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":null,"pages":null},"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":null,"pages":null},"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":null,"pages":null},"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":null,"pages":null},"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":null,"pages":null},"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":null,"pages":null},"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":null,"pages":null},"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}
This study experimentally and numerically examines the performance of low‐strength reinforced concrete (LS RC) columns confined with external post‐tensioned metal straps (PTMS). Twelve square columns of cross‐section 125 × 125 mm and height 1500 mm were subjected to axial load, with eight columns being eccentrically loaded. Four columns were control specimens without confinement, and another eight were confined using a novel technique that provides active confinement through the PTMS. The main parameters investigated included the PTMS confinement ratio (ρv = 0.64% and 1.28%) and different eccentricities (e/b = 0, 0.25, 0.5 or 1.0, where e = eccentricity). The results show that the capacity and axial displacement of the PTMS‐confined columns increased by up to 43% and 116% over unconfined control columns. Finite element analyses of the columns were carried out in Abaqus® to provide further insight into the behavior of PTMS‐confined columns. This study contributes towards developing cost‐effective confinement solutions for LS RC columns, thus encouraging the broader adoption of active confinement techniques in practical strengthening applications.
{"title":"Performance of eccentrically loaded low‐strength RC columns confined with posttensioned metal straps: An experimental and numerical investigation","authors":"Ram Prasad Neupane, Thanongsak Imjai, Reyes Garcia, Yie Sue Chua, Sandeep Chaudhary","doi":"10.1002/suco.202301026","DOIUrl":"https://doi.org/10.1002/suco.202301026","url":null,"abstract":"This study experimentally and numerically examines the performance of low‐strength reinforced concrete (LS RC) columns confined with external post‐tensioned metal straps (PTMS). Twelve square columns of cross‐section 125 × 125 mm and height 1500 mm were subjected to axial load, with eight columns being eccentrically loaded. Four columns were control specimens without confinement, and another eight were confined using a novel technique that provides active confinement through the PTMS. The main parameters investigated included the PTMS confinement ratio (<jats:italic>ρ</jats:italic><jats:sub><jats:italic>v</jats:italic></jats:sub> = 0.64% and 1.28%) and different eccentricities (<jats:italic>e</jats:italic><jats:italic>/b</jats:italic> = 0, 0.25, 0.5 or 1.0, where <jats:italic>e</jats:italic> = eccentricity). The results show that the capacity and axial displacement of the PTMS‐confined columns increased by up to 43% and 116% over unconfined control columns. Finite element analyses of the columns were carried out in Abaqus® to provide further insight into the behavior of PTMS‐confined columns. This study contributes towards developing cost‐effective confinement solutions for LS RC columns, thus encouraging the broader adoption of active confinement techniques in practical strengthening applications.","PeriodicalId":21988,"journal":{"name":"Structural Concrete","volume":null,"pages":null},"PeriodicalIF":3.2,"publicationDate":"2024-09-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142203987","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}
The immediate functionality of bridges following severe earthquakes is vital for uninterrupted rescue operations. Regarding the significance of resiliency in bridges, post‐tensioned (PT) rocking piers with low residual displacements and minimal damages have developed over the past few decades. The rocking mechanism at two ends of the pier avoids bending moments and excessive flexural damage. The self‐centering (SC) capacity in this system is provided through post‐tensioning forces. Concerning optimum seismic design and retrofit purposes, it is essential to predict the actual degree of seismic damage and SC capacity of PT rocking systems after seismic hazards. In this case, a self‐centering index (SI) is proposed to evaluate the SC capacity when piers are subjected to cyclic and seismic loadings. This SI, when used in co‐operation with a viable damage prediction model, predicts whether or not the piers remain reparable under cyclic or seismic loading scenarios. After comparing a number of energy‐based damage indices, all of which consider the cumulative hysteresis energy, with the input energy‐based damage index (IEB‐DI), the latter was calibrated against observed damages under cyclic loading tests. This DI was chosen as the most suitable damage prediction model and was considered to be simply applicable after time history analysis. In this study, the seismic performance of a seismic‐resistant dual system, consisting of three RC bents along with an SC bent, was evaluated using the aforementioned damage limit states and the introduced SI. The damage predictions of the monolithic bridge, as the reference model, were compared with the estimated damage to the dual bridge. The results show that the joint application of the IEB‐DI and the proposed SI in predicting the performance level of SC rocking piers results in a comprehensive damage prediction model.
严重地震发生后，桥梁能否立即发挥作用对于不间断的救援行动至关重要。关于桥梁韧性的重要性，在过去几十年中，已经开发出了残余位移小、损坏程度小的后张法（PT）摇动桥墩。桥墩两端的摇晃机制可避免弯矩和过度的挠曲破坏。这种系统的自定心（SC）能力是通过后张力提供的。为了达到最佳抗震设计和改造目的，必须预测 PT 摇摆系统在地震灾害后的实际震损程度和自定心能力。在这种情况下，我们提出了一种自定心指数（SI），用于评估桥墩在承受循环荷载和地震荷载时的自定心能力。该 SI 与可行的损坏预测模型配合使用时，可预测桥墩在循环或地震荷载情况下是否仍可修复。基于输入能量的损伤指数（IEB-DI）考虑了累积滞后能量，在比较了许多基于能量的损伤指数后，根据循环加载试验下观察到的损伤情况对 IEB-DI 进行了校准。该损毁指数被选为最合适的损毁预测模型，并被认为可在时间历程分析后简单应用。在本研究中，使用上述破坏极限状态和引入的 SI 评估了抗震双系统的抗震性能，该系统由三个 RC 弯道和一个 SC 弯道组成。将作为参考模型的整体桥梁的破坏预测与双桥的估计破坏进行了比较。结果表明，联合应用 IEB-DI 和拟议的 SI 预测 SC 摇动桥墩的性能水平，可以得到一个全面的损坏预测模型。
{"title":"Damage assessment of self‐centering rocking piers using an input energy‐based damage prediction model coupled with self‐centering index","authors":"Rezvan Ashouri, Mahmoud R. Shiravand","doi":"10.1002/suco.202301146","DOIUrl":"https://doi.org/10.1002/suco.202301146","url":null,"abstract":"The immediate functionality of bridges following severe earthquakes is vital for uninterrupted rescue operations. Regarding the significance of resiliency in bridges, post‐tensioned (PT) rocking piers with low residual displacements and minimal damages have developed over the past few decades. The rocking mechanism at two ends of the pier avoids bending moments and excessive flexural damage. The self‐centering (SC) capacity in this system is provided through post‐tensioning forces. Concerning optimum seismic design and retrofit purposes, it is essential to predict the actual degree of seismic damage and SC capacity of PT rocking systems after seismic hazards. In this case, a self‐centering index (SI) is proposed to evaluate the SC capacity when piers are subjected to cyclic and seismic loadings. This SI, when used in co‐operation with a viable damage prediction model, predicts whether or not the piers remain reparable under cyclic or seismic loading scenarios. After comparing a number of energy‐based damage indices, all of which consider the cumulative hysteresis energy, with the input energy‐based damage index (IEB‐DI), the latter was calibrated against observed damages under cyclic loading tests. This DI was chosen as the most suitable damage prediction model and was considered to be simply applicable after time history analysis. In this study, the seismic performance of a seismic‐resistant dual system, consisting of three RC bents along with an SC bent, was evaluated using the aforementioned damage limit states and the introduced SI. The damage predictions of the monolithic bridge, as the reference model, were compared with the estimated damage to the dual bridge. The results show that the joint application of the IEB‐DI and the proposed SI in predicting the performance level of SC rocking piers results in a comprehensive damage prediction model.","PeriodicalId":21988,"journal":{"name":"Structural Concrete","volume":null,"pages":null},"PeriodicalIF":3.2,"publicationDate":"2024-09-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142226095","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}
Recycled aggregate concrete (RAC) is a multi‐phase material, and it is meaningful to investigate the effect of the properties of each phase. However, a comprehensive parametric analysis of these properties is still lacking, which limits a full understanding of the behavior of RAC. This paper uses numerical mesoscale models and contributes to knowledge on this topic. It focuses on the effects of the quality and shape of aggregate since they are relevant to the behavior of concrete but have scarcely been studied for RAC. Their effects on the mechanical response and fracture behavior of RAC were analyzed based on a validated two‐dimensional numerical model. In addition, this paper also justified the choice of the range of the parameters as well as benchmarked the numerical results with the state‐of‐the‐art. The main findings of the paper are: (1) stiffer aggregates decrease the tensile (by up to 29%) and compressive strength of RAC (by up to 7%); (2) aggregate shape moderately influences these properties by up to 10% and 8%; (3) the modulus of elasticity of RAC is considerably influenced by the stiffness of the aggregates (15%), while it is almost unaffected by the shape of the aggregates; (4) both stiffer and elongated aggregates tend to cause micro‐cracking in the interface and premature failure of concrete.
{"title":"Mesoscale modeling of recycled aggregate concrete: A parametric analysis of the quality and shape of aggregate","authors":"Qifan Ren, João Pacheco, Jorge de Brito","doi":"10.1002/suco.202400743","DOIUrl":"https://doi.org/10.1002/suco.202400743","url":null,"abstract":"Recycled aggregate concrete (RAC) is a multi‐phase material, and it is meaningful to investigate the effect of the properties of each phase. However, a comprehensive parametric analysis of these properties is still lacking, which limits a full understanding of the behavior of RAC. This paper uses numerical mesoscale models and contributes to knowledge on this topic. It focuses on the effects of the quality and shape of aggregate since they are relevant to the behavior of concrete but have scarcely been studied for RAC. Their effects on the mechanical response and fracture behavior of RAC were analyzed based on a validated two‐dimensional numerical model. In addition, this paper also justified the choice of the range of the parameters as well as benchmarked the numerical results with the state‐of‐the‐art. The main findings of the paper are: (1) stiffer aggregates decrease the tensile (by up to 29%) and compressive strength of RAC (by up to 7%); (2) aggregate shape moderately influences these properties by up to 10% and 8%; (3) the modulus of elasticity of RAC is considerably influenced by the stiffness of the aggregates (15%), while it is almost unaffected by the shape of the aggregates; (4) both stiffer and elongated aggregates tend to cause micro‐cracking in the interface and premature failure of concrete.","PeriodicalId":21988,"journal":{"name":"Structural Concrete","volume":null,"pages":null},"PeriodicalIF":3.2,"publicationDate":"2024-09-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142203988","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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