Pub Date : 2024-09-02DOI: 10.1016/j.istruc.2024.107210
Jun Zhao, Yi Zhao, Fuqiang Shen, Xiaopeng Li, Lu Yin
To achieve the expected seismic properties of high energy consumption and resilience for well used concrete shear walls, the paper presents experimental and numerical study on seismic behavior of concrete shear walls reinforced by carbon fiber-reinforced polymer (CFRP) bars in boundary elements and magnetorheological (MR) dampers. Firstly, a full-scale multi-coil shear valve MR damper was developed and tested under cyclic load to study the effects of current and displacement on the mechanical properties of the MR damper. Then five full-scale cantilever wall specimens reinforced with CFRP bars and MR dampers were tested under reversed cyclic lateral load under different axial load ratios and damping forces. All specimens exhibited significant resilience with little residual drift less than 0.5 %. It was observed that with the increase of axial load ratio, the load-bearing capacity and energy consumption increased, while the ultimate deformation decreased. The load-bearing capacity and energy consumption were improved by increasing the current of the MR damper. Finally, a parallel numerical simulation and parameter analysis were conducted based on a proposed numerical analysis model considering the slippage of CFRP bars. The parameter analysis discussed the effects of the parameters of concrete strength, CFRP bar modulus, steel bar strength, and installation height of MR damper on seismic behavior of the wall.
{"title":"Experimental and numerical study on seismic behavior of high energy-consuming resilient concrete shear walls reinforced by CFRP bars and magnetorheological dampers","authors":"Jun Zhao, Yi Zhao, Fuqiang Shen, Xiaopeng Li, Lu Yin","doi":"10.1016/j.istruc.2024.107210","DOIUrl":"https://doi.org/10.1016/j.istruc.2024.107210","url":null,"abstract":"To achieve the expected seismic properties of high energy consumption and resilience for well used concrete shear walls, the paper presents experimental and numerical study on seismic behavior of concrete shear walls reinforced by carbon fiber-reinforced polymer (CFRP) bars in boundary elements and magnetorheological (MR) dampers. Firstly, a full-scale multi-coil shear valve MR damper was developed and tested under cyclic load to study the effects of current and displacement on the mechanical properties of the MR damper. Then five full-scale cantilever wall specimens reinforced with CFRP bars and MR dampers were tested under reversed cyclic lateral load under different axial load ratios and damping forces. All specimens exhibited significant resilience with little residual drift less than 0.5 %. It was observed that with the increase of axial load ratio, the load-bearing capacity and energy consumption increased, while the ultimate deformation decreased. The load-bearing capacity and energy consumption were improved by increasing the current of the MR damper. Finally, a parallel numerical simulation and parameter analysis were conducted based on a proposed numerical analysis model considering the slippage of CFRP bars. The parameter analysis discussed the effects of the parameters of concrete strength, CFRP bar modulus, steel bar strength, and installation height of MR damper on seismic behavior of the wall.","PeriodicalId":48642,"journal":{"name":"Structures","volume":null,"pages":null},"PeriodicalIF":4.1,"publicationDate":"2024-09-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142222002","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 : 2024-09-02DOI: 10.1016/j.istruc.2024.107189
Juke Wang, Xiaojun Li, Aiwen Liu, Su Chen, Lei Fu, Haoran Liu, Fangfang Li
In the past decades, considerable attention has been paid to the strongly nonlinear control-structure interaction (CSI) between shaking table array and test structure. Although some encouraging progress have been made, developing accurate system model and conducting in-depth analysis are less successful and still require further research. This work establishes an analytical model of two different shaking tables and test structure. Based on the analytical model, an in-depth study is conducted to investigate the CSI effects under different shaking table conditions. The analysis shows the CSI effects on single shaking table, the coupling between shaking tables, the synchronous and tracking control performance of shaking table array, and the measured frequency of test structure. Compared with previous studies which assume two shaking tables are the same, the new findings are that the influence of the CSI on single shaking table decreases, the synchronization performance of shaking table array is extremely degraded, and the measured frequency is smaller than the real frequency of test structure. More importantly, the previous shaking table test results can be corrected based on this study.
{"title":"Investigation on the nonlinear interaction between electro-hydraulic shaking table array and test structure","authors":"Juke Wang, Xiaojun Li, Aiwen Liu, Su Chen, Lei Fu, Haoran Liu, Fangfang Li","doi":"10.1016/j.istruc.2024.107189","DOIUrl":"https://doi.org/10.1016/j.istruc.2024.107189","url":null,"abstract":"In the past decades, considerable attention has been paid to the strongly nonlinear control-structure interaction (CSI) between shaking table array and test structure. Although some encouraging progress have been made, developing accurate system model and conducting in-depth analysis are less successful and still require further research. This work establishes an analytical model of two different shaking tables and test structure. Based on the analytical model, an in-depth study is conducted to investigate the CSI effects under different shaking table conditions. The analysis shows the CSI effects on single shaking table, the coupling between shaking tables, the synchronous and tracking control performance of shaking table array, and the measured frequency of test structure. Compared with previous studies which assume two shaking tables are the same, the new findings are that the influence of the CSI on single shaking table decreases, the synchronization performance of shaking table array is extremely degraded, and the measured frequency is smaller than the real frequency of test structure. More importantly, the previous shaking table test results can be corrected based on this study.","PeriodicalId":48642,"journal":{"name":"Structures","volume":null,"pages":null},"PeriodicalIF":4.1,"publicationDate":"2024-09-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142222006","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 : 2024-09-01DOI: 10.1016/j.istruc.2024.107102
Kadir Ozakgul, Mehmet Fatih Yilmaz, Fatih Yilmaz, Barlas Ozden Caglayan, Iman Hajirasouliha
While many railway viaducts still in use in Turkish railway networks are located on active fault zones that produced historical destructive earthquakes, they are not seismically designed in accordance to current standards. This study aims to provide a better understanding about the serviceability fragility of such systems by conducting detailed probability-based seismic assessments under near-field and far-field earthquakes. To achieve this, firstly, 3D finite element models of a range of selected viaducts in Turkey were generated based on their original design drawings. The developed FE models were validated by comparing the analytical modal frequencies with the results of in-situ dynamic tests involving a series of acceleration measurements. Nonlinear time history analyses were then carried out under 25 near-field and 25 far-field real three-component ground motion recordings to obtain the seismic response of each selected viaduct. Subsequently, probabilistic seismic demand models were defined using linear regression analysis to determine relationships between engineering demand parameters (EDPs) and ground motion intensity measures (IMs). Peak ground acceleration (PGA), peak ground velocity (PGV) and spectral acceleration at 1.0 s (Sa (1.0)) were used as the IM parameter, while the maximum lateral displacement of the bridge spans for different service velocities defined in the Eurocode was considered as the EDP at serviceability damage state. Finally, analytical fragility curves for all the selected railway viaducts were developed considering maximum damage probability for the IM levels. The results, in general, demonstrate the seismic vulnerability of the existing viaducts in Turkey. It is shown that while at low speed limits the viaducts exposed to far-field ground motions were more vulnerable than those under near-field ground motions, at high speed limits the viaducts subjected to near-field ground motions were more vulnerable. Also, it is seen that reinforced concrete and masonry viaducts are generally more vulnerable to earthquakes than the steel viaducts. The outcomes of this study should prove useful for the seismic risk assessment, loss estimation and rehabilitation of the railway transportation networks in future studies.
土耳其铁路网中仍在使用的许多铁路高架桥都位于历史上曾发生过破坏性地震的活动断层带上，但它们的抗震设计并不符合现行标准。本研究旨在通过在近场和远场地震下进行详细的基于概率的地震评估，更好地了解此类系统的适用性脆性。为此，首先根据原始设计图纸生成了土耳其一系列选定高架桥的三维有限元模型。通过将分析模态频率与涉及一系列加速度测量的现场动态测试结果进行比较，对所开发的有限元模型进行了验证。然后，在 25 次近场和 25 次远场真实三分量地面运动记录下进行了非线性时间历程分析，以获得每座选定高架桥的地震响应。随后，利用线性回归分析确定了概率地震需求模型，以确定工程需求参数（EDPs）与地动烈度测量值（IMs）之间的关系。峰值地动加速度（PGA）、峰值地动速度（PGV）和 1.0 秒时的频谱加速度（Sa (1.0)）被用作地动烈度参数，而《欧洲规范》中规定的不同使用速度下桥跨的最大横向位移则被视为适用性破坏状态下的工程需求参数。最后，考虑到 IM 水平的最大损坏概率，为所有选定的铁路高架桥绘制了分析脆性曲线。总体而言，研究结果表明了土耳其现有高架桥的抗震脆弱性。结果表明，在低速限情况下，受远场地动影响的高架桥比受近场地动影响的高架桥更脆弱，而在高速限情况下，受近场地动影响的高架桥更脆弱。此外，钢筋混凝土和砖石结构的高架桥一般比钢结构的高架桥更容易受到地震的影响。这项研究的成果将有助于今后铁路交通网络的地震风险评估、损失估计和修复。
{"title":"Serviceability fragility assessment of non-seismically designed railway viaducts in Turkey under near-field and far-field earthquakes","authors":"Kadir Ozakgul, Mehmet Fatih Yilmaz, Fatih Yilmaz, Barlas Ozden Caglayan, Iman Hajirasouliha","doi":"10.1016/j.istruc.2024.107102","DOIUrl":"https://doi.org/10.1016/j.istruc.2024.107102","url":null,"abstract":"While many railway viaducts still in use in Turkish railway networks are located on active fault zones that produced historical destructive earthquakes, they are not seismically designed in accordance to current standards. This study aims to provide a better understanding about the serviceability fragility of such systems by conducting detailed probability-based seismic assessments under near-field and far-field earthquakes. To achieve this, firstly, 3D finite element models of a range of selected viaducts in Turkey were generated based on their original design drawings. The developed FE models were validated by comparing the analytical modal frequencies with the results of in-situ dynamic tests involving a series of acceleration measurements. Nonlinear time history analyses were then carried out under 25 near-field and 25 far-field real three-component ground motion recordings to obtain the seismic response of each selected viaduct. Subsequently, probabilistic seismic demand models were defined using linear regression analysis to determine relationships between engineering demand parameters (EDPs) and ground motion intensity measures (IMs). Peak ground acceleration (PGA), peak ground velocity (PGV) and spectral acceleration at 1.0 s (Sa (1.0)) were used as the IM parameter, while the maximum lateral displacement of the bridge spans for different service velocities defined in the Eurocode was considered as the EDP at serviceability damage state. Finally, analytical fragility curves for all the selected railway viaducts were developed considering maximum damage probability for the IM levels. The results, in general, demonstrate the seismic vulnerability of the existing viaducts in Turkey. It is shown that while at low speed limits the viaducts exposed to far-field ground motions were more vulnerable than those under near-field ground motions, at high speed limits the viaducts subjected to near-field ground motions were more vulnerable. Also, it is seen that reinforced concrete and masonry viaducts are generally more vulnerable to earthquakes than the steel viaducts. The outcomes of this study should prove useful for the seismic risk assessment, loss estimation and rehabilitation of the railway transportation networks in future studies.","PeriodicalId":48642,"journal":{"name":"Structures","volume":null,"pages":null},"PeriodicalIF":4.1,"publicationDate":"2024-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142227484","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 : 2024-09-01DOI: 10.1016/j.istruc.2024.107104
Ruiran Li, Jun Yu, Xingde Zhou
Local damage of the structural members and even progressive collapse of structures occurred in terrorist or accidental explosions, but there are few unified frameworks of integrating the member damage into the structural damage for rapid assessment against blast loads. To fill this gap, a framework is proposed for engineering practice to rapidly assess damage levels of regular reinforced concrete (RC) frame structures under external explosions, in which the structural damage level is eventually determined with only two inputs: scaled distance and structural redundancy. A regular 5-story RC frame structure subjected to external explosions is adopted as an example to illustrate the proposed framework. Firstly, damage indexes of structural members are formulated under far-field explosions or close-in explosions, and the structural damage index is further derived through the weighted integration of the damage indexes of structural members. Subsequently, the damage modes and collapse processes of the designed RC frame structure are simulated under different explosion scenarios, and the energy-based damage indexes for assessing structures against blast loads are developed and validated. Through numerical results of 23 case studies, the structural damage assessment formula as a function of scaled distance and structural redundancy is derived through regress analysis, and on the other hand, two key threshold values of the energy-based damage indexes are introduced to classify the structural damage levels (minor, moderate and severe levels). Finally, the structural damage index is correlated to the energy-based damage index through curve-fitting to determine the corresponding threshold values of structural damage index as well, and the effectiveness of the damage assessment framework is further validated. The results show that the proposed damage assessment framework can rapidly and accurately assess the damage levels of the regular RC frame structures under external explosions, and the deviation between the predicted damage indexes and the numerical results are 4.11 %–9.52 %.
{"title":"A rapid damage assessment framework for regular RC frame structures under external explosions","authors":"Ruiran Li, Jun Yu, Xingde Zhou","doi":"10.1016/j.istruc.2024.107104","DOIUrl":"https://doi.org/10.1016/j.istruc.2024.107104","url":null,"abstract":"Local damage of the structural members and even progressive collapse of structures occurred in terrorist or accidental explosions, but there are few unified frameworks of integrating the member damage into the structural damage for rapid assessment against blast loads. To fill this gap, a framework is proposed for engineering practice to rapidly assess damage levels of regular reinforced concrete (RC) frame structures under external explosions, in which the structural damage level is eventually determined with only two inputs: scaled distance and structural redundancy. A regular 5-story RC frame structure subjected to external explosions is adopted as an example to illustrate the proposed framework. Firstly, damage indexes of structural members are formulated under far-field explosions or close-in explosions, and the structural damage index is further derived through the weighted integration of the damage indexes of structural members. Subsequently, the damage modes and collapse processes of the designed RC frame structure are simulated under different explosion scenarios, and the energy-based damage indexes for assessing structures against blast loads are developed and validated. Through numerical results of 23 case studies, the structural damage assessment formula as a function of scaled distance and structural redundancy is derived through regress analysis, and on the other hand, two key threshold values of the energy-based damage indexes are introduced to classify the structural damage levels (minor, moderate and severe levels). Finally, the structural damage index is correlated to the energy-based damage index through curve-fitting to determine the corresponding threshold values of structural damage index as well, and the effectiveness of the damage assessment framework is further validated. The results show that the proposed damage assessment framework can rapidly and accurately assess the damage levels of the regular RC frame structures under external explosions, and the deviation between the predicted damage indexes and the numerical results are 4.11 %–9.52 %.","PeriodicalId":48642,"journal":{"name":"Structures","volume":null,"pages":null},"PeriodicalIF":4.1,"publicationDate":"2024-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142222013","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 : 2024-09-01DOI: 10.1016/j.istruc.2024.107159
Jitendra Khatti, Berivan Yılmazer Polat
This investigation introduces the optimal performance models for predicting the compressive strength (CS) and pozzolanic activity index (PAI) by comparing the machine learning models. The machine learning models, i.e., multilinear regression (MLR), support vector machine (SVM), gaussian process regression (GPR), decision tree (DT), random forest (RF), and gene expression programming (GEP) have been trained (TRN) and tested (TST) by 28 and 7 data points. For the first time, the SiO, AlO, FeO, SiO +AlO +FeO, reactive SiO, Blaine specific surface area, and specific gravity have been used as input variables to compute the CS, and 28 days PAI (28PAI), and 90 days PAI (90PAI) of the natural pozzolans. The multicollinearity analysis showed the SiO, AlO, FeO, SiO +AlO +FeO, reactive SiO, and specific gravity have problematic multicollinearity (variance inflation factor – VIF > 10). Therefore, the root mean square error (RMSE), mean absolute error (MAE), correlation coefficient (R), performance index (PI), and variance accounted for (VAF) metrics have been implemented to evaluate the model's performance and multicollinearity impact. From the comparison of models, it has been recorded that model GPR outperformed the MLR, SVM, DT, RF, and GEP models in predicting CS (PI = 1.29, VAF = 71.31, R = 0.8473, MAE = 0.9390 MPa), 28PAI (PI = 1.87, VAF = 94.88, R = 0.9744, MAE = 0.7295 %), and 90PAI (PI = 1.72, VAF = 88.11, R = 0.9393, MAE = 1.2444 %) in the TST phase, close to ideal values. The score, generalizability. Wilcoxon test, uncertainty analysis, Anderson-daring test, and accuracy metrics have confirmed the superiority of GPR models in predicting CS, 28PAI, and 90PAI of natural pozzolans.
{"title":"Assessment of short and long-term pozzolanic activity of natural pozzolans using machine learning approaches","authors":"Jitendra Khatti, Berivan Yılmazer Polat","doi":"10.1016/j.istruc.2024.107159","DOIUrl":"https://doi.org/10.1016/j.istruc.2024.107159","url":null,"abstract":"This investigation introduces the optimal performance models for predicting the compressive strength (CS) and pozzolanic activity index (PAI) by comparing the machine learning models. The machine learning models, i.e., multilinear regression (MLR), support vector machine (SVM), gaussian process regression (GPR), decision tree (DT), random forest (RF), and gene expression programming (GEP) have been trained (TRN) and tested (TST) by 28 and 7 data points. For the first time, the SiO, AlO, FeO, SiO +AlO +FeO, reactive SiO, Blaine specific surface area, and specific gravity have been used as input variables to compute the CS, and 28 days PAI (28PAI), and 90 days PAI (90PAI) of the natural pozzolans. The multicollinearity analysis showed the SiO, AlO, FeO, SiO +AlO +FeO, reactive SiO, and specific gravity have problematic multicollinearity (variance inflation factor – VIF > 10). Therefore, the root mean square error (RMSE), mean absolute error (MAE), correlation coefficient (R), performance index (PI), and variance accounted for (VAF) metrics have been implemented to evaluate the model's performance and multicollinearity impact. From the comparison of models, it has been recorded that model GPR outperformed the MLR, SVM, DT, RF, and GEP models in predicting CS (PI = 1.29, VAF = 71.31, R = 0.8473, MAE = 0.9390 MPa), 28PAI (PI = 1.87, VAF = 94.88, R = 0.9744, MAE = 0.7295 %), and 90PAI (PI = 1.72, VAF = 88.11, R = 0.9393, MAE = 1.2444 %) in the TST phase, close to ideal values. The score, generalizability. Wilcoxon test, uncertainty analysis, Anderson-daring test, and accuracy metrics have confirmed the superiority of GPR models in predicting CS, 28PAI, and 90PAI of natural pozzolans.","PeriodicalId":48642,"journal":{"name":"Structures","volume":null,"pages":null},"PeriodicalIF":4.1,"publicationDate":"2024-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142222012","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 : 2024-09-01DOI: 10.1016/j.istruc.2024.107206
Lu Gan, Zhouhong Zong, Minghong Li, Haimin Qian, Jin Lin
Scaling model was widely used in engineering to reveal the responses of full-scale prototype model. This study provided insight into the impact of the scale effect on the dynamic response and damage of stiffened and unstiffened steel plates under explosions. A numerical model consider fluid-structure-interaction (FSI) was established using LS-DYNA platform, and the numerical model was verified by the blast test results. Moreover, the scaling factors () equal to 1 (prototype), 1/2, and 1/4, and 1/8, and 1/12 were considered in the study, the scaling effects on the breach size, plastic area, and the deformation shape were analyzed. The results showed that the breach size and plastic area of the scaled model deviated from the ideal results based on the replica law. However, the deformation shapes of scaled-down plates accurately reflected the deformation characteristics of the full prototype plate. The scaling factor significantly influenced the dynamic responses of stiffened and unstiffened steel plates; as the scaling factor () increased, the dimensionless displacement decreased. The results indicated that a smaller led to a larger deviation in response. The influencing factors of the scaling effect were investigated, and it was found that stiffened steel plates were more sensitive to the scaling factor than unstiffened steel plates. By comparing the detonation of cuboid, cylindrical, and spherical explosives blast-loaded onto stiffened steel plates, it was determined that the detonation of cubic explosives caused the most severe scaling effect on stiffened steel plates under blast loads. The study also found that explosive mass and standoff distance influenced the scaling effect of stiffened steel plates under blast loads. Additionally, steel plates in the plastic stage and the critical state between the elastic and plastic stages were particularly sensitive to the scaling effect. Due to the strain rate effect, which can lead to a deviation from the ideal scale law, different steel materials exhibit varying scale sensitivities. Comparing stiffened plates made from Q235, Q345, DH36, and L907A, the order of sensitivity to the scaling factor was: Q235 > Q345 ≈ DH36 > L907A.
{"title":"Impact of prototype scale effect on the dynamic responses and damage of steel plates under explosions","authors":"Lu Gan, Zhouhong Zong, Minghong Li, Haimin Qian, Jin Lin","doi":"10.1016/j.istruc.2024.107206","DOIUrl":"https://doi.org/10.1016/j.istruc.2024.107206","url":null,"abstract":"Scaling model was widely used in engineering to reveal the responses of full-scale prototype model. This study provided insight into the impact of the scale effect on the dynamic response and damage of stiffened and unstiffened steel plates under explosions. A numerical model consider fluid-structure-interaction (FSI) was established using LS-DYNA platform, and the numerical model was verified by the blast test results. Moreover, the scaling factors () equal to 1 (prototype), 1/2, and 1/4, and 1/8, and 1/12 were considered in the study, the scaling effects on the breach size, plastic area, and the deformation shape were analyzed. The results showed that the breach size and plastic area of the scaled model deviated from the ideal results based on the replica law. However, the deformation shapes of scaled-down plates accurately reflected the deformation characteristics of the full prototype plate. The scaling factor significantly influenced the dynamic responses of stiffened and unstiffened steel plates; as the scaling factor () increased, the dimensionless displacement decreased. The results indicated that a smaller led to a larger deviation in response. The influencing factors of the scaling effect were investigated, and it was found that stiffened steel plates were more sensitive to the scaling factor than unstiffened steel plates. By comparing the detonation of cuboid, cylindrical, and spherical explosives blast-loaded onto stiffened steel plates, it was determined that the detonation of cubic explosives caused the most severe scaling effect on stiffened steel plates under blast loads. The study also found that explosive mass and standoff distance influenced the scaling effect of stiffened steel plates under blast loads. Additionally, steel plates in the plastic stage and the critical state between the elastic and plastic stages were particularly sensitive to the scaling effect. Due to the strain rate effect, which can lead to a deviation from the ideal scale law, different steel materials exhibit varying scale sensitivities. Comparing stiffened plates made from Q235, Q345, DH36, and L907A, the order of sensitivity to the scaling factor was: Q235 > Q345 ≈ DH36 > L907A.","PeriodicalId":48642,"journal":{"name":"Structures","volume":null,"pages":null},"PeriodicalIF":4.1,"publicationDate":"2024-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142222026","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}
The coupling between the creep and shrinkage of concrete, tendon relaxation, and temperature variations makes it difficult to determine the influence of each individual factor on prestress loss. This study investigates the influence of these multiple factors on the medium and short-term prestress of beam bridges, crucial for their durability and safety. Initially, laboratory experiments were conducted on six model beams to analyze medium and short-term prestress variations. Using a pre-designed scheme, the study isolated and quantified the impacts on effective prestress, with losses calculated through superposition. The findings were compared with existing models, leading to the proposal of a refined model for multiple factors affecting prestress. Then the prestress loss experiments on ten full-sized beams, with thirty-five strands, were calibrated based on the proposed model by regression analysis. Based on the modified model of prestress loss, the mentioned influencing factors would be calculated separately, which agree with the measured data from laboratory and in-situ experiments. In the end, the study concludes that creep has the greatest impact on prestress loss, with other factors contributing to varying degrees. Through full-scale tests, parameters for the prestress loss model were verified. The proposed model in this study effectively describes prestress loss within the tested timeframe. The study further concludes that there existed a time lag in prestress tendons and ambient temperature in both laboratory model beams and in-situ full-scale beams. For practical applications in lift-off tests of effective prestress, the appropriate testing time after tensioning to yield relatively stable results is recommended.
{"title":"Medium and short-term effective prestress losses considering multiple factors: Laboratory and on-site beam experiments","authors":"Faxiang Xie, Tianliang Chang, Chuanlong Zhang, Feng Zhang, Geni Kuang, Yun Zhang","doi":"10.1016/j.istruc.2024.107166","DOIUrl":"https://doi.org/10.1016/j.istruc.2024.107166","url":null,"abstract":"The coupling between the creep and shrinkage of concrete, tendon relaxation, and temperature variations makes it difficult to determine the influence of each individual factor on prestress loss. This study investigates the influence of these multiple factors on the medium and short-term prestress of beam bridges, crucial for their durability and safety. Initially, laboratory experiments were conducted on six model beams to analyze medium and short-term prestress variations. Using a pre-designed scheme, the study isolated and quantified the impacts on effective prestress, with losses calculated through superposition. The findings were compared with existing models, leading to the proposal of a refined model for multiple factors affecting prestress. Then the prestress loss experiments on ten full-sized beams, with thirty-five strands, were calibrated based on the proposed model by regression analysis. Based on the modified model of prestress loss, the mentioned influencing factors would be calculated separately, which agree with the measured data from laboratory and in-situ experiments. In the end, the study concludes that creep has the greatest impact on prestress loss, with other factors contributing to varying degrees. Through full-scale tests, parameters for the prestress loss model were verified. The proposed model in this study effectively describes prestress loss within the tested timeframe. The study further concludes that there existed a time lag in prestress tendons and ambient temperature in both laboratory model beams and in-situ full-scale beams. For practical applications in lift-off tests of effective prestress, the appropriate testing time after tensioning to yield relatively stable results is recommended.","PeriodicalId":48642,"journal":{"name":"Structures","volume":null,"pages":null},"PeriodicalIF":4.1,"publicationDate":"2024-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142222029","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 : 2024-08-31DOI: 10.1016/j.istruc.2024.107173
Peng Li, Liang Fan, Wei Shen, Fei Wang
The cold-sprayed zinc technology exhibits unique advantages in the field of metal corrosion prevention due to its environmental friendliness and convenient construction. However, compared to hot-dip galvanizing, there is still a necessity to improve its corrosion resistance. Graphene as a filler material, effectively strengthens the anticorrosive properties of the coating. Nevertheless, the resistance of graphene-modified cold-sprayed zinc coating to chloride ion induced metal corrosion remains unknown. In this study, cold-sprayed zinc coating and graphene-modified zinc coating were employed to steel rebar that was subjected to different levels of tensile stress. The passivation and de-passivation process of the stretched zinc-coated rebar in the simulated concrete pore solution were investigated with electrochemical tests and microscopic analyses. The research findings reveal that compared with ordinary cold-sprayed zinc coating, graphene-modified coating can significantly improve the coating resistance and reduce the corrosion rate of rebar under different levels of tensile stress attributed to the high surface area of graphene. However, due to the discontinuity between zinc powders induced by graphene, a complete passivation film cannot form on the surface of graphene-modified zinc coating, which resulted in a lower resistance against chloride ion induced de-passivation. This study indicates that graphene-modified cold-sprayed zinc-coating is not fit for marine environment.
{"title":"Corrosion protection performance of stretched graphene-modified cold-sprayed zinc coating for steel rebar","authors":"Peng Li, Liang Fan, Wei Shen, Fei Wang","doi":"10.1016/j.istruc.2024.107173","DOIUrl":"https://doi.org/10.1016/j.istruc.2024.107173","url":null,"abstract":"The cold-sprayed zinc technology exhibits unique advantages in the field of metal corrosion prevention due to its environmental friendliness and convenient construction. However, compared to hot-dip galvanizing, there is still a necessity to improve its corrosion resistance. Graphene as a filler material, effectively strengthens the anticorrosive properties of the coating. Nevertheless, the resistance of graphene-modified cold-sprayed zinc coating to chloride ion induced metal corrosion remains unknown. In this study, cold-sprayed zinc coating and graphene-modified zinc coating were employed to steel rebar that was subjected to different levels of tensile stress. The passivation and de-passivation process of the stretched zinc-coated rebar in the simulated concrete pore solution were investigated with electrochemical tests and microscopic analyses. The research findings reveal that compared with ordinary cold-sprayed zinc coating, graphene-modified coating can significantly improve the coating resistance and reduce the corrosion rate of rebar under different levels of tensile stress attributed to the high surface area of graphene. However, due to the discontinuity between zinc powders induced by graphene, a complete passivation film cannot form on the surface of graphene-modified zinc coating, which resulted in a lower resistance against chloride ion induced de-passivation. This study indicates that graphene-modified cold-sprayed zinc-coating is not fit for marine environment.","PeriodicalId":48642,"journal":{"name":"Structures","volume":null,"pages":null},"PeriodicalIF":4.1,"publicationDate":"2024-08-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142222030","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 : 2024-08-31DOI: 10.1016/j.istruc.2024.107205
Bin Li, Xiangyang Wang, Danyang Di, Wei Yu, Hongyuan Fang, Xueming Du, Niannian Wang, Tilang Zhang, Kejie Zhai
Due to varying burial conditions and service environments, concrete pipes exhibit complex mechanical behavior. Existing theoretical, simulation, and test methods for determining the maximum stress of pipes have significant limitations, including excessive assumptions, low efficiency, and restricted applicable conditions. Therefore, there is an urgent need to propose a multi-factor associated method for pipe stress prediction. This paper proposed an innovative approach to finely simulate the mechanics response for concrete pipes under the coupling action of stress-seepage-fluid fields. The accuracy of this numerical simulation method was validated through full-scale test. Sensitivity analysis based on Morris sensitivity analysis theory was conducted on traffic load magnitude and speed, buried depth, groundwater table, fluid height and velocity, bedding strength, backfill strength, and pipe diameter. A dataset of “physical variables - maximum stress” for concrete pipes was established. A multi-factor-correlated prediction model of maximum stress for concrete pipe was proposed using XGBoost machine learning method optimized by Particle Swarm Optimization (PSO) algorithm. The results indicate that pipe diameter is highly sensitive; buried depth and traffic load magnitude are sensitive; groundwater table, bedding strength, and backfill strength are moderately sensitive; while fluid height, traffic speed, and flow velocity are insensitive. The XGBoost-PSO model demonstrates the highest accuracy and lowest error compared to BP, RF, and XGBoost models, with improvements in prediction accuracy of 59.6 %, 23.8 %, and 8.6 %, respectively. The model achieves RMSE of 0.118 and MAE of 0.213, demonstrating the suitability of the XGBoost-PSO model for predicting maximum stress for concrete pipes.
{"title":"Prediction model of maximum stress for concrete pipes based on XGBoost-PSO algorithm","authors":"Bin Li, Xiangyang Wang, Danyang Di, Wei Yu, Hongyuan Fang, Xueming Du, Niannian Wang, Tilang Zhang, Kejie Zhai","doi":"10.1016/j.istruc.2024.107205","DOIUrl":"https://doi.org/10.1016/j.istruc.2024.107205","url":null,"abstract":"Due to varying burial conditions and service environments, concrete pipes exhibit complex mechanical behavior. Existing theoretical, simulation, and test methods for determining the maximum stress of pipes have significant limitations, including excessive assumptions, low efficiency, and restricted applicable conditions. Therefore, there is an urgent need to propose a multi-factor associated method for pipe stress prediction. This paper proposed an innovative approach to finely simulate the mechanics response for concrete pipes under the coupling action of stress-seepage-fluid fields. The accuracy of this numerical simulation method was validated through full-scale test. Sensitivity analysis based on Morris sensitivity analysis theory was conducted on traffic load magnitude and speed, buried depth, groundwater table, fluid height and velocity, bedding strength, backfill strength, and pipe diameter. A dataset of “physical variables - maximum stress” for concrete pipes was established. A multi-factor-correlated prediction model of maximum stress for concrete pipe was proposed using XGBoost machine learning method optimized by Particle Swarm Optimization (PSO) algorithm. The results indicate that pipe diameter is highly sensitive; buried depth and traffic load magnitude are sensitive; groundwater table, bedding strength, and backfill strength are moderately sensitive; while fluid height, traffic speed, and flow velocity are insensitive. The XGBoost-PSO model demonstrates the highest accuracy and lowest error compared to BP, RF, and XGBoost models, with improvements in prediction accuracy of 59.6 %, 23.8 %, and 8.6 %, respectively. The model achieves RMSE of 0.118 and MAE of 0.213, demonstrating the suitability of the XGBoost-PSO model for predicting maximum stress for concrete pipes.","PeriodicalId":48642,"journal":{"name":"Structures","volume":null,"pages":null},"PeriodicalIF":4.1,"publicationDate":"2024-08-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142222025","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 : 2024-08-31DOI: 10.1016/j.istruc.2024.107174
Abdulaziz Alsaif, Abdulrahman Albidah
The integration of waste tire elements into concrete, specifically granular rubber and discrete steel fibers, signifies a substantial advance in the pursuit of sustainable alternatives for rigid concrete pavements. This incorporation not only improves the ductility of rigid concrete pavements, but also augments their energy absorption capabilities. Similarly, replacing natural aggregates in concrete with reclaimed asphalt pavement (RAP) aggregates makes a large contribution to the reduction of negative environmental impacts, while conserving natural resources from depletion. This investigation explores the potential application of recycled rubber particles from waste tires (WTRR) and RAP aggregates as partial substitutes for natural fine aggregates, and evaluates their impact on the performance of rigid concrete pavements. Eight mixes were cast, each with two variables: (i) fine aggregate type (fine rubber (FRu) aggregates, fine asphalt (FAs) aggregates, and combinations of both types of aggregate) replacing 50 % of the natural fine aggregate; and (ii) waste tire recycled steel fibers (WTRSF) content (0 and 40 kg/m). The axial compressive stress–strain, flexural load–deflection, and direct shear strength behaviors, together with the dry unit weight and volume of permeable voids for all concrete mixes were investigated and compared. The results show that, although the flexural and shear strengths decrease with the inclusion of FRu and/or FAs, the use of WTRSF noticeably mitigates the losses in strength that arise from the use of WTRR and/or RAP aggregates alone. The inclusion of WTRSF enhances the strain capacity of the concrete and allows the development of adequate post-peak energy absorption capacity in flexural and shear loading. Additionally, the dry unit weight of the proposed composites decreased by as much as 8 %, and their volume of permeable voids lies within the limits of high-durability concrete mixes (9–12 %). Hence, the proposed sustainable concrete composites are promising composites for rigid concrete pavement construction.
{"title":"Production of rubberized concrete utilizing reclaimed asphalt pavement aggregates and recycled tire steel fibers","authors":"Abdulaziz Alsaif, Abdulrahman Albidah","doi":"10.1016/j.istruc.2024.107174","DOIUrl":"https://doi.org/10.1016/j.istruc.2024.107174","url":null,"abstract":"The integration of waste tire elements into concrete, specifically granular rubber and discrete steel fibers, signifies a substantial advance in the pursuit of sustainable alternatives for rigid concrete pavements. This incorporation not only improves the ductility of rigid concrete pavements, but also augments their energy absorption capabilities. Similarly, replacing natural aggregates in concrete with reclaimed asphalt pavement (RAP) aggregates makes a large contribution to the reduction of negative environmental impacts, while conserving natural resources from depletion. This investigation explores the potential application of recycled rubber particles from waste tires (WTRR) and RAP aggregates as partial substitutes for natural fine aggregates, and evaluates their impact on the performance of rigid concrete pavements. Eight mixes were cast, each with two variables: (i) fine aggregate type (fine rubber (FRu) aggregates, fine asphalt (FAs) aggregates, and combinations of both types of aggregate) replacing 50 % of the natural fine aggregate; and (ii) waste tire recycled steel fibers (WTRSF) content (0 and 40 kg/m). The axial compressive stress–strain, flexural load–deflection, and direct shear strength behaviors, together with the dry unit weight and volume of permeable voids for all concrete mixes were investigated and compared. The results show that, although the flexural and shear strengths decrease with the inclusion of FRu and/or FAs, the use of WTRSF noticeably mitigates the losses in strength that arise from the use of WTRR and/or RAP aggregates alone. The inclusion of WTRSF enhances the strain capacity of the concrete and allows the development of adequate post-peak energy absorption capacity in flexural and shear loading. Additionally, the dry unit weight of the proposed composites decreased by as much as 8 %, and their volume of permeable voids lies within the limits of high-durability concrete mixes (9–12 %). Hence, the proposed sustainable concrete composites are promising composites for rigid concrete pavement construction.","PeriodicalId":48642,"journal":{"name":"Structures","volume":null,"pages":null},"PeriodicalIF":4.1,"publicationDate":"2024-08-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142222014","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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