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Showing 8 results for Koo

Soroush A., Koohi Sh.,
Volume 2, Issue 4 (December 2004)

Lateral spreading of liquefied saturated sandy deposits happens during and shortly afterearthquakes. This paper first reviews this phenomenon by means of reviewing and comparingobservations on case histories and experimental works. Based on the results from the review andcomparison, a mechanism for describing lateral spreading will be suggested. The Finn model,adopted in the Computer code FLAC is employed to carry out numerical analyses of lateralspreading of the Wildlife Site, happened during the 1987 Superstition Hills earthquake. First themodel is calibrated by means of numerical analysis of the first centrifuge model test of theVELACS Project. For the Wildlife site, three types of analysis are carried out: a) coupledliquefaction-consolidation analysis using the coefficient of permeability (K1) of the liquefiedlayers, as reported in the literature b) analysis type (a), but with K equal to 0.1K1, and c) a fullyundrained liquefaction analysis. The analyses results, in forms of excess pore water pressures andsurface displacements, indicated that the fully undrained behavior of the liquefied layers betterrepresents the behavior and response of the site during the earthquake.
B. Saghafian, A.r. ShoKoohi,
Volume 4, Issue 1 (March 2006)

Time–Area method is one of the most widely applied techniques of watershed routing, and can be potentially used as a distributed model. In this paper, a fundamental flaw in the arrangement of subareas in the original time-area histogram is identified for one-dimensional flow. This is conducted on the basis of comparing time-area hydrograph with that of the kinematic wave theorem. Accordingly, a revised time-area algorithm is developed as a substitute for the original time-area. It is proved that in the revised approach, subareas must be reversely arranged. It is also shown that the revised time-area hydrograph is in perfect agreement with the hydrograph derived by the kinematics wave theory.
A. R. ShoKoohi, B. Saghafian,
Volume 10, Issue 1 (March 2012)

In almost all of the present mathematical models, the upstream subbasins, with overland flow as the dominant type of flow, are

simulated as a rectangular plane. However, the converging plane is the closest shape to an actual upstream subbasin. The

intricate nature of the governing equations of the overland flow on a converging plane is the cause of prolonged absence of an

analytical or semi analytical solution to define the rising limb of the resulted hydrograph. In the present research, a new

geomorphologic semi analytical method was developed that tries to establish a relationship between the parallel and converging

flows to reduce the complexity of the equations. The proposed method uses the principals of the Time Area method modified to

apply the kinematic wave theory and then by applying a correction factor finds the actual discharge. The correction factor, which

is based on the proportion of the effective drained area to the analytically calculated one, introduces the convergence effect of

the flow in reducing the potentially available discharge in a parallel flow. The proposed method was applied to a case study and

the result was compared with that of Woolhiser's numerical method that showed the reliability of the new method.

R. Abbasnia, A. HolaKoo,
Volume 10, Issue 3 (September 2012)

One important application of fiber reinforced polymer (FRP) is to confine concrete as FRP jackets in seismic retrofit process

of reinforced concrete structures. Confinement can improve concrete properties such as compressive strength and ultimate axial

strain. For the safe and economic design of FRP jackets, the stress-strain behavior of FRP-confined concrete under monotonic

and cyclic compression needs to be properly understood and modeled. According to literature review, it has been realized that

although there are many studies on the monotonic compressive loading of FRP-confined concrete, only a few studies have been

conducted on the cyclic compressive loading. Therefore, this study is aimed at investigating the behavior of FRP-confined

concrete under cyclic compressive loading. A total of 18 cylindrical specimens of FRP-confined concretewere tested in uniaxial

compressive loading with different wrap thickness, and loading patterns. The results obtained from the tests are presented and

examined based on analysis of test results predictive equations for plastic strain and stress deterioration were derived. The

results are also compared with those from two current models,comparison revealed the lack of sufficient accuracy of the current

models to predict stress-strain behavior and accordingly some provisions should be incorporated.

J. S. Yi, C. W. Koo, S. H. Park, O. K. Kwon,
Volume 11, Issue 1 (TransactionA: Civil Engineering, March 2013)

Construction industry consists of several phases in which a variety of stakeholders are involved. As construction projects are becoming larger, more complex and more diverse, the design phase has been more important factor for the success of projects than ever before. However, it is considered that most of design work occurred in actual design process is intangible. Such recognition makes the design phase more unsystematic and arbitrary, which finally weakens the competitiveness of whole project. In order to solve these problems, this study developed a web-based system for integrated design management (IDMS) which consists of 8 modules including design document, schedule, quality, and building permit management. This section is intended to validate the system implementation and its effectiveness. Two characteristics have made this research significantly different from previous studies. First of all, users of the system including architects and other design professionals were continuously involved starting from the development phase to the validation phase. The other unique characteristic is that the actual design project was applied as a test bed in the final verification stage. The research team applied the actual data which had been generated while each business process, and verified the effectiveness of system implementation. The authors expect that such a user-centered approach enable the system more robust and effective.
Abdolreza S.moghadam, Masoud NeKooei, Ramin K.badri,
Volume 14, Issue 8 (Transaction A: Civil Engineering 2016)

This paper investigates the effect of different deteriorating hysteretic model parameters on the response of asymmetric buildings. The example buildings are 5-story symmetric and asymmetric buildings. The maximum interstory drift ratio over the height of building is selected as the structural response in this study. A proper hysteretic model is used to simulate the deterioration properties of structural elements. The median response of building with different mass eccentricities is evaluated by 3D modeling. The results are provided for both torsionally stiff and torsionally flexible buildings. The results show that the effect of deterioration parameters are different for flexible side and stiff side elements. Those effects are mainly significant for higher intensity levels. That intensity threshold level is independent of all hysteretic parameters except for the plastic rotation capacity.

Alireza Darvishpour, Ali Ghanbari, Seyyed Ali Asghar Hosseini, Masoud NeKooei,
Volume 15, Issue 3 (Transaction B: Geotechnical Engineering 2017)

Most of the proposed methods for obtaining the free vibration natural frequency of the retaining wall have been presented, assuming the behavior of the wall in two-dimensional domain, and they are not able to express the three-dimensional behavior of these structures in a satisfying manner. In this paper, the plate theory is employed to analyze the free vibration of wall-soil system in three-dimensional domain. So the retaining wall is modeled as a clamped-free plate and the stiffness of the soil existing behind the wall is modeled as a set of springs. Using the approximate Rayleigh method, new analytical expression for obtaining the free vibration natural frequencies for the three first modes of the wall is represented. The results of the proposed model are compared with both the results of the other researchers and the ones from finite element method (FEM). They are also compared with the results of a full-scale experiment and it shows a good agreement. The comparison shows that modeling the wall in two-dimensional form is not accurate enough to calculate all the natural frequencies of the wall. The results of this paper show that there is a considerable difference between two- and three-dimensional behavior of the walls. The proposed method also gives the free vibration natural frequencies of the wall extensional modes with an acceptable accuracy. Finally, the effect of tensile and compressive behavior of the soil on the fundamental frequency is studied. This research can be considered as a new field in three-dimensional calculation of the retaining walls.

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

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.

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