1,721,087 research outputs found
R.C. Technology in Italy at the Beginning of 20th Century: a Historical Journey Through the Work of Porcheddu Society
No full textSeismic vulnerability of r.c. circular bridge columns
No full textThe seismic response of highway viaducts with bearing-supported superstructures and characterized by structural
regularity, essentially depends on the behaviour of its piers. Therefore, the vulnerability analysis of the most
exposed column often coincides with that of the whole structure. This paper is focused on a simplified procedure
that furnishes the expected damage vs ground acceleration for homogeneous families of piers, characterized by
same design and site parameters. The procedure preliminarily analyzes different forms of column failures
(flexural failure for inadequate confinement of the plastic hinge zone; flexural strength degradation in sections
with lap-spliced reinforcement; shear failure; buckling of reinforcements). Subsequently, on the basis of a
comparative analysis, the most probable condition of collapse is determined. The algorithm utilizes an
approximated closed-form approach, properly obtained, in terms of longitudinal reinforcement, transverse
confining steel, and base axial compression
Fuzzy Time-Dependent Reliability Analysis of RC Beams Subject to Pitting Corrosion
No full textSteel bars pitting corrosion is an electrochemical process that could seriously jeopardize the reliability of reinforced concrete structures. Even if detailed models exist to predict the lifetime of the concrete element when it is subject to this environmental attack, their applications present serious limitations that undergo, to the noteworthy sources of, uncertainty of many problem parameters. This restriction could produce erroneous solutions, especially when analysis deals with existing buildings or little information about problem parameters are accessible. In detail this takes place when real environmental conditions, mechanical properties as well as load conditions, could only be estimated and not known with enough accuracy. To overcome this problem, some methodologies have been developed, assuming that uncertainty variables can be suitably modeled in a probabilistic way, and therefore traditional theories for reliability assessment can be used. Nonetheless, in the analysis of this problem, there are other parameters that cannot be treated opportunely in a probabilistic way. The main purpose of this paper is to develop an efficient alternative approach for time-dependent reliability analysis regarding reinforced concrete beams subject to pitting corrosion, when probabilistic and nonprobabilistic parameters occur at the same time. With this new approach, it is possible to obtain a versatile tool to support the decision maker in planning maintenance interventions
Stochastic approach for analytical fragility curves
No full textOne of the main problems is the assessment of “residual reliability” or “vulnerability” of a single existing structure, or of a given class of similar structures, against seismic actions. The fragility curves describe the probability of a structure to suffer a given damage level when it is subject to a given seismic excitation level. This research work is focused on an analytical method for constructing fragility curves of existing structures based on a stochastic approach. Analysed structure is modelled by a simple one degree of freedom system subject to a nonstationary Kanai-Tajimi process. The numerical values of the parameters of its constitutive law, here suitably described by means of a hysteretic model, are selected using an identification procedure with the non linear pushover analysis performed on the real assessed structure. To develop fragility curves, a displacement based damage index is adopted. Fragility curves are obtained in terms of probability of exceeding a given damage level by using an approximate crossings theory of stochastic processes
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