Alexandru Aldea

Using experimental data to reduce the single-building sigma of fragility curves: case study of the BRD tower in Bucharest, Romania

The lack of knowledge concerning modelling existing buildings leads to signifiant variability in fragility curves for single or grouped existing buildings. This study aims to investigate the uncertainties of fragility curves, with special consideration of the single-building sigma. Experimental data and simplified models are applied to the BRD tower in Bucharest, Romania, a RC building with permanent instrumentation. A three-step methodology is applied: (1) adjustment of a linear MDOF model for experimental modal analysis using a Timoshenko beam model and based on Anderson’s criteria, (2) computation of the structure’s response to a large set of accelerograms simulated by SIMQKE software, considering twelve ground motion parameters as intensity measurements (IM), and (3) construction of the fragility curves by comparing numerical interstory drift with the threshold criteria provided by the Hazus methodology for the slight damage state. By introducing experimental data into the model, uncertainty is reduced to 0.02 considering Sd (f1) as seismic intensity IM and uncertainty related to the model is assessed at 0.03. These values must be compared with the total uncertainty value of around 0.7 provided by the Hazus methodology.

Ground Types for Seismic Design in Romania

The paper presents an overview of available data concerning ground types for seismic design in Romania. A short overview of a ground information database created during BIGSEES Romanian project is presented. A comparison of shear wave velocity for 19 sites in Bucharest determined by PS logging measurements and by Wald topographic slope method is discussed. The paper reiterates the conclusion of a study regarding the Eurocode soil factor S derived from the Romanian seismic motions. The need for an enlarged database of in situ determined ground condition is underlined, at least at the location of seismic stations. Based on borehole-specific data (geotechnical properties, hydrologic factors) and velocity profiles, evaluations of soil liquefaction potential and related indices were performed by using empirical equations proposed in literature. The application of GIS tools provided a spatial distribution of liquefaction susceptibility of Quaternary alluvial sediments in Bucharest.

Toward the Seismic Evaluation of “Carol I” Royal Mosque in Constanța

Seismic protection of cultural heritage constructions is a priority in earthquake prone countries, due to their cultural, historical and touristic importance. The paper presents a first step toward the seismic evaluation of the “Carol I” Royal Mosque in Constanța, Romania: ambient vibration measurements and the assessment of the existing damage state induced by previous earthquakes and/or other actions (index R2 according to the Romanian code for seismic evaluation of existing buildings P100-3/2008). The mosque was built in 1910–1913 and has a masonry structure with a 26 m height reinforced concrete dome. It has an approximately 40 m height RC minaret and thus it is between the first civil constructions using reinforced concrete in Romania. The construction experienced the major earthquakes of 1940 (M W = 7.7) and 1977 (M W = 7.5) and several other medium size events originating from Vrancea subcrustal seismic source without significant damage. However, the long-term climatic aggression had a negative impact on the structure. Ambient vibration measurements were performed in the minaret. The results will be used for the proper calibration of the computational model for linear analysis.

The inter-relationships between urban dynamics and water resource and supply based on multitemporal analysis

The growth and concentration of population, housing and industry in urban and suburban areas in the continuous evolution of a city over time causes complex social, economic, and physical challenges. The population and its relationship with the use and development of the land and water is a critical issue of urban growth, and since ancient times land, water and man were directly involved in the human populations’ survival. Nevertheless the current potential of study over this relationship between urban growth, water supply, drainage and water resources conditions becomes more and more attractive due to the possibility to make use of the broader variety of information sources and technologies readily available in recent years, with emphasis on the open data and on the big data as primary sources. In this regard we present some new possibilities of analyses over the demographics, land use/land cover and water supply and conservation based on a study over a Romanian region of development (Bucharest-Ilfov). As urban development usually outgrows the existing water supply systems, the resolution consists in drilling new and deeper wells, building new water distribution pipelines, building longer aqueducts and larger reservoirs, or finding new sources and constructing completely new water supply systems, water supplies may evolve this way from a result into a cause and driver of urban growth. The evolution trends of the studied area was estimated based on the open satellite time-series imagery and remote sensing techniques by land use/land cover extraction and the identification of the changes in urbanization. The survey is mainly focused on the expansion of the water network in terms of areal, total length and number of connections correlated with the amount of water produced, consumed and lost within a supply zone. Some urban human activities including the industrial ones alter water resource by pollution, over pumping of groundwater, construction of dams and reservoirs. In areas of rapid growth the worse problems came from the inadequate amount of potable water, the continuous deterioration of water quality and the slow progress in the water resources management and supply. The effects of urban dynamics over the water use and sustainability deserves an increasing study over the recent history in order to provide for an optimal management of the interrelationships between them.

Dynamic Characteristics of a Tall Building Identified from Earthquake and Ambient Vibration Records

Abstract The paper presents the modal characteristics of a tall building in Bucharest (BRD-SG Tower) identified from earthquake and ambient vibration records. The building was built in the early 2000’s and has a reinforced concrete structure (inner shear wall tube and perimeter frames) with 3 underground stories, ground floor and 18 stories. The seismic instrumentation of the building consists of a seismic station with two triaxial acceleration sensors located at the top of the building (+69.6 m) and at the third basement (−9.3 m). The dynamic characteristics of the building are estimated from the seismic records from 23 earthquakes (with moment magnitudes MW between 3.7 and 6.0) that occurred during the period 2004÷2010. The results obtained from the earthquake records are compared with those obtained from 35 ambient vibration records from the period 2003 ÷ 2010.

Expected Direct Seismic Losses Assessment Using Gis. Case Study for Iaşi Municipality

Abstract Expected direct seismic losses assessment is performed on probabilistic basis using world-wide accepted methodologies for two study areas located in Iasi Municipality. The probabilistic assessment refers to the following issues: site-dependent seismic hazard, expected seismic response of buildings, seismic fragility of structures, expected seismic damage. The analysis of the spatial distribution of the existing building stock as well as the presentation of the results on expected direct seismic losses are performed using geographic information systems (GIS)