Asian Transactions on Engineering
Volume: 05, Issue: 03, June 2015
Title: Investigation of Energy Dissipation in Stepped Spillway with Semicircular Steps Treads
Author(s): Ali Mohsen Hayder, Muthanna Sadiq Jafar
Paper ID: ATE-15070319
Pages: 1 - 5
Abstract: The construction of spillway with steps represents an efficient technique to decrease the energy of water that flows over it. Steps shape, or geometry of the spillway, has a significant effect on the residual energy at the toe of the spillway. In this study, a traditional stepped spillway model designed with six steps of 5cm height, 5cm length, and 30cm width. The stepped spillway model modified twice by curving the horizontal treads using sectors of PVC pipe with 7.5cm diameter. The first modification done by curving the treads up to make convex treads with height of 1.1cm and the second modification was done by curving the treads down to make-concaved treads with depth of 1.1cm. Eleven tests carried out for the three cases with flow rates varied from 0.64l/s to 24.95l/s. The experimental results showed that the discharge affected reversely on the energy dissipation, and the concaved treads case produced higher dissipation than the horizontal and the convex cases. The energy dissipation for concaved treads case ranged from 48.84 to 87.82%, 41.38 to 84.08% for convex treads case and 34.93 to 78.23% for horizontal treads case. In addition, the total energy dissipation produced by the spillway and hydraulic jump together, for concaved treads case ranged from 62.51 to 94.38%, convex treads case from 60.74 to 93.81%, and horizontal treads from 59.64 to 93.25%. The other relation that noted were the decrease of Froude number at the toe, with the increase of flow rate, and concaved treads case produced lower values of Fr than the other two cases. In addition, the values of y2/y1, conjugate depths of the hydraulic jump, decreased with the increase of flow rates, and concaved treads case produced lower values of y2/y1 than the other two cases.
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Title: Strengthening of Reinforced Concrete Columns by Steel Jacketing: A State of Review
Author(s): N. Islam, M. M. Hoque
Paper ID: ATE-15130371
Pages: 6 - 14
Abstract: This paper aims to review the strengthening techniques of Reinforced Concrete (RC) column using steel jacket. Steel jacket usually consists of steel plates or angles and batten plates/strips with different configurations. Both experimental and analytical investigations conducted by researchers have been reviewed. Most of the investigations were focused to know the effect of strengthening configurations on load carrying capacity, ductility, lateral strength and flexural strength by changing parameters like strip thickness, size and spacing, concrete strength, angle size and thickness. Comparisons between the results of the experimental investigation and analytical equations proposed by different researchers and design codes have been illustrated. It has been found from the literature that load carrying capacity depends on aforementioned parameters. The experimental investigations conducted by several researchers reveal that the overall increase in axial strength ranges from 18.65% to 109% and that of lateral strength from 63% to 68%.
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Title: ATP Analysis of Transient Process during Direct Lightning Strike to the Telecommunication Tower
Author(s): Xhemali Pejtemalli, Piro Cipo, Aldi Muçka
Paper ID: ATE-15090371
Pages: 15 - 23
Abstract: For the wireless antenna industry, lightning protection has become even more necessary as a growing number of sophisticated electronic equipment is mounted on towers, which are more susceptible to direct strikes. A direct lightning strike to the telecomunication tower can cause dangerous overvoltages, which can result in malfunction of the sensitive equipment as well as dangerous step and touch voltages. Over voltages and over currents arising in 60 m of telecommunication tower during direct lightning strike on the top of the tower. The simulation of the electromagnetic transient process, caused from the lightning stroke on the upper most part of the telecommunication tower, has been carried out over the usage of the ATP Draw (Alternative Transient Program) software tool. ATP Draw , is a graphical, mouse-driven preprocessor to the ATP version of the Electromagnetic Transients Program (EMTP) on the MS-Windows platform . The Alternative Transients Program (ATP) is considered to be one of the most widely used universal program system for digital simulation of transient phenomena of electromagnetic as well as electromechanical nature in electric power systems. The key focus of the study has been the assessment of the tower behavior under the effect of the different lightning sources. In consideration of the propagation phenomenon of lightning current, each conducting branch of the multi conductor system of the tower, is subdivided into a suitable number of segments. The length of each segment is assumed to be less than or equal to one-tenth of the minimum of wavelength corresponding to the maximum frequency likely to affect the system transient. A distributed parameters line model is employed, with Heidler's type surge current source representing direct lightning strike to the telecommunication tower. The mathematical model elaborated for the ATP Draw characterized by loss lines with distributed constant parameter, which is based on the single phase Clark’s model. The inductance, capacitance and characteristic impedance of the segment model have been calculated using average potential method and programmed in Matlab code. The impact of the equivalent grounding resistance has been considered through the adoption of the model that implies constant resistance. The usage of three impulsive standard sources has been implemented, respectively: 1,2/50[ µs]; 8/20 [µs] and 10/350[ µs].
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Title: Radial Consolidation Analysis by the Steepest Slopes Observed in the δt - log t and δt - √t Curves
Author(s): Mohammed Shukri Al-Zoubi
Paper ID: ATE-15160219
Pages: 24 - 28
Abstract: The steepest slopes method for radial consolidation is proposed herein for estimating the coefficient of radial consolidation cr, which is directly related to the ratio of the steepest slopes observed in the compression-log time (δt - log t) and in the compression-root time (δt - √t) curves. The proposed method involves only the identification of two straight lines with steepest slopes and compute without the need to identify the initial or secondary compression. Accordingly, the proposed method does not require a complete record of compression - time data; few data points at middle of primary consolidation range are adequate to estimate cr particularly in the case of field conditions. Because the proposed method computes cr in the middle of primary consolidation range, the computed cr is least affected by the initial and secondary compressions. Experimental results of radial consolidation tests are used to validate the proposed method by comparison with existing methods and by matching experimental compression - time data with the theory.
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