Research

22 pages, 10638 KiB

Open AccessArticle

Strength of Hybrid Steel-BFRP Reinforced Concrete Beams with Openings in the D-Region Strengthened Internally and Externally

by Sameh Yehia, Bader Faihan and Arafa M. A. Ibrahim

Buildings 2023, 13(10), 2522; https://doi.org/10.3390/buildings13102522 - 05 Oct 2023

Viewed by 622

Abstract

The opened beams always confused the designers due to the guidelines missing. In this research, six hybrid beams reinforced with mixed steel and basalt fiber-reinforced polymer (BFRP) bars and having constant cross-sections of 150 mm × 300 mm and a clear span of [...] Read more.

The opened beams always confused the designers due to the guidelines missing. In this research, six hybrid beams reinforced with mixed steel and basalt fiber-reinforced polymer (BFRP) bars and having constant cross-sections of 150 mm × 300 mm and a clear span of 1800 mm were cast and tested under a four-point loading setup. Generally, five beams had symmetrical rectangular openings with dimensions of 150 mm × 250 mm located at a distance of 250 mm (equivalent to the beam effective depth) from the beam support, while an additional solid beam served as a control. The studied parameters included the effect of using internal reinforcement (steel or BFRP bars) provided adjacent to the opening sides or by incorporating an external BFRP sheet around the opening corners. Also, double enhancement with internal steel reinforcement bars together with external strengthening BFRP sheet was investigated. The relevant results showed that the opened beam without enhancement lost 75% of the maximum load compared with the solid beam. Placing internal steel or BFRP bars around the openings increased the maximum load by 62% and 60%, respectively, compared to the non-enhanced opened beams. Using an external BFRP sheet to strengthen the opening corners of the beam enhanced the maximum load by 76% compared with the non-enhanced opened beam. Consequently, by combining both the internal steel reinforcement and external BFRP sheet around the openings, the maximum load increased by 137% compared with the non-enhanced opened beam. Ultimately, a numerical analysis of the three-dimensional finite element model was performed to confirm the experimental findings, and the relevant results showed compatibility correlations with the experimental ones. Also, the effect of various parameters such as BFRP reinforcement ratio and number of BFRP sheet layers around the openings was investigated by adapting the validated numerical model. Full article

(This article belongs to the Special Issue Editorial Board Members’ Collection Series: 'Building Materials and Repair & Renovation')

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57 pages, 6719 KiB

Open AccessArticle

Fiber Reinforced Polymer (FRP) Confined Circular Concrete Columns: An Experimental Overview

by Maria K. Valasaki and Christos G. Papakonstantinou

Buildings 2023, 13(5), 1248; https://doi.org/10.3390/buildings13051248 - 09 May 2023

Cited by 3 | Viewed by 2045

Abstract

Fiber-reinforced polymers (FRPs) are widely used as composite materials in civil engineering applications to rehabilitate or strengthen reinforced-concrete structural elements. The purpose of this study was to compile an extensive and up-to-date experimental database based on the compressive tests conducted on circular confined [...] Read more.

Fiber-reinforced polymers (FRPs) are widely used as composite materials in civil engineering applications to rehabilitate or strengthen reinforced-concrete structural elements. The purpose of this study was to compile an extensive and up-to-date experimental database based on the compressive tests conducted on circular confined concrete structural elements using FRP composite materials. Strict criteria were implemented during the collection of the experimental data to minimize uncertainty and maximize uniformity. In order to compare the results, the collected data were divided into two categories based on the type of confinement, namely FRP wrapped and FRP tube encased. A detailed database of 1470 experimental test results on FRP-confined concrete cylindrical specimens demonstrated the specimens’ geometry, the jacketing materials’ physical and mechanical properties, and the effect of the confinement on the axial compressive strength and strain. The analysis of the database led to important observations on the parameters that influence FRP-confined concrete’s behavior. The unconfined concrete strength seems to be inversely related to the confinement efficiency. The confinement efficiency is quite limited in high-strength concrete specimens. Carbon fibers tend to provide greater confinement effectiveness, while the FRP axial rigidity was found to contribute significantly to the effect of confinement. Glass and aramid fibers seem to perform equally well, regardless of the confinement method. An interesting finding is that while FRP-wrapped specimens perform similarly to tube-encased specimens in terms of increases in compressive strength, the latter are associated with larger increases in ultimate axial strains. Full article

(This article belongs to the Special Issue Editorial Board Members’ Collection Series: 'Building Materials and Repair & Renovation')

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15 pages, 3146 KiB

Open AccessArticle

Surface Activation of Wax-Based Additives to Enhance Asphalt Rheological Properties via Rotating Plasma Treatment

by Qiwei Chen, Yanqing Li, Zengyao Lin and Huayang Yu

Buildings 2023, 13(2), 514; https://doi.org/10.3390/buildings13020514 - 14 Feb 2023

Cited by 2 | Viewed by 1589

Abstract

Wax-based additives have been widely used in asphalt pavement for their preferable environmental benefits. However, poor compatibility between wax-based warm mix additives and asphalt easily leads to precipitation of wax and cracking of asphalt pavement. Plasma treatment can effectively modify the surface of [...] Read more.

Wax-based additives have been widely used in asphalt pavement for their preferable environmental benefits. However, poor compatibility between wax-based warm mix additives and asphalt easily leads to precipitation of wax and cracking of asphalt pavement. Plasma treatment can effectively modify the surface of various materials. This study applies plasma treatment to improve the surface properties of wax-based additives for compatibility improvement in asphalt binder. Compatibility of two different wax-base additives in asphalt binder before and after surface treatment is investigated via cigar tube test and morphology test. In parallel, rheological properties of wax-modified asphalt are characterized from the perspectives of rotational viscosity, rutting resistance, and fatigue performance. Results show the enhanced surface roughness and chemical activity of wax-based additives after plasma treatment. The adhesion between waxes and the asphalt matrix is significantly improved. Waxes within binder are uniformly dispersed after plasma treatment. The incorporation of surface activated wax helps to promote the viscosity reduction of asphalt binder. Furthermore, the high-temperature performance of wax-based asphalt after surface activation treatment of wax is significantly improved, especially for fatty acid amide waxes. As for fatigue performance, plasma treatment improves the fatigue resistance from a compatibility perspective. Therefore, plasma has great promise for facilitating wax-modified asphalt properties from a compatibility perspective. Full article

(This article belongs to the Special Issue Editorial Board Members’ Collection Series: 'Building Materials and Repair & Renovation')

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14 pages, 3511 KiB

Open AccessArticle

Experimental Study on Impact Behavior of Concrete Panel with and without Polypropylene Macrofibers

by Kwangsoo Youm and Jiho Moon

Buildings 2023, 13(2), 303; https://doi.org/10.3390/buildings13020303 - 19 Jan 2023

Cited by 3 | Viewed by 1014

Abstract

Macrofibers have often been used to increase the tensile strength, durability, crack resistance, spalling, impact resistance, and toughness of concrete. However, the impact behavior of fiber-reinforced concrete (FRC) structures is quite different from their static behavior, and the effectiveness of macrofibers in improving [...] Read more.

Macrofibers have often been used to increase the tensile strength, durability, crack resistance, spalling, impact resistance, and toughness of concrete. However, the impact behavior of fiber-reinforced concrete (FRC) structures is quite different from their static behavior, and the effectiveness of macrofibers in improving impact resistance should be carefully evaluated. In this study, the impact behavior of FRC with polypropylene (PP) macrofibers was studied through a series of drop-weight impact tests. First, the material characteristics of the FRC with PP fibers under static conditions were evaluated. Test specimens were constructed and drop-weight impact tests were performed. The main parameters were the presence or absence of PP fibers and the drop height, which is related to the magnitude of the impact energy. From the results, it can be found that the crack width of the FRC specimen was smaller than the normal concrete specimen for a similar residual deflection after the impact test due to the bridging effect of the macrofibers. However, the effect of PP fibers on the impact resistance was not significant, even though there was a considerable increase in tensile and flexural performance under static conditions, since the hardening effect after the sharp reduction in strength shown in the static test of FRC is not effective in the impact test. Full article

(This article belongs to the Special Issue Editorial Board Members’ Collection Series: 'Building Materials and Repair & Renovation')

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17 pages, 7110 KiB

Open AccessArticle

Experimental and Numerical Investigation of an Innovative 3DPC Thin-Shell Structure

by Wenfeng Du, Liming Zhu, Hao Zhang, Zhiyong Zhou, Kewei Wang and Nasim Uddin

Buildings 2023, 13(1), 233; https://doi.org/10.3390/buildings13010233 - 13 Jan 2023

Cited by 2 | Viewed by 1361

Abstract

The development and application of new Fiber Reinforced Polymer (FRP) material and 3D printing construction technology provide a basis for making up for the shortcomings of traditional thin-shell structures and building new thin-shell structures with better performance. In this paper, a new 3D [...] Read more.

The development and application of new Fiber Reinforced Polymer (FRP) material and 3D printing construction technology provide a basis for making up for the shortcomings of traditional thin-shell structures and building new thin-shell structures with better performance. In this paper, a new 3D Printing Composite (3DPC) thin-shell structure is proposed, which is prepared using a FRP plate as a permanent base mold and combining it with 3D printing cement technology. Both the typical experiment and finite element numerical simulation analysis of the 3DPC thin-shell structure are carried out. The results show that the maximum load capacity of the 3DPC thin-shell structure is increased by 53.3% as compared with the corresponding traditional concrete thin-shell structure. The presence of the FRP sheet effectively delays the generation of initial cracks and enhances the ductility of components. Full article

(This article belongs to the Special Issue Editorial Board Members’ Collection Series: 'Building Materials and Repair & Renovation')

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18 pages, 10770 KiB

Open AccessArticle

Characterization of Mortar from Casa Barbot (Portugal), a Case Study from the Beginning of the 20th Century

by Hamid Maljaee, António Santos Silva and Ana Velosa

Buildings 2023, 13(1), 232; https://doi.org/10.3390/buildings13010232 - 13 Jan 2023

Cited by 2 | Viewed by 1306

Abstract

The popularity of natural cement (Roman cement) in buildings from the late 19th and the beginning of the 20th century and the high diversity of characteristics of natural cement demand research of mortar and binders used in the buildings of this period in [...] Read more.

The popularity of natural cement (Roman cement) in buildings from the late 19th and the beginning of the 20th century and the high diversity of characteristics of natural cement demand research of mortar and binders used in the buildings of this period in Portugal. Understanding the type of binder used in the historic buildings will help the project/intervention team to make the best decisions in terms of the development of compatible mortars for historical conservation purposes. Casa Barbot is one of the Art Nouveau examples of the beginning of the 20th century in Portugal. The garden of this building is characterized by peculiar elements in terms of materials and architecture. Full characterization of the mortars employed in the construction of this building as well as identification of the used binder is the main objective of this study. The study comprises a wide range of laboratory characterization techniques such as X-ray fluorescence (XRF), X-ray diffraction (XRD), petrography, open porosity, density, water absorption by capillarity, and compressive strength. The results show the diversity of compositional characteristics in the mortars used in the decorative elements in the period garden of Casa Barbot. All mortars are composed of Portland cement with a mix of additives such as blast furnace slag, limestone filler, air lime, and the occasional presence of charcoal. The results raise doubt about the use of natural cement as stated in the historical documents. This study will broaden the scientific knowledge of the materials of that period in Portugal to provide a comprehensive plan for the preservation of historical buildings. Full article

(This article belongs to the Special Issue Editorial Board Members’ Collection Series: 'Building Materials and Repair & Renovation')

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33 pages, 11764 KiB

Open AccessArticle

Nonlinear Regression Prediction of Mechanical Properties for SMA-Confined Concrete Cylindrical Specimens

by Saeed Eilbeigi, Mohammadreza Tavakkolizadeh and Amir R. Masoodi

Buildings 2023, 13(1), 112; https://doi.org/10.3390/buildings13010112 - 31 Dec 2022

Cited by 3 | Viewed by 1230

Abstract

In order to achieve active confinement in concrete elements, researchers have recently employed smart materials called shape memory alloys (SMA). Several empirical relationships have been widely used to predict the behavior of confined concrete. To develop more accurate relations for predicting the behavior [...] Read more.

In order to achieve active confinement in concrete elements, researchers have recently employed smart materials called shape memory alloys (SMA). Several empirical relationships have been widely used to predict the behavior of confined concrete. To develop more accurate relations for predicting the behavior of concrete actively confined with SMA spirals, it is necessary to obtain new relations for determining the peak compressive stress and the corresponding strain in addition to the ultimate stress and strain. For this purpose, existing data from 42 specimens of plain concrete cylindrical specimens confined with SMA spirals and subjected to uniaxial compression were collected. Then, by using MATLAB and SigmaPlot software, nonlinear regression analyses were conducted to obtain the optimum relations. The best equations were selected using multiple error criteria of root mean square error (RMSE) and R-squared (R²). Finally, the accuracy of the proposed relations was compared to the existing relations for active concrete confinement which showed better accuracy. Full article

(This article belongs to the Special Issue Editorial Board Members’ Collection Series: 'Building Materials and Repair & Renovation')

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14 pages, 7081 KiB

Open AccessArticle

Using Optimization Algorithms-Based ANN to Determine the Temperatures in Timber Exposed to Fire for a Long Duration

by Mehdi Nikoo, Ghazanfarah Hafeez and Paulo Cachim

Buildings 2022, 12(12), 2265; https://doi.org/10.3390/buildings12122265 - 19 Dec 2022

Cited by 2 | Viewed by 1186

Abstract

The article investigates the temperature prediction in rectangular timber cross-sections exposed to fire. Timber density, exposure time, and the point coordinates within the cross-section are treated as inputs to determine the temperatures. A total of 54,776 samples of wood cross-sections with a variety [...] Read more.

The article investigates the temperature prediction in rectangular timber cross-sections exposed to fire. Timber density, exposure time, and the point coordinates within the cross-section are treated as inputs to determine the temperatures. A total of 54,776 samples of wood cross-sections with a variety of characteristics were considered in this study. Of the sample data, 70% was dedicated to training the networks, while the remaining 30% was used for testing the networks. Feed-forward networks with various topologies were employed to examine the temperatures of timber exposed to fire for more than 1500 s. The weight of the artificial neural network was optimized using bat and genetic algorithms. The results conclude that both algorithms are efficient and accurate tools for determining the temperatures, with the bat algorithm being marginally superior in accuracy than the genetic algorithm. Full article

(This article belongs to the Special Issue Editorial Board Members’ Collection Series: 'Building Materials and Repair & Renovation')

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