The seismic performance assessment of existing masonry buildings involves many uncertainties, whose impact can be reduced to some extent by using non-destructive in-situ tests of such buildings, at least when destructive in-situ tests, which can provide more reliable results, cannot be performed. In this paper the extent of the potential beneficial effects achievable by calibration of a structural model of a building to its experimentally estimated vibration periods has been investigated. This was done by performing measurements of ambient and forced vibrations on an old two-storey masonry building, and by then assessing its seismic performance using a simplified nonlinear method. The results of numerical investigations revealed that the natural vibration periods of such buildings can be reproduced with sufficient accuracy, although it is possible that they will be overestimated or underestimated by analysts by up to around 40 %. This means that the accuracy of the prediction of the intermediate results of the seismic performance assessment of any particular building can be significantly increased by calibration of the structural model. Additionally, the beneficial effects of such calibration were observed even in the case of the final outcome of the nonlinear analysis, which is expressed through the near-collapse limit state capacity in terms of the peak ground acceleration.
COBISS.SI-ID: 6420577
Seismic design of equipment in industrial buildings is mostly conducted using the floor response spectra, which are often based on the assumption that the behaviour of the structure and the equipment is linear elastic. Essential reductions in peak values of floor response spectra can be obtained if inelastic behaviour of the structure is taken into account. This paper presents the most important results of an extensive parametric study of floor response spectra, taking into account the inelastic behaviour of the structure and the linear elastic behaviour of the equipment. The structure and the equipment were modelled as single-degree-of-freedom (SDOF) systems. Response-history analyses were performed for a set of recorded ground acceleration time-histories and for different properties of the structure. The influences of input ground motion, ductility, hysteretic behaviour and natural period of the structure, as well as damping of the equipment have been studied. Based on the results obtained and the conclusions made, a simple practice-oriented method for direct generation of floor response spectra from the design spectrum is proposed. The method is intended for a quick estimation of approximate floor response spectra.
COBISS.SI-ID: 6372705
Simplified procedures have been used for the estimation of seismic response parameters by considering the epistemic uncertainties for an older reinforced concrete frame, and for two contemporary reinforced concrete structures. The simplifications in the procedure are associated with a simplified nonlinear method and models for the assessment of the seismic performance of the structure, whereas the effects of the epistemic uncertainty are treated by using the first-order-second-moment (FOSM) method, and the latin hypercube sampling (LHS) technique. The results of sensitivity analysis reveal that it is those parameters which affect the collapse mechanism and have a high coefficient of variation that have the greatest impact on the seismic response parameters for the near collapse limit state. The results of uncertainty analysis by using the LHS technique showed that epistemic uncertainties have an effect on the dispersion, and also on the median estimates of the response parameters. For all three example structures a reduction in the estimate for the median peak ground acceleration at the near-collapse limit state was observed. Thus, explicit consideration of epistemic uncertainties in the process of the assessment of structural performance can lead to more accurate results, and consequently also to more reliable assessment of seismic risk.
COBISS.SI-ID: 6228321