eng
Materials and Energy Research Center
International Journal of Engineering
1025-2495
1735-9244
1998-08-01
11
3
121
134
71205
Effect of Impressed Current on Bond Strength Between Steel Rebar and Concrete
R. Dehghanian
dehghani@cc.iut.ac.ir
1
Elecrtical and Computer Enginnering, Isfahan University of Technology
The deterioration of bond strength between reinforcing steel and concrete as a result of impressed cathodic current with respect to the exposure time was investigated. A current in the magnitude of 3ma/ft2 (based on reinforcing rebar area) was used for a period of five years. Chemical analyses for sodium (Na+), potassium (K+) and chloride (Cl-) ions in concrete cylinders were performed as a function of time and distance from the rebar. Bond strength and chemical analyses for cylinders exposed to the current flow were compared to those determined for the cylinders with no impressed current (control). After forty two months of experiment, it was found that the impressed current had weakened the bond between the rebar and concrete significantly. This weakening in some cases was a factor of two lower compared to the control cylinders of the same age. The concentration of sodium and potassium ions near the rebar for the test cylinders increased with exposure time to current. The chloride ions migrated toward the concrete surface as expected. The decrease in bond strength was probably due to the accumulation of sodium ions near the rebar. It is well known that high sodium concentration will attack the portland cement matrix. These results indicate that there should be some concern about the long term effects of cathodic protection for reinforcing concrete structures.
https://www.ije.ir/article_71205_f7feac9a9b754b970053647d427a0e78.pdf
Concrete
Cathodic Protection
Rebar
Bond Strength Exposure Time
Sodium Ion
potassium ion
Chloride ion
migration
eng
Materials and Energy Research Center
International Journal of Engineering
1025-2495
1735-9244
1998-08-01
11
3
135
146
71206
Traffic Flow Characteristics of Isolated Off-ramps in Iranian Expressways
M. Vaziri
manouchehrvaziri@yahoo.com
1
Civil Engineering, Sharif University of Technology
The purpose of this study was to investigate traffic flow characteristics at off-ramp junctions in Iranian expressways. The study was conducted on the traffic behavior in isolated off-ramp vicinity of 6-lane expressways. The database consisted of traffic flow and traffic speed information extracted from videotapes. The relationship between diverging traffic flow in the right lane of expressway with total expressway and ramp flows was investigated. The 1985 U.S. Highway Capacity Manual, the 1985 HCM, models, and numerical values for isolated off-ramp analysis were evaluated and modifications for Iranian expressway system were suggested. The speed -flow relationship study showed that for a developing country such as Iran, the developed country's transportation engineering and planning manuals such as the 1985 HCM could give misleading results. Highway capacity analysis should be adjusted for a developing country's prevailing traffic composition and driver behavior.
https://www.ije.ir/article_71206_0e9fd21dd7a5024b15497b16d1bbc2ed.pdf
Transportation engineering
Traffic Flow Characteristics
Highway Capacity Analysis
Ramp Junction
eng
Materials and Energy Research Center
International Journal of Engineering
1025-2495
1735-9244
1998-08-01
11
3
147
156
71207
Some Issues in Implementation of a Voltage Stability Analysis Function in an Energy Management System Environment
K. Imhof
hasnomail@ije.ir
1
H. Seifi
seifi_ho@modares.ac.ir
2
, ATEL AG
Electerical Engineering, Tarbiat Modarres University
Over the last few years, the problem of voltage stability has received a lot of attraction from the power system community. This type of stability is now a major concern for utilities in both planning and operating conditions. Both static and dynamic aspects of the problem have been discussed and investigated by the researchers. The present paper concentrates on a Voltage Stability Analysis function as integrated into an Energy Management System (EMS) environment. In order to provide an optimal user interface, the function is integrated into the contingency analysis function. Key issues such as the integration approach, the voltage dependency of load characteristics, the choice of current point distance to critical point in terms of either MVAr, MW or MVA as well as a fast screening approach for finding the most potential unstable load nodes in an EMS are reviewed. The function has been implemented at the customer's NOK, Baden Switzerland-site in an on-line environment. Initial results are promising.
https://www.ije.ir/article_71207_94d5edd1b20e36b5558e179f50dea45a.pdf
Voltage stability
Voltage Collapse
Power system stability
energy management system
Power System Dynamics
eng
Materials and Energy Research Center
International Journal of Engineering
1025-2495
1735-9244
1998-08-01
11
3
157
166
71208
Turbulent Flow over Cars
A. R. Azimian
azimian@cc.iut.ac.ir
1
, Isfahan University of Technology
In this paper the flow behaviour over a number of car bodies is studied. For this purpose the unsteady 2-D incompressible Navier-Stokes equations have been applied. After averaging and nondimensionalizing the equations, the system of equations has been transformed from the Cartesian (x-y) coordinates to a body fitted generalized (-) coordinate. As the flow is incompressible, the density in the continuity equation will disappear and thus the coupling between the continuity and the momentum equations will be lost. To resume the missing coupling between the aforementioned equations an artificial state equation is introduced. This artificial state equation will couple the continuity and the momentum equations via pressure. For turbulence simulation Jones & Launders Low Reynolds turbulence model was employed. By means of an implicit method, the system of five equations are solved. From the flow field solution, the drag force on car geometries are predicted and the results are compared to the drag force calculated from experimental correlations. Agreement is fare enough i.e. within 90 percent of accuracy.
https://www.ije.ir/article_71208_f57e54170f56304ba3bde802931cda24.pdf
Turbulent Flow
Car Bodies
Navier
stokes Equations
Drag force
Artificial State Equation
eng
Materials and Energy Research Center
International Journal of Engineering
1025-2495
1735-9244
1998-08-01
11
3
167
174
71209
The Influence of Urban Network Features on the Quality of Traffic Service (RESEARCH NOTE)
B. Amini
hasnomail@ije.ir
1
J. Shahi
jalil@iust.ac.ir
2
Civil Engineering, Iran University of Science & Technology
Civil Engineering, Iran University of Science & Technology
The work reported here presents a methodology based on a two-fluid model to assess the degree of influence of various geometric and control features of an urban network on the quality of traffic service. The two-fluid model gives a curvilinear relation between the trip time and stop time per unit distance and its parameters characterize the quality of traffic service in urban networks. Any Change in geometric and control features of a network would alter these parameters and the relationships permit the engineer to predict and evaluate traffic impacts of a given modification in advance.
https://www.ije.ir/article_71209_bcd83ef174ec38641aa49c01549a37d5.pdf
urban network
Two
Fluid Model
Traffic Service
Auto
Restricted Zone
eng
Materials and Energy Research Center
International Journal of Engineering
1025-2495
1735-9244
1998-08-01
11
3
175
179
71210
The Effect to Epsilon Phase on the Friction and Wear of Nitrided Die Steels (RESEARCH NOTE)
X. Du
hasnomail@ije.ir
1
Z. Zhang
zhuzhang@eller.arizona.edu
2
Z. Zheng
3
X. Tong
iaohuitong@sohu.com
4
, Beijing Machinery and Electricity Institute Co Ltd (BMEI)
, Beijing Machinery and Electricity Institute Co Ltd (BMEI)
, Beijing Machinery and Electricity Institute Co Ltd (BMEI)
In this paper, the wear resistance and antifriction of epsilon phase layer and diffusion layer of gas nitrided D2 steel and M2 steel have been studied. The changes m wear mechanism of epsilon phase under the load from 20N to 200N are analysed. When the load is lighter than 100N, it is mainly oxidizing wear on friction surface. The adhesion, peeling off and abrasive wear appear on friction surface while the load is heavier than 150N. The epsilon phase on nitrided D2 steel surface can reduce oxidizing wear and adhesion, and delay abrasive wear. The friction coefficient of D2 steel can be reduced by 19%, and the wear resistance can be increased 200% to 300% by the epsilon phase layer on nitrided surface.
https://www.ije.ir/article_71210_4efdfc0733531cc2a79bb2a3dde01bca.pdf
Die Steel
Nitriding
Wear
Antifriction