond stress versus slip curve in terms of stiffness. Comparison of the bond stress-slip response of anchored bar in concrete confined by the ordinary reinforcing steel bars and by the metallic fibers demonstrated that the concrete confined by the fibers in hybrid form showed better performance than the concrete confined by the ordinary steel bars in terms of peak bond stress and toughness. Since the hybrid form of investigated metallic fibers realize same effect as that by ordinary steel, the congestion of steel in seismic resistant column-beam joint can be avoided by replacing some percentage of steel ratio to confine the concrete by the metallic fibers.

Simplified Approach to Model Steel Rebar-Concrete Interface in Reinforced Concrete

Rashid Hameed,Alain Sellier,Anaclet Turatsinze,Frédéric Duprat 대한토목학회 2017 KSCE Journal of Civil Engineering Vol.21 No.4

For correct description of cracking process in reinforced concrete structural elements, the simulation of the behaviour of steel rebarconcrete interface is always of primary importance. This paper proposes a simplified method to model the steel rebar-concrete interface in RC structures. The proposed method considers the introduction of massive elasto-plastic isotropic bond element as steel rebarconcrete interface. Stress-strain behaviour curve required for elasto-plastic isotropic material is obtained by performing conventional pull-out tests on concrete. For plain concrete matrix, an orthotropic damage model based on plasticity and damage theories was adopted for finite element modelling in Finite Element (FE) code CASTEM. In order to validate the proposed approach, a comprehensive experimental program was designed and carried out. Under this program, pure tension test on RC prisms and flexural test on RC beams were performed. Testing of proposed steel rebar-concrete interface bond model in numerical simulation of RC prism subjected to pure tension and RC beam in flexure, and comparison of numerical simulation results with experimental data is also discussed in this paper.

Strengthening of concrete damaged by mechanical loading and elevated temperature

Ahmad, Hammad,Hameed, Rashid,Riaz, Muhammad Rizwan,Gillani, Asad Ali Techno-Press 2018 Advances in concrete construction Vol.6 No.6

Despite being one of the most abundantly used construction materials because of its exceptional properties, concrete is susceptible to deterioration and damage due to various factors particularly corrosion, improper loading, poor workmanship and design discrepancies, and as a result concrete structures require retrofitting and strengthening. In recent times, Fiber Reinforced Polymer (FRP) composites have substituted the conventional techniques of retrofitting and strengthening of damaged concrete. Most of the research studies related to concrete strengthening using FRP have been performed on undamaged test specimens. This contribution presents the results of an experimental study in which concrete specimens were damaged by mechanical loading and elevated temperature in laboratory prior to application of Carbon Fiber Reinforced Polymer (CFRP) sheets for strengthening. The test specimens prepared using concrete of target compressive strength of 28 MPa at 28 days were subjected to compressive and splitting tensile testing up to failure and the intact pieces of the failed specimens were collected for the purpose of repair. In order to induce damage as a result of elevated temperature, the concrete cylinders were subjected to $400^{\circ}C$ and $800^{\circ}C$ temperature for two hours duration. Concrete cylinders damaged under compressive and split tensile loads were re-cast using concrete and rich cement-sand mortar, respectively and then strengthened using CFRP wrap. Concrete cylinders damaged due to elevated temperature were also strengthened using CFRP wrap. Re-cast and strengthened concrete cylinders were tested in compression and splitting tension. The obtained results revealed that re-casting of specimens damaged by mechanical loadings using concrete & mortar, and then strengthened by single layer CFRP wrap exhibited strength even higher than their original values. In case of specimens damaged by elevated temperature, the results indicated that concrete strength is significantly dropped and strengthening using CFRP wrap made it possible to not only recover the lost strength but also resulted in concrete strength greater than the original value.

Aluminum ASA 6061 Anodizing Process by Chromic Acid Using Box–Wilson Central Composite Design: Optimization and Corrosion Tendency

Khalid H. Rashid,Anees A. Khadom,Hameed B. Mahood 대한금속·재료학회 2021 METALS AND MATERIALS International Vol.27 No.10

The behavior of anodic porous alumina film formed on an aluminum surface by anodizing in chromic acid solutions wasoptimized using Box–Wilson experimental design. The film thickness was correlated as a function of temperature, acidconcentration, applied voltage, and time. A mathematical model was suggested and optimized. Results of coating thicknessindicate that both temperature and time play an important role in the anodizing process. The interaction effect of variableson the film thickness is less pronounced compared with the effect of the main variables. Optimum film thickness obtainedduring the anodizing process was 10.43 μm at the optimum value of temperature (45 °C) and time (68 min). The polarizationmeasurement of anodized aluminum ASA 6061 in chromic acid shows a high corrosion resistance in the presence ofcoating. The results confirmed by using surface morphology investigations.

Association of rs1042522 Polymorphism with Increased Risk of Prostate Adenocarcinoma in the Pakistani Population and its HuGE Review

Khan, Mohammad Haroon,Rashid, Hamid,Mansoor, Qaiser,Hameed, Abdul,Ismail, Muhammad Asian Pacific Journal of Cancer Prevention 2014 Asian Pacific journal of cancer prevention Vol.15 No.9

Prostate adenocarcinoma is one of the leading causes of cancer related mortality in men but still limited knowledge is available about its associated functional SNPs including rs1042522 (Pro72Arg). The present study was undertaken to explore the association of this SNP with susceptibility to prostate adenocarcinoma along with its structural and functional impacts in the Pakistani population in a case-control study. Three-dimensional structure of human TP53 with Pro72Arg polymorphism was predicted through homology modeling, refined and validated for detailed structure-based assessment. We also carried out a HuGE review of the previous available data for this polymorphism. Different genetic models were used to evaluate the genotypes association with the increased risk of PCa (Allelic contrast: OR=0.0.34, 95%CI 0.24-0.50, p=0.000; GG vs CC: OR=0.17, 95%CI 0.08-0.38, p=0.000; Homozygous: OR=0.08, 95%CI 0.04-0.15, p=0.000; GC vs CC: OR=2.14, 95%CI 1.01-4.51, p=0.046; Recessive model: OR=0.10, 95%CI 0.05-0.18, p=0.000; Log Additive: OR=3.54, 95%CI 2.13-5.89, p=0.000) except the Dominant model (OR=0.77, 95%CI 0.39-1.52, p=0.46). Structure and functional analysis revealed that the SNP in the proline rich domain is responsible for interaction with HRMT1L2 and WWOX. In conclusion, it was observed that the Arg coding G allele is highly associated with increased risk of prostate adenocarcinoma in the Pakistani population (p=0.000).

Reactivity of aluminosilicate materials and synthesis of geopolymer mortar under ambient and hot curing condition

Zafar, Idrees,Tahir, Muhammad Akram,Hameed, Rizwan,Rashid, Khuram,Ju, Minkwan Techno-Press 2022 Advances in concrete construction Vol.13 No.1

Aluminosilicate materials as precursors are heterogenous in nature, consisting of inert and partially reactive portion, and have varying proportions depending upon source materials. It is essential to assess the reactivity of precursor prior to synthesize geopolymers. Moreover, reactivity may act as decisive factor for setting molar concentration of NaOH, curing temperature and setting proportion of different precursors. In this experimental work, the reactivities of two precursors, low calcium (fly ash (FA)) and high calcium (ground granulated blast furnace slag (GGBS)), were assessed through the dissolution of aluminosilicate at (i) three molar concentrations (8, 12, and 16 M) of NaOH solution, (ii) 6 to 24 h dissolution time, and (iii) 20-100℃. Based on paratermeters influencing the reactivity, different proportions of ternary binders (two precursors and ordinary cement) were activated by the combined NaOH and Na2SiO3 solutions with two alkaline activators to precursor ratios, to synthesize the geopolymer. Reactivity results revealed that GGBS was 20-30% more reactive than FA at 20℃, at all three molar concentrations, but its reactivity decreased by 32-46% with increasing temperature due to the high calcium content. Setting time of geopolymer paste was reduced by adding GGBS due to its fast reactivity. Both GGBS and cement promoted the formation of all types of gels (i.e., C-S-H, C-A-S-H, and N-A-S-H). As a result, it was found that a specified mixing proportion could be used to improve the compressive strength over 30 MPa at both the ambient and hot curing conditions.

Biallelic mutations in pakistani families with autosomal recessive prelingual nonsyndromic hearing loss

Choi Hee Ji,Kanwal Sumaira,Hameed Rashid,Tamanna Nasrin,Perveen Shazia,Mahreen Hina,Son Wonseok,Lee Kyung Suk,Chung Ki Wha 한국유전학회 2023 Genes & Genomics Vol.45 No.2

Background Nonsyndromic autosomal recessive hearing loss (DFNB) is an etiologically heterogeneous disorder group showing a wide spectrum of onset ages and severity. DFNB genes are very diverse in their types and functions, making molecular diagnosis difficult. DFNB is particularly frequent in Pakistan, which may be partly due to consanguinity. Objective This study was performed to determine the genetic causes in Pakistani DFNB families with prelingual onset and to establish genotype-phenotype correlation. Methods Whole exome sequencing and subsequent genetic analysis were performed for 11 Pakistani DFNB families including eight consanguineous families. Results We identified eight pathogenic or likely pathogenic mutations in LOXHD1, GJB2, SLC26A4, MYO15A, and TMC1 from six families. The GJB2 mutations were identified in two families each with compound heterozygous mutations and a homozygous mutation. The compound heterozygous mutations in LOXHD1 ([p.D278Y] + [p.D1219E]) and GJB2 [p.M1?] + [p.G12Vfs*2]) were novel. The four missense or start-loss mutations were located at well conserved residues, and most in silico analysis predicted their pathogenicity. In addition to causative mutations, we found compound heterozygous mutations in PTPRQ as variants of uncertain significance. Conclusion This study identified biallelic mutations as the underlying cause of early onset DFNB in six Pakistani families. This study will be helpful in providing an exact molecular diagnosis and treatment of prelingual onset deafness patients.