Rita Greco

Strong motion duration effects on base isolated systems

In this paper the non-stationary response covariance of a base isolated building subjected to a seismic excitation modelled through a zero mean Gaussian non-stationary stochastic process, uniformly modulated in the time with a boxcar-shape temporal function, is determined. The results are utilised to give an estimation of the strong motion duration effects on the temporal peak of the root mean square value of the response of the system and on system failure probability for first threshold crossing.

Fuzzy reliability analysis of RC structures by using an improved time-dependent model of chloride ingress

Steel bars pitting corrosion is a process that strongly jeopardises the reliability of the reinforced concrete structures exposed to chlorides. The proper treatment of uncertainties that affects geometrical, mechanical and chemical involved parameters is for some aspects still an open question because the probabilstic approach, ordinarily adopted, presents some limitations not only when few data are available to characterise involved variables but especially when some parameters are ambiguously defined, not only in terms of distribution type. In these circumstances a possibilistic approach could respresent a reasonable alternative to perform this specific reliability analysis. In the present study, the problem parameters are modelled by using a complete fuzzy criterion and a time-dependent fuzzy safety factor is defined in order to evaluate how the residual flexural resistance is greater or less than the bending moment. Moreover, the study provides a more proper mathematical analysis of the chloride penetration into concrete.

OPTIMAL DESIGN OF TUNED MASS DAMPERS BY PERFORMANCE–COST ANALYSIS

This work deals with the multi-objective optimization of single Tuned Mass Dampers, focusing on buildings subject to low-moderate earthquakes. The novelty consists in considering both economic and performance criteria. The economic objective is represented by the cost of the device, directly related to its mechanical parameters, while the ratio between the absolute acceleration of the protected structure and the unprotected one is assumed as performance parameter. This latter parameter allows in fact to evaluate the damage level and the behavior of both components and equipment. A multi-objective optimization problem is then so formulated and the Non-dominated Sorting Genetic Algorithm, in its second version, is applied to obtain the Pareto optimum solutions. Finally, by a sensitivity analysis, the optimum solutions are commented with respect to some input data. 2161 Available online at www.eccomasproceedia.org Eccomas Proceedia COMPDYN (2017) 2161-2170

Stochastic Analysis of Sensitivity and Efficiency of Base Isolation System in Seismic Structural Protection

In this research the seismic response of structures isolated at the base by means of High Damping Laminated Rubber Bearings (HDRB) is evaluated. The analysis is performed by using a stochastic approach and a Gaussian zero mean non stationary stochastic process is used in order to model the seismic acceleration acting at the base of the structure. In order to take into account of the non-linear constitutive behavior both of the base isolation device and of the structure, the hysteretic differential Bouc-Wen model (BWM) is adopted. Moreover, the stochastic linearization method in the time domain is adopted to estimate the statistical moments of the non-linear system response in the state space. After estimating the system response variance a sensitivity analysis is carried out. The final aim of the research is to asses the real capacity of base isolation devices in order to protect the structures from seismic actions, by avoiding a non-linear response with associated large plastic displacements, and, therefore, by limiting related damage phenomena in structural and non structural members. In order to achieve this objective the stochastic response of a non-linear n-dof shear-type base isolated building is analyzed. The protection level offered to the structure by the base isolators is then assessed by evaluating the reduction both of the displacement response and the hysteretic dissipated energy.Copyright