STRUCTURAL RELIABILITY ANALYSIS OF A REINFORCED CONCRETE BEAM STRENGTHENED WITH CARBON FIBER

Resumo

Concrete beams and strengthening design procedures are commonly specified in normative
codes, using simplified deterministic procedures. This prescriptive methodology has as a consequence
in practice in which structural safety is indeterminate, since the innumerable sources of uncertainty when
designing the project can result in significant deviations from reality. As an alternative, the safety of
these beams can be quantified through the application of structural reliability theory. The present work
analyzes safety of a reinforced concrete beam strengthened with carbon fiber. For this, the Monte Carlo
method is applied to determine the reliability index and probability of failure of the structural element.
The steel reinforcement design of the beam was performed according to NBR 6118 [1], and in sequence
a load increase analysis was conducted to justify the strengthening. The fiber strengthening was designed
according to two methods, the available in ACI 440.2R-17 [11] and in Machado [3]. In the specific ACI
method two set of material parameters were tested, the recommended on ACI 318-14 [2] and the
designated on NBR 6118 [1]. As a result of the analysis with both methods it was observed that in some
cases the reliability indexes were unanimously superior to the coefficients targeted. In the case of the
use of parameters of the Brazilian standard in the ACI 440.2R-17 [11] design methodology, there were
cases in which the same indexes were not satisfactory. Because the central verification in the ACI
440.2R-17 [11] design procedure is the steel tension, a different assumption in its yield limit changes
considerably the results and the probabilistic response.