Research

Open AccessArticle

Stiffness of Experimentally Tested Horizontally Loaded Walls and Timber-Framed Modular Building

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Czesław Miedziałowski

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Krzysztof Robert Czech

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Marta Nazarczuk

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Marta Kosior-Kazberuk

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Anna Żakowicz

Materials 2023, 16(18), 6229; https://doi.org/10.3390/ma16186229 - 15 Sep 2023

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Abstract

This paper presents an overview of representative up-to-date research and the authors’ own experimental results from tests of wall elements and a horizontally loaded timber-framed modular building. The research has been conducted in connection with the development of timber-based structures in recent years. [...] Read more.

This paper presents an overview of representative up-to-date research and the authors’ own experimental results from tests of wall elements and a horizontally loaded timber-framed modular building. The research has been conducted in connection with the development of timber-based structures in recent years. In the present research, wall elements and modules of timber-frame construction with life-size dimensions were used. So far, these types of structures have mainly been tested in laboratories—especially with regard to anchoring and cyclic loading. An experimental testing was carried out on a natural scale in two stages based on the standard procedure described in EN 594. In the first stage, wall panels were tested. In the second stage, tests were carried out on a complete four-storey building. Dowel fasteners were used to fix the sheathing to the load-bearing wall structures. Additionally, the sheathing was glued to the timber frame of the walls. The same type of wall element was used for the construction of the tested building. Horizontal loads were applied at the height of the top of the walls in both stages. The building loads were applied in a direction perpendicular to the longitudinal axis of the modules. Based on test data, the stiffnesses of the wall panels and the whole building were derived, as well as the type of interaction between the modules and the influence of the walls on the spatial work of the building. On the basis of the conducted studies, both the stiffness of the walls in different configurations and the stiffness of the complete building were determined, as well as the nature of the interaction of neighbouring modules and the influence of wall connections on the 3D working of the building. The results show that the stiffness of the building in the horizontal plane in the direction of the applied load is almost twice as high as the sum of the stiffnesses of the building walls in the same direction. Full article

(This article belongs to the Special Issue Testing of Materials and Elements in Civil Engineering (3rd Edition))

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Open AccessArticle

Influence of Fire Exposition of Fibre-Cement Boards on Their Microstructure

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Materials 2023, 16(18), 6153; https://doi.org/10.3390/ma16186153 - 10 Sep 2023

Viewed by 343

Abstract

The diagnostics of materials, elements and structures after fire exposure are very complicated. Researchers carrying out such diagnostics encounter difficulties at the very beginning, e.g., how to map fire conditions. In this publication, the authors focused on the analysis of the fibre-cement composite [...] Read more.

The diagnostics of materials, elements and structures after fire exposure are very complicated. Researchers carrying out such diagnostics encounter difficulties at the very beginning, e.g., how to map fire conditions. In this publication, the authors focused on the analysis of the fibre-cement composite used as facade cladding. The fibre-cement boards are construction products used in civil engineering. The fibre-cement boards are characterised by two phases: the matrix phase and the dispersed phase. The analysis of fibre-cement composite was performed using non-destructive methods. The use of non-destructive methods in the future will allow for the analysis of facades after fires without the need to obtain large elements, which will significantly reduce costs while increasing safety. The aim of the work was to determine internal changes in the microstructure of fibre-cement boards after exposure to fire. The degraded samples were compared with reference samples in the evaluation of the microstructure. An analysis was performed using a scanning electron microscope, images of backscattered electrons (BSE) and maps obtained using Energy Dispersive X-ray Spectroscopy (EDX), which allowed conclusions to be drawn. The observed changes were presented in the form of photos showing changes in the composition of the plates, and they were commented on. It should be noted that fire temperatures act destructively, and a number of changes can be observed in the microstructure. The results of the work indicate that, in the future, the use of non-destructive methods will make it possible to assess the degree of degradation of the façade after a fire. Full article

(This article belongs to the Special Issue Testing of Materials and Elements in Civil Engineering (3rd Edition))

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Open AccessArticle

Computational Complexity and Its Influence on Predictive Capabilities of Machine Learning Models for Concrete Mix Design

by

Patryk Ziolkowski

Materials 2023, 16(17), 5956; https://doi.org/10.3390/ma16175956 - 30 Aug 2023

Viewed by 281

Abstract

The design of concrete mixtures is crucial in concrete technology, aiming to produce concrete that meets specific quality and performance criteria. Modern standards require not only strength but also eco-friendliness and production efficiency. Based on the Three Equation Method, conventional mix design methods [...] Read more.

The design of concrete mixtures is crucial in concrete technology, aiming to produce concrete that meets specific quality and performance criteria. Modern standards require not only strength but also eco-friendliness and production efficiency. Based on the Three Equation Method, conventional mix design methods involve analytical and laboratory procedures but are insufficient for contemporary concrete technology, leading to overengineering and difficulty predicting concrete properties. Machine learning-based methods offer a solution, as they have proven effective in predicting concrete compressive strength for concrete mix design. This paper scrutinises the association between the computational complexity of machine learning models and their proficiency in predicting the compressive strength of concrete. This study evaluates five deep neural network models of varying computational complexity in three series. Each model is trained and tested in three series with a vast database of concrete mix recipes and associated destructive tests. The findings suggest a positive correlation between increased computational complexity and the model’s predictive ability. This correlation is evidenced by an increment in the coefficient of determination (R²) and a decrease in error metrics (mean squared error, Minkowski error, normalized squared error, root mean squared error, and sum squared error) as the complexity of the model increases. The research findings provide valuable insights for increasing the performance of concrete technical feature prediction models while acknowledging this study’s limitations and suggesting potential future research directions. This research paves the way for further refinement of AI-driven methods in concrete mix design, enhancing the efficiency and precision of the concrete mix design process. Full article

(This article belongs to the Special Issue Testing of Materials and Elements in Civil Engineering (3rd Edition))

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Open AccessArticle

A Constitutive Model for Describing the Tensile Response of Woven Polyethylene Terephthalate Geogrids after Damage

by

Giovani Lombardi

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Margarida Pinho-Lopes

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António Miguel Paula

and

António Bastos Pereira

Materials 2023, 16(15), 5384; https://doi.org/10.3390/ma16155384 - 31 Jul 2023

Viewed by 272

Abstract

A constitutive model was used to describe the tensile response of two woven Polyethylene Terephthalate (PET) geogrids, before and after mechanical damage. The model parameters of undamaged and damaged specimens were estimated via numerical regressions of test results. For each sample, the experimental [...] Read more.

A constitutive model was used to describe the tensile response of two woven Polyethylene Terephthalate (PET) geogrids, before and after mechanical damage. The model parameters of undamaged and damaged specimens were estimated via numerical regressions of test results. For each sample, the experimental and fitted tensile strengths were statistically compared using hypothesis tests. For each geogrid, tensile load–strain curves of damaged samples were drawn by applying scaling factors to the plot of the undamaged sample. The curve fittings resulted in high R² values for undamaged and damaged specimens of the geogrids. For most samples, there was no significant mean difference between the experimental and fitted tensile strength. The model allowed us to describe the load–strain curve of a geogrid from its tensile properties: ε_max, T_max and J_i. Regardless of the type of damage (in laboratory or in situ), the model was able to describe the load–strain curves of damaged samples using data from undamaged samples and scaling factors. Full article

(This article belongs to the Special Issue Testing of Materials and Elements in Civil Engineering (3rd Edition))

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Open AccessArticle

Effect of Vibration Procedure on Particle Distribution of Cement Paste

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Materials 2023, 16(7), 2600; https://doi.org/10.3390/ma16072600 - 24 Mar 2023

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Abstract

Vibration procedures significantly affect the performances of cement-based materials. However, studies on the distribution of certain particles within cement-based materials are limited due to the complexity and difficulty of identifying each specific particle. This paper presents a new method for simulating and quantifying [...] Read more.

Vibration procedures significantly affect the performances of cement-based materials. However, studies on the distribution of certain particles within cement-based materials are limited due to the complexity and difficulty of identifying each specific particle. This paper presents a new method for simulating and quantifying the movements of particles within cement paste through the use of “tagged materials”. By separating the tagged particles from the cement paste after vibration, the distribution of the particles in the cement paste can be calculated statistically. The effect of the vibration time and frequency, fresh behavior, and powder characteristics of cement paste on particle motions are investigated. The results demonstrate that when the vibration exceeds 1800 s, it induces a significant uneven dispersion of microparticles. This effect is more pronounced at low viscosities (<1 Pa·s) of cement paste or high vibration frequencies (>200 Hz). Larger and denser particles exhibit greater dispersion. This method provides a valuable tool for investigating the theory of particle motion in cement paste, which is crucial for understanding the influence of vibration on the properties of cement-based materials. Full article

(This article belongs to the Special Issue Testing of Materials and Elements in Civil Engineering (3rd Edition))

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Open AccessArticle

Long-Term Prestress Loss Calculation Considering the Interaction of Concrete Shrinkage, Concrete Creep, and Stress Relaxation

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Materials 2023, 16(6), 2452; https://doi.org/10.3390/ma16062452 - 19 Mar 2023

Viewed by 1094

Abstract

In order to accurately calculate the long-term prestress losses of prestressed tendons, a time-varying model of long-term prestress loss considering the interaction between concrete shrinkage, creep, and the stress relaxation of prestressed tendons was constructed. Then, a method for calculating the long-term prestress [...] Read more.

In order to accurately calculate the long-term prestress losses of prestressed tendons, a time-varying model of long-term prestress loss considering the interaction between concrete shrinkage, creep, and the stress relaxation of prestressed tendons was constructed. Then, a method for calculating the long-term prestress losses of concrete structures was developed. A long-term prestress loss test of a prestressed concrete T-beam in a long-term field test environment was carried out. The measured values of long-term prestress losses are compared with the calculated results of JTG 3362-2018, AASHTO LRFD-2007, and the time-varying law model. The results show that the long-term effective tension of the T-beam decreases gradually with the increase in the load holding time. At the beginning of loading, the tensile force changes rapidly and then gradually slows down. The later the tensile age or the higher the initial loading stress level, the smaller the long-term prestress losses of the prestressed tendons. The long-term prestress loss values calculated by JTG 3362-2018, AASHTO LRFD-2007, and the time-varying law model increase with the increase in the load holding time. In the early stage of loading, the rate of change slows down and tends to be stable. The calculated results of JTG 3362-2018 and AASHTO LRFD-2007 are significantly different from the measured values. However, the calculated results of the time-varying law model are in good agreement with the measured values. The average coefficients of variation of the long-term prestress loss calculated by JTG 3362-2018, AASHTO LRFD-2007, and the time-varying law model are 17%, 10%, and 5%, respectively. The time-varying law model of the long-term prestress losses of prestressed tendons is accurate, and the long-term prestress loss of prestressed reinforcement can be predicted effectively. Full article

(This article belongs to the Special Issue Testing of Materials and Elements in Civil Engineering (3rd Edition))

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Open AccessArticle

Modelling of Resinous Material Filling Expansion Joints in Reinforced Concrete Structures

by

Krzysztof Schabowicz

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Grzegorz Waśniewski

and

Krzysztof Wróblewski

Materials 2023, 16(5), 2011; https://doi.org/10.3390/ma16052011 - 28 Feb 2023

Viewed by 691

Abstract

This paper is a continuation of the research and analysis to estimate hyperelastic material constants when only uniaxial test data are available. The FEM simulation was expanded and the results obtained from three-dimensional and plane strain expansion joint models were compared and discussed. [...] Read more.

This paper is a continuation of the research and analysis to estimate hyperelastic material constants when only uniaxial test data are available. The FEM simulation was expanded and the results obtained from three-dimensional and plane strain expansion joint models were compared and discussed. The original tests were carried out for a gap with a width of 10 mm, whereas in the case of axial stretching, the stresses and internal forces caused by the leading deformations were recorded for a smaller gap, and the axial compression was also recorded. The differences in the global response between the three- and two-dimensional models were also considered. Finally, using FEM simulations, the values of stresses and cross-sectional forces in the filling material were determined, which can be the basis for the design of expansion joints geometry. The results of these analyses could form the basis of guidelines for the design of expansion joint gaps filled with material, ensuring the waterproofing of the joint. Full article

(This article belongs to the Special Issue Testing of Materials and Elements in Civil Engineering (3rd Edition))

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Open AccessArticle

Dynamic Diagnostic Tests and Numerical Analysis of the Foundations for Turbine Sets

by

Jerzy Szolomicki

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Grzegorz Dmochowski

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Maciej Roskosz

Materials 2023, 16(4), 1421; https://doi.org/10.3390/ma16041421 - 08 Feb 2023

Viewed by 702

Abstract

This paper shows current trends in testing and numerical analysis of dynamic loading in relation to a real frame foundation for a turbogenerator set. The analysis of the machine’s foundations, which are subjected to static and dynamic loads, is a complex problem combining [...] Read more.

This paper shows current trends in testing and numerical analysis of dynamic loading in relation to a real frame foundation for a turbogenerator set. The analysis of the machine’s foundations, which are subjected to static and dynamic loads, is a complex problem combining the issues of geotechnics, structural engineering, and vibration theory. The authors present a case study of the assessment of the foundation’s technical condition. The main objective of this study is to perform and compare experimental and numerical dynamic analysis which includes the measurement of the acceleration, speed, and amplitude of the natural vibrations of the foundation during the operational speed of the turbogenerator. In addition, auxiliary material tests were carried out to fully diagnose the foundation and obtain the material properties required for the numerical analysis. They included both destructive and non-destructive of concrete strength, the evaluation of the degree of its carbonation, and the scanning of the reinforcement distribution. The research presented in the paper is intended to facilitate the preparation of appropriate data for the design of the foundation renovation and strengthening. Full article

(This article belongs to the Special Issue Testing of Materials and Elements in Civil Engineering (3rd Edition))

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