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Prestressed concrete piles with closed-ended circular hollow sections (spun piles) are sometimes used as foundations for pile-supported wharves. Due to a reduction in the rebar area, concrete compressive strength, yield strength of PC-bar, and bond strength between PC-bar and concrete, corrosion attacks typically lower the performance of spun piles...
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Context 1
... analysis model was constructed as one quarter of the spun pile section with a height of 250 mm because it had a horizontally axisymmetric shape ( Figure 2). Solid elements were used to model the concrete, PC-bars, and transverse rebar elements ( Figure 3). A hexahedral formulation was employed for the solid-element mesh [34]. ...
Context 2
... et al. proposed the equation by referring to the data for the corrosion degree of 10% or less; therefore, their equation cannot predict the drastic decrease in the compressive strength of the cover concrete in the extensive corrosion degree range. Figure 13 illustrates the local bond-slip relationship for the PC-bars. The black line is the bond-slip without corrosion (0 years), while the red line represents the bond-slip at 75 years. ...
Context 3
... 75 years, the bond (12) Proposed (Cover Concrete) Proposed (Core Concrete) stress decreased to 31.3% of the initial value due to cracks around the corroded PC-bar and concrete. Figure 13 also depicts the bond-slip relationship by using FIB Model Code 2010 [38] and Cairns [39]. The bond strength by using Cairns was similar to that of this study; however, Cairns did not examine the bond strength reduction with the progress of the corroding of the rebar. ...
Citations
... Lately, the technology of vibro-centrifugation, specifically of concrete, has emerged as one of the most promising areas in modern concrete science and technology, allowing for reinforced concrete elements with a variatropic structure. Quite a lot of relevant and interesting scientific works are devoted to this issue from the points of view of materials [3][4][5], design solutions [6,7] and forecasting methods [8][9][10]. However, this area is poorly studied and there is a serious deficiency in both scientific and practical terms, which is expressed in the absence of systematic knowledge about the life cycle management processes of vibro-centrifuged variatropic concrete. ...
... (1) Application of existing experience in theoretical analysis and practical implementation of machine learning methods in the life cycle management of vibrocentrifuged variatropic concrete; (2) Justification of the need to expand the stack of technologies to determine the physical and mechanical properties of vibro-centrifuged variatropic concrete by creating regression models based on machine learning methods; (3) Testing of samples made of vibro-centrifuged variatropic concrete under laboratory conditions, with the subsequent formation of a dataset for the training, optimization and testing of regression models; (4) Analysis of the data obtained, identifying the main statistical characteristics and determining dependencies; (5) Creating an expanded dataset by adding new features at the feature engineering stage; (6) Description and implementation of the ridge regression method on original dataset and feature-engineered dataset; (7) Description and implementation of the decision tree and XGBoost method on original dataset and feature-engineered dataset; (8) Description and implementation of the XGBoost method on original dataset and feature-engineered dataset; (9) Comparative analysis of the results of all models based on the values of the main metrics to assess the quality of the forecast when solving a regression problem; (10) Determination of prospects and features of implementation of developed forecasting methods into practice; (11) Determining the possibility of "learning transfer" by adapting the results obtained to other types of concrete. ...
... The hyperparameters of each model were optimized using the Optuna optimization system. (4) The XGBoost model showed the best quality metrics: MAE = 1.134627, MSE = 4.801390, RMSE = 2.191208, MAPE = 2.72% and R 2 = 0.93. ...
In recent years, one of the most promising areas in modern concrete science and the technology of reinforced concrete structures is the technology of vibro-centrifugation of concrete, which makes it possible to obtain reinforced concrete elements with a variatropic structure. However, this area is poorly studied and there is a serious deficiency in both scientific and practical terms, expressed in the absence of a systematic knowledge of the life cycle management processes of vibro-centrifuged variatropic concrete. Artificial intelligence methods are seen as one of the most promising methods for improving the process of managing the life cycle of such concrete in reinforced concrete structures. The purpose of the study is to develop and compare machine learning algorithms based on ridge regression, decision tree and extreme gradient boosting (XGBoost) for predicting the compressive strength of vibro-centrifuged variatropic concrete using a database of experimental values obtained under laboratory conditions. As a result of laboratory tests, a dataset of 664 samples was generated, describing the influence of aggressive environmental factors (freezing–thawing, chloride content, sulfate content and number of wetting–drying cycles) on the final strength characteristics of concrete. The use of analytical techniques to extract additional knowledge from data contributed to improving the resulting predictive properties of machine learning models. As a result, the average absolute percentage error (MAPE) for the best XGBoost algorithm was 2.72%, mean absolute error (MAE) = 1.134627, mean squared error (MSE) = 4.801390, root-mean-square error (RMSE) = 2.191208 and R2 = 0.93, which allows to conclude that it is possible to use “smart” algorithms to improve the life cycle management process of vibro-centrifuged variatropic concrete, by reducing the time required for the compressive strength assessment of new structures.
... The local buckling of the steel shell in a composite column with an annular section is influenced by the ratio of the pipe diameter to its thickness and the depth of the concrete core. In [58], the authors consider the issue of studying the corrosion effect on the mechanical properties of centrifuged ring-section struts using three-dimensional finite element analysis. The influence of unevenly distributed corrosion products was modeled, taking into account deformations due to volumetric expansion over 75 years. ...
Current regulatory documents and the scientific literature lack a theoretical framework and practical guidance for calculating centrifugally compacted reinforced concrete structures, taking into account the variatropy of their structure and the material’s characteristics across the section. A problem related to this research lies in the need to form a systematized, theoretical, and practical knowledge base about variatropic concretes, the importance of which has been proven by various scientists without, to date, the creation of a unified scientific methodological base. The importance of this study is linked to the need for the world’s construction projects and processes to transition to the most economically, materially, and resource-efficient types of building structures, which, of course, include structures made of variable-type concrete. This study’s objective is to fill these scientific and engineering gaps. The purpose of this study was to systematize the existing knowledge base about the technology, structure formation, and properties of variatropic concrete, using an analytical review of previously conducted studies by ourselves and others, both in Russia and abroad. A theoretical justification for the formation of the structure of variatropic materials is presented. An analysis of the basic physical and mechanical properties of variatropic concretes is carried out and the features of their microstructures are considered. The main structures created using centrifugation technology are considered. Variatropic concrete has an increased amount of mechanical characteristics compared to traditional concrete, on average by up to 45%. The durability of variatropic concrete is improved, on average, by up to 30% compared to conventional concrete.
... In harsh servicing environments, especially the marine environment, steel structures often suffer from failure of the coating and cathodic protection, resulting in different types and levels of corrosion damage [3]. Ultimate strength is the primary consideration for determining their actual safety margin [4,5]. ...
H-section columns with random pitting corrosion exhibit localized damage, making it imperative to conduct a thorough assessment in order to guarantee their long-term structural safety and integrity. This paper presents a method for constructing finite element models of randomly pitted H-section stub columns. The accuracy of the models was first validated against existing experiments. Various scenarios, accounting for different levels of pitting intensities and locations of corrosion occurrence, were considered, to elucidate the mechanisms of the reduction in ultimate strength and stiffness, as well as the failure of columns. Additionally, the influence of the width-to-thickness ratio of the plate on the ultimate strength of stub columns was also taken into account. A method to address the thickness loss resulting from random pitting corrosion was proposed for the ultimate strength assessment of randomly pitted stub columns, and its accuracy was verified based on the Chinese and European Standards. An empirical formula was proposed and verified upon the results of numerous stochastic simulations of randomly pitted H-section columns. The results demonstrated that for axially loaded H-section stub columns, both ultimate strength and stiffness decrease significantly and nonlinearly with the increase in the degree of pitting damage. Corrosion can change the failure mode of a stub column by inducing local buckling in a plate that initially satisfies the buckling criterion before the overall column failure.
... Therefore, the corrosion effect in a marine environment was simplified in this study by altering the PC bar geometry and decreasing the material properties of the spun pile (i.e., the compressive strength of the cover concrete, core concrete, and yield strength of the PC bar reduction). Furthermore, to consider the confinement effects on corroded concrete, this study employed the reduced compressive strength of confined concrete (core concrete) as well as the reduced compressive strength of unconfined concrete (cover concrete) [33]. Figure 3 illustrates the non-uniform decrease in the cross-sectional area of the PC bar ...
... Therefore, the corrosion effect in a marine environment was simplified in this study by altering the PC bar geometry and decreasing the material properties of the spun pile (i.e., the compressive strength of the cover concrete, core concrete, and yield strength of the PC bar reduction). Furthermore, to consider the confinement effects on corroded concrete, this study employed the reduced compressive strength of confined concrete (core concrete) as well as the reduced compressive strength of unconfined concrete (cover concrete) [33]. Figure 3 illustrates the non-uniform decrease in the cross-sectional area of the PC bar considered in this study to represent the changes in the PC bar geometry. ...
... Equations (7)-(9) describe the effects of corrosion on the mechanical properties of spun pile materials. The compressive strength of corroded cover concrete and corroded core concrete and the yield strength of the corroded PC bar were determined as follows [33]: ...
Fiber-based finite element analysis (FB-FEA) has been widely recognized for its ability to reproduce experimental results and is also a reliable method for evaluating the nonlinear seismic response of pile-supported wharves (PSWs). Design practice often employs frame analysis (FA) due to its easy implementation. To precisely reproduce the nonlinear seismic response of PSW using FA, it is necessary to configure mechanical properties such as the hinge property correctly. However, it is unclear whether the hinge properties proposed in previous studies can be applied to PSWs with spun piles. In this study, a novel FA method was developed to investigate the nonlinear seismic response of PSWs with corroded spun piles considering PC bar area reduction, deteriorated material properties, the bending stiffness reduction factor, and the moment–curvature relationship of the spun pile. The nonlinear seismic response of corroded PSWs was determined by performing pushover analysis using three methods: FA using the method of the previous study (FA-1), the proposed FA method (FA-2), and FB-FEA. As regards PSW foundations, vertical pile and batter pile configurations were considered. The pushover analysis results were compared in terms of several parameters, such as the natural period, plastic hinge formation, and load capacity of the corroded PSWs. The FA-2 results agreed very well with the FB-FEA results, while the FA-1 results were less precise with respect to the natural periods and load capacities of corroded PSWs. The results indicated that the bending stiffness reduction factor, moment–curvature relationship, and axial load–bending moment (P–M) capacity of the corroded spun piles should be appropriately defined. Corrosion had greater negative impacts on the compressive axial load and bending moment capacities of the spun pile than on its tensile axial load capacity.
... The effect of sulfate attack has also been evaluated on the properties and behavior of concrete products such as square steel tube columns filled with concrete [26] and twisted piles [27]. Considering reinforced concrete as a whole, in addition to concrete corrosion, it is necessary to touch upon the corrosion of reinforcing steel, which also has a negative impact on the operation of products and structures. ...
The concrete of numerous buildings and structures is at increased risk due to various kinds of aggressive pollutants. In this regard, it is necessary to implement and take additional actions, among which the so-called technological methods for concrete structure property modification are promising. These methods comprise improvement and modernization of existing technologies to produce the most effective concrete building structures before the introduction of steel reinforcement. One of the effective and proven technological and design solutions is the use of centrifuged and vibrocentrifuged concrete of an annular section with a variotropic concrete structure. The aim of the work was to study the physical and mechanical properties of variotropic concretes of annular structures when exposed to sulfate attack. As a result of the cyclic impact of sulfate attack, the mass loss of vibrocentrifuged concrete was the smallest in comparison with centrifuged (17% less) and vibrated concrete (37% less). The loss of cube and prism strength of vibrocentrifuged concrete was the smallest in comparison with centrifuged (20% and 18% less, respectively) and vibrated concrete (42% and 38% less, respectively). The sulfate attack rate, as a depth of penetration and concrete destruction, was 46% less for vibrocentrifuged concrete than for centrifuged concrete and 65% less than for vibrated concrete.
