Finite element parametric study of reinforced concrete beams shear-strengthened with embedded FRP bars

The deep embedment (DE) of fibre-reinforced polymer (FRP) bars is a promising shear-strengthening scheme for existing concrete structures. In the current study, a three-dimensional nonlinear finite element (FE) model for DE-strengthened reinforced concrete beams was developed and validated. The FE and Concrete Society TR55 predictions were compared with published experimental results. The FE-predicted/experimental shear strength enhancement ratio is 1.08 with a standard deviation of 0.25, whereas the TR55-predicted/experimental shear strength enhancement ratio is 1.57 with a standard deviation of 0.54. A numerical parametric study was carried out. The results showed that the predicted shear strength enhancement was positively influenced by the use of inclined DE FRP bars and the increase in concrete compressive strength but decreased with the increase in shear span-to-effective depth ratio and internal steel stirrup-to-DE FRP bar ratio. The predicted percentage of shear strength enhancement was not significantly influenced by size effect

Nonlinear finite element modelling and parametric study of CFRP shear-strengthened prestressed concrete girders

This paper presents a three-dimensional nonlinear finite element (FE) model for prestressed concrete girders strengthened in shear with externally bonded carbon fibre reinforced polymer (CFRP) reinforcement. A total strain rotating crack model, where the crack direction changes with the change in the direction of the principal tensile stress, was used for the concrete. In this model, explicit modelling of the concrete shear behaviour after cracking, e.g. via a shear retention parameter, is not required as the crack plane is always a principal plane with no shear stresses. The FE model was validated using experimental results from the literature. An extensive parametric study was carried out to identify the effect of the concrete compressive strength, CFRP width-to-spacing ratio, CFRP thickness, girder effective depth, shear span to effective depth ratio, level of prestress, tendon profile, pre-cracking and CFRP-to-concrete interface model on the predicted shear force capacity. The results suggested that the predicted shear strength enhancement can be significant and increases with the increase in concrete compressive strength, CFRP width-to-spacing ratio, and CFRP thickness but decreases with the increase in girder effective depth and shear span to effective depth ratio.The first author gratefully acknowledges the financial support of KRG.This is the accepted manuscript. The final version is available from Elsevier at http://www.sciencedirect.com/science/article/pii/S0950061814012872

Precracked RC T-beams Repaired in Shear with Externally Bonded CFRP Sheets

This is the accepted version of the original publication available here: http://www.concrete.org/PUBS/JOURNALS/OLJDetails.asp?Home=SJ&ID=51683632.This study investigates the structural behavior of precracked reinforced concrete (RC) T-beams strengthened in shear with externally bonded carbon fiber-reinforced polymer (CFRP) sheets. It reports on seven tests on unstrengthened and strengthened RC T-beams, identifying the influence of load history, beam depth, and percentage of longitudinal steel reinforcement on the structural behavior. The experimental results indicate that the contributions of the external CFRP sheets to the shear force capacity can be significant and depend on most of the investigated variables. This study also investigates the accuracy of the prediction of the fiber-reinforced polymer (FRP) contribution in ACI 440.2R-08, UK Concrete Society TR55, and fib Bulletin 14 design guidelines for shear strengthening. A comparison of predicted values with experimental results indicates that the guidelines can overestimate the shear contribution of the externally bonded FRP system.This work was funded by the Engineering and Physical Sciences Research Council [grant number GR/S55101/01]

CFRP shear strengthening of reinforced-concrete T-beams with corroded shear links

This paper investigates the structural behavior of uncorroded as well as corroded RC T-beams strengthened in shear with either externally bonded (EB) carbon fiber–reinforced polymer (CFRP) sheets or embedded CFRP rods. Nine tests were carried out on RC T-beams having an effective depth of 295 mm and a shear span to effective depth ratio of 3.05. The investigated parameters are the shear link corrosion level (uncorroded, 7% corroded, or 12% corroded) and type of CFRP strengthening system (EB CFRP sheets or embedded CFRP rods). The unstrengthened beams with shear link corrosion levels of 7 and 12% had shear strengths that were 11 and 14%, respectively, less than the shear strength of the uncorroded unstrengthened beam. Both the embedded CFRP rods and EB CFRP sheets were effective in enhancing the shear strength of tested beams but the effectiveness of both strengthening systems decreased with increasing shear link corrosion level. The shear strength enhancement provided by the embedded CFRP rods and EB CFRP sheets decreased from 19 and 15%, respectively, to 12 and 11%, respectively, with an increase in shear link corrosion level from 7 to 12%. Corrosion of the shear links did not have a significant effect on the beam stiffness. Premature debonding limited the effectiveness of the EB CFRP sheets whereas the embedded CFRP rods did not exhibit signs of debonding and therefore showed higher effectiveness.The authors would like to thank Fyfe Europe for supplying the CFRP sheets and epoxy laminating resin used in this study. The first author acknowledges the financial support of the UK Engineering and Physical Sciences Research Council.This is the author accepted manuscript. The final version is available from American Society of Civil Engineers via http://dx.doi.org/10.1061/(ASCE)CC.1943-5614.000054

ADOPTION AND ACCESS OF E-LIBRARY SERVICES IN UNIVERSITY LIBRARIES OF NORTH WEST ZONE OF NIGERIA

This paper examined the adoption and access of E-library services in University library of North west zone of Nigeria. Survey research method was adopted to carry out the study using descriptive research methodology. The population used under this study comprised all the state federal, state and private universities in North–West Geo-political zone of Nigeria, comprises of seventeen (17) studied universities, the population considered to be subject of the study includes other professional and non-professional staff in the Nigerian university libraries on the position of university librarian circumstantially. The sample size depends on the nature of the research of the study. It is however proposed to have a sample of seventeen (17) universities, therefore the number of the universities is manageable, and therefore no sampling is required. The instruments used data collection is questionnaire. Stratified sampling technique was used in selecting the secondary population of the study. Data was also analyzed using descriptive analysis using frequency tables and percentages. Stratified sampling technique was used in selecting the secondary population of the study. The administration of the questionnaire was carried out by the co researchers and assisted by three (3) research assistants. The study found that, adoption and accessing of the electronic library services and resources in Nigerian university libraries of North-west Geo-political Zone are basically for the purpose of effective, reliable, and adequate library information dissemination. The study has also identified that some universities have for long adopted and established the electronic unit earlier than other university libraries in the North-west Geo-political Zone of Nigeria. Consequent to that, it has been identified that all the sampled university libraries have established the electronic unit for the purpose of information dissemination via electronic devices for rapid and speedy information services. The study has further revealed that majority of the electronic unit or managers of the electronic section are specialists in the area of library and information science. The study recommends that encouragement from the government will give enough room and opportunity to provide adequate transformation of information electronically in Nigerian University libraries of north-west geo-political zone. There is the need for the university libraries to concretely form a consortium for the formation of unified electronic services and electronic resource sharing e.g. Universities library consortium, Hinary, Lefel, etc. One of the greatest challenges or threats to the adoption and accessing or sustainability of using the electronic resources in Nigeria is the issue of power supply. Efforts should be made by the authority concern to provide alternative in case of power failure during the transformation services. The alternative probably might be the provision of solar power or standby generator in order to alleviate the challenge of inadequacy or none supply of electricity power supply. University libraries being an academic institution library should try by all means to promote their electronic resources and services for the university community members to be aware of their availability and existence. Article visualizations

Derivation of Klein – Gordon Equation for Frictional Medium

The expression for a wave function in a conducting medium together with relativistic energy momentum relation is used to derive Klien - Gordon equation for frictional medium. This equation reduces to the ordinary Klein- Gordon equation in free space. For good conducted lasing is possible. The amplification coefficient is proportional to conductivity

Quantum Heat Flow Model for Heat Flow in Some Nanotubes

Using Schrodinger equation in a fractional medium a useful expression for heat flow through Nano tubes has been found. Fortunately, this equation resembles  that obtained by Moran Wang etal, and Hai- Dong Wang teal.   the ordinary thermal conductivity is constant. The effective thermal conductivity temperature dependent resembles that obtained for carbon Nano tubes and Boron Nitride Nano tubes. It is also finite at low temperature which also conforms with experimental data for carbon and Boron. Since Nano materials are described by quantum lows, this new model is thus more suitable for Nano tubes, as for as it is derived using quantum laws

Prevalence and burden of HBV co-infection among people living with HIV:A global systematic review and meta-analysis

Globally, in 2017 35 million people were living with HIV (PLHIV) and 257 million had chronic HBV infection (HBsAg positive). The extent of HIV-HBsAg co-infection is unknown. We undertook a systematic review to estimate the global burden of HBsAg co-infection in PLHIV. We searched MEDLINE, Embase and other databases for published studies (2002-2018) measuring prevalence of HBsAg among PLHIV. The review was registered with PROSPERO (#CRD42019123388). Populations were categorized by HIV-exposure category. The global burden of co-infection was estimated by applying regional co-infection prevalence estimates to UNAIDS estimates of PLHIV. We conducted a meta-analysis to estimate the odds of HBsAg among PLHIV compared to HIV-negative individuals. We identified 506 estimates (475 studies) of HIV-HBsAg co-infection prevalence from 80/195 (41.0%) countries. Globally, the prevalence of HIV-HBsAg co-infection is 7.6% (IQR 5.6%-12.1%) in PLHIV, or 2.7 million HIV-HBsAg co-infections (IQR 2.0-4.2). The greatest burden (69% of cases; 1.9 million) is in sub-Saharan Africa. Globally, there was little difference in prevalence of HIV-HBsAg co-infection by population group (approximately 6%-7%), but it was slightly higher among people who inject drugs (11.8% IQR 6.0%-16.9%). Odds of HBsAg infection were 1.4 times higher among PLHIV compared to HIV-negative individuals. There is therefore, a high global burden of HIV-HBsAg co-infection, especially in sub-Saharan Africa. Key prevention strategies include infant HBV vaccination, including a timely birth-dose. Findings also highlight the importance of targeting PLHIV, especially high-risk groups for testing, catch-up HBV vaccination and other preventative interventions. The global scale-up of antiretroviral therapy (ART) for PLHIV using a tenofovir-based ART regimen provides an opportunity to simultaneously treat those with HBV co-infection, and in pregnant women to also reduce mother-to-child transmission of HBV alongside HIV