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21 pages, 3633 KiB  
Article
Shear Mechanism of Precast Segmental Concrete Beam Prestressed with Unbonded Tendons
by Wu-Tong Yan, Lei Yuan, Yong-Hua Su and Zi-Wei Song
Buildings 2025, 15(15), 2668; https://doi.org/10.3390/buildings15152668 - 28 Jul 2025
Viewed by 224
Abstract
The shear tests are conducted on six precast segmental concrete beams (PSCBs) in this paper. A new specimen design scheme is presented to compare the effects of segmental joints on the shear performance of PSCBs. The failure modes, shear strength, structural deflection, stirrup [...] Read more.
The shear tests are conducted on six precast segmental concrete beams (PSCBs) in this paper. A new specimen design scheme is presented to compare the effects of segmental joints on the shear performance of PSCBs. The failure modes, shear strength, structural deflection, stirrup strain, and tendon stress are recorded. The factors of shear span ratio, the position of segmental joints, and hybrid tendon ratio are focused on, and their effects on the shear behaviors are compared. Based on the measured responses, the shear contribution proportions of concrete segments, prestressed tendons, and stirrups are decomposed and quantified. With the observed failure modes, the truss–arch model is employed to clarify the shear mechanism of PSCBs, and simplified equations are further developed for predicting the shear strength. Using the collected test results of 30 specimens, the validity of the proposed equations is verified with a mean ratio of calculated-to-test values of 0.96 and a standard deviation of 0.11. Furthermore, the influence mechanism of shear span ratio, segmental joints, prestressing force, and hybrid tendon ratio on the shear strength is clarified. The increasing shear span ratio decreases the inclined angle of the arch ribs, thereby reducing the shear resistance contribution of the arch action. The open joints reduce the number of stirrups passing through the diagonal cracks, lowering the shear contribution of the truss action. The prestressing force can reduce the inclination of diagonal cracks, improving the contribution of truss action. The external unbonded tendon will decrease the height of the arch rib due to the second-order effects, causing lower shear strength than PSCBs with internal tendons. Full article
(This article belongs to the Special Issue Advances in Steel-Concrete Composite Structure—2nd Edition)
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25 pages, 4965 KiB  
Article
Towards Selecting an Optimal Bonding Test Method for Rebar–Concrete: Comparison Between Pull-Out Test and Full-Beam Test
by Sisi Chao, Chenghua Li, Jiahong Dong and Ziliang Lu
Buildings 2025, 15(13), 2375; https://doi.org/10.3390/buildings15132375 - 7 Jul 2025
Viewed by 400
Abstract
There are many methods for evaluating the bond behavior between rebar and concrete. For certain experimental purposes, selecting the ideal method for testing the rebar–concrete bonding properties is often a controversial problem. The most representative single-end pull-out test method and the full-beam test [...] Read more.
There are many methods for evaluating the bond behavior between rebar and concrete. For certain experimental purposes, selecting the ideal method for testing the rebar–concrete bonding properties is often a controversial problem. The most representative single-end pull-out test method and the full-beam test method were applied in this work to conduct bonding tests between rebar and concrete. Considering the influence of the concrete strength, bonding length, stirrup, and rebar slotting, these two testing strategies are compared and analyzed in terms of the specimen failure mode, bonding strength, bond–slip curve, and rebar stress distribution. Suggestions are offered regarding the selection of an appropriate method for evaluating the bond behavior between rebar and concrete based on an comparative analysis of the two tested approaches. The results presented herein provide a basis for the preparation of relevant test method standards. Full article
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28 pages, 7919 KiB  
Article
Numerical Study on Shear-Oriented Parameters in RC Beams with Openings Reinforced by Fe-SMA Rebars
by Mohamed Elkafrawy, Ahmed Khalil, Rami Hawileh and Mohammad AlHamaydeh
Buildings 2025, 15(12), 2028; https://doi.org/10.3390/buildings15122028 - 12 Jun 2025
Viewed by 1380
Abstract
Reinforced concrete (RC) beams with openings in shear spans exhibited a significantly reduced structural performance due to disruptions in load transfer mechanisms. This numerical study investigated the influence of pre-stressed iron-based Shape Memory Alloy (Fe-SMA) rebars on the behavior of RC beams with [...] Read more.
Reinforced concrete (RC) beams with openings in shear spans exhibited a significantly reduced structural performance due to disruptions in load transfer mechanisms. This numerical study investigated the influence of pre-stressed iron-based Shape Memory Alloy (Fe-SMA) rebars on the behavior of RC beams with web openings, focusing on the effect of shear-oriented design parameters, including the stirrup spacing, stirrup diameter, and horizontal reinforcement around the opening. A nonlinear finite element analysis (NLFEA) was conducted using ABAQUS/CAE software 2020 to simulate the response of RC beams under these conditions. The results showed that the presence of web openings in RC beams reduced the ultimate load capacity and stiffness. However, the pre-stressed Fe-SMA reinforcement effectively mitigated these adverse effects, restoring much of the solid beam’s performance. Among the studied parameters, reducing the stirrup spacing significantly improved the load-bearing capacity, with the smallest spacing (100 mm) restoring 86% of the solid beam’s ultimate load. Increasing the Fe-SMA stirrup diameter further enhanced performance, with T16 stirrups recovering 92% of the solid beam’s ultimate load capacity. The most substantial improvement occurred when horizontal reinforcement was introduced, particularly with T16 stirrups, achieving a 95% load recovery, nearly matching the solid RC beam structural performance. These findings demonstrated the promising potential of pre-stressed Fe-SMA reinforcement as a viable solution for restoring the structural strength of RC beams with web openings. Full article
(This article belongs to the Special Issue Strengthening and Rehabilitation of Structures or Buildings)
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21 pages, 808 KiB  
Article
Data-Driven Approach to Derive Equation for Predicting Ultimate Shear Strength of Reinforced Concrete Beams Without Stirrups
by Menghay Phoeuk, Dong-Yeong Choi, Suchart Limkatanyu and Minho Kwon
Materials 2025, 18(11), 2446; https://doi.org/10.3390/ma18112446 - 23 May 2025
Viewed by 462
Abstract
Shear failure in reinforced concrete (RC) beams is abrupt and brittle, occurs without warning, and leaves no opportunity for internal stress redistribution. Despite the critical need for accurate shear strength assessment, existing methods vary widely across regions, leading to inconsistencies in practice. This [...] Read more.
Shear failure in reinforced concrete (RC) beams is abrupt and brittle, occurs without warning, and leaves no opportunity for internal stress redistribution. Despite the critical need for accurate shear strength assessment, existing methods vary widely across regions, leading to inconsistencies in practice. This study presents a unified shear strength equation for non-prestressed rectangular RC beams without stirrups, developed for simplicity and broad applicability. The model requires only basic geometric and material properties and applies to both shear-slender and non-shear-slender beams. It was formulated using a data-driven approach that combines an extensive experimental database collected up to 2007 with advanced computational techniques, including Artificial Neural Networks, Generative Adversarial Networks, and Bayesian optimization. The proposed equation was evaluated against established shear provisions, such as ACI 318-25 and CSA A23.3-24, and benchmarked with an experimental database. The results show that the model improves prediction accuracy, reduces uncertainty, and provides a more consistent method for shear strength assessment. The robustness of the equation was further confirmed through additional experimental database gathered after 2007, demonstrating strong agreement with test results and lower prediction uncertainty than current code provisions. These findings support the potential adoption of the proposed equation in engineering practice. Full article
(This article belongs to the Section Construction and Building Materials)
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31 pages, 9883 KiB  
Article
Flexural Behavior of Desert Sand Concrete-Filled Steel Tube: Experimental Validation, FEM Analysis, and Design Formulas
by Chao-Cheng Zhang, Fa-Xing Ding, Said Ikram Sadat, Fei Lyu, Xin-Yu Huang, Rui Gao, Tao Yu and Yu-Lin Liu
Materials 2025, 18(10), 2371; https://doi.org/10.3390/ma18102371 - 20 May 2025
Cited by 1 | Viewed by 421
Abstract
This study investigates the flexural performance of desert sand concrete-filled steel tube (DS-CFST) members through experimental validation and finite element modeling (FEM). An extensive database of square and circular CFST specimens subjected to pure bending was analyzed to validate an ABAQUS-based FEM. Parametric [...] Read more.
This study investigates the flexural performance of desert sand concrete-filled steel tube (DS-CFST) members through experimental validation and finite element modeling (FEM). An extensive database of square and circular CFST specimens subjected to pure bending was analyzed to validate an ABAQUS-based FEM. Parametric studies evaluated the influence of steel yield strength, steel ratio, stirrup confinement, and desert sand replacement ratio (r) on ultimate bending moment, stiffness, and failure modes. The results indicated that steel yield strength and section geometry significantly affected bending capacity, while desert sand substitution (r ≤ 1) had a negligible impact on capacity, reducing it by less than 3%. The FEM accurately predicted buckling patterns, moment-curvature relationships, and failure modes. New design formulas for predicting ultimate bending moment and flexural stiffness were proposed, demonstrating superior accuracy (mean error < 1%) compared to existing design codes (AIJ, AISC, GB). This study highlights that DS-CFST members, particularly circular sections, offer robust flexural performance, with enhanced ductility and uniform stress distribution. The findings underscore the potential of using desert sand as a sustainable material in concrete-filled steel tube structures without compromising structural integrity. Full article
(This article belongs to the Special Issue Advances in Compressive Strength of Cement-Based Materials)
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20 pages, 5910 KiB  
Article
The Restraint Mechanism of High-Strength Rectangular Spiral Stirrup Confined Fiber Reinforced Concrete
by Pengyu Fan, Huajing Zhao and Weitong Liu
Buildings 2025, 15(8), 1345; https://doi.org/10.3390/buildings15081345 - 17 Apr 2025
Viewed by 333
Abstract
To reveal the confinement mechanism of high-strength rectangular spiral stirrups (HRSSs) on fiber-reinforced concrete, this study designed and conducted axial compression tests on 20 HRSS-confined fiber-reinforced concrete columns. The effects of stirrup spacing, stirrup strength, and concrete strength on the strength and ductility [...] Read more.
To reveal the confinement mechanism of high-strength rectangular spiral stirrups (HRSSs) on fiber-reinforced concrete, this study designed and conducted axial compression tests on 20 HRSS-confined fiber-reinforced concrete columns. The effects of stirrup spacing, stirrup strength, and concrete strength on the strength and ductility of the columns were analyzed. The experimental results demonstrate that HRSS can significantly improve the performance of fiber-reinforced concrete. The peak strength of concrete exhibited a maximum increase of 2.033 times, and the ductility ratio achieved a maximum increase of 2.588 times. Furthermore, the application of densely spaced high-strength spiral hoops to confine the core concrete not only effectively enhances its compressive strength but also markedly improves its deformability. Based on the stress distribution across the cross-section of HRSS-confined fiber-reinforced concrete columns, this paper proposes a method for delineating the effective confinement area, establishes calculation models for effective lateral confinement stress, effective confinement coefficient, peak stress, and peak strain, and develops a stress-strain constitutive relationship suitable for HRSS-confined fiber-reinforced concrete columns. Full article
(This article belongs to the Section Building Structures)
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19 pages, 5458 KiB  
Article
Experimental Study on Axial Compression Behavior of Fiber-Reinforced Lightweight Aggregate Concrete Columns Confined by Grid Stirrups
by Shun Chen, Tao Wu, Yujie Huang and Guangyu Sun
Buildings 2025, 15(7), 1206; https://doi.org/10.3390/buildings15071206 - 7 Apr 2025
Viewed by 328
Abstract
In this study, thirteen axial compression tests were conducted on stirrup-confined fiber-reinforced lightweight aggregate concrete (SFLWAC) columns. The effects of stirrup spacing, fiber type, and fiber volume content on the confinement effect of concrete were analyzed. The failure process and failure modes were [...] Read more.
In this study, thirteen axial compression tests were conducted on stirrup-confined fiber-reinforced lightweight aggregate concrete (SFLWAC) columns. The effects of stirrup spacing, fiber type, and fiber volume content on the confinement effect of concrete were analyzed. The failure process and failure modes were investigated. The stress–strain curve of columns and the characteristic points of the curve were examined, and prediction models for peak stress and strain were proposed. The results indicate that increasing the volumetric stirrup ratio effectively enhances the lateral confinement force and increases the area of confined concrete. For specimens with a low volumetric stirrup ratio, the stirrups do not fully utilize their strength when the confined concrete reaches peak strength. The addition of fibers effectively improves the brittleness of lightweight aggregate concrete, with steel fibers providing a more pronounced improvement than carbon fibers. The proposed prediction models can accurately predict the axial compression behavior of SFLWAC. Full article
(This article belongs to the Section Building Structures)
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22 pages, 7497 KiB  
Article
An Experimental Study on the Seismic Performance of New Precast Prestressed Concrete Exterior Joints Based on UHPC Connection
by Xueyu Xiong, Zhisheng Wei, Dawei Zhang, Ju Liu, Yifan Xie and Liang He
Buildings 2025, 15(5), 729; https://doi.org/10.3390/buildings15050729 - 24 Feb 2025
Cited by 4 | Viewed by 768
Abstract
Traditional monolithic precast and precast prestressed concrete joints often face challenges such as complex steel reinforcement details and low construction efficiency. Grouting sleeve connections may also suffer from quality issues. To address these problems, a new precast prestressed concrete frame beam-column exterior joint [...] Read more.
Traditional monolithic precast and precast prestressed concrete joints often face challenges such as complex steel reinforcement details and low construction efficiency. Grouting sleeve connections may also suffer from quality issues. To address these problems, a new precast prestressed concrete frame beam-column exterior joint using ultra-high-performance concrete (UHPC) for connection (PPCFEJ-UHPC) is proposed. This innovative joint lessens the amount of stirrups in the core area, decreases the anchorage length of beam longitudinal reinforcement, and enables efficient lap splicing of column longitudinal reinforcement, thereby enhancing construction convenience. Cyclic loading tests were conducted on three new exterior joint specimens (PE1, PE2, PE3) and one cast-in-place joint specimen (RE1) to evaluate their seismic performance. The study concentrated on failure modes, energy dissipation capacity, displacement ductility, strength and stiffness degradation, shear stress, and deformation’s influence on the longitudinal reinforcement anchoring length and axial compression ratio. The results indicate that the new joint exhibits beam flexural failure with minimal damage to the core area, unlike the cast-in-place joint, which suffers severe core area damage. The novel joint exhibits at least 21.7% and 6.1% improvement in cumulative energy consumption and ductility coefficient, respectively, while matching the cast-in-place joint’s bearing capacity. These characteristics are further improved by 5.5% and 10.7% when the axial compression ratio is increased. The new joints’ seismic performance indices all satisfy the ACI 374.1-05 requirements. Additionally, UHPC significantly improves the anchoring performance of steel bars in the core area, allowing the anchorage length of beam longitudinal bars to be reduced from 16 times of the diameter of reinforcement to 12 times. Full article
(This article belongs to the Special Issue Research on Soil–Structure Interaction for Civil Structures)
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25 pages, 21422 KiB  
Article
Advantages of Using Fibres to Withstand Shear Stress: A Comparative Parametric Study with Conventionally Reinforced Concrete Beams
by Alvaro Picazo, Marcos García Alberti, Alejandro Enfedaque and Jaime C. Gálvez
Materials 2025, 18(4), 801; https://doi.org/10.3390/ma18040801 - 12 Feb 2025
Viewed by 622
Abstract
The structural use of fibre-reinforced concrete (FRC) has shown to be an attractive alternative for certain structural elements, being especially suitable to withstand shear stresses in concrete beams. In the case of longitudinal steel bars to support bending stresses, the reductions are of [...] Read more.
The structural use of fibre-reinforced concrete (FRC) has shown to be an attractive alternative for certain structural elements, being especially suitable to withstand shear stresses in concrete beams. In the case of longitudinal steel bars to support bending stresses, the reductions are of interest. However, in the case of shear stress, it is possible to eliminate the stirrup reinforcement in certain areas. In such a case, the use of FRC may eliminate not only the material but also the tasks of preparing and placing reinforcement, achieving significant savings in labour and allowing a faster execution, avoiding human error, and providing greater security to the work. This study was developed with the aim of assessing a basic practical application of FRC for shear strength. A series of graphics have been made to be used as a calculation tool. The typical structural elements of buildings subjected to bending and shear stress have been tested and analysed. The results for steel fibre-reinforced concrete (SFRC) and polyolefin fibre-reinforced concrete (PFRC) show that fibre can substitute, to some extent, part of the longitudinal reinforcement needed to provide the required flexural strength. Additionally, the fibres can reduce or even eliminate the need for stirrups for shear strength, which leads to savings in cost and execution time. Full article
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21 pages, 7078 KiB  
Article
Study on the Axial Compressive Behavior of Steel Fiber Reinforced Concrete Confined with High-Strength Rectangular Spiral Stirrup
by Huajing Zhao, Weitong Liu, Penghui Yang and Can Song
Materials 2025, 18(3), 669; https://doi.org/10.3390/ma18030669 - 3 Feb 2025
Viewed by 770
Abstract
Monotonic axial compression tests were carried out on 16 steel fiber-reinforced concrete (SFRC) columns confined by rectangular spiral stirrups. The impacts of stirrup spacing, stirrup strength, concrete strength, and cross-sectional aspect ratio on the peak load, ductility, and failure mode of these columns [...] Read more.
Monotonic axial compression tests were carried out on 16 steel fiber-reinforced concrete (SFRC) columns confined by rectangular spiral stirrups. The impacts of stirrup spacing, stirrup strength, concrete strength, and cross-sectional aspect ratio on the peak load, ductility, and failure mode of these columns were analyzed. The test results demonstrate that steel fibers significantly mitigate the spalling of the concrete column’s protective layer through their bridging effect. Small spacing and high-strength spiral stirrups effectively confine the core concrete, enhancing the bearing capacity and ductility of concrete columns. Concrete strength exhibits a positive correlation with the confinement effect. However, as concrete strength increases, the rate of improvement in the confinement effect decreases. At peak compressive stress, the high-strength stirrup may not reach its yield state. Based on the test results, a method for calculating stirrup stress under the peak stress of confined concrete is proposed. A “coupling restraint coefficient” is proposed, and a constitutive model for HRSS confined steel fiber reinforced concrete is developed, considering the coupled effect of effective confinement forces in different directions. Comparative analysis shows that the constitutive model established in this paper agrees well with the experimental results and demonstrates good applicability. Full article
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16 pages, 5877 KiB  
Article
Modification of Uniaxial Stress–Strain Model of Concrete Confined by Pitting Corroded Stirrups
by Zhiwei Miao, Yifan Liu, Kangnuo Chen and Xinping Niu
Materials 2024, 17(23), 6014; https://doi.org/10.3390/ma17236014 - 9 Dec 2024
Viewed by 945
Abstract
To investigate the impact of stirrup pitting corrosion on the stress–strain model of core concrete under compression, this study, based on existing corroded steel specimens, establishes a probabilistic model of the residual cross-sectional area distribution of steel bars to reasonably evaluate the effect [...] Read more.
To investigate the impact of stirrup pitting corrosion on the stress–strain model of core concrete under compression, this study, based on existing corroded steel specimens, establishes a probabilistic model of the residual cross-sectional area distribution of steel bars to reasonably evaluate the effect of pitting on the mechanical performance of stirrups. Considering the tension stiffening effect in reinforced concrete, a time-dependent damage model of corroded steel bars in concrete was determined, and the existing stress–strain model of concrete confined by stirrups was ultimately modified, establishing a time-dependent constitutive model that incorporates the effects of stirrup pitting corrosion. A comparison with previous experimental results indicates that the revised model presented in this paper can appropriately reflect the changes in the mechanical performance of concrete confined by corroded stirrups. The results of this study can provide theoretical support for the refined numerical analysis of reinforced concrete structures under the erosion of chloride ions. Full article
(This article belongs to the Section Construction and Building Materials)
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19 pages, 13623 KiB  
Article
An Innovative Technique for the Strengthening of RC Columns and Their Connections with Beams Using C-FRP ROPES
by Chris Karayannis and Emmanuil Golias
Appl. Sci. 2024, 14(18), 8395; https://doi.org/10.3390/app14188395 - 18 Sep 2024
Cited by 5 | Viewed by 1603
Abstract
The application of the innovative C-FRP ropes for the strengthening of reinforced concrete columns is experimentally examined. Two real-scale specimens with the same geometrical characteristics and the same steel reinforcements were constructed for the needs of this investigation. The primary objective of the [...] Read more.
The application of the innovative C-FRP ropes for the strengthening of reinforced concrete columns is experimentally examined. Two real-scale specimens with the same geometrical characteristics and the same steel reinforcements were constructed for the needs of this investigation. The primary objective of the study is to investigate the efficacy of the use of C-FRP ropes as externally mounted reinforcement for the strengthening of deficient external columns. In this direction, (a) C-FRP ropes are applied as longitudinal reinforcement of the column for the increase in the flexural strength, (b) C-FRP ropes are applied as external confining stirrups in the critical end parts of the column for the improvement of the concrete strength and the development of local element ductility, and finally (c) C-FRP ropes are applied as external stirrups in the form of diagonal X-shaped reinforcement for the increase in the capacity of the part of the column connected with the beam (joint panel). Both specimens are tested under the same cyclic loading procedure that comprises seven steps and each step includes three full loading cycles. The maximum loads of the strengthened specimen at the three loading cycles of the seventh step were 40%, 72% and 87% higher than the corresponding ones of the unstrengthened specimen. On the other hand, the measured shear deformations of the joint panel of the pilot (unstrengthened) specimen at the sixth and the seventh steps were 43% and 44% higher than the corresponding ones of the strengthened specimen. In general, it is concluded that the strengthened column exhibited improved hysteretic response and the whole behavior was apparently improved compared to the pilot specimen without strengthening in terms of maximum loads per loading step, dissipated energy, and shear deformations of the joint panel. In particular, it is stressed that the measured shear deformations of the joint panel and strain gauge measurements have substantiated that the column and the connection panel of the strengthened specimen remain almost intact, whereas damage and eventually failure have been located in the column and the joint panel of the pilot specimen. Additionally, it is emphasized that the C-FRP ropes can easily be applied in structures with complex configuration without any geometrical restraints. Full article
(This article belongs to the Special Issue Advances in Building Materials and Concrete, 2nd Edition)
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22 pages, 6176 KiB  
Article
A Study on the Bearing Performance of an RC Axial Compression Shear Wall Strengthened by a Replacement Method Using Local Reinforcement with an Unsupported Roof
by Yuanwen Liu, Jie Deng, Yigang Jia, Guangyu Wu, Naiwen Ke and Xianglan Wei
Buildings 2024, 14(9), 2926; https://doi.org/10.3390/buildings14092926 - 15 Sep 2024
Viewed by 1014
Abstract
When compared with conventional replacement reinforcement methods, the method of replacement using a local reinforcement with an unsupported roof has the advantages of shortening the reinforcement cycle and reducing material loss, and many scholars have carried out useful explorations thereof. At present, the [...] Read more.
When compared with conventional replacement reinforcement methods, the method of replacement using a local reinforcement with an unsupported roof has the advantages of shortening the reinforcement cycle and reducing material loss, and many scholars have carried out useful explorations thereof. At present, the formula for the bearing capacity of reinforcement by replacing concrete in the Code does not consider the effect of stress hysteresis on the parts of the reinforcement; so when the initial stress level is greater than 0.4, the Code’s strength utilization coefficient of 0.8 for the new concrete in the replaced area is on the side of insecurity. In this study, we are trying to improve and supplement the formula in the Code through the following work. Firstly, 18 groups of shear wall models were constructed using a VFEAP finite element analysis program to analyze the bearing performances of the shear walls after the replacement. The results showed that the replacement concrete strength, the initial stress level and the size of the replaced area had a significant influence on the bearing capacity of the shear wall after the replacement. Secondly, utilizing the replacement concrete strength, the initial stress level and the size of the replacement area as key parameters, then introducing the strength improvement coefficient considering the constraints of the stirrups, the modified strength utilization coefficient of new concrete in the replaced area was formulated. Finally, based on the modified strength utilization coefficient, the replacement bearing capacity formulas for the one-batch, two-batch, and three-batch replacements were derived, and an N-batch replacement bearing capacity formula was regressed and fitted on the basis of these equations, which are less discrete and more secure than the Code’s formula. Full article
(This article belongs to the Special Issue Advanced Studies on Steel Structures)
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18 pages, 15014 KiB  
Article
A Study of the Shear Behavior of Concrete Beams with Synthetic Fibers Reinforced with Glass and Basalt Fiber-Reinforced Polymer Bars
by Isabela Oliveira Duarte, Nadia Cazarim da Silva Forti, Lia Lorena Pimentel and Ana Elisabete Paganelli Guimarães de Avila Jacintho
Buildings 2024, 14(7), 2123; https://doi.org/10.3390/buildings14072123 - 11 Jul 2024
Cited by 3 | Viewed by 1678
Abstract
The use of synthetic materials with high corrosion resistance in a concrete matrix yields structures that are more durable and suitable for use in aggressive environments, eliminating the need for frequent maintenance. Examples of such materials include glass (GFRP) and basalt (BFRP) fiber-reinforced [...] Read more.
The use of synthetic materials with high corrosion resistance in a concrete matrix yields structures that are more durable and suitable for use in aggressive environments, eliminating the need for frequent maintenance. Examples of such materials include glass (GFRP) and basalt (BFRP) fiber-reinforced polymer bars (FRP). Due to the low modulus of elasticity of these bars, concrete elements reinforced with FRP longitudinal rebars tend to exhibit cracks with wider openings and greater depths compared to those reinforced with steel rebars, which diminishes the element’s shear resistance. The addition of discontinuous fibers into the concrete aims to maintain stress transfer across the cracks, thereby enhancing the shear capacity and ductility of FRP-reinforced structures. This study evaluates the impact of fiber addition on the shear resistance of concrete beams reinforced with FRP rebars. An experimental investigation was conducted, focusing on the partial and complete substitution of stirrups with polypropylene macro fibers in concrete beams reinforced with FRP longitudinal rebars and stirrups. This research examined beams reinforced with glass (GFRP) and basalt (BFRP) fiber-reinforced polymer bars. For the initial set of beams, all stirrups were replaced with synthetic macro fibers. In the subsequent set, macro fibers were added to beams with insufficient stirrups. Although the complete replacement of GFRP and BFRP stirrups with polypropylene macro fibers did not alter the brittle shear failure mode, it did enhance the shear resistance capacity by 78.5% for GFRP-reinforced beams and 60.4% for BFRP-reinforced beams. Furthermore, the addition of macro fibers to beams with insufficient stirrups, characterized by excessive spacing, changed the failure mode from brittle shear to pseudo-ductile flexural failure due to concrete crushing. In such instances, the failure load increased by 18.8% for beams with GFRP bars and 22.8% for beams with BFRP bars. Full article
(This article belongs to the Section Building Materials, and Repair & Renovation)
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24 pages, 6939 KiB  
Article
Behavior of Circular Hollow Steel-Reinforced Concrete Columns under Axial Compression
by Qiuyu Wei, Qingxin Ren, Qinghe Wang and Yannian Zhang
Appl. Sci. 2024, 14(11), 4833; https://doi.org/10.3390/app14114833 - 3 Jun 2024
Cited by 1 | Viewed by 2183
Abstract
The circular hollow steel-reinforced concrete (HSRC) column consists of an inner circular hollow steel tube and outer circular hollow reinforced concrete (RC). This design provides several advantages, including being lightweight, having a wide sectional profile, and having a high flexural stiffness. This paper [...] Read more.
The circular hollow steel-reinforced concrete (HSRC) column consists of an inner circular hollow steel tube and outer circular hollow reinforced concrete (RC). This design provides several advantages, including being lightweight, having a wide sectional profile, and having a high flexural stiffness. This paper aims to investigate the behavior of the circular HSRC columns under axial compression through testing and finite element (FE) modeling. An FE model was established to simulate the circular HSRC columns under axial compression, which was validated against the test data. Additionally, the load distribution and the interface stress between the outer hollow RC and inner steel tube were analyzed. Subsequently, a systematic parametric analysis was conducted on the diameter (d) and thickness (t) of the steel tube; slenderness ratio (λ); strength of concrete (fcu); yield strength of steel tube (fsy), longitudinal rebar (fly), and stirrup (fgy); as well as the stirrup spacing (s). The critical influencing factors of the circular HSRC columns under axial compression were identified. fcu, λ, d, fly, and fsy dramatically influence the bearing capacity, and the stiffness is notably affected by λ and fcu. Finally, three simplified design methods were summarized and evaluated for calculating the bearing capacity of the circular HSRC columns under axial compression. Full article
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