Seismic Vulnerability Of Buildings Research Articles

Applications of a GIS-based geotechnical tool to assess spatial earthquake hazards in an urban area

A geotechnical information system (GTIS) was constructed within a spatial geographic information system (GIS) framework to reliably predict geotechnical information and accurately estimate site effects at Gyeongju, an urban area in South Korea. The system was built based on both collected and performed site investigation data in addition to acquired geo-knowledge data. Seismic zoning maps were constructed using the site period (TG) and mean shear wave velocity to a depth of 30 m (VS30), and these maps were presented as a regional strategy to mitigate earthquake-induced risks in the study area. In particular, the TG distribution map indicated the susceptibility to ground motion resonance in periods ranging from 0.2 to 0.5 s and the corresponding seismic vulnerability of buildings with two to five stories. Seismic zonation of site classification according to VS30 values was also performed to determine the site amplification coefficients for seismic design and seismic performance evaluation at any site and administrative subunit in the study area. In addition, we investigated the site effects according to subsurface and surface ground irregularities at Gyeongju by seismic response analyses in time domains based on both two- and three-dimensional spatial finite element models, which were generated using spatial interface coordinates between geotechnical subsurface layers predicted by the GTIS. This practical study verified that spatial GIS-based geotechnical information can be a very useful resource in determining how to best mitigate seismic hazards, particularly in urban areas.

Ambient noise measurements on soil and buildings

This special issue of the Bulletin of Earthquake Engineering contains 13 paper devoted to ambient noise measurements on soil and buildings. Five of the paper are the outcome of a NATO Science for Peace Project named “Assessment of Seismic Site Amplification and Seismic Building Vulnerability in the FYR Macedonia, Croatia and Slovenia” whose aim was to bring together geologist, seismologist and engineers and perform field measurement of dynamic characteristics of large sets of buildings and their foundation soils, trying to integrate interpreted measurement data into microzonation maps of urban areas. Around this core I collected other papers by authors that were invited to participate to project meetings and to another initiative that stemmed out of the project, that is a NATO Advanced Research Workshop entitled “Increasing Seismic Safety by Combining Engineering Technologies and Seismological Data”. The ARW produced also a book (Mucciarelli et al. 2009) that provided a detailed state of the art and new ideas for the future, making it a complement to this special issue devoted to original experimental and numerical results. Two papers of this issue were later contributed by authors that became aware of the initiative and decided that their work was fit in this framework, confirming the ongoing interest on this subject. The papers cover issues starting from the classical use of microtremors to study soil properties (Herak et al. 2010; Gosar and Lenart 2010) consider new theoretical models of seismic noise (Albarello and Lunedei 2010), discuss the stability of noise measurement to invert velocity profiles (Endrun et al. 2010) and include the study of possible resonance between soil and structures (Gosar et al. 2010). To this last aim, the knowledge of the dynamic properties of building is essential. It is very interesting that two independent papers, one from the SfP project (Gallipoli 2010) and one submitted later (Oliveira and Navarro 2010) came to the same conclusion analysing different sets of building in different countries: the period

VULNERABILITY OF BUILDINGS TO LONG DISTANCE EARTHQUAKES FROM SUMATRA

This study focuses on seismic vulnerability of shear wall – frame buildings in Singapore when they are subjected to far field effects of earthquakes in Sumatra. For this purpose, the demand curve was obtained based on the accelerograms of bedrock motions due to the worst earthquake scenario in Sumatra, and soil profiles of the selected sites. The recent two strong earthquakes in Sumatra were considered when the design earthquake was identified. On the other hand, the capacity curve was determined by a reliable and elegant analytical model validated by experimental results. By comparing the demand curve and capacity curve, seismic vulnerability of buildings is evaluated through a case study of a 25 story shear wall-frame building, representing the typical high rise building in Singapore. The case study reveals that high rise buildings in Singapore may suffer damages due to the worst earthquake scenario.

Seismic site effect estimation in the city of Rabat (Morocco)

This study is based on a site survey carried out in the capital city of Morocco, Rabat. For this aim, we used a technique based on the recording and processing of seismic ambient noise to characterize local geological conditions in terms of the dynamic response of soil during earthquakes. This technique consists of an assessment of the spectral ratio of the horizontal to vertical components of microtremors recorded at the surface during a few minutes, and allows determination of the fundamental period and the maximum amplification factor at the site of measurement. We applied this technique in the city of Rabat to obtain distribution maps of dominant periods and amplification factors assessed in more than 250 sites. In order to discuss the results of this study, we used the information available in this zone about the lithology and topography to correlate the obtained values of dominant periods and amplification factors with the ground conditions. Finally, we established a microzoning map of the city of Rabat based on the contours of dominant periods. The microzoning map established in this study can be used by engineers and decision makers for urban and land use planning and also as a guide in reduction of the seismic vulnerability of buildings.

Seismic vulnerability estimation of the building considering seismic environment and local site condition

A procedure is developed to incorporate seismic environment and site condition into the framework of seismic vulnerability estimation of building to consider the effects of the severity and/or frequency content of ground motion due to seismic environment and site condition. Localized damage distribution can be strongly influenced by seismic environment and surficial soil conditions and any attempt to quantify seismic vulnerability of building should consider the impact of these effects. The seismic environment, site and structure are coupled to estimate damage probability distribution among different damage states for the building. Response spectra at rock site are estimated by probabilistic seismic hazard assessment approach. Based upon engineering representations of soil and amplifying spectral coordinates, frequency content and severity of ground motion are considered. Furthermore the impacts of severity and/or frequency of ground motion effects are considered to estimate the seismic response of reinforced concrete building and damage probability distribution for the building. In addition, a new method for presenting the distribution of damage is developed to express damage probability distribution for the building for different seismic hazard levels.

Probabilistic neural networks for seismic damage mechanisms prediction

The procedure commonly employed to assess the seismic vulnerability of buildings uses simplified qualitative and quantitative observations obtained from the measured data entered into report forms. In Italy, the data sheets adopted by the National Defence Group against Earthquakes (Gruppo Nazionale per la Difesa dai Terremoti-GNDT) play a unifying and reference role. This paper proposes a method for the processing of the data contained in such report forms which is based on probabilistic neural networks producing a Bayesian classification. The final goal is to exploit the fundamental learning and generalization capabilities of neural networks to obtain an estimate of the vulnerability of structural systems. In particular, the aim is to be able to predict the damage mechanisms which may be triggered in the macro-elements of public worship buildings.