Pub Date : 2024-02-10DOI: 10.1177/13694332241232049
Jiajing Li, Qiaoyun Wu, Shun Weng
Time history response derivatives with respect to the design variables are frequently used in optimization design, damage detection, structural control, etc. This paper proposes a substructuring method for efficient calculation of higher order time history response derivatives of large-scale structures. First, the global structure is disassembled into several small substructures and the substructural displacement is projected onto the range space of a few substructural master eigenvectors. Afterwards, the derivative of substructural master eigenvectors of a few substructures containing the design variables are assembled to form the reduced first, second, and higher order sensitivity equations with a size of the number of master eigenvectors. The equivalent eigenvector which relates the slave and master eigenvectors is derived to compensate for the inertial effect of discarded slave eigenvectors. Finally, the first, second, and higher order time history response derivatives of global large-scale structure are efficiently solved from the reduced sensitivity equations by using Newmark- β method. A numerical one-bay plane frame and a numerical highway bridge are applied to verify the accuracy and efficiency of proposed substructuring method.
{"title":"Efficient calculation of higher order time history response derivatives by substructuring method","authors":"Jiajing Li, Qiaoyun Wu, Shun Weng","doi":"10.1177/13694332241232049","DOIUrl":"https://doi.org/10.1177/13694332241232049","url":null,"abstract":"Time history response derivatives with respect to the design variables are frequently used in optimization design, damage detection, structural control, etc. This paper proposes a substructuring method for efficient calculation of higher order time history response derivatives of large-scale structures. First, the global structure is disassembled into several small substructures and the substructural displacement is projected onto the range space of a few substructural master eigenvectors. Afterwards, the derivative of substructural master eigenvectors of a few substructures containing the design variables are assembled to form the reduced first, second, and higher order sensitivity equations with a size of the number of master eigenvectors. The equivalent eigenvector which relates the slave and master eigenvectors is derived to compensate for the inertial effect of discarded slave eigenvectors. Finally, the first, second, and higher order time history response derivatives of global large-scale structure are efficiently solved from the reduced sensitivity equations by using Newmark- β method. A numerical one-bay plane frame and a numerical highway bridge are applied to verify the accuracy and efficiency of proposed substructuring method.","PeriodicalId":505409,"journal":{"name":"Advances in Structural Engineering","volume":" 5","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-02-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139786830","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-02-09DOI: 10.1177/13694332241232050
Li Wang, Biao Liu, Ziqi Li, Yu-Xing Zhang, Lu-Song Yu
To better understand the mechanical property issues of in-service concrete-filled steel tube (CFST) bridges susceptible to natural environmental temperatures, 13 CFST stub columns were assessed under axial compression with different ambient temperatures and steel ratios, with the strength of the core concrete as the main parameters. The influence of ambient temperature on the peak strain and joint elastic modulus of the CFST stubs was investigated. The influence mechanism of steel content and core concrete strength on the residual toughness of the CFST at different ambient temperatures was revealed. In this study, we proposed a modified constitutive equation for CFST, taking into account the ambient temperature. We demonstrated that the peak strain, residual toughness ratio, and elastic modulus of the CFST stubs significantly decreased when the temperature decreased. The calculated values of the modified constitutive equation for CFST, taking into account the ambient temperature, were in good agreement with the test results and could be used to predict the trends in stress properties of the CFST stubs at different temperatures. The results could serve as a critical reference for the design and calculation of CFST structures in very cold regions.
{"title":"Experimental study on axial compression properties of concrete filled steel tubular stub columns in varying ambient temperature","authors":"Li Wang, Biao Liu, Ziqi Li, Yu-Xing Zhang, Lu-Song Yu","doi":"10.1177/13694332241232050","DOIUrl":"https://doi.org/10.1177/13694332241232050","url":null,"abstract":"To better understand the mechanical property issues of in-service concrete-filled steel tube (CFST) bridges susceptible to natural environmental temperatures, 13 CFST stub columns were assessed under axial compression with different ambient temperatures and steel ratios, with the strength of the core concrete as the main parameters. The influence of ambient temperature on the peak strain and joint elastic modulus of the CFST stubs was investigated. The influence mechanism of steel content and core concrete strength on the residual toughness of the CFST at different ambient temperatures was revealed. In this study, we proposed a modified constitutive equation for CFST, taking into account the ambient temperature. We demonstrated that the peak strain, residual toughness ratio, and elastic modulus of the CFST stubs significantly decreased when the temperature decreased. The calculated values of the modified constitutive equation for CFST, taking into account the ambient temperature, were in good agreement with the test results and could be used to predict the trends in stress properties of the CFST stubs at different temperatures. The results could serve as a critical reference for the design and calculation of CFST structures in very cold regions.","PeriodicalId":505409,"journal":{"name":"Advances in Structural Engineering","volume":" 6","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-02-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139789550","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The utilization of fiber-reinforced polymer (FRP) reinforcements in structural design is increasing due to their non-corrosive nature. However, the anisotropic features and linear elastic behavior of FRP rebars have led researchers to explore the use of hybrid combinations of FRP and steel reinforcements. Current codes and guidelines predominantly focus on the design of glass FRP (GFRP) reinforced structural elements, leaving a gap in incorporating the hybrid use of FRP-steel combinations and different types of FRP materials, such as carbon FRP (CFRP). This study conducted experimental investigations on concrete beams reinforced with GFRP, CFRP, and hybrid (GFRP-steel and CFRP-steel in combination) rebars, comparing the results with theoretical models. Ten full-scale beams were tested under monotonic loading. Test results revealed that existing codes overestimate GFRP reinforced beam displacements while underestimating CFRP reinforced beam displacements. A reduction factor is proposed for the effective moment of inertia expression given by ACI 440.11-22 to predict the deflections of CFRP reinforced and hybrid reinforced beams. The experimental data for CFRP and hybrid reinforced concrete beams align well with the predictions calculated using the proposed equations.
{"title":"Flexural behavior of concrete beams hybrid-reinforced with glass fiber-reinforced polymer, carbon fiber-reinforced polymer, and steel rebars","authors":"Hilal Terzioglu, Meltem Eryilmaz Yildirim, Omer Karagoz, E. Unluoglu, Mizan Dogan","doi":"10.1177/13694332241232051","DOIUrl":"https://doi.org/10.1177/13694332241232051","url":null,"abstract":"The utilization of fiber-reinforced polymer (FRP) reinforcements in structural design is increasing due to their non-corrosive nature. However, the anisotropic features and linear elastic behavior of FRP rebars have led researchers to explore the use of hybrid combinations of FRP and steel reinforcements. Current codes and guidelines predominantly focus on the design of glass FRP (GFRP) reinforced structural elements, leaving a gap in incorporating the hybrid use of FRP-steel combinations and different types of FRP materials, such as carbon FRP (CFRP). This study conducted experimental investigations on concrete beams reinforced with GFRP, CFRP, and hybrid (GFRP-steel and CFRP-steel in combination) rebars, comparing the results with theoretical models. Ten full-scale beams were tested under monotonic loading. Test results revealed that existing codes overestimate GFRP reinforced beam displacements while underestimating CFRP reinforced beam displacements. A reduction factor is proposed for the effective moment of inertia expression given by ACI 440.11-22 to predict the deflections of CFRP reinforced and hybrid reinforced beams. The experimental data for CFRP and hybrid reinforced concrete beams align well with the predictions calculated using the proposed equations.","PeriodicalId":505409,"journal":{"name":"Advances in Structural Engineering","volume":" 9","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-02-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139788244","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The utilization of fiber-reinforced polymer (FRP) reinforcements in structural design is increasing due to their non-corrosive nature. However, the anisotropic features and linear elastic behavior of FRP rebars have led researchers to explore the use of hybrid combinations of FRP and steel reinforcements. Current codes and guidelines predominantly focus on the design of glass FRP (GFRP) reinforced structural elements, leaving a gap in incorporating the hybrid use of FRP-steel combinations and different types of FRP materials, such as carbon FRP (CFRP). This study conducted experimental investigations on concrete beams reinforced with GFRP, CFRP, and hybrid (GFRP-steel and CFRP-steel in combination) rebars, comparing the results with theoretical models. Ten full-scale beams were tested under monotonic loading. Test results revealed that existing codes overestimate GFRP reinforced beam displacements while underestimating CFRP reinforced beam displacements. A reduction factor is proposed for the effective moment of inertia expression given by ACI 440.11-22 to predict the deflections of CFRP reinforced and hybrid reinforced beams. The experimental data for CFRP and hybrid reinforced concrete beams align well with the predictions calculated using the proposed equations.
{"title":"Flexural behavior of concrete beams hybrid-reinforced with glass fiber-reinforced polymer, carbon fiber-reinforced polymer, and steel rebars","authors":"Hilal Terzioglu, Meltem Eryilmaz Yildirim, Omer Karagoz, E. Unluoglu, Mizan Dogan","doi":"10.1177/13694332241232051","DOIUrl":"https://doi.org/10.1177/13694332241232051","url":null,"abstract":"The utilization of fiber-reinforced polymer (FRP) reinforcements in structural design is increasing due to their non-corrosive nature. However, the anisotropic features and linear elastic behavior of FRP rebars have led researchers to explore the use of hybrid combinations of FRP and steel reinforcements. Current codes and guidelines predominantly focus on the design of glass FRP (GFRP) reinforced structural elements, leaving a gap in incorporating the hybrid use of FRP-steel combinations and different types of FRP materials, such as carbon FRP (CFRP). This study conducted experimental investigations on concrete beams reinforced with GFRP, CFRP, and hybrid (GFRP-steel and CFRP-steel in combination) rebars, comparing the results with theoretical models. Ten full-scale beams were tested under monotonic loading. Test results revealed that existing codes overestimate GFRP reinforced beam displacements while underestimating CFRP reinforced beam displacements. A reduction factor is proposed for the effective moment of inertia expression given by ACI 440.11-22 to predict the deflections of CFRP reinforced and hybrid reinforced beams. The experimental data for CFRP and hybrid reinforced concrete beams align well with the predictions calculated using the proposed equations.","PeriodicalId":505409,"journal":{"name":"Advances in Structural Engineering","volume":"370 7","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-02-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139847960","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-02-09DOI: 10.1177/13694332241232050
Li Wang, Biao Liu, Ziqi Li, Yu-Xing Zhang, Lu-Song Yu
To better understand the mechanical property issues of in-service concrete-filled steel tube (CFST) bridges susceptible to natural environmental temperatures, 13 CFST stub columns were assessed under axial compression with different ambient temperatures and steel ratios, with the strength of the core concrete as the main parameters. The influence of ambient temperature on the peak strain and joint elastic modulus of the CFST stubs was investigated. The influence mechanism of steel content and core concrete strength on the residual toughness of the CFST at different ambient temperatures was revealed. In this study, we proposed a modified constitutive equation for CFST, taking into account the ambient temperature. We demonstrated that the peak strain, residual toughness ratio, and elastic modulus of the CFST stubs significantly decreased when the temperature decreased. The calculated values of the modified constitutive equation for CFST, taking into account the ambient temperature, were in good agreement with the test results and could be used to predict the trends in stress properties of the CFST stubs at different temperatures. The results could serve as a critical reference for the design and calculation of CFST structures in very cold regions.
{"title":"Experimental study on axial compression properties of concrete filled steel tubular stub columns in varying ambient temperature","authors":"Li Wang, Biao Liu, Ziqi Li, Yu-Xing Zhang, Lu-Song Yu","doi":"10.1177/13694332241232050","DOIUrl":"https://doi.org/10.1177/13694332241232050","url":null,"abstract":"To better understand the mechanical property issues of in-service concrete-filled steel tube (CFST) bridges susceptible to natural environmental temperatures, 13 CFST stub columns were assessed under axial compression with different ambient temperatures and steel ratios, with the strength of the core concrete as the main parameters. The influence of ambient temperature on the peak strain and joint elastic modulus of the CFST stubs was investigated. The influence mechanism of steel content and core concrete strength on the residual toughness of the CFST at different ambient temperatures was revealed. In this study, we proposed a modified constitutive equation for CFST, taking into account the ambient temperature. We demonstrated that the peak strain, residual toughness ratio, and elastic modulus of the CFST stubs significantly decreased when the temperature decreased. The calculated values of the modified constitutive equation for CFST, taking into account the ambient temperature, were in good agreement with the test results and could be used to predict the trends in stress properties of the CFST stubs at different temperatures. The results could serve as a critical reference for the design and calculation of CFST structures in very cold regions.","PeriodicalId":505409,"journal":{"name":"Advances in Structural Engineering","volume":"2021 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-02-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139849327","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-02-08DOI: 10.1177/13694332241232046
C. Karthik, M. Anbarasu, M. A. Dar
In the companion paper, test results were presented to explore the flexural performance of cold-formed ferritic stainless steel (FSS) closed built-up beams. Each specimen was fabricated by joining two lipped channels in a face-to-face configuration and securing them with spot welds at intermediate points along the beam span. Sectional aspect ratio, compression flange’s sectional slenderness and moment gradient were the key parameters varied to explore their influence on the flexural response of such members through tests. The current paper establishes a simplified finite element (FE) model of cold-formed FSS closed built-up beams and verifies it against the test results. Further, an extensive parametric study is carried out using the validated FE model to generate a large pool of data points. A wider database comprising of test results, numerical results obtained from this study and numerical results available in the companion paper were used to critically examine the adequacy of the current Australian Specifications (AS/NZ), American Standard (SEI/ASCE-8), European Code (EN 1993-1-4), Modified Eurocode approach suggested by Gardner and Theofanous, and Direct Strength Method (DSM) in North American Specification (AISI-S100: 2016), Modified DSM approach proposed by the authors in the literature and Continuous Strength Method (CSM) for cold-formed steel (CFS) flexural members. This makes the current study the first to extensively assess the accuracy of the various design guidelines available in the codes and other relevant literature, which explicitly highlighted their grave limitations. Accordingly, through suitable modifications and recommendations, new design rules are proposed to reliably and safely predict the flexural capacity of cold-formed FSS closed built-up beams.
{"title":"Reliable design rules for cold-formed ferritic stainless steel closed built-up beams","authors":"C. Karthik, M. Anbarasu, M. A. Dar","doi":"10.1177/13694332241232046","DOIUrl":"https://doi.org/10.1177/13694332241232046","url":null,"abstract":"In the companion paper, test results were presented to explore the flexural performance of cold-formed ferritic stainless steel (FSS) closed built-up beams. Each specimen was fabricated by joining two lipped channels in a face-to-face configuration and securing them with spot welds at intermediate points along the beam span. Sectional aspect ratio, compression flange’s sectional slenderness and moment gradient were the key parameters varied to explore their influence on the flexural response of such members through tests. The current paper establishes a simplified finite element (FE) model of cold-formed FSS closed built-up beams and verifies it against the test results. Further, an extensive parametric study is carried out using the validated FE model to generate a large pool of data points. A wider database comprising of test results, numerical results obtained from this study and numerical results available in the companion paper were used to critically examine the adequacy of the current Australian Specifications (AS/NZ), American Standard (SEI/ASCE-8), European Code (EN 1993-1-4), Modified Eurocode approach suggested by Gardner and Theofanous, and Direct Strength Method (DSM) in North American Specification (AISI-S100: 2016), Modified DSM approach proposed by the authors in the literature and Continuous Strength Method (CSM) for cold-formed steel (CFS) flexural members. This makes the current study the first to extensively assess the accuracy of the various design guidelines available in the codes and other relevant literature, which explicitly highlighted their grave limitations. Accordingly, through suitable modifications and recommendations, new design rules are proposed to reliably and safely predict the flexural capacity of cold-formed FSS closed built-up beams.","PeriodicalId":505409,"journal":{"name":"Advances in Structural Engineering","volume":" 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-02-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139791779","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-02-08DOI: 10.1177/13694332241232046
C. Karthik, M. Anbarasu, M. A. Dar
In the companion paper, test results were presented to explore the flexural performance of cold-formed ferritic stainless steel (FSS) closed built-up beams. Each specimen was fabricated by joining two lipped channels in a face-to-face configuration and securing them with spot welds at intermediate points along the beam span. Sectional aspect ratio, compression flange’s sectional slenderness and moment gradient were the key parameters varied to explore their influence on the flexural response of such members through tests. The current paper establishes a simplified finite element (FE) model of cold-formed FSS closed built-up beams and verifies it against the test results. Further, an extensive parametric study is carried out using the validated FE model to generate a large pool of data points. A wider database comprising of test results, numerical results obtained from this study and numerical results available in the companion paper were used to critically examine the adequacy of the current Australian Specifications (AS/NZ), American Standard (SEI/ASCE-8), European Code (EN 1993-1-4), Modified Eurocode approach suggested by Gardner and Theofanous, and Direct Strength Method (DSM) in North American Specification (AISI-S100: 2016), Modified DSM approach proposed by the authors in the literature and Continuous Strength Method (CSM) for cold-formed steel (CFS) flexural members. This makes the current study the first to extensively assess the accuracy of the various design guidelines available in the codes and other relevant literature, which explicitly highlighted their grave limitations. Accordingly, through suitable modifications and recommendations, new design rules are proposed to reliably and safely predict the flexural capacity of cold-formed FSS closed built-up beams.
{"title":"Reliable design rules for cold-formed ferritic stainless steel closed built-up beams","authors":"C. Karthik, M. Anbarasu, M. A. Dar","doi":"10.1177/13694332241232046","DOIUrl":"https://doi.org/10.1177/13694332241232046","url":null,"abstract":"In the companion paper, test results were presented to explore the flexural performance of cold-formed ferritic stainless steel (FSS) closed built-up beams. Each specimen was fabricated by joining two lipped channels in a face-to-face configuration and securing them with spot welds at intermediate points along the beam span. Sectional aspect ratio, compression flange’s sectional slenderness and moment gradient were the key parameters varied to explore their influence on the flexural response of such members through tests. The current paper establishes a simplified finite element (FE) model of cold-formed FSS closed built-up beams and verifies it against the test results. Further, an extensive parametric study is carried out using the validated FE model to generate a large pool of data points. A wider database comprising of test results, numerical results obtained from this study and numerical results available in the companion paper were used to critically examine the adequacy of the current Australian Specifications (AS/NZ), American Standard (SEI/ASCE-8), European Code (EN 1993-1-4), Modified Eurocode approach suggested by Gardner and Theofanous, and Direct Strength Method (DSM) in North American Specification (AISI-S100: 2016), Modified DSM approach proposed by the authors in the literature and Continuous Strength Method (CSM) for cold-formed steel (CFS) flexural members. This makes the current study the first to extensively assess the accuracy of the various design guidelines available in the codes and other relevant literature, which explicitly highlighted their grave limitations. Accordingly, through suitable modifications and recommendations, new design rules are proposed to reliably and safely predict the flexural capacity of cold-formed FSS closed built-up beams.","PeriodicalId":505409,"journal":{"name":"Advances in Structural Engineering","volume":"12 3","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-02-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139851678","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-02-06DOI: 10.1177/13694332241232048
V. Cao, Sang Tan Ngo
This study investigated the residual axial strength of reinforced concrete (RC) columns after exposure to standard and non-standard fires. Experiments and theoretical analyses were performed on 30 RC columns, which were divided into five groups: one group (the control group) was not exposed to fire; two groups were exposed to 30-min and 45-min ISO 834 standard fires; and the other two groups were exposed to 60-min and 75-min non-standard fires. These postfire specimens were axially loaded until they failed. The experimental results showed that 30-min and 45-min ISO 834 fires decreased the residual strength by 11.6% and 17.4%, respectively. 60-min and 75-min non-ISO 834 fires caused similar reductions in the residual axial strength of postfire RC columns, although the durations of these non-standard fires were considerably longer. This experimental result confirmed that the maximum temperature, rather than the fire durations, of non-standard fires governed the reduction in the residual axial strength. In theoretical analysis, the axial strength of postfire RC columns can be calculated using the proposed model, which combines the confinement model, the 500°C isotherm method, and the distribution model of temperature. The proposed model can appropriately predict the residual axial strength of postfire columns when the fire closely follows the ISO 834 fire. The inaccuracy of the model significantly increases when the fires are non-ISO 834 fires. Two concepts, namely equivalent area and maximum temperature, were introduced to address the issue. The concept of maximum temperature successfully addressed the above-mentioned issue and exhibited superiority over the concept of equivalent area. This result reaffirmed the superior governing characteristic of the maximum temperature compared with the duration of non-standard fires, as evidenced in the experimental results. The proposed models would be useful for engineers in practice when evaluating the residual axial strength of both standard and non-standard postfire RC columns.
本研究调查了钢筋混凝土 (RC) 柱在遭受标准和非标准火灾后的残余轴向强度。研究人员对 30 根钢筋混凝土柱进行了实验和理论分析，并将其分为五组：一组（对照组）未遭受火灾；两组分别遭受 30 分钟和 45 分钟的 ISO 834 标准火灾；另外两组分别遭受 60 分钟和 75 分钟的非标准火灾。这些着火后试样被轴向加载直至失效。实验结果表明，30 分钟和 45 分钟的 ISO 834 火烧分别使残余强度降低了 11.6% 和 17.4%。60 分钟和 75 分钟的非 ISO 834 火灾对火灾后 RC 柱的残余轴向强度造成了类似的降低，尽管这些非标准火灾的持续时间要长得多。这一实验结果证实，非标准火灾的最高温度而非火灾持续时间决定了残余轴向强度的降低。在理论分析中，火灾后 RC 柱的轴向强度可通过所提出的模型进行计算，该模型结合了约束模型、500°C 等温线法和温度分布模型。当火灾紧跟 ISO 834 火灾时，所提出的模型可以适当预测火灾后柱的残余轴向强度。当火灾为非 ISO 834 火灾时，模型的不准确性会明显增加。为解决这一问题，引入了两个概念，即等效面积和最高温度。最高温度概念成功地解决了上述问题，并显示出优于等效面积概念。这一结果再次证实，与非标准火灾的持续时间相比，最高温度具有更优越的控制特性，实验结果也证明了这一点。所提出的模型将有助于工程师在实践中评估标准和非标准火灾后 RC 柱的残余轴向强度。
{"title":"Residual axial strength of reinforced concrete columns after exposure to standard and non-standard fires","authors":"V. Cao, Sang Tan Ngo","doi":"10.1177/13694332241232048","DOIUrl":"https://doi.org/10.1177/13694332241232048","url":null,"abstract":"This study investigated the residual axial strength of reinforced concrete (RC) columns after exposure to standard and non-standard fires. Experiments and theoretical analyses were performed on 30 RC columns, which were divided into five groups: one group (the control group) was not exposed to fire; two groups were exposed to 30-min and 45-min ISO 834 standard fires; and the other two groups were exposed to 60-min and 75-min non-standard fires. These postfire specimens were axially loaded until they failed. The experimental results showed that 30-min and 45-min ISO 834 fires decreased the residual strength by 11.6% and 17.4%, respectively. 60-min and 75-min non-ISO 834 fires caused similar reductions in the residual axial strength of postfire RC columns, although the durations of these non-standard fires were considerably longer. This experimental result confirmed that the maximum temperature, rather than the fire durations, of non-standard fires governed the reduction in the residual axial strength. In theoretical analysis, the axial strength of postfire RC columns can be calculated using the proposed model, which combines the confinement model, the 500°C isotherm method, and the distribution model of temperature. The proposed model can appropriately predict the residual axial strength of postfire columns when the fire closely follows the ISO 834 fire. The inaccuracy of the model significantly increases when the fires are non-ISO 834 fires. Two concepts, namely equivalent area and maximum temperature, were introduced to address the issue. The concept of maximum temperature successfully addressed the above-mentioned issue and exhibited superiority over the concept of equivalent area. This result reaffirmed the superior governing characteristic of the maximum temperature compared with the duration of non-standard fires, as evidenced in the experimental results. The proposed models would be useful for engineers in practice when evaluating the residual axial strength of both standard and non-standard postfire RC columns.","PeriodicalId":505409,"journal":{"name":"Advances in Structural Engineering","volume":"67 5","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-02-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139858497","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-02-06DOI: 10.1177/13694332241232048
V. Cao, Sang Tan Ngo
This study investigated the residual axial strength of reinforced concrete (RC) columns after exposure to standard and non-standard fires. Experiments and theoretical analyses were performed on 30 RC columns, which were divided into five groups: one group (the control group) was not exposed to fire; two groups were exposed to 30-min and 45-min ISO 834 standard fires; and the other two groups were exposed to 60-min and 75-min non-standard fires. These postfire specimens were axially loaded until they failed. The experimental results showed that 30-min and 45-min ISO 834 fires decreased the residual strength by 11.6% and 17.4%, respectively. 60-min and 75-min non-ISO 834 fires caused similar reductions in the residual axial strength of postfire RC columns, although the durations of these non-standard fires were considerably longer. This experimental result confirmed that the maximum temperature, rather than the fire durations, of non-standard fires governed the reduction in the residual axial strength. In theoretical analysis, the axial strength of postfire RC columns can be calculated using the proposed model, which combines the confinement model, the 500°C isotherm method, and the distribution model of temperature. The proposed model can appropriately predict the residual axial strength of postfire columns when the fire closely follows the ISO 834 fire. The inaccuracy of the model significantly increases when the fires are non-ISO 834 fires. Two concepts, namely equivalent area and maximum temperature, were introduced to address the issue. The concept of maximum temperature successfully addressed the above-mentioned issue and exhibited superiority over the concept of equivalent area. This result reaffirmed the superior governing characteristic of the maximum temperature compared with the duration of non-standard fires, as evidenced in the experimental results. The proposed models would be useful for engineers in practice when evaluating the residual axial strength of both standard and non-standard postfire RC columns.
本研究调查了钢筋混凝土 (RC) 柱在遭受标准和非标准火灾后的残余轴向强度。研究人员对 30 根钢筋混凝土柱进行了实验和理论分析，并将其分为五组：一组（对照组）未遭受火灾；两组分别遭受 30 分钟和 45 分钟的 ISO 834 标准火灾；另外两组分别遭受 60 分钟和 75 分钟的非标准火灾。这些着火后试样被轴向加载直至失效。实验结果表明，30 分钟和 45 分钟的 ISO 834 火烧分别使残余强度降低了 11.6% 和 17.4%。60 分钟和 75 分钟的非 ISO 834 火灾对火灾后 RC 柱的残余轴向强度造成了类似的降低，尽管这些非标准火灾的持续时间要长得多。这一实验结果证实，非标准火灾的最高温度而非火灾持续时间决定了残余轴向强度的降低。在理论分析中，火灾后 RC 柱的轴向强度可通过所提出的模型进行计算，该模型结合了约束模型、500°C 等温线法和温度分布模型。当火灾紧跟 ISO 834 火灾时，所提出的模型可以适当预测火灾后柱的残余轴向强度。当火灾为非 ISO 834 火灾时，模型的不准确性会明显增加。为解决这一问题，引入了两个概念，即等效面积和最高温度。最高温度概念成功地解决了上述问题，并显示出优于等效面积概念。这一结果再次证实，与非标准火灾的持续时间相比，最高温度具有更优越的控制特性，实验结果也证明了这一点。所提出的模型将有助于工程师在实践中评估标准和非标准火灾后 RC 柱的残余轴向强度。
{"title":"Residual axial strength of reinforced concrete columns after exposure to standard and non-standard fires","authors":"V. Cao, Sang Tan Ngo","doi":"10.1177/13694332241232048","DOIUrl":"https://doi.org/10.1177/13694332241232048","url":null,"abstract":"This study investigated the residual axial strength of reinforced concrete (RC) columns after exposure to standard and non-standard fires. Experiments and theoretical analyses were performed on 30 RC columns, which were divided into five groups: one group (the control group) was not exposed to fire; two groups were exposed to 30-min and 45-min ISO 834 standard fires; and the other two groups were exposed to 60-min and 75-min non-standard fires. These postfire specimens were axially loaded until they failed. The experimental results showed that 30-min and 45-min ISO 834 fires decreased the residual strength by 11.6% and 17.4%, respectively. 60-min and 75-min non-ISO 834 fires caused similar reductions in the residual axial strength of postfire RC columns, although the durations of these non-standard fires were considerably longer. This experimental result confirmed that the maximum temperature, rather than the fire durations, of non-standard fires governed the reduction in the residual axial strength. In theoretical analysis, the axial strength of postfire RC columns can be calculated using the proposed model, which combines the confinement model, the 500°C isotherm method, and the distribution model of temperature. The proposed model can appropriately predict the residual axial strength of postfire columns when the fire closely follows the ISO 834 fire. The inaccuracy of the model significantly increases when the fires are non-ISO 834 fires. Two concepts, namely equivalent area and maximum temperature, were introduced to address the issue. The concept of maximum temperature successfully addressed the above-mentioned issue and exhibited superiority over the concept of equivalent area. This result reaffirmed the superior governing characteristic of the maximum temperature compared with the duration of non-standard fires, as evidenced in the experimental results. The proposed models would be useful for engineers in practice when evaluating the residual axial strength of both standard and non-standard postfire RC columns.","PeriodicalId":505409,"journal":{"name":"Advances in Structural Engineering","volume":"33 20","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-02-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139798435","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-02-05DOI: 10.1177/13694332241232052
Yu-peng Chen, Wenmin Zhang
The application of a composite saddle in single-tower earth-anchored suspension bridges (STEASBs) replaces the tower on the steep slope side, which is a cost-effective solution that improves bridge safety and provides environmental protection for the steep bank slope of the valley. However, this novel bridge design needs an appropriate model to evaluate the effect of rock anchor hangers on the structure in the non-girder area and adjust their parameters to optimize the mechanical response of the whole bridge structure. This study proposes an approach to quickly evaluate the most unfavorable load cases of the STEASB and further optimizes the structural parameters of rock anchor hangers to enhance structural safety. An analytical model for the STEASBs under the live load is proposed and verified by the finite element model (FEM), with the maximum relative error not exceeding 7.37%. Combined with the golden eagle optimizer (GEO), the most unfavorable load cases of the corresponding design indices are yielded. The Pareto optimal solutions for the spacing, cross-sectional area, and initial tension of the vertical rock anchor hangers are obtained through multi-objective optimization to improve the mechanical behavior of STEASBs. In addition, it is clarified that the main function of rock anchor hangers is to reduce the peak value of the stress amplitude of the hangers and girder-end rotation, providing a theoretical basis for the STEASB design.
{"title":"Rock anchor hanger effect on single-tower earth-anchored suspension bridge mechanical performance: An analytical model and multi-objective golden eagle optimization","authors":"Yu-peng Chen, Wenmin Zhang","doi":"10.1177/13694332241232052","DOIUrl":"https://doi.org/10.1177/13694332241232052","url":null,"abstract":"The application of a composite saddle in single-tower earth-anchored suspension bridges (STEASBs) replaces the tower on the steep slope side, which is a cost-effective solution that improves bridge safety and provides environmental protection for the steep bank slope of the valley. However, this novel bridge design needs an appropriate model to evaluate the effect of rock anchor hangers on the structure in the non-girder area and adjust their parameters to optimize the mechanical response of the whole bridge structure. This study proposes an approach to quickly evaluate the most unfavorable load cases of the STEASB and further optimizes the structural parameters of rock anchor hangers to enhance structural safety. An analytical model for the STEASBs under the live load is proposed and verified by the finite element model (FEM), with the maximum relative error not exceeding 7.37%. Combined with the golden eagle optimizer (GEO), the most unfavorable load cases of the corresponding design indices are yielded. The Pareto optimal solutions for the spacing, cross-sectional area, and initial tension of the vertical rock anchor hangers are obtained through multi-objective optimization to improve the mechanical behavior of STEASBs. In addition, it is clarified that the main function of rock anchor hangers is to reduce the peak value of the stress amplitude of the hangers and girder-end rotation, providing a theoretical basis for the STEASB design.","PeriodicalId":505409,"journal":{"name":"Advances in Structural Engineering","volume":"7 7","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-02-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139806198","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
京公网安备 11010802042870号
京ICP备2023020795号-1
扫码关注我们
求助内容：
应助结果提醒方式：