Ritermayer Monteiro Teixeira

This article presents a probabilistic methodology for assessing corrosion initiation in reinforced concrete structures exposed to chloride ingress. The approach addresses key limitations of conventional analytical models by accounting for non-diffusive barriers and incorporating a rigorous statistical treatment of censored data to mitigate biases introduced by limited simulation durations. A combination of analytical solutions for diffusion from opposite sides with time-dependent boundary conditions is also proposed and validated. The probabilistic study includes the depassivation assessment of a hollow pier section. The blocking effect caused by rebars is statistically characterised through correction factors derived from finite element simulations. These factors are used to adjust analytical solutions, which are computationally inexpensive. Results show that neglecting the rebar blocking effect can overestimate the mean corrosion initiation time by up to 42%, while the use of censored data reduces bias in lifetime estimates. The observed frequency of censored events reached up to 20% when simulations were truncated at 100 years. The corrected analytical models closely match the finite element results, statistically validating their application. The case study indicates premature corrosion initiation (less than 10 years to achieve target reliability), underscoring the need to better reconcile the desired levels of reliability with realistic input parameters for depassivation.

Although Fiber Reinforced Polymer (FRP) prestressing is widely recognized for enhancing the serviceability conditions of strengthened structural elements, there are no available fatigue prediction models encompassing the specificities and advantages of FRP prestressing. In this context, this paper addresses the effect of FRP prestressing on the fatigue performance of strengthened reinforced concrete (RC) beams through the assessment of experimental data, constant life diagrams, and the adjustment of specific stress versus number of cycle (S‐N) curves for RC strengthened with prestressed FRP. First, data obtained through the development of an experimental program give an insight into the long‐term behavior of full‐scale beams subjected to in‐service and severe fatigue loading conditions. Fatigue life prediction models based on the adjustment of S‐N curves are developed using an extensive database of failure data and runouts of fatigue tests. Finally, data of fatigue tests plotted in a constant life diagram evidence the combined effects of stress range, mean stress, R ratio, and reinforcing steel properties on the fatigue life of RC beams strengthened with prestressed FRP. Results highlight the positive effects of FRP prestressing by the improvement of serviceability condition under static loading and the increasing of endurance limit under cyclic loading.

The use of externally bonded fibre-reinforced polymer (FRP) increases the fatigue life of reinforced-concrete beams due to a reduction in the steel stress level when compared with unstrengthened beams. For steel stresses up to 80% of the yield stress, fatigue failure is normally marked by the gradual deterioration of the steel reinforcement, which leads to a stress transfer to the FRP, until failure. Higher steel stresses are associated with FRP debonding, while steel stresses below the fatigue limit will never lead to fatigue failure. In this work, the maximum likelihood estimation method was used to determine stress–cycle curves and confidence intervals. Experimental data with runouts of fatigue tests found in the literature and generated through an experimental programme were used to adjust the fatigue model. The aim was to characterise the large scatter between the results of fatigue tests from different sources. The proposed fatigue model was found to represent accurately the slope of the fatigue curve for FRP-strengthened beams.

Modeling the traffic loads on bridges has been the subject of numerous studies. Defining a live load model to be used for bridge design is not an easy task. It demands among many other things a reliable dataset, a well-defined procedure for filtering data and also the determination of statistics for single and multiple presence occurrences. This study examines and characterizes the live load statistics for Brazilian concrete bridges. Single and multiple truck presence are evaluated for different bridge spans and truck daily volume. The sample is comprised of the thirteen months of data from a High Speed Weigh-In-Motion station (HS-WIM) in a resolution of one hundredth of a second currently operating on the Fernão Dias highway, also known as BR-381. The system provides eleven thousand records on a daily basis. After the filtering process three thousand trucks remain. The station takes measures in an same-direction two-lane highway, which allows the evaluation and characterization of both single and multiple presence statistics. Three case of multiple presence are considered: following, side-by-side and staggered cases. The consideration of truck multiple presence on concrete bridges is mandatory to understand and characterize live load models. The results show that with the exception of the side-by-side case, the frequency of multiple truck presence is significantly affected by span length. It also shows that the daily truck volume considerably affects the multiple presence statistics for all load patterns. The results show that the general tendency of the occurrence of all multiple presence events is to increase as the truck volume increases.