Periodica Polytechnica (Budapest University of Technology and Economics)
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The Impact of Natural Fibers on Thermal Resistance and Spalling in High-performance Concrete
Get PDFThis article presents an experimental approach to evaluate the effectiveness of palm fibers as a natural innovative solution to enhance the thermal resistance of high-performance concrete (HPC) under fire conditions. The utilization of palm fibers aims to promote local materials, since locally sourced materials may be more affordable due to their abundance. Four different high-performance concrete formulations were tested. The first, called HPCSF, which is composed of fibreless silica fumes, served as a reference mix. The second, HPCPSF, included the addition of polypropylene fibers to silica fume. The third, HPCDFSF, integrates date palm fibers with silica fume. Finally, the fourth, HPCPQSSF, combined polypropylene fibers with varying amounts of quarry sand and silica sand, in addition to silica fume. The results of the fire resistance tests show that the incorporation of palm fibers into the concrete mixture improves structural strength, reduces spalling, prevents crack formation under high-temperature conditions, and increases fire resistance in HPC
Integrated Design Optimization Process for Building Projects
Get PDFIn this study, a cost-design optimization is conducted for a reinforced concrete structure with irregular voids and inclined axes, which is a real-world application. Data transfers are performed on a 3D model to achieve the optimization. Data exchange is managed automatically by the created software program. As an application example, a hospital building with 10 beds is considered. Optimum design and minimum cost values are obtained for optimization processes using the Rao algorithms. The construction cost values are compared both among algorithms and with actual cost values, indicating a successful optimization process. The software program developed in this study accelerates the processes in optimization operations, thereby contributing to the realization of automatic data transfers
Effect of Microwave Curing on the Performance of High-volume Fly Ash Concrete
Get PDFConcrete curing significantly impacts mechanical properties and durability, yet traditional methods face efficiency challenges. Microwave curing (MC) offers a promising alternative, providing rapid and uniform concrete curing. However, fully understanding the impact of MC on concrete performance, particularly in high-volume fly ash concrete (HVFC), remains a research gap. This study addresses this gap by investigating the effect of MC on key properties of HVFC, including compressive strength, drying shrinkage, chloride ion penetration, and resistance to sulfate attack. Concrete specimens underwent MC at varied energies (200–1000 W) and durations (10–30 min) to evaluate their mechanical and durability characteristics. Results show that MC significantly boosts early-stage concrete strength, notably at high applied energy. The specimen cured at 1000 W for 30 min (MC1000-30) achieved the highest 1-day strength of 23.68 MPa. However, the normal curing specimen exhibited the highest strength of 32.07 MPa at 28 days while the strength value of the MC1000-30 specimen declined to 20.25 MPa, indicating a 36.85% decrease. Although declining strength was observed after 28 days, the MC1000-30 specimen demonstrated improved durability with significantly reduced drying shrinkage (by 83.12%) and chloride ion penetration (by 31.6%). The study underscores the feasibility of utilizing MC for HVFC as it demonstrated significant enhancements in both early-stage concrete strength and durability at a later stage. Careful parameter optimization can ensure sustained effectiveness over time, offering a viable alternative to traditional curing methods
New Short-Circuited Coaxial Method Implementation for Complex Permittivity Measurement of Power Transformer Oils
Get PDFThe investigation into the dielectric properties of transformer oils has been a focal point in both historical and contemporary electric insulation technology as high-voltage applications have greatly benefited from the continuous research efforts in this field. The dielectric permittivity is one of the factors to be negotiated when discussing the electric insulation of any material. This work aims to showcase a new short-circuited coaxial cable method to evaluate the complex dielectric permittivity of palm, sunflower and rapeseed oil and review other previously used measurement techniques. Mainly, the test was performed using a sample holder that represents a short-ended coaxial cable filled with the test material which is connected to one port of a vector network analyser. The measurements of the input impedance for various oil samples were conducted at frequencies ranging from 1 MHz to 10 MHz. The technique uses the value of the input impedance which depends on the reflected signals from the test sample to the network analyser, consequently, the value of the dielectric permittivity and dielectric loss have been calculated using the short circuit impedance formula which involves numerical methods to get the results which shows that this method can be used as an alternative to investigate the oils insulation parameters as it provides smooth results for permittivity without any divergence, ensuring more reliable and consistent measurements as well as providing high accuracy in determining the permittivity of materials
Vibration Analysis of Damaged Viscoelastic Composite Sandwich Plate
Get PDFThis paper presents a study of free and forced vibration of composite sandwich plate with and without damage using the finite element analysis developed under ANSYS APDL software. This modeling uses the 8-node shell 281 element to modelized the composite laminates of the top and bottom face sheets of the sandwich plate and the 20-node higher order solid 186 element to modelized the viscoelastic core. Two sets of boundaries are considered; Simply supported and clamped boundary conditions at all edges. The effect of damaged face sheets layers on natural frequencies, mode shapes, the frequency and transient responses of the sandwich plate is investigated. Numerical results show remarkable shifts of the natural frequencies, frequency and transient responses due to the presence of damage. It is concluded that the natural frequencies decreasing is due to the loss of structural stiffness. Natural frequencies of the sandwich plates are close to those issued from numerical results available in the literature
Numerical Investigation on Influence of Grooves on Tube Hydroforming Process of Aluminium Alloys
Get PDFFor several decades, scientists and engineers have been using the tube hydroforming (THF) process for numerous applications in the automotive and aerospace industries. The inert advantages like weight reduction without compromising on strength, improved part quality, better surface finish, and reduced tooling costs have motivated the use of THF in the fabrication industry. The presence of grooves on the pre-forms was found to immensely help in increasing the pressure-withstanding capacity of the THF tubes, in addition to reducing the stress concentration and achieving the near-net shape during the THF process. This project involves the development of a detailed Finite Element Model, for the THF process. Numerical analysis is carried out in two stages: Stage-1: Groove Formation, and Stage-2: Final THF tube formation. In Stage 1, the numerical model investigates the formation of grooves, predicting the amount of internal pressure and axial feeding that are required to accurately form them. In Stage 2, numerical simulations focus on the actual THF process. This two-stage THF process (Grooved-THF) was compared to a single-stage Generic THF process. The results indicate the Grooved-THF to be producing a relatively lower thickness reduction with a more closely formed corner radius compared to the generic case. The work also involves multi-objective optimization of the process parameters like the number of grooves, coefficient of friction, internal fluid pressure, and die corner radius using the DOE technique – RSM. The results indicate the number of grooves and the friction coefficient to be the most influencing parameters in the THF process
Corrigendum
Get PDFViktor Józsa, Dávid Csemány "Evaporation of Renewable Fuels in a Lean Premixed Prevaporized Burner", 60(2), pp. 82–88, 2016. (in this issue)https://doi.org/10.3311/PPme.8564When the above article was first published online Fig. 2 was incorrect. This has now been corrected in the online version. The correct version of Fig. 2 is published here
Active Displacement Control of Pantograph-catenary System for a Half-body Railway Model
Get PDFThe pantograph is an essential component that provides electrical contact between the overhead wires and the electric train. The quality of the current collection in high-speed trains is directly influenced by the mechanical interaction between the pantograph collector head and the overhead contact line. To overcome these challenges and improve pantograph performance, researchers and engineers have explored innovative solutions, including the introduction of active control mechanisms. Excitation by the vehicle is one of the normal disturbances in the dynamic interaction of the pantograph and the overhead line. The vertical effects of vehicle-track vibrations on the interaction between the pantograph and the overhead contact line have not yet been adequately researched. To fill this research gap, this study establishes models for both the pantograph-catenary interaction and the vehicle-track system. In this study, the performance of the modified Skyhook-Proportional-Integral-Derivative (PID) controller was investigated for a half-body of a railway pantograph-catenary system. Track irregularities such as step, sine, and random were applied to perturb the suspension system. The performance of both passive and active systems was investigated by considering the track irregularities as a basis. The root mean square analysis (RMS) found that active displacement control of pantograph-catenary systems for a half-body railway model equipped with modified Skyhook-PID controllers performed better than the passive systems. In summary, the future experimental approach for active half-body railway model could incorporate this simple modification of the Skyhook-PID controller
Investigating the Preference on Public Transport in a Metropolitan Area of Lampung Province, Indonesia
Get PDFMetropolitan areas grow and develop as the region's population grows and travels to meet needs such as education, work, family matters, and business. Kotabumi and Bandar Lampung are two of the regions that have grown faster in recent years as a result of the construction of the trans-Sumatera toll road, while railway has been operating for more than two decades. The main objective of this works is to explore preference towards public transport with service quality attributes. The minibus mode or "travel" in Indonesia is defined as transportation services that pick up passengers. This study surveyed 384 commuters who used three modes of transportation: rail, bus, and minibus with relatively different service characteristics and trip purposes of school/college (35%), leisure (28%), family affairs (19%), work (14%), and business (4%) and represented predominantly an age range of 17 to 55 years (97%). The rail mode's utility value was 4.383, while the bus and minibus modes' utility values were 3.751 and 3.737, respectively. Because utility value reflects the level of user satisfaction with the overall attributes and service quality, the rail mode has a much higher probability of being chosen by respondents, with a probability level of 48.65%, compared to the bus and minibus modes, which have a probability level of 25.86% and 25.49%, respectively
The Feasibility and Operational Performance of Implementation Median U-turn Intersections: A CRITIC Method
Get PDFCurrently, a growing number of cities are adopting the Median-U-Turn (MUT) intersection design to enhance road capacity and traffic efficiency. The critical question in selecting the right intersection design is how significantly the implementation of MUT can enhance intersection performance, focusing on three key aspects: intersection efficiency, capacity, and the environmental impact of the design. To address this question, an evaluation of operational performance under various prevailing conditions (roadway and control) was conducted using VISSIM, a microscopic simulation platform. This evaluation involved five scenarios: conventional intersections (with increased cycle length, grade separation with a signalized at-grade intersection, grade separation with a roundabout), MUT, and signalized crossover MUT at a dense urban arterial intersection in Amman, Jordan's capital. The performance was compared using several metrics: average control delay, number of stops, average travel speed and time, average stopped delay, Carbon Monoxide (CO) emissions, fuel consumption, and vehicle safety. The Criteria Importance Through Intercriteria Correlation (CRITIC) technique was subsequently used to select the optimal design. The findings indicate that the existing intersection configuration is the least effective, while the MUT with signals at the crossing U-turn points is the most efficient solution