Search

Second‐generation Eurocode 8 introduces displacement‐based design alongside the traditional force‐based one with reduced equivalent forces; it provides resistance models needed to apply the approach to reinforced concrete, steel and composite frame or wall‐frame structures: chord rotation for members, and shear strength for members and joints; finally, it declares a target reliability level for near collapse. This paper discusses the formulation of partial factors to achieve a target reliability when using the displacement‐based approach. The factors are derived following a traditional, time‐invariant way of performing code‐calibration for other non‐seismic design situations, starting from the probability distributions for the seismic action effect and the resistance. It is shown that the problem can be simplified to one with two Lognormal variables, a uniform reliability can be achieved over the calibration space when both a load‐side and a resistance‐side factor are used, and constant sensitivity coefficients can be used, with values different from the original König and Hosser ones and reflecting the larger weight of the action‐related uncertainty in the seismic case. The problem with this otherwise good result is that a partial factor on the load side must be used and, further, that its value is site dependent. This approach is not in line with current European practice, thus a corrected site‐independent resistance‐side partial factor is proposed, which is compatible with the framework of Eurocode 8. As a further advantage, the proposed format coincides with that proposed in the second‐generation EN1990/EN1992 for the assessment of existing structures under non‐seismic design situations. [ABSTRACT FROM AUTHOR]

This study investigates the seismic response of archetype infilled reinforced concrete buildings representative of the existing Italian residential building stock by focusing on the modelling aspects of the existing infills, including their failure modes and interaction with the frame. The study compares the seismic response of the considered buildings, investigated through nonlinear static and dynamic analysis, with reference to two Performance Levels. The main variables considered are the construction period, the site hazard, the number of stories and the infill configuration. The observed return period capacity of the buildings mainly depends on the site hazard and on the construction period. [ABSTRACT FROM AUTHOR]

This study investigates the seismic response of reinforced concrete buildings designed according to Italian regulations and construction practices for three different post-WWII periods, up to the 1990s. Additional key investigated parameters are the number of stories and the site hazard. The main issues related to non-seismic and early seismic design practices are discussed. The study compares the seismic response of the buildings, investigated through nonlinear static and dynamic analyses, with reference to two performance levels, confirming and quantifying the increase in performance with the design codes evolution. The seismic behavior of infilled frames is investigated in the companion paper. [ABSTRACT FROM AUTHOR]

The effect on seismic demand of the soil-foundation compliance is investigated for a reinforced concrete frame building representative of Italian constructions from the 1970s. Design accounts for regulations, materials, preferred structure and foundation layouts and analysis methods of the period. Inelastic response history analysis for multiple motions at three intensities is carried out. For the compliant-base case, each foundation is replaced with a nonlinear inertial macro-element. Results suggest that the effect of interaction is minor, lower than expected from similar analysis on a new building, due to the larger degree of conservatism associated with foundation design in the considered period and the corresponding lower strength and stiffness of the superstructure. [ABSTRACT FROM AUTHOR]

The paper investigates the problem of Soil‐Foundation‐Structure Interaction (SFSI) for buildings supported on piles through the comparative analysis between the fixed base and the compliant base assumptions. The structure, a nine‐storey residential building (with or without infills), is modelled in non‐linear regime while the piled foundation is idealized by means of independent lumped parameters models, either linear or non‐linear. In this last case, the soil‐foundation system is replaced by an assembly of viscous‐dampers, fictitious masses and non‐linear springs modelled according to the classical Bouc‐Wen formulation, so as to account for the hysteretic behaviour of the foundation. A detailed calibration procedure for both linear and non‐linear foundation models is also presented and discussed. Two different natural soil deposits are considered, a pyroclastic deposit and a deep layer of lacustrine clay. The results undertaken in the context of a probabilistic analysis show that SFSI may lead to a significant reduction of the seismic demand in infilled buildings at low and intermediate earthquake intensity levels. Conversely, at higher intensity earthquakes the seismic demand is not affected by the non‐linear springs. It is shown that a proper modelling of radiation mechanism at foundation level is crucial for a reliable and sustainable prediction of SFSI effects. [ABSTRACT FROM AUTHOR]