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Sadeghi J.m., Youldashkhan M.,
Volume 3, Issue 1 (March 2005)
Abstract

In this paper, the main factors in the analysis of the railway concrete sleepers areinvestigated and new recommendations are made in order to improve the accuracy of the currentpractices in analysis of the railway track system. First, a comprehensive literature survey isconducted, then, FEM models for a railway track system are developed and used to discuss andevaluate the assumptions commonly used in the analysis of the railway track system. The analysisfactors investigated include stress distribution under a concrete sleeper, rail-seat load, anddynamic coefficient factor. Finally, recommendations and needs for continuation of the researchare presented.
B. ZahabiYoun,
Volume 4, Issue 1 (March 2006)
Abstract

A methodology is presented for the stochastic generation of daily rainfall which accounts for changes to the climatic inputs. The focus of the study is an example catchment in Iran. The methodology addresses the inability of GCMs to provide suitable future scenarios for the time and space scales required for a water resource impact assessment for a small catchment. One stochastic model for rainfall (Neyman-Scott Rectangular Pulses, NSRP, model) is used to generate daily rainfall sequences and then validated using historic records. For present climate conditions, the NSRP model is fitted to observed rainfall statistics. GCM outputs are then downscaled using regressions between atmospheric circulation indices (ACIs) and rainfall statistics. The relationships are then used to predict the rainfall statistics for future conditions using GCM outputs. In this respect, climate change impacts are studied and assessed in this paper. Generated rainfall scenario can then be used as inputs to a rainfall-runoff model in order to generate daily streamflow data which is not investigated here.
M.h. Sebt, A. Yousefzadeh, M. Tehranizadeh,
Volume 9, Issue 1 (March 2011)
Abstract

In this paper, the optimal location and characteristics of TADAS dampers in moment resisting steel structures, considering the application of minimum number of TADAS dampers in a building as an objective function and the restriction for destruction of main members is studied. Genetic algorithm in first generation randomly produces different chromosomes representing unique TADAS dampers distributions in structure and the structure corresponding to each chromosome is time history analyzed. Then the damage index for each member and the average weighted damage index for all members are determined. Genetic algorithm evaluates the fitness of each chromosome then selection and crossover as logical operators and mutation as random operator effect the current generation's chromosomes according to their fitness and new chromosomes are generated. Accordingly, successive generations are reproduced in the same way until the convergence condition is fulfilled in final generation and four distributions are suggested as better options. Since these proposed distributions are selected under the one earthquake, therefore, it is better that the four new structures are cost-benefit analyzed in different earthquakes. Finally, the optimal placement for dampers is compared and selected based on a benefit to cost ratio, drift stories and the number of different TADAS types of such structures. The increase in amount of energy dissipated via dampers located in different floors as well as the status of plastic hinges in main members of the structure strengthened with optimum option are the proof of the optimal placement and suitable characteristics for dampers.


Prof. T.h. Kim, Mr. S.h. You,
Volume 13, Issue 2 (Transaction B: Geotechnical Engineering June 2015)
Abstract

The ground improvement using Plastic Board Drain (PBD) in soft soil was undertaken by sand mat formation, PBD installation, preloading surcharge, and removal of surcharge. During this procedure, the sand mat formation induced an initial settlement. However, it was very difficult to estimate that settlement due to PBD installation, which frequently destroyed the instruments installed in the ground. Consequently, the initial settlement was not properly included in total settlement. In this study, the initial settlement was estimated using ground level measurement and cone penetration test. Both predicted almost the same amount of initial settlement. The initial settlement is linearly increased with the depth of the sand mat. The degree of consolidation and the time of surcharge removal were estimated using the settlement included the initial settlement. Correct estimation of initial settlement is very important because it is a critical factor, which affects total settlement and the time of surcharge removal. If the initial settlement is not considered, the preloading surcharge may be overloaded or the time of surcharge removal may be predicted incorrectly. Consequently, the prediction of settlement, which requires to management of construction procedure of the project, may be wrong
Yeon Yeu, Youngseok Kim, Dongwook Kim,
Volume 14, Issue 7 (Transaction B: Geotechnical Engineering 2016)
Abstract

Pile penetration and rebound amount measurements during pile driving are important in analysis of penetration and bearing characteristics of piles and for assurance of pile installation quality. Traditional manual measurement of penetration and rebound of piles exposes engineers under unfavorable environment of injury risk and significant vibration and noise. To improve accuracy of pile penetration and rebound measurements and to ensure safety of engineers during pile driving, the close-range photogrammetry approach was implemented. For the track of three-dimensional spatial information of one point on the pile during driving, a series of stereo pair images of the point attached on a pile is required using more than two camera systems at different locations. In this study, two charge coupled device cameras were used to obtain stereo images. Robust measurements and reliable results can be guaranteed by the constrained geometry of close-range photogrammetry. From the field implementation, it was found that the newly developed pile penetration and rebound measurement system is accurate and safe.


Muhammad Yousaf, Zahid Ahmed Siddiqi, Muhammad Burhan Sharif, Asad Ullah Qazi,
Volume 15, Issue 4 (Transaction A: Civil Engineering 2017)
Abstract

In this study, a comparison is made between force and displacement controlled non-linear FE analyses for an RC beam in flexure with partially developed steel bars. An FE model with slightly unsymmetrical reinforcement was analyzed by applying two-point loading using both force and displacement controlled methods. The responses obtained using ANSYS-13 were validated against available experimental data. Combined comparative display of flexural response of the beam using force and displacement controlled analysis, that has least been addressed in the literature, is given here. Study choses large-deformation-nonlinear plastic analysis scheme, discrete modeling approach for material modeling and program-chosen incremental scheme following Newton-Raphson method. The results show that displacement controlled approach is efficient in terms of time saving and less disk space requirement along with the ability to give falling branch of load-deflection response, if element displacement capacity still exists. Moreover, it gives an early estimate of the load carrying capacity of the structural element along with suitable values of convergence and non-linear solution parameters. However, for a beam with unsymmetrical detailing, force controlled analysis method seems to yield more realistic and practical results in terms of mid span deflection and beam cracking behavior compared with assumed symmetric displacement controlled technique. It also gives true fracture prediction at ultimate load level, which is not true for the displacement controlled method as the computer code forces the model to maintain equal displacements at two load points, falsely increasing the capacity of the beam.


Dr. Dan Koo, Dr. Younghan Younghan Jung, Mr. Urso Campos,
Volume 15, Issue 5 (Transaction A: Civil Engineering 2017)
Abstract

Roadway striping is a major operation and maintenance (O&M) task that must be performed to maintain safe vehicular traffic on roadways, which require re-striping or new striping every few seasons depending on the degree of deterioration due to weathering, abrasion, and damage during snow removal. Performance is normally assessed using manually collected data such as working hours, material consumption, and approximate striping distance achieved during a striping season, but the performance analysis methods currently used do not provide a clear holistic picture and are insufficient to permit an in-depth analysis. In order to address this deficiency, this study utilized telematics technology to automatically collect data that could then be used to improve striping performance without the need for additional staff or equipment. This paper presents the telematics data collection and implementation in two areas: 1) providing performance analyses using telematics data and 2) developing performance metrics for future performance measurement. As a result of the study, performance analyses revealed there was sufficient room for improvement and several recommendations were made. Performance metrics were provided using Monte Carlo and triangular distribution.


Younes Aminpour, Javad Farhoudi,
Volume 15, Issue 5 (Transaction A: Civil Engineering 2017)
Abstract

Local scour downstream of hydraulic structures is one of the critical phenomena which has absorbed a vast amount of interests by researchers. The designers of hydraulic structures, particularly, spillways try to utilize proper means to minimize the consequences of excess energies downstream of such structures which usually tend the erosion at their immediate downstream reaches. The stepped spillway is designed to create a large amount of energy dissipation by means of steps and would decrease the amount of scour evolution at its downstream. This article presents the results of 67 experiments conducted at two different scales of stepped spillways, to study the local scour downstream the structure. The experiments were planned to consider a wide range of geometrical factors, flow characteristics, and sediment properties. The time length of experiments was ranged from 6 to 24 hours which produced more than 80000 data points for analytical considerations. The results were used to render a regression equation to define the similarity among the scour hole profiles. It was observed that, a long term observation would be needed to reach the equilibrium state. However, semi-equilibrium conditions will be achieved after 24 hours. It was also noted that the depth of scour hole adjacent to channel walls was bigger than that at centerline. 



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