Maria-Victoria Requena-Garcia-Cruz

Bio: Maria-Victoria Requena-Garcia-Cruz is an academic researcher from University of Seville. The author has contributed to research in topics: Structural engineering & Retrofitting. The author has an hindex of 3, co-authored 10 publications receiving 24 citations.

An index-based method for evaluating seismic retrofitting techniques. Application to a reinforced concrete primary school in Huelva.

Abstract: A project named PERSISTAH (Projetos de Escolas Resilientes aos SISmos no Territorio do Algarve e de Huelva, in Portuguese) is being developed. It aims to cooperatively assess and improve the seismic vulnerability of primary schools in the Algarve (Portugal) and Huelva (Spain). A large number of schools have to be analysed. In order to determine which seismic retrofitting technique is optimal, an index-based method is presented in this paper. It considers three parameters: first, the efficiency of the seismic retrofitting technique in relation to the structural improvement obtained; second, the cost of the implementation of the retrofitting technique; and third, the architectural impact. It should be mentioned that a specific measurement for each solution according to its geometry has been performed. Also, coefficients to consider the singularities of each analysis and the importance of the parameters (number of buildings, typology, available funds, etc.) in the study are considered. The most representative primary school of Huelva has been chosen to test the index-based method. The most suitable retrofitting techniques for this type of buildings have been tested. The retrofitting technique which most increased the seismic performance has been the addition of X and V bracings within the building’s bays. Furthermore, the analyses have revealed that adding the retrofitting elements in the most vulnerable direction of the building provides a high efficiency. The results have also shown that implementing techniques of lower architectural impact gives acceptable results. The analysis of the mean damage level index has shown that the building would experiment a severe damage. All the retrofitting techniques applied have reduced it, at least, up to moderate damage. Finally, it should be noted that the position of the retrofitting elements is also paramount for providing an optimal retrofitting.

Seismic capacity and vulnerability assessment considering ageing effects: case study—three local Portuguese RC buildings

Abstract: A high percentage of reinforced concrete (RC) buildings in Portugal were designed and built before the introduction of modern seismic codes. This research aims to assess the seismic capacity and vulnerability of RC buildings in the city of Lisbon. For that purpose, nonlinear static procedures have been used and fragility curves have been developed. These buildings are reaching the end of their nominal life. Therefore, ageing effects have been taken into account, as well as the presence of smooth rebar. To do so, a sensitivity analysis has been performed by considering the chloride-induced corrosion of the reinforcement steel rebar and the degradation of the concrete cover. To illustrate the effects of ageing and the procedure adopted for the seismic fragility assessment of old RC structures, three RC buildings with masonry infills have been selected as case studies. They were all built between 1960 and 1980, and they are representative of the current building stock in Lisbon. The seismic capacity of the buildings has been determined by means of nonlinear static analyses of three-dimensional numerical models. The N2 method and its extended version have been considered to determine the target displacement. The seismic safety of the buildings has been estimated in terms of the demand/capacity ratio for each vertical structural element (columns and walls) according to the bending and the shear failures. Then, a set of fragility curves has been developed for all buildings to represent the probability of RC elements reaching or exceeding the significant damage limit state. Results have shown that the concrete strength degradation has had more influence than reduction of the rebar diameter in the seismic capacity. When considering steel corrosion, it has been demonstrated that the corrosion rate has reduced the capacity more than the time of exposure. It can be concluded that ageing affects the seismic behaviour of RC structures, increasing the vulnerability of these buildings.

Optimal seismic retrofitting techniques for URM school buildings located in the southwestern Iberian peninsula.

Abstract: This paper aims to study different seismic retrofitting techniques to test the reduction of the seismic vulnerability of unreinforced masonry buildings. Three techniques have been considered in a case study: adding steel or carbon fibre reinforced polymer grids in the walls and steel encirclements in the openings. The performance-based method has been used to that purpose. Nonlinear static analyses have been performed to obtain the capacity and fragility curves, the performance point and the damage level states. Moreover, an analysis of the cost-benefit ratio has been carried out. Results have shown that the three techniques have produced considerable improvements. The addition of encirclements has reduced the deformation resulting in a slight increase of the structure’s stiffness. Adding steel grids has produced the maximum peak strength increase while adding polymer grids has produced the largest ultimate displacements. Adding encirclement has had the best cost-benefit ratio.

A Hybrid ANN-GA Model for an Automated Rapid Vulnerability Assessment of Existing RC Buildings

Abstract: Determining the risk priorities for the building stock in highly seismic-prone regions and making the final decisions about the buildings is one of the essential precautionary measures that needs to be taken before the earthquake. This study aims to develop an Artificial Neural Network (ANN)-based model to predict risk priorities for reinforced-concrete (RC) buildings that constitute a large part of the existing building stock. For this purpose, the network parameters in the network structure have been optimized by establishing a hybrid structure with the Genetic Algorithm (GA). As a result, the ANN model can make accurate predictions with maximum efficiency. The suggested ANN model is a feedforward back-propagation network model. It aims to predict the risk priorities for 329 RC buildings in the most successful way, for which the performance score was calculated using the Turkey Rapid Evaluation Method (2013). In this paper, a GA-ANN hybrid model was implemented in which the ANN, using the most successful gene revealed by the model, produced successful results in calculating the performance score. In addition, the required input parameters for obtaining more efficient results in solving such a problem and the parameters that need to be used in establishing such an ANN network structure have been optimized. With the help of such a model, the operation process will be eliminated. The created hybrid model was 98% successful in determining the risk priority in RC buildings.

Temperature Effects on Vibration-Based Damage Detection of a Reinforced Concrete Slab

Abstract: To study the variations in modal properties of a reinforced concrete (RC) slab (such as natural frequencies, mode shapes and damping ratios) under the influence of ambient temperature, a laboratory RC slab is monitored for over a year, the simple linear regression (LR) and autoregressive with exogenous input (ARX) models between temperature and frequencies are established and validated, and a damage identification based on particle swarm optimization (PSO) is utilized to detect the assumed damage considering temperature effects. Firstly, the vibration testing is performed for one year and the variations of natural frequencies, mode shapes and damping ratios under different ambient temperatures are analyzed. The obtained results show that the change of ambient temperature causes a major change of natural frequencies, which, on the contrary, has little effect on damping ratios and modal shapes. Secondly, based on a theoretical derivation analysis of natural frequency, the models are determined from experimental data on the healthy structure, and the functional relationship between temperature and elastic modulus is obtained. Based on the monitoring data, the LR model and ARX model between structural elastic modulus and ambient temperature are acquired, which can be used as the baseline of future damage identification. Finally, the established ARX model is validated based on a PSO algorithm and new data from the assumed 5% uniform damage and 10% uniform damage are compared with the models. If the eigenfrequency exceeds the certain confidence interval of the ARX model, there is probably another cause that drives the eigenfrequency variations, such as structural damage. Based on the constructed ARX model, the assumed damage is identified accurately.

Seismic capacity and vulnerability assessment considering ageing effects: case study—three local Portuguese RC buildings

Abstract: A high percentage of reinforced concrete (RC) buildings in Portugal were designed and built before the introduction of modern seismic codes. This research aims to assess the seismic capacity and vulnerability of RC buildings in the city of Lisbon. For that purpose, nonlinear static procedures have been used and fragility curves have been developed. These buildings are reaching the end of their nominal life. Therefore, ageing effects have been taken into account, as well as the presence of smooth rebar. To do so, a sensitivity analysis has been performed by considering the chloride-induced corrosion of the reinforcement steel rebar and the degradation of the concrete cover. To illustrate the effects of ageing and the procedure adopted for the seismic fragility assessment of old RC structures, three RC buildings with masonry infills have been selected as case studies. They were all built between 1960 and 1980, and they are representative of the current building stock in Lisbon. The seismic capacity of the buildings has been determined by means of nonlinear static analyses of three-dimensional numerical models. The N2 method and its extended version have been considered to determine the target displacement. The seismic safety of the buildings has been estimated in terms of the demand/capacity ratio for each vertical structural element (columns and walls) according to the bending and the shear failures. Then, a set of fragility curves has been developed for all buildings to represent the probability of RC elements reaching or exceeding the significant damage limit state. Results have shown that the concrete strength degradation has had more influence than reduction of the rebar diameter in the seismic capacity. When considering steel corrosion, it has been demonstrated that the corrosion rate has reduced the capacity more than the time of exposure. It can be concluded that ageing affects the seismic behaviour of RC structures, increasing the vulnerability of these buildings.