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Showing 28 results for Modeling

Nassiri H., Khayat Khoie A.,
Volume 3, Issue 3 (9-2005)
Abstract

This paper studies the effects of queue formation in the bottlenecks at off-ramps on the capacity of the freeways. Six expressway exit-ramps throughout the city of Tehran, Iran were selected and their traffic flows were observed in thirty-minute intervals during which the queue formation and queue elimination occurred. Assuming that in the absence of the queue, the traffic flow is in its normal state, the changes in the volume of through vehicles has been modeled as an average estimator of the change in the expressway capacity.The developed models prove that the changes in freeway capacity are due to queue formation at the off-ramp sections. However, the estimated figures are different from those obtained from the theory of freeway capacity. The conclusion is that lane blockage is only one of many factors that affect the freeway capacity while the queue forms. Since it is not possible to quantify all those factors individually, the resulting models are macroscopic estimates of the phenomenon.
Sassan Eshghi, Khashaiar Pourazin,
Volume 7, Issue 1 (3-2009)
Abstract

Confined masonry buildings are used in rural and urban areas of Iran. They performed almost satisfactory

during past moderate earthquakes of Iran. There is not a methodology in Iranian Seismic Code (Standard 2800-3rd

edition) to estimate their capacities quantitatively. In line with removing this constraint, an attempt is made to study

in-plane behavior of two squared confined masonry walls with and without opening by using a numerical approach.

These walls are considered based on Iranian Seismic Code requirements. Finite element 2D models of the walls are

developed and a pushover analysis is carried out. To model the non-linear behavior of the confined masonry walls, the

following criteria are used: (1) The Rankine-Hill yield criterion with low orthotropic factor to model the masonry

panel (2) The Rankine yield criterion to model reinforced concrete bond-beams and tie-columns (3) The Coulomb

friction criterion with tension cutoff mode to model the interface zone between the masonry panel and reinforced

concrete members. For this purpose, the unknown parameters are determined by testing of masonry and concrete

samples and by finite element analysis. Comparing the results show that the initial stiffness, the maximum lateral

strength and the ductility factor of walls with and without opening are different. Also, the severe compressed zones of

the masonry panels within the confining elements are found different from what are reported for the masonry panels

of infilled frames by other researchers. This study shows that a further investigation is needed for estimating capacity

of confined masonry walls with and without opening analytically and experimentally. Also where openings, with

medium size are existed, the confining elements should be added around them. These issues can be considered in the

next revisions of Iranian Seismic Code.


M.h. Baziar, A. Ghorbani, R. Katzenbach,
Volume 7, Issue 3 (9-2009)
Abstract

The pile-raft foundation is a combination of a raft foundation with piles. Pile-raft foundation has been widely designed, assuming all structure loads to be transferred to piles without considering contribution of the load taken by contact surface between raft and soil. Methods of analysis currently used in practice are based upon relatively conservative assumptions of soil behavior or on the less realistic soil-structure interaction. In this study the bearing -settlement behavior of combined pile-raft foundations on medium dense sand was investigated. 1g physical model test was performed on a circular rigid raft underpinned with four model piles. Numerical simulation was also carried out on the model test, using FLAC-3D, to show compatibility of the numerical analysis with the test. The obtained results showed very good accuracy of the numerical method used in this study as long as the applied load does not exceed the working load, while the performance of numerical model was relatively good for the loads beyond working load.
M.a. Goudarzi, S.r. Sabbagh-Yazdi,
Volume 7, Issue 3 (9-2009)
Abstract

The main objective of this article is evaluation of the simplified models which have been developed for analysis and design of liquid storage tanks. The empirical formulas of these models for predicting Maximum Sloshing Wave Height (MSWH) are obtained from Mass Spring Models (MSM). A Finite Element Modeling (FEM) tool is used for investigating the behavior the some selected liquid storage tanks under available earthquake excitations. First, the results of FEM tool are verified by analyzing a liquid storage tank for which theoretical solution and experimental measurements are readily available. Then, numerical investigations are performed on three vertical, cylindrical tanks with different ratios of Height to Radius (H/R=2.6, 1.0 and 0.3). The behaviors of the tanks are initially evaluated using modal under some available earthquake excitations with various vibration frequency characteristics. The FEM results of modal analysis, in terms of natural periods of sloshing and impulsive modes period, are compared with those obtained from the simplified MSM formulas. Using the time history of utilized earthquake excitations, the results of response-history FEM analysis (including base shear force, global overturning moment and maximum wave height) are compared with those calculated using simplified MSM formulations. For most of the cases, the MSWH results computed from the time history FEM analysis demonstrate good agreements with the simplified MSM. However, the simplified MSM doesn’t always provide accurate results for conventionally constructed tanks. In some cases, up to 30%, 35% and 70% average differences between the results of FEM and corresponding MSM are calculated for the base shear force, overturning moment and MSWH, respectively.
A. R. Majidi, A.a. Mirghasemi, M. Arabshahi,
Volume 9, Issue 4 (12-2011)
Abstract

In the current study, an effort is made to determine three dimensional bearing capacity of rectangular foundations using Discrete

Element Method. The soil mass is modeled as discrete blocks connected with Winkler springs. Different factors affect the geometry

of failure surface. Six independent angles are used to define the failure surface. By trial and error, the optimum shape of failure

surface beneath the foundation can be found. The paper includes the derivation of the governing equations for this DEM based

formulation in three dimensional state as well as parametric sensitivity analyses and comparison with other methods. Moreover,

using the current method, bearing capacity coefficients are presented for various friction angles and foundation aspect ratios.


R. Mahin Roosta, A. Alizadeh,
Volume 10, Issue 2 (6-2012)
Abstract

In the first impounding of rockfill dams, additional settlements occur in upstream side in saturated rockfills due to collapse
phenomenon even high rainy seasons can cause additional deformation in the dumped rockfills. Unfortunately these
displacements are not taken into account in the conventional numerical models which are currently used to predict embankment
dam behavior during impounding. In this paper to estimate these displacements, strain hardening-strain softening model in Flac
is modified based on the laboratory tests, in which same impounding process in such dams is considered. Main feature of the
model is reproduction of nonlinear behavior of rockfill material via mobilized shear strength parameters and using collapse
coefficient to display induced settlement due to inundation. This mobilization of shear strength parameters associated with some
functions for dilatancy behavior of rockfill are used in a finite difference code for both dry and wet condition of material. Collapse
coefficient is defined as a stress dependent function to show stress release in the material owing to saturation. To demonstrate
how the model works, simulation of some large scale triaxial tests of rockfill material in Gotvand embankment dam is presented
and results are compared with those from laboratory tests, which are in good agreement. The technique could be used with any
suitable constitutive law in other coarse-grained material to identify collapse settlements due to saturation


A. A. Tasnimi, M. A. Rezazadeh,
Volume 10, Issue 3 (9-2012)
Abstract

The torsional capacity of unreinforced masonry brick buildings is generally inadequate to provide a stable seismic behavior. The

torsional strength is believed to be the most important parameter in earthquake resistance of masonry buildings and the shear

stresses induced in the bed joints of such building’s walls is an important key for design purposes. Brick buildings strengthened

with wire-mesh reinforced concrete overlay are used extensively for building rehabilitation in Iran. Their quick and simple

applications as well as good appearance are the main reasons for the widespread use of such strengthening technique. However,

little attention has been paid to torsional strengthening in terms of both experimental and numerical approach. This paper reports

the response and behavior of two single-story brick masonry buildings having a rigid two-way RC floor diaphragm. Both

specimens were tested under monotonic torsional moment.Numerical work was carried out using non-linear finite element

modeling. Good agreement in terms of torque–twist behavior, and crack patterns was achieved. The unique failure modes of the

specimens were modeled correctly as well. The results demonstrate the effectiveness of reinforced concrete overlay in enhancing

the torsional response of strengthened building. Having evaluated the verification of modeling, an unreinforced brick building

with wall-to-wall vulnerable connections was modeled so that the effect of these connections on torsional performance of brick

building could be studied. Then this building was strengthened with reinforced concrete overlay and the effect of strengthening

on torsional performance of brick buildings with vulnerable connections was predicted numerically.


Seyed B. Beheshti-Aval,
Volume 10, Issue 4 (12-2012)
Abstract

A comparison between design codes i.e. ACI and AISC-LRFD in evaluation of flexural strength of concrete filled steel tubular

columns (CFTs) is examined. For this purpose an analytical study on the response of CFTs under axial-flexural loading is carried

using three-dimensional finite elements with elasto-plastic model for concrete with cracking and crushing capability and elastoplastic

kinematic hardening model for steel. The accuracy of the model is verified against previous test results. The nonlinear

modeling of CFT columns shows that the minimum thickness that recommended by ACI and AISC-LRFD to prevent local buckling

before the steel shell yielding for CFT columns could be decreased. The comparison of analytical results and codes indicates that

the accuracy of ACI method in estimation of axial-flexural strength of CFT columns is more appropriate than AISC-LRFD. The

ACI lateral strength of CFTs is located on upper bond of the AISC-LRFD’s provisions. AISC-LRFD estimates the lateral strength

conservatively but ACI in some ranges such as in short columns or under high axial load levels computes lateral strength in nonconservative

manner. Supplementary provisions for post local buckling strength of CFT columns should be incorporated in high

seismic region. This effect would be pronounced for column with high aspect ratio and short columns.


J. S. Yi, C. W. Koo, S. H. Park, O. K. Kwon,
Volume 11, Issue 1 (3-2013)
Abstract

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.
F. Nasirzadeh, M. Khanzadi, A. Afshar, S. Howick,
Volume 11, Issue 1 (3-2013)
Abstract

This research presents a dynamic mathematical system for modeling and simulating the quality management process in construction projects. Through sets of cause and effect feedback loops, all factors that internally and externally affect the quality management process are addressed. The proposed system integrates fuzzy logic with system dynamics simulation scheme to consider the uncertainties associated with the model parameters and estimation of the extra cost and time due to quality defects. Quantification of the consequences of the quality failures is performed based on the α-cut representation of fuzzy numbers and interval analysis. The proposed approach is efficient in modeling and analyzing a quality management process which is complex and dynamic in nature and involves various uncertainties. The proposed approach is implemented in a real submarine water supply pipe line project in order to evaluate its applicability and performance. The negative impacts resulting from quality failures are simulated. These negative impacts are mitigated by the implementation of alternative solutions.
M. Mortazavi Zanjani, A. Soroush,
Volume 11, Issue 2 (11-2013)
Abstract

This paper presents results of a thorough study on the phenomenon of rupture propagation of reverse faults from the bedrock

foundation through homogeneous clayey embankments, mainly at the end of construction, with complementary analyses for the

steady state seepage through the embankment. The study is performed by means of numerical analyses with a nonlinear Finite

Element Method, verified beforehand through simulating fault propagations in an existing horizontal soil layer experiment.

Multiple cases considering three slopes & three clayey soils for the embankment and five fault dip angles, activated in several

locations of base of the embankment, are analyzed. The results show that ruptures in the embankment follow optimal paths to

reach the surface and their near-surface directions are predictable with respect to corresponding theories of classical soil

mechanics. Various types of rupture in the embankment are produced on the basis of the rupture types, the embankment base is

divided into three distinguishable zones, which can be used for interpretation of fault ruptures behavior. The effects of materials

and slope of the embankment, fault dip angle, and fault’s point of application in the bedrock-soil interface on the rupture paths

are studied in depth.


Y.y. Chang, C.j. Lee, W.c. Huang, W.j. Huang, M.l. Lin, W.y. Hung, Y. H. Lin,
Volume 11, Issue 2 (11-2013)
Abstract

This study presents a series of physical model tests and numerical simulations using PFC2D (both with a dip slip angle=60° and

a soil bed thickness of 0.2 m in model scale)at the acceleration conditions of 1g, 40g, and 80 g to model reverse faulting. The soil

deposits in prototype scale have thicknesses of 0.2 m, 8 m, and 16 m, respectively. This study also investigates the evolution of a

surface deformation profile and the propagation of subsurface rupture traces through overlying sand. This study proposes a

methodology for calibrating the micromechanical material parameters used in the numerical simulation based on the measured

surface settlements of the tested sand bed in the self-weight consolidation stage. The test results show that steeper surface slope

on the surface deformation profile, a wider shear band on the major faulting-induced distortion zone, and more faulting appeared

in the shallower depths in the 1-g reverse faulting model test than in the tests involving higher-g levels. The surface deformation

profile measured from the higher-g physical modeling and that calculated from numerical modeling show good agreement. The

width of the shear band obtained from the numerical simulation was slightly wider than that from the physical modeling at the

same g-levels and the position of the shear band moved an offset of 15 mm in model scale to the footwall compared with the results

of physical modeling.


H. Ghiassian, M. Jalili, I. Rahmani, Seyed M. M. Madani,
Volume 11, Issue 4 (12-2013)
Abstract

The concept of Geosynthetic Cellular Systems (GCS) has recently emerged as a new method in construction of breakwaters and coastal protective structures. The method potentially has significant advantages compared to conventional systems from the standpoint of constructability, cost effectiveness, and environmental considerations. This paper presents the results of physical model testing on the hydraulic responses of GCS structures under wave action. A series of model tests were carried out in a wave flume on GCS models with different shapes and soil types, subjected to various wave characteristics. Horizontal wave forces acting on the models were measured at different elevations. The maximum horizontal force in each test was calculated and compared with conventional formula of predicting wave pressure on breakwaters. The results show that Goda’s equation overestimates the hydrodynamic water pressure on these structures. This can be attributed to the influence of seeping water through the GCS models because of relative permeability of the GCS.
K. J. Tu, Y. W. Huang,
Volume 11, Issue 4 (12-2013)
Abstract

The decisions made in the planning phase of a building project greatly affect its future operation and maintenance (O&M) cost. Recognizing the O&M cost of condominiums’ common facilities as a critical issue for home owners, this research aims to develop an artificial neural network (ANN) O&M cost prediction model to assist developers and architects in effectively assessing the impacts of their decisions made in the planning phase of condominium projects on future O&M costs. A regression cost prediction model was also developed as a benchmark model for testing the predictive accuracy of the ANN model. Six critical building design attributes (building age, number of apartment units, number of floors, average sale price, total floor area, and common facility floor area) which are usually available in the project planning phase, were identified as the input factors to both models and average monthly O&M cost as the output factor. 55 of the 65 existing condominium properties randomly selected were treated as the training samples whose data were used to develop the ANN and regression models the other ten as the test samples to compare and verify the predictive performance of both models. The study results revealed that the ANN model delivers more accurate and reliable cost prediction results, with lower average absolute error around 7.2% and maximum absolute error around 16.7%, as compared with the regression model. This study shows that ANN is an effective method in predicting building O&M costs in the project planning phase. Keywords: Project management, Facility management, Common facilities, Cost modeling.
P. Ramadoss,
Volume 12, Issue 1 (3-2014)
Abstract

Abstract: This paper presents the influence of adding steel fibers and incorporation of silica fume on the mechanical properties of high-strength concrete. The variables investigated were steel fiber volume fraction (0 to 1.5%), silica fume replacement (5, 10 and 15%) and water-to-binder ratio (0.25, 0.30, 0.35 and 0.40). The influence of fiber content in terms of fiber reinforcing index on the compressive and splitting tensile strengths of high-strength steel fiber reinforce concrete (HSFRC) is presented. The use of silica fume increased both the compressive and splitting tensile strengths of concrete at 28 days. On the other hand, the addition of crimped steel fiber into high-strength concrete improves splitting tensile strength significantly. Based on the test data, using regression analysis, empirical expression to predict 28-day tensile strength of HSFRC in terms of fiber reinforcing index was developed and the absolute variation and integral absolute error (IAE) obtained was 3.1% and 3.3, respectively. The relationship between splitting tensile and compressive strength of SFRC was reported with regression coefficient (r) = 0.9. The experimental values of previous researchers were compared with the values predicted by the model and found to predict the values quite accurately.
M. Effati, M. A. Rajabi, F. Samadzadegan, Sh. Shabani,
Volume 12, Issue 3 (9-2014)
Abstract

Road transportation by way of automobiles is a very convenient means of transportation. Today, the most detrimental consequence of developing transportation systems in a country is traffic accident that places a huge financial burden on society. This paper investigates the role of information systems in transportation safety that leads to improved planning and operation of the transportation system through the application of new technologies. Current methods for identification of segments of roads with high potential of accident are based on statistical approaches. Since there are not accident records for newly built roads, these methods cannot be used for regional roads that are recently built. This paper presents a GIS based Neuro-Fuzzy modeling for identification of road hazardous zones. The results of proposed approach are compared with statistical methods. It is shown that this method is a cheaper but at the same time robust means of analyzing the level of hazard associated with each road segment under consideration, specially when data are uncertain and incomplete.
M. Zare, A. Eslami,
Volume 12, Issue 4 (12-2014)
Abstract

Physical modeling for study of deep foundations can be performed in simple chambers (1g), calibration chambers (CC),

and centrifuge apparatus (ng). These common apparatus face certain limitations and difficulties. Recently, Frustum Confining

Vessels (FCV) have been evolved for physical modeling of deep foundations and penetrometers. Shaped as the frustum of a

cone, this device applies steady pressure on its bottom and creates a linear stress distribution along its vertical central core.

This paper presents the key findings in FCV, as developed in AUT. The FCV has a height of 1200 mm, with top and bottom

diameters of 300 and 1300 mm, respectively. By applying bottom pressure up to 600 kPa, the in-situ overburden stress

conditions, equivalent up to 40 m soil deposits, become consistent with the embedment depth of commonly used piles.

Observations indicated that a linear trend of stress distribution exists, and this device can create overburden stress in the

desired control volume along the central core. Moreover, a couple of compressive and tensile load tests were performed on

steel model piles driven in sand with a length of 750 mm, and different length to diameter (L/D) ratios between 8-15.

Comparison between measured and predicted ultimate capacity of model piles performed in FCV demonstrate a suitable

conformity for similar confinement conditions in the field. Therefore, the FCV can be considered as an appropriate approach

for the investigation of piling geotechnical behavior, and the examination of construction effects.


A. Allahverdi, M. Mahinroosta,
Volume 12, Issue 4 (12-2014)
Abstract

It was found out that the logarithmic models fit the cement–slag blend systems well. In the present study, based on the experimental results, a logarithmic model has been developed to predict the compressive strength of chemically activated high phosphorous slag content cement. Mixes of phosphorous slag (80 wt.%), Portland cement (14 wt.%) and compound chemical activator (6 wt.%) were prepared at different Blaine finenesses using a laboratory ball mill. Compressive strengths of mortar specimens cured in lime-saturated water were measured at different curing times. Mathematical model was prepared in terms of curing time and water-to-cement ratio as independent variables and compressive strength as dependent variable. The comparisons between the model reproductions and the experimentally obtained results confirm the applicability of the presented model.
H. B. Ozmen, M. Inel, S. M. Senel, A. H. Kayhan,
Volume 13, Issue 1 (3-2015)
Abstract

Seismic performance and loss assessment studies for stock of buildings are generally based on representative models due to extremely large number of vulnerable buildings. The main problem is the proper reflection of the building stock characteristics well enough by limited number of representative models. This study aims to provide statistical information of structural parameters of Turkish building stock for proper modeling using a detailed inventory study including 475 low and mid-rise RC building with 40351 columns and 3128 beams for member properties. Thirty-five different parameters of existing low and mid-rise Turkish RC building stock are investigated. An example application is given to express use of given statistical information. The outcomes of the current study and previous studies are compared. The comparison shows that the previous studies have guidance for limited number of parameters while the current study provides considerably wide variety of structural and member parameters for proper modeling.
Mr. Mehdi Goorani, Dr. Amir Hamidi,
Volume 13, Issue 2 (6-2015)
Abstract

This paper presents a model for prediction of the mechanical behavior of sand-gravel mixtures using generalized plasticity and critical state concepts. Proposed model is based on the difference between critical state lines of sand and sand-gravel mixture in e-Lnp' plane. A generalized plasticity model is considered as the base model for sandy soil. Its state parameter, dilation rate and hardening function are modified to involve the effects of gravel particles on the behavior of mixture. Gravel content is considered as a physical parameter for determination of four new added parameters of the model. Verification of the proposed model performed considering four sets of experiments conducted by different researchers on poorly graded sand-gravel mixtures. According to the results, proposed model provides satisfactory qualitative and quantitative predictions of the behavior of sand-gravel mixture. Stress- strain behavior besides volumetric strains in drained condition and induced pore pressure during undrained loading are satisfactory predicted which indicates the possibility of its application in boundary value problems of geotechnical engineering.

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