The construction of tunnels has become increasingly common in city infrastructure; tunnels are used to connect different places in a region (for transportation and/or drainage). In this study, the structural response of a typical segmental tunnel built in soft soil was studied using a simplified model which considers the coupling between segmental rings. From an engineering point of view, there is a need to use simple and reliable finite element models. Therefore, a 1D model based on the Finite Element Method (FEM) composed of beam elements to model the segments and elastic-linear springs and non-linear springs to model the mechanical behavior of the joints was performed. To validate the modeling strategy, the numerical results were compared to (lab-based) experimental results, under an Ultimate Limit State, obtained from the literature, and a comparison between numerical results considering a 3D numerical complex model which included the nonlinearity of concrete, reinforcing steel and the joints was performed. With this simplified model, we obtained a prediction of approximately 95% of the ultimate loading capacity compared to the results developed in the experimental and 3D models. This proposed model will help engineers in practice to create “rational” structural designs of segmental tunnel linings when a “low” interaction between rings is expected.

In this work, electrochemical monitoring of stress corrosion cracking (SCC) behavior of a X70 steel in acidic synthetic soil solution during the slow strain rate test (SSRT) was performed by electrochemical noise (EN) using the conventional arrangement of symmetrical electrodes and electrochemical emission spectroscopy (EES) using the asymmetrical arrangement replacing the second working electrode for a platinum micro-cathode. The statistical method, fast Fourier transform, and discrete wavelet transform were used for analyzing the potential and current signals recorded by both arrangements. The results showed that EN arrangement was more effective to detect the crack initiation at a point close to yield strength despite stress-induced asymmetry in one of the electrodes. For the EES arrangement, the micro-cathode had a strong influence on the electrochemical noise of the current and potential under stress conditions. From the transient features, statistical parameters, and wavelet analysis, a discontinuous transgranular SCC mechanism was found. The resistance values obtained by EN measurements had better correlation with the electrochemical impedance spectroscopy results (EIS) than EES measurements.

Frame buildings are prone to cracking because of their deformation by normal and extreme events such as temperature and earthquakes. Even though the crack widths are limited in the structural design, a cracked cover reduces the corrosion protection of reinforcing steel. Therefore, the load capacity of structures can be compromised prematurely. This paper aims to evaluate the flexo-compressive strength of deteriorated reinforced concrete (RC) elements in the corrosion process. To that end, a methodology to calculate the residual strength capacity was proposed, considering the influences of crack widths and cover width on the corrosion level—structure age relation of RC elements. The strength deteriorations caused by the concrete cracking and the steel corrosion were incorporated according to structure age. The residual strength was studied using parametric analyses, whose variables were the crack width, the cover width, the rebar diameter, and the structure age. The results showed that the cracked frame elements reduced their serviceability life by up to 62%, although their crack widths were within range recommended by the design codes (lesser than 0.30 mm). In 25 years, the corrosion effects reduce the element strength by up to 44%. This is due to the corrosion protection provided by the cracked cover becomes insignificant, reducing the initiation time. Thus, considering the corrosion deterioration can prevent strength overestimations up to 1.46 times. Additionally, according to their current state, the proposed methodology provides a practical estimation of flexo-compressive strength in corroded RC elements.

Increased temperature due to global climate change is increasing the magnitude and frequency of extreme winds making billboard structures more vulnerable. This paper proposes a methodology to determine the structural safety of flexible outdoor single-post billboards. A CFD model of a flexible single-post billboard was performed as an example. Resultant wind forces were obtained for the previous model using different wind speeds. A mechanical numerical model of the billboard was realized, and this was subjected to the resultant wind forces. Internal forces for the most vulnerable places of the billboard were obtained for all different adopted wind speeds. Next, a reliability analysis of the billboard was performed considering several values for the bias factor and coefficient of variation for the internal forces caused by wind. Safety levels determined from the reliability analysis indicate that a billboard designed with a nominal wind speed of 180 km/h cannot achieve the target probability index of 3.2 for wind speed higher or equal to 200 km/h for any of the adopted probabilistic parameters. Significant differences in the found safety levels for the evaluated probability parameters indicate that billboard structures could undergo safety values below the target one with changes in the case where wind characteristics endanger this type of structure.

The aim of the research reported in this paper was to evaluate the recommendations commonly used for limiting the deformations of segmental reinforced concrete tunnels built in soft soil. These traditional deformation limits are empirical and do not consider the slenderness ratio or soil-pressure distribution around tunnels. Furthermore, while they are generally assumed to relate to the serviceability limit state, this is not clear. Parametric analyses were therefore performed by means of finite-element models in which the non-linear behaviour of joints and materials was taken in account. The serviceability deformation was defined to prevent typical problems that could jeopardise the serviceability states of segmental linings. These serviceability deformations were then compared with traditional deformation limits. The results showed that the serviceability deformation depends on the slenderness ratio and the soil-pressure distribution. It was concluded that empirical recommendations are only suitable for certain slenderness ratios and soil-pressure distributions.