Articles de revista
http://hdl.handle.net/2117/478
20160206T15:14:06Z

Urban nonengineered buildings in Merida, Venezuela. Seismic performance and proposals for retrofit and for new construction
http://hdl.handle.net/2117/78991
Urban nonengineered buildings in Merida, Venezuela. Seismic performance and proposals for retrofit and for new construction
López Almansa, Francisco; Pujades Beneit, Lluís; Castillo, A.
The seismic risk for an informal settlement in Mérida (“La Milagrosa”) is qualitatively assessed and retrofit strategies are
proposed. The buildings in the settlement are thoroughly examined and four prototype buildings are chosen to represent
the vast majority of houses in “La Milagrosa”. The structural behavior of these buildings under gravity loads and seismic
actions is deeply analyzed; this study shows that the prototype buildings are unsafe for gravity loads, and that the seismic
demands largely exceed their capacity. Based on these conclusions, feasible retrofit strategies are proposed, together with
draft recommendations for new similar constructions. Earlier quantitative estimative appraisals show that the proposed
seismic strengthening measures can be very effective in reducing fatalities and economical losses, and are significantly
more costefficient than reconstructionbased approaches. These conclusions might be generalized to many nonengineered
urban areas in earthquakeprone regions of the developing world.
20151110T19:03:43Z
López Almansa, Francisco
Pujades Beneit, Lluís
Castillo, A.
The seismic risk for an informal settlement in Mérida (“La Milagrosa”) is qualitatively assessed and retrofit strategies are
proposed. The buildings in the settlement are thoroughly examined and four prototype buildings are chosen to represent
the vast majority of houses in “La Milagrosa”. The structural behavior of these buildings under gravity loads and seismic
actions is deeply analyzed; this study shows that the prototype buildings are unsafe for gravity loads, and that the seismic
demands largely exceed their capacity. Based on these conclusions, feasible retrofit strategies are proposed, together with
draft recommendations for new similar constructions. Earlier quantitative estimative appraisals show that the proposed
seismic strengthening measures can be very effective in reducing fatalities and economical losses, and are significantly
more costefficient than reconstructionbased approaches. These conclusions might be generalized to many nonengineered
urban areas in earthquakeprone regions of the developing world.

Fractal structure and predictive strategy of the daily extreme temperature residuals at Fabra Observatory (NE Spain, years 19172005)
http://hdl.handle.net/2117/78472
Fractal structure and predictive strategy of the daily extreme temperature residuals at Fabra Observatory (NE Spain, years 19172005)
Lana Pons, Francisco Javier; Burgueño, August; Serra de Larrocha, Carina; Martínez Santafé, Maria Dolors
A compilation of daily extreme temperatures recorded at the Fabra Observatory (Catalonia, NE Spain) since 1917 up to 2005 has permitted an exhaustive analysis of the fractal behaviour of the daily extreme temperature residuals, DTR, defined as the difference between the observed daily extreme temperature and the daily average value. The lacunarity characterises the lag distribution on the residual series for several thresholds. Hurst, H, and Hausdorff, Ha, exponents, together with the exponent beta of the decaying power law, describing the evolution of power spectral density with frequency, permit to characterise the persistence, antipersistence or randomness of the residual series. The selfaffine character of DTR series is verified, and additionally, they are simulated by means of fractional Gaussian noise, fGn. The reconstruction theorem leads to the quantification of the complexity (correlation dimension, mu*, and Kolmogorov entropy, kappa.) and predictive instability (Lyapunov exponents, lambda, and KaplanYorke dimension, DKY) of the residual series. All fractal parameters are computed for consecutive and independent segments of 5year lengths. This strategy permits to obtain a high enough number of fractal parameter samples to estimate time trends, including their statistical significance. Comparisons are made between results of predictive algorithms based on fGn models and an autoregressive autoregressive integrated moving average (ARIMA) process, with the latter leading to slightly better results than the former. Several dynamic atmospheric mechanisms and local effects, such as local topography and vicinity to the Mediterranean coast, are proposed to explain the complex and instable predictability of DTR series. The memory of the physical system (Kolmogorov entropy) would be attributed to the interaction with the Mediterranean Sea.
20151029T10:50:38Z
Lana Pons, Francisco Javier
Burgueño, August
Serra de Larrocha, Carina
Martínez Santafé, Maria Dolors
A compilation of daily extreme temperatures recorded at the Fabra Observatory (Catalonia, NE Spain) since 1917 up to 2005 has permitted an exhaustive analysis of the fractal behaviour of the daily extreme temperature residuals, DTR, defined as the difference between the observed daily extreme temperature and the daily average value. The lacunarity characterises the lag distribution on the residual series for several thresholds. Hurst, H, and Hausdorff, Ha, exponents, together with the exponent beta of the decaying power law, describing the evolution of power spectral density with frequency, permit to characterise the persistence, antipersistence or randomness of the residual series. The selfaffine character of DTR series is verified, and additionally, they are simulated by means of fractional Gaussian noise, fGn. The reconstruction theorem leads to the quantification of the complexity (correlation dimension, mu*, and Kolmogorov entropy, kappa.) and predictive instability (Lyapunov exponents, lambda, and KaplanYorke dimension, DKY) of the residual series. All fractal parameters are computed for consecutive and independent segments of 5year lengths. This strategy permits to obtain a high enough number of fractal parameter samples to estimate time trends, including their statistical significance. Comparisons are made between results of predictive algorithms based on fGn models and an autoregressive autoregressive integrated moving average (ARIMA) process, with the latter leading to slightly better results than the former. Several dynamic atmospheric mechanisms and local effects, such as local topography and vicinity to the Mediterranean coast, are proposed to explain the complex and instable predictability of DTR series. The memory of the physical system (Kolmogorov entropy) would be attributed to the interaction with the Mediterranean Sea.

Aftershock sequences of three seismic crises at southern California, USA, simulated by a cellular automata model based on selforganized criticality
http://hdl.handle.net/2117/78319
Aftershock sequences of three seismic crises at southern California, USA, simulated by a cellular automata model based on selforganized criticality
Monterrubio Velasco, Marisol; Lana Pons, Francisco Javier; Martínez Santafé, Maria Dolors
Several properties of aftershock series related to the main shocks of Landers, Northridge and Hector Mine (southern California, USA) are reproduced by the Dynamic Fiber Bundle Model, DFBM. Optimum values for the three parameters governing DFBM are determined by searching for the best agreement of real aftershock series properties and those of synthetic sequences generated by this model. The analysis of the model parameter values provides details on the underlying physical mechanism of the aftershock sequence generation. First, the ratio of seismic energy radiated as seismic waves and transferred as stressstrain to adjacent faults; second, the degree of stress heterogeneity reproducing the complex behavior of real aftershock series. Additionally, the results of simulations support the coexistence of two types of relaxation processes. One of them is associated with the wellknown modified Omori's (MO) law, which involves elapsed times between consecutive aftershocks monotonically increasing; the other is manifested by episodes of sudden stress release, with interevent times much shorter than those predicted by MO law. These episodes are assumed to be a consequence of the complex distribution of tectonic stresses and fault geometry. The first process is associated to events designed as leading aftershocks, LA. The second process generates series of events which are designed as cascades, CA. It is worth of mention that several properties concerning CAs can be reasonably related to critical changes on stress field along the simulation process.
20151027T11:12:24Z
Monterrubio Velasco, Marisol
Lana Pons, Francisco Javier
Martínez Santafé, Maria Dolors
Several properties of aftershock series related to the main shocks of Landers, Northridge and Hector Mine (southern California, USA) are reproduced by the Dynamic Fiber Bundle Model, DFBM. Optimum values for the three parameters governing DFBM are determined by searching for the best agreement of real aftershock series properties and those of synthetic sequences generated by this model. The analysis of the model parameter values provides details on the underlying physical mechanism of the aftershock sequence generation. First, the ratio of seismic energy radiated as seismic waves and transferred as stressstrain to adjacent faults; second, the degree of stress heterogeneity reproducing the complex behavior of real aftershock series. Additionally, the results of simulations support the coexistence of two types of relaxation processes. One of them is associated with the wellknown modified Omori's (MO) law, which involves elapsed times between consecutive aftershocks monotonically increasing; the other is manifested by episodes of sudden stress release, with interevent times much shorter than those predicted by MO law. These episodes are assumed to be a consequence of the complex distribution of tectonic stresses and fault geometry. The first process is associated to events designed as leading aftershocks, LA. The second process generates series of events which are designed as cascades, CA. It is worth of mention that several properties concerning CAs can be reasonably related to critical changes on stress field along the simulation process.

Evaluation of the GPR frequency spectra in asphalt pavement assessment
http://hdl.handle.net/2117/76524
Evaluation of the GPR frequency spectra in asphalt pavement assessment
Pedret Rodés, Josep; Pérez Gracia, María de la Vega; Martínez Reguero, Adriana Haydée
Ground penetrating radar (GPR) is frequently used in pavement assessments, mainly using the evaluation of wave travel times. However, GPR data provide further information that could be used in order to determine the inner conditions and characteristics about materials. In this paper, the possible analysis of the frequency spectrum of GPR signals is analysed and discussed. Several tests were carried out in a portion of a highway in two different stages of its service life. Results highlight the relationship between the shape of the spectrum and the frequency signature with the structure and conditions of the pavement.
20150826T11:49:36Z
Pedret Rodés, Josep
Pérez Gracia, María de la Vega
Martínez Reguero, Adriana Haydée
Ground penetrating radar (GPR) is frequently used in pavement assessments, mainly using the evaluation of wave travel times. However, GPR data provide further information that could be used in order to determine the inner conditions and characteristics about materials. In this paper, the possible analysis of the frequency spectrum of GPR signals is analysed and discussed. Several tests were carried out in a portion of a highway in two different stages of its service life. Results highlight the relationship between the shape of the spectrum and the frequency signature with the structure and conditions of the pavement.

Application of particle motion technique to structural modal identification of heritage buildings
http://hdl.handle.net/2117/28420
Application of particle motion technique to structural modal identification of heritage buildings
Caselles Magallón, Josep Oriol; Martínez, Guillermo; Clapes Boixader, Jaime; Roca Fabregat, Pedro; Pérez Gracia, María de la Vega
Determining the behavior of a structure estimated by means of finite elements analysis requires not only an indepth knowledge of its geometry and dynamic properties but also an experimental validation to corroborate the adequacy of the characteristics of the structure. Most of the current structural identification techniques are based on linear methods that call for many measurement points
and/or a relative simple structure. Complex structures are somewhat still an unexplored field due to the difficulties with the finite element method and the experimental corroboration of its results. This study presents the use of particle motion computation applied to each structural vibration mode to improve the identification of its dynamic properties, and its application to the Gothic Cathedral of Palma de Majorca (Spain).
20150626T08:12:41Z
Caselles Magallón, Josep Oriol
Martínez, Guillermo
Clapes Boixader, Jaime
Roca Fabregat, Pedro
Pérez Gracia, María de la Vega
Determining the behavior of a structure estimated by means of finite elements analysis requires not only an indepth knowledge of its geometry and dynamic properties but also an experimental validation to corroborate the adequacy of the characteristics of the structure. Most of the current structural identification techniques are based on linear methods that call for many measurement points
and/or a relative simple structure. Complex structures are somewhat still an unexplored field due to the difficulties with the finite element method and the experimental corroboration of its results. This study presents the use of particle motion computation applied to each structural vibration mode to improve the identification of its dynamic properties, and its application to the Gothic Cathedral of Palma de Majorca (Spain).

Nanozonation in dense cities : testing a combined methodology in Barcelona City (Spain)
http://hdl.handle.net/2117/28414
Nanozonation in dense cities : testing a combined methodology in Barcelona City (Spain)
Salinas Naval, Víctor; Caselles Magallón, Josep Oriol; Pérez Gracia, María de la Vega; Santos Assunçao, Sonia; Clapes Boixader, Jaime; Pujades Beneit, Lluís; González Drigo, José Ramón; Canas Torres, José Antonio; Martínez Sánchez, Joan
Microzonation is widely used in seismic risk evaluations to define the predominant period values, which are usually associated with extended areas of a few hundred meters. However, the representative values corresponding to these areas are obtained from few measurements in each area. Thereby, results are accurate only in the case of depthdependent soils. However, not detected narrow and sharp lateral changes in soil are potentially the cause of imprecision and could be a source of specific errors. This article aims to present several tests conducted in order to emphasise the importance of accurate selection of points, to underscore the necessity of more precise and detailed evaluations, and to suggest a possible methodology to select the most appropriate data acquisition points. Results highlight the need to divide microzonation areas into smaller zones for a precise evaluation in locations where sudden changes in soil characteristics exist. Therefore, in such sites the requirement of nanozonation appears; defining zones with the same soil response. Distance between vibration measurements could be the main problem for nanozonation; data acquisition in areas with irregular geology can be time consuming when a precise analysis is required. In the most complicated environments or in dense cities, it could even be unfeasible. Consequently, it is necessary to establish a functional methodology to adequately distribute the measurement points throughout the area. On this occasion, three sites in Barcelona city were studied. This city is surrounded by mountains at NW, W, and S, and by the Mediterranean Sea at N and E. As a consequence, the shallow geology is characterized by many paleochannels and streams that are currently buried. These geological structures most likely affect the soil response maps, including nanozonation.
20150626T06:19:38Z
Salinas Naval, Víctor
Caselles Magallón, Josep Oriol
Pérez Gracia, María de la Vega
Santos Assunçao, Sonia
Clapes Boixader, Jaime
Pujades Beneit, Lluís
González Drigo, José Ramón
Canas Torres, José Antonio
Martínez Sánchez, Joan
Microzonation is widely used in seismic risk evaluations to define the predominant period values, which are usually associated with extended areas of a few hundred meters. However, the representative values corresponding to these areas are obtained from few measurements in each area. Thereby, results are accurate only in the case of depthdependent soils. However, not detected narrow and sharp lateral changes in soil are potentially the cause of imprecision and could be a source of specific errors. This article aims to present several tests conducted in order to emphasise the importance of accurate selection of points, to underscore the necessity of more precise and detailed evaluations, and to suggest a possible methodology to select the most appropriate data acquisition points. Results highlight the need to divide microzonation areas into smaller zones for a precise evaluation in locations where sudden changes in soil characteristics exist. Therefore, in such sites the requirement of nanozonation appears; defining zones with the same soil response. Distance between vibration measurements could be the main problem for nanozonation; data acquisition in areas with irregular geology can be time consuming when a precise analysis is required. In the most complicated environments or in dense cities, it could even be unfeasible. Consequently, it is necessary to establish a functional methodology to adequately distribute the measurement points throughout the area. On this occasion, three sites in Barcelona city were studied. This city is surrounded by mountains at NW, W, and S, and by the Mediterranean Sea at N and E. As a consequence, the shallow geology is characterized by many paleochannels and streams that are currently buried. These geological structures most likely affect the soil response maps, including nanozonation.

Probabilistic seismic damage assessment of RC buildings based on nonlinear dynamic analysis
http://hdl.handle.net/2117/28218
Probabilistic seismic damage assessment of RC buildings based on nonlinear dynamic analysis
Vargas Alzate, Yeudy Felipe; Pujades Beneit, Lluís; Barbat Barbat, Horia Alejandro; Hurtado Gómez, Jorge Eduardo
The incremental dynamic analysis is a powerful tool for evaluating the seismic vulnerability and risk of buildings. It allows calculating the global damage of structures for different PGAs and representing this result by means of damage curves. Such curves are used by many methods to obtain seismic risk scenarios at urban level. Even if the use of this method in a probabilistic environment requires a relevant computational effort, it should be the reference method for seismic risk evaluation. In this article we propose to assess the seismic expected damage by using nonlinear dynamic analysis. We will obtain damage curves by means of the incremental dynamic analysis combined with the damage index of Park & Ang. The uncertainties related to the mechanical properties of the materials and the seismic action will be considered. The probabilistic damage curves obtained can be used to calculate not only seismic risk scenarios at urban level, but also to estimate economic losses.
20150608T14:46:58Z
Vargas Alzate, Yeudy Felipe
Pujades Beneit, Lluís
Barbat Barbat, Horia Alejandro
Hurtado Gómez, Jorge Eduardo
The incremental dynamic analysis is a powerful tool for evaluating the seismic vulnerability and risk of buildings. It allows calculating the global damage of structures for different PGAs and representing this result by means of damage curves. Such curves are used by many methods to obtain seismic risk scenarios at urban level. Even if the use of this method in a probabilistic environment requires a relevant computational effort, it should be the reference method for seismic risk evaluation. In this article we propose to assess the seismic expected damage by using nonlinear dynamic analysis. We will obtain damage curves by means of the incremental dynamic analysis combined with the damage index of Park & Ang. The uncertainties related to the mechanical properties of the materials and the seismic action will be considered. The probabilistic damage curves obtained can be used to calculate not only seismic risk scenarios at urban level, but also to estimate economic losses.

Preventive intervention in a group of building located in the histotic centre of Manresa (Barcelona)
http://hdl.handle.net/2117/28166
Preventive intervention in a group of building located in the histotic centre of Manresa (Barcelona)
Díaz Gómez, César; Cornadó Bardón, Còssima; Griera Cura, Antoni; Caselles Magallón, Josep Oriol; Alegre Heitzmann, Vicente; Santamaria Garcia, Pere
The preservation of old downtowns has become a necessity of growing interest. New urban policies have been approved in different countries in order to revive the old city centers and make them economically sustainable. In this global trend, the municipality of Manresa (Barcelona) developed an important urban planning operation in the old district that included the demolition of a group of existing buildings and the construction of a new modern one in close proximity to a group of old residential buildings which are cultural heritage of the city. As a consequence, specific areas of risk were generated which lead to the adoption of precautionary measures to ensure safety.
This paper presents the preliminary analysis, diagnostics and monitoring carried out on this group of heterogeneous old buildings, as well as the results and precautionary measures taken to ensure their safety. The paper also provides a translatable methodology that combines qualitative and quantitative aspects.
20150603T12:33:08Z
Díaz Gómez, César
Cornadó Bardón, Còssima
Griera Cura, Antoni
Caselles Magallón, Josep Oriol
Alegre Heitzmann, Vicente
Santamaria Garcia, Pere
The preservation of old downtowns has become a necessity of growing interest. New urban policies have been approved in different countries in order to revive the old city centers and make them economically sustainable. In this global trend, the municipality of Manresa (Barcelona) developed an important urban planning operation in the old district that included the demolition of a group of existing buildings and the construction of a new modern one in close proximity to a group of old residential buildings which are cultural heritage of the city. As a consequence, specific areas of risk were generated which lead to the adoption of precautionary measures to ensure safety.
This paper presents the preliminary analysis, diagnostics and monitoring carried out on this group of heterogeneous old buildings, as well as the results and precautionary measures taken to ensure their safety. The paper also provides a translatable methodology that combines qualitative and quantitative aspects.

Parametric model for capacity curves
http://hdl.handle.net/2117/28071
Parametric model for capacity curves
Pujades Beneit, Lluís; Vargas Alzate, Yeudy Felipe; Barbat Barbat, Horia Alejandro; González Drigo, José Ramón
A parametric model for capacity curves and capacity spectra is proposed. The capacity curve is considered to be composed of a linear part and a nonlinear part. The normalized nonlinear part is modelled bymeans of a cumulative lognormal function. Instead, the cumulative Beta function can be used. Moreover, this new conceptualization of the capacity curves allows defining stiffness and energy functions relative to the total energy loss and stiffness degradation at the ultimate capacity point. Based on these functions, a new damage index is proposed and it is shown that this index, obtained from nonlinear static analysis, is compatible with the Park and Ang index obtained from dynamic analysis. This capacity based damage index allows setting up a fragility model. Specific reinforced concrete buildings are used to illustrate the adequacy of the capacity, damage and fragility models. The usefulness of the models here proposed is highlighted showing how the parametric model is representative for a family of capacity curves having the same normalized nonlinear part and how important variables can be tabulated as empirical functions of the two main parameters defining the capacity model. The availability of this new mathematical model may be a powerful tool for current earthquake engineering research, especially in seismic risk assessments at regional scale and in probabilistic approaches where massive computations are needed.
20150527T14:44:12Z
Pujades Beneit, Lluís
Vargas Alzate, Yeudy Felipe
Barbat Barbat, Horia Alejandro
González Drigo, José Ramón
A parametric model for capacity curves and capacity spectra is proposed. The capacity curve is considered to be composed of a linear part and a nonlinear part. The normalized nonlinear part is modelled bymeans of a cumulative lognormal function. Instead, the cumulative Beta function can be used. Moreover, this new conceptualization of the capacity curves allows defining stiffness and energy functions relative to the total energy loss and stiffness degradation at the ultimate capacity point. Based on these functions, a new damage index is proposed and it is shown that this index, obtained from nonlinear static analysis, is compatible with the Park and Ang index obtained from dynamic analysis. This capacity based damage index allows setting up a fragility model. Specific reinforced concrete buildings are used to illustrate the adequacy of the capacity, damage and fragility models. The usefulness of the models here proposed is highlighted showing how the parametric model is representative for a family of capacity curves having the same normalized nonlinear part and how important variables can be tabulated as empirical functions of the two main parameters defining the capacity model. The availability of this new mathematical model may be a powerful tool for current earthquake engineering research, especially in seismic risk assessments at regional scale and in probabilistic approaches where massive computations are needed.

A new steel framing system for seismic protection of timber platform frame buildings: implementation with hysteretic energy dissipators
http://hdl.handle.net/2117/25182
A new steel framing system for seismic protection of timber platform frame buildings: implementation with hysteretic energy dissipators
López Almansa, Francisco; Segués Aguasca, Edgar; Rodríguez Cantalapiedra, Inma
This paper describes a new seismic protection system for timber platform frame buildings, either for new construction or retrofit. The system consists in connecting the timber frame to a steel structure that includes hysteretic energy dissipators designed to absorb most of the seismic input energy thus protecting the timber frame and the other steel members; alternatively, the system might use other types of dissipative devices. The steel structure consists of four steel stacks (located at each of the four façades) and steel collectors embracing each slab; the stacks and the collectors are connected, at each floor level, through the energy dissipators. The steel structure is selfsupporting, that is, the timber frame is not affected by horizontal actions and can be designed without accounting for any seismic provision; in turn, the steel members do not participate in the main loadcarrying system. The timbersteel interface is designed to avoid any stress concentration in the transfer of horizontal forces and to guarantee that the yielding of the dissipators occurs prior
to any timber failure. The energy dissipation capacity of the suggested system is discussed, and an application example on a sixstory timber building is presented; this case corresponds to highly demanding conditions because of the relatively large building height and weight, the high local seismicity, and the soft soil condition. This research belongs to a wider project aiming to promote the structural use of timber by improving the seismic capacity of wooden buildings; this research includes experiments and advanced numerical simulation. Copyright © 2014 John Wiley & Sons, Ltd.
20150108T16:27:15Z
López Almansa, Francisco
Segués Aguasca, Edgar
Rodríguez Cantalapiedra, Inma
This paper describes a new seismic protection system for timber platform frame buildings, either for new construction or retrofit. The system consists in connecting the timber frame to a steel structure that includes hysteretic energy dissipators designed to absorb most of the seismic input energy thus protecting the timber frame and the other steel members; alternatively, the system might use other types of dissipative devices. The steel structure consists of four steel stacks (located at each of the four façades) and steel collectors embracing each slab; the stacks and the collectors are connected, at each floor level, through the energy dissipators. The steel structure is selfsupporting, that is, the timber frame is not affected by horizontal actions and can be designed without accounting for any seismic provision; in turn, the steel members do not participate in the main loadcarrying system. The timbersteel interface is designed to avoid any stress concentration in the transfer of horizontal forces and to guarantee that the yielding of the dissipators occurs prior
to any timber failure. The energy dissipation capacity of the suggested system is discussed, and an application example on a sixstory timber building is presented; this case corresponds to highly demanding conditions because of the relatively large building height and weight, the high local seismicity, and the soft soil condition. This research belongs to a wider project aiming to promote the structural use of timber by improving the seismic capacity of wooden buildings; this research includes experiments and advanced numerical simulation. Copyright © 2014 John Wiley & Sons, Ltd.