GIES - Geofísica i Enginyeria Sísmica
http://hdl.handle.net/2117/477
2018-01-23T19:48:33ZEarthquake static stress transfer in the 2013 Gulf of Valencia (Spain) seismic sequence
http://hdl.handle.net/2117/107836
Earthquake static stress transfer in the 2013 Gulf of Valencia (Spain) seismic sequence
Salo Salgado, Lluis; Frontera Genovard, Tànit; Goula Suriñach, Xavier; Pujades Beneit, Lluís; Ledesma Villalba, Alberto
On 24 September 2013, an Ml 3.6 earthquake struck in the Gulf of Valencia (Spain) near the Mediterranean coast of Castelló, roughly 1 week after gas injections conducted in the area to develop underground gas storage had been halted. The event, felt by the nearby population, led to a sequence build-up of felt events which reached a maximum of Ml 4.3 on 2 October. Here, we study the role of static stress transfer as an earthquake-triggering mechanism during the main phase of the sequence, as expressed by the eight felt events. By means of the Coulomb failure function, cumulative static stress changes are quantified on fault planes derived from focal mechanism solutions (which act as both source and receiver faults) and on the previously mapped structures in the area (acting only as stress receivers in our modeling). Results suggest that static stress transfer played a destabilizing role and point towards an SE-dipping structure underlying the reservoir (or various with analogous geometry) that was most likely activated during the sequence. One of the previously mapped faults could be geometrically compatible, yet our study supports deeper sources. Based on this approach, the influence of the main events in the occurrence of future and potentially damaging earthquakes in the area would not be significant.
2017-09-20T15:38:41ZSalo Salgado, LluisFrontera Genovard, TànitGoula Suriñach, XavierPujades Beneit, LluísLedesma Villalba, AlbertoOn 24 September 2013, an Ml 3.6 earthquake struck in the Gulf of Valencia (Spain) near the Mediterranean coast of Castelló, roughly 1 week after gas injections conducted in the area to develop underground gas storage had been halted. The event, felt by the nearby population, led to a sequence build-up of felt events which reached a maximum of Ml 4.3 on 2 October. Here, we study the role of static stress transfer as an earthquake-triggering mechanism during the main phase of the sequence, as expressed by the eight felt events. By means of the Coulomb failure function, cumulative static stress changes are quantified on fault planes derived from focal mechanism solutions (which act as both source and receiver faults) and on the previously mapped structures in the area (acting only as stress receivers in our modeling). Results suggest that static stress transfer played a destabilizing role and point towards an SE-dipping structure underlying the reservoir (or various with analogous geometry) that was most likely activated during the sequence. One of the previously mapped faults could be geometrically compatible, yet our study supports deeper sources. Based on this approach, the influence of the main events in the occurrence of future and potentially damaging earthquakes in the area would not be significant.Rainfall intensity patterns derived from the urban network of Barcelona (NE Spain)
http://hdl.handle.net/2117/107815
Rainfall intensity patterns derived from the urban network of Barcelona (NE Spain)
Lana Pons, Francisco Javier; Serra de Larrocha, Carina; Casas Castillo, M. del Carmen; Rodríguez Solá, Raúl
An analysis of the normalised rainfall intensity curves in Barcelona (NE Spain) has been undertaken from selected rain rate episodes recorded by an urban network of tipping buckets applying a 5-min integration time along the years 1994–2009. These curves, based on cumulative amount and time distributions, are modelled by a power law, this fact suggesting fractal behaviour. Four parameters characterise these curves. One of them is the exponent of the power law. Another one quantifies the intermittency of the rainfall along the episode. The other two are the coordinates of cumulative
amount and time distribution from which the power law fits well the normalised curve. The total rainfall amount of the episode, its length and the coefficient of variation of the 5-min amounts are also considered as complementary parameters. Taking advantage of these seven parameters, patterns of rainfall intensity are determined for every episode. These patterns, together with the statistical distribution of 5-min amounts, maximum intensity and rainfall intermittence,
should increase the knowledge on the urban rainfall regime with the aim of improving drainage design. In addition to present results, flood prevention should be complemented with extreme value analyses and quantification of return periods.
2017-09-20T10:28:05ZLana Pons, Francisco JavierSerra de Larrocha, CarinaCasas Castillo, M. del CarmenRodríguez Solá, RaúlAn analysis of the normalised rainfall intensity curves in Barcelona (NE Spain) has been undertaken from selected rain rate episodes recorded by an urban network of tipping buckets applying a 5-min integration time along the years 1994–2009. These curves, based on cumulative amount and time distributions, are modelled by a power law, this fact suggesting fractal behaviour. Four parameters characterise these curves. One of them is the exponent of the power law. Another one quantifies the intermittency of the rainfall along the episode. The other two are the coordinates of cumulative
amount and time distribution from which the power law fits well the normalised curve. The total rainfall amount of the episode, its length and the coefficient of variation of the 5-min amounts are also considered as complementary parameters. Taking advantage of these seven parameters, patterns of rainfall intensity are determined for every episode. These patterns, together with the statistical distribution of 5-min amounts, maximum intensity and rainfall intermittence,
should increase the knowledge on the urban rainfall regime with the aim of improving drainage design. In addition to present results, flood prevention should be complemented with extreme value analyses and quantification of return periods.Fractal analysis and statistics of seismic generation rates: the example of the southern California
http://hdl.handle.net/2117/105977
Fractal analysis and statistics of seismic generation rates: the example of the southern California
Lana Pons, Francisco Javier; Martínez Santafé, Maria Dolors; Amir Hosseini, Seyed; Serra de Larrocha, Carina
The seismic generation rate, SGR, at southern California along the 1981–2007 recording period is analysed with the main purpose of finding out whether there exist some correlations between seismic activity before, after and along aftershock sequences triggered by mainshocks of high magnitude. The possibility that a mainshock could be triggered by another neighbouring mainshock and its aftershock sequence is also investigated. The analyses are based on monthly SGR series, obtained as the number of events detected every month along the recording period considered. These monthly SGR series are derived for three aftershock areas associated with Landers (June 28, 1992, Mw = 7.3), Northridge (January 17, 1994, Mw = 6.7) and Hector Mine (October 16, 1999, Mw = 7.1) mainshocks. The most relevant features of SGR series are investigated through various techniques: 1) the rescaled range analysis and the interpretation of the Hurst exponent in terms of persistence, anti-persistence and randomness; 2) time trend estimation by the Kendall-tau algorithm and assessment of their statistical significance by the Mann-Kendall test; 3) the self-affine character, derived from semivariograms, and the Hausdorff measure; 4) autocorrelation and power spectra; 5) cross-correlation and cross-power spectra; 6) the search for the statistical distribution best reproducing the empirical probability of SGR series. Additionally, a close look at plots of epicenters within the aftershock areas, distinguishing between periods of background and aftershock activity, permits detecting some features of the seismicity. Changes on spatial patterns of seismicity suggest that the effects of tectonic stress redistribution could persist beyond an aftershock period, at short and medium distances of the mainshock. This possibility would be also in agreement with cross-correlation results for SGR series.
2017-06-29T09:57:45ZLana Pons, Francisco JavierMartínez Santafé, Maria DolorsAmir Hosseini, SeyedSerra de Larrocha, CarinaThe seismic generation rate, SGR, at southern California along the 1981–2007 recording period is analysed with the main purpose of finding out whether there exist some correlations between seismic activity before, after and along aftershock sequences triggered by mainshocks of high magnitude. The possibility that a mainshock could be triggered by another neighbouring mainshock and its aftershock sequence is also investigated. The analyses are based on monthly SGR series, obtained as the number of events detected every month along the recording period considered. These monthly SGR series are derived for three aftershock areas associated with Landers (June 28, 1992, Mw = 7.3), Northridge (January 17, 1994, Mw = 6.7) and Hector Mine (October 16, 1999, Mw = 7.1) mainshocks. The most relevant features of SGR series are investigated through various techniques: 1) the rescaled range analysis and the interpretation of the Hurst exponent in terms of persistence, anti-persistence and randomness; 2) time trend estimation by the Kendall-tau algorithm and assessment of their statistical significance by the Mann-Kendall test; 3) the self-affine character, derived from semivariograms, and the Hausdorff measure; 4) autocorrelation and power spectra; 5) cross-correlation and cross-power spectra; 6) the search for the statistical distribution best reproducing the empirical probability of SGR series. Additionally, a close look at plots of epicenters within the aftershock areas, distinguishing between periods of background and aftershock activity, permits detecting some features of the seismicity. Changes on spatial patterns of seismicity suggest that the effects of tectonic stress redistribution could persist beyond an aftershock period, at short and medium distances of the mainshock. This possibility would be also in agreement with cross-correlation results for SGR series.Seismic damage assessment of URM buildings: a comparison of non-linear static procedures
http://hdl.handle.net/2117/105901
Seismic damage assessment of URM buildings: a comparison of non-linear static procedures
González Drigo, José Ramón; Ávila Haro, Jorge Arturo; Pujades Beneit, Lluís; Barbat Barbat, Horia Alejandro
In the scientific literature, a significant number of non-linear procedures are proposed in order to evaluate the seismic vulnerability of a building. In this work, and in the context of the Risk-UE methodology, a complete comparison of six representative nonlinear procedures, applied to an unreinforced building, has been performed. The incremental dynamic analysis has been considered in order to provide a reference for comparisons. Additionally, the evaluation of the applicability and reliability of the nonlinear static procedures has been performed and, some simple modifications, oriented to improve their use, have been proposed. The seismic demand has been conveniently defined applying the conditional spectrum approach procedure. Two different methodologies were used in order to define the fragility curves. Accordingly, a complete comparison of the calculated damage indices and the damage curves, corresponding to the different considered peak ground acceleration values,
has been undertaken. The comparison results let know that the damage curves obtained by performing the non-linear procedures and by applying the Risk-UE methodology tend to overestimate the damage corresponding to low values of the PGA while the damage related to higher values of the PGA is underestimated.
2017-06-27T13:57:34ZGonzález Drigo, José RamónÁvila Haro, Jorge ArturoPujades Beneit, LluísBarbat Barbat, Horia AlejandroIn the scientific literature, a significant number of non-linear procedures are proposed in order to evaluate the seismic vulnerability of a building. In this work, and in the context of the Risk-UE methodology, a complete comparison of six representative nonlinear procedures, applied to an unreinforced building, has been performed. The incremental dynamic analysis has been considered in order to provide a reference for comparisons. Additionally, the evaluation of the applicability and reliability of the nonlinear static procedures has been performed and, some simple modifications, oriented to improve their use, have been proposed. The seismic demand has been conveniently defined applying the conditional spectrum approach procedure. Two different methodologies were used in order to define the fragility curves. Accordingly, a complete comparison of the calculated damage indices and the damage curves, corresponding to the different considered peak ground acceleration values,
has been undertaken. The comparison results let know that the damage curves obtained by performing the non-linear procedures and by applying the Risk-UE methodology tend to overestimate the damage corresponding to low values of the PGA while the damage related to higher values of the PGA is underestimated.Capacity curve based damage index for steel buildings: a probabilistic approach
http://hdl.handle.net/2117/105900
Capacity curve based damage index for steel buildings: a probabilistic approach
Díaz-Alvarado, S.A.; Pujades Beneit, Lluís; Barbat Barbat, Horia Alejandro; Hidalgo-Leiva, D.A.; Vargas Alzate, Yeudy Felipe
The capacity and expected seismic damage of several types of steel buildings are assessed by using a probabilistic approach. Nonlinear static and dynamic analyses are performed by means of Monte Carlo Simulations. Concerning to the nonlinear static approach, it is shown that a new damage model, recently developed for reinforced concrete buildings, also holds for steel buildings. The new damage index is defined as a combination of the energy dissipation and the one of the secant stiffness degradation; both functions are obtained from the capacity curve in a straightforward way. The analyzed buildings are archetypal of the Mexico City and the seismic actions are selected so that they are compatible with the design spectra provided in the seismic code. The results show that, in average, the Park and Ang index, calculated by means
of incremental dynamic analysis, is well fitted by the combination of the contributions to damage of the stiffness degradation (71%) and the one of the energy loss (29%). The obtained results confirm that the new damage model can be a powerful tool for probabilistic assessments of seismic damage.
2017-06-27T13:50:12ZDíaz-Alvarado, S.A.Pujades Beneit, LluísBarbat Barbat, Horia AlejandroHidalgo-Leiva, D.A.Vargas Alzate, Yeudy FelipeThe capacity and expected seismic damage of several types of steel buildings are assessed by using a probabilistic approach. Nonlinear static and dynamic analyses are performed by means of Monte Carlo Simulations. Concerning to the nonlinear static approach, it is shown that a new damage model, recently developed for reinforced concrete buildings, also holds for steel buildings. The new damage index is defined as a combination of the energy dissipation and the one of the secant stiffness degradation; both functions are obtained from the capacity curve in a straightforward way. The analyzed buildings are archetypal of the Mexico City and the seismic actions are selected so that they are compatible with the design spectra provided in the seismic code. The results show that, in average, the Park and Ang index, calculated by means
of incremental dynamic analysis, is well fitted by the combination of the contributions to damage of the stiffness degradation (71%) and the one of the energy loss (29%). The obtained results confirm that the new damage model can be a powerful tool for probabilistic assessments of seismic damage.Evaluation of seismic damage in low-rise buildings of reinforced concrete masonry
http://hdl.handle.net/2117/105899
Evaluation of seismic damage in low-rise buildings of reinforced concrete masonry
Hidalgo-Leiva, D.A.; Pujades Beneit, Lluís; Barbat Barbat, Horia Alejandro; Díaz-Alvarado, S.A.; Vargas Alzate, Yeudy Felipe
The assessment of damage caused by earthquakes in structures, requires the use of nonlinear analysis, either static or dynamic, in order to define the performance of the buildings for the considered hazard levels. In this paper, different damage models based on static and dynamic nonlinear analysis are used in the evaluation of a lowrise building with reinforced concrete masonry, which is the main structural material used in Costa Rica. The fragility curves and the mean damage index are defined from the static nonlinear analysis. The Park&Ang index is also obtained as a global damage index when the dynamic nonlinear analysis is performed. Damage is then described with discrete damage states and, for each damage state, displacement thresholds are
defined. Finally, a Park&Ang compatible damage curve is obtained as a combination of the secant stiffness degradation and the plastic displacement energy curves, all obtained from the capacity curve obtained with Pushover analysis.
2017-06-27T13:43:03ZHidalgo-Leiva, D.A.Pujades Beneit, LluísBarbat Barbat, Horia AlejandroDíaz-Alvarado, S.A.Vargas Alzate, Yeudy FelipeThe assessment of damage caused by earthquakes in structures, requires the use of nonlinear analysis, either static or dynamic, in order to define the performance of the buildings for the considered hazard levels. In this paper, different damage models based on static and dynamic nonlinear analysis are used in the evaluation of a lowrise building with reinforced concrete masonry, which is the main structural material used in Costa Rica. The fragility curves and the mean damage index are defined from the static nonlinear analysis. The Park&Ang index is also obtained as a global damage index when the dynamic nonlinear analysis is performed. Damage is then described with discrete damage states and, for each damage state, displacement thresholds are
defined. Finally, a Park&Ang compatible damage curve is obtained as a combination of the secant stiffness degradation and the plastic displacement energy curves, all obtained from the capacity curve obtained with Pushover analysis.New parametric model for capacity curves and a new capacity based damage index
http://hdl.handle.net/2117/105898
New parametric model for capacity curves and a new capacity based damage index
Pujades Beneit, Lluís; Vargas Alzate, Yeudy Felipe; Barbat Barbat, Horia Alejandro; González Drigo, José Ramón; Díaz-Alvarado, S.A.; Hidalgo-Leiva, D.A.
A recently proposed parametric model re-conceptualizes capacity curves as composed by linear and non-linear parts. The normalized non-linear capacity curve can be modelled by a cumulative lognormal function. While the linear part is defined by the initial stiffness, the non-linear part keeps the information about the physical degradation of the structure for increasing drifts. Besides, the non-linear part of capacity curves allows defining new curves related to energy loss and to tangent and secant stiffness degradation. It has been shown that an adequate combination of the energy loss and secant stiffness degradation functions leads to a good pointer of physical damage and, therefore, it can be used as a new damage index. This new damage index can be calibrated in such a way that it is equivalent to the well-known Park and Ang damage index, which, in turn, can be obtained from incremental dynamic analyses. In this paper the theoretical formulation of the parametric model and the one of the new damage index are reviewed first. Then the relation between the degradation of the building and the increase of its fundamental period of response is investigated, showing that the increase of the period can be also a good damage forecaster.
2017-06-27T13:33:06ZPujades Beneit, LluísVargas Alzate, Yeudy FelipeBarbat Barbat, Horia AlejandroGonzález Drigo, José RamónDíaz-Alvarado, S.A.Hidalgo-Leiva, D.A.A recently proposed parametric model re-conceptualizes capacity curves as composed by linear and non-linear parts. The normalized non-linear capacity curve can be modelled by a cumulative lognormal function. While the linear part is defined by the initial stiffness, the non-linear part keeps the information about the physical degradation of the structure for increasing drifts. Besides, the non-linear part of capacity curves allows defining new curves related to energy loss and to tangent and secant stiffness degradation. It has been shown that an adequate combination of the energy loss and secant stiffness degradation functions leads to a good pointer of physical damage and, therefore, it can be used as a new damage index. This new damage index can be calibrated in such a way that it is equivalent to the well-known Park and Ang damage index, which, in turn, can be obtained from incremental dynamic analyses. In this paper the theoretical formulation of the parametric model and the one of the new damage index are reviewed first. Then the relation between the degradation of the building and the increase of its fundamental period of response is investigated, showing that the increase of the period can be also a good damage forecaster.Seismic assessment of high-rise URM buildings: a probabilistic approach
http://hdl.handle.net/2117/105897
Seismic assessment of high-rise URM buildings: a probabilistic approach
Ávila Haro, Jorge Arturo; González Drigo, José Ramón; Pujades Beneit, Lluís; Barbat Barbat, Horia Alejandro
The definition of the seismic demand and the correct characterization of the mechanical properties of the materials are two of the major difficulties in the seismic damage assessment of unreinforced masonry buildings due to the large uncertainties and variability that they present. A seven-story unreinforced masonry building in Barcelona, Spain, is taken as a case-study and modeled as an isolated solid clay structure with unidirectional iron beams-brick vaults slabs and load-bearing walls. In order to overcome the material definition shortcomings, the compressive strength, Young modulus, shear modulus and shear strength are modeled as random variables. On the other hand, the seismic demand variability is addressed through a set of different ground motions selected with the conditional spectrum method and subsequently scaled to different levels of demand (pga) as the incremental dynamic analysis methodology suggests. Due to computational and time limitations, a sufficiently representative sample is selected firstly from the population of mechanical properties, and secondly from the population of dynamics analyses for each direction of analysis. The obtained results show the correlation and different grades of influence for each of the selected random variables and levels of seismic demand (pga).
2017-06-27T13:16:22ZÁvila Haro, Jorge ArturoGonzález Drigo, José RamónPujades Beneit, LluísBarbat Barbat, Horia AlejandroThe definition of the seismic demand and the correct characterization of the mechanical properties of the materials are two of the major difficulties in the seismic damage assessment of unreinforced masonry buildings due to the large uncertainties and variability that they present. A seven-story unreinforced masonry building in Barcelona, Spain, is taken as a case-study and modeled as an isolated solid clay structure with unidirectional iron beams-brick vaults slabs and load-bearing walls. In order to overcome the material definition shortcomings, the compressive strength, Young modulus, shear modulus and shear strength are modeled as random variables. On the other hand, the seismic demand variability is addressed through a set of different ground motions selected with the conditional spectrum method and subsequently scaled to different levels of demand (pga) as the incremental dynamic analysis methodology suggests. Due to computational and time limitations, a sufficiently representative sample is selected firstly from the population of mechanical properties, and secondly from the population of dynamics analyses for each direction of analysis. The obtained results show the correlation and different grades of influence for each of the selected random variables and levels of seismic demand (pga).Complexity and predictability of the monthly Western Mediterranean oscillation index
http://hdl.handle.net/2117/105695
Complexity and predictability of the monthly Western Mediterranean oscillation index
Lana Pons, Francisco Javier; Burgueño Rivero, August; Martínez Santafé, Maria Dolors; Serra de Larrocha, Carina
The complexity, predictability and predictive instability of the Western Mediterranean Oscillation index (WeMOi) at monthly scale, years 1856-2000, are analysed from the viewpoint of monofractal and multifractal theories. The complex physical mechanism is quantified by: (1) the Hurst exponent, H, of the rescaled range analysis; (2) correlation and embedding dimensions, mu* and d(E), together with Kolmogorov entropy, kappa, derived from the reconstruction theorem; and (3) the critical Holder exponent, alpha(o), the spectral width, W, and the asymmetry of the multifractal spectrum, f(alpha). The predictive instability is described by the Lyapunov exponents, lambda, and the Kaplan-Yorke dimension, D-KY, while the self-affine character is characterized by the Hausdorff exponent, H-a. Relationships between the exponent beta, which describes the dependence of the power spectrum S(f) on frequency f, and the Hurst and Hausdorff exponents suggest fractional Gaussian noise (fGn) as a right simulation of empiric WeMOi. Comparisons are made with monthly North-Atlantic Oscillation and Atlantic Multidecadal Oscillation indices. The analysis is complemented with an ARIMA(p,1,0) autoregressive process, which yields a more accurate prediction of WeMOi than that derived from fGn simulations.
2017-06-21T09:58:47ZLana Pons, Francisco JavierBurgueño Rivero, AugustMartínez Santafé, Maria DolorsSerra de Larrocha, CarinaThe complexity, predictability and predictive instability of the Western Mediterranean Oscillation index (WeMOi) at monthly scale, years 1856-2000, are analysed from the viewpoint of monofractal and multifractal theories. The complex physical mechanism is quantified by: (1) the Hurst exponent, H, of the rescaled range analysis; (2) correlation and embedding dimensions, mu* and d(E), together with Kolmogorov entropy, kappa, derived from the reconstruction theorem; and (3) the critical Holder exponent, alpha(o), the spectral width, W, and the asymmetry of the multifractal spectrum, f(alpha). The predictive instability is described by the Lyapunov exponents, lambda, and the Kaplan-Yorke dimension, D-KY, while the self-affine character is characterized by the Hausdorff exponent, H-a. Relationships between the exponent beta, which describes the dependence of the power spectrum S(f) on frequency f, and the Hurst and Hausdorff exponents suggest fractional Gaussian noise (fGn) as a right simulation of empiric WeMOi. Comparisons are made with monthly North-Atlantic Oscillation and Atlantic Multidecadal Oscillation indices. The analysis is complemented with an ARIMA(p,1,0) autoregressive process, which yields a more accurate prediction of WeMOi than that derived from fGn simulations.La gestión de la calidad: algunas reflexiones sobre los procesos de calidad que se implantan en los centros docentes universitarios
http://hdl.handle.net/2117/105475
La gestión de la calidad: algunas reflexiones sobre los procesos de calidad que se implantan en los centros docentes universitarios
Pérez Gracia, María de la Vega; López López, José; Buenestado Caballero, Pablo; Garcia-Alzórriz Pardo, Juan Antonio; Torres Cámara, Ricardo; Martínez Sánchez, Joan; Velasco Quesada, Guillermo
Resumen.
Tras diseñar un sistema interno de garantía de calidad se inició el proceso de implantación. Sin embargo, este proceso se ha dilatado en el tiempo y no se ha podido finalizar todavía. Es posible que muchos de los problemas con los que nos hemos encontrado sean fallos del sistema diseñado, que no fueron previstos por el centro ni detectados por los revisores externos. La discusión sobre nuestra experiencia, contrastándola con la de otros centros puede ser una herramienta valiosa para mejorar un sistema complejo.
Abstract.
After the quality system design, implementation was the second step. However, several difficulties caused the delay in the implementation process and the system is not yet finalized. It is possible that some of the problems in the process were due to a non appropriate design or evaluation of the quality system. In our opinion, the discussion about the experience, contrasted to the other centres’ experiences could help in the improvement of the system.
2017-06-16T08:50:36ZPérez Gracia, María de la VegaLópez López, JoséBuenestado Caballero, PabloGarcia-Alzórriz Pardo, Juan AntonioTorres Cámara, RicardoMartínez Sánchez, JoanVelasco Quesada, GuillermoResumen.
Tras diseñar un sistema interno de garantía de calidad se inició el proceso de implantación. Sin embargo, este proceso se ha dilatado en el tiempo y no se ha podido finalizar todavía. Es posible que muchos de los problemas con los que nos hemos encontrado sean fallos del sistema diseñado, que no fueron previstos por el centro ni detectados por los revisores externos. La discusión sobre nuestra experiencia, contrastándola con la de otros centros puede ser una herramienta valiosa para mejorar un sistema complejo.
Abstract.
After the quality system design, implementation was the second step. However, several difficulties caused the delay in the implementation process and the system is not yet finalized. It is possible that some of the problems in the process were due to a non appropriate design or evaluation of the quality system. In our opinion, the discussion about the experience, contrasted to the other centres’ experiences could help in the improvement of the system.