Damage Characterization of Beam-Column Joints Reinforced with GFRP Under Reversed Cyclic Loading

The use of fiber reinforced polymer (FRP) reinforcement in concrete structures has been on the rise due to its advantages over conventional steel reinforcement such as corrosion. Reinforcing steel corrosion has been the primary cause of deterioration of reinforced concrete (RC) structures, resulting in tremendous annual repair costs. One application of FRP reinforcement to be further explored is its use in RC frames. Nonetheless, due to FRP\u27s inherently elastic behavior, FRP-reinforced (FRP-RC) members exhibit low ductility and energy dissipation as well as different damage mechanisms. Furthermore, current design standards for FRP-RC structures do not address seismic design in which the beam-column joint is a key issue. During an earthquake, the safety of beam-column joints is essential to the whole structure integrity. Thus, research is needed to gain better understanding of the behavior of FRP-RC structures and their damage mechanisms under seismic loading. In this study, two full-scale beam-column joint specimens reinforced with steel and GFRP configurations were tested under quasi-static loading. The control steel-reinforced specimen was detailed according to current design code provisions. The GFRP-RC specimen was detailed in a similar scheme. The damage in the two specimens is characterized to compare their performance under simulated seismic loading

Behaviour of reinforced self-consolidating concrete frames

Multi-storey reinforced concrete (RC) structural frames represent some of the most congested structural elements. Placing and consolidating concrete in such structural frames imposes substantial challenges. This offers a unique area of application for self-consolidating concrete (SCC) because of its inherent ability to flow under its own weight and fill congested sections, complicated formwork and hard-to-reach areas. Research is, however, needed to demonstrate the ability of SCC structural frames adequately to resist vertical and lateral loads. In the present study, full-scale 3 m high beam-column joints reinforced as per the Canadian Standards CSA A23·3-94 and ACI-352R-02 were made with normal concrete (NC) and SCC. They were tested under reversed cyclic loading applied at the beam tip and at a constant axial load applied on the column. The beam–column joint specimens were instrumented with linear variable displacement transducers and strain gauges to determine load–displacement traces, cumulative dissipated energy and secant stiffness. The current paper compares the performance of reinforced NC and SCC structural frames and discusses the potential use of SCC in such structural elements. Results indicate that reducing the coarse aggregate content in SCC mixtures can reduce the contribution of the aggregate interlock mechanism to total shear resistance, which leads to more rapid deterioration under cyclic loading. Further research is needed to ensure the safety of using low coarse aggregate content in SCC in highly seismic areas and assess the safety of already existing buildings cast using SCC

Nonlinear Model for Reinforced Concrete under Cyclic Loading

Most of the available shear models for reinforced concrete rely on empirical formulations. In this study, a rational shear stress function is used to define the shear stress–strain envelope for reinforced concrete. Cyclic rules are proposed to define the loading, unloading and reloading relationships for reinforced concrete under shear stress reversals. A normal stress function describing the cyclic relationship of concrete under axial stress is also introduced. The proposed functions are verified using experimental data of reinforced concrete panels tested under monotonic and cyclic loading. Subsequently, the normal and shear stress functions along with their cyclic rules are integrated in a non-linear finite element analysis code. The resulting model accounts for tension stiffening, crack opening and closing, compression hardening and softening, degradation of concrete strength and stiffness in the direction parallel to the crack, compression unloading and reloading, as well as non-linear steel behaviour (strain hardening and Bauschinger effect). The finite element model is then used to analyse two Portland Cement Association shear walls with different geometries tested under cyclic loading. The results show a good agreement between analytical and experimental data. The model showed an excellent capacity of predicting shear deformations of reinforced concrete elements under cyclic loading with minimal computational efforts

Predicting COVID-19 cases using Bidirectional LSTM on multivariate time series

Background: To assist policy makers in taking adequate decisions to stop the spread of COVID-19 pandemic, accurate forecasting of the disease propagation is of paramount importance. Materials and Methods: This paper presents a deep learning approach to forecast the cumulative number of COVID-19 cases using Bidirectional Long Short-Term Memory (Bi-LSTM) network applied to multivariate time series. Unlike other forecasting techniques, our proposed approach first groups the countries having similar demographic and socioeconomic aspects and health sector indicators using K-Means clustering algorithm. The cumulative cases data for each clustered countries enriched with data related to the lockdown measures are fed to the Bidirectional LSTM to train the forecasting model. Results: We validate the effectiveness of the proposed approach by studying the disease outbreak in Qatar. Quantitative evaluation, using multiple evaluation metrics, shows that the proposed technique outperforms state-of-art forecasting approaches. Conclusion: Using data of multiple countries in addition to lockdown measures improve accuracy of the forecast of daily cumulative COVID-19 cases

Nanosized Supramolecular Coordination Polymers Derived from Divalent Metal Ions, 4-Pyridylacetate and Auxiliary Ligands Containing Nitrogen and Phosphorus Donors

A series of coordination polymers of Co(II), Ni(II), Cu(II) or Cd(II) comprising 4-pyridylacetate (pya) and certain auxiliary ligands including benzimidazole (Hbzim), 1,10-phenanthroline (phen), 2,2'-bipyridine (2,2'-bipy),  2-amino-4-methylthiazole (A-Mtz), quinazole (Quz), 2,5-dimethylpyrazine (dpmz), bis(diphenylphosphino)methane (dpm), 1,2-bis(diphenylphosphino)ethane (dpe) and 1,3-bis(diphenylphosphino) propane (dpp) were prepared  and characterized by spectroscopic, magnetic and  thermal techniques. In these coordination polymers 4-pyridylacetate coordinates to the metal ions in a monodentate fashion through the carboxylate oxygens and/or the pyridyl nitrogen. Octahedral structures around the metal ions were suggested for all the complexes. The kinetic analyses of the thermal decomposition of the complexes were studied using the Coats-Redfern equation. The kinetic and thermodynamic parameters of the thermal decomposition were also calculated and discussed. From the X-ray powder diffraction data, the crystal parameters as well as the particle sizes (15.7-18.7 nm) of the complexes could be evaluated. Some of the compounds exhibit catalytic activity. The biological activity of the compounds was screened as well. DOI: http://dx.doi.org/10.17807/orbital.v13i1.155

Developing a Pattern-Based Method for Detecting Defective Sensors in an Instrumented Bridge

It is important to assure the reliability of a structural health monitoring system before interpreting the monitoring data for the detection of structural anomalies, Finding a malfunctioning component such as a sensor is an important step in that direction. Damage detection techniques in civil structures fall in the following two categories: data-driven and structural model-based. The data-driven methods provide a direct approach to damage assessment in a structure without creating any structural model (e.g. finite element model). Existence of damage and its location are interpreted by pattern matching of the data series of strain gauges, and temperature gauges at different time ranges. The objective of this study was to explore such methods, including the autoregressive exogenous (ARX) model, and based on that, develop new techniques to detect defective sensors. As a case study, the structural health monitoring data from the Portage Creek Bridge, located in the British Columbia, Canada was utilized to assess the conditions a set of sensors in of an instrumented pier, using methods developed based on the concepts of the sequential and binary search techniques. Continuous data sets of strain and temperature gauges were filtered and normalized. Defective sensors were detected by pattern matching of simulated and real data, using sensitivity analyses of the developed models

Curative role of lactulose, L-carnitine, alpha-lipoic acid and combination of L-carnitine and alpha-lipoic acid in a rat model of acute hepatic encephalopathy: Biochemical observations

Purpose: To determine whether a combination L-carnitine and α-lipoic acid (ALA) can alleviate the toxic effects of thioacetamide (TAA) via their potent antioxidant and free radical-scavenging activities.Methods: Rats were injected with TAA for 3 days to induce acute hepatic failure. TAA induced rats were treated with each of lactulose, L-carnitine and ALA alone and a combination of L-carnitine and ALA for 3 months. Thereafter, biochemical indices, ammonia levels, oxidative stress markers, and the levels of inflammatory markers were assessed in serum, liver and brain.Results: A significant improvement was observed after 3 months of antioxidants treatment. Lactulose, L-carnitine and ALA significantly decreased serum concentrations of alanine transaminase (ALT), aspartate aminotransaminase (AST) and level of total bilirubin while both levels of total protein (TP) and albumin (ALB) were significantly increased (p < 0.05 ) compared to TAA group. In addition, each of antioxidants alone significantly decreased ammonia (NH3) concentrations of serum, liver and brain in TAA-induced rats. Treatment with antioxidants for 3 months significantly (p < 0.05) decreased Malondialdehyde (MDA) and nitric oxide (NO) while antioxidant enzyme activities of glutathione peroxidase (GPX) and superoxide dismutase (SOD) were significantly increased (p < 0.05) in liver and brain tissues. The expressions of serum tumor necrosis factor-α (TNF-α) and soluble protein (S100-β) were significantly (p < 0.05) down-regulated in TAA-induced rats.Conclusion: L-carnitine in combination with ALA can mitigate HE induced experimentally in rats. The protective efficacy of L-carnitine in combination with ALA in HE can be attributed to suppression of oxidative stress, ammonia concentration and the levels of inflammatory markers. Thus, it may have the potential to be used to treat liver cirrhosis in clinical settings.Keywords: Lactulose, L-carnitine, α-Lipoic acid, Hepatic encephalopathy, Thioacetamide, Oxidative stress, Cirrhosis, Acute liver injur

Behçet’s disease: Spectrum of MDCT chest and pulmonary angiography findings in patients with chest complaints

AbstractObjectiveThe aim of the work was directed to evaluate the value of multi-detector computed tomography pulmonary angiography study in evaluation of known patients with Behcet’s disease.Materials and methodsThis study was done retrospectively and included eighteen known patients with Behcet’s disease and referred for MDCT pulmonary angiography.ResultsPulmonary artery aneurysm was the most common finding as it was found in 16 patients, followed by pulmonary embolism which was found in 14 patients, 12 patients with pulmonary hypertension, right ventricular strain in 6 patients, intracardiac thrombus in 4 patients, dilated bronchial arteries in 8 patients, venous occlusion in 4 patients, mosaic attenuation of the lung in 12 patients, pulmonary infarcts in 4 patients, and pleural effusion in 4 patients.ConclusionMDCT pulmonary angiography is an important diagnostic imaging tool for diagnosis of vascular complications in patients with Behcet’s disease

New Mixed Ligand Complexes of Ditertiary Phosphanes with Ni(II) Alkylxanthates

Mixed Iigand complexes of Ni(II) with alkylxanthates and ditertiary phosphanes of the composition Ni(ROCSSb(diphoshhave been prepared, where R = methyl, ethyl, propyl, butyl, and cyclohexyl and diphos = bis(diphenylphosphino)ethane (dpe) and bis- (diphenylphosphino)butane (dpb). The newly prepared compounds were characterized on the basis of chemical analyses, infrared and electronic spectra, lH-NMR, molar conductance, and thermal analysis. A square planar structure was proposed for the complexes