2020-12-02T13:33:42Z
http://scientiairanica.sharif.edu/?_action=export&rf=summon&issue=237
Scientia Iranica
Scientia Iranica
1026-3098
1026-3098
2009
16
5
Analytical and Numerical Study of FRP Retrotted RC Beams Under Low Velocity Impact
E.
Shafei
M.Z.
Kabir
Abstract. An analytical along with numerical analysis has been carried out to investigate the behavior
of concrete simply supported beams strengthened with Fiber-Reinforced Polymer (FRP) unidirectional
laminates under impact loading. Concrete beams are reinforced with a minimum ratio of
exural and
shear steel rebars and nally retrotted with epoxy-bonded high strength carbon FRP laminates in their
exure surfaces. The impact force was applied with a solid steel cylinder drop weight. Analytical results
showed that composite laminates externally bonded to reinforced concrete beam substrate can signicantly
enhance the performance of theses structural members to resist impact loadings. Also, based on the
obtained results, in retrotted beams the crack propagation happens in a desirable mode; an increasing
of yielded rebar zones and residual beam stiness. Retrotted beams were stier than unretrotted ones
in their rst impact response. The residual stiness of impacted concrete beams depends on their initial
stiness and the impact energy level. The analytical method uses an idealized elastic spring-mass model
and
exural wave propagation theory to calculate the dynamic response of assumed beams. Analytical
responses are adjusted due to an inelastic response, and nally are used for the simplied designation of
impact resisting reinforced concrete beams retrotting laminates.
Impact loading
Reinforced concrete beam
Composite laminate
Retrotting
FEM
2009
10
01
http://scientiairanica.sharif.edu/article_3118_37c3e34e146c22a1b0b3afd84196a49d.pdf
Scientia Iranica
Scientia Iranica
1026-3098
1026-3098
2009
16
5
A Numerical Study on the Eect of Accident Conguration on Pedestrian Lower Extremity Injuries
S.
Shahbeyk
A.
Abvabi
Abstract. An FE model of a pedestrian lower legform impactor has been developed and certied,
both statically and dynamically, based on EEVC-WG17 requirements. The legform is then utilized in
a series of 40 km/hr pedestrian accident analyses to assess the protection level delivered by a typical
sedan vehicle. The values of maximum tibia acceleration, maximum knee bending angle, and maximum
knee shearing displacement have been extracted for 25 dierent accident congurations and compared with
their admissible ranges. It has been shown that tibia acceleration is mainly in
uenced by extension of
the area transferring the impact load between the legform and the vehicle. However, variations of vehicle
front-end structure geometry and stiness in the vertical direction have been found to be the most decisive
parameters in the level of legform knee maximum bending rotation and maximum shearing displacement.
Pedestrian accident
Lower extremity injury
Bumper design
2009
10
01
http://scientiairanica.sharif.edu/article_3119_7b9fad3ca87e12fde63c01500bff2357.pdf
Scientia Iranica
Scientia Iranica
1026-3098
1026-3098
2009
16
5
Estimates of Average Inelastic Deformation Demands for Regular Steel Frames by the Endurance Time Method
H.E.
Estekanchi
H. T.
Riahi
A.
Vafai
Abstract. The Endurance Time (ET) method is a new dynamic pushover procedure in which
structures are subjected to gradually intensifying acceleration functions and their performance is assessed
based on the length of the time interval that they can satisfy required performance objectives. In this
paper, the accuracy of the Endurance Time method in estimating average deformation demands of low
and medium rise steel frames using ETA20f series of ET acceleration functions has been investigated. The
precision of the ET method in predicting the response of steel frames in nonlinear analysis is investigated
by considering a simple set of moment-resisting frames. An elastic-perfectly-plastic material model and
a bilinear material model with a post-yield stiness equal to 3% of the initial elastic stiness have been
considered. For frames with an elastic-perfectly-plastic material model, which are P ???? sensitive cases,
the ET analysis for the maximum interstory drift ratio somewhat underestimates the nonlinear response
history analysis results. The dierence between the results of the ET analysis and the nonlinear response
history analysis for the material model with 3% post-yield stiness is acceptable. The consistency of the
base shears obtained by the two methods is also satisfactory. It is shown that, although the results of the
ET analysis are not exactly consistent with the results of ground motions analysis, the ET method can
clearly identify the structure with a better performance even in the case of structures with a relatively
complicated nonlinear behavior.
nonlinear response history analysis
Dynamic pushover
Endurance Time method
Performance-based seismic engineering
2009
10
01
http://scientiairanica.sharif.edu/article_3120_7dd553bca269f3d2d35c4c250235cd5a.pdf
Scientia Iranica
Scientia Iranica
1026-3098
1026-3098
2009
16
5
Earthquake System Science: Potential for Seismic Risk Reduction
T. H.
Jordan
Abstract. Earthquakes in megacities such as Tehran and Los Angeles pose huge risks that could
jeopardize national prosperity and social welfare. Quantifying urban seismic risk is a dicult problem
because it requires detailed knowledge of the natural and the built environments, as well as an
understanding of both earthquake and human behaviors. Risk assessments can be improved through
international collaborations that combine the expertise of earthquake scientists and engineers. The most
eective strategies are seismic safety engineering, enforced through stringent building codes and disaster
preparations informed by realistic scenarios of large earthquake cascades. These strategies rely on the
ability to forecast earthquakes and their eects and to monitor earthquake cascades in near real time. The
practical problems of risk reduction are, thus, coupled to the basic problems of earthquake system science:
the interseismic dynamics of fault systems and the coseismic dynamics of fault rupture and groundmotion
excitation. In the United States, the Southern California Earthquake Center (SCEC) coordinates
an extensive research program in earthquake system science, which includes major eorts to improve
time-dependent earthquake rupture forecasts through better understanding of earthquake predictability
and to develop attenuation relationships that correctly model the physics of seismic wave propagation.
Earthquake system science relies on the premise that detailed studies of fault systems in dierent regions
can be synthesized into a generic understanding of earthquake phenomena. Achieving such a synthesis
will depend on international partnerships that facilitate the development and comparison of well-calibrated
regional models, and it will require the deployment of a cyberinfrastructure that can facilitate the creation
and
ow of information required to predict earthquake behavior. In the not-too-distant future, we will
be able to incorporate much more physics into seismic hazard and risk analysis through physics-based,
system-level simulations.
Seismic risk analysis
risk assessment
Earthquake prediction
seismic wave propagation
2009
10
01
http://scientiairanica.sharif.edu/article_3121_32ceb2a2ae214a12b445cad771696779.pdf
Scientia Iranica
Scientia Iranica
1026-3098
1026-3098
2009
16
5
Optimal Design of Geometrically Nonlinear Space Trusses Using an Adaptive Neuro-Fuzzy Inference System
E.
Salajegheh
J.
Salajegheh
S.M.
Seyedpoor
M.
Khatibinia
Abstract. An ecient methodology is proposed to optimize space trusses considering geometric
nonlinearity. The optimization task is performed by a continuous Particle Swarm Optimization (PSO).
Design variables are cross sectional areas of the trusses and their weights are also taken as the objective
function. Design constraints are dened to restrict nodal displacements and element stresses and
prevent the overall elastic instability of the structures during the optimization procedure. In order to
reduce the computational eort of the optimization process, an Adaptive Neuro Fuzzy Inference System
(ANFIS) is employed to approximate the nonlinear analysis of the structures instead of performing
via a time consuming Finite Element Analysis (FEA). The presented ANFIS is compared with a
Back Propagation Neural Network (BPNN) and appears to produce a better performance generality for
evaluating structure design values. Test example results demonstrate the computational advantages of the
suggested methodology for optimum design of geometrically nonlinear space trusses.
Space truss
Geometric nonlinearity
particle swarm optimization
Approximation concepts
Adaptive neuro fuzzy inference system
2009
10
01
http://scientiairanica.sharif.edu/article_3122_5f4237f23472d22ac8911b8f060429e0.pdf