Issue 2, 19, 2019

• DYNAMIC BUCKLING OF SHELL-LIKE STRUCTURES UNDER PRESSURES DUE TO AN EXPLOSION

  M. Ameijeiras, L. Godoy

  International Journal of Natural Disasters, Accidents and Civil Infrastructure (2019). Vol. 19, (2), 4

  
  

  Abstract

  The nonlinear dynamic response and buckling of a simple, two degree of freedom system is investigated in this work under an impulsive load that simulates a nearby detonation-like explosion. The system includes force and moment springs in much the same way as membrane and bending effects develop in shell structures. The static response is first obtained to evaluate bifurcation states and nonlinear equilibrium paths including geometric imperfections. The dynamic problem is modeled using Lagrange equation of motion. The nonlinear dynamic response under impulsive load is next computed for the perfect configuration under increasing load levels. The presence of quasi-bifurcations is detected using stability coefficients based on second order derivatives of the total potential energy. For a given load level, it is found that one stability coefficient vanishes at the first maximum in the displacement versus time trajectory, at which the system passes through a state of zero velocity. This occurs for the same displacement configuration as in the static buckling mode. The results show that quasi-bifurcation loads thus obtained are independent of the amplitude of the geometric imperfection considered but display high sensitivity to changes in the membrane to bending stiffness ratio.

  Abstract
  The nonlinear dynamic response and buckling of a simple, two degree of freedom system is investigated in this work under an impulsive load that simulates a nearby detonation-like [...]

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• CALCULO DE LA INTENSIDAD JMA PARA REGISTROS DEL LABORATORIO DE INGENIERÍA SÍSMICA DE COSTA RICA

  A. Moya

  International Journal of Natural Disasters, Accidents and Civil Infrastructure (2019). Vol. 19, (2), 3

  
  

  Abstract

  The JMA intensity was calculated for all the important events that the Earthquake Engineering Laboratory (LIS) has recorded since 1990. First, a pre-selection was made taking into account only events that had been recorded in more than 5 sites. Every record was plotted and revised by visual inspection in order to rule out those with high noise level or poor waveform quality. A frequency domain filter was applied to each component, then in the time domain the vectorial summation was computed and data was sorted out in descending order. The amplitude at which the cummulative amplitude reached a value of 0.3s was taken to compute the JMA intensity. The results are shown in the form of graphs that relate the value of JMA to the maximum acceleration and in the form of maps showing the spatial distribution of intensities.

  Abstract
  The JMA intensity was calculated for all the important events that the Earthquake Engineering Laboratory (LIS) has recorded since 1990. First, a pre-selection was made taking [...]

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• VELOCIDADES DE VIENTO EXTREMAS EN EL NORDESTE DE ARGENTINA

  B. Natalini, M. Natalini

  International Journal of Natural Disasters, Accidents and Civil Infrastructure (2019). Vol. 19, (2), 2

  
  

  Abstract

  The extreme wind map of the Argentinean code of practice CIRSOC 102 was updated in 1997 from records of the period 1967-1990. The information contained in this map is represented by the Basic Wind Speed, '''V'''. The contribution of the uncertainty of '''V '''to the whole uncertainty of the design wind load, of either a building or structure, is dominant with regard to the other variables that make up the wind load. Some authors asses this contribution to be above 70%, which underlines the importance of having good quality estimations of '''V'''. For this reason the extreme wind maps are updated periodically. In this work, results of '''V''' calculated from updated records of seven meteorological stations in north-eastern Argentina (NEA region) are presented. The values turn out to be noticeably lower than those of the CIRSOC 102; a reduction that is magnified when evaluated in terms of resulting wind loads. The records have been previously depurated after a combined assessment of both the quality of the instrumentation and the completeness of every yearly record. 95% confidence limits are presented, being the first time confidence limits are published for Argentina. Further values of '''V '''obtained after consolidating data of some stations in superstations are presented. Reductions of the confidence limits ranging 30% to 50% were observed.

  Abstract
  The extreme wind map of the Argentinean code of practice CIRSOC 102 was updated in 1997 from records of the period 1967-1990. The information contained in this map is represented [...]

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• ESTUDIO DE LA INFLUENCIA DE LAS IRREGULARIDADES EN PLANTA EN LA RESPUESTA SÍSMICA DE UNA ESTRUCTURA DE CONCRETO ARMADO

  L. Pérez Peña, G. Doz

  International Journal of Natural Disasters, Accidents and Civil Infrastructure (2019). Vol. 19, (2), 1

  
  

  Abstract

  The changes in the geometry of the structures are called irregularities and are divided into two types: plant and height irregularities, the latter being widely investigated. In this sense, the objective of the present work is to study in detail the influence of the plant irregularities in the seismic resistance of a reinforced concrete structure, to quantify and locate vulnerable zones in the structure. The proposed study is developed numerically using ETABS software Nonlinear v9.7.2 and MATLAB R2009b. The results showed that plant irregularities as they are placed in the structure, this is losing its bearing capacity and therefore its ability to withstand the lateral loads.

  Abstract
  The changes in the geometry of the structures are called irregularities and are divided into two types: plant and height irregularities, the latter being widely investigated. [...]

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