S. Hartwig, C. Kang, F. Fürll, F. Klein, M. Classen, S. Marx
Previous models of circular ring segment joints have been inadequate in describing their loading capacity due to the lack of consideration for the interaction between shear force and bending moment. Consequently, these models have led to over‐ or underestimation of the joints' capacity. The increasing use of dry joint connection technology in wind turbine towers and prefabricated segmental bridge constructions necessitates the development of advanced computational models for these connections. This study presents a new model that considers the effects of bending moment, shear force, and torsion on the loading capacity of circular ring segment joints. Numerical simulations were conducted to validate the developed model under different load combinations, and the results demonstrate excellent agreement between the model predictions and numerical simulations.
{"title":"Development of a new analytical model for circular concrete ring segments with dry joints under combined effects","authors":"S. Hartwig, C. Kang, F. Fürll, F. Klein, M. Classen, S. Marx","doi":"10.1002/suco.202400194","DOIUrl":"https://doi.org/10.1002/suco.202400194","url":null,"abstract":"Previous models of circular ring segment joints have been inadequate in describing their loading capacity due to the lack of consideration for the interaction between shear force and bending moment. Consequently, these models have led to over‐ or underestimation of the joints' capacity. The increasing use of dry joint connection technology in wind turbine towers and prefabricated segmental bridge constructions necessitates the development of advanced computational models for these connections. This study presents a new model that considers the effects of bending moment, shear force, and torsion on the loading capacity of circular ring segment joints. Numerical simulations were conducted to validate the developed model under different load combinations, and the results demonstrate excellent agreement between the model predictions and numerical simulations.","PeriodicalId":21988,"journal":{"name":"Structural Concrete","volume":"13 1","pages":""},"PeriodicalIF":3.2,"publicationDate":"2024-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142247404","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Filippo Medeghini, Giuseppe Tiberti, Jajnabalkya Guhathakurta, Sven Simon, Giovanni A. Plizzari, Peter Mark
Fiber orientation is of paramount importance for the design of fiber‐reinforced concrete (FRC) structural elements, because it markedly influences the postcracking properties of such material. For this reason, structural codes introduce orientation factors which aim to correlate the real mechanical properties of the structural element with the ones determined from standard beams. Although the need of considering fiber orientation in design codes is commonly accepted, the orientation factors are still based on a limited number of research studies, raising the need to better determine fiber orientation to improve the current standards and support the design process of FRC elements. In this research, a steel fiber‐reinforced concrete (SFRC) with a hybrid system of macro and microfibers is steered into a broad range of fiber orientations and cast into standard beams. Besides measuring the mechanical performance of these SFRC beams, three different methods for assessing fiber orientation are employed, namely electromagnetic induction, image analysis, and micro‐computed tomography. The comparison between the outcomes of the different methods provides detailed information about the accuracy and suitability of each method, considering the corresponding domain of applicability at structural level. Finally, a critical review of the most common 2D and 3D orientation parameters found in literature is performed, and the equations are adapted to account for the hybrid system of fibers.
{"title":"Fiber orientation and orientation factors in steel fiber‐reinforced concrete beams with hybrid fibers: A critical review","authors":"Filippo Medeghini, Giuseppe Tiberti, Jajnabalkya Guhathakurta, Sven Simon, Giovanni A. Plizzari, Peter Mark","doi":"10.1002/suco.202400461","DOIUrl":"https://doi.org/10.1002/suco.202400461","url":null,"abstract":"Fiber orientation is of paramount importance for the design of fiber‐reinforced concrete (FRC) structural elements, because it markedly influences the postcracking properties of such material. For this reason, structural codes introduce orientation factors which aim to correlate the real mechanical properties of the structural element with the ones determined from standard beams. Although the need of considering fiber orientation in design codes is commonly accepted, the orientation factors are still based on a limited number of research studies, raising the need to better determine fiber orientation to improve the current standards and support the design process of FRC elements. In this research, a steel fiber‐reinforced concrete (SFRC) with a hybrid system of macro and microfibers is steered into a broad range of fiber orientations and cast into standard beams. Besides measuring the mechanical performance of these SFRC beams, three different methods for assessing fiber orientation are employed, namely electromagnetic induction, image analysis, and micro‐computed tomography. The comparison between the outcomes of the different methods provides detailed information about the accuracy and suitability of each method, considering the corresponding domain of applicability at structural level. Finally, a critical review of the most common 2D and 3D orientation parameters found in literature is performed, and the equations are adapted to account for the hybrid system of fibers.","PeriodicalId":21988,"journal":{"name":"Structural Concrete","volume":"39 1","pages":""},"PeriodicalIF":3.2,"publicationDate":"2024-09-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142247409","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Strut‐and‐tie modeling (STM) is commonly employed in the design of multiple pile caps in bridge structures. However, the construction of the model can be complicated by manual and experience‐related challenges. Based on load‐path modeling (LPM), this study presents analytical solutions for solving the elastic stress distribution in multiple‐pile caps with various structural configurations. This is accomplished by employing the transparent LPM approach that combines graphical and analytical features. It is found that the LPM is able to capture the distribution of transverse tensile stresses in the bottom region of multiple‐pile caps. At the same time, direct equations are developed to calculate the resultant transverse tension forces in multiple‐pile caps. The LPM results can be used as a quantitative basis for constructing strut‐and‐tie models. Finally, a worked example is provided to show the efficiency of the proposed LPM.
{"title":"Load‐path analysis of transverse tensile stresses in multiple‐pile caps","authors":"Zhi‐Qi He, Muhammad Sami Ullah, Gao Liu","doi":"10.1002/suco.202400699","DOIUrl":"https://doi.org/10.1002/suco.202400699","url":null,"abstract":"Strut‐and‐tie modeling (STM) is commonly employed in the design of multiple pile caps in bridge structures. However, the construction of the model can be complicated by manual and experience‐related challenges. Based on load‐path modeling (LPM), this study presents analytical solutions for solving the elastic stress distribution in multiple‐pile caps with various structural configurations. This is accomplished by employing the transparent LPM approach that combines graphical and analytical features. It is found that the LPM is able to capture the distribution of transverse tensile stresses in the bottom region of multiple‐pile caps. At the same time, direct equations are developed to calculate the resultant transverse tension forces in multiple‐pile caps. The LPM results can be used as a quantitative basis for constructing strut‐and‐tie models. Finally, a worked example is provided to show the efficiency of the proposed LPM.","PeriodicalId":21988,"journal":{"name":"Structural Concrete","volume":"38 1","pages":""},"PeriodicalIF":3.2,"publicationDate":"2024-09-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142247407","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Developing offshore wind power can effectively reduce carbon emissions, and adopting large‐capacity wind turbines is an important way to achieve cost reduction and efficiency increase. With increasing power capacity, the hub height and rotor‐nacelle assemblies (RNA) load will increase significantly. Ultra‐high performance concrete (UHPC) possesses ultra‐high compressive performance, good tensile, fatigue, and corrosion resistance, and thus is an effective way to further improve the mechanical performance and economic efficiency of tall offshore wind turbine (OWT) towers. Evaluation of ultimate strength is an essential aspect of design for OWT towers, and the tower structure is mainly under the combined action of axial compression from the self‐weight and RNA loads and bending from the eccentricities of RNA and aerodynamic loads from the rotor on the tower top. In this work, the mechanical behavior of prestressed UHPC wind turbine tower columns under combined axial compression and bending was numerically investigated. The finite element (FE) analyses were carried out using ABAQUS, and the material and geometric nonlinearity were considered in the model, as well as the tensile strain hardening properties of UHPC. The FE models were firstly verified by the typical experimental results of UHPC hollow columns, reinforced UHPC beams, prestressed UHPC beams, and prestressed concrete‐steel hybrid wind turbine tower model. Then the parametric study was carried out, and the parameters included the control stress and number of prestressing tendons, rib number, diameter‐to‐thickness ratio of the UHPC column, steel ratio of longitudinal reinforcement, axial load ratio, and UHPC strength. The calculation methods for flexural capacity of prestressed UHPC wind turbine tower columns were finally proposed, and were found to agree well with the modeling results.
{"title":"Mechanical behavior of prestressed UHPC wind turbine tower columns under combined axial compression and bending","authors":"Zheng Zhou, Xuhong Zhou","doi":"10.1002/suco.202400223","DOIUrl":"https://doi.org/10.1002/suco.202400223","url":null,"abstract":"Developing offshore wind power can effectively reduce carbon emissions, and adopting large‐capacity wind turbines is an important way to achieve cost reduction and efficiency increase. With increasing power capacity, the hub height and rotor‐nacelle assemblies (RNA) load will increase significantly. Ultra‐high performance concrete (UHPC) possesses ultra‐high compressive performance, good tensile, fatigue, and corrosion resistance, and thus is an effective way to further improve the mechanical performance and economic efficiency of tall offshore wind turbine (OWT) towers. Evaluation of ultimate strength is an essential aspect of design for OWT towers, and the tower structure is mainly under the combined action of axial compression from the self‐weight and RNA loads and bending from the eccentricities of RNA and aerodynamic loads from the rotor on the tower top. In this work, the mechanical behavior of prestressed UHPC wind turbine tower columns under combined axial compression and bending was numerically investigated. The finite element (FE) analyses were carried out using ABAQUS, and the material and geometric nonlinearity were considered in the model, as well as the tensile strain hardening properties of UHPC. The FE models were firstly verified by the typical experimental results of UHPC hollow columns, reinforced UHPC beams, prestressed UHPC beams, and prestressed concrete‐steel hybrid wind turbine tower model. Then the parametric study was carried out, and the parameters included the control stress and number of prestressing tendons, rib number, diameter‐to‐thickness ratio of the UHPC column, steel ratio of longitudinal reinforcement, axial load ratio, and UHPC strength. The calculation methods for flexural capacity of prestressed UHPC wind turbine tower columns were finally proposed, and were found to agree well with the modeling results.","PeriodicalId":21988,"journal":{"name":"Structural Concrete","volume":"3 1","pages":""},"PeriodicalIF":3.2,"publicationDate":"2024-09-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142203980","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Fully embedded and spatially diffuse sensors are central to the advancement of civil and construction engineering. Indeed, they serve as an enabling technology necessary for addressing the current challenges associated with through‐life management and structural health monitoring of existing structures and infrastructures. The need to identify structural issues early on has driven the integration of such embedded sensing capabilities into construction materials, turning passive structures into proactive, self‐aware “entities,” commonly referred to as Smart Structures. The economic rationale behind this endeavor is underscored by the vital significance of continuous monitoring, which enables prompt anomaly assessment and thus mitigates the risks of potential structural failures. This is particularly relevant for road and rail infrastructures, as they represent a substantial and enduring investment for any nation. Given that a large majority of these large infrastructures are composed of concrete and reinforced concrete, both academics and construction companies are continuously researching micro‐ and nano‐engineered self‐sensing solutions specifically tailored for this building material. This comprehensive review paper reports the latest advances in the field of self‐sensing concrete as of 2024, with an emphasis on intrinsic self‐sensing concrete, that is, electrically conductive functional fillers. A critical analysis and a discussion of the findings are provided. Based on the perceived existing gaps and demands from the industry, the field's future perspectives are also briefly outlined.
{"title":"Recent advances in embedded technologies and self‐sensing concrete for structural health monitoring","authors":"Marco Civera, Ahmad Naseem, Bernardino Chiaia","doi":"10.1002/suco.202400714","DOIUrl":"https://doi.org/10.1002/suco.202400714","url":null,"abstract":"Fully embedded and spatially diffuse sensors are central to the advancement of civil and construction engineering. Indeed, they serve as an enabling technology necessary for addressing the current challenges associated with through‐life management and structural health monitoring of existing structures and infrastructures. The need to identify structural issues early on has driven the integration of such embedded sensing capabilities into construction materials, turning passive structures into proactive, self‐aware “entities,” commonly referred to as Smart Structures. The economic rationale behind this endeavor is underscored by the vital significance of continuous monitoring, which enables prompt anomaly assessment and thus mitigates the risks of potential structural failures. This is particularly relevant for road and rail infrastructures, as they represent a substantial and enduring investment for any nation. Given that a large majority of these large infrastructures are composed of concrete and reinforced concrete, both academics and construction companies are continuously researching micro‐ and nano‐engineered self‐sensing solutions specifically tailored for this building material. This comprehensive review paper reports the latest advances in the field of self‐sensing concrete as of 2024, with an emphasis on intrinsic self‐sensing concrete, that is, electrically conductive functional fillers. A critical analysis and a discussion of the findings are provided. Based on the perceived existing gaps and demands from the industry, the field's future perspectives are also briefly outlined.","PeriodicalId":21988,"journal":{"name":"Structural Concrete","volume":"50 1","pages":""},"PeriodicalIF":3.2,"publicationDate":"2024-09-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142203982","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This research investigated the mechanical property and hydration process of sintered sludge cement (SSC) paste, focusing on the effects of calcination temperature of sludge, sintered sludge ash (SSA) content, curing age, and water‐binder ratio using isothermal calorimetry, X‐ray diffraction, scanning electron microscopy, and multiple regression. Increasing calcination temperature enhanced the compressive strength of SSC paste due to the decomposition of minerals like Clinochlore and Muscovite. The compressive strength decreased by 2.4%–49.4% when the SSA content increased from 0% to 50%, with more significant declines noted at higher water‐binder ratios. Notably, the 7‐day compressive strength of the cement paste with 10% SSA showed little change, and the 28‐day compressive strength actually increased at a water‐binder ratio of 0.4. SSA slowed down the hydration rate of cement and induced more Monocarbonate to form in the early stage. A multiple linear regression model was developed to predict SSC compressive strength with a 12% error margin.
{"title":"Experimental investigation on mechanical property and hydration process of sintered sludge cement paste at different water‐binder ratios and curing ages","authors":"Jinrui Zhang, Chenjiang Li, Tong Lv, Dongshuai Hou, Shuxian Hong, Biqin Dong","doi":"10.1002/suco.202400820","DOIUrl":"https://doi.org/10.1002/suco.202400820","url":null,"abstract":"This research investigated the mechanical property and hydration process of sintered sludge cement (SSC) paste, focusing on the effects of calcination temperature of sludge, sintered sludge ash (SSA) content, curing age, and water‐binder ratio using isothermal calorimetry, X‐ray diffraction, scanning electron microscopy, and multiple regression. Increasing calcination temperature enhanced the compressive strength of SSC paste due to the decomposition of minerals like Clinochlore and Muscovite. The compressive strength decreased by 2.4%–49.4% when the SSA content increased from 0% to 50%, with more significant declines noted at higher water‐binder ratios. Notably, the 7‐day compressive strength of the cement paste with 10% SSA showed little change, and the 28‐day compressive strength actually increased at a water‐binder ratio of 0.4. SSA slowed down the hydration rate of cement and induced more Monocarbonate to form in the early stage. A multiple linear regression model was developed to predict SSC compressive strength with a 12% error margin.","PeriodicalId":21988,"journal":{"name":"Structural Concrete","volume":"15 1","pages":""},"PeriodicalIF":3.2,"publicationDate":"2024-09-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142203981","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Penghui Zhang, Lianxu Zhou, Junjun Guo, Zhiqiang Wang
Drilled shafts with a larger diameter than columns are frequently adopted as the foundation of highway bridge columns due to their superior economic efficiency and lower impact on existing facilities in the urban built‐up area. Different section dimensions lead to a socket connection between the column and the oversized shaft and a noncontact lap splice of their longitudinal bars. The force‐transfer mechanism and failure process of column‐to‐drilled shaft connections were deeply revealed in this study. Detailed FE models were developed at the Diana platform and validated against previous experimental results. Subsequently, a parametric study investigated the effect of the shear span‐to‐depth ratio, diameter ratio of shaft‐to‐column, column embedment depth, and shaft stirrup ratio. Finally, a modified strut‐and‐tie model (STM) was proposed to design stirrups of the transition region efficiently considering the experimental failure mechanism. Results indicate that the numerical models built in the Diana platform can precisely simulate the mechanical behavior of column‐to‐drilled shaft connections. The failure mechanism of column‐to‐drilled shaft connections is shaft stirrups yield at the compressive side induced by extrusion between the embedded column and shaft. The lateral loading capacity of column‐to‐drilled shaft connections increases with the increase of shear span‐to‐depth ratio, diameter ratio of shaft‐to‐column, column embedment depth, and shaft stirrup ratio. The modified STM is able to reveal the variation tendency of shaft transverse reinforcement demand with the various design parameters and give an average stirrup stress ratio of 1.20 and a coefficient of variation of only 8.31%.
{"title":"Strut‐and‐tie model for column‐to‐drilled shaft connections in reinforced concrete bridge columns subjected to lateral loads","authors":"Penghui Zhang, Lianxu Zhou, Junjun Guo, Zhiqiang Wang","doi":"10.1002/suco.202400098","DOIUrl":"https://doi.org/10.1002/suco.202400098","url":null,"abstract":"Drilled shafts with a larger diameter than columns are frequently adopted as the foundation of highway bridge columns due to their superior economic efficiency and lower impact on existing facilities in the urban built‐up area. Different section dimensions lead to a socket connection between the column and the oversized shaft and a noncontact lap splice of their longitudinal bars. The force‐transfer mechanism and failure process of column‐to‐drilled shaft connections were deeply revealed in this study. Detailed FE models were developed at the <jats:italic>Diana</jats:italic> platform and validated against previous experimental results. Subsequently, a parametric study investigated the effect of the shear span‐to‐depth ratio, diameter ratio of shaft‐to‐column, column embedment depth, and shaft stirrup ratio. Finally, a modified strut‐and‐tie model (STM) was proposed to design stirrups of the transition region efficiently considering the experimental failure mechanism. Results indicate that the numerical models built in the <jats:italic>Diana</jats:italic> platform can precisely simulate the mechanical behavior of column‐to‐drilled shaft connections. The failure mechanism of column‐to‐drilled shaft connections is shaft stirrups yield at the compressive side induced by extrusion between the embedded column and shaft. The lateral loading capacity of column‐to‐drilled shaft connections increases with the increase of shear span‐to‐depth ratio, diameter ratio of shaft‐to‐column, column embedment depth, and shaft stirrup ratio. The modified STM is able to reveal the variation tendency of shaft transverse reinforcement demand with the various design parameters and give an average stirrup stress ratio of 1.20 and a coefficient of variation of only 8.31%.","PeriodicalId":21988,"journal":{"name":"Structural Concrete","volume":"18 1","pages":""},"PeriodicalIF":3.2,"publicationDate":"2024-09-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142203983","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Cast‐in‐suit stairs and precast stairs were damaged seriously during many earthquakes in recent years. Stairs with new sliding support were put forward in order to avoid the failure of stairs, landing slab in the half floor was divided into two parts and sliding support was placed between stair beam and landing slab. Down‐scaled model of stairs with new sliding support was produced, and reversed cyclic loading test was conducted to investigate the failure mode, hysteretic behavior, ductility, stiffness degradation and energy dissipation. The failure mode was crushing damage of frame column and stair components remained intact. The new sliding support had good working properties and landing slab separated from stair beam under the pull condition. In addition, seven finite element models of staircase were developed to investigate the seismic performance of staircase, and seven finite element models of frame structure were developed to investigate the effect of stairs on the seismic performance of main structure. Lateral stiffness of the staircase was asymmetrical affected by common stairs, so torsional deformation of staircase was large, and stairs with new sliding support had no effect to the lateral stiffness of staircase. Compared with frame structure, the natural period of vibration decreased approximately by 5% and the first vibration mode also changed direction when common stairs was considered, the natural period of vibration and the first vibration mode were not change when sliding support was adopted. Stairs were not damaged and did not affect the seismic performance of main structure when new sliding support was used.
{"title":"Seismic performance of reinforced concrete stairs with new sliding support","authors":"Zheng Zhang, Shuping Cong, Yangang Zhang, Yongtao Chen","doi":"10.1002/suco.202300907","DOIUrl":"https://doi.org/10.1002/suco.202300907","url":null,"abstract":"Cast‐in‐suit stairs and precast stairs were damaged seriously during many earthquakes in recent years. Stairs with new sliding support were put forward in order to avoid the failure of stairs, landing slab in the half floor was divided into two parts and sliding support was placed between stair beam and landing slab. Down‐scaled model of stairs with new sliding support was produced, and reversed cyclic loading test was conducted to investigate the failure mode, hysteretic behavior, ductility, stiffness degradation and energy dissipation. The failure mode was crushing damage of frame column and stair components remained intact. The new sliding support had good working properties and landing slab separated from stair beam under the pull condition. In addition, seven finite element models of staircase were developed to investigate the seismic performance of staircase, and seven finite element models of frame structure were developed to investigate the effect of stairs on the seismic performance of main structure. Lateral stiffness of the staircase was asymmetrical affected by common stairs, so torsional deformation of staircase was large, and stairs with new sliding support had no effect to the lateral stiffness of staircase. Compared with frame structure, the natural period of vibration decreased approximately by 5% and the first vibration mode also changed direction when common stairs was considered, the natural period of vibration and the first vibration mode were not change when sliding support was adopted. Stairs were not damaged and did not affect the seismic performance of main structure when new sliding support was used.","PeriodicalId":21988,"journal":{"name":"Structural Concrete","volume":"37 1","pages":""},"PeriodicalIF":3.2,"publicationDate":"2024-09-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142203984","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Qichang Fan, Yuanyuan Zheng, Chunhui He, Dan Meng, Qun Guo, Yiming Liu
To explore the influence of the interface properties between fiber/cement matrix on the performance of fiber‐modified cement‐based composite. Polyethylene (PE) and polyvinyl alcohol fiber (PVA) are brought in the cement‐based materials to prepare mortar and Engineered Cementitious Composite (ECC) samples. The mortar's mechanical, and ECC's tensile capacity, four‐point bending and porosity were tested to verify the interface's influence on samples' performance. Furthermore, the water contact angle was used to analyze the wettability of the fiber, and a scanning electron microscope (SEM) was used to observe the fiber/matrix interface on the microscopic scale. Molecular dynamics simulation was performed to calculate the interfacial paraments from an atomic scale. The results shows that fiber increases the toughness of the mortar and improved its flexural strength. Through SEM, it was found that PVA fiber can form tight adsorption with the hydration matrix. While there are many apparent cracks and pores at the PE/matrix interface, the poor bonding destroys the matrix's structure and reduces its compressive strength. By analyzing the performance of ECC samples, it was known that PVA‐ECC's strain rate can reach 5.73%, while PE‐ECC is 4.20%. PE fiber has higher mechanical strength and can bear more loads, it helps PE‐ECC to obtain a greater modulus of rapture. Nuclear magnetic resonance results showed that the porosity of PVA‐ECC is lower than PE‐ECC. The ability of PE‐ECC to resist external interference is weak, and the interface of PE/matrix is easily damaged. Molecule dynamics simulation results indicated the adsorption energy between PVA/CSH is 6.17 times that of PE/CSH. The PVA/C‐S‐H interface tends to form CaO and H‐bonds to strengthen the bonding, the bonding has limited the movement of atoms and making the PVA chains tightly adsorbed on the CSH surface. While the adsorption between PE and CSH is weak, the PE will detach from the CSH surface and form aggregates. Moreover, PVA and water molecules form a stable hydrogen bond network to promote the hydration production grows on the surface of PVA fiber. However, PE fiber is complex enough to adsorb water molecules and hardly encourage the development of pores at the interface. By analyzing the properties of the interface between different fibers and cement matrix can provide insights for strengthening the interface properties of fiber cement matrix, and then improve the properties of fiber cement‐based composites.
{"title":"Effect of interfacial properties between polyethylene and polyvinyl alcohol fiber/cement matrix on properties of mortar and ECC","authors":"Qichang Fan, Yuanyuan Zheng, Chunhui He, Dan Meng, Qun Guo, Yiming Liu","doi":"10.1002/suco.202400607","DOIUrl":"https://doi.org/10.1002/suco.202400607","url":null,"abstract":"To explore the influence of the interface properties between fiber/cement matrix on the performance of fiber‐modified cement‐based composite. Polyethylene (PE) and polyvinyl alcohol fiber (PVA) are brought in the cement‐based materials to prepare mortar and Engineered Cementitious Composite (ECC) samples. The mortar's mechanical, and ECC's tensile capacity, four‐point bending and porosity were tested to verify the interface's influence on samples' performance. Furthermore, the water contact angle was used to analyze the wettability of the fiber, and a scanning electron microscope (SEM) was used to observe the fiber/matrix interface on the microscopic scale. Molecular dynamics simulation was performed to calculate the interfacial paraments from an atomic scale. The results shows that fiber increases the toughness of the mortar and improved its flexural strength. Through SEM, it was found that PVA fiber can form tight adsorption with the hydration matrix. While there are many apparent cracks and pores at the PE/matrix interface, the poor bonding destroys the matrix's structure and reduces its compressive strength. By analyzing the performance of ECC samples, it was known that PVA‐ECC's strain rate can reach 5.73%, while PE‐ECC is 4.20%. PE fiber has higher mechanical strength and can bear more loads, it helps PE‐ECC to obtain a greater modulus of rapture. Nuclear magnetic resonance results showed that the porosity of PVA‐ECC is lower than PE‐ECC. The ability of PE‐ECC to resist external interference is weak, and the interface of PE/matrix is easily damaged. Molecule dynamics simulation results indicated the adsorption energy between PVA/CSH is 6.17 times that of PE/CSH. The PVA/C‐S‐H interface tends to form CaO and H‐bonds to strengthen the bonding, the bonding has limited the movement of atoms and making the PVA chains tightly adsorbed on the CSH surface. While the adsorption between PE and CSH is weak, the PE will detach from the CSH surface and form aggregates. Moreover, PVA and water molecules form a stable hydrogen bond network to promote the hydration production grows on the surface of PVA fiber. However, PE fiber is complex enough to adsorb water molecules and hardly encourage the development of pores at the interface. By analyzing the properties of the interface between different fibers and cement matrix can provide insights for strengthening the interface properties of fiber cement matrix, and then improve the properties of fiber cement‐based composites.","PeriodicalId":21988,"journal":{"name":"Structural Concrete","volume":"17 1","pages":""},"PeriodicalIF":3.2,"publicationDate":"2024-09-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142203986","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This paper presents a numerical and experimental study aimed at the modeling and dynamic characterization of the reinforced concrete structure of the Palazzetto dello Sport in Rome, designed and by Pier Luigi Nervi with Annibale Vitellozzi, and built by Nervi & Bartoli contractors in 1956‐57. An experimental dynamic testing campaign has been performed to obtain the modal properties of the structure, identified using operational modal analysis (OMA). The axial symmetry of the Palazzetto's dome, expected to exist in an idealized perfect dome, has been observed to occur experimentally by noting that rotated modes possessed nearly identical frequencies, evidenced by closely spaced double peaks in the power spectral density. This observation recognizes the remarkable precision of Nervi's construction methodology. A numerical 3D model has been developed by relying on detailed information about the structure gathered from various sources, including archival documents, on‐site testing, and surveying. The model has been calibrated by means of modal updating based on the experimental measurements collected in this study. The reconstruction of the dome using laser‐scanning and aerophotogrammetry has revealed a slight asymmetry in its thickness distribution (and consequently its mass distribution) that, when incorporated in the numerical model, has been shown to contribute to the experimentally observed frequency split. It is expected that, by tracking these closely spaced frequencies on top of the typical variations of natural frequencies in a health monitoring approach, further insight might be gained into the detection of possible damages and/or degradation of the structure and its components.
{"title":"The Pier Luigi Nervi's concrete structure of Palazzetto dello Sport: Modeling and dynamic characterization","authors":"Jacopo Ciambella, Gianluca Ranzi, Francesco Romeo","doi":"10.1002/suco.202400320","DOIUrl":"https://doi.org/10.1002/suco.202400320","url":null,"abstract":"This paper presents a numerical and experimental study aimed at the modeling and dynamic characterization of the reinforced concrete structure of the Palazzetto dello Sport in Rome, designed and by Pier Luigi Nervi with Annibale Vitellozzi, and built by Nervi & Bartoli contractors in 1956‐57. An experimental dynamic testing campaign has been performed to obtain the modal properties of the structure, identified using operational modal analysis (OMA). The axial symmetry of the Palazzetto's dome, expected to exist in an idealized perfect dome, has been observed to occur experimentally by noting that rotated modes possessed nearly identical frequencies, evidenced by closely spaced double peaks in the power spectral density. This observation recognizes the remarkable precision of Nervi's construction methodology. A numerical 3D model has been developed by relying on detailed information about the structure gathered from various sources, including archival documents, on‐site testing, and surveying. The model has been calibrated by means of modal updating based on the experimental measurements collected in this study. The reconstruction of the dome using laser‐scanning and aerophotogrammetry has revealed a slight asymmetry in its thickness distribution (and consequently its mass distribution) that, when incorporated in the numerical model, has been shown to contribute to the experimentally observed frequency split. It is expected that, by tracking these closely spaced frequencies on top of the typical variations of natural frequencies in a health monitoring approach, further insight might be gained into the detection of possible damages and/or degradation of the structure and its components.","PeriodicalId":21988,"journal":{"name":"Structural Concrete","volume":"81 1","pages":""},"PeriodicalIF":3.2,"publicationDate":"2024-09-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142203985","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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