Seismic behavior of composite bridge columns

“This study investigates experimentally and numerically the seismic behavior of large-scale hollow-core fiber-reinforced polymer-concrete-steel (HC-FCS) innovative bridge columns as a sustainable approach to endure and rapidly recover from natural disasters such as earthquakes. The HC-FCS column consisted of a concrete shell sandwiched between an outer fiber-reinforced polymer (GFRP) tube and an inner steel tube to provided continuous confinement for the concrete shell along with the height of the column. The columns have a slender inner steel tube with diameter-to-thickness (Ds/ts) ratios ranged between 85 to 254. Each steel tube was embedded into the footing, while the GFRP tube was not embedded into the footing. The HC-FCS columns having a high Ds/ts ratio of 147 and 254 with short embedded length (1.25 Ds) do not dissipate high levels of energy and display nonlinear elastic performance due to severe steel tube buckling and slippage. However, the column with a Ds/ts ratio of 85 combined with substantial embedment length (1.6 Ds) results in a nonlinear inelastic behavior, high-energy dissipation, and ductile behavior. A retrofitting technique for a high Ds/ts ratio HC-FCS column precluding buckling of the inner steel tube was proposed, examined, and approved to be effective. New bond-slip expressions were proposed based on the analytical solution to capture the bond-slip effect between steel and concrete accurately. New design guidelines were proposed for HC-FCS columns in flexural and shear, as well as the column-to-footing connection. The innovative column approved to be easy to construct and repaired with high strength, drift, and resilience connection compared to the conventional bridge columns”--Abstract, page iv

Behavior of Hollow-Core Composite Bridge Columns having Slender Inner Steel Tubes

This paper experimentally investigates the seismic behavior of three large-scale hollow-core fiber-reinforced polymer-concrete-steel (HC-FCS) columns. An HC-FCS column consisted of a concrete shell sandwiched between an outer glass fiber-reinforced polymer (GFRP) tube and an inner steel tube. Both tubes provided continuous confinement for the concrete shell along with the height of the column. The columns had two different steel tube diameter-to-thickness (Ds/ts) ratios of 85, and 254. Each steel tube was embedded into the footing, with an embedded length of 1.25-1.6 times its diameter, while the GFRP tube was not embedded into the footing. Two columns were tested as as-built specimens. Then, one of these columns was repaired and re-tested. This study revealed that HC-FCS columns having a high Ds/ts ratio of 254 and short embedded length (1.25 Ds) do not dissipate high levels of energy and display nonlinear elastic performance due to severe steel tube buckling and slippage. However, the column with a Ds/ts ratio of 85 combined with substantial embedment length (1.6 Ds) results in a nonlinear inelastic behavior, high-energy dissipation, and ductile behavior. A retrofitting technique for a high Ds/ts ratio HC-FCS column precluding buckling of the inner steel tube was proposed and examined. The retrofitting method was characterized by the use of an anchorage system with steel tube concrete filling at the joint interface region. The retrofitted column achieved the ductile behavior and performed well under seismic loading with flexural strength increased by 22%. However, the lateral displacement capacity decreased by 26% compared to the original column due to the residual deformations and stresses exhibited during the previous test

Seismic Performance of Hollow-Core HC-FCS Columns having Inner Steel Tube with High Diameter to Thickness Ratio

This paper experimentally investigates the seismic behavior of a large-scale hollow-core fiber-reinforced polymer-concrete-steel HC-FCS column under seismic cyclic loading. The HC-FCS column consisted of a concrete shell sandwiched between an outer fiber-reinforced polymer (FRP) tube and an inner steel tube. The FRP tube provides continuous confinement for the concrete shell along the height of the column while the steel tube provides the required flexural strength. The tested column has an inner steel tube that had a diameter-to-thickness ratio (Di/t) (of 254. The seismic performance of the precast HC-FCS column was compared to that of HC-FCS column having(Di/t) of 64. Three-dimensional numerical models were also developed using LS_DYNA software for modeling the HC-FCS columns. This study revealed that HC-FCS columns having very high (Di/t) and short embedded lengths do not dissipate high levels of energy and display nonlinear elastic performance due to steel tube slippage. However, the use of small values of (Di/t)combined with generous embedment length results in a nonlinear inelastic behavior, high energy dissipation, and ductile behavior

Inelastic Response Evaluation of Precast Composite Columns under Seismic Loads

This paper presents a non-linear finite element analysis of large-scale hollow-core fiber-reinforced polymer-concrete-thin walled steel (HC-FCS) precast columns under reversed cyclic loading. The HC-FCS columns provide an economical and efficient alternative to conventional concrete bridge columns. The precast HC-FCS column consists of a concrete shell sandwiched between an outer fiber-reinforced polymer (FRP) tube and an inner thin-walled steel tube. The steel tube diameter-to thickness (Di/ts) ratio was 254. The proposed FEA model was developed using LS_DYNA multipurpose software and was verified by experimental results performed in this study. The FE model was used to investigate some important phenomena such as thin-walled steel tube cyclic local buckling and to determine where and when steel tube yielding and damage initiation occurs. The comparison and analysis of the proposed model to predict local damages, failure patterns, and hysteretic curves were in reasonable accuracy with the experimental outcomes

Seismic Performance of Hollow-Core Composite Columns under Cyclic Loading

This paper experimentally investigates the seismic behavior of a large-scale, hollow-core, fiber-reinforced, polymerconcrete- steel HC-FCS column under cyclic loading. The typical precast HC-FCS member consists of a concrete wall sandwiched between an outer fiber-reinforced polymer (FRP) tube and an inner steel tube. The FRP tube provides continuous confinement for the concrete wall, along the height of the column. The column is inserted into the footing and temporarily supported; then, the footing is cast in place around the column. The seismic performance of the precast HC-FCS columns was assessed and compared with previous experimental work. The compared column had the same geometric properties; but the steel tube was 25% thicker than the column that was tested in this study. This paper revealed that these HC-FCS column assemblies were deemed satisfactory by developing the whole performance of such columns and using that performance to provide excellent ductility with inelastic deformation capacity by alleviating the damage at high lateral drifts

Nonlinear Analysis of Hollow-Core Composite Building Columns

This paper numerically investigates the behavior of hollow-core fiber-reinforced polymer-concrete-steel (HC-FCS) building columns under combined axial compression and flexural loadings. The HC-FCS column for buildings consists of an outer circular fiber-reinforced polymer (FRP) tube, an inner square steel tube, and a concrete wall between them. A three-dimensional numerical model has been developed using LS_DYNA software for modeling of large scale HC-FCS columns. The nonlinear FE models were designed and validated against experimental results gathered from HC-FCS columns tested under cyclic lateral loading. The FE results were in decent agreement with the experimental backbone curves. These models subsequently were used to conduct a parametric study investigating the effects of the concrete wall thickness, steel tube width-to-thickness (B/t) ratio, and local buckling instability on the behavior of the HC-FCS columns. The obtained local buckling stresses results from the FE models were compared with the values calculated from the empirical equations of the available design codes. Finally, an approximated expression based on the available empirical formulas and the FE model results has been proposed in this paper to calculate the local buckling stresses of HC-FCS columns

Developed Clustering Algorithms for Engineering Applications: A Review

Clustering algorithms play a pivotal role in the field of engineering, offering valuable insights into complex datasets. This review paper explores the landscape of developed clustering algorithms with a focus on their applications in engineering. The introduction provides context for the significance of clustering algorithms, setting the stage for an in-depth exploration. The overview section delineates fundamental clustering concepts and elucidates the workings of these algorithms. Categorization of clustering algorithms into partitional, hierarchical, and density-based forms lay the groundwork for a comprehensive discussion. The core of the paper delves into an extensive review of clustering algorithms tailored for engineering applications. Each algorithm is scrutinized in dedicated subsections, unraveling their specific contributions, applications, and advantages. A comparative analysis assesses the performance of these algorithms, delineating their strengths and limitations. Trends and advancements in the realm of clustering algorithms for engineering applications are thoroughly examined. The review concludes with a reflection on the challenges faced by existing clustering algorithms and proposes avenues for future research. This paper aims to provide a valuable resource for researchers, engineers, and practitioners, guiding them in the selection and application of clustering algorithms for diverse engineering scenarios

Medication Adherence Amongst Diabetic Patients in a Tertiary Healthcare Institution in Central Nigeria

Purpose: To investigate the degree of diabetic patients’ compliance with their prescribed medications, factors responsible for non-compliance and how compliance can be enhanced.Methods: The study involved 220 diabetic patients on anti-diabetic medication (insulin, metformin and gliclazide) visiting the out-patient clinic of the University of Ilorin Teaching Hospital, Nigeria, who met specific criteria. Questionnaires and patient interviews were used to gather information.Results: A total of 162 patients (73.64 %) of the patients were non-compliant with medications; 22 of the compliant patients were males while 36 were females. Twenty three of the compliant patients had no formal education unlike the rest. There was significant association (p < 0.05) between patients’ financial status and compliance. However, there was no significant association (p > 0.05) between number of prescribed medications, side effects, patients’ level of education, patients’ belief of efficacy of medication and compliance.Conclusion: A very high level of non-compliance to anti-diabetic medication has been observed in the facility studied. Institution of policies that will enhance compliance in these facilities and others in Nigeria is highly recommended.Keywords: Compliance, Adherence, Diabetic, Medication, Prescriptio

Interfacial Shear Bond Strength between Steel H-piles and Polymer Concrete Jackets

Steel H-piles have been used widely in bridge construction throughout the U.S. because of their relatively large load-carrying capacity while occupying a small area. However, many H-piles suffer from corrosion, which may lead to abrupt collapse. A cost-effective repair technique, including encasing the corroded region of the steel pile into a concrete jacket, which acts as an alternative load path for the applied axial load, has been used by several state Departments of Transportation. Methyl methacrylate polymer concrete (MMA-PC) is a type of concrete that is commonly used as a repair material. However, there is limited research on the assessment of bond strength between MMA-PC and steel elements. This paper investigates experimentally the bond behavior of seven full-scale steel H-piles encased in concrete jackets. The jackets were cast using either MMA-PC or Portland cement concrete (CC). Different embedment lengths of 63.5mm (2.5 in.), 127mm (5 in.), and 190.5mm (7.5 in.) were used for the MMA-PC and one embedment length of 254mm (10 in.) was used for the CC jacket. Cylindrical and prismatic jacket configurations were used and tested using push-out. The experimental results revealed that using the MMA-PC jacket was more effective compared with the CC jacket in relation to the load-carrying capacity. For design purposes, a shear bond stress of 2.96 MPa [0.43 kips per square inch (ksi)] can be used for MMA-PC jackets having an embedment length of at least 127mm (5 in.) whereas a value of 0.83 MPa (0.12 ksi) can be used for CC

Efecto de algunos factores fisiológicos en la producción de ácido cítrico por tres aislamientos de Aspergillus niger empleando aserrín hidrolizado como fuente de carbono

Introduction: Citric acid (2-hydroxy-propane-1, 2, 3-tricarboxylic acid) was first isolated from lemon juice in 1784. It is a primary metabolic product which is formed in the tricarboxylic acid (Krebs) cycle. It is estimated that the market value of citric acid will exceed two billion dollars in 2019. About 70% of total citric acid produced globally is utilized in food industry, while about 12% is utilized in pharmaceuticals and cosmetic industries and the remainder in other industrial purposes. The industrial production of citric acid is undertaken by fermentation process in the presence of filamentous fungi for large scale of production. Aspergillus niger is the most efficient fungus due to its ability to produce more citric acid per unit time and ferment different inexpensive raw materials. Materials and Methods: Three isolates of the fungus Aspergillus niger (An1, An2, An3) were used throughout this study using different carbon source concentration in the form of sawdust acid hydrolysis supplemented with different concentration of (NH4)2H2SO4 as a nitrogen source. The effect of hydrogen ion concentration and addition of methanol to the fermentation medium was also investigated. Results and Discussion: The results indicated that the optimization of carbon and nitrogen concentration had stimulatingeffect on citric acid production by the three used isolates. Moreover, addition of methanol at concentration of 1% at pH of 3.5 highly increased citric acid production. Conclusion: we concluded that the agriculture waste was a favorable substrate for the production of citric acid especially it is cost effective and easily obtainable