Disaster Advances

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Disaster Advances





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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