During the week after the main shocks two survey groups visited the area and prepared for ‘Ingegneria Si- smica’ the following preliminary reports on damage suffered by some masonry and r.c. buildings. The groups included researchers of various Universities and engineers belonging to Public Administations. Seismological data of the events may be found at the site http://itaca.mi.ingv.it/itacanet/.
For this paper is available an extended abstract after the text in Italian
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
The paper presents an overview of a new originally developed quasi-optimal control algorithms for reproduction of earthquakes by shaking tables. As known, shaking tables are widely used for testing of structures, models or structural details subjected to earthquakes or other types of dynamic loadings. In order to obtain dynamic response of a tested model close to that of a real structure, the shaking table should reproduce real dynamic excitations with high accuracy. Moreover, the shaking table control algorithm should consider real restrains in the platform displacements. Changing the ground acceleration record by time scaling, like it is common in existing algorithms, yields undesired effect on the tested models dynamic behaviour. The originally developed approach, described in this paper, is based on optimal signals perturbation and filtering technique. It includes quasi-optimal spline approximation and further optimal smoothening of the dynamic loading signal, decreasing negative effects. Selecting the smoothening parameters is an adaptive procedure, performed by comparing the spectrum characteristics of the original and reproduced signals. The effectiveness of the proposed method is demonstrated by obtaining responses of multi-story structural models subjected to various seismic excitations. It is shown that the proposed algorithm is a very effective method for reproduction of real earthquakes by using shaking tables with limited stroke.
The technique of the seismic base isolation (Base Isolation System − BIS) represents an innovative structural control system and, in particular, an important passive control system for seismic protection of structures. This technique has reached a high level of reliability and, as a matter of fact, isolated structures do have an elastic behaviour during the earthquakes, even of high intensity. This reliability is witnessed by the new seismic codes that allows for the use of BIS and provides specific design criteria. In this work, the Base Isolation System for a multi- storey reinforced concrete building, highly irregular in plan, has been considered. The Eurocodes (EC0; EC2; EC8) have been adopted and compared with the new Italian seismic code (NTC 2008). The base isolated structure has been compared to the fixed base structure and the significant benefits that the technique provides on the seismic response of the structure, with significant spin on the costs of the structure, have been highlighted.
For this paper is available an extended abstract after the text in Italian
In this paper the ultimate resistance for shear not directed as principal axis of inertia of RC columns sections is evaluated by means of a numerical method. The sections may be of any shape (circular too) and are also subjected to axial force and biaxial bending. Although the importance of this topic for capacity design rule in seismic design, no indication is present in Italian code nor in Eurocodes.
For this paper is available an extended abstract after the text in Italian
For this paper is available an extended abstract after the text in Italian
Discussion on the new italian seismic code
For this paper is available an extended abstract after the text in Italian