The model considered in this paper for analysis of fast and large ground movements is based on the equations of motion, mass and energy balances and on conventional ground parameters. The model capability is checked for the Pandemonium Creek rock avalanche in British Columbia, the Shum Wan Road debris run-out in Hong Kong and a coal mine waste fast spread at Aberfan in Wales. The analytical model can be used for first estimates of basic ground movement parameters such as the travel distance, peak velocity and acceleration. Despite its simplicity, the model still requires the use of some ground parameters and an assessment of the initial mass conditions a priori by the user.
Month: October 2009
A weakness of the static method as implemented by the Italian seismic Code
The static method of seismic analysis proposed by the Italian code of practice can lead to non- conservative design. This may happen when the rigorous value of the fundamental period of the structure is adopted instead of the approximate one given by the code.The present paper shows that in the presence of eccentricity between the stiffness center and the mass center of the building floors, the static method can under-evaluate the maximum seismic effects by more than 25%. Appropriate changes in the code should be introduced in order to bring the static method to the safe side. Some possible improvements are discusses in the present paper.
For this paper is available an extended abstract after the text in Italian
Seismic design methods of concentrically braced steel frames
SUMMARY – The work described here is addressed to the evaluation and the comparison of different seismic design methods of multistory steel frame structures with concentric braces. In particular, a multistory frame is designed through both the simplified method currently proposed by the recent code provisions (OPCM 3431, DM 24/01/2008, Eurocode 8 ) and an alternative simplified one, based on the partial contribution due to the brace under compression. The assessment of the seismic response of the two structures is then performed by means of static analyses, where the non-linearities of the geometry and of the materials are included, in order to compare the related seismic performances. In addition, the seismic response of the frame designed with the new method is assessed through non-linear dynamic analyses and incremental dynamic analyses, to particularly highlight the properties of the alternative adopted method, which permit to achieve less conservative solutions, more economical in terms of amount of material and characterized by more effective collapse mechanisms.
For this paper is available an extended abstract after the text in Italian
The new bridge seismically isolated over the river Fella in Dogna (Italy): design validation as a result of structural dynamic tests
An example of structural validation as a result of dynamic identification of a new bridge over the river Fella in Dogna (Italy) follows. The structure, a prestressed concrete continuous beam, bypasses, with its two spans of 37.5 m each, the wide alluvial riverbed. The bridge, which rises in an high level seismic area, has been isolated by the use of elastomeric isolators able to reduce the heavy stresses of seismic origin. The dynamic tests performed on the bridge and the followed structural identification by means of model updating have led to a «zero reading» of the dynamic characteristics, to be used as reference data for subsequent analysis of degradation, especially following a seismic event. It will be shown a parallel between the stresses identified in the structural model (based on which the bridge was built) and the resulting model from dynamic identification, to extract a possible criterion for structural validation after the construction.
For this paper is available an extended abstract after the text in Italian
Rehabilitation of a small borough damaged by Umbria earthquake (26/09/1997)
The paper describes the works done to repair the so called «Borgo di Pascelupo». The «Borgo di Pascelupo» is an hamlet placed in Scheggia and Pascelupo’s town, located in Umbria (Italy), damaged by the 26th of September 1997 earthquake. Both the administration and techniques aspects are analyzed.
For this paper is available an extended abstract after the text in Italian
Arturo Danusso and the burden of proof
For this paper is available an extended abstract after the text in Italian