Earthquake Spectra (EARTHQ SPECTRA )

Publisher: Earthquake Engineering Research Institute


Earthquake Spectra Online (EQS), The Professional Journal of the Earthquake Engineering Research Institute serving professionals in civil, geotechnical, mechanical and structural engineering, geology, seismology, architecture, city planning, public administration, and social science concerned with earthquake hazard reduction.

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    Earthquake Spectra website
  • Other titles
    Earthquake reconnaissance report., Reconnaissance report., Earthquake spectra
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    Periodical, Internet resource
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    Journal / Magazine / Newspaper, Internet Resource

Publications in this journal

  • Earthquake Spectra 12/2014; 30(4):1427–1448.
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    ABSTRACT: This paper investigates the response of lead rubber bearings (LRBs) under bidirectional earthquake excitations when lead core heating effect is of concern. For this purpose, series of nonlinear response history analyses were conducted with a bilinear force-deformation relation for LRBs. In the considered bilinear representation, the strength of LRBs deteriorates due to lead core heating under cyclic motions. Response of LRBs was studied in terms of maximum isolator displacements (MIDs) and maximum lead core temperature as a function of isolator characteristics (characteristic strength to weight ratio, Q/W, and post-yield isolation period, T). Nonlinear response history analyses were performed using two sets of ground motions clustered according to their soil classifications. To quantify the interacted effects of coupled analysis and lead core heating on MID, unidirectional analyses were also performed. Furthermore, the efficacy of equivalent lateral force (ELF) procedure in estimating the MID of LRBs was also tested for the cases in which temperature dependent behavior of LRBs was considered. The results demonstrate that the temperature rises in the lead core of LRBs in bidirectional analyses are approximately 50% higher than that of unidirectional ones. It decreases with increasing Q/W ratio and T. It is also revealed that ELF procedure gives close estimations for MID with some overestimation even for temperature dependent behavior of LRBs.
    Earthquake Spectra 12/2014;
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    ABSTRACT: On May 20, 2012 a M5.9 earthquake hit the Emilia-Romagna Region, in Northern Italy. Although of rather moderate magnitude, the quake affected an area up to 17 km from the epicenter with severe damage and collapse of several warehouses. Widespread liquefaction phenomena were observed, such as sand boils and ground failures. Presented herein are the outcomes of a geotechnical post-earthquake reconnaissance survey conducted a week after the main shock in Sant'Agostino, a municipality near Ferrara, which was severely affected by the ground shaking. The presented findings add new liquefaction case records induced by a moderate earthquake in the Italian historical database. Non-invasive, seismic geophysical tests were carried out at 4 sites in the area of Sant'Agostino during the post-earthquake reconnaissance survey for near-surface geotechnical characterization. Preliminary assessment of liquefaction susceptibility has been carried out using post-earthquake field measurements at the 4 sites. Predictions based on standard, state of the practice empirical correlations are consistent with the observed liquefaction phenomena.
    Earthquake Spectra 10/2014;
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    ABSTRACT: Implementation of a mechanical Negative Stiffness Device (NSD) within a reduced-scale highway bridge model and its performance under seismic loading conditions is evaluated via shaking table tests. Four different isolation system configurations are considered: isolated bridge (IB), IB with viscous dampers, IB with NSDs and IB with viscous dampers and NSDs. In addition, two bridge pier configurations were considered, one with flexible piers (mimicking a middle span of a multi-span bridge) and one with braced piers (mimicking a single span bridge supported on abutments). The main feature of the NSD is a large pre-compressed spring, which can push the structure away from its initial undeformed position and thus induce negative stiffness behavior. The experimental results clearly demonstrate the effectiveness of the NSDs in limiting the seismic response of the bridge and provide validation of numerical simulation results wherein numerical models of the bridge model components were calibrated via system identification testing.
    Earthquake Spectra 07/2014;
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    ABSTRACT: Using data from the California Strong Motion Instrumentation Program, we studied the relationship between building response and parameters describing the noxiousness of ground motion. According to vulnerability methods that use structural drift as damage criteria, we estimated the building response on the basis of the normalized relative roof displacement (NRRD), considered as damage criteria. The relationships between the NRRD and the intensity measures of the ground motion are developed using simulated annealing method. Grouping buildings by typology (defined according to their main construction material and height) reduces the variability of the building response. Furthermore, by combining IMs, the NRRD can be predicted more accurately by a Building Damage Prediction Equation. A functional form is thus proposed to estimate the NRRD for several building typologies, calibrated on the building responses recorded in California. This functional form can be used to obtain a fast and overall damage forecast after an earthquake.
    Earthquake Spectra 06/2014;
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    ABSTRACT: On 20th and 29th May 2012 two earthquakes of magnitude 5.9 and 5.8 (MW) occurred in the Emilia region (Northern Italy), one of the most developed industrial centers of the country. A complete photographic report collected in the epicentral zone shows the seismic vulnerability of precast structures, the damage to which is mainly caused by connection systems. Indeed, the main recorded damage is either the loss of support of structural horizontal elements, due to the failure of friction beam-to-column and roof-to-beam connections, or the collapse of the cladding panels, due to the failure of the panel-to-structure connections. The damage can be explained by the intensity of the recorded seismic event and by the exclusion of the epicentral region from the seismic areas recognized by the Italian building code up to 2003. Simple considerations related to the recorded acceleration spectra allow motivating the extensive damage due to the loss of support.
    Earthquake Spectra 05/2014; 30(2):891-912.
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    ABSTRACT: The study of earthquakes from historical sources, or historical seismology, was considered an early priority for the Global Earthquake Model (GEM) project, which commissioned a study of historical seismicity on a global scale. This was the Global Earthquake History (GEH) project, led jointly by the Istituto Nazionale di Geofisica e Vulcanologia (INGV; Milan, Italy) and the British Geological Survey (BGS; UK). GEH was structured around three complementary deliverables: archive, catalog, and the Web infrastructure designed to store both the archive and catalog. The Global Historical Earthquake Archive (GHEA) provides a complete account of the global situation in historical seismology for large earthquakes. From GHEA, the Global Historical Earthquake Catalogue (GHEC v1.0) was derived—a world catalog of earthquakes for the period 1000–1903, with magnitudes of Mw7 and over. Though much remains to be done, the data here presented show that the compilation of both archive and cat- alog contribute to an improved understanding of the Global Earthquake History.
    Earthquake Spectra 05/2014; 30(2):607-624.
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    ABSTRACT: This paper examines the seismic response of a cooling tower supported on four isolation/restraint (I/R) mounts. The tower was mounted on the roof of a five-story reinforced concrete building built at full-scale and tested on the large outdoor unidirectional shake table at the University of California, San Diego. The building was tested in two phases: (i) base-isolated, and (ii) fixed-base. In each phase, the building was subjected to six earthquake input ground motions reproduced by the shake table. In this paper, the measured response of the cooling tower and its supporting system are analyzed and compared to current code provisions.
    Earthquake Spectra 04/2014;