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Even if the effectiveness of friction pendulum bearings has been extensively proven by means of numerous experimental programs carried out worldwide, many aspects concerning their behavior under seismic action still need to be clarified. One of these is related to the temperature rises induced by the heat generated by friction during the dynamic sliding of the surfaces in contact, which may significantly affect the superficial frictional properties of the sliding surfaces involved, thus reducing the overall performance of the isolating system, up to re-coupling the structure with the ground shaking, in a limit scenario. With the aim to contribute to a better understanding of this aspect, and to develop a simplified tool capable to reproduce the hysteretic force—displacement loops together with the corresponding temperature variations, a thermo-mechanical model for the multiple friction pendulum devices is proposed. The model is based on the combination of simple thermomechanical rheological elements and does not require the evaluation of any convolution integral arising from the solution of the heat conduction problem as it happens with many existing models. The model is numerically implemented under displacement-control and its effectiveness is validated through the numerical simulation of some recent experimental results that shows a good agreement with the observed behavior.

•A rheological friction model including temperature is proposed.•The displacement-based calculation procedure is described in detail.•Experimental tests are simulated in order to assess the validity of the proposed procedure.

In performance-based earthquake engineering, probabilistic seismic demand models are usually developed by using methods which need a large number of nonlinear dynamic analyses to be run. In order to reduce the numerical effort, simplified methodologies of analysis have been proposed. Objective of the present study is to use the uncoupled modal response history analysis for the estimation of acceleration floor spectra, engineering demand parameters commonly used for measuring seismic demand in acceleration-sensitive non-structural elements. The procedure is evaluated for a 6-story reinforced concrete frame case study, designed to be representative of an existing structure lacking in specific capacity design rules.

Abstract: In the framework of performance-based assessment of existing RC buildings, an important step is the definition of an intensity measure (IM) of the seismic action that be accurate and efficient in correlating with the engineering demand parameters (EDP) of interest and in reducing the variability in their prediction. Objective of this work is to assess five different IMs, when they are applied to an in-plan irregular three-dimensional building subjected to bi-directional earthquake motion. The objective is pursued through multiple regression of the results obtained from nonlinear dynamic analyses. The study shows that certain IMs are more suitable to evaluate EDPs when dealing with 3D structures subjected to 2D earthquakes.

The normal-faulting earthquake of 6 April 2009 in the Abruzzo Region of central Italy caused heavy losses of life and substantial damage to centuries-old buildings of significant cultural importance and to modern reinforced-concrete-framed buildings with hollow masonry infill walls. Although structural deficiencies were significant and widespread, the study of the characteristics of strong motion data from the heavily affected area indicated that the short duration of strong shaking may have spared many more damaged buildings from collapsing. It is recognized that, with this caveat of short-duration shaking, the infill walls may have played a very important role in preventing further deterioration or collapse of many buildings. It is concluded that better new or retrofit construction practices that include reinforced-concrete shear walls may prove helpful in reducing risks in such seismic areas of Italy, other Mediterranean countries, and even in United States, where there are large inventories of deficient structures.

About 10% of the almost 20,000 buildings damaged by the 2002 Molise, Italy, seismic sequence were reinforced concrete (RC). The most frequent type of damage affected the infill masonry walls, but in some cases cracks in concrete columns were observed. Heavy damage to both infills and structural elements was restricted to a few cases in the meizoseismal area. Almost all the affected municipalities were only classified as seismic in May 2003, following this earthquake. Consequently, construction generally used vertical-load-bearing moment-resisting frames with no explicit design for seismic lateral forces. In particular, the reinforced concrete buildings typically consist of cast-in-place unidirectional RC slabs lightened with hollow clay tiles, supported by RC beams and columns. Usually no shear walls are present, except in some cases for the elevator shaft. This paper covers: a) an overview and statistical analysis of damage to RC buildings, and b) a detailed analysis of two damaged buildings.

The 2002 Molise, Italy, earthquake struck a relatively limited geographical area where the communities are mainly agrarian. While most buildings in the region are masonry, there are significant differences in the type of masonry construction, as material characteristics and construction practices had changed over the centuries. This paper focuses on the masonry buildings that predominate in domestic construction. The most significant features that contributed to the damage pattern appear to be (1) construction criteria, techniques, and details that were inadequate for seismically active areas, particularly in buildings constructed or substantially modified over the past 100 years, and (2) site effects resulting from differences in amplification and frequency of the vibrations that locally increased the destructiveness of the earthquake. The observed damage did not correlate to the vulnerability that would be assigned to the structures under the European Macroseismic Scale.

In 1998, a new system of seismic classification promoted by the Department of Civil Protection identified the area in Italy hit by the 2002 earthquake in Molise and Puglia as a Zone 2 (moderately seismic). However, this classification was not adopted until March 2003, when an ordinance passed that partially closed the gap between scientific knowledge and official recognition of seismic hazard and that established a method for constantly updating the classification in the future. This paper reviews some of the methods available to assess the seismic hazard, particularly referring to the rich seismic history of Italy and using the “Associated Seismic Area” concept. This study confirms that the area affected by this earthquake should be considered as Zone 2. An appendix presents data on the seismic risk of existing buildings in the area and concludes that it is high for masonry buildings and that a strengthening program is needed.

The object of this paper is to introduce a procedure for the determination of elastic design earthquake input energy spectra taking into account the influence of magnitude, soil type and distance from the surface projection of the fault. Firstly, an accurate selection of a large set of representative records has been realized. Secondly, the construction of the design input energy spectra has required determining the spectral shapes and a normalization factor which measures seismic hazard in terms of energy. This factor, denoted as the seismic hazard energy factor, has been defined as the area under the earthquake input energy spectrum in the period interval between 0·05 and 4·0 s. Finally, due to the importance of the source-to-site distance in the evaluation of the input energy, an investigation into the attenuation of the seismic hazard energy factor has been carried out. © 1998 John Wiley & Sons, Ltd.