Measuring the Abilities of Four Approximation
Approaches for Trusses Optimization
maged
mirzaee
tmu
author
gafar
rozagar
tmu
author
text
article
2011
per
There are a lot of approximation techniques for structural optimization. Among them, four
outstanding approximation methods have been selected for trusses optimization. These
approaches have been developed or modified by previous ones. Based on these schemes, a lot
of trusses have been optimized by author's program. This study shows that the abilities of the
mentioned methods are not the same and some of them have deficiencies. Reaching a better
solution, lesser analysis time, oscillation of response, numerical stability and also using a
variety of the design variables are among the findings of this work. A brief of these obtained
results has been given in the conclusion part.
Keywords: Nonlinear programming, Global optimum, Approximation methods, Convex
approximation, Structural analysis, Two and three dimensional trusses
Modares Civil Engineering journal
Tarbiat Modares University
2476-6763
10
v.
4
no.
2011
1
12
http://mcej.modares.ac.ir/article_1736_630c706d2bde6d34f21d023ee07b5215.pdf
Direct Calculation of Free Term Coefficients in
Displacement Boundary Integral Equations for 3-D
Isotropic Problems
babak
Omidvar
دانشگاه تهران
author
mohamad
Rahimian
author
taktom
mohamad nagad
author
ali
sanaeeha
author
text
article
2011
per
Abstract:
Direct calculation of free term coefficients for linear isotropic problems in three dimensional
displacement boundary integral equations is presented in details. In addition, the shape
functions of 9 node non-continuous and semi-continuous elements for modeling the crack
surfaces, layers interface, infinite boundary and other similar problems have been
demonstrated. This proposed method for calculating cij coefficients has been verified
comparing with some solved problems.
Modares Civil Engineering journal
Tarbiat Modares University
2476-6763
10
v.
4
no.
2011
13
24
http://mcej.modares.ac.ir/article_1737_a178e15a50ffce412f0481f0fd32dc77.pdf
Effect of Restraint in Plastic Shrinkage and Settlement of
Repair Materials Based on Self-consolidating Concrete
parviz
Goddossi1
دانشگاه علم و صنعت
author
ali
sherzadi
author
text
article
2011
per
Plastic shrinkage occurs in fresh concrete within few hours after mixing the concrete. When
the plastic concrete is allowed to shrink freely, it never cracks. But, generally, removal of
unsound material or damaged concrete is a part of repair operation. Thus usually the surface
of the substrate is rough, the repair concrete will be under restrained condition, which will
result in the development of tensile stresses in the plastic concrete and will create cracks on
the surface of the concrete. Four types of repair materials were used in this work: plane selfconsolidating
concrete (SSC), SCC containing silica fume (S.F.), SCC containing S.F. and
latex (Styrene Butadiene Rubber), and SCC containing S.F., latex and fiber. To roughen the
surface of the substrate base, dents with different degree, referring to restraint indices, RI,
were used to provide restraints. RI is defined as the ratio of the surface area dents to smooth
surface area of the slab. The panels were subjected to sever combination of wind, temperature
and relative humidity. The test program includes: settlement strains, free and restrained
shrinkage strains, evaporation and bleeding rates, and cracks characteristic measurements.
The results showed that, while the rate of evaporation and bleeding affected the shrinkage
properties, it was over shadowed by properties of the repair materials and restraints indices.
The results also indicated that, for a given repair concrete, the restrained strain increased as
the R.I. increased. A significant improve was observed for the SCC with latex and fiber,
exhibiting the lowest plastic settlement, shrinkage strains and crack area, and the highest time
to the first crack. The plane SCC exhibited almost two times of higher settlement and
shrinkage strains than the SCC with latex and fiber, for a given R
Modares Civil Engineering journal
Tarbiat Modares University
2476-6763
10
v.
4
no.
2011
25
32
http://mcej.modares.ac.ir/article_1738_355ab6227d65405ac1c35a80b96c5b09.pdf
Airport Ranking Based on the Efficiency and Level of
Services Using AHP Method
mahmod
saffarzada
author
shahab
hasan poor
author
amiraza
mamdohi
author
text
article
2011
per
Abstract:
One of the main reasons of weakness in airport system management and capacity
insufficiency of its various sections is the lack of detailed information or reliable assessments
of services of those sections of the airport. Proper airport management requires a thorough
understanding of the performance of the different components and the airport system, as a
whole. In this paper, a model of airport assessment and ranking is proposed after identifying
and classifying the factors influencing the efficiency and level of service of the various
sections of an airport based on the results of previous researches and a survey to gather the
opinion of the experts in this field. The importance of the above factors and their sub-factors
is determined using Analytical Hierarchy Process and the data gathered from the experts. The
results of this model can help to identify airport weaknesses and strengths per airport section,
make possible a quantitative comparison of airports and their ranks and also may be applied
to identify the potentials of the different sections of an airport system. The results indicated
that the efficiency factors (76.7%) are about three times more important than the level of
service factors (23.3%). Also the two most important factors are runways (26.11%) while
taxiways (9.6%) and the least important ones are baby changing stations (0.1%) and vending
machines (0.11%).
Modares Civil Engineering journal
Tarbiat Modares University
2476-6763
10
v.
4
no.
2011
33
46
http://mcej.modares.ac.ir/article_1739_40a7d9557292c72797ebf37aa812ea4d.pdf
Cyanide Removal From Contaminated Sediment of
Tailing Dam by Electrokinetic Technology
ahmad
khodadady
author
hosan
Ganjidoust
author
ezad
Bani Mostafa3
author
text
article
2011
per
There are known techniques for cyanide remediation from contaminated soil such as soil
washing, soil oxidation and biological degradation. However, there is very little research for
electrokinetic remediation of cyanide from soil.
This study investigates the application of electrokinetic remediation to contaminated soil with
high clay content and low coefficient of permeability. The experiments were conducted with
two electrodes as cathode and anode poles, which were placed inside the soil using the direct
electrical current. Thus cyanide ions were transported to the anode pole and caused the
remediation of the soil. The contaminated soil from tailing dam of Takab gold processing
plant was used. Contaminated soil with the concentration of 420 mg/kg, distilled water and
NaOH were employed in the electrokinetic cell.
The experiments were conducted on the optimum moisture content of clayed soil at two
voltage gradients (1.0 and 1.5 VDC/cm for the duration of 7 and 14 days) in order to assess
the effect of voltage gradient when employing 1M NaOH solutions and distilled water at the
anode pole. For each test, cyanide removal efficiency, the pH of the soil, moisture content,
electrical conductivity and the electrical current and flow were determined. The
measurements were conducted for the entire duration of electrokinetic experiments and at the
end of the test. The results indicated that the cyanide removal obtained in 7 and 14 days was
approximately 65% and 80%, respectively. The results also showed the pH of the soil was
changed from 8.83 to 1-2 for the anode and to 12-13 for the cathode pole. The cyanide
transported to the cathode and the pH were the most important dominant factors for cyanide
remediation.
Modares Civil Engineering journal
Tarbiat Modares University
2476-6763
10
v.
4
no.
2011
47
55
http://mcej.modares.ac.ir/article_1740_63ec6c0fe5c6cbd1050ca61bd8dcbe9e.pdf
Effect of Random Initial Crookedness of Members on
Reliability of Steel Frames
m.a
Lotfollahi-Yaghin
author
m.
Negin
author
text
article
2011
per
Abstract:
The effect of two types of common initial geometric imperfections on the reliability of steel
frames was investigated. These imperfections are the coordinates of connection nodes and
crookedness of members. Most of the finite element reliability analyses in the past
haveneglect this source of uncertainty. For this purpose, static non-linear pushover structural
analysis was used in the present work from which reliabilities were estimated based on the
FORM and Monte Carlo sampling methods. Furthermore, to investigate the importance of
uncertain parameters, reliability sensitivity analysis was performed by the use of direct
differentiation method, which was implemented in the object oriented framework of
OpenSees software. It was demonstrated that some of these geometric imperfections have
significant influence on the reliability assessment of steel frames.
Modares Civil Engineering journal
Tarbiat Modares University
2476-6763
10
v.
4
no.
2011
57
69
http://mcej.modares.ac.ir/article_1741_f5238980f21996428f4d98e190ee75f8.pdf
Strength Development and Absorption of High Strength
Concertes Incorporating Natural Pozzolan, Fly Ash and
Silica Fume
mahmod
nili
author
amir
Salehi
author
text
article
2011
per
Abstract:
The effects of natural pozzolan, fly ash and silica fume as cementitious materials on strength
development and absorption water capacity were investigated. Cubic specimens
(100×100×100 mm) from 13 mix designs with 2 water-cement ratios of 0.3 and 0.46 were
made. The specimens at the age of 28 days were dried and then immersed in water from 30
minutes to 7 days based on BS 1881, part 122, to study their cavity volume. The cement type
2 was replaced (by weight) with natural pozzolan and fly ash with 15, 30, 15 and 25 percent,
respectively. Furthermore, in 0.3 water cement ratio specimens, the cement was replaced with
silica fume at three percentages of 5, 8 and 11. It was concluded that natural pozzolan caused
the decrease of compressive strength at both the early and later ages. Fly ash also caused the
decrease of compressive strength at the early age, however, at the later age, it improved the
compressive strength. Silica fume improved the compressive strength from the second day to
the later ages. In 0.46 water cement ratio specimens, the absorption water capacity was
decreased when the cement replacement with natural pozzolan and fly ash was 15%. Silica
fume decreased the absorption water content when the immersion time was 7 days. In 0.3
water cement ratio specimens, the pozzolan materials had no considerable effect on the
absorption water capacity.
Modares Civil Engineering journal
Tarbiat Modares University
2476-6763
10
v.
4
no.
2011
71
82
http://mcej.modares.ac.ir/article_1742_5039c34529874d0334e3d44775a55d04.pdf
«Research Note»
A Review of Foundations Evaluation Using Seismic Codes
M
Soltani Mohammadi1
author
bahman
Ghiassi2
author
text
article
2011
per
Abstract:
The experience of last earthquakes has shown the vulnerability of most of structures. This has
been caused the speeding up of the seismic evaluation and retrofitting of projects in Iran. In
this regard, the instructions for seismic rehabilitation of the existing buildings have been
published and are currently beiong used in the evaluation and retrofitting projects. The
experience of retrofitting the structures in the past has shown that one of the most important
problems in Iran is seismic evaluation and retrofitting of the foundations. The evaluation
procedures are usually done such that they results in huge retrofitting plans for foundations
and this opinion has been raised that seismic evaluation and retrofitting of the structures is not
economical. This paper presents some suggestions for accurate seismic evaluation of
structural and geotechnical components of foundations. The results showed that by using the
correct relations and understanding the behavior of structure exactly, the retrofitting
procedure do not result in massive strengthening.
Modares Civil Engineering journal
Tarbiat Modares University
2476-6763
10
v.
4
no.
2011
http://mcej.modares.ac.ir/article_1743_83e617bf8e4b621b4b3bcae76b2ca6aa.pdf
«Research Note»
Vibration Control of High-rise Buildings with Tuned Mass
Dampers
(Case Study: Tehran International Tower)
m.r
Bemanian
author
m.r
Okhovat
author
H
Okhovat3
author
text
article
2011
per
Abstract:
Appealing to the principle of vertical residence and stemming the horizontal expansion of the
city, the Tehran Milad Tower is being built on 35000 sm3 site with the total area of 220000
sm3. With a height of over 170m, this 56-story concrete building is in the final stages of
construction and would be the highest residential building of Iran. Since Tehran is located in a
high-risk earthquake zone, all of its structures must be designed for seismic loads. In this
building, the lateral loads are carried with three main shear walls, which are located in an
angle of 120 degrees and the gravity loads are transferred from the concrete slabs to the
secondary shear walls.
Since the introduction of Tuned Mass Dampers (TMD) by Frahm in 1909, as a passive control
system, numerous investigations have been carried out to examine the effect of these devices
in reducing seismic response of the structures. The objective of incorporating a TMD into a
structures is to reduce the energy dissipation demand on the primary structural members
subjected to external forces. This reduction is accomplished by transferring some of the
structural vibration energy to the TMD and dissipating the energy at the damper of TMD.
The purpose of this paper is to design and evaluate the effectiveness of TMD for response
reduction of the Tehran tower under seismic excitations. A lumped mass model of the
building was provided with 112 translational and 56 rotational degrees of freedom using solid
and shell elements. Time history analyses were performed to calculate the response of the
structure subjected to some earthquake records. The same procedure was followed for the
models with attached TMD. The control effectiveness of TMD was evaluated by comparing
the tower's responses with those of the towers without control device. Furthermore, multiple
tuned mass dampers are suggested as a solution for insufficiency of TMD.
Modares Civil Engineering journal
Tarbiat Modares University
2476-6763
10
v.
4
no.
2011
http://mcej.modares.ac.ir/article_1744_cef5e0f1cf4b51ce043478f7d6b2b2d1.pdf
119
Abstract
«Research Note»
Measuring the Abilities of Four Approximation
Approaches for Trusses Optimization
M.
Rezaiee Pajand1
author
S.T.
Firoozi2
author
text
article
2011
per
There are a lot of approximation techniques for structural optimization. Among them, four
outstanding approximation methods have been selected for trusses optimization. These
approaches have been developed or modified by previous ones. Based on these schemes, a lot
of trusses have been optimized by author's program. This study shows that the abilities of the
mentioned methods are not the same and some of them have deficiencies. Reaching a better
solution, lesser analysis time, oscillation of response, numerical stability and also using a
variety of the design variables are among the findings of this work. A brief of these obtained
results has been given in the conclusion part.
Modares Civil Engineering journal
Tarbiat Modares University
2476-6763
10
v.
4
no.
2011
http://mcej.modares.ac.ir/article_1745_f0b3c7b01bcb232e97d814bc6db52e6d.pdf