Review of the book by Antonello Ciccozzi
L’Aquila earthquake
Seismic Demand Analysis of Inelastic SDOF Systems Designed According to the NTC 2008 for L’Aquila Earthquake
he study investigates on the inelastic response of equivalent Simple Degree Of Freedom systems (SDOF) to some L’Aquila earthquake accelerograms recorded in the epicentral area. According to recent statistical analysis, L’Aquila earthquake is considered as a seismic event having a return period of about 475 years. The aim of the paper is to give a first interpretation to the high damage levels (IX-X MCS) due to the earthquake, in spite of its moderate magnitudo (ML = 5.8) and the correct historical seismic classification of the stroked area. The study thus analyzes the inelastic seismic demand of a SDOF, designed according to the NTC08, to four near-fault accelerograms recorded during the L’Aquila earthquake main shock, by varying SDOF capacity in terms of strength, ductility and viscous damping, in order to assess the performance targets imposed by the same NTC08. Two well- known damage indices have been used to estimate seismic effects on built environment: Park & Ang and low-cycle fatigue indices. The results highlight the high seismic inelastic demand, well beyond the limit specified in NTC08, both for the design of new buildings and for seismic upgrading of existing ones. This clearly shows the need for a revision of the actual seismic hazard map taking into account the near-fault and site amplification effects, which are not considered within the seismic hazard methods adopted by the NTC08.
For this paper is available an extended abstract after the text in Italian
Early comments about earthquake effects on masonry buildings in the neighbourhood of L’Aquila
The present work illustrates some early considerations on the effects of the 6 April 2009 earthquake and of the following seismic sequence in some towns in the neighbourhood of L’Aquila, in central Italy. Such considerations were recorded, during technical surveys to assess the structural usability of buildings using the first-level AeDES form, by technicians of the Ground, Seismic and Geological Survey Group of Emilia-Romagna Region with the volunteer assistance of experts from Universities of Bologna, Ferrara and Parma. In the paper the attention is focused on masonry buildings since they experienced, particularly the older ones, the major damage. The seismic behaviour and the most frequent damages of recurrent typologies of masonry structures in the inspected area are described. Most of buildings are characterized by masonry structures with raw stones and sub-horizontal disposition, or by concrete bricks and large mortar joints with concrete-brick floors and roofs. Inspections in masonry structures allowed the detection of four frequent failure modes: partial decohesion of masonry walls, overall out-of-plane rotation of walls, out-of-plane flexure, in-plane flexure and shear. Moreover the behaviour of buildings strengthened with different techniques, including reinforced plaster or steel ties, is examined. Finally some considerations are made on the failure of churches.
For this paper is available an extended abstract after the text in Italian