Pub Date : 2024-09-05DOI: 10.1016/j.istruc.2024.107154
Kenny Mudenda, Alphose Zingoni
Sustainable design with minimization of carbon footprint requires the consideration of opportunities for optimal material use as well as for re-use and repurposing existing steel members. For steel beams susceptible to lateral-torsional buckling one such opportunity is the use of flange upstands to strengthen existing beams if a change in use requires that the member have more bending strength or stiffness. Flange upstands employed in the study convert a doubly symmetric section into a monosymmetric section. The monosymmetry effect is studied and reveals the existence of a range of upstand heights that can be exploited for increased critical elastic buckling moment. Beyond a given upstand height, the effect of monosymmetry then reduces the critical elastic buckling moment. It is shown that the critical upstand height relates closely to the point at which the monosymmetric section attains a coincident shear center and centroid, a property typically associated with doubly symmetric sections. Elastic and elastic-plastic analysis approaches are used to demonstrate how the stiffeners influence flexural capacity and stiffness properties of the beams. Application of a desirable range of upstand heights for strengthening I-shaped doubly symmetric beams is demonstrated with an example.
{"title":"Steel beam upstands as a strengthening approach for doubly symmetric I-shaped sections","authors":"Kenny Mudenda, Alphose Zingoni","doi":"10.1016/j.istruc.2024.107154","DOIUrl":"https://doi.org/10.1016/j.istruc.2024.107154","url":null,"abstract":"Sustainable design with minimization of carbon footprint requires the consideration of opportunities for optimal material use as well as for re-use and repurposing existing steel members. For steel beams susceptible to lateral-torsional buckling one such opportunity is the use of flange upstands to strengthen existing beams if a change in use requires that the member have more bending strength or stiffness. Flange upstands employed in the study convert a doubly symmetric section into a monosymmetric section. The monosymmetry effect is studied and reveals the existence of a range of upstand heights that can be exploited for increased critical elastic buckling moment. Beyond a given upstand height, the effect of monosymmetry then reduces the critical elastic buckling moment. It is shown that the critical upstand height relates closely to the point at which the monosymmetric section attains a coincident shear center and centroid, a property typically associated with doubly symmetric sections. Elastic and elastic-plastic analysis approaches are used to demonstrate how the stiffeners influence flexural capacity and stiffness properties of the beams. Application of a desirable range of upstand heights for strengthening I-shaped doubly symmetric beams is demonstrated with an example.","PeriodicalId":48642,"journal":{"name":"Structures","volume":null,"pages":null},"PeriodicalIF":4.1,"publicationDate":"2024-09-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142222176","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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 : 2024-09-05DOI: 10.1016/j.istruc.2024.107229
Hanlin Dong, Jingyan Tao, Xijun Wang, Jing Luo
Incorporating slotted-bolted dampers into multi-story hybrid Steel Frame – Light Wood Shear Wall (SF-LWSW) structures presents a promising avenue to enhance seismic resilience. This study conducts comprehensive seismic performance assessments utilizing nonlinear time-history analyses across a suite of earthquakes. The research establishes both a detailed and a simplified numerical modeling approach, employing the “DowelType” hysteretic model tailored to simulate the shear behavior of dowel-type fasteners in wood structures. Key structural design parameters encompass the wall-to-frame stiffness ratio, the damper activation load level, and the slot length. The inter-story drift, the residual drift, the wall force level, and the frame force level are selected as performance indicators. Results show that the dampers are efficient in reducing inter-story drifts, particularly for upper stories and structures with large stiffness ratios. The application of dampers substantially mitigates the shear forces within the walls, culminating in structurally resilient systems even under major earthquakes.
{"title":"Enhancing seismic resilience in hybrid steel frame – Light wood shear wall structures with slotted-bolted dampers: Design parameters and performance evaluation using “DowelType” hysteretic model","authors":"Hanlin Dong, Jingyan Tao, Xijun Wang, Jing Luo","doi":"10.1016/j.istruc.2024.107229","DOIUrl":"https://doi.org/10.1016/j.istruc.2024.107229","url":null,"abstract":"Incorporating slotted-bolted dampers into multi-story hybrid Steel Frame – Light Wood Shear Wall (SF-LWSW) structures presents a promising avenue to enhance seismic resilience. This study conducts comprehensive seismic performance assessments utilizing nonlinear time-history analyses across a suite of earthquakes. The research establishes both a detailed and a simplified numerical modeling approach, employing the “DowelType” hysteretic model tailored to simulate the shear behavior of dowel-type fasteners in wood structures. Key structural design parameters encompass the wall-to-frame stiffness ratio, the damper activation load level, and the slot length. The inter-story drift, the residual drift, the wall force level, and the frame force level are selected as performance indicators. Results show that the dampers are efficient in reducing inter-story drifts, particularly for upper stories and structures with large stiffness ratios. The application of dampers substantially mitigates the shear forces within the walls, culminating in structurally resilient systems even under major earthquakes.","PeriodicalId":48642,"journal":{"name":"Structures","volume":null,"pages":null},"PeriodicalIF":4.1,"publicationDate":"2024-09-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142222166","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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 : 2024-09-05DOI: 10.1016/j.istruc.2024.107122
K.S. Saumiyaa, M. Anbarasu, Chanchal Sonkar
Cold-formed ultra-high-strength steel (UHSS) is gaining attention in the construction sector because of its high strength-to-weight ratio and affordability. However, limited research has been conducted on cold-formed UHSS tubular members under concentric axial loading. This study aims to propose a novel extension of deformation-based method namely; continuous strength method (CSM) and AISI based direct strength method (DSM) design methodologies for cold-formed UHSS columns. A nonlinear finite element (FE) model was developed using the ABAQUS package for cold-formed UHSS columns, incorporating initial geometric imperfections and material non-linearities. The developed FE model was then validated against experimental test results from the literature for cold-formed UHSS columns. Parametric studies were conducted on cold-formed UHSS hollow sections to comprehensively understand their axial behaviour, utilizing the validated FE model and to generate additional data sets. A total of 146 FE models were analyzed by varying the thickness of the cold-formed steel sheets (4, 5, 6, 8, 10 and 12 mm), as well as cross-section dimensions, to account for broad range of cross-sectional slenderness ratios. The obtained FE results were compared with the AISI based current DSM and also with CSM/DSM based design rules recommended by other researchers in the literature. The specimens considered in the present study demonstrated failure due to local buckling. The numerical results showed that existing standards lack precise design procedures for cold-formed UHSS hollow columns, indicating a need for further research to develop accurate design procedures. Therefore, the proposed rational extension of deformation-based CSM and DSM methodologies provides more precise and less scattered capacity estimations for cold-formed UHSS columns, as verified through reliability analysis.
{"title":"Behaviour and design of cold-formed ultra-high-strength steel hollow section column members","authors":"K.S. Saumiyaa, M. Anbarasu, Chanchal Sonkar","doi":"10.1016/j.istruc.2024.107122","DOIUrl":"https://doi.org/10.1016/j.istruc.2024.107122","url":null,"abstract":"Cold-formed ultra-high-strength steel (UHSS) is gaining attention in the construction sector because of its high strength-to-weight ratio and affordability. However, limited research has been conducted on cold-formed UHSS tubular members under concentric axial loading. This study aims to propose a novel extension of deformation-based method namely; continuous strength method (CSM) and AISI based direct strength method (DSM) design methodologies for cold-formed UHSS columns. A nonlinear finite element (FE) model was developed using the ABAQUS package for cold-formed UHSS columns, incorporating initial geometric imperfections and material non-linearities. The developed FE model was then validated against experimental test results from the literature for cold-formed UHSS columns. Parametric studies were conducted on cold-formed UHSS hollow sections to comprehensively understand their axial behaviour, utilizing the validated FE model and to generate additional data sets. A total of 146 FE models were analyzed by varying the thickness of the cold-formed steel sheets (4, 5, 6, 8, 10 and 12 mm), as well as cross-section dimensions, to account for broad range of cross-sectional slenderness ratios. The obtained FE results were compared with the AISI based current DSM and also with CSM/DSM based design rules recommended by other researchers in the literature. The specimens considered in the present study demonstrated failure due to local buckling. The numerical results showed that existing standards lack precise design procedures for cold-formed UHSS hollow columns, indicating a need for further research to develop accurate design procedures. Therefore, the proposed rational extension of deformation-based CSM and DSM methodologies provides more precise and less scattered capacity estimations for cold-formed UHSS columns, as verified through reliability analysis.","PeriodicalId":48642,"journal":{"name":"Structures","volume":null,"pages":null},"PeriodicalIF":4.1,"publicationDate":"2024-09-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142222170","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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 : 2024-09-04DOI: 10.1016/j.istruc.2024.107214
Guilherme dos Santos Silva, Silvio Cesar de Oliveira, Pedro Ignácio Lima Gadêlha Jardim, Elvys Dias Reis, Vinícius Borges de Moura Aquino, André Luis Christoforo
Engineered wood products, such as Cross Laminated Timber (CLT), have been widely used in civil construction. Standard calculation methods, like the Gamma method commonly used in structural design, estimate the bending stiffness of elements. However, these methods are based on one-dimensional solids (bar elements), which can be limiting. This limitation may result in inaccurate estimates, especially when the panel's dimensions, measured in the median plane, significantly differ by an order of magnitude. In this research, a parametric study was carried out using the finite element method (three-dimensional approach), varying the panel's dimensions (width and length), the layers' thickness, and the number of layers (cross-section height), and adopting elastic properties considering either the wood's orthotropy or the rolling shear estimation (108 numerical simulations in all). Based on the parameterization, multiple variable regression models were used to establish a correction coefficient to be incorporated into the Gamma method to improve its accuracy in estimating bending stiffness. Therefore, the single adjusted equation (considering the wood's orthotropy) showed values closer to the numerical ones (MAPE = 0.95 %, RMSE = 2.96 × 10 Nmm, and CV = 1.60 %) than those obtained by the Gamma method (MAPE = 2.13 %, RMSE = 7.47 × 10 Nmm, and CV = 4.04 %).
{"title":"Proposed correction to the Gamma method for estimating the bending stiffness of CLT panels","authors":"Guilherme dos Santos Silva, Silvio Cesar de Oliveira, Pedro Ignácio Lima Gadêlha Jardim, Elvys Dias Reis, Vinícius Borges de Moura Aquino, André Luis Christoforo","doi":"10.1016/j.istruc.2024.107214","DOIUrl":"https://doi.org/10.1016/j.istruc.2024.107214","url":null,"abstract":"Engineered wood products, such as Cross Laminated Timber (CLT), have been widely used in civil construction. Standard calculation methods, like the Gamma method commonly used in structural design, estimate the bending stiffness of elements. However, these methods are based on one-dimensional solids (bar elements), which can be limiting. This limitation may result in inaccurate estimates, especially when the panel's dimensions, measured in the median plane, significantly differ by an order of magnitude. In this research, a parametric study was carried out using the finite element method (three-dimensional approach), varying the panel's dimensions (width and length), the layers' thickness, and the number of layers (cross-section height), and adopting elastic properties considering either the wood's orthotropy or the rolling shear estimation (108 numerical simulations in all). Based on the parameterization, multiple variable regression models were used to establish a correction coefficient to be incorporated into the Gamma method to improve its accuracy in estimating bending stiffness. Therefore, the single adjusted equation (considering the wood's orthotropy) showed values closer to the numerical ones (MAPE = 0.95 %, RMSE = 2.96 × 10 Nmm, and CV = 1.60 %) than those obtained by the Gamma method (MAPE = 2.13 %, RMSE = 7.47 × 10 Nmm, and CV = 4.04 %).","PeriodicalId":48642,"journal":{"name":"Structures","volume":null,"pages":null},"PeriodicalIF":4.1,"publicationDate":"2024-09-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142222172","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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 : 2024-09-04DOI: 10.1016/j.istruc.2024.107148
Lei Wang, Xiaoling Wang, Jun Zhang, Jiajun Wang, Hongling Yu
Dam safety monitoring systems collect a significant amount of data, including numerous instances of abnormal data attributed to factors such as aging equipment and recording errors. The accurate detection and classification of abnormal data can effectively enhance the reliability of rockfill dam safety assessments based on monitoring data. Note that the scarcity of the abnormal data in actual monitoring datasets poses a significant challenge to existing data-driven anomaly detection studies. To address these issues, we develop a novel self-supervised learning-based framework for abnormal data detection and classification of rockfill dam deformation data. This framework includes an abnormal data detection method based on transformers and synthetic abnormal data. By analyzing and further modeling the real-world abnormal data, a criterion for synthesizing abnormal data is proposed to augment the scale of abnormal data. Additionally, we introduce an abnormal data classification method using imaging time series, which captures the multi-scale features of sequence data in a higher dimension by encoding it into image representations and employing a residual network (ResNet) for feature extraction. The effectiveness of the proposed approach is demonstrated through an engineering case study. The F1 scores for abnormal data detection and classification are 0.9722 and 0.9596, respectively, which surpass those of other conventional methods. The results demonstrate that the proposed approach achieves high-precision detection and classification of abnormal data, even under adverse conditions where abnormal data are sparse, thus ensuring reliable safety assessment of rockfill dams.
大坝安全监测系统收集了大量数据，其中不乏因设备老化和记录错误等因素造成的异常数据。对异常数据进行准确检测和分类，可有效提高基于监测数据的堆石坝安全评估的可靠性。需要注意的是，实际监测数据集中异常数据的稀缺性给现有的数据驱动异常检测研究带来了巨大挑战。为解决这些问题，我们开发了一种基于自监督学习的新型框架，用于对堆石坝变形数据进行异常数据检测和分类。该框架包括基于变压器和合成异常数据的异常数据检测方法。通过对真实世界异常数据的分析和进一步建模，我们提出了一种合成异常数据的标准，以扩大异常数据的规模。此外，我们还介绍了一种使用成像时间序列的异常数据分类方法，该方法通过将序列数据编码为图像表示并使用残差网络（ResNet）进行特征提取，在更高的维度上捕捉序列数据的多尺度特征。通过工程案例研究证明了所提方法的有效性。异常数据检测和分类的 F1 分数分别为 0.9722 和 0.9596，超过了其他传统方法。结果表明，即使在异常数据稀少的不利条件下，所提出的方法也能实现对异常数据的高精度检测和分类，从而确保对堆石坝进行可靠的安全评估。
{"title":"A self-supervised learning-based approach for detection and classification of dam deformation monitoring abnormal data with imaging time series","authors":"Lei Wang, Xiaoling Wang, Jun Zhang, Jiajun Wang, Hongling Yu","doi":"10.1016/j.istruc.2024.107148","DOIUrl":"https://doi.org/10.1016/j.istruc.2024.107148","url":null,"abstract":"Dam safety monitoring systems collect a significant amount of data, including numerous instances of abnormal data attributed to factors such as aging equipment and recording errors. The accurate detection and classification of abnormal data can effectively enhance the reliability of rockfill dam safety assessments based on monitoring data. Note that the scarcity of the abnormal data in actual monitoring datasets poses a significant challenge to existing data-driven anomaly detection studies. To address these issues, we develop a novel self-supervised learning-based framework for abnormal data detection and classification of rockfill dam deformation data. This framework includes an abnormal data detection method based on transformers and synthetic abnormal data. By analyzing and further modeling the real-world abnormal data, a criterion for synthesizing abnormal data is proposed to augment the scale of abnormal data. Additionally, we introduce an abnormal data classification method using imaging time series, which captures the multi-scale features of sequence data in a higher dimension by encoding it into image representations and employing a residual network (ResNet) for feature extraction. The effectiveness of the proposed approach is demonstrated through an engineering case study. The F1 scores for abnormal data detection and classification are 0.9722 and 0.9596, respectively, which surpass those of other conventional methods. The results demonstrate that the proposed approach achieves high-precision detection and classification of abnormal data, even under adverse conditions where abnormal data are sparse, thus ensuring reliable safety assessment of rockfill dams.","PeriodicalId":48642,"journal":{"name":"Structures","volume":null,"pages":null},"PeriodicalIF":4.1,"publicationDate":"2024-09-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142222190","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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 : 2024-09-04DOI: 10.1016/j.istruc.2024.107115
Paulo Feghali, Pablo Krahl, Flávio de Andrade Silva
Ultra-high-performance concrete is a material with enhanced mechanical properties compared to conventional concrete. These characteristics make it possible to conceive structural elements with reduced cross-sections and lower reinforcement ratios (RR) to withstand the same load capacities as conventional concrete elements. However, UHPC beams with low RRs exhibit low ductility indexes due to localization phenomena. The proposed methodology uses a genetic algorithm routine to generate an optimized cross-section to reduce UHPC consumption, decreasing the RR. The optimization methodology was based on finite element models to increase load capacity while maintaining a target minimum ductility. The experimental program tested three reference rectangular beams with different RRs and one beam with an optimized cross-section. The tested beams were then modeled using the finite element method in the Abaqus software through a modeling technique that considered the variability of the material properties by dividing the element’s volume into parts with different material properties. The results showed that changing the cross-section’s format can increase load-bearing capacity while maintaining target ductility.
{"title":"Optimization of UHPC beams under flexural loading: A numerical and experimental investigation","authors":"Paulo Feghali, Pablo Krahl, Flávio de Andrade Silva","doi":"10.1016/j.istruc.2024.107115","DOIUrl":"https://doi.org/10.1016/j.istruc.2024.107115","url":null,"abstract":"Ultra-high-performance concrete is a material with enhanced mechanical properties compared to conventional concrete. These characteristics make it possible to conceive structural elements with reduced cross-sections and lower reinforcement ratios (RR) to withstand the same load capacities as conventional concrete elements. However, UHPC beams with low RRs exhibit low ductility indexes due to localization phenomena. The proposed methodology uses a genetic algorithm routine to generate an optimized cross-section to reduce UHPC consumption, decreasing the RR. The optimization methodology was based on finite element models to increase load capacity while maintaining a target minimum ductility. The experimental program tested three reference rectangular beams with different RRs and one beam with an optimized cross-section. The tested beams were then modeled using the finite element method in the Abaqus software through a modeling technique that considered the variability of the material properties by dividing the element’s volume into parts with different material properties. The results showed that changing the cross-section’s format can increase load-bearing capacity while maintaining target ductility.","PeriodicalId":48642,"journal":{"name":"Structures","volume":null,"pages":null},"PeriodicalIF":4.1,"publicationDate":"2024-09-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142222193","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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 : 2024-09-04DOI: 10.1016/j.istruc.2024.107147
R. Mohana, S.M.Leela Bharathi
In order to develop an impact resistant ferrocement panels in a sustainable way, first time the nano fly ash based geopolymer mortar was employed in this research work by using crumb rubber and plastic pellets as partial replacement materials of fine aggregates. The type and combinations of meshing reinforcement were optimized numerically by using the finite element analysis software Ansys. Also, the role of using crumb rubber and plastic pellets on the impact resistant characteristics of the nano fly ash based geopolymer ferrocement panels were studied experimentally and compared by conducting the direct fall impact test. From the results, it was observed that the use of nano fly ash based geopolymer mortar completely eliminates the need of super plasticizer and oven curing. Also, the use of crumb rubber and plastic pellets resulted in the maximum impact energy absorption of 2949.14 joules and 3483 joules which is 48.7 % and 75.6 % higher than control ferrocement panels. The excellent energy absorption capacity and post-impact failure of the developed panels will lead to the exploration of extensive impact resistant structural applications such as deck slabs, abutments, railway girders etc.
{"title":"Assessment on the mesh and mortar effect of the impact resistant nano fly ash based geopolymer ferrocement panels using rubber and plastic aggregates","authors":"R. Mohana, S.M.Leela Bharathi","doi":"10.1016/j.istruc.2024.107147","DOIUrl":"https://doi.org/10.1016/j.istruc.2024.107147","url":null,"abstract":"In order to develop an impact resistant ferrocement panels in a sustainable way, first time the nano fly ash based geopolymer mortar was employed in this research work by using crumb rubber and plastic pellets as partial replacement materials of fine aggregates. The type and combinations of meshing reinforcement were optimized numerically by using the finite element analysis software Ansys. Also, the role of using crumb rubber and plastic pellets on the impact resistant characteristics of the nano fly ash based geopolymer ferrocement panels were studied experimentally and compared by conducting the direct fall impact test. From the results, it was observed that the use of nano fly ash based geopolymer mortar completely eliminates the need of super plasticizer and oven curing. Also, the use of crumb rubber and plastic pellets resulted in the maximum impact energy absorption of 2949.14 joules and 3483 joules which is 48.7 % and 75.6 % higher than control ferrocement panels. The excellent energy absorption capacity and post-impact failure of the developed panels will lead to the exploration of extensive impact resistant structural applications such as deck slabs, abutments, railway girders etc.","PeriodicalId":48642,"journal":{"name":"Structures","volume":null,"pages":null},"PeriodicalIF":4.1,"publicationDate":"2024-09-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142222191","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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 : 2024-09-04DOI: 10.1016/j.istruc.2024.107198
Qingdong Chai, Changyuan Yu, Yan Qing Wang
The present study proposes a semi-analytical method for solving the frequency response of conical shells with bolt boundaries. The non-uniform artificial spring technology is employed to simulate the bolt loosening or no-loosening boundary conditions, which is closer to the real bolt contact situation. Donnell’s shell theory as well as the displacement assumption of Chebyshev polynomials are employed in theoretical modeling, and the governing equation is obtained by the Lagrange equation. The rationality of the established model is confirmed through comparisons with existing literature and modal tests, revealing that the maximum errors of theoretical results compared to literature and experiment are 0.82 % and 3.9 %, respectively. From both theoretical and experimental aspects, the frequency response of conical shells with bolt loosening boundary conditions are explored. Subsequently, the combined effects of cone sizes and loosening degrees on frequency responses of bolted conical shells are analyzed. Results demonstrate that bolt loosening significantly reduces the fundamental frequency while this attenuation diminishes with increasing mode order. The increase in the bolt loosening degree results in the attenuation of the formant value, confirming an increase in the modal damping ratio. The influence of cone angle on frequency response is directly tied to the bolt loosening degree. The established model proves dependable for predicting the vibration characteristics of bolted conical shells under varying loosening degrees, offering valuable insights for the design and operational phases of thin-walled conical shell structures.
{"title":"Theory and experiment studies on frequency response of conical shells with bolt boundary","authors":"Qingdong Chai, Changyuan Yu, Yan Qing Wang","doi":"10.1016/j.istruc.2024.107198","DOIUrl":"https://doi.org/10.1016/j.istruc.2024.107198","url":null,"abstract":"The present study proposes a semi-analytical method for solving the frequency response of conical shells with bolt boundaries. The non-uniform artificial spring technology is employed to simulate the bolt loosening or no-loosening boundary conditions, which is closer to the real bolt contact situation. Donnell’s shell theory as well as the displacement assumption of Chebyshev polynomials are employed in theoretical modeling, and the governing equation is obtained by the Lagrange equation. The rationality of the established model is confirmed through comparisons with existing literature and modal tests, revealing that the maximum errors of theoretical results compared to literature and experiment are 0.82 % and 3.9 %, respectively. From both theoretical and experimental aspects, the frequency response of conical shells with bolt loosening boundary conditions are explored. Subsequently, the combined effects of cone sizes and loosening degrees on frequency responses of bolted conical shells are analyzed. Results demonstrate that bolt loosening significantly reduces the fundamental frequency while this attenuation diminishes with increasing mode order. The increase in the bolt loosening degree results in the attenuation of the formant value, confirming an increase in the modal damping ratio. The influence of cone angle on frequency response is directly tied to the bolt loosening degree. The established model proves dependable for predicting the vibration characteristics of bolted conical shells under varying loosening degrees, offering valuable insights for the design and operational phases of thin-walled conical shell structures.","PeriodicalId":48642,"journal":{"name":"Structures","volume":null,"pages":null},"PeriodicalIF":4.1,"publicationDate":"2024-09-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142222175","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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 : 2024-09-04DOI: 10.1016/j.istruc.2024.107153
Pushkal Badoniya, Manu Srivastava, Prashant K. Jain, Abhay Kumar
The construction industry has always focused on cost-effective manufacturing techniques for fabricating large metal structures. Wire arc additive manufacturing (WAAM) is a promising technology for fabricating large-metal components of moderate complexity at a faster rate than other metal additive manufacturing methods. WAAM-fabricated structures exhibit microstructural heterogeneity and anisotropic mechanical characteristics. Post-deposition heat treatment (PDHT) plays an important role in strengthening fabricated structures by improving microstructural uniformity and reducing inherent anisotropy. This study aims to investigate the effect of PDHT on the mechanical and microstructural characteristics of WAAM-fabricated low carbon steel (LCS) ER70S-6. Optical macrograph results showed that the as-deposited (LCS-AD) and heat-treated (LCS-HT) samples mainly consisted of polygonal ferrite and pearlite phases. However, a microscopic study of both samples reveals the presence of finely polygonal ferrite and laminar pearlite along with traces of martensite and precipitated carbides in LCS-HT. Whereas, LCS-AD exhibits the presence of only polygonal ferrite and laminar pearlite. The average grain size diameter of LCS-HT was found to be less than that of the as-deposited sample. The increment in the distribution of high-angle grain boundaries in LCS-HT confirms grain boundary migration and recrystallization. Mechanical test results show that PDHT improves average microhardness and mechanical strength by reducing the anisotropic nature and interlayer defects of the sample. The average microhardness for LCS-HT was increased by 16.43 HV. Similarly, the yield stress, ultimate tensile stress, and elongation percentage for LCS-HT compared to LCS-AD enhanced on average by 6.39 %, 15.61 %, and 32.72 %, respectively. Fractography analysis shows that PDHT facilitated more uniform tensile fracture for LCS-HT vertical samples. While LCS-AD vertical samples exhibit ductile-brittle fractures due to their interlayer defects.
{"title":"Microstructural refinement and strengthening of wire arc additively manufactured construction grade low carbon steel through heat treatment","authors":"Pushkal Badoniya, Manu Srivastava, Prashant K. Jain, Abhay Kumar","doi":"10.1016/j.istruc.2024.107153","DOIUrl":"https://doi.org/10.1016/j.istruc.2024.107153","url":null,"abstract":"The construction industry has always focused on cost-effective manufacturing techniques for fabricating large metal structures. Wire arc additive manufacturing (WAAM) is a promising technology for fabricating large-metal components of moderate complexity at a faster rate than other metal additive manufacturing methods. WAAM-fabricated structures exhibit microstructural heterogeneity and anisotropic mechanical characteristics. Post-deposition heat treatment (PDHT) plays an important role in strengthening fabricated structures by improving microstructural uniformity and reducing inherent anisotropy. This study aims to investigate the effect of PDHT on the mechanical and microstructural characteristics of WAAM-fabricated low carbon steel (LCS) ER70S-6. Optical macrograph results showed that the as-deposited (LCS-AD) and heat-treated (LCS-HT) samples mainly consisted of polygonal ferrite and pearlite phases. However, a microscopic study of both samples reveals the presence of finely polygonal ferrite and laminar pearlite along with traces of martensite and precipitated carbides in LCS-HT. Whereas, LCS-AD exhibits the presence of only polygonal ferrite and laminar pearlite. The average grain size diameter of LCS-HT was found to be less than that of the as-deposited sample. The increment in the distribution of high-angle grain boundaries in LCS-HT confirms grain boundary migration and recrystallization. Mechanical test results show that PDHT improves average microhardness and mechanical strength by reducing the anisotropic nature and interlayer defects of the sample. The average microhardness for LCS-HT was increased by 16.43 HV. Similarly, the yield stress, ultimate tensile stress, and elongation percentage for LCS-HT compared to LCS-AD enhanced on average by 6.39 %, 15.61 %, and 32.72 %, respectively. Fractography analysis shows that PDHT facilitated more uniform tensile fracture for LCS-HT vertical samples. While LCS-AD vertical samples exhibit ductile-brittle fractures due to their interlayer defects.","PeriodicalId":48642,"journal":{"name":"Structures","volume":null,"pages":null},"PeriodicalIF":4.1,"publicationDate":"2024-09-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142222194","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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 : 2024-09-04DOI: 10.1016/j.istruc.2024.107137
Maryam Trad, Ibrahim Bitar, Stéphane Grange, Benjamin Richard
In this paper, a new multiscale macro-element formulation for the steel–concrete interface modeling is proposed. This element allows for the representation of the behavior of steel and the interface zone surrounding it. It can also model the interfacial bond stresses in between. Compared to conventional interface models of the literature, which employ separate mesh elements for the steel and the interface, utilizing a macro-element to model both components simplifies the creation of a reinforced concrete structure mesh. Moreover, the macro-element equilibrium is solved using a sub-structuring method that aims to reduce the computational cost. At the global level, it is considered as a four-node element linked to two-dimensional and three-dimensional concrete elements. At the local level, an assembly of multiple three-node bar elements with bond stresses is performed. An inner mesh discretization is therefore possible at the local level independently of the global level. The coupling between the two modeling scales is done using a static condensation technique. The formulation of the macro-element is presented in this paper. A selection of numerical examples is provided. The presented applications demonstrate the robustness of the proposed interface model and its capacity to reproduce the experimental behavior of reinforced concrete structural elements.
{"title":"A multiscale steel–concrete interface model for structural applications","authors":"Maryam Trad, Ibrahim Bitar, Stéphane Grange, Benjamin Richard","doi":"10.1016/j.istruc.2024.107137","DOIUrl":"https://doi.org/10.1016/j.istruc.2024.107137","url":null,"abstract":"In this paper, a new multiscale macro-element formulation for the steel–concrete interface modeling is proposed. This element allows for the representation of the behavior of steel and the interface zone surrounding it. It can also model the interfacial bond stresses in between. Compared to conventional interface models of the literature, which employ separate mesh elements for the steel and the interface, utilizing a macro-element to model both components simplifies the creation of a reinforced concrete structure mesh. Moreover, the macro-element equilibrium is solved using a sub-structuring method that aims to reduce the computational cost. At the global level, it is considered as a four-node element linked to two-dimensional and three-dimensional concrete elements. At the local level, an assembly of multiple three-node bar elements with bond stresses is performed. An inner mesh discretization is therefore possible at the local level independently of the global level. The coupling between the two modeling scales is done using a static condensation technique. The formulation of the macro-element is presented in this paper. A selection of numerical examples is provided. The presented applications demonstrate the robustness of the proposed interface model and its capacity to reproduce the experimental behavior of reinforced concrete structural elements.","PeriodicalId":48642,"journal":{"name":"Structures","volume":null,"pages":null},"PeriodicalIF":4.1,"publicationDate":"2024-09-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142222192","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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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