The paper presents results from an experimental program implemented for three representative buildings in Bucharest metropolitan area and aimed to explore the potential of various dynamic identification methods in providing information about building state changes. The objective is to establish reference values of potential use in rapid earthquake damage detection systems. Each of the selected buildings was designed according to a different seismic code, in force at the time of its construction. The methods employed for this study were: the analysis of Fourier spectra, the analysis of the transfer function and the random decrement technique. To validate the results, the fundamental periods of vibration determined experimentally were compared with the corresponding values predicted by the empirical formulas specified in the corresponding editions of the Romanian seismic code. The results revealed consistent values for both the fundamental period and the damping ratio of the buildings. However, small variations of the two parameters were identified, depending on the time the recordings were performed, noise sources and levels and building occupancy. The results, in terms of validated data on the dynamic characteristics of Romanian building stock and of assessment of methods performance, add up to the information pool needed for the development of countrywide pre- and post-earthquake assisted decision tools.

The accurate estimation of plastic rotational capacity in reinforced concrete (RC) elements is essential for performance-based seismic design and structural safety assessments. In this study, an extensive experimental database, comprising 258 rectangular and 151 circular RC column specimens, was compiled based on open data available and used to train machine learning models for predicting this parameter. Three algorithms, i.e. Support Vector Regression (SVR), Random Forest (RF), and Extreme Gradient Boosting (XGBoost), were implemented and optimized using grid search within a nested cross-validation framework. The predictive performance was evaluated by averaging the coefficient of determination (R²) across five outer folds, while final accuracy was assessed on the test set using both R², the Mean Absolute Error (MAE), the root mean squared error (RMSE), and the mean absolute percentage error (MAPE). Model interpretability was improved using SHAP (SHapley Additive exPlanations) analysis, which quantified the influence of input parameters on predictions. Finally, a stacking ensemble model was developed to integrate the strengths of the individual regressors. The proposed methodology demonstrates increased accuracy and robustness in predicting the plastic rotational capacity of both circular and rectangular RC columns, providing a valuable tool for seismic assessment and structural reliability analysis.

Traditional houses represent landmarks of local cultures all over the world. In seismically prone countries, the traditional timber frames with different types of infills have shown quite good earthquake resilience, an essential feature considering their large number, their simplicity and their reduced cost, owing to the use of local materials and workmanship. In fact, their seismic behavior fostered the interest in further scientific research, including that addressing engineering aspects. Because of their diversity in layout and detailing, noticeable even among houses in the same area, developing general methods to preserve and strengthen such buildings is still a difficult task. This paper presents an overview of the traditional building construction techniques in Romania, focusing on the structural configuration and detailing of the so-called paiantă houses. Largely used all over the country, these houses have shown that they can generally withstand earthquakes at least without collapsing and, most frequently, with minor or repairable damage. Their preservation is nowadays a major challenge, as they are being gradually either demolished and replaced, or retrofitted by using invasive techniques. Their cultural and heritage value is undeniable, and there are still many things to be learned from the past craftsmanship and re-valuated in the future. Three case studies of rural buildings located in different areas of the country were chosen among the most widespread paiantă versions, and comprehensive engineering assessments were conducted to identify their detailing and degradations. Based on the most common degradations, the conclusions drawn from this study can be used to substantiate further research aimed at selecting the most appropriate construction and strengthening techniques.