2010
17
1
1
0
http://scientiairanica.sharif.edu/3138.html
Preloaded HighTemperature Constitutive Models and Relationships for Concrete
2
2
The behavior of concrete structures that are exposed to extreme thermomechanical loading
is an issue of great importance in nuclear engineering. The structural resafety capacity of concrete
is very complicated because concrete materials have considerable variations. Constitutive models and
relationships for preloaded Normal and High Strength Concrete (NSC and HSC) subjected to re are
needed, which are intended to provide ecient modeling and to specify the reperformance criteria
of the behavior of preloaded concrete structures exposed to re. In this paper, formulations for
estimating the parameters aecting the behavior of unconned preloaded concrete at high temperatures
are proposed. These formulations include residual compression strength, initial modulus of elasticity,
peak strain, thermal strain, transient creep strain and the compressive stressstrain relationship at elevated
temperatures. The proposed constitutive models and relationships are veried with available experimental
data and existing models. The proposed models and relationships are general and rational, and have good
agreement with the experimental data. More tests are needed to further verify and improve the proposed
constitutive models and relationships.
2
The behavior of concrete structures that are exposed to extreme thermomechanical loading
is an issue of great importance in nuclear engineering. The structural resafety capacity of concrete
is very complicated because concrete materials have considerable variations. Constitutive models and
relationships for preloaded Normal and High Strength Concrete (NSC and HSC) subjected to re are
needed, which are intended to provide ecient modeling and to specify the reperformance criteria
of the behavior of preloaded concrete structures exposed to re. In this paper, formulations for
estimating the parameters aecting the behavior of unconned preloaded concrete at high temperatures
are proposed. These formulations include residual compression strength, initial modulus of elasticity,
peak strain, thermal strain, transient creep strain and the compressive stressstrain relationship at elevated
temperatures. The proposed constitutive models and relationships are veried with available experimental
data and existing models. The proposed models and relationships are general and rational, and have good
agreement with the experimental data. More tests are needed to further verify and improve the proposed
constitutive models and relationships.
Keywords: Preloaded concrete; Constitutive models and relationships; Normal and high strength
concrete; Fire; High temperature.
0
0


M.
Bastami
Department of Civil Engineering,University of Kurdistan
Iran
swncuzje@scientiaunknown.non


F.
Aslani
Department of Civil Engineering,University of Kurdistan
Iran
wigvjoai@scientiaunknown.non
Preloaded concrete
Constitutive models and relationships
Normal and high strength concrete
Fire
High temperature
http://scientiairanica.sharif.edu/3139.html
Characteristics of Second Generation Endurance Time Acceleration Functions
2
2
The Endurance Time (ET) method is a timehistory based dynamic pushover procedure
in which structures are subjected to specially designed, intensifying accelerograms, and their seismic
performance is judged based on the time duration needed to satisfy the required design objective. Second
generation refers to ET acceleration functions that are generated by application of optimization techniques
in order to produce response spectra compliant linearly intensifying accelerograms. In this paper, the major
characteristics of a set of second generation ET acceleration functions (ETA20a013) are investigated.
The template response spectra of this set of ET acceleration functions corresponds to the design spectra
of the Iranian National Building Code (Standard 2800) for sti soil (type II). Results show that a good
correspondence can be established between the eective ground motion parameters of earthquakes and ET
acceleration functions at specic target times. Therefore, it is expected that ET acceleration functions can
be used to predict various demand parameters of structures subjected to ground motions whose response
spectra is more or less compatible with the adopted template response spectra. Discrepancies between
characteristics of ET acceleration functions and ground motions have also been discussed.
2
The Endurance Time (ET) method is a timehistory based dynamic pushover procedure
in which structures are subjected to specially designed, intensifying accelerograms, and their seismic
performance is judged based on the time duration needed to satisfy the required design objective. Second
generation refers to ET acceleration functions that are generated by application of optimization techniques
in order to produce response spectra compliant linearly intensifying accelerograms. In this paper, the major
characteristics of a set of second generation ET acceleration functions (ETA20a013) are investigated.
The template response spectra of this set of ET acceleration functions corresponds to the design spectra
of the Iranian National Building Code (Standard 2800) for sti soil (type II). Results show that a good
correspondence can be established between the eective ground motion parameters of earthquakes and ET
acceleration functions at specic target times. Therefore, it is expected that ET acceleration functions can
be used to predict various demand parameters of structures subjected to ground motions whose response
spectra is more or less compatible with the adopted template response spectra. Discrepancies between
characteristics of ET acceleration functions and ground motions have also been discussed.
Keywords: Dynamic pushover; Intensifying acceleration functions; Endurance time method.
0
0


H.E.
Estekanchi
Department of Civil Engineering,Sharif University of Technology
Iran
email@email.com


A.
Vafai
Department of Civil Engineering,Sharif University of Technology
Iran
osapjweb@scientiaunknown.non


V.
Valamanesh
Department of Civil Engineering,Sharif University of Technology
Iran
avduqbtj@scientiaunknown.non
Dynamic pushover
Intensifying acceleration functions
Endurance Time method
http://scientiairanica.sharif.edu/3140.html
Experimental and Numerical Behavior of Shallow Foundations on Sand Reinforced with Geogrid and Grid Anchor Under Cyclic Loading
2
2
There are many cases where the foundations of structures are subjected to cyclic loading
in addition to static loading. Oil reservoir foundations with frequent discharges and lling or road
embankments under repeatable trac loads are examples of such foundations. Although the amplitudes
of the cyclic load is usually less than the permissible static load, the concern still exists for the amount
of uniform and non uniform settlement of such structures. The soil under such foundations may be
reinforced with geosynthetics to improve their engineering properties. This paper deals with the eects
of using the new generation of reinforcements, gridanchor, for the purpose of reducing the permanent
settlement of these foundations under the in
uence of dierent proportions of the ultimate load. Other
items, such as the type and number of reinforcements, as well as the number of loading cycles, are studied
experimentally. In all cases, the foundation is rst under the in
uence of a xed static load equal to
the weight of the structure itself and, then, the cyclic load in dierent proportions of the ultimate load is
applied to it. The results show that by using gridanchor and increasing the number of their layers in the
same proportion as that of the cyclic load applied, the amounts of permanent settlements are reduced and
the numbers of loading cycles to reach it are decreased. For comparison with the experimental ndings,
similar to the conditions of the tests conducted, numerical models were made using a 3D nite element
software. The numerical results showed good agreement with the test results.
2
There are many cases where the foundations of structures are subjected to cyclic loading
in addition to static loading. Oil reservoir foundations with frequent discharges and lling or road
embankments under repeatable trac loads are examples of such foundations. Although the amplitudes
of the cyclic load is usually less than the permissible static load, the concern still exists for the amount
of uniform and non uniform settlement of such structures. The soil under such foundations may be
reinforced with geosynthetics to improve their engineering properties. This paper deals with the eects
of using the new generation of reinforcements, gridanchor, for the purpose of reducing the permanent
settlement of these foundations under the in
uence of dierent proportions of the ultimate load. Other
items, such as the type and number of reinforcements, as well as the number of loading cycles, are studied
experimentally. In all cases, the foundation is rst under the in
uence of a xed static load equal to
the weight of the structure itself and, then, the cyclic load in dierent proportions of the ultimate load is
applied to it. The results show that by using gridanchor and increasing the number of their layers in the
same proportion as that of the cyclic load applied, the amounts of permanent settlements are reduced and
the numbers of loading cycles to reach it are decreased. For comparison with the experimental ndings,
similar to the conditions of the tests conducted, numerical models were made using a 3D nite element
software. The numerical results showed good agreement with the test results.
Keywords: Reinforced soil; Shallow footing; Cyclic loading; Gridanchor; Geogrid.
0
0


N.
Hataf
Department of Civil Engineering,Shiraz University
Iran
nhataf@shirazu.ac.ir


A. H.
Boushehrian
Department of Civil Engineering,Shiraz University
Iran
ahajiani@gmail.com


A.
Ghahramani
Department of Civil Engineering,Shiraz University
Iran
aghahrama@shirazu.ac.ir
reinforced soil
Shallow footing
cyclic loading
gridanchor
geogrid
http://scientiairanica.sharif.edu/3141.html
Seismic Risk Analysis of Iranian Construction Projects
2
2
In this paper, the project earthquake occurrence risk coecient is determined for each
construction project that is located in one of Iran's twenty seismic regions. This coecient is allocated,
regardless of the current situation of the project, being in the plan or execution phase or even completed.
This coecient indicates the possibility of an earthquake occurrence during a project's life time. To nd
this coecient, the GutenbergRichter linear relationship has been applied, in conjunction with the Poisson
distribution. The GutenbergRichter linear equation expresses the relationship between the magnitude of
an earthquake and the number of occurrences, during a xed time, of that magnitude. To nd the linear
relationship for a series of earthquakes with dierent magnitudes occurring in the same seismic region,
the Ordinary Least Square (OLS) has been used. Two linear regression assumption violations, which
are variance heteroscedasticity and autocorrelation, have been tested on the available data. In the case
of nding one or both of these two violations, The Generalized Least Square (GLS) has been applied to
produce a better regression line. Moreover, the second order type of the GutenbergRichter relationship has
also been determined to validate the linear one. In conclusion, by application of the Poisson distribution
and by having the design earthquake's magnitude and project life time, the third parameter, which is the
design earthquake occurrence risk, can be determined for a given construction project in a specic location
in Iran.
2
In this paper, the project earthquake occurrence risk coecient is determined for each
construction project that is located in one of Iran's twenty seismic regions. This coecient is allocated,
regardless of the current situation of the project, being in the plan or execution phase or even completed.
This coecient indicates the possibility of an earthquake occurrence during a project's life time. To nd
this coecient, the GutenbergRichter linear relationship has been applied, in conjunction with the Poisson
distribution. The GutenbergRichter linear equation expresses the relationship between the magnitude of
an earthquake and the number of occurrences, during a xed time, of that magnitude. To nd the linear
relationship for a series of earthquakes with dierent magnitudes occurring in the same seismic region,
the Ordinary Least Square (OLS) has been used. Two linear regression assumption violations, which
are variance heteroscedasticity and autocorrelation, have been tested on the available data. In the case
of nding one or both of these two violations, The Generalized Least Square (GLS) has been applied to
produce a better regression line. Moreover, the second order type of the GutenbergRichter relationship has
also been determined to validate the linear one. In conclusion, by application of the Poisson distribution
and by having the design earthquake's magnitude and project life time, the third parameter, which is the
design earthquake occurrence risk, can be determined for a given construction project in a specic location
in Iran.
Keywords: Earthquake risk analysis; Construction management; Project management; Risk management;
OLS, GLS;
0
0


A.
Bakhshiani
Department of Engineering,University of Tehran
Iran
imjvpwyo@scientiaunknown.non


M.
Mofid
Department of Civil Engineering,Sharif University of Technology
Iran
mofid@sharif.edu


M.
ShokriGhasabeh
Department of Engineering,University of South Australia
Iran
sdytovvd@scientiaunknown.non


K.
Hansen
Department of Mechanical Engineering,University of Adelaide
Iran
yyuzgnma@scientiaunknown.non
Earthquake risk analysis
Construction Management
project management
Risk Management
OLS, GLS
http://scientiairanica.sharif.edu/3142.html
Optimization of SemiActive Control of Seismically Excited Buildings Using Genetic Algorithms
2
2
In this paper, the performance of semiactive viscous dampers in reducing the response
of tall buildings to earthquake acceleration is optimized using genetic algorithms. Torsional effects due
to irregularities exist in the building and due to unsymmetrical placement of the dampers are taken into
account through 3D modeling of the building. For the numerical example, a twelvestory building is
chosen. The building is modeled as a 3D frame. The equations of motion of the building with semiactive
viscous dampers, subjected to earthquake acceleration, is written, resolved in state space and the results
are compared with those of the uncontrolled building. Moreover, in order to minimize building responses
such as top story displacement and base shear, the required number and location of dampers are optimized
using genetic algorithms.
2
In this paper, the performance of semiactive viscous dampers in reducing the response
of tall buildings to earthquake acceleration is optimized using genetic algorithms. Torsional effects due
to irregularities exist in the building and due to unsymmetrical placement of the dampers are taken into
account through 3D modeling of the building. For the numerical example, a twelvestory building is
chosen. The building is modeled as a 3D frame. The equations of motion of the building with semiactive
viscous dampers, subjected to earthquake acceleration, is written, resolved in state space and the results
are compared with those of the uncontrolled building. Moreover, in order to minimize building responses
such as top story displacement and base shear, the required number and location of dampers are optimized
using genetic algorithms.
Keywords: Optimization; Genetic algorithms; Fluid viscous damper; Semiactive control
0
0


S.
Pourzeynali
Department of Civil Engineering,Guilan University
Iran
pourzeynali@guilan.ac.ir


T.
Mousanejad
Department of Civil Engineering,Guilan University
Iran
mcpoxxni@scientiaunknown.non
optimization
genetic algorithms
Fluid viscous damper
Semiactive control
http://scientiairanica.sharif.edu/3143.html
Comparison of the Cosserat Continuum Approach with Finite Element Interface Models in a Simulation of Layered Materials
2
2
This paper compares the formulation of the nite element Cosserat smeared approach with
the combined nite elementexplicit interface element approach, when both applied to the analysis of layered
continua. The fundamental equations of both formulations are presented. Also, using three examples, the
nature and accuracy of the displacement eld predicted by both techniques are investigated and discussed.
2
This paper compares the formulation of the nite element Cosserat smeared approach with
the combined nite elementexplicit interface element approach, when both applied to the analysis of layered
continua. The fundamental equations of both formulations are presented. Also, using three examples, the
nature and accuracy of the displacement eld predicted by both techniques are investigated and discussed.
Keywords: Cosserat theory; Layered continuum; Internal characteristic length; Transversely isotropic;
Interface element; Finite element method.
0
0


A.
Riahi
Department of Civil Engineering,University of Toronto
Iran
qnwsrpxi@scientiaunknown.non


J.H.
Curran
Department of Civil Engineering,University of Toronto
Iran
oavmodew@scientiaunknown.non
Cosserat theory
Layered continuum
Internal characteristic length
Transversely isotropic
Interface element
Finite Element Method
http://scientiairanica.sharif.edu/3144.html
Improving Mechanical Properties of High Strength Concrete by Magnetic Water Technology
2
2
The most important challenge for concrete technologists is to improve the properties of
concrete. In the last two decades, in Russia and China, a new technology, called magnetic water
technology, has been used in the concrete industry. In this technology, by passing water through a magnetic
eld, some of its physical properties change and, as a result of such changes, the number of molecules
in the water cluster decrease from 13 to 5 or 6, which causes a decrease in the water surface tension.
Using magnetized water in concrete mixtures causes an improvement in the workability and compressive
strength of concrete. Also, this processed water causes a reduction in the cement content required for the
specied compressive strength value. In this research, in the concrete laboratory of Sahand University of
Technology, the eects of magnetic water on some mechanical properties of high strength concrete, such as
workability and compressive strength, have been studied. For the production of magnetic water, a magnetic
treatment device (made in Germany) has been used. This device mostly is used for the softening of water
and, for the rst time in this research, it has been used by the authors for the production of concrete.
The results of tests showed that, in most cases, concrete made with magnetic water (magnetic concrete),
has higher slump values than those of control concrete (up to 45%). Also in some cases, the compressive
strength of the magnetic concrete samples was higher than that of the control concrete samples (up to
18%). Also, in some cases, with the same slump and compressive strength, cement content can be reduced
by 28% in the case of magnetic concrete.
2
The most important challenge for concrete technologists is to improve the properties of
concrete. In the last two decades, in Russia and China, a new technology, called magnetic water
technology, has been used in the concrete industry. In this technology, by passing water through a magnetic
eld, some of its physical properties change and, as a result of such changes, the number of molecules
in the water cluster decrease from 13 to 5 or 6, which causes a decrease in the water surface tension.
Using magnetized water in concrete mixtures causes an improvement in the workability and compressive
strength of concrete. Also, this processed water causes a reduction in the cement content required for the
specied compressive strength value. In this research, in the concrete laboratory of Sahand University of
Technology, the eects of magnetic water on some mechanical properties of high strength concrete, such as
workability and compressive strength, have been studied. For the production of magnetic water, a magnetic
treatment device (made in Germany) has been used. This device mostly is used for the softening of water
and, for the rst time in this research, it has been used by the authors for the production of concrete.
The results of tests showed that, in most cases, concrete made with magnetic water (magnetic concrete),
has higher slump values than those of control concrete (up to 45%). Also in some cases, the compressive
strength of the magnetic concrete samples was higher than that of the control concrete samples (up to
18%). Also, in some cases, with the same slump and compressive strength, cement content can be reduced
by 28% in the case of magnetic concrete.
Keywords: High strength concrete; Magnetic water; Compressive strength; Slump; Clean concre
0
0


H.
Afshin
Department of Civil Engineering,Shiraz University
Iran
sqfyielj@scientiaunknown.non


M.
Gholizadeh
Department of Chemistry,Sabzevar Tarbiat moallem University
Iran
m_gholizadeh@sttu.ac.ir


N.
Khorshidi
Department of Chemistry,Sabzevar Tarbiat moallem University
Iran
alwkwfks@scientiaunknown.non
High strength concrete
Magnetic water
compressive strength
Slump
Clean concre