18
1735-0522
340
Design
Buckling Load of Symmetric Planar Frames with Semi-rigid Joints Using Graph Theory
Kaveh
A.
Rahimi Bondarabady
H.A.
Shahryari
L.
1
9
2006
4
3
157
175
03
11
2009
The main aim of this paper is to extend the recently developed methods for calculating the
buckling loads of planar symmetric frames to include the effect of semi-rigidity of the joints. This is
achieved by decomposing a symmetric model into two submodels and then healing them in such a
manner that the :::union::: of the eigenvalues of the healed submodels result in the eigenvalues of the
entire model. Thus the critical load of the frame is obtained using the eigenvalues of its submodels.
341
Three-dimensional modeling of strain localization in Cosserat continuum theory
Khoei
A.R.
Yadegari
S.
Anahid
M.
1
9
2006
4
3
176
191
03
11
2009
11
01
2014
In this paper, a higher order continuum model is presented based on the Cosserat
continuum theory in 3D numerical simulation of shear band localization. As the classical
continuum models suffer from the pathological mesh-dependence in strain softening models, the
governing equations are regularized by adding the rotational degrees-of-freedom to conventional
degrees-of-freedom. The fundamental relations in three-dimensional Cosserat continuum are
presented and the internal length parameters are introduced in the elasto-plastic constitutive matrix
to control the shear bandwidth. Finally, the efficiency of proposed model and computational
algorithm is demonstrated by a 3D strip in tensile. A comparison is performed between the classical
and Cosserat theories and the effect of internal length parameter is demonstrated. Clearly, a finite
shear bandwidth is achieved and the load-displacement curves are uniformly converged upon
different mesh sizes.
342
Analysis of Earthquake Response of an Asphalt Concrete Core Embankment Dam
Baziar
M.H.
Salemi
Sh.
Heidari
T.
1
9
2006
4
3
192
210
03
11
2009
11
01
2014
Seismic behavior of a rockfill dam with asphalt-concrete core has been studied utilizing
numerical models with material parameters determined by laboratory tests. The case study selected
for these analyses, is the Meyjaran asphalt core dam, recently constructed in Northern Iran, with
60 m height and 180 m crest length. The numerical analyses have been performed using a nonlinear
three dimensional finite difference software and various hazard levels of earthquakes.
This study shows that due to the elasto-plastic characteristics of the asphalt concrete, rockfill dams
with asphalt concrete core behave satisfactorily during earthquake loading. The induced shear
strains in the asphalt core, for the case presented in this research, are less than 1% during an
earthquake with amax=0.25g and the asphalt core remains watertight. Due to large shear
deformations caused by a more severe earthquake with amax=0.60g, some cracking may occur
towards the top of the core (down to 5-6 m), and the core permeability may increase in the top part,
but the dam is safe.
343
Comparison of Static and Dynamic Pushover Analysis in Assessment of the Target Displacement
R. Rofooei
F.
K. Attari
N.
Rasekh
A.
Shodja
A.H.
1
9
2006
4
3
212
225
03
11
2009
11
01
2014
Pushover analysis is a simplified nonlinear analysis technique that can be used to
estimate the dynamic demands imposed on a structure under earthquake excitations. One of the first
steps taken in this approximate solution is to assess the maximum roof displacement, known as
target displacement, using the base shear versus roof displacement diagram. That could be done by
the so-called dynamic pushover analysis, i.e. a dynamic time history analysis of an equivalent single
degree of freedom model of the original system, as well as other available approximate static
methods. In this paper, a number of load patterns, including a new approach, are considered to
construct the related pushover curves. In a so-called dynamic pushover analysis, the bi-linear and
tri-linear approximations of these pushover curves were used to assess the target displacements by
performing dynamic nonlinear time history analyses. The results obtained for five different special
moment resisting steel frames, using five earthquake records were compared with those resulted
from the time history analysis of the original system. It is shown that the dynamic pushover analysis
approach, specially, with the tri-linear approximation of the pushover curves, proves to have a
better accuracy in assessing the target displacements. On the other hand, when nonlinear static
procedure seems adequate, no specific preference is observed in using more complicated static
procedures (proposed by codes) compared to the simple first mode target displacement assessment.
344
Post-cyclic Behavior of Compacted Clay-sand Mixtures
Soltani-Jigheh
H.
Soroush
A.
1
9
2006
4
3
226
243
03
11
2009
11
01
2014
This paper presents the results of a series of monotonic and post-cyclic triaxial tests
carried out on a clay specimen and three types of clay-sand mixed specimens. The focus of the paper
is on the post-cyclic mechanical behavior of the mixed specimens, as compared to their monotonic
behavior. Analyses of the tests results show that cyclic loading degrade undrained shear strength
and deformation modulus of the specimens during the post-cyclic monotonic loading. The
degradation depends on the sand content, the cyclic strain level and to some degrees to the
consolidation pressure.
345
Selecting an Optimum Configuration of Urban One-Way and Two-Way Streets Using Genetic Algorithms
Afandizadeh Zargari
Sh.
Taromi
R.
1
9
2006
4
3
244
259
03
11
2009
11
01
2014
Optimization is an important methodology for activities in planning and design. The
transportation designers are able to introduce better projects when they can save time and cost of
travel for project by optimization methods. Most of the optimization problems in engineering are
more complicated than they can be solved by custom optimization methods. The most common and
available methods are heuristic methods. In these methods, the answer will be close to the optimum
answer but it isn’t the exact one. For achieving more accuracy, more time has been spent. In fact,
the accuracy of response will vary based on the time spent.
In this research, using the generic algorithms, one of the most effective heuristic algorithms, a
method of optimization for urban streets direction will be introduced. Therefore model of decision
making in considered one way – two way streets is developed. The efficiency of model in Qazvin
network is shown and the results compared whit the current situation as case study. The objective
function of the research is to minimize the total travel time for all users, which is one of the most
used in urban networks objectives.