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Go to Editorial ManagerFourier series and finite element analysis are utilized to obtain the solution of simply supported beams resting on elastic foundations with different loadings in order to arrive at a free vibration. The equation of the free vibration of beam on elastic foundation is derived and solved. Good agreement has been obtained between the results of the present study Fourier and finite element analysis and other previous solutions. The effect of modulus of subgrade reaction, axial tension force (foundation modulus) and beam depth on the behavior is studied.
Catalytic isomerization is a process used to increase the octane number of light naphtha fraction and thus aids in extending the life of automobile engines. Researchers are still working to prepare more effective and less expensive isomerization catalysts to replace the costly previous catalysts. Ongoing challenges in this field seek to design highly active isomerization catalysts operated under moderate conditions while keeping high branched-isomer selectivity. Heteropolyacids (HPA) have been presented as the most capable substitutes to fulfill the requirements. They are considered bifunctional catalysts that perform dehydrogenation /isomerization followed by hydrogenation because of their firm acidity and redox properties. Some catalytic-isomerization studies were started utilizing HPA in combination with platinum, which significantly improves the selectivity and stability. Thus, HPA-based bifunctional catalysts can provide enough acid and hydrogenation–dehydrogenation sites sufficiently. However, the most ongoing challenge in this field is the poor thermal stability of HPAs, which limits their use at higher temperatures for vapour-phase reactions. This review aims to highlight the recent progress in catalytic isomerization of alkanes using heteropolyacids supported on different carriers, with and without noble metals.
This paper presents experimental investigations to study the behavior of High Strength Reinforced Concrete (HSRC) deep beams with web openings under monotonic and static repeated loading conditions. The experimental work procedure consisted of testing eighteen simply supported HSRC deep beams both with and without web openings. The numerical work procedure consisted of testing ten simply supported HSRC deep beams both with web openings. All beams had the same dimensions and flexural reinforcement. They had an overall length of 1400 mm, a width of 150 mm and a height of 400 mm. The investigated test parameters were concrete compressive strength, shape and size of openings, vertical and horizontal reinforcement ratios, shear span to effective depth ratio (a/d ratio) and loading history. The experimental results reveal that the ultimate load capacities for specimens tested under four different repeated loading regimes decrease in the range between 2% and 19% in regards to the control specimens which were tested under monotonic loading regime. The results indicated that the increase in the severity of loading history leads to a decrease in the ultimate shear strength of the deep beams and causes increases in their ductility ratio. The ultimate loads of HSRC deep beams with square web openings size of (50*50mm, 60*60mm and 70*70mm) tested under the repeated loading history (HS-1) which consisting of five phases decreased by (11.4 %, 24.1% and 26.3 %, respectively) compared to that of identical solid deep beam. The ultimate load of HSCR deep beam with circular web openings shape tested under repeated loading history (HS-1) increases by 8.6 % compared to the equivalent square web openings shape. For numerically analyzed beams under repeated loading history (HS-1), the ultimate load increases by 16% when using area of 2500mm2 of circular web openings shape (equal in area to square web opening size 50mm*50mm) and by 13.5% when using rhombus web openings shape of the dimensions 50*50mm in comparison with the case of 60-mm size square web openings.
This paper deals with the elastic stability of a column bolted at its mid-height to a simply supported square plate and subjected to a concentrated load, using energy method. A uniform homogeneous column is assumed to be pinned at both ends. From symmetry considerations, half of the column is modeled by making the plate acting as a torsion spring on the column at its mid-height. The column length and cross-section, plate dimensions and thickness, and the material properties for the column and the plate catch the interest of the author. The problem is solved by using energy method and ultimately, the elastic buckling load is found. The analytical elastic buckling load is compared with a numerical solution obtained from finite element method using SAP2000. The numerical results agree with the analytical solution. The finite element model is refined to catch the actual effect of the bolted plate on the elastic buckling load. It has been found that the elastic buckling load is increased due to the increase in the rotational stiffness provided from the plate.
Construction joints are separations between successive concrete pours. They are critical in the building of large concrete structures, since these structures cannot be cast in a single pour. Self-consolidation concrete is a relatively new kind of concrete that is considered suitable for a wide range of construction applications, especially those needing a high early resistance. Certain findings from earlier experimental tests were adopted and analyzed using finite element analysis. ANSYS program was used to analyze the impact of utilizing high strength concrete (fc') and the secondary reinforcement ratio (ρv) on the behavior of reinforced self-consolidating concrete beams having a horizontal construction joint. Nine beams analyzed in this study have the same dimensions (150×180×1200) mm (width× height ×length). Between the two supports, the clear span was 1100 mm. Two-point loads were applied to the simply supported beams during testing. One of the beams acts as a control beam (without a construction joint) and the remaining beams were with horizontal construction joint in the tension zone. The ultimate loads obtained analytically vary by between 3.1% and 7.8 % from those found experimentally. The presence of the horizontal construction joints made the beam less stiff. Utilizing a 70 MPa high strength concrete resulted in a 47.4 % in ultimate load over the experimental value for regular strength concrete (28 MPa). Increasing the ratio of secondary reinforcement (0.01229 to 0.049) resulted in a 10.3% increase in ultimate load magnitude, while decreasing the ratio of secondary reinforcement (0.01229 to 0.0025) with spanning the spacing between stirrups led to a reduction in ultimate load magnitude by 55.8%.
A failing heart can be supported in several ways, including cardiopulmonary bypass pumps (CPB), extracorporeal membrane oxygenators (ECMOs), and other types of auxiliary heart pumps. The intra-aortic-balloon-pump (IABP) is one technique of internal counter-pulsation that supports maintaining the circulatory system It continues to be used as a vascular support device to critically unwell cardiac patients. Many recent studies have focused on the problems of the (IABP) in open-heart surgery, while other researchers concentrated on the positioning and size of the balloon, some of them studied the timing of the balloon's inflation and deflation. this paper has reviewed a brief Introduction, the basic principles of the balloon, how to trigger the balloon pump as well as the use of IABP in Coronary Artery Bypass Graft (CABG), balloon mistiming of inflation and deflation, balloon timing usage within open-heart surgery and finally a balloon position and sizing.
This work describes seam welding process using dissimilar ferrous metals by pulsed Nd:YAG. The main objective of this work is to achieve the best welding conditions. This imposes careful selection for the welding parameters and inevitably the well design of experiment (DOE). Sheets of ASTM A240/316L stainless steel to ASTM A570/Gr30 carbon steel all of 0.5 mm in thickness were lap welded. Different pulse energies or the related peak power, pulse duration, pulse repetition rate, and welding speeds were used. Moreover, different welding speeds were controlled by the employed manipulator. The laser beam spot diameter and the standoff distance were fixed. Experimental results are supported by the computational 2D and 3D models. In this article response surface methodology (RSM) was applied to design the experiment and obtain the best parameters through a set of mathematical models that define the weld characteristics. The results show that the best joint in term of joint strength is obtained at 31.9 J pulse energy (related to 5.5 kW peak power and 5.8 ms pulse duration), power density of 1.43×106 W/cm2, 1.5 Hz pulse repetition rate, and 0.5 mm/s welding speed.
This study aims to review flow-induced vibration one of the repercussions of vibrations is caused by fluid movement. In general, the investigation of the structure of the systems affects the efficiency of the components that construct those systems. This review examined the influence of generated vibrations and internal pressure on fluid transport pipes using theoretical calculations, practical tests, and numerical analysis to identify and test the dynamic behavior of static fluid transport pipes. The experimental study considered the natural frequencies caused by the fluid pressure effect under various stability situations. The flow of all liquids, such as oil, water, gas, air, and vapors, through the pipes, was tested, and the mathematical models were correctly adjusted. All empirical, theoretical, numerical, and analytical research agrees that several approaches exist to develop, modify, and improve these metrics. However, one factor affecting rheological measurements is vibration, which was addressed as needed in the middle of the 20th century due to major discoveries that damage could be rooted in vibration. Established on the determinations, they provided mathematical models paired with pressure and velocity measurements of moving fluids and the influence of produced or uninduced vibration. This study demonstrates that additional empirical investigations, particularly more detailed analytical methodologies, are urgently required to produce better findings.
In this research, we investigate the nonlinear vibration of functionally graded carbon nanotubes (FG-CNTs) for simply supported sandwich cylindrical panels. The sandwich consisting of three layers formed of (FG-CNTs) and isotropic material as (CNT, ALMINUME, CNT). Mechanical properties of the sandwich media are acquired according to a re?ned rule of blend approach. The governing equations were derived using a first-order deformation theory (FOSDT). Four kinds of carbon nanotubes of sandwich cylindrical panels were analyzed. The volume fraction of CNTs is varied. The properties of nonlinear responses and free vibration are studied. The numerical approach employs the fourth-order Runge-Kutta and Galerkine procedure. Which conducted for the dynamic analysis of the panels to present the natural frequencies and non-linear dynamic response expression. The results show that; the natural frequencies and the nonlinear vibration amplitude decrease with the volume fraction and thickness ratio increase. The nonlinear vibration amplitude response increases when increasing the excitation force. The initial imperfection and the elastic foundation have a minor impact on the nonlinear vibration response of the panel. The Pasternak Foundation has a larger impact than the Winkler foundation. The structure formed of FG-CNT present an excellent choice for high-performance of engineering applications.
The composite opened web steel joist supported floor systems have been common for many years. It is economic and has light weight and can embed the electrical conduit, ductwork and piping, eliminating the need for these to pass under the member, consequently eliminate the height between floors. In order to study the joist strength capacity under the various conditions, it had been fabricated seven joists composed of the steel and concrete slab connected to the top chord by shear connectors (headed studs). These joist have 2820 mm length c/c of the supports and 235 mm overall depth. In the present study, six variable parameters are adopted (Studs distribution, Degree of shear connection, Degree of the web inclination, Shape of the web, Density of concrete for slab and length of the shear connector). The test results exhibited that minimum strength capacity was 160kN for light weight joist and maximum capacity was 225kN for joist of long shear connectors at failure. The results were compared by ultimate flexural model by Azmi.
In Urban cities, services are supported by intelligent applications and are connected to each other through ad hoc networks. Any service can be operated using a compatible of an Internet of Things (IoT) technology. This study focuses on the transportation service and finding a non-cost solution to solve the crossroads congestion that affected people time and money. The Wireless Sensor Networks (WSNs) that are planted on the roads can help in monitoring the roads situation by collecting their data and send them through wireless communication to a traffic management center. In this work two phases of time are considered for a crowded area. Low-cost components are suggested to solve the congestion at the cross roads without the need for reconstruct the roads. IoT device such as smart phone can be wirelessly connected to the Traffic Management Center (TMC), which can analyze the incoming data from WSN and send back the calculated time to the police officer to control the green light long and overcome the standard time installed for all directions. The main idea is to solve the congestion problem in real time by extending the time long of the green traffic light for the road direction with the highest vehicle density. The suggested algorithm was operated on a dataset of 6 days and for the time phase from 7:00-10:00am.
Shallow foundation suffers from considerable settlement, displacement and tilting under earthquakes. This is particularly due to the shaking associated with earthquakes that lead to the generation of horizontal seismic load transferred through the soil to the foundation. Also, liquefaction could take place during the earthquake in the saturated loose sand. To alleviate the detrimental effect of earthquakes, ground improvement is required. This study examines the response of the shallow square foundation rested on loose sand soil reinforced with geogrid reinforcement when subjected to 2023 Turkey earthquake by using a shaking table system. Different number of geogrid layers are installed; (one, two, three and four), also various geogrid configurations were examined which are (straight, trapezoidal and reverse trapezoidal). The acceleration response, settlement, horizontal displacement, rotation and pore water pressure developed in the sand soil and the shallow foundation during 2023 Turkey earthquake has been examined. The settlement and the horizontal displacement, foundation rotation, acceleration and pore water pressure were measured using rope displacement transducers, tilt sensors, accelerometers and pore water transducers respectively. The results showed that the acceleration amplifies when passing through loose sand. The results also indicated that the shallow foundation experienced noticeable settlement, horizontal displacement and rotation when subjected to the seismic loads. On the other hand, the installation of geogrid proved to be effective in controlling the problems associated with earthquakes. The optimum geogrid reinforcement is occurred when three layers of geogrid placed in reverse trapezoidal configuration (3RT) since it gave the best reduction in the acceleration amplification and the highest decrease in the foundation settlement, displacement and tilting which is about (60-66) %. Nevertheless, the effectiveness of geogrid minimizes when the sand soil becomes saturated. In addition, liquefaction occurs during earthquakes especially at the shallower depths because of the decrease in the shear strength of saturated soil.
Flexible and rigid pavements are commonly built for airport pavements to support the moving loads of aircraft during the pavement design life. Airport pavements represent a cornerstone of the aviation world. Their condition profoundly impacts safety, operational efficiency, airport capacity, and financial well-being. These meticulously engineered surfaces must withstand the immense stresses generated by aircraft during takeoff, landing, and taxiing. At the planning stage, the pavement structure, materials, aircraft loads, environmental conditions, and pavement damage models should be evaluated. Comparing with road pavement design, airport pavement structural design is unique in terms of the traffic loads supported by pavements with high load magnitude, significant tire pressure, and dynamic traffic conditions. Over time, deterioration stemming from environmental exposure, aircraft loading, and other factors becomes inevitable. This study aims to explore the various factors influencing airport pavement performance, review the existing methodologies for pavement design and maintenance, and propose enhancements to current practices to ensure long-term durability and safety of airport pavements. This study aims to explore the various factors influencing airport pavement performance, review the existing methodologies for pavement design and maintenance, and propose enhancements to current practices to ensure long-term durability and safety of airport pavements.
This paper presents a numerical investigation to study the effect of variations in displacement history sequence and magnitude on cyclic response of RC tapered (haunched) beams (RCHBs).Five simply supported RCHBs (four haunched and one prismatic) were selected from experimental work carried out by Aranda et al. The selected variables included were five loading history types. The first part of this study focused to verify the finite element analysis with selected experimental work and the second part of this study focused too studying the effect of varying in loading history to the response of RCHBs. The finite element code Abaqus was used in the modeling. The adopted cyclic simulation performance of the selected beams using the plastic- damage model for concrete developed by Lubliner and Lee & Fenves. The constitutive model of plain concrete describing the uniaxial compression response under cyclic loading proposed by Thorenfeldt, and the uniaxial tension response follows the softening law proposed by Hordijk was used in the modeling. Menegotto-Pinto model was used to simulate the steel response. Model verification has shown A good agreement to the selected experimental work. The variations in loading history will decrease the ultimate load and corresponding deflection with increase in the number of cycles at ultimate load.