The Changes of Bridge Loads During the Long-term Period

Karas Slawomir,Hypki Mateusz 대한토목학회 2016 KSCE JOURNAL OF CIVIL ENGINEERING Vol.20 No.5

The aim of the paper is an analysis of bridge loads changes in the 20th century. The Polish bridge load standards issued in the 20th century are considered here. The two static approaches are adopted on the basis of the model of the real composite of a steel and concrete bridge carrying-deck. The first of them, the traditional simplified Courbon method which was in use up to the 1970s, gives bending moment results. The other one is the analysis by the ABAQUS FEM. The dynamic response of the structure is performed for the set of velocities starting from 10 km/h to 90 km/h. Basing on the obtained results, it is concluded that the load increase is essential for bridge sustainability in all phases i.e. for design, maintenance and optional rebuilding. Having in mind that, in general, the indicative service life of a bridge is intended for 100 years approximately, i.e. for three generations, the prognosis of load changes is crucial. The bridge load effects increase over the past century is estimated at 60% to 85%, it being at least 30%.

Development of new predictive analysis in the orthogonal metal cutting process by utilization of Oxley's machining theory

Abdelkader Karas,Mohamed Bouzit,Mustapha Belarbi,Redha Mazouzi 국제구조공학회 2015 Steel and Composite Structures, An International J Vol.19 No.6

This paper presents a contribution to improving an analytical thermo-mechanical modeling of Oxley's machining theory of orthogonal metals cutting, which objective is the prediction of the cutting forces, the average stresses, temperatures and the geometric quantities in primary and secondary shear zones. These parameters will then be injected into the developed model of Karas et al. (2013) to predict temperature distributions at the tool-chip-workpiece interface. The amendment to Oxley's modified model is the reduction of the estimation of time-related variables cutting process such as cutting forces, temperatures in primary and secondary shear zones and geometric variables by the introduction the constitutive equation of Johnson-Cook model. The model-modified validation is performed by comparing some experimental results with the predictions for machining of 0.38% carbon steel.

Critical buckling analyses of nonlinear FG-CNT reinforced nano-composite beam

Zerrouki, Rachid,Karas, Abdelkader,Zidour, Mohamed Techno-Press 2020 Advances in nano research Vol.9 No.3

This paper investigates the effect of linear and non-linear distribution of carbon nanotube volume fraction in the FG-CNTRC beams on the critical buckling by using higher-order shear deformation theories. Here, the material properties of the CNTRC beams are assumed to be graded in the thickness direction according to a new exponential power law distribution in terms of the carbon nanotube volume fractions. The single-walled carbon nanotube is aligned and distributed in the polymeric matrix with different patterns of reinforcement; the material properties of the CNTRC beams are described by using the rule of mixture. The governing equations are derived through using Hamilton's principle. The Navier solution method is used under the specified boundary conditions for simply supported CNTRC beams. The mathematical models provided in this work are numerically validated by comparison with some available results. New results of critical buckling with the non-linear distribution of CNT volume fraction in different patterns are presented and discussed in detail, and compared with the linear distribution. Several aspects of beam types, CNT volume fraction, exponent degree (n), aspect ratio, etc., are taken into this investigation. It is revealed that the influences of non-linearity distribution in the beam play an important role to improve the mechanical properties, especially in buckling behavior. The results show that the X-Beam configuration is the strongest among all different types of CNTRC beams in supporting the buckling loads.

Effect of nonlinear FG-CNT distribution on mechanical properties of functionally graded nano-composite beam

Rachid Zerrouki,Abdelkader Karas,Mohamed Zidour,Abdelmoumen Anis Bousahla,Abdelouahed Tounsi,Fouad Bourada,Abdeldjebbar Tounsi,Kouider Halim Benrahou,S.R. Mahmoud 국제구조공학회 2021 Structural Engineering and Mechanics, An Int'l Jou Vol.78 No.2

This work focused on the novel numerical tool for the bending responses of carbon nanotube reinforced composites (CNTRC) beams. The higher order shear deformation beam theory (HSDT) is used to determine strain-displacement relationships. A new exponential function was introduced into the carbon nanotube (CNT) volume fraction equation to show the effect of the CNT distribution on the CNTRC beams through displacements and stresses. To determine the mechanical properties of CNTRCs, the rule of the mixture was employed by assuming that the single-walled carbon nanotubes (SWCNTs)are aligned and distributed in the matrix. The governing equations were derived by Hamilton’s principle, and the mathematical models presented in this work are numerically provided to verify the accuracy of the present theory. The effects of aspect ratio (l/d), CNT volume fraction (Vcnt), and the order of exponent (n) on the displacement and stresses are presented and discussed in detail. Based on the analytical results. It turns out that the increase of the exponent degree (n) makes the X-beam stiffer and the exponential CNTs distribution plays an indispensable role to improve the mechanical properties of the CNTRC beams.

Buckling of carbon nanotube reinforced composite plates supported by Kerr foundation using Hamilton’s energy principle

Ammar Boulal,Tayeb Bensattalah,Abdelkader Karas,Mohamed Zidour,Houari Heireche,E.A. Adda Bedia 국제구조공학회 2020 Structural Engineering and Mechanics, An Int'l Jou Vol.73 No.2

This paper investigates the buckling behavior of carbon nanotube-reinforced composite plates supported by Kerr foundation model. In this foundation elastic of Kerr consisting of two spring layers interconnected by a shearing layer. The plates are reinforced by single-walled carbon nanotubes with four types of distributions of uniaxially aligned reinforcement material. The analytical equations are derived and the exact solutions for buckling analyses of such type’s plates are obtained. The mathematical models provided, and the present solutions are numerically validated by comparison with some available results in the literature. Effect of various reinforced plates parameters such as aspect ratios, volume fraction, types of reinforcement, parameters constant factors of Kerr foundation and plate thickness on the buckling analyses of carbon nanotube-reinforced composite plates are studied and discussed.

Free vibration responses of nonlinear FG-CNT distribution in a polymer matrix

Mohamed Zidour,Rachid Zerrouki,Ahmed Hamidi,Youcef Tlidji,Abdelkader Karas,Abdelouahed Tounsi 국제구조공학회 2022 Smart Structures and Systems, An International Jou Vol.30 No.2

The object of this paper is to investigate the free vibration behavior under the effect of carbon nanotube distribution in functionally graded carbon nanotube-reinforced composite (FG-CNTRC) by using higher-order shear deformation theories. In this work, we present a novel distribution method for carbon nanotubes in the polymer matrix by using a new exponential power law distribution of carbon nanotube volume fraction. It is assumed that the SWCNTs are aligned along the beam axial direction and the distribution of the SWCNTs may vary through the thickness of the beam with different patterns of reinforcement. The rule of mixtures is used in order to obtain material properties of the CNTRC beams. Hamilton's principle is used in deriving the equations of motion. The validity of the free Vibration results is examined by comparing them with those of the known data in the literature. The results that obtained indicate that the carbon nanotube volume fraction distribution play a very important role on the free vibrations characteristics of the CNTRC beam.

Regulation of HBV-specific CD8+ T cell-mediated inflammation is diversified in different clinical presentations of HBV infection

Colin M. Dinney,Lu-Dong Zhao,Charles D. Conrad,Jay M. Duker,Richard O. Karas,Zhibin Hu,Michele A. Hamilton,Thomas R. Gillis,Thomas M. Parker,Bing Fan,Andrew H. Advani,Fred B. Poordad,Paulette L. Fauce 한국미생물학회 2015 The journal of microbiology Vol.53 No.10

Chronic HBV infection is the leading cause of liver cirrhosis and hepatic cancer, but the individual responses toward HBV infection are highly variable, ranging from asymptomatic to chronic active hepatitis B inflammation. In this study, we hypothesized that the different individual responses to HBV infection was associated with differences in HBV-specific CD8+ T cell-mediated inflammation and cytotoxicity. Blood samples were collected from subjects with asymptomatic HBV-infection, subjects undergoing active chronic HBV flares (active CHB), and subjects with HBV-infected hepatocellular carcinoma (HBV-HCC). By tetramer staining, we found that all three groups had similar frequencies of HBVspecific CD8+ T cells. However, after HBV peptide stimulation, the HBV-specific CD8+ T cells in asymptomatic subjects had significantly stronger interferon gamma (IFN-γ), tumor necrosis factor alpha (TNF-α), and CD107a expression than those in active CHB and HBV-HCC patients. Examination of surface marker expression revealed that the PD-1-Tim-3- double-negative cell population was the main contributor to HBV-specific inflammation. In active CHB patients and HBV-HCC patients, however, the frequencies of activated PD-1-Tim-3- cells were significantly reduced. Moreover, the serum HBV DNA titer was not correlated with the frequencies of HBV-specific CD8+ T cells but was inversely correlated with the frequencies of IFN-g-expressing and CD107a-express cells in response to HBV stimulation. Together, our data demonstrated that the status of HBVspecific CD8+ T cell exhaustion was associated with different clinical outcomes of chronic HBV infection.

Effect of Orifice Induced Hydrodynamic Cavitation on the Properties of Waste Activated Sludge

Esra Demir Karaçoban,Fatma Olcay Topaç,Efsun Dindar,Bülent Keskinler 대한토목학회 2024 KSCE Journal of Civil Engineering Vol.28 No.4

Exploring alternative methods to reduce the quantity of wastewater sludge and improve its characteristics is among the prioritized subjects in the field of sludge management. Hydrodynamic cavitation, commonly employed for water and wastewater treatment, also holds the potential for utilization as a pre-treatment method for sludge. In the presented study, the excess sludge obtained from the wastewater treatment facility of a food and beverage manufacturing factory was collected and disintegrated with a orifice-induced hydrodynamic cavitation unit. According to the data obtained, the highest cavitation performance was achieved under the condition where the cavitation number was set to 0.3. In addition, hydrodynamic cavitation performed under the optimum operating conditions, significantly increased the solubility of waste activated sludge. The results showed that the soluble chemical oxygen demand concentration, which was initially determined as 382 mg/l, reached 3,068 mg/l end of the cavitation. 64% of the total Kjeldahl nitrogen and 60% of the total phosphorus of waste-activated sludge were converted into soluble forms by the effects of hydrodynamic cavitation. Moreover, the results of the microbial study indicated that removal rates of indicator bacteria varied between 94% and 99%.

The effect of different earthquake ground motion levels on the performance of steel structures in settlements with different seismic hazards

Ercan Işık,İbrahim Baran Karaşin,Abdulhalim Karaşin 국제구조공학회 2022 Structural Engineering and Mechanics, An Int'l Jou Vol.84 No.1

The updated Turkish Building Earthquake Code has been significantly renovated and expanded compared to previous seismic design codes. The use of earthquake ground motion levels with different probabilities of exceedance is one of the major advances in structural mechanics with the current code. This study aims to investigate the earthquake performance of steel structure in settlements with different seismic hazards for various earthquake ground motion levels. It is focused on earthquake and structural parameters for four different ground motion levels with different probabilities of exceedance calculated according to the location of the structure by the updated Turkish Hazard Map. For this purpose, each of the seven different geographical regions of Turkey which has the same seismic zone in the previous earthquake hazard map has been considered. Earthquake parameters, horizontal design elastic spectra obtained and comparisons were made for all different ground motion levels for the seven different locations, respectively. Structural analyzes for a sample steel structure were carried out using pushover analysis by using the obtained design spectra. It has been determined that the different ground motion levels significantly affect the expected target displacements of the structure for performance criteria. It is noted that the different locations of the same earthquake zone in the previous code with the same earthquake-building parameters show significant variations due to the micro zoning properties of the updated seismic design code. In addition, the main innovations of the updated code were discussed.

Performance Analysis of Steel Structures with A3 Irregularities

Ercan Işık,Mesut Özdemir,İbrahim Baran Karaşin 한국강구조학회 2018 International Journal of Steel Structures Vol.18 No.3

Determination of the behaviour of structures during earthquakes is a very important engineering concern. Irregularities in the structure may lead to more damage imposed on it by weakening its defence mechanism during an earthquake. Some of these irregularities may be indentations or protrusions in the plan. Such irregular buildings may be encountered in practice because of various reasons. This study examined the state of irregularity by the A3 plan in the Turkish Building Earthquake Regulation of 2016. Four diff erent A3-type irregularity cases were considered. The building with no irregularities in its plan was taken as the reference building. The fi ve steel structures were compared by obtaining pushover curves for both the X and Y directions. Additionally, as a rapid assessment method, the Canada Seismic Screening Method was used in the study. Both in the rapid assessment method and from the pushover curves, it was determined that buildings without irregularities are safer. The study also allows a comparison among the earthquake performances of the structures using the rapid assessment method. It may be stated that there was an agreement between the two methods. This shows that the rapid assessment method may be used for steel structures. The importance of constructing structures that do not include irregularities is emphasized with the study. If one has to construct such structures, the defence mechanism of the structure should be strengthened by taking various measures.