Pub Date : 2026-02-12DOI: 10.1016/j.engstruct.2026.122312
Hermawan Sutejo , Yu-Chen Ou
Buckling of longitudinal reinforcement in compression, often followed by low-cycle fatigue fracture in tension, is a primary mechanism driving strength degradation in reinforced concrete flexural members subjected to large-displacement reversals. This study proposes a mechanics-based analytical model to predict the buckling length of longitudinal reinforcement restrained by rectilinear transverse reinforcement. The model captures buckling lengths over a non-integer interval of tie spacings by incorporating end transition regions beyond the outermost hoops bounding the buckling region. The buckling-restraint stiffness is formulated by combining axial and bending components. The axial component is adjusted to reflect hoop type and hook-bent angle through a geometric effectiveness factor, while the bending component is evaluated from the flexural response of transverse ties. The model is validated using 38 beam and 32 column specimens collected from the literature. The proposed model achieves improved accuracy relative to the models by Su et al. and Dhakal & Maekawa, with average prediction errors of 6.5 % for beams and 10.1 % for columns, compared to 9.8 % and 12.3 % for Su et al. and 26.0 % and 22.3 % for Dhakal & Maekawa, respectively. Parametric reanalysis shows that excluding either the axial reduction factor or the bending component increases the error by about 20 %, and neglecting both increases the error by up to 55 %, demonstrating that both mechanisms are essential for reliable buckling-length prediction.
{"title":"Prediction model for longitudinal reinforcement buckling in reinforced concrete beams and columns with rectilinear hoops","authors":"Hermawan Sutejo , Yu-Chen Ou","doi":"10.1016/j.engstruct.2026.122312","DOIUrl":"10.1016/j.engstruct.2026.122312","url":null,"abstract":"<div><div>Buckling of longitudinal reinforcement in compression, often followed by low-cycle fatigue fracture in tension, is a primary mechanism driving strength degradation in reinforced concrete flexural members subjected to large-displacement reversals. This study proposes a mechanics-based analytical model to predict the buckling length of longitudinal reinforcement restrained by rectilinear transverse reinforcement. The model captures buckling lengths over a non-integer interval of tie spacings by incorporating end transition regions beyond the outermost hoops bounding the buckling region. The buckling-restraint stiffness is formulated by combining axial and bending components. The axial component is adjusted to reflect hoop type and hook-bent angle through a geometric effectiveness factor, while the bending component is evaluated from the flexural response of transverse ties. The model is validated using 38 beam and 32 column specimens collected from the literature. The proposed model achieves improved accuracy relative to the models by Su et al. and Dhakal & Maekawa, with average prediction errors of 6.5 % for beams and 10.1 % for columns, compared to 9.8 % and 12.3 % for Su et al. and 26.0 % and 22.3 % for Dhakal & Maekawa, respectively. Parametric reanalysis shows that excluding either the axial reduction factor or the bending component increases the error by about 20 %, and neglecting both increases the error by up to 55 %, demonstrating that both mechanisms are essential for reliable buckling-length prediction.</div></div>","PeriodicalId":11763,"journal":{"name":"Engineering Structures","volume":"353 ","pages":"Article 122312"},"PeriodicalIF":6.4,"publicationDate":"2026-02-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146154156","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-02-12DOI: 10.1016/j.engstruct.2026.122325
Trevor Zhiqing Yeow , Koichi Kusunoki
In structural health monitoring, correct classification of a building’s inelastic deformation mode (i.e., total-yield or soft-story) is needed for accurate safety evaluations. However, sensors are usually not placed on all floors in most applications, making inelastic deformation mode classification difficult. In this study, features based on plastic displacements and sensor location are proposed for training and evaluating inelastic deformation mode classification models. The importance of the newly proposed features was compared against other features proposed in literature based on peak floor acceleration and velocity response, cumulative absolute velocity and jerk. A large building response database was created from numerical simulations of a wide range of reinforced concrete frame structures exhibiting different inelastic deformation modes for evaluating feature importance. It was found that the newly proposed features ranked highly when applying the Minimum Redundancy Maximum Relevancy algorithm to the response database compared to past features. Furthermore, a k-Nearest Neighbor classification model trained using a feature set containing the proposed features and building-level ductility response resulted in a more accurate model compared to only using existing features (misclassification rate of 10 % versus 29 %). These results demonstrate the suitability of the proposed features for training and evaluating building inelastic deformation mode classification models.
{"title":"Plastic displacement features for classifying the inelastic deformation mode of instrumented buildings with few sensors considering sensor locations","authors":"Trevor Zhiqing Yeow , Koichi Kusunoki","doi":"10.1016/j.engstruct.2026.122325","DOIUrl":"10.1016/j.engstruct.2026.122325","url":null,"abstract":"<div><div>In structural health monitoring, correct classification of a building’s inelastic deformation mode (i.e., total-yield or soft-story) is needed for accurate safety evaluations. However, sensors are usually not placed on all floors in most applications, making inelastic deformation mode classification difficult. In this study, features based on plastic displacements and sensor location are proposed for training and evaluating inelastic deformation mode classification models. The importance of the newly proposed features was compared against other features proposed in literature based on peak floor acceleration and velocity response, cumulative absolute velocity and jerk. A large building response database was created from numerical simulations of a wide range of reinforced concrete frame structures exhibiting different inelastic deformation modes for evaluating feature importance. It was found that the newly proposed features ranked highly when applying the Minimum Redundancy Maximum Relevancy algorithm to the response database compared to past features. Furthermore, a <em>k</em>-Nearest Neighbor classification model trained using a feature set containing the proposed features and building-level ductility response resulted in a more accurate model compared to only using existing features (misclassification rate of 10 % versus 29 %). These results demonstrate the suitability of the proposed features for training and evaluating building inelastic deformation mode classification models.</div></div>","PeriodicalId":11763,"journal":{"name":"Engineering Structures","volume":"353 ","pages":"Article 122325"},"PeriodicalIF":6.4,"publicationDate":"2026-02-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146154153","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-02-12DOI: 10.1016/j.engstruct.2026.122330
Zhu-Yu Sun , Yu-Tao Guo , Kang Ge , Chao Hou , Zhen-Zhong Hu
Offshore bridges operate in complex ocean environments, making structural analysis, design, and monitoring more challenging. Existing typical time history analysis and nonlinear model updating based on finite-element methods are computationally intensive and time consuming, limiting the usage in many scenarios. To create a more efficient analytical tool, a Deep Learning-based Offshore Bridge Predictor (DeepOBP) is proposed. The model integrates structural characteristics and coupled dynamic loads in the ocean environments, enabling millisecond level and high precision nonlinear dynamic offshore bridge response predictions. A differentiable structural inverse framework (Inverse DeepOBP) couples the surrogate model with gradient-based optimization is further developed to enable rapid damage identification and model calibration for structural health monitoring. The experimental results show that DeepOBP demonstrates high accuracy under both normal operating conditions and multihazard coupled conditions, with R² = 0.93 and 0.92. Inverse DeepOBP delivers more than a 10-fold and more than a 104-fold speed-up over surrogate-based model updating with the heuristic algorithm and nonlinear finite element model updating, respectively, while maintaining relative errors below 7 % for each identified parameter, enabling efficient structural analyses and real-time monitoring.
{"title":"Deep learning-based realtime multiload response prediction and inverse analysis of offshore bridges","authors":"Zhu-Yu Sun , Yu-Tao Guo , Kang Ge , Chao Hou , Zhen-Zhong Hu","doi":"10.1016/j.engstruct.2026.122330","DOIUrl":"10.1016/j.engstruct.2026.122330","url":null,"abstract":"<div><div>Offshore bridges operate in complex ocean environments, making structural analysis, design, and monitoring more challenging. Existing typical time history analysis and nonlinear model updating based on finite-element methods are computationally intensive and time consuming, limiting the usage in many scenarios. To create a more efficient analytical tool, a Deep Learning-based Offshore Bridge Predictor (DeepOBP) is proposed. The model integrates structural characteristics and coupled dynamic loads in the ocean environments, enabling millisecond level and high precision nonlinear dynamic offshore bridge response predictions. A differentiable structural inverse framework (Inverse DeepOBP) couples the surrogate model with gradient-based optimization is further developed to enable rapid damage identification and model calibration for structural health monitoring. The experimental results show that DeepOBP demonstrates high accuracy under both normal operating conditions and multihazard coupled conditions, with R² = 0.93 and 0.92. Inverse DeepOBP delivers more than a 10-fold and more than a 10<sup>4</sup>-fold speed-up over surrogate-based model updating with the heuristic algorithm and nonlinear finite element model updating, respectively, while maintaining relative errors below 7 % for each identified parameter, enabling efficient structural analyses and real-time monitoring.</div></div>","PeriodicalId":11763,"journal":{"name":"Engineering Structures","volume":"353 ","pages":"Article 122330"},"PeriodicalIF":6.4,"publicationDate":"2026-02-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146154154","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-02-12DOI: 10.1016/j.engstruct.2026.122350
Quanjun Hua , Qing Chun , Yu Yuan
Historical masonry arch bridges represent critical transportation infrastructure and irreplaceable cultural heritage, yet they face severe threats from floating debris impact during extreme hydrological events. Existing research primarily focuses on ship impact on modern bridges, paying insufficient attention to the material degradation caused by long-term weathering and water erosion. Moreover, current simulation methods often lack adequate bidirectional fluid-structure interaction (FSI) simulation for woody debris impact, leading to inaccurate safety evaluations. This study takes the Nanjing Putang Bridge—a nine-span historical masonry arch bridge constructed in 1512 and a Chinese key national cultural heritage site—as a case study. Two key contributions are presented: first, the development of a two-stage finite element model updating approach based on operational modal analysis to map material degradation; and second, the integration of the updated model with bidirectional FSI simulation to systematically investigate the bridge’s mechanical response under woody debris impact. Results show that under combined water flow and debris impact, tensile stress concentrates on the side wall of Pier No. 5 and joints between Arch No. 3 to No. 6 and their respective arch shoulder walls, without causing structural collapse. Additionally, existing ship collision codes overestimate the impact force of floating woody debris, while the current simulation impact values are only 13–41 % of code-derived ones. This overestimation is corrected by introducing a regression-derived dynamic correction coefficient. This study provides a reliable numerical framework for the safety assessment of historical masonry arch bridges against floating debris impact.
{"title":"Floating debris impact on historical masonry arch bridges: Model updating and fluid-structure interaction simulation","authors":"Quanjun Hua , Qing Chun , Yu Yuan","doi":"10.1016/j.engstruct.2026.122350","DOIUrl":"10.1016/j.engstruct.2026.122350","url":null,"abstract":"<div><div>Historical masonry arch bridges represent critical transportation infrastructure and irreplaceable cultural heritage, yet they face severe threats from floating debris impact during extreme hydrological events. Existing research primarily focuses on ship impact on modern bridges, paying insufficient attention to the material degradation caused by long-term weathering and water erosion. Moreover, current simulation methods often lack adequate bidirectional fluid-structure interaction (FSI) simulation for woody debris impact, leading to inaccurate safety evaluations. This study takes the Nanjing Putang Bridge—a nine-span historical masonry arch bridge constructed in 1512 and a Chinese key national cultural heritage site—as a case study. Two key contributions are presented: first, the development of a two-stage finite element model updating approach based on operational modal analysis to map material degradation; and second, the integration of the updated model with bidirectional FSI simulation to systematically investigate the bridge’s mechanical response under woody debris impact. Results show that under combined water flow and debris impact, tensile stress concentrates on the side wall of Pier No. 5 and joints between Arch No. 3 to No. 6 and their respective arch shoulder walls, without causing structural collapse. Additionally, existing ship collision codes overestimate the impact force of floating woody debris, while the current simulation impact values are only 13–41 % of code-derived ones. This overestimation is corrected by introducing a regression-derived dynamic correction coefficient. This study provides a reliable numerical framework for the safety assessment of historical masonry arch bridges against floating debris impact.</div></div>","PeriodicalId":11763,"journal":{"name":"Engineering Structures","volume":"353 ","pages":"Article 122350"},"PeriodicalIF":6.4,"publicationDate":"2026-02-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146170744","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-02-12DOI: 10.1016/j.engstruct.2026.122339
Yirui Sun, Yujie Chen, Zonghan Xie
Advances in modelling and simulation are driving innovation in mechanical joint design. However, the lack of standardized evaluation criteria hinders meaningful comparison across geometries, rendering the rational design and improvement difficult. To address this, we studied three representative joint shapes—trapezoid, circle, and ellipse. Finite element analysis (FEA) was employed to evaluate their tensile performance within the elastic regime. The elliptical joint showed the highest stiffness, while the circular joint exhibited the greatest load capability and resilience. Joint performance was also influenced by friction coefficient, yield strength, and blade number. Applying edge constraints notably enhanced performance, especially for single-blade joints, with up to 7.6 × increase in load capability and 5.4 × in resilience for circular joints, and 11.2 × in stiffness for trapezoidal joints. An Ashby-type plot was developed to support the comparative selection of joint designs. These results provide a foundation for establishing standardized evaluation criteria for tensile joint performance.
{"title":"Computational analysis of interlocking joints with different geometries under tensile loads","authors":"Yirui Sun, Yujie Chen, Zonghan Xie","doi":"10.1016/j.engstruct.2026.122339","DOIUrl":"10.1016/j.engstruct.2026.122339","url":null,"abstract":"<div><div>Advances in modelling and simulation are driving innovation in mechanical joint design. However, the lack of standardized evaluation criteria hinders meaningful comparison across geometries, rendering the rational design and improvement difficult. To address this, we studied three representative joint shapes—trapezoid, circle, and ellipse. Finite element analysis (FEA) was employed to evaluate their tensile performance within the elastic regime. The elliptical joint showed the highest stiffness, while the circular joint exhibited the greatest load capability and resilience. Joint performance was also influenced by friction coefficient, yield strength, and blade number. Applying edge constraints notably enhanced performance, especially for single-blade joints, with up to 7.6 × increase in load capability and 5.4 × in resilience for circular joints, and 11.2 × in stiffness for trapezoidal joints. An Ashby-type plot was developed to support the comparative selection of joint designs. These results provide a foundation for establishing standardized evaluation criteria for tensile joint performance.</div></div>","PeriodicalId":11763,"journal":{"name":"Engineering Structures","volume":"353 ","pages":"Article 122339"},"PeriodicalIF":6.4,"publicationDate":"2026-02-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146154152","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-02-12DOI: 10.1016/j.engstruct.2026.122289
Rafał Walczak , Wit Derkowski
This study examines the structural behaviour of aged prefabricated post-tensioned concrete beams subjected to simulated anchorage failure - an essential aspect in assessing mid-20th-century industrial structures. Full-scale crane girders, in service for over 50 years, were tested to replicate emergency scenarios involving partial loss of tendon anchorages. The investigation addressed various anchorage failure configurations, grout quality levels, shear span-to-depth ratios (a/d), and the impact of low transverse reinforcement. Results showed that even in severe cases - such as loss of both bottom anchorages and insufficient tendon grouting - the beams did not exhibit brittle behaviour. Clear warning symptoms like large deflections and visible cracking preceded failure, although the capacity dropped by up to 50 %. In contrast, the failure of top tendon anchorage had a negligible impact on load-bearing capacity. Beams with low shear slenderness demonstrated higher ultimate strength, typically failing through concrete crushing, while more slender beams followed beam-type failure modes. However, anchorage failures may result in a distinct failure mode of the member. Numerical simulations using DIANA FEA, validated against the test results, extended the analysis to additional damage scenarios. Notably, simulation of the failure of all four bottom anchorages, out of five tendons in the beam, indicated that the beam could sustain load only until initial cracking, after which brittle failure occurred - identifying a critical threshold for safety evaluations. Despite limited stirrup reinforcement, all beams demonstrated sufficient shear performance. These findings contribute valuable insight into the structural assessment and sustainable long-term use or reuse of ageing post-tensioned elements, supporting more informed and sustainable infrastructure decisions.
{"title":"When anchorage fails: Assessing old post-tensioned precast beams in service","authors":"Rafał Walczak , Wit Derkowski","doi":"10.1016/j.engstruct.2026.122289","DOIUrl":"10.1016/j.engstruct.2026.122289","url":null,"abstract":"<div><div>This study examines the structural behaviour of aged prefabricated post-tensioned concrete beams subjected to simulated anchorage failure - an essential aspect in assessing mid-20th-century industrial structures. Full-scale crane girders, in service for over 50 years, were tested to replicate emergency scenarios involving partial loss of tendon anchorages. The investigation addressed various anchorage failure configurations, grout quality levels, shear span-to-depth ratios (a/d), and the impact of low transverse reinforcement. Results showed that even in severe cases - such as loss of both bottom anchorages and insufficient tendon grouting - the beams did not exhibit brittle behaviour. Clear warning symptoms like large deflections and visible cracking preceded failure, although the capacity dropped by up to 50 %. In contrast, the failure of top tendon anchorage had a negligible impact on load-bearing capacity. Beams with low shear slenderness demonstrated higher ultimate strength, typically failing through concrete crushing, while more slender beams followed beam-type failure modes. However, anchorage failures may result in a distinct failure mode of the member. Numerical simulations using DIANA FEA, validated against the test results, extended the analysis to additional damage scenarios. Notably, simulation of the failure of all four bottom anchorages, out of five tendons in the beam, indicated that the beam could sustain load only until initial cracking, after which brittle failure occurred - identifying a critical threshold for safety evaluations. Despite limited stirrup reinforcement, all beams demonstrated sufficient shear performance. These findings contribute valuable insight into the structural assessment and sustainable long-term use or reuse of ageing post-tensioned elements, supporting more informed and sustainable infrastructure decisions.</div></div>","PeriodicalId":11763,"journal":{"name":"Engineering Structures","volume":"353 ","pages":"Article 122289"},"PeriodicalIF":6.4,"publicationDate":"2026-02-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146154155","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-02-12DOI: 10.1016/j.engstruct.2026.122337
Congjie Shang , Yulong Bao , Huazi Li , Yongle Li
With the continuous evolution of bridge deck configurations, certain sections exhibit highly nonlinear damping ratios under still air conditions and demonstrate novel nonlinear flutter behaviors in uniform flow. Identifying these nonlinear parameters using conventional Hilbert transform and polynomial fitting methods has proven exceptionally challenging. This work investigates the separated double composite girder section as a representative case, where nonlinear frequencies and damping ratios of the sectional model are systematically identified. An improved method for identification and fitting of nonlinear damping ratios including energy-based method and piecewise reduced-order fitting method are subsequently developed and thoroughly validated. Two critical technical challenges are successfully resolved: constrained piecewise fitting and optimal breakpoint determination through a weighted coefficient of determination. Finally, the nonlinear flutter characteristics of the model are analyzed from the perspectives of steady-state amplitude, limit-cycle oscillation behavior, and model damping ratio through wind tunnel test. Results demonstrate that the proposed methodology achieves superior identification accuracy compared to conventional techniques, with reproduced vibration response curves showing remarkable consistency with test results. The girder model exhibits distinct nonlinear flutter dominated by torsional vibration, where the steady-state torsional amplitude manifests a stagnation platform within a specific wind speed region. This nonlinear flutter mechanism fundamentally originates from the highly nonlinear behavior of the model damping ratio in the vicinity of the stagnation platform.
{"title":"Experimental investigation on nonlinear flutter characteristics of a separated double composite girder","authors":"Congjie Shang , Yulong Bao , Huazi Li , Yongle Li","doi":"10.1016/j.engstruct.2026.122337","DOIUrl":"10.1016/j.engstruct.2026.122337","url":null,"abstract":"<div><div>With the continuous evolution of bridge deck configurations, certain sections exhibit highly nonlinear damping ratios under still air conditions and demonstrate novel nonlinear flutter behaviors in uniform flow. Identifying these nonlinear parameters using conventional Hilbert transform and polynomial fitting methods has proven exceptionally challenging. This work investigates the separated double composite girder section as a representative case, where nonlinear frequencies and damping ratios of the sectional model are systematically identified. An improved method for identification and fitting of nonlinear damping ratios including energy-based method and piecewise reduced-order fitting method are subsequently developed and thoroughly validated. Two critical technical challenges are successfully resolved: constrained piecewise fitting and optimal breakpoint determination through a weighted coefficient of determination. Finally, the nonlinear flutter characteristics of the model are analyzed from the perspectives of steady-state amplitude, limit-cycle oscillation behavior, and model damping ratio through wind tunnel test. Results demonstrate that the proposed methodology achieves superior identification accuracy compared to conventional techniques, with reproduced vibration response curves showing remarkable consistency with test results. The girder model exhibits distinct nonlinear flutter dominated by torsional vibration, where the steady-state torsional amplitude manifests a stagnation platform within a specific wind speed region. This nonlinear flutter mechanism fundamentally originates from the highly nonlinear behavior of the model damping ratio in the vicinity of the stagnation platform.</div></div>","PeriodicalId":11763,"journal":{"name":"Engineering Structures","volume":"353 ","pages":"Article 122337"},"PeriodicalIF":6.4,"publicationDate":"2026-02-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146170803","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-02-12DOI: 10.1016/j.engstruct.2026.122322
Kun Lin , Yixiao Chen , Annan Zhou , Hongjun Liu
Suction caissons are promising foundations for offshore wind turbines in shallow coastal regions. To investigate dynamic performance of suction caisson supported offshore wind turbines under various operational conditions, a series of wind tunnel tests were conducted on a scaled model based on the NREL 5 MW wind turbine. The model was designed and fabricated in accordance with similitude principles and installed in saturated sand using suction installation methods. Eleven scenarios were analyzed, ranging from cut-in to cut-out wind speed, with pitch adjustment failure taken into account. The dynamic responses, including nacelle displacement, tower-top acceleration, tower-bottom bending moment, and earth pressure variations, were evaluated and compared under different conditions. The results revealed that increasing wind speed reduces the natural frequency while increasing the damping ratio. When approaching failure, the ground support conditions become notably unstable, as evidenced by significant fluctuations in earth pressure behind the suction caisson and in the tower-bottom bending moment. The unstable ground support conditions amplify variations in both the natural frequency and the damping ratio. Several regression equations were developed to estimate rotation angle of foundation, natural frequency, and global damping ratio enabling better practical design of suction caisson supported offshore wind turbines.
{"title":"Dynamic performance of suction caisson supported offshore wind turbines under different operational conditions","authors":"Kun Lin , Yixiao Chen , Annan Zhou , Hongjun Liu","doi":"10.1016/j.engstruct.2026.122322","DOIUrl":"10.1016/j.engstruct.2026.122322","url":null,"abstract":"<div><div>Suction caissons are promising foundations for offshore wind turbines in shallow coastal regions. To investigate dynamic performance of suction caisson supported offshore wind turbines under various operational conditions, a series of wind tunnel tests were conducted on a scaled model based on the NREL 5 MW wind turbine. The model was designed and fabricated in accordance with similitude principles and installed in saturated sand using suction installation methods. Eleven scenarios were analyzed, ranging from cut-in to cut-out wind speed, with pitch adjustment failure taken into account. The dynamic responses, including nacelle displacement, tower-top acceleration, tower-bottom bending moment, and earth pressure variations, were evaluated and compared under different conditions. The results revealed that increasing wind speed reduces the natural frequency while increasing the damping ratio. When approaching failure, the ground support conditions become notably unstable, as evidenced by significant fluctuations in earth pressure behind the suction caisson and in the tower-bottom bending moment. The unstable ground support conditions amplify variations in both the natural frequency and the damping ratio. Several regression equations were developed to estimate rotation angle of foundation, natural frequency, and global damping ratio enabling better practical design of suction caisson supported offshore wind turbines.</div></div>","PeriodicalId":11763,"journal":{"name":"Engineering Structures","volume":"353 ","pages":"Article 122322"},"PeriodicalIF":6.4,"publicationDate":"2026-02-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146170746","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-02-12DOI: 10.1016/j.engstruct.2026.122348
Matteo Mazzeo , Giuseppe Muscolino , Giuseppe Ricciardi
In the field of structural and seismic engineering, the use of viscoelastic (VE) dampers has emerged as a pivotal approach to enhance the energy dissipation capability of civil structures subjected to dynamic loading, particularly seismic excitations. However, accurately capturing the viscoelastic behavior of these dampers, characterized by memory effects, broad relaxation spectra, and frequency-dependent responses, poses significant modeling challenges. Classical integer-order rheological models often fail to effectively represent these complex behaviors, prompting the exploration and utilization of fractional derivative models (FDMs).
This study introduces a straightforward and effective methodology for identifying the parameters of the most widely used fractional viscoelastic models, specifically the fractional Maxwell (F-M), fractional Kelvin Voigt (F-KV), and their generalizations, fractional Zener-Maxwell (F-ZM), and fractional Zener-Kelvin Voigt (F-ZKV) models. The proposed method leverages the characteristic Cole–Cole arc-shaped trajectory in the complex stiffness and compliance planes, allowing parameter calibration based on standard experimental data without the need for sophisticated numerical optimization procedures or specialized software.
Empirical validation, conducted through both artificially generated datasets with controlled perturbations and real experimental data available in the literature, demonstrates the method’s efficacy in accurately capturing the dynamic stiffness and compliance behavior of viscoelastic dampers. The results confirm excellent agreement between the responses identified in the model and the experimental observations, including hysteresis loops and dissipated energy per cycle, with limited discrepancies. Thus, the proposed method significantly simplifies the identification of the dynamic behavior of viscoelastic devices when using fractional models, achieving a nice accuracy compared to the experimental evidence and a simple implementation of advanced theoretical formulations.
{"title":"Identification of the parameters of the simplest fractional models to characterize the viscoelastic behavior of some anti-seismic devices","authors":"Matteo Mazzeo , Giuseppe Muscolino , Giuseppe Ricciardi","doi":"10.1016/j.engstruct.2026.122348","DOIUrl":"10.1016/j.engstruct.2026.122348","url":null,"abstract":"<div><div>In the field of structural and seismic engineering, the use of viscoelastic (VE) dampers has emerged as a pivotal approach to enhance the energy dissipation capability of civil structures subjected to dynamic loading, particularly seismic excitations. However, accurately capturing the viscoelastic behavior of these dampers, characterized by memory effects, broad relaxation spectra, and frequency-dependent responses, poses significant modeling challenges. Classical integer-order rheological models often fail to effectively represent these complex behaviors, prompting the exploration and utilization of fractional derivative models (FDMs).</div><div>This study introduces a straightforward and effective methodology for identifying the parameters of the most widely used fractional viscoelastic models, specifically the fractional Maxwell (F-M), fractional Kelvin Voigt (F-KV), and their generalizations, fractional Zener-Maxwell (F-ZM), and fractional Zener-Kelvin Voigt (F-ZKV) models. The proposed method leverages the characteristic Cole–Cole arc-shaped trajectory in the complex stiffness and compliance planes, allowing parameter calibration based on standard experimental data without the need for sophisticated numerical optimization procedures or specialized software.</div><div>Empirical validation, conducted through both artificially generated datasets with controlled perturbations and real experimental data available in the literature, demonstrates the method’s efficacy in accurately capturing the dynamic stiffness and compliance behavior of viscoelastic dampers. The results confirm excellent agreement between the responses identified in the model and the experimental observations, including hysteresis loops and dissipated energy per cycle, with limited discrepancies. Thus, the proposed method significantly simplifies the identification of the dynamic behavior of viscoelastic devices when using fractional models, achieving a nice accuracy compared to the experimental evidence and a simple implementation of advanced theoretical formulations.</div></div>","PeriodicalId":11763,"journal":{"name":"Engineering Structures","volume":"353 ","pages":"Article 122348"},"PeriodicalIF":6.4,"publicationDate":"2026-02-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146170743","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-02-11DOI: 10.1016/j.engstruct.2026.122345
Delbaz Samadian, Annalisa Occhipinti, Imrose B. Muhit, Nashwan Dawood
Accurately assessing the vulnerability of critical building portfolios is fundamental for regional risk management and decision support, especially in regions facing sequential earthquake–flood events exacerbated by climate change. Such compound disasters pose severe environmental challenges, yet current practice lacks reliable surrogate models to rapidly predict structural response and damage-relevant demand parameters under combined seismic and flood loading. This study addresses that gap by introducing a soft computing approach, the Stacked Attention-based Long Short-Term Memory network (Stack-AttenLSTM), to efficiently predict key structural response quantities under sequential earthquake–flood hazards. In this framework, structural vulnerability is interpreted in a performance-based sense, whereby hazard-induced response metrics serve as proxies for damage susceptibility rather than direct loss estimation. The surrogate model predicts key engineering demand parameters (EDPs), including the maximum inter-storey drift ratio (MIDR), maximum floor acceleration (MFA), and maximum base shear (MBS), which are widely used indicators of structural damage and vulnerability. To develop this model, a large-scale meta-database comprising 30,000 steel special moment-resisting frame (SMRF) buildings is first generated to capture structural variability across low-, mid-, and high-rise typologies, from which a representative subset is selected for detailed high-fidelity three-dimensional (3D) nonlinear time-history analyses (NLTHA) under sequential earthquake–flood loading and surrogate model training. Flood loading is represented using computational fluid dynamics (CFD) simulations with a dam-break–type inflow condition, employed as a conservative hydrodynamic proxy to study flow-induced forces under extreme inundation scenarios. Multiple Stack-AttenLSTM architectures are trained and evaluated, and the final model is selected for its optimal balance of predictive accuracy and computational efficiency, enabling rapid yet reliable response prediction. The proposed model achieves high predictive accuracy, with coefficients of determination (R²) approaching 0.88 and low error metrics across all hazard scenarios, demonstrating its effectiveness for rapid multi-hazard vulnerability assessment. Although explicit fragility or loss models are not derived, the Stack-AttenLSTM framework is suitable for integration with early warning systems and digital twin platforms, enabling real-time monitoring, improved uncertainty management, and proactive disaster response.
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