Pub Date : 2025-02-26DOI: 10.1016/j.engstruct.2025.119942
Bedar Rauf Hassan , Ahmed Manguri , Amjad Burhan Hussein , Antonella Corrado , Przha Habib Abdulrahman , Lava Mahdi Mohammed , Shatw Saadun Mahmood , Lazyar Azad Hatim
In response to the growing demand for alternatives to traditional stirrups in construction, discrete fibers have emerged as a promising solution, offering potential time savings during the building process. Among these, the use of recycled plastic fibers has garnered significant attention, addressing both environmental sustainability and material efficiency challenges in the construction industry. This research focuses on incorporating recycled plastic as discrete fibers within concrete beams reinforced with basalt fiber-reinforced polymer (BFRP) bars, with the dual objectives of reducing environmental impact and enhancing construction efficiency. This research investigates the shear behavior and strength of concrete beams reinforced with BFRP bars through both experimental and numerical methods. Three types of discrete fibers (straps, water bottles, and ropes) were examined for their influence on beam performance. The study focuses on two key parameters: the aspect ratio of the fibers and the different materials from which they are made. Seven concrete beams were tested experimentally to assess these effects, and the experimental findings were further validated using finite element analysis FEM by using ABAQUS. The experimental results indicated that recycled plastic fibers did not significantly enhance the shear strength of FRC beams, with the exception of the BFRP-reinforced beam containing 20 mm short water bottle fibers, which showed a 13.97 % improvement in shear strength compared to the control beam. Furthermore, the analytical results aligned well with the experimental findings in terms of failure load, cracking behavior, and deformation behavior, demonstrating strong consistency between the two approaches.
{"title":"Experimental and numerical assessment of recycled plastic fibers on shear strength and behavior of reinforced concrete beams with basalt FRP bars","authors":"Bedar Rauf Hassan , Ahmed Manguri , Amjad Burhan Hussein , Antonella Corrado , Przha Habib Abdulrahman , Lava Mahdi Mohammed , Shatw Saadun Mahmood , Lazyar Azad Hatim","doi":"10.1016/j.engstruct.2025.119942","DOIUrl":"10.1016/j.engstruct.2025.119942","url":null,"abstract":"<div><div>In response to the growing demand for alternatives to traditional stirrups in construction, discrete fibers have emerged as a promising solution, offering potential time savings during the building process. Among these, the use of recycled plastic fibers has garnered significant attention, addressing both environmental sustainability and material efficiency challenges in the construction industry. This research focuses on incorporating recycled plastic as discrete fibers within concrete beams reinforced with basalt fiber-reinforced polymer (BFRP) bars, with the dual objectives of reducing environmental impact and enhancing construction efficiency. This research investigates the shear behavior and strength of concrete beams reinforced with BFRP bars through both experimental and numerical methods. Three types of discrete fibers (straps, water bottles, and ropes) were examined for their influence on beam performance. The study focuses on two key parameters: the aspect ratio of the fibers and the different materials from which they are made. Seven concrete beams were tested experimentally to assess these effects, and the experimental findings were further validated using finite element analysis FEM by using ABAQUS. The experimental results indicated that recycled plastic fibers did not significantly enhance the shear strength of FRC beams, with the exception of the BFRP-reinforced beam containing 20 mm short water bottle fibers, which showed a 13.97 % improvement in shear strength compared to the control beam. Furthermore, the analytical results aligned well with the experimental findings in terms of failure load, cracking behavior, and deformation behavior, demonstrating strong consistency between the two approaches.</div></div>","PeriodicalId":11763,"journal":{"name":"Engineering Structures","volume":"330 ","pages":"Article 119942"},"PeriodicalIF":5.6,"publicationDate":"2025-02-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143487351","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-02-26DOI: 10.1016/j.engstruct.2025.119960
Fangduo Xiao , Shikun Chen , Kehua Chen , Jizhong Wang , Junlong Yang , Dongming Yan
The stainless steel (SS) rebar is attractive for reinforcing seawater sea-sand concrete (SSC) due to its desirable corrosion resistance. This study presents a central pull-out test program involving 44 specimens to explore the bond behavior of SS rebar to SSC. Several test parameters, such as concrete type and strength, bar type, anchorage length, concrete cover, and stirrup ratio, were comprehensively discussed to investigate their effects on failure modes, bond-slip responses, and ultimate bond strength. Experimental results show that concrete cover, anchorage length, and concrete strength all play a significant role in failure modes. The bond strength of SS rebar is enhanced with the increase in compressive strength of SSC. Nevertheless, inferior bond strength is detected for SSC specimens compared to the normal concrete (NC) counterparts with the same pre-designed concrete strength regardless of bar type. The average bond strength tends to increase with a decreasing anchorage length and increasing concrete cover. In addition, the use of stirrups can also enhance the bond strength by at least 19.32 % compared to the unstrengthened specimens. By taking into account the similar confinement effect provided by the concrete cover and internal stirrups, a unified confinement coefficient is adopted in the ultimate bond strength model and the design anchorage length. Finally, the bond interface is assumed to consist of unlimited spring and friction elements, and a new bond-slip model is proposed based on stochastic damage theory. The proposed model can reasonably reveal the randomness and nonlinearity of bond-slip responses, and a good agreement is also detected by comparing the theoretical predictions with test results.
{"title":"Bond behavior of stainless steel (SS) rebar to seawater sea-sand concrete (SSC): Experiments and modeling","authors":"Fangduo Xiao , Shikun Chen , Kehua Chen , Jizhong Wang , Junlong Yang , Dongming Yan","doi":"10.1016/j.engstruct.2025.119960","DOIUrl":"10.1016/j.engstruct.2025.119960","url":null,"abstract":"<div><div>The stainless steel (SS) rebar is attractive for reinforcing seawater sea-sand concrete (SSC) due to its desirable corrosion resistance. This study presents a central pull-out test program involving 44 specimens to explore the bond behavior of SS rebar to SSC. Several test parameters, such as concrete type and strength, bar type, anchorage length, concrete cover, and stirrup ratio, were comprehensively discussed to investigate their effects on failure modes, bond-slip responses, and ultimate bond strength. Experimental results show that concrete cover, anchorage length, and concrete strength all play a significant role in failure modes. The bond strength of SS rebar is enhanced with the increase in compressive strength of SSC. Nevertheless, inferior bond strength is detected for SSC specimens compared to the normal concrete (NC) counterparts with the same pre-designed concrete strength regardless of bar type. The average bond strength tends to increase with a decreasing anchorage length and increasing concrete cover. In addition, the use of stirrups can also enhance the bond strength by at least 19.32 % compared to the unstrengthened specimens. By taking into account the similar confinement effect provided by the concrete cover and internal stirrups, a unified confinement coefficient is adopted in the ultimate bond strength model and the design anchorage length. Finally, the bond interface is assumed to consist of unlimited spring and friction elements, and a new bond-slip model is proposed based on stochastic damage theory. The proposed model can reasonably reveal the randomness and nonlinearity of bond-slip responses, and a good agreement is also detected by comparing the theoretical predictions with test results.</div></div>","PeriodicalId":11763,"journal":{"name":"Engineering Structures","volume":"330 ","pages":"Article 119960"},"PeriodicalIF":5.6,"publicationDate":"2025-02-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143487349","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-02-26DOI: 10.1016/j.engstruct.2025.119881
Guang He , Xudong Shao , Suiwen Wu , Junhui Cao , Wenyong Cai , Xudong Zhao
To break through the three technical bottlenecks of traditional arch bridges, namely, excessive self-weight, high cost and difficult construction, a low-carbon and high-performance steel-ultra high performance concrete (UHPC) composite truss (SUCT) arch bridge was proposed. After the completion of the cyclic construction, the stress superposition effect makes the stress states of the inner and outer arches different. After the completion of the bridge, the SUCT arch has a high compressive stress reserve to make full use of the compressive strength of UHPC. In this paper, the most unfavorable asymmetric loads were applied to the SUCT arch (16 m) after cyclic construction to study its mechanical performance under high compressive stress state. The cracking behavior, failure mode, and deflection and strain responses were mainly discussed. The nominal cracking and crushing stresses were analyzed. The damage evolution law of the SUCT arch and other composite arches was compared, and the corresponding design suggestions were put forward. The results indicate that the SUCT arch exhibits a brittle failure mode of small eccentric compression, with visible cracks (≤0.04 mm) and crushing only occurring at the spring on the loading side. The stress superposition effect causes the inner arch to crack and crush before the outer arch. The bearing capacity of the SUCT arch is controlled by the compressive strength of UHPC, which can give full play to the excellent compressive performance of UHPC. When the maximum crack width is 0.02 mm, the nominal cracking stresses of the inner and outer arches are 3.5 times and 4.9 times of the elastic ultimate strength, respectively, and the nominal crushing stress of the inner arch (178 MPa) is 2.5 times of the design value of the compressive strength, indicating that the SUCT arch has excellent crack resistance and compressive performance. The compressive safety reserve of the SUCT arch is obviously lower than that of crack resistance, which indicates that the design of SUCT arch bridges is mainly controlled by compression. When designing the SUCT arch, the reinforcement ratio of the longitudinal steel bars and the requirement for the tensile strength of UHPC can be appropriately reduced, and the compressive strength can be appropriately improved, especially in the spring area. Furthermore, the sliding connector can be further optimized to reduce the stress superposition effect, so that the stress states of the inner and outer arches tend to be consistent, and the bearing capacity and crack resistance can be further improved. This study can be used to guide the design and application of new arch bridges.
{"title":"Large-scale experimental study on the mechanical behavior of a steel-UHPC composite truss arch under high compressive stress state after cyclic construction","authors":"Guang He , Xudong Shao , Suiwen Wu , Junhui Cao , Wenyong Cai , Xudong Zhao","doi":"10.1016/j.engstruct.2025.119881","DOIUrl":"10.1016/j.engstruct.2025.119881","url":null,"abstract":"<div><div>To break through the three technical bottlenecks of traditional arch bridges, namely, excessive self-weight, high cost and difficult construction, a low-carbon and high-performance steel-ultra high performance concrete (UHPC) composite truss (SUCT) arch bridge was proposed. After the completion of the cyclic construction, the stress superposition effect makes the stress states of the inner and outer arches different. After the completion of the bridge, the SUCT arch has a high compressive stress reserve to make full use of the compressive strength of UHPC. In this paper, the most unfavorable asymmetric loads were applied to the SUCT arch (16 m) after cyclic construction to study its mechanical performance under high compressive stress state. The cracking behavior, failure mode, and deflection and strain responses were mainly discussed. The nominal cracking and crushing stresses were analyzed. The damage evolution law of the SUCT arch and other composite arches was compared, and the corresponding design suggestions were put forward. The results indicate that the SUCT arch exhibits a brittle failure mode of small eccentric compression, with visible cracks (≤0.04 mm) and crushing only occurring at the spring on the loading side. The stress superposition effect causes the inner arch to crack and crush before the outer arch. The bearing capacity of the SUCT arch is controlled by the compressive strength of UHPC, which can give full play to the excellent compressive performance of UHPC. When the maximum crack width is 0.02 mm, the nominal cracking stresses of the inner and outer arches are 3.5 times and 4.9 times of the elastic ultimate strength, respectively, and the nominal crushing stress of the inner arch (178 MPa) is 2.5 times of the design value of the compressive strength, indicating that the SUCT arch has excellent crack resistance and compressive performance. The compressive safety reserve of the SUCT arch is obviously lower than that of crack resistance, which indicates that the design of SUCT arch bridges is mainly controlled by compression. When designing the SUCT arch, the reinforcement ratio of the longitudinal steel bars and the requirement for the tensile strength of UHPC can be appropriately reduced, and the compressive strength can be appropriately improved, especially in the spring area. Furthermore, the sliding connector can be further optimized to reduce the stress superposition effect, so that the stress states of the inner and outer arches tend to be consistent, and the bearing capacity and crack resistance can be further improved. This study can be used to guide the design and application of new arch bridges.</div></div>","PeriodicalId":11763,"journal":{"name":"Engineering Structures","volume":"330 ","pages":"Article 119881"},"PeriodicalIF":5.6,"publicationDate":"2025-02-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143487342","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-02-26DOI: 10.1016/j.engstruct.2025.119961
Allan Joseph Romero , Mohamed A. Moustafa
Ultra-high performance concrete (UHPC) is a rapidly growing solution for complex superstructures, particularly in regions susceptible to high seismic activity. However, implementing UHPC at the full structural components scale is still challenging because of the associated costs and slow development of design guidelines. Few studies in the research community focus on structural seismic applications, and none incorporate sustainable materials like recycled steel fibers, which can significantly lower the UHPC cost. Thus, this study fills a significant knowledge gap and focuses on the dynamic seismic performance of large-scale precast UHPC bridge piers that exclusively use economically scalable UHPC mixtures with recycled steel fibers. With a focus on bridge piers with accelerated bridge construction (ABC) grouted duct connections, three large-scale precast UHPC bridge piers were fabricated at an actual precast facility in California and tested on a shake table under dynamic earthquake excitations. The UHPC bridge piers varied based on the type of UHPC fibers (manufactured versus recycled steel fibers) and the grouting material in the ABC joint (conventional grout versus UHPC). The paper presents new data and knowledge on seismic response and plastic hinge behavior of UHPC from dynamic shake table tests and successfully demonstrates the viability of scalable UHPC with recycled steel fibers for seismic bridges.
{"title":"Shake table tests of economical precast ultra-high performance concrete bridge piers with different fiber types and seismic joint materials","authors":"Allan Joseph Romero , Mohamed A. Moustafa","doi":"10.1016/j.engstruct.2025.119961","DOIUrl":"10.1016/j.engstruct.2025.119961","url":null,"abstract":"<div><div>Ultra-high performance concrete (UHPC) is a rapidly growing solution for complex superstructures, particularly in regions susceptible to high seismic activity. However, implementing UHPC at the full structural components scale is still challenging because of the associated costs and slow development of design guidelines. Few studies in the research community focus on structural seismic applications, and none incorporate sustainable materials like recycled steel fibers, which can significantly lower the UHPC cost. Thus, this study fills a significant knowledge gap and focuses on the dynamic seismic performance of large-scale precast UHPC bridge piers that exclusively use economically scalable UHPC mixtures with recycled steel fibers. With a focus on bridge piers with accelerated bridge construction (ABC) grouted duct connections, three large-scale precast UHPC bridge piers were fabricated at an actual precast facility in California and tested on a shake table under dynamic earthquake excitations. The UHPC bridge piers varied based on the type of UHPC fibers (manufactured versus recycled steel fibers) and the grouting material in the ABC joint (conventional grout versus UHPC). The paper presents new data and knowledge on seismic response and plastic hinge behavior of UHPC from dynamic shake table tests and successfully demonstrates the viability of scalable UHPC with recycled steel fibers for seismic bridges.</div></div>","PeriodicalId":11763,"journal":{"name":"Engineering Structures","volume":"330 ","pages":"Article 119961"},"PeriodicalIF":5.6,"publicationDate":"2025-02-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143487350","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-02-26DOI: 10.1016/j.engstruct.2025.119953
Lei Tang , Xu-Qiang Shang , Yang-Zhu Zhang , Tian-Li Huang , Ning-Bo Wang , Wei-Xin Ren
The dynamic responses of bridges under operational traffic loads exhibit time-varying characteristics, and accurately identifying the time-varying characteristics is crucial for the health monitoring of bridges. In this study, a generalized S-local maximum reassignment transform (GS-LMRT) is proposed for identifying the time-varying frequencies of bridges under a moving vehicle and for detecting the damage in bridges. First, the parameter optimization algorithm using the energy concentration measure is adopted to determine the optimal window parameters for the generalized S transform (GST). Then, by introducing the frequency-reassignment operator from the local maximum synchrosqueezing transform (LMSST) to the absolute value of GST, the GS-LMRT can be obtained. GS-LMRT can improve the energy concentration of the GST and overcome the issue of fixed window width in LMSST. Finally, to assess the damage of bridges, a damage index (DI) is calculated using the IFs obtained from intact bridges and damaged bridges under a moving vehicle through the proposed GS-LMRT method. Numerical investigations are conducted to study the effect of vehicle mass, vehicle speed, measurement noise, and road surface roughness. Laboratory experiments of a damaged beam with a moving vehicle are designed to validate the proposed method. Numerical simulation and experimental results illustrate that the proposed GS-LMRT method can be used for instantaneous frequency identification and damage detection of bridges under a moving vehicle.
{"title":"Damage detection for bridges under a moving vehicle based on generalized S - local maximum reassignment transform","authors":"Lei Tang , Xu-Qiang Shang , Yang-Zhu Zhang , Tian-Li Huang , Ning-Bo Wang , Wei-Xin Ren","doi":"10.1016/j.engstruct.2025.119953","DOIUrl":"10.1016/j.engstruct.2025.119953","url":null,"abstract":"<div><div>The dynamic responses of bridges under operational traffic loads exhibit time-varying characteristics, and accurately identifying the time-varying characteristics is crucial for the health monitoring of bridges. In this study, a generalized S-local maximum reassignment transform (GS-LMRT) is proposed for identifying the time-varying frequencies of bridges under a moving vehicle and for detecting the damage in bridges. First, the parameter optimization algorithm using the energy concentration measure is adopted to determine the optimal window parameters for the generalized S transform (GST). Then, by introducing the frequency-reassignment operator from the local maximum synchrosqueezing transform (LMSST) to the absolute value of GST, the GS-LMRT can be obtained. GS-LMRT can improve the energy concentration of the GST and overcome the issue of fixed window width in LMSST. Finally, to assess the damage of bridges, a damage index (DI) is calculated using the IFs obtained from intact bridges and damaged bridges under a moving vehicle through the proposed GS-LMRT method. Numerical investigations are conducted to study the effect of vehicle mass, vehicle speed, measurement noise, and road surface roughness. Laboratory experiments of a damaged beam with a moving vehicle are designed to validate the proposed method. Numerical simulation and experimental results illustrate that the proposed GS-LMRT method can be used for instantaneous frequency identification and damage detection of bridges under a moving vehicle.</div></div>","PeriodicalId":11763,"journal":{"name":"Engineering Structures","volume":"330 ","pages":"Article 119953"},"PeriodicalIF":5.6,"publicationDate":"2025-02-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143487341","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
To evaluate the structural safety against waterborne debris impacts, the impact loads are usually computed with analytical models such as those proposed by ASCE/SEI 7–22. These models often assume a massless structure to simplify the analytical formulations, which can be an oversimplifying and inaccurate assumption in cases where the structure is heavier and more flexible than the debris. To address this problem, we aim to define the domain in which the existing models are inaccurate and to propose a new analytical model to accurately compute the debris impact forces through comprehensive finite element simulations and analytical modelling. We defined such a domain in the design space of structure-to-debris mass and stiffness ratios and assessed which are the most accurate analytical models to compute debris impact forces across this space. Our proposed model significantly improves upon the overestimating results of the ASCE/SEI 7–22 model when both stiffness and mass are important in determining the impact forces.
{"title":"Waterborne debris impact forces on wall structures: Elastic analytical model integrating the effects of the structural mass","authors":"Alessandro De Iasio , Bahman Ghiassi , Riccardo Briganti , Gabriele Milani","doi":"10.1016/j.engstruct.2025.119928","DOIUrl":"10.1016/j.engstruct.2025.119928","url":null,"abstract":"<div><div>To evaluate the structural safety against waterborne debris impacts, the impact loads are usually computed with analytical models such as those proposed by ASCE/SEI 7–22. These models often assume a massless structure to simplify the analytical formulations, which can be an oversimplifying and inaccurate assumption in cases where the structure is heavier and more flexible than the debris. To address this problem, we aim to define the domain in which the existing models are inaccurate and to propose a new analytical model to accurately compute the debris impact forces through comprehensive finite element simulations and analytical modelling. We defined such a domain in the design space of structure-to-debris mass and stiffness ratios and assessed which are the most accurate analytical models to compute debris impact forces across this space. Our proposed model significantly improves upon the overestimating results of the ASCE/SEI 7–22 model when both stiffness and mass are important in determining the impact forces.</div></div>","PeriodicalId":11763,"journal":{"name":"Engineering Structures","volume":"330 ","pages":"Article 119928"},"PeriodicalIF":5.6,"publicationDate":"2025-02-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143480402","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-02-24DOI: 10.1016/j.engstruct.2025.119946
Kai Yan , Xi Yu , Pengfei Ren , Ruixin Zhang , Erwin Oh , Yupeng Zhang , Xin Zhang
The fire safety of CFRP-strengthened concrete structures has raised much concern due to the sensitivity of epoxy-based bonding agents to high temperature and failure of strengthening system. Hence, replacing traditional epoxy adhesives with the inorganic adhesives with better high-temperature resistance provides a chance to improve the safety of the strengthened concrete structures under fire. At present, there are few studies concerning the fire behavior of the concrete beams strengthened with the CFRP sheets using magnesium phosphate inorganic adhesive (MPIA) as adhesive agent, and the failure mechanism of the CFRP-MPIA strengthening system under fire is unknown. To fill this gap, eleven specimens were designed and fabricated in this study, and the standard fire tests under constant load were carried out. During tests, the fire responses of the specimens, including the temperature and mid-span deflection developments, the failure time of strengthening system, fire resistance, and failure mode were measured and analyzed. Also, the effect of load level, adhesive type and fire insulation on the fire resistance of the strengthened concrete beams was investigated. The results showed that the MPIA, served as bonding agent, possesses excellent high-temperature resistance, and the “binder-CFRP sheet-binder” sandwich design can thus play a role of thermal insulation for CFRP sheets, which postpones the failure time of CFRP-MPIA strengthening system effectively, and the excellent mechanical properties of the CFRP sheets under anoxic conditions can also be fully utilized. These make the fire resistance of the CFRP-MPIA strengthened concrete beams without fire insulation are slightly higher than those of the CFRP-epoxy strengthened beams with a fire insulation of 20 mm, achieving the integrated design goal of strengthening and fire resistance. Additionally, with the combined use of the fire insulation and the “binder-CFRP sheet-binder” sandwich strengthening system, the fire resistance of the CFRP-MPIA strengthened concrete beams are over 50 % higher than those of the CFRP-epoxy strengthened concrete beams.
{"title":"Experimental research on fire resistance of the concrete beams strengthened with the CFRP sheets pasted by magnesium phosphate inorganic adhesive","authors":"Kai Yan , Xi Yu , Pengfei Ren , Ruixin Zhang , Erwin Oh , Yupeng Zhang , Xin Zhang","doi":"10.1016/j.engstruct.2025.119946","DOIUrl":"10.1016/j.engstruct.2025.119946","url":null,"abstract":"<div><div>The fire safety of CFRP-strengthened concrete structures has raised much concern due to the sensitivity of epoxy-based bonding agents to high temperature and failure of strengthening system. Hence, replacing traditional epoxy adhesives with the inorganic adhesives with better high-temperature resistance provides a chance to improve the safety of the strengthened concrete structures under fire. At present, there are few studies concerning the fire behavior of the concrete beams strengthened with the CFRP sheets using magnesium phosphate inorganic adhesive (MPIA) as adhesive agent, and the failure mechanism of the CFRP-MPIA strengthening system under fire is unknown. To fill this gap, eleven specimens were designed and fabricated in this study, and the standard fire tests under constant load were carried out. During tests, the fire responses of the specimens, including the temperature and mid-span deflection developments, the failure time of strengthening system, fire resistance, and failure mode were measured and analyzed. Also, the effect of load level, adhesive type and fire insulation on the fire resistance of the strengthened concrete beams was investigated. The results showed that the MPIA, served as bonding agent, possesses excellent high-temperature resistance, and the “binder-CFRP sheet-binder” sandwich design can thus play a role of thermal insulation for CFRP sheets, which postpones the failure time of CFRP-MPIA strengthening system effectively, and the excellent mechanical properties of the CFRP sheets under anoxic conditions can also be fully utilized. These make the fire resistance of the CFRP-MPIA strengthened concrete beams without fire insulation are slightly higher than those of the CFRP-epoxy strengthened beams with a fire insulation of 20 mm, achieving the integrated design goal of strengthening and fire resistance. Additionally, with the combined use of the fire insulation and the “binder-CFRP sheet-binder” sandwich strengthening system, the fire resistance of the CFRP-MPIA strengthened concrete beams are over 50 % higher than those of the CFRP-epoxy strengthened concrete beams.</div></div>","PeriodicalId":11763,"journal":{"name":"Engineering Structures","volume":"330 ","pages":"Article 119946"},"PeriodicalIF":5.6,"publicationDate":"2025-02-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143474191","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The quest for sustainable concrete production emphasizes human health and environmental safety while significantly reducing CO2 emissions associated with traditional cement manufacturing, which is vital in combating climate change. Moreover, the novel application of by-products with pozzolanic properties not only diminishes environmental waste but also enhances the performance of concrete constructions. This research studies the sustainable application of crumb rubber (CR) and rice husk ash (RHA) in reinforced concrete (RC) beams. The research proposes a sustainable approach to mitigate the decreased flexural capacity in rubberized RC beams by incorporating rice husk ash (RHA) as a substitute for cement. Nine different concrete mixtures were designed with varying substitution ratios of RHA and CR as partial replacements for cement and fine aggregate (FA), respectively. The substitution ratios considered were 0 %, 10 %, or 20 % for RHA and 0 %, 5 %, or 10 % for CR by FA. Nine simply supported RC beams were cast and tested. The findings demonstrated that substituting cement with RHA at an ideal replacement ratio of 10 % enhanced the concrete strength, whereas the use of CR had a detrimental impact. The flexural capacity, stiffness, and toughness of the examined beams improved with the inclusion of RHA up to 10 %; they then declined with the inclusion of 20 % RHA but continued to be higher than those of the control specimen. The exploration of concrete mixture substitution ratios highlights a compelling balance between performance and sustainability. According to the experimental results, the best substitution ratio for the concrete mixture is a combination of 10 % RHA and 10 % CR, which only slightly reduces the ultimate load by 3.1 %. Finally, the experimental outcomes were compared with the predicted results of ACI 318–19 approaches.
{"title":"Enhancing flexural performance of rubberized concrete beams through incorporation of rice husk ash as cement replacement","authors":"Noha Hussein , Mohamed Abou Elmaaty , Mansour Alturki , Mahmoud Elsayed","doi":"10.1016/j.engstruct.2025.119958","DOIUrl":"10.1016/j.engstruct.2025.119958","url":null,"abstract":"<div><div>The quest for sustainable concrete production emphasizes human health and environmental safety while significantly reducing CO<sub>2</sub> emissions associated with traditional cement manufacturing, which is vital in combating climate change. Moreover, the novel application of by-products with pozzolanic properties not only diminishes environmental waste but also enhances the performance of concrete constructions. This research studies the sustainable application of crumb rubber (CR) and rice husk ash (RHA) in reinforced concrete (RC) beams. The research proposes a sustainable approach to mitigate the decreased flexural capacity in rubberized RC beams by incorporating rice husk ash (RHA) as a substitute for cement. Nine different concrete mixtures were designed with varying substitution ratios of RHA and CR as partial replacements for cement and fine aggregate (FA), respectively. The substitution ratios considered were 0 %, 10 %, or 20 % for RHA and 0 %, 5 %, or 10 % for CR by FA. Nine simply supported RC beams were cast and tested. The findings demonstrated that substituting cement with RHA at an ideal replacement ratio of 10 % enhanced the concrete strength, whereas the use of CR had a detrimental impact. The flexural capacity, stiffness, and toughness of the examined beams improved with the inclusion of RHA up to 10 %; they then declined with the inclusion of 20 % RHA but continued to be higher than those of the control specimen. The exploration of concrete mixture substitution ratios highlights a compelling balance between performance and sustainability. According to the experimental results, the best substitution ratio for the concrete mixture is a combination of 10 % RHA and 10 % CR, which only slightly reduces the ultimate load by 3.1 %. Finally, the experimental outcomes were compared with the predicted results of ACI 318–19 approaches.</div></div>","PeriodicalId":11763,"journal":{"name":"Engineering Structures","volume":"330 ","pages":"Article 119958"},"PeriodicalIF":5.6,"publicationDate":"2025-02-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143474192","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-02-24DOI: 10.1016/j.engstruct.2025.119951
Taraka M.R. Balla , Rahul Reddy Morthala , S. Suriya Prakash
Engineers constantly look for reliable and long-lasting strengthening solutions for deteriorated bridges and building systems. Ultrahigh-performance concrete (UHPC) overlays can be an effective solution for repairing and strengthening bridge decks, beams and slabs in buildings to increase durability and structural performance. This study explores the effectiveness of an innovative hybrid strengthening technique for flexural members using UHPC overlay and external bonding of carbon fibre-reinforced polymer (CFRP) composites. UHPC has a dense material composition that results in high strength, stiffness, and durability. The flexural behaviour of reinforced concrete (RC) beams strengthened with various hybrid configurations of UHPC overlay, and CFRP strengthening is experimentally assessed in this study. Five full-scale specimens with different strengthening configurations are tested under four-point loading. Test results show a maximum increase in flexural capacity of 63 % with only UHPC overlay and 129 % with the hybrid configuration compared to the control RC beam. In addition, the digital image correlation (DIC) results revealed an improved serviceability performance in terms of lesser deflections and reduced crack widths due to UHPC overlay and FRP strengthening. The moment-curvature and load-displacement response from the test results are compared with predictions of the analytical approach generated from the cross-section and member-level analysis. The cracking moment and ultimate strength of all the tested beams are predicted using the proposed analytical approach. Predictions had a coefficient of variation (COV) of 0.05 and 0.04, respectively, with test results.
{"title":"Enhancing flexural performance of reinforced concrete beams using UHPC overlay and external bonding of CFRP composites","authors":"Taraka M.R. Balla , Rahul Reddy Morthala , S. Suriya Prakash","doi":"10.1016/j.engstruct.2025.119951","DOIUrl":"10.1016/j.engstruct.2025.119951","url":null,"abstract":"<div><div>Engineers constantly look for reliable and long-lasting strengthening solutions for deteriorated bridges and building systems. Ultrahigh-performance concrete (UHPC) overlays can be an effective solution for repairing and strengthening bridge decks, beams and slabs in buildings to increase durability and structural performance. This study explores the effectiveness of an innovative hybrid strengthening technique for flexural members using UHPC overlay and external bonding of carbon fibre-reinforced polymer (CFRP) composites. UHPC has a dense material composition that results in high strength, stiffness, and durability. The flexural behaviour of reinforced concrete (RC) beams strengthened with various hybrid configurations of UHPC overlay, and CFRP strengthening is experimentally assessed in this study. Five full-scale specimens with different strengthening configurations are tested under four-point loading. Test results show a maximum increase in flexural capacity of 63 % with only UHPC overlay and 129 % with the hybrid configuration compared to the control RC beam. In addition, the digital image correlation (DIC) results revealed an improved serviceability performance in terms of lesser deflections and reduced crack widths due to UHPC overlay and FRP strengthening. The moment-curvature and load-displacement response from the test results are compared with predictions of the analytical approach generated from the cross-section and member-level analysis. The cracking moment and ultimate strength of all the tested beams are predicted using the proposed analytical approach. Predictions had a coefficient of variation (COV) of 0.05 and 0.04, respectively, with test results.</div></div>","PeriodicalId":11763,"journal":{"name":"Engineering Structures","volume":"330 ","pages":"Article 119951"},"PeriodicalIF":5.6,"publicationDate":"2025-02-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143480430","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-02-24DOI: 10.1016/j.engstruct.2025.119963
Ernesto Hernández , Alessandro Palermo , Gabriele Chiaro , Allan Scott
The influence of rubber aggregate stiffness on the cyclic performance of concrete columns exhibiting flexure-shear interaction remains unclear. It is also uncertain whether existing design provisions can be applied effectively to rubberized concrete columns with these properties. This study examines the cyclic behavior of six circular columns designed for flexure-shear interaction at two ductility levels: limited (LD, ) and moderate (MD, ). The 500 mm diameter columns had an aspect ratio of 2.5 and a constant axial load ratio of . Columns with rubber contents by total aggregate volume of 10 % (R10), and 20 % (R20) were tested, along with a conventional concrete mix (CM2) of comparable compressive strength to R10 mix. R10 columns exhibited minor delays in concrete crushing and rebar buckling, with ductility increases of 10 % (LD) and 3 % (MD) and shear strength variations of less than 1 % compared to CM2. However, increasing rubber content to 20 % led to performance declines, with R20 columns showing shear strength reductions of 21 % (LD) and 14 % (MD) relative to their R10 counterparts. Assessment of design provisions for circular columns indicated that, for rubber contents up to 20 % and axial load ratios up to 10 %, shear strength and stiffness of rubberized concrete columns can be conservatively predicted by solely accounting for the change in compressive strength.
{"title":"Cyclic behavior of reinforced rubberized concrete columns under flexure-shear interaction","authors":"Ernesto Hernández , Alessandro Palermo , Gabriele Chiaro , Allan Scott","doi":"10.1016/j.engstruct.2025.119963","DOIUrl":"10.1016/j.engstruct.2025.119963","url":null,"abstract":"<div><div>The influence of rubber aggregate stiffness on the cyclic performance of concrete columns exhibiting flexure-shear interaction remains unclear. It is also uncertain whether existing design provisions can be applied effectively to rubberized concrete columns with these properties. This study examines the cyclic behavior of six circular columns designed for flexure-shear interaction at two ductility levels: limited (LD, <span><math><mrow><mi>μ</mi><mo>≤</mo><mn>2</mn></mrow></math></span>) and moderate (MD, <span><math><mrow><mn>2</mn><mo><</mo><mi>μ</mi><mo>≤</mo><mn>4</mn></mrow></math></span>). The 500 mm diameter columns had an aspect ratio of 2.5 and a constant axial load ratio of <span><math><mrow><mn>0.10</mn><msubsup><mrow><mtext>f</mtext></mrow><mrow><mtext>c</mtext></mrow><mrow><mo>′</mo></mrow></msubsup><msub><mrow><mtext>A</mtext></mrow><mrow><mtext>g</mtext></mrow></msub></mrow></math></span>. Columns with rubber contents by total aggregate volume of 10 % (R10), and 20 % (R20) were tested, along with a conventional concrete mix (CM2) of comparable compressive strength to R10 mix. R10 columns exhibited minor delays in concrete crushing and rebar buckling, with ductility increases of 10 % (LD) and 3 % (MD) and shear strength variations of less than 1 % compared to CM2. However, increasing rubber content to 20 % led to performance declines, with R20 columns showing shear strength reductions of 21 % (LD) and 14 % (MD) relative to their R10 counterparts. Assessment of design provisions for circular columns indicated that, for rubber contents up to 20 % and axial load ratios up to 10 %, shear strength and stiffness of rubberized concrete columns can be conservatively predicted by solely accounting for the change in compressive strength.</div></div>","PeriodicalId":11763,"journal":{"name":"Engineering Structures","volume":"330 ","pages":"Article 119963"},"PeriodicalIF":5.6,"publicationDate":"2025-02-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143480403","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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