Vol. 7(9) September 2014
A Novel Wavelet based Relative Displacement Analysis
of Structure subjected to Seismic Base Excitation
Beena Mol M., Prabavathy S. and Mohanalin J.
During earthquakes, structures are subjected to time
varying seismic forces which in turn produce time dependent displacements and stresses
within the structures. Improving the efficiency in analyzing the displacement within
the structure and designing an earthquake resistant structure (EQRS) depends on
the detailed information about the earthquake loading force acting at the base of
the structure. Seismic signals called accelerograms are the only available sources
of detailed and critical information about the earthquake random cyclic forces.
Hence the ground motion information from the accelerograms is required for designing
the EQRS. Therefore, each recorded accelerogram is an asset for the progress in
earthquake and seismological engineering. However, due to various environmental
and instrumental disturbances these recorded data are highly contaminated. Retrieval
of information from contaminated seismic signals is a challenging and demanding
area of research. It is a traditional choice to use ‘universal’, ‘normal’ or ‘Bayes’
threshold in wavelet domain to remove the noise. However, the lack of homogeneity
present in the accelerogram signal distribution requires a localized thresholding
approach over the traditional global techniques. In this study, the localized rule
based thresholding technique is applied for processing the seismic signals. This
is followed by a case study in which the impact of the noise has been analyzed in
obtaining the acceleration, velocity, displacement and relative displacement parameters
of a multistory reinforced concrete structure. It has been found that these parameters
are excellently procured by the localized approach, thereby enhancing the design
accuracy. In short, the main contribution of this study is twofold, first to introduce
the localized wavelet based approach to the seismic research community and secondly
to study its impact in seismic structural analysis.
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Lessons on post-disater reconstruction and geohazard
prevention from the Wenchuan earthquanke
Wang Yunsheng, Hu Qinlong, Zhi Jingzi and Deng Xi
A strong earthquake like the Wenchuan earthquake on May
12th, 2008 in China could cause huge losses in human lives and properties damages
in a short time. Reconstruction projects have been carried out after the earthquake
with varying degrees of success. This paper deals with a couple of issues arising
after the Wenchuan earthquake from which certain lessons can be drawn. The original
seismic zoning in the earthquake area proved to be under valuated. A safe distance
of the buildings from active fault zones was not respected in the mountain towns.
Many villages in these mountains were not built in a safe geological environment.
An anti -seismic design of the buildings was not respected enough. The amount of
loose source material for debris flows after the earthquake was under estimated
leading to ineffective designs of remedial works. The level of new designed roads,
bridges and tunnels proved to be too low due to an under estimate of the rise of
the river beds in the main valleys. Areas with a high hazard for flooding and debris
flows were ignored in the planning of new built up areas.
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Characteristics of the horizontal response spectrum
using ground motions observed in and around Korean peninsula
Jun Kyoung Kim and Tae Seok Oh
This study analyzed the influences of frequency and epicentral
distance on the design response spectrum as these variables are reported to be highly
sensitive to the characteristics of horizontal normalized response values. The present
work also investigated the adequacy of US Nuclear Regulatory Committee's Regulatory
Guide 1.60 which has been applied to Korean nuclear facilities since the 1970’s
and the Korean Uniform Building Code. Data of 260 horizontal components from 20
recent moderate magnitude earthquakes were selected and analyzed. The responses
at 500 frequencies from 0.1 Hz to 50 Hz by 0.1 Hz were calculated. Horizontal normalized
response values are found to be significantly influenced by frequency and epicentral
distances. As the epicentral distance increases, frequency with maximum normalized
response values of 4 groups tends to move gradually to lower resonance frequency.
Normalized response values at higher frequencies such as 50, 40, 30, and 20 Hz tend
to decrease gradually as the epicentral distance increases. Considering all 4 epicentral
distance groups, Regulatory Guide 1.60 is less conservative at higher frequency
bands above approximately 5 to 10 Hz, depending on the epicentral distance. Therefore,
the regulatory guide standards should be considered more conservatively considering
the Korean seismotectonic environments.
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Earthquake Source Parameters and their Scaling for
the Uttarakhand region of North-West Himalaya
Kumar Arjun, Kumar Ashwani, Gupta S. C., Mittal Himanshu and Sen Arup
The Uttarakhand region of North-West Himalaya exhibits
high historic and instrumental seismicity as evidenced by the occurrence of several
moderate to large-sized earthquakes in the region. Source parameters of 16 small
and moderate-sized earthquakes (3.1≤Mw≤6.7) have been estimated and a scaling law
for the region has been developed. In this study software EQK_SRC_PARA33 has been
used that considers Brune’s model that yields a fall-off of 2 beyond corner frequencyfc
with high frequency dimunition factor presented by Boore7 to estimate fmax. The
estimated seismic moments range from 5.1×1013 to 1.10×1019Nm. The source radii are
confined between 200 m to 9.7km, the stress drop ranges between 2.59MPa to 8.34MPa
respectively. Using the data set of 16 events, a scaling law, M0 fc3 = 3.0 x 1016
Nm/s3 has been developed for the region. From the plot between seismic moment and
fmax, the values of fmax seem to be dependent on the source size and vary from 4
Hz to 18 Hz at various sites falling in the Uttarakhand region of NW Himalaya. Comparing
the average stress drop of 6.0 MPa obtained in the present study, with the global
average of 3.0 MPa for inter-plate earthquakes, it can be inferred that the average
stress drop associated with the small and moderate earthquakes is almost double
in the Uttarakhand region of NW Himalaya. The estimates of stress drops, fmax and
scaling law will help to simulate strong ground motion using stochastic methods
for this region.
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Field-observed buildings behavior during the 2013
Lushan Mw 6.6 earthquake in China
Liu Yufa and Huang Runqiu
The 2013 Lushan Mw6.6 earthquake hit the southwestern
China at 8:02 A.M of 20th April, 2013, leading to enormously economic and human
losses which were mainly due to the building damage or destruction. A majority of
the buildings in the earthquake region were either of non-engineered buildings including
unconfined brick masonry building and wood-frame building in rural area or engineered
buildings including confined brick masonry building and reinforced concrete frame
building in urban area. The engineered buildings performed generally satisfactorily
but for non-structural damage in some instances; however, non-engineered buildings,
especially unconfined brick masonry building performed very poorly, the incorrect
choice of sites, lack of integrity, the unreasonable structural arrangement and
construction process of buildings observed on the spot, can be responsible for the
catastrophe. However, many traditional wood-frame buildings stayed intact when experienced
maximum peak ground acceleration (PGA) of 0.9g, cracking the record of 0.6g registered
in previous earthquakes.
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A Simulation of Extraction Effect of Upper Protecting
Seam Basing on UDEC
Gao Bao-bin, Liu Yun-peng and Yuan Dong-sheng
It has been confirmed by many studies that protecting
layer mining is the most effective measure to prevent coal dynamic disasters. Taking
Fusheng Coal Mine of Lu′an Group as engineering background to research the feasibility
and protective effect of close distance upper protective layer mining, namely mining
14# coal seam as protective seam to eliminate outburst of 15# coal seam, use UDEC
numerical calculation program to simulate the rock stratum displacement, stress
change and expansion ratio of protected seam through building similar model. The
results show that the expansion ratio reaches 3%, meeting the relevant standard
of prevention and control of coal and gas outburst, and the stress distribution
accords with the moving law of coal and rock which is of great theoretical significance
and practical value for Fusheng Coal Mine to take upper protective layer mining
as its outburst prevention technique measure.
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Preventing man-made disaster in the European Union:The
‘Shamrock’ Transportation Security Assessment Scheme
Zamparini Luca and Reniers Genserik
All transport networks are, to a certain extent, vulnerable
to man-made disasters that imply momentous consequences at the economic and social
level. Coordination among all involved actors in international transport chains
is thus a relevant pre-requisite for the minimization of security risk. This paper
discusses the heterogeneity within the EU-28 Member States, from a socio-economic
point of view, as well as from a transportation perspective. In combination with
this heterogeneity, the diversity of transportation security policies among the
countries is remarkable. Nonetheless, to be able to efficiently and effectively
and pro-actively as well as re-actively, tackle transportation security problems,
there should be a systematic approach that is followed within the European Union.
Such a transportation security assessment scheme is (called Shamrock scheme) composed
of four stages (definition, communication, responsibilities and handling).
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A 3-D Numerical Model for assessing Rockfall Hazard
Cheng-Yu Ku
This paper presents the development of a three-dimensional
numerical model for assessing the rockfall hazards using the probabilistic analysis
based on the lumped mass method. Due toBecause the reliable prediction of rockfalls
is highly related to the three-dimensional nature of actual slope geometry, the
proposed model can be integrated with very high accuracy highly accurate DEM from
ground Light light Detection detection And and Ranging ranging (LiDAR) measurements.
Furthermore, theThis study employs probability and statisticals analysis of in the
analysis of rockfall simulations for dealingto deal with the uncertainties, such
as the coefficients of restitution, the slope friction and the location and velocity
of where the rocks beginoriginate, are employed in this study. Results obtained
demonstrate that the proposed approach proves tocan effectively account for rockfall
dynamics and may provide a useful tool for quantitative assessment of rockfall hazards
. Furthermore, theThe proposed three-dimensional rockfall numerical model can greatly
increase the reliability of the prediction ofpredicting rockfall trajectories with
the useusing of the high resolution DEM and can exhibit great potentials for practical
applications in the future.
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An investigation into the disaster management lessons
learnt out of Fukushima Daiichi nuclear disaster
Deepa Ramachandran and Karthikeyan P.
There is no query that the Fukushima Daiichi Nuclear
Power Plant accident in 2011 after the 9.0 magnitude earthquake that hit Japan and
consequent tsunami had a major influence not only on people’s safety and the surroundings
enclosing the site but also on economy of Japanese due to the affectation on agriculture
and energy sectors. However the influences of accident developed beyond the border
of Japanese and perverted risk perception of public towards plants of nuclear energy
around the globe. In order to assure the continued nuclear facilities operation,
it is essential to develop the trust of public by taking proper measures that lead
to a generalized development in the security at nuclear facilities and by a good
risk communication with public. Any individual included in safety process must contribute
to expanding trust in risk management firms and regulatory agencies based on efficient
risk communication and sound science practices. This study has discussed about the
losses which occurred in Japan due to the Fukushima disaster and suggested lessons
of disaster management to avoid disasters in future.
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Seismic behavior of RC columns strengthened with prestressed
high strength steel wire mesh
Deng Zongcai, Guo Jianping and Jumbe R. Daud
An innovative retrofitting technique of prestressed high
strength steel wire mesh (PSWM) with new tension and anchor system is presented.
It consists of external prestressing of columns in transverse direction by means
of individual hoops with prestressing high strength strands and specially designed
anchorage system. 18 columns are prepared, two of which are control specimens and
16 retrofitted columns and a seismic performance test was conducted. Effects of
steel strand spacing, prestressed level and axial compression ratio on seismic retrofitting
performance and energy dissipation are studied. As the strand spacing is reduced,
retrofitting effectiveness, bearing capacity and ductility are significantly improved.
As prestressing level is increased, retrofitting effectiveness is improved as well,
i.e. comparing prestressed and control columns, specimens with strand spacing 60
mm and axial compression ratio 0.4, yield load increased by 9.1%, and ductility
factor increased by 11.0%; for specimens with strand spacing of 60 mm and axial
compression ratio of 0.8, ultimate load increased by 17.6%. Specimens under high
axial compression ratio displayed significantly improved yield load, ultimate load
and ductility factor. The influence of strand spacing on the seismic behavior of
the retrofitted columns is more significant than effect of prestressing level.
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