In the presented practice-oriented probabilistic approach for the seismic performance assessment of building structures, the SAC-FEMA method, which is a part of the broader PEER probabilistic framework and permits probability assessment in closed form, is combined with the pushover-based N2 method. The most demanding part of the PEER probabilistic framework, i.e. Incremental Dynamic Analysis (IDA), is replaced by the much simpler N2 method which requires considerably less input data and much less computational time, but which can, nevertheless, often provide acceptable estimates for the mean values of the structural response. Using some additional simplifying assumptions that are consistent with seismic code procedures, an explicit equation for a quick estimation of the annual probability of “failure” (i.e. the probability of exceeding the near collapse limit state) of a structure can be derived, which is appropriate for practical applications, provided that predetermined default values for the dispersion measures are available. In the paper, this simplified approach is summarized and applied to the estimation of the “failure” probability of reinforced concrete frame buildings representing both old structures, not designed for earthquake resistance, and new structures designed according to Eurocode 8. The results of the analyses indicate a high probability of the “failure” of buildings which have not been designed for seismic loads. For a building designed according to a modern code, the conservatively determined probability of “failure” is about 30 times less but still significant (about 1% over the lifetime of the structure).
COBISS.SI-ID: 5478241
The proposed method involves a non-linear static analysis of a set of structural models, which is defined by utilising Latin hypercube sampling, and non-linear dynamic analyses of equivalent single degree-of-freedom models. The set of structural models captures the epistemic uncertainties, whereas the aleatory uncertainty due to the random nature of the ground motion is, as usual, simulated by a set of ground motion records. Although the method is very simple to implement, it goes beyond the widely used assumption of independent effects due to aleatory and epistemic uncertainty.
COBISS.SI-ID: 5380961
In order to provide adequate seismic behavior of masonry walls, local brittle failure of masonry units in the most stressed zones of structural walls shouldbe prevented. Although robust behavior is required by the code, no specifications are given regarding the criteria to fulfill this requirement. To propose such criteria, a series of 28 masonry walls, built with six different types of hollow clay masonry units, currently available on the market, have been tested by subjecting them to cyclic lateral load at two levels of constant precompression. Besides, the strength characteristics of the units, like compressive strength orthogonal and parallel to the bed jointsand tensile and shear strength of the units have been determined by standardized and specifically designed testing procedures. By correlating the parameters of seismic resistance of the walls and strength characteristics of the units, no specific indicator for robustness could have been determined on the basis of the mechanical characteristics of the tested units. It has been found that in all cases the level of precompression, i.e. the ratio between the compressive stresses in the walls and the compressive strength of masonry,represents the governing parameter.
COBISS.SI-ID: 1829223