Structural performance of precast foamed concrete sandwich panel subjected to axial load

In this paper, experimental and simple analytical studies on the structural behavior of Precast Foamed Concrete Sandwich Panel (PFCSP) were reported. Full-scale tests on six PFCSP panels varying in thickness were performed under axial load applications. Axial load-bearing capacity, load-deflection profiles, load-strain relationships, slenderness ratio, load-displacement, load-deformation, typical modes of failure and cracking patterns under constantly increasing axial loads were discussed. Nonlinear Finite Element Analysis (FEA) using LUSAS software to investigate the structural behavior of PFCSP was contacted. The computed ultimate strength values using American Concrete Institute equation (ACI318) and other empirical formulas developed by pervious researchers which applicable to predict the ultimate strength capacity of sandwich panels were compared with the experimental test results and FEA data obtained; therefore, very conservative values resulted, a significant agreement with the FEA data that presented a high degree of accuracy with experiments and an increase in slenderness function

Motives for khat use and abstinence in Yemen - a gender perspective

<p>Abstract</p> <p>Background</p> <p>Khat consumption is widespread in Yemeni society and causes problems both in economic development and public health. Preventive measures have been largely unsuccessful and the cultivation continues to proliferate. The gender-specific motives for khat use and abstinence were studied to create a toe-hold for more specific interventions.</p> <p>Methods</p> <p>In a quota sample with equal numbers of males, females, abstainers and consumers, 320 subjects were interviewed on their specific opinions about khat and its impact on subjective and public health, and on social and community functioning. Strata were compared in their acceptance and denial of opinions. Notions that could predict abstinence status or gender were identified with multivariate logistic regression analysis.</p> <p>Results</p> <p>Male khat users had a strong identification with khat use, while females were more ambivalent. The notion that khat consumption is a bad habit (odds ratio (OR) 3.4; p < 0.001) and consumers are malnuorished (OR 2.2; p = 0.046) were associated with female gender among khat users. Among the females worries about health impact (OR 3.2; p = 0.040) and loss of esteem in the family (OR 3.1; p = 0.048) when using khat predicted abstinence. Male abstainers opposed khat users in the belief that khat is the cause of social problems (OR 5.1, p < 0.001). Logistic regression reached an accuracy of 75 and 73% for the prediction of abstinence and 71% for gender among consumers. (All models p < 0.001.)</p> <p>Conclusions</p> <p>Distinct beliefs allow a differentiation between males, females, khat users and abstainers when targeting preventive measures. In accordance to their specific values female khat users are most ambivalent towards their habit. Positive opinions scored lower than expected in the consumers. This finding creates a strong toe-hold for gender-specific public health interventions.</p

Flexural strength of FRP plated RC beams using a partial-interaction displacement-based approach

esigning FRP plated RC beams using full-interaction moment-curvature analysis would often suggest that the RC structure is brittle with debonding often occurring prior to yielding of the reinforcement steel. For that reason, researchers have looked into a displacement-based approach that takes into account the member debonding mechanism. The force in the plate within the debonded region was assumed to remain at the intermediate crack debonding force, PIC, and the ultimate strength was determined by considering compatibility of displacements along the member length. However, from laboratory testing, it is seen that the force in the externally bonded FRP plate keeps building up until failure occurs. Therefore, in this study, an extension to the displacement-based approach developed by previous researchers for FRP plated beams is presented where the residual bondstress of the plate within the debonded region is incorporated in the analysis. This is achieved by adopting a bond-slip model with a residual shear component that allows for the force in the plate to increase beyond PIC. The ultimate strength of the FRP plated beams is determined when the plate displacement matches that of the concrete near the plate end. A comparison with the experimental results of seven adhesively plated beams shows that incorporating the residual bondstress of the externally bonded plate yields significant improvement in accuracy and give better correlation with experimental findings

RC beam strengthening using hinge and anchorage approach

Retrofitting of existing structures using adhesively bonded plates has been a major growth area in civil engineering and has gained well-deserved popularity over the past few years. This strengthening technique is in line with sustainable practices in construction and can be used to preserve eminent structures of historical or cultural values. This study aims to present an ideal design model for strengthening reinforced concrete elements using the hinge and anchorage design philosophies for retrofitting and plating existing structures. This includes a check on the intermediate crack (IC), critical diagonal crack (CDC), and plate end (PE) debonding mechanisms. The results of a theoretical model for an FRP plated reinforced concrete beam element were presented, and the findings showed that plating increased the shear at the datum point to cause a diagonal crack by 46.7%. The increase in moment capacity due to plating the hogging region was 64.3% while allowing for 30% moment redistribution from the sagging region to the hogging region. The accompanying increase in uniformly distributed load due to 30% moment redistribution was 42.8%. The results of the theoretical model were compared with previous design models for IC debonding to which it has been shown that following the anchorage approach, a higher strain in the plate may be allowed as compared to the hinge approach. In addition to the theoretical model presented, analysis on an FRP plated RC beam and slab were also presented to show the effect of different plate widths on the moment capacity and PE moment capacity

Acid and Sulphate Attacks on a Rubberized Engineered Cementitious Composite Containing Graphene Oxide

The objective of this research was to determine the durability of an engineered cementitious composite (ECC) incorporating crumb rubber (CR) and graphene oxide (GO) with respect to resistance to acid and sulphate attacks. To obtain the mix designs used for this study, response surface methodology (RSM) was utilized, which yielded the composition of 13 mixes containing two variables (crumb rubber and graphene oxide). The crumb rubber had a percentage range of 0–10%, whereas the graphene oxide was tested in the range of 0.01–0.05% by volume. Three types of laboratory tests were used in this study, namely a compressive test, an acid attack test to study its durability against an acidic environment, and a sulphate attack test to examine the length change while exposed to a sulphate solution. Response surface methodology helped develop predictive responsive models and multiple objectives that aided in the optimization of results obtained from the experiments. Furthermore, a rubberized engineered cementitious composite incorporating graphene oxide yielded better chemical attack results compared to those of a normal rubberized engineered cementitious composite. In conclusion, nano-graphene in the form of graphene oxide has the ability to enhance the properties and overcome the limitations of crumb rubber incorporated into an engineered cementitious composite. The optimal mix was attained with 10% crumb rubber and 0.01 graphene oxide that achieved 43.6 MPa compressive strength, 29.4% weight loss, and 2.19% expansion. The addition of GO enhances the performance of rubberized ECC, contributing to less weight loss due to the deterioration of acidic media on the ECC. It also contributes to better resistance to changes in the length of the rubberized ECC samples

Mechanics-based approach for predicting the short-term deflection of CFRP plated RC beams

Most design codes available today for predicting the deflection of adhesively plated RC beams use a full-interaction moment-curvature approach that requires the flexural rigidity to be quantified empirically. Due to their empirical nature, these design rules can only be applied within the bounds of the tests from which they were derived. Furthermore, as these design rules follow a full-interaction analysis, the slip between the reinforcement and adjacent concrete was not considered and the method does not cope with the discrete rotation of the cracks; that is, the deflection associated with crack widening was not directly considered. As an alternative, partial-interaction mechanics-based methods can be used. In this study, a mechanics-based approach for quantifying the deflection of adhesively plated RC beams was presented. The approach took into account the slip between the reinforcement and adjacent concrete, the formation and widening of flexural cracks, and the intermediate crack debonding mechanism of the externally bonded plate. The deflection from the mechanics-based approach was determined by considering the discrete rotation of individual cracks and the curvature of uncracked regions of the beam. The deflection results derived from the mechanics-based approach were compared with the experimental results of seven adhesively plated CFRP RC beams bonded to their tension face and a significant correlation between the results was observed. The mechanics-based approach does not require any components on the member level to be quantified empirically; thus, it could be useful in predicting the deflection of adhesively plated RC beams with new types of reinforcement material

BCNet: A Deep Learning Computer-Aided Diagnosis Framework for Human Peripheral Blood Cell Identification

Blood cells carry important information that can be used to represent a person&rsquo;s current state of health. The identification of different types of blood cells in a timely and precise manner is essential to cutting the infection risks that people face on a daily basis. The BCNet is an artificial intelligence (AI)-based deep learning (DL) framework that was proposed based on the capability of transfer learning with a convolutional neural network to rapidly and automatically identify the blood cells in an eight-class identification scenario: Basophil, Eosinophil, Erythroblast, Immature Granulocytes, Lymphocyte, Monocyte, Neutrophil, and Platelet. For the purpose of establishing the dependability and viability of BCNet, exhaustive experiments consisting of five-fold cross-validation tests are carried out. Using the transfer learning strategy, we conducted in-depth comprehensive experiments on the proposed BCNet&rsquo;s architecture and test it with three optimizers of ADAM, RMSprop (RMSP), and stochastic gradient descent (SGD). Meanwhile, the performance of the proposed BCNet is directly compared using the same dataset with the state-of-the-art deep learning models of DensNet, ResNet, Inception, and MobileNet. When employing the different optimizers, the BCNet framework demonstrated better classification performance with ADAM and RMSP optimizers. The best evaluation performance was achieved using the RMSP optimizer in terms of 98.51% accuracy and 96.24% F1-score. Compared with the baseline model, the BCNet clearly improved the prediction accuracy performance 1.94%, 3.33%, and 1.65% using the optimizers of ADAM, RMSP, and SGD, respectively. The proposed BCNet model outperformed the AI models of DenseNet, ResNet, Inception, and MobileNet in terms of the testing time of a single blood cell image by 10.98, 4.26, 2.03, and 0.21 msec. In comparison to the most recent deep learning models, the BCNet model could be able to generate encouraging outcomes. It is essential for the advancement of healthcare facilities to have such a recognition rate improving the detection performance of the blood cells