Pub Date : 2026-02-07DOI: 10.1016/j.istruc.2026.111309
Xiang-Dong Cai , Wang-Xi Zhang , Shun-Tao Li , Yi-Bo Zhou , Jin-Yi Zhang , Wei-Jian Yi
Seismic design of reinforced concrete frame structures aims to achieve a beam hinge mechanism; however, this ideal behavior is inevitably disturbed by floor slab participation and base embedment performance. This study investigates the effects of slab strengthening and base embedment performance on the seismic response and global yielding mechanism of RC frame substructures. An experimental program combined with parametric finite element analyses is conducted, considering variations in slab reinforcement ratio, slab thickness, slab concrete strength, base reinforcement ratio, base height, and base concrete strength. The results indicate that slab-related parameters dominate the transition of the yielding mechanism by promoting column yielding and suppressing beam hinge formation, whereas base reinforcement ratio and base concrete strength exert limited influence. Base height significantly affects structural strength, deformation capacity, and the distribution of column hinges. Based on these findings, a quantitative, mechanism-based evaluation framework is proposed using dimensionless indicators derived from global- and story-level column hinge ratios to define an acceptable partial beam hinge-column hinge mechanism. The proposed framework provides a practical diagnostic tool for assessing whether the plastic mechanism obtained from nonlinear analysis is compatible with seismic design objectives.
{"title":"Seismic behavior of reinforced concrete frame substructure considering floor slab strengthening and base embedment performance","authors":"Xiang-Dong Cai , Wang-Xi Zhang , Shun-Tao Li , Yi-Bo Zhou , Jin-Yi Zhang , Wei-Jian Yi","doi":"10.1016/j.istruc.2026.111309","DOIUrl":"10.1016/j.istruc.2026.111309","url":null,"abstract":"<div><div>Seismic design of reinforced concrete frame structures aims to achieve a beam hinge mechanism; however, this ideal behavior is inevitably disturbed by floor slab participation and base embedment performance. This study investigates the effects of slab strengthening and base embedment performance on the seismic response and global yielding mechanism of RC frame substructures. An experimental program combined with parametric finite element analyses is conducted, considering variations in slab reinforcement ratio, slab thickness, slab concrete strength, base reinforcement ratio, base height, and base concrete strength. The results indicate that slab-related parameters dominate the transition of the yielding mechanism by promoting column yielding and suppressing beam hinge formation, whereas base reinforcement ratio and base concrete strength exert limited influence. Base height significantly affects structural strength, deformation capacity, and the distribution of column hinges. Based on these findings, a quantitative, mechanism-based evaluation framework is proposed using dimensionless indicators derived from global- and story-level column hinge ratios to define an acceptable partial beam hinge-column hinge mechanism. The proposed framework provides a practical diagnostic tool for assessing whether the plastic mechanism obtained from nonlinear analysis is compatible with seismic design objectives.</div></div>","PeriodicalId":48642,"journal":{"name":"Structures","volume":"86 ","pages":"Article 111309"},"PeriodicalIF":4.3,"publicationDate":"2026-02-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146192320","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 : 2026-02-07DOI: 10.1016/j.istruc.2026.111313
Zehong Yang , Yongjian Liu , Yinping Ma , Lei Jiang , Wenxiang Wu , Yu Deng , Yunqiang Qiao
The ultra-high-performance concrete (UHPC) was employed to enhance the flexural behavior of concrete filled steel tubular (CFST) composite truss girder. To fully exploit the compressive advantages of UHPC, numerical simulating method of UHPC-enhanced CFST Composite Truss Girder (UCCTG) was performed and validated against the existing experiments. Results demonstrated that the UCCTG exhibited significantly enhanced flexural stiffness and strength through the incorporation of a UHPC slab, while the improvement of filling the concrete in both top and bottom chords was limited. The thickness can reduce approximately 50 % by applying UHPC slab compared to the conventional concrete slab while maintaining comparable flexural strength. The enhancement mechanism of UHPC slab on UCCTG was investigated under different failure modes: (i) for bottom chord failure, the higher strength of UHPC slab resulted in bottom chord stresses closer to the ultimate strength of the steel with higher material efficiency; (ii) for composite top chord failure, the CFST chord failed before the UHPC slab due to its high compressive strength; (iii) after brace failure, the UCCTG sustained additional load capacity through local bending of the composite top chord. Flexural strength calculating methods of UCCTG was proposed and validated against the finite element results. Design recommendations were provided to ensure structural and economic advantages.
{"title":"Flexural behavior of UHPC-enhanced concrete filled steel tubular composite truss girders","authors":"Zehong Yang , Yongjian Liu , Yinping Ma , Lei Jiang , Wenxiang Wu , Yu Deng , Yunqiang Qiao","doi":"10.1016/j.istruc.2026.111313","DOIUrl":"10.1016/j.istruc.2026.111313","url":null,"abstract":"<div><div>The ultra-high-performance concrete (UHPC) was employed to enhance the flexural behavior of concrete filled steel tubular (CFST) composite truss girder. To fully exploit the compressive advantages of UHPC, numerical simulating method of UHPC-enhanced CFST Composite Truss Girder (UCCTG) was performed and validated against the existing experiments. Results demonstrated that the UCCTG exhibited significantly enhanced flexural stiffness and strength through the incorporation of a UHPC slab, while the improvement of filling the concrete in both top and bottom chords was limited. The thickness can reduce approximately 50 % by applying UHPC slab compared to the conventional concrete slab while maintaining comparable flexural strength. The enhancement mechanism of UHPC slab on UCCTG was investigated under different failure modes: (i) for bottom chord failure, the higher strength of UHPC slab resulted in bottom chord stresses closer to the ultimate strength of the steel with higher material efficiency; (ii) for composite top chord failure, the CFST chord failed before the UHPC slab due to its high compressive strength; (iii) after brace failure, the UCCTG sustained additional load capacity through local bending of the composite top chord. Flexural strength calculating methods of UCCTG was proposed and validated against the finite element results. Design recommendations were provided to ensure structural and economic advantages.</div></div>","PeriodicalId":48642,"journal":{"name":"Structures","volume":"86 ","pages":"Article 111313"},"PeriodicalIF":4.3,"publicationDate":"2026-02-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146192367","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 : 2026-02-07DOI: 10.1016/j.istruc.2026.111304
Francesco Esposito, Fabrizio Ascione, Diana Faiella, Elena Mele
The reuse of structural steel is gaining increasing attention due to its sustainability benefits and the inherent durability of the material. However, this practice requires a reversal of the conventional design process, as the structural elements are defined a priori. Moreover, in Italy, a large portion of the existing reinforced concrete (RC) buildings constructed between the 1960s and 1980s exhibits high seismic vulnerability, making seismic retrofitting interventions necessary. This research aims to address both issues by applying steel reuse to the seismic retrofit of existing RC structures through the adoption of external diagrid-type systems incorporating reused steel elements. A Python-based algorithm is developed and implemented within a workflow created in the Rhino/Grasshopper environment and managed through a genetic algorithm. At each step of the optimization process, the diagrid structure—whose design variables correspond to nodal coordinates—is initially generated using new steel elements, which are subsequently replaced, with reused elements while satisfying structural and geometric constraints. In Italy, most steel suitable for reuse originates from industrial buildings or electrical transmission towers and mainly consists of L-shaped sections. For this reason, the algorithm includes the capability to manage such profiles by coupling them in pairs or in groups of four, enabling a broader range of section configurations. This approach increases the probability of achieving an optimal match between reused and new elements. The proposed methodology enables the exploitation of Italian steel reuse datasets and provides a framework for extending the service life of both steel components and existing RC structures.
{"title":"Stock-constrained optimization of diagrid exoskeletons using reclaimed steel for seismic retrofit of RC buildings","authors":"Francesco Esposito, Fabrizio Ascione, Diana Faiella, Elena Mele","doi":"10.1016/j.istruc.2026.111304","DOIUrl":"10.1016/j.istruc.2026.111304","url":null,"abstract":"<div><div>The reuse of structural steel is gaining increasing attention due to its sustainability benefits and the inherent durability of the material. However, this practice requires a reversal of the conventional design process, as the structural elements are defined a priori. Moreover, in Italy, a large portion of the existing reinforced concrete (RC) buildings constructed between the 1960s and 1980s exhibits high seismic vulnerability, making seismic retrofitting interventions necessary. This research aims to address both issues by applying steel reuse to the seismic retrofit of existing RC structures through the adoption of external diagrid-type systems incorporating reused steel elements. A Python-based algorithm is developed and implemented within a workflow created in the Rhino/Grasshopper environment and managed through a genetic algorithm. At each step of the optimization process, the diagrid structure—whose design variables correspond to nodal coordinates—is initially generated using new steel elements, which are subsequently replaced, with reused elements while satisfying structural and geometric constraints. In Italy, most steel suitable for reuse originates from industrial buildings or electrical transmission towers and mainly consists of <span>L</span>-shaped sections. For this reason, the algorithm includes the capability to manage such profiles by coupling them in pairs or in groups of four, enabling a broader range of section configurations. This approach increases the probability of achieving an optimal match between reused and new elements. The proposed methodology enables the exploitation of Italian steel reuse datasets and provides a framework for extending the service life of both steel components and existing RC structures.</div></div>","PeriodicalId":48642,"journal":{"name":"Structures","volume":"86 ","pages":"Article 111304"},"PeriodicalIF":4.3,"publicationDate":"2026-02-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146191403","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 : 2026-02-07DOI: 10.1016/j.istruc.2026.111316
Weidong He , Peng Liu , Xingyu Peng , Cheng Chen , Zhen Sun , Yalin Li , Yongbo Shao
Composite profiles have gained increasing applications in civil engineering and materials science due to their superior mechanical properties, yet optimizing joint connection performance remains a critical technical challenge. This study investigates the static and low-cycle cyclic loading responses of basalt fiber reinforced polymer (BFRP) square tube joint with different axial fiber layups, as well as hybrid carbon/basalt fiber tubes, under varying numbers of bolted connections. The effects of fiber axial orientation and hybrid lay-up configurations on load-bearing capacity, stiffness degradation patterns, and energy dissipation performance were systematically analyzed for both single-bolt and six-bolt connection joints. Results indicate that compared to basalt fiber square tubes with uniform axial lay-up, multi-axial fiber lay-up structures demonstrate significantly enhanced mechanical performance under both static and cyclic loading. Especially, under static loading conditions, the multi-axial lay-up increased joint load capacity by over 50 %. Under cyclic loading, the maximum energy dissipation capacities of single-bolt and six-bolt connections with multi-axial lay-up reached 2.5 times and 5.2 times those of uniformly axial lay-up tubes joint respectively. Besides, in the six-bolt connection joints, the carbon fiber layers in the hybrid lay-up configuration fully exploit their tensile properties, demonstrating superior load-bearing capacity and energy dissipation performance compared to other structures.
{"title":"Experimental performance of bolted BFRP square profile joints under quasi-static and cyclic loads","authors":"Weidong He , Peng Liu , Xingyu Peng , Cheng Chen , Zhen Sun , Yalin Li , Yongbo Shao","doi":"10.1016/j.istruc.2026.111316","DOIUrl":"10.1016/j.istruc.2026.111316","url":null,"abstract":"<div><div>Composite profiles have gained increasing applications in civil engineering and materials science due to their superior mechanical properties, yet optimizing joint connection performance remains a critical technical challenge. This study investigates the static and low-cycle cyclic loading responses of basalt fiber reinforced polymer (BFRP) square tube joint with different axial fiber layups, as well as hybrid carbon/basalt fiber tubes, under varying numbers of bolted connections. The effects of fiber axial orientation and hybrid lay-up configurations on load-bearing capacity, stiffness degradation patterns, and energy dissipation performance were systematically analyzed for both single-bolt and six-bolt connection joints. Results indicate that compared to basalt fiber square tubes with uniform axial lay-up, multi-axial fiber lay-up structures demonstrate significantly enhanced mechanical performance under both static and cyclic loading. Especially, under static loading conditions, the multi-axial lay-up increased joint load capacity by over 50 %. Under cyclic loading, the maximum energy dissipation capacities of single-bolt and six-bolt connections with multi-axial lay-up reached 2.5 times and 5.2 times those of uniformly axial lay-up tubes joint respectively. Besides, in the six-bolt connection joints, the carbon fiber layers in the hybrid lay-up configuration fully exploit their tensile properties, demonstrating superior load-bearing capacity and energy dissipation performance compared to other structures.</div></div>","PeriodicalId":48642,"journal":{"name":"Structures","volume":"86 ","pages":"Article 111316"},"PeriodicalIF":4.3,"publicationDate":"2026-02-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146192321","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 : 2026-02-06DOI: 10.1016/j.istruc.2026.111311
Mahdi Yazdani, René Panian
Masonry arch bridges, as critical components of railway infrastructure, are widely scattered throughout the Iranian railway network. Although most of these bridges have been in service for over ninety years, they continue to perform safely while being subjected to increasing traffic demands in recent years. Existing assessment methods mainly focus on ultimate load capacity and do not explicitly address fatigue damage or remaining service life under repeated train loading. Unlike conventional capacity-based approaches, this study presents a fracture-mechanics-based framework that explicitly accounts for fatigue crack growth, enabling quantitative prediction of the remaining service life of masonry arch bridges, which has rarely been addressed in existing numerical studies. A detailed finite element model was developed in ANSYS and calibrated using crack mouth opening displacement (CMOD) measurements obtained from field observations. Fatigue crack propagation was considered by Paris’ law, enabling the relationship between crack length, stress intensity factor (SIF), and number of load cycles to be quantified under realistic traffic scenarios. The results show that for an axle load of 20 ton and 15 train passages per day, the estimated fatigue life of the bridge is approximately 125 years, which decreases to about 94 years when the axle load increases to 25 ton. Based on the critical load position at one-quarter of the main span, a fatigue limit of approximately 0.27 was identified. The proposed methodology extends conventional assessment practices by integrating fracture-mechanics-based fatigue analysis into numerical modeling, providing a practical and service-life-oriented tool for predicting fatigue life and supporting informed decision-making in the structural management of historic railway masonry arch bridges.
{"title":"Fatigue life assessment of multi-span railway masonry arch bridges based on crack growth rate","authors":"Mahdi Yazdani, René Panian","doi":"10.1016/j.istruc.2026.111311","DOIUrl":"10.1016/j.istruc.2026.111311","url":null,"abstract":"<div><div>Masonry arch bridges, as critical components of railway infrastructure, are widely scattered throughout the Iranian railway network. Although most of these bridges have been in service for over ninety years, they continue to perform safely while being subjected to increasing traffic demands in recent years. Existing assessment methods mainly focus on ultimate load capacity and do not explicitly address fatigue damage or remaining service life under repeated train loading. Unlike conventional capacity-based approaches, this study presents a fracture-mechanics-based framework that explicitly accounts for fatigue crack growth, enabling quantitative prediction of the remaining service life of masonry arch bridges, which has rarely been addressed in existing numerical studies. A detailed finite element model was developed in ANSYS and calibrated using crack mouth opening displacement (CMOD) measurements obtained from field observations. Fatigue crack propagation was considered by Paris’ law, enabling the relationship between crack length, stress intensity factor (SIF), and number of load cycles to be quantified under realistic traffic scenarios. The results show that for an axle load of 20 ton and 15 train passages per day, the estimated fatigue life of the bridge is approximately 125 years, which decreases to about 94 years when the axle load increases to 25 ton. Based on the critical load position at one-quarter of the main span, a fatigue limit of approximately 0.27 was identified. The proposed methodology extends conventional assessment practices by integrating fracture-mechanics-based fatigue analysis into numerical modeling, providing a practical and service-life-oriented tool for predicting fatigue life and supporting informed decision-making in the structural management of historic railway masonry arch bridges.</div></div>","PeriodicalId":48642,"journal":{"name":"Structures","volume":"86 ","pages":"Article 111311"},"PeriodicalIF":4.3,"publicationDate":"2026-02-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146192526","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 : 2026-02-06DOI: 10.1016/j.istruc.2026.111228
Fabián Consuegra
Soil-Structure Interaction (SSI) effects may become significant for buildings situated on soft soil when coupled with specific foundation and superstructure flexibility characteristics. Under service conditions, traffic-induced waves can cause vibrations perceptible to building occupants, even when the structure fully complies with a conventional strength-based building standard. This investigation was based on records of a six-story building. Soil foundation was modeled through a semi-infinite elastic media representation. A calibrated model achieved estimations within an 8 % difference from actual field records. The results demonstrate that SSI induces a reduction of up to 40 % in the system’s lateral stiffness during its service state at overall drift ratios of about 0.0002 %. In contrast to research approaches focused primarily on inelastic behavior for seismic applications, this study presents a methodology to identify the presence of SSI, by tracking the frequency of an equivalent nonlinear-elastic model. This variation occurs as base movement activates foundation flexibility, leading to the coexistence of two distinct fundamental frequencies. The identification is achieved through a 2-DOF representation and it involves (a) analyzing the frequency content of ambient vibrations recorded with high-sensitivity instrumentation; (b) tracking the fundamental frequency as a function of displacement; (c) establishing a linear transfer function (TF) to isolate the effects of soil flexibility; and (d) comparing estimated forces applied at each DOF to localize the source of energy input. The method was successfully implemented to characterize the most probable scenario causing user-perceived vibrations. Despite its efficacy, the applicability of this approach may be limited in cases with low signal-to-noise ratios or highly rigid superstructures that preclude the coexistence of the fixed-base and SSI-influenced frequencies.
{"title":"Identification of soil-structure interaction as the primary source of traffic-induced vibrations in a low-rise building: A nonlinear-elastic perspective","authors":"Fabián Consuegra","doi":"10.1016/j.istruc.2026.111228","DOIUrl":"10.1016/j.istruc.2026.111228","url":null,"abstract":"<div><div>Soil-Structure Interaction (SSI) effects may become significant for buildings situated on soft soil when coupled with specific foundation and superstructure flexibility characteristics. Under service conditions, traffic-induced waves can cause vibrations perceptible to building occupants, even when the structure fully complies with a conventional strength-based building standard. This investigation was based on records of a six-story building. Soil foundation was modeled through a semi-infinite elastic media representation. A calibrated model achieved estimations within an 8 % difference from actual field records. The results demonstrate that SSI induces a reduction of up to 40 % in the system’s lateral stiffness during its service state at overall drift ratios of about 0.0002 %. In contrast to research approaches focused primarily on inelastic behavior for seismic applications, this study presents a methodology to identify the presence of SSI, by tracking the frequency of an equivalent nonlinear-elastic model. This variation occurs as base movement activates foundation flexibility, leading to the coexistence of two distinct fundamental frequencies. The identification is achieved through a 2-DOF representation and it involves (a) analyzing the frequency content of ambient vibrations recorded with high-sensitivity instrumentation; (b) tracking the fundamental frequency as a function of displacement; (c) establishing a linear transfer function (TF) to isolate the effects of soil flexibility; and (d) comparing estimated forces applied at each DOF to localize the source of energy input. The method was successfully implemented to characterize the most probable scenario causing user-perceived vibrations. Despite its efficacy, the applicability of this approach may be limited in cases with low signal-to-noise ratios or highly rigid superstructures that preclude the coexistence of the fixed-base and SSI-influenced frequencies.</div></div>","PeriodicalId":48642,"journal":{"name":"Structures","volume":"86 ","pages":"Article 111228"},"PeriodicalIF":4.3,"publicationDate":"2026-02-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146192527","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 : 2026-02-06DOI: 10.1016/j.istruc.2026.111254
Yuliang Cai, Zixin Chen, Fei Wang, Zhuo Zhao, Zhongda Lyu, Lei Wang, Xinkai Yan
Due to the combined effects of hydration heat, drying shrinkage, autogenous shrinkage, and external environmental conditions, large precast box girders are highly susceptible to early-age cracking, which can severely compromise the durability and service life of bridges. Research on early-age cracking of box girders remains limited, with most existing studies focusing predominantly on thermal stress while neglecting the effects of early-age shrinkage, which hinders the accurate analysis of crack causes and the development of effective prevention strategies. In this study, a computational approach was developed to simulate the coupled thermal, hygral, and mechanical behavior of large precast concrete box girders at an early age, integrating full-scale testing and numerical modeling. The evolution patterns of temperature, moisture content, strain development, and cracking risk during the early stages were systematically analyzed in detail. Research indicates that by incorporating the equivalent age of concrete and fully considering the spatiotemporal evolution of concrete material parameters, the early-age temperature field of box girders can be accurately simulated. The highest measured temperature reached 74.8℃, occurring at the center of the web at the end section. The maximum difference between simulated and measured peak temperatures was 3.78 %. At 100 h, the surface humidity of the box girder at the end and mid-span sections was recorded as 95.1 % and 93.2 %, respectively. The thinner the cross-sectional thickness of the girder, the more significant the decrease in surface humidity. Moreover, the early humidity gradient in box girders is mainly concentrated within a depth of 10 cm to 15 cm beneath the inner surface. The mid-span standard section of the girder exhibits a relatively high risk of cracking; the cracking risks at the top-web junction at the quarter and mid-span sections at 100 h are recorded as 1.28 and 1.23, respectively. The simulated cracking time as well as the high-risk cracking zones showed strong agreement with the experimental observations. Further analysis indicated that implementing internal moisture-curing measures in box girders can reduce the early-age stress at the junction of the top slab and web at the midspan section by 0.43 MPa, thereby decreasing the risk of early-age cracking by 16 %.
{"title":"Early cracking risk analysis of large precast box girders based on thermo-hygro-mechanical coupling","authors":"Yuliang Cai, Zixin Chen, Fei Wang, Zhuo Zhao, Zhongda Lyu, Lei Wang, Xinkai Yan","doi":"10.1016/j.istruc.2026.111254","DOIUrl":"10.1016/j.istruc.2026.111254","url":null,"abstract":"<div><div>Due to the combined effects of hydration heat, drying shrinkage, autogenous shrinkage, and external environmental conditions, large precast box girders are highly susceptible to early-age cracking, which can severely compromise the durability and service life of bridges. Research on early-age cracking of box girders remains limited, with most existing studies focusing predominantly on thermal stress while neglecting the effects of early-age shrinkage, which hinders the accurate analysis of crack causes and the development of effective prevention strategies. In this study, a computational approach was developed to simulate the coupled thermal, hygral, and mechanical behavior of large precast concrete box girders at an early age, integrating full-scale testing and numerical modeling. The evolution patterns of temperature, moisture content, strain development, and cracking risk during the early stages were systematically analyzed in detail. Research indicates that by incorporating the equivalent age of concrete and fully considering the spatiotemporal evolution of concrete material parameters, the early-age temperature field of box girders can be accurately simulated. The highest measured temperature reached 74.8℃, occurring at the center of the web at the end section. The maximum difference between simulated and measured peak temperatures was 3.78 %. At 100 h, the surface humidity of the box girder at the end and mid-span sections was recorded as 95.1 % and 93.2 %, respectively. The thinner the cross-sectional thickness of the girder, the more significant the decrease in surface humidity. Moreover, the early humidity gradient in box girders is mainly concentrated within a depth of 10 cm to 15 cm beneath the inner surface. The mid-span standard section of the girder exhibits a relatively high risk of cracking; the cracking risks at the top-web junction at the quarter and mid-span sections at 100 h are recorded as 1.28 and 1.23, respectively. The simulated cracking time as well as the high-risk cracking zones showed strong agreement with the experimental observations. Further analysis indicated that implementing internal moisture-curing measures in box girders can reduce the early-age stress at the junction of the top slab and web at the midspan section by 0.43 MPa, thereby decreasing the risk of early-age cracking by 16 %.</div></div>","PeriodicalId":48642,"journal":{"name":"Structures","volume":"86 ","pages":"Article 111254"},"PeriodicalIF":4.3,"publicationDate":"2026-02-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146192573","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 : 2026-02-06DOI: 10.1016/j.istruc.2026.111264
Bo Da , Heng Zhou , Kai Sun , Tao Tao , Zhangyu Wu , Da Chen
To explore compressive performance of high-strength coral aggregate seawater concrete columns (CASCC) with additional anti-corrosion technology, tests and numerical simulation analysis were carried out considering various rebars and eccentricities. Failure mechanisms, deformation characteristics and ultimate bearing capacity (Nu) of CASCC were studied. Furthermore, load-dependent displacement and strain relationships were formulated, and a numerical predictive model for CASCC’s Nu was developed. Analysis indicates stress behavior and failure in CASCC columns are comparable to conventional concrete columns. Considering complex stress state changes of tension-compression-shear during loading, a numerical model suitable for describing the compression properties of CASCC was proposed based on concrete damage plasticity (CDP) theory. The average error between model predictions and experimental data remaining below 6.85 %, which can effectively display full process failure mode of CASCC and variation laws of displacement and strain. In addition, the accuracy of Nu calculated by numerical model is 17.0 % and 18.4 % higher than that of the current specification GB/T 50010–2010 and JGJ/T 12–2019, respectively. Addressing the poor applicability of the current specifications and incorporating the impact of rebar corrosion and interfacial bond-slip degradation on Nu of CASCC, the Nu optimization calculation formula is proposed and verified, and its accuracy is similar to numerical model.
{"title":"Test and simulation research on compressive performance of high-strength CASCC with additional anti-corrosion technology","authors":"Bo Da , Heng Zhou , Kai Sun , Tao Tao , Zhangyu Wu , Da Chen","doi":"10.1016/j.istruc.2026.111264","DOIUrl":"10.1016/j.istruc.2026.111264","url":null,"abstract":"<div><div>To explore compressive performance of high-strength coral aggregate seawater concrete columns (CASCC) with additional anti-corrosion technology, tests and numerical simulation analysis were carried out considering various rebars and eccentricities. Failure mechanisms, deformation characteristics and ultimate bearing capacity (<em>N</em><sub>u</sub>) of CASCC were studied. Furthermore, load-dependent displacement and strain relationships were formulated, and a numerical predictive model for CASCC’s <em>N</em><sub>u</sub> was developed. Analysis indicates stress behavior and failure in CASCC columns are comparable to conventional concrete columns. Considering complex stress state changes of tension-compression-shear during loading, a numerical model suitable for describing the compression properties of CASCC was proposed based on concrete damage plasticity (CDP) theory. The average error between model predictions and experimental data remaining below 6.85 %, which can effectively display full process failure mode of CASCC and variation laws of displacement and strain. In addition, the accuracy of <em>N</em><sub>u</sub> calculated by numerical model is 17.0 % and 18.4 % higher than that of the current specification GB/T 50010–2010 and JGJ/T 12–2019, respectively. Addressing the poor applicability of the current specifications and incorporating the impact of rebar corrosion and interfacial bond-slip degradation on <em>N</em><sub>u</sub> of CASCC, the <em>N</em><sub>u</sub> optimization calculation formula is proposed and verified, and its accuracy is similar to numerical model.</div></div>","PeriodicalId":48642,"journal":{"name":"Structures","volume":"86 ","pages":"Article 111264"},"PeriodicalIF":4.3,"publicationDate":"2026-02-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146192609","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}
In Italy the current seismic design standards for new and existing constructions relies on Uniform-Hazard Approach (UHA), assigning fixed hazard-exceedance probabilities to different Limit States (LSs). However, this approach leads to non-uniform seismic risk, since failure probabilities vary across a territory depending on local seismic hazard conditions. To cover this gap, this study proposes a reliability-based procedure for calibrating the seismic action of constructions, consistent with the probabilistic framework of SAC FEMA and the Risk-Targeted Approach (RTA). In accordance with this procedure, target reliability indexes and the corresponding reliability factors are proposed by referring to the current MPS-04 seismic hazard model. To this scope exceedance probabilities for different LSs and Consequence Classes (CCs) are defined, and the seismic hazard function parameters are optimized in a log–log space. Assuming the annual failure probability of provided by FEMA, average target reliability factors of 2.11 for the Ultimate Limit State (ULS) and 1.0 for the Serviceability Limit State (SLS) are obtained for the Italian territory. Based on these values, mean target reliability indexes are then derived as functions of the LS and CC. The results obtained clearly show that, coherently with the UHA, the Expected Annual Losses (EALs) and reliability indexes vary significantly across Italy, indicating a non-uniform risk distribution. Conversely, the reliability-based procedure achieves uniform seismic risk by introducing a site-specific modification factor to the MPS-04 seismic action. The reliability factors derived according to the proposed design procedure may be readily implemented in the design code to calibrate a seismic action ensuring a uniform seismic risk across the Italian territory.
{"title":"A proposal for the calibration of the Italian seismic action in accordance with a reliability-based design procedure","authors":"Matteo Tatangelo , Lorenzo Audisio , Michele D’Amato , Rosario Gigliotti , Franco Braga","doi":"10.1016/j.istruc.2026.111279","DOIUrl":"10.1016/j.istruc.2026.111279","url":null,"abstract":"<div><div>In Italy the current seismic design standards for new and existing constructions relies on <em>Uniform-Hazard Approach</em> (<em>UHA</em>), assigning fixed hazard-exceedance probabilities to different <em>Limit States</em> (<em>LSs</em>). However, this approach leads to non-uniform seismic risk, since failure probabilities vary across a territory depending on local seismic hazard conditions. To cover this gap, this study proposes a reliability-based procedure for calibrating the seismic action of constructions, consistent with the probabilistic framework of SAC FEMA and the <em>Risk-Targeted Approach</em> (<em>RTA</em>). In accordance with this procedure, target reliability indexes and the corresponding reliability factors are proposed by referring to the current <em>MPS-04</em> seismic hazard model. To this scope exceedance probabilities for different <em>LSs</em> and <em>Consequence Classes</em> (<em>CCs</em>) are defined, and the seismic hazard function parameters are optimized in a log–log space. Assuming the annual failure probability of <span><math><mrow><mn>2</mn><mo>×</mo><msup><mrow><mn>10</mn></mrow><mrow><mo>−</mo><mn>4</mn></mrow></msup></mrow></math></span> provided by FEMA, average target reliability factors of 2.11 for the <em>Ultimate Limit State</em> (<em>ULS</em>) and 1.0 for the <em>Serviceability Limit State</em> (<em>SLS</em>) are obtained for the Italian territory. Based on these values, mean target reliability indexes are then derived as functions of the <em>LS</em> and <em>CC</em>. The results obtained clearly show that, coherently with the <em>UHA</em>, the <em>Expected Annual Losses</em> (<em>EALs</em>) and reliability indexes vary significantly across Italy, indicating a non-uniform risk distribution. Conversely, the reliability-based procedure achieves uniform seismic risk by introducing a site-specific modification factor to the MPS-04 seismic action. The reliability factors derived according to the proposed design procedure may be readily implemented in the design code to calibrate a seismic action ensuring a uniform seismic risk across the Italian territory.</div></div>","PeriodicalId":48642,"journal":{"name":"Structures","volume":"86 ","pages":"Article 111279"},"PeriodicalIF":4.3,"publicationDate":"2026-02-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146192572","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}
Precast concrete (PC) structures have historically faced challenges in seismic regions owing to brittle joint behavior and limited energy dissipation capacity. While recent research has advanced emulative column–footing connections using column shoes, studies on non-emulative precast systems employing energy-dissipating devices remain relatively limited, particularly in terms of experimental validation. Despite the potential benefits of hybrid self-centering systems, experimental validation remains limited. In particular, no studies to date have examined non-emulative column–footing connections that combine unbonded post-tensioning tendons with energy-dissipating bolts. This study outlines the development of an innovative PC column-footing connection that incorporates unbonded prestressed tendons and energy-dissipating bolts within a column shoe connection system. The proposed system is designed to enhance self-centering capability while maintaining the energy dissipation capacity of precast structural systems. Adhering to the capacity design philosophy, the connection is intended to confine damage to the joint region. The experimental program comprised six specimens subjected to quasi-static reversed cyclic loading: a cast-in-place (CIP) specimen, an emulative precast specimen, and four unbonded prestressed column shoe systems (UCS). The UCS series includes a tendon-only configuration (UCS-0) and three variations (UCS-8, UCS-15, and UCS-18) with differing ratios of moment contribution from energy-dissipating bolts relative to the total flexural capacity. The study focused on evaluating damage patterns, lateral load-carrying capacity, stiffness, and energy dissipation for each specimen. Experimental results were benchmarked against design predictions to evaluate the accuracy and reliability of the system. The findings indicate that the proposed connection effectively resisted lateral seismic loading and demonstrated performance comparable with that of conventional CIP systems. Notably, the connection maintained significant strength and stiffness even at drift ratios up to ±4.50 %. Furthermore, the overall performance satisfied the requirements outlined in ACI 374.1–05 for the seismic evaluation of structural systems.
{"title":"Development and experimental study of innovative precast column–footing connections with self-centering and energy-dissipating bolts","authors":"Nitatch Sripongngam, Napatsakorn Wonghiran, Panatouch Thongou, Sirawit Thianthong, Ekkachai Yooprasertchai, Chai Jaturapitakkul","doi":"10.1016/j.istruc.2026.111305","DOIUrl":"10.1016/j.istruc.2026.111305","url":null,"abstract":"<div><div>Precast concrete (PC) structures have historically faced challenges in seismic regions owing to brittle joint behavior and limited energy dissipation capacity. While recent research has advanced emulative column–footing connections using column shoes, studies on non-emulative precast systems employing energy-dissipating devices remain relatively limited, particularly in terms of experimental validation. Despite the potential benefits of hybrid self-centering systems, experimental validation remains limited. In particular, no studies to date have examined non-emulative column–footing connections that combine unbonded post-tensioning tendons with energy-dissipating bolts. This study outlines the development of an innovative PC column-footing connection that incorporates unbonded prestressed tendons and energy-dissipating bolts within a column shoe connection system. The proposed system is designed to enhance self-centering capability while maintaining the energy dissipation capacity of precast structural systems. Adhering to the capacity design philosophy, the connection is intended to confine damage to the joint region. The experimental program comprised six specimens subjected to quasi-static reversed cyclic loading: a cast-in-place (CIP) specimen, an emulative precast specimen, and four unbonded prestressed column shoe systems (UCS). The UCS series includes a tendon-only configuration (UCS-0) and three variations (UCS-8, UCS-15, and UCS-18) with differing ratios of moment contribution from energy-dissipating bolts relative to the total flexural capacity. The study focused on evaluating damage patterns, lateral load-carrying capacity, stiffness, and energy dissipation for each specimen. Experimental results were benchmarked against design predictions to evaluate the accuracy and reliability of the system. The findings indicate that the proposed connection effectively resisted lateral seismic loading and demonstrated performance comparable with that of conventional CIP systems. Notably, the connection maintained significant strength and stiffness even at drift ratios up to ±4.50 %. Furthermore, the overall performance satisfied the requirements outlined in ACI 374.1–05 for the seismic evaluation of structural systems.</div></div>","PeriodicalId":48642,"journal":{"name":"Structures","volume":"86 ","pages":"Article 111305"},"PeriodicalIF":4.3,"publicationDate":"2026-02-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146191402","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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