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The Top 20 Most-Cited Papers from 2022 to 2023
Current Issue
2024 Vol. 39, No. 7
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2024, 39(7): 1-9.
doi: 10.13206/j.gjgS22120201
Abstract
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Abstract:
In order to study the failure probability of the high-strength CFST-aluminum alloy core assembled buckling-restrained braces (HSCSB-ALAB) under different intensity of ground motion, based on the incremental dynamic analysis (IDA) method, the near-field pulse ground motion, far-field ground motion, near-field ground motion and integrated ground motion were selected. The seismic fragility of a 10 story HSC-SB-ALAB is analyzed by using four groups of 45 strong motion records. The fragility curves of the structure under four earthquake types are obtained; the probability of reaching each limit state of the structure under frequent earthquake, fortified earthquake and rare earthquake is given; and the collapse margin ratio of the structure is calculated and evaluated.
The results show that the probability of reaching each limit state is the largest under the action of near-field impulse ground motion, and the exceeding probability is the smallest under the action of far-field earthquake. Under the action of various types of ground motions, the collapse probability of the structure is only about 1%, which meets the seismic fortification goal of "no damage in small earthquake, repairable in medium earthquake and no collapse in large earthquake". The collapse reserve coefficient is greater than the minimum value of 2. 47 required in FEMA P695, which is 1. 34-1. 43 times that of other types of concrete-filled steel tubular structures.
In order to study the failure probability of the high-strength CFST-aluminum alloy core assembled buckling-restrained braces (HSCSB-ALAB) under different intensity of ground motion, based on the incremental dynamic analysis (IDA) method, the near-field pulse ground motion, far-field ground motion, near-field ground motion and integrated ground motion were selected. The seismic fragility of a 10 story HSC-SB-ALAB is analyzed by using four groups of 45 strong motion records. The fragility curves of the structure under four earthquake types are obtained; the probability of reaching each limit state of the structure under frequent earthquake, fortified earthquake and rare earthquake is given; and the collapse margin ratio of the structure is calculated and evaluated.
The results show that the probability of reaching each limit state is the largest under the action of near-field impulse ground motion, and the exceeding probability is the smallest under the action of far-field earthquake. Under the action of various types of ground motions, the collapse probability of the structure is only about 1%, which meets the seismic fortification goal of "no damage in small earthquake, repairable in medium earthquake and no collapse in large earthquake". The collapse reserve coefficient is greater than the minimum value of 2. 47 required in FEMA P695, which is 1. 34-1. 43 times that of other types of concrete-filled steel tubular structures.
2024, 39(7): 10-18.
doi: 10.13206/j.gjgS23112802
Abstract:
Concrete-filled steel tubular(CFST) structures can give full play to the advantages of both concrete and steel materials, and have been widely used in commercial and public buildings. With the implementation of the prefabricated building policy in recent years, CFST columns with rectangular section are getting more and more attention in residential projects due to its advantages of excellent bearing capacity and simple joint structure. Compared with commercial and public buildings. residential steel structures have higher requirements for the effective use of building interior space (avoid " convex beams and columns" ) and economy (reduce the amount of steel used). In order to meet these requirements, the section of the rectangular concrete-filled steel tube column in the residential steel structure generally has a large aspect ratio, and the width to thickness ratio of the plate is as large as possible. Currently, the sectional aspect ratio of rectangular CFST column has reached about 3. 3 in the application of engineering, lager than the common range(no more than 2. 0). The local buckling of steel tubes is the one of the most important failure modes of CFST column, which will cause the significant decrease of bearing capacity of CFST column and affect the residual bearing capacity of the specimens. The limit of width-tothickness ratio is recommended in specifications for preventing the local buckling. Therefore, it is necessary to pay attention to the width-to-thickness ratio of CFST columns. However, there is difference of the limitation of width-to-thickness ratio between Chinese code and foreign codes. Meanwhile, the limit of width / thickness ratio of the existing code is mainly based on the study of the component whose section aspect ratio is not more than 2. 0, and for residential steel structure should be used in a wide range of aspect ratio greater than 2. 0 of the wide applicability of the concrete filled steel tube column need further research.
The limit of sectional width-to-thickness ratio of rectangular CFST column is studied by finite element(FE) analysis. Based on the confined concrete constitutive model and concrete damage plastic(CDP) model, considering the effects of section height to width ratio restraint cross section aspect ratio coefficient. FE model of rectangular CFST column is established for analyzing the members with large aspect ratio. The accuracy of the FE model is verified by comparing with the test. Through the parameter analysis, considering the influence of sectional aspect ratio, width-to-thickness ratio, steel strength and concrete strength on the ultimate bearing capacity of rectangular CFST columns, the limit of sectional width-to-thickness ratio of rectangular CFST columns is analyzed. The limits of sectional width-to-thickness ratio of rectangular CFST column in codes are introduced, and the analysis result is compared with the limit in codes. By defining the normalized ultimate bearing capacity coefficient and taking the turning point of the curve of the ultimate load as the basis to determine the limit of width-to-thickness ratio of the steel tube, it is found that the steel strength and concrete strength are negatively correlated and positively correlated with the ultimate bearing capacity of the specimens, respectively. But effect of section width-to-thickness ratio on the ultimate bearing capacity is more critical. The results show that the limit of width-to-thickness ratio of rectangular CFST columns is about 50√235/fy, which is close to the recommendation values of AIJ, EC4 and BS5400, but obviously smaller than the limits of GB 50936, CECS 159, GJ / B 4142, DBJ / T 13-51 and AISC 360.
Concrete-filled steel tubular(CFST) structures can give full play to the advantages of both concrete and steel materials, and have been widely used in commercial and public buildings. With the implementation of the prefabricated building policy in recent years, CFST columns with rectangular section are getting more and more attention in residential projects due to its advantages of excellent bearing capacity and simple joint structure. Compared with commercial and public buildings. residential steel structures have higher requirements for the effective use of building interior space (avoid " convex beams and columns" ) and economy (reduce the amount of steel used). In order to meet these requirements, the section of the rectangular concrete-filled steel tube column in the residential steel structure generally has a large aspect ratio, and the width to thickness ratio of the plate is as large as possible. Currently, the sectional aspect ratio of rectangular CFST column has reached about 3. 3 in the application of engineering, lager than the common range(no more than 2. 0). The local buckling of steel tubes is the one of the most important failure modes of CFST column, which will cause the significant decrease of bearing capacity of CFST column and affect the residual bearing capacity of the specimens. The limit of width-tothickness ratio is recommended in specifications for preventing the local buckling. Therefore, it is necessary to pay attention to the width-to-thickness ratio of CFST columns. However, there is difference of the limitation of width-to-thickness ratio between Chinese code and foreign codes. Meanwhile, the limit of width / thickness ratio of the existing code is mainly based on the study of the component whose section aspect ratio is not more than 2. 0, and for residential steel structure should be used in a wide range of aspect ratio greater than 2. 0 of the wide applicability of the concrete filled steel tube column need further research.
The limit of sectional width-to-thickness ratio of rectangular CFST column is studied by finite element(FE) analysis. Based on the confined concrete constitutive model and concrete damage plastic(CDP) model, considering the effects of section height to width ratio restraint cross section aspect ratio coefficient. FE model of rectangular CFST column is established for analyzing the members with large aspect ratio. The accuracy of the FE model is verified by comparing with the test. Through the parameter analysis, considering the influence of sectional aspect ratio, width-to-thickness ratio, steel strength and concrete strength on the ultimate bearing capacity of rectangular CFST columns, the limit of sectional width-to-thickness ratio of rectangular CFST columns is analyzed. The limits of sectional width-to-thickness ratio of rectangular CFST column in codes are introduced, and the analysis result is compared with the limit in codes. By defining the normalized ultimate bearing capacity coefficient and taking the turning point of the curve of the ultimate load as the basis to determine the limit of width-to-thickness ratio of the steel tube, it is found that the steel strength and concrete strength are negatively correlated and positively correlated with the ultimate bearing capacity of the specimens, respectively. But effect of section width-to-thickness ratio on the ultimate bearing capacity is more critical. The results show that the limit of width-to-thickness ratio of rectangular CFST columns is about 50√235/fy, which is close to the recommendation values of AIJ, EC4 and BS5400, but obviously smaller than the limits of GB 50936, CECS 159, GJ / B 4142, DBJ / T 13-51 and AISC 360.
2024, 39(7): 19-28.
doi: 10.13206/j.gjgS23112901
Abstract:
Hollow concrete filled steel tube is a composite material with excellent performance, widely used in engineering structures such as buildings, bridges, and tunnels. Compared with circular concrete filled steel tube columns, rectangular concrete filled steel tube columns have advantages such as convenient construction and simple node structure. However, research has shown that compared with circular hollow concrete filled steel tube, rectangular members have lower composite strength and poorer ductility. Reinforcement and reinforcement measures can effectively enhance the strength and ductility of composite columns. PHC tubular pile is a hollow circular reinforced concrete prefabricated member made by pre tensioning and centrifugal molding technology and steam curing. The built-in longitudinal bars can improve the bending performance of the tubular pile, and the spiral hoop bars can improve the ductility of the structure. Its single pile bearing capacity is high, the cost is low, and its application range is very wide. This article proposes a new type of composite member-ribbed reinforced hollow square concrete filled steel tube-by placing PHC pile into ribbed steel tube and pouring sandwich concrete afterwards. Previous studies have shown that the wall thickness and width to thickness ratio of the steel tube have the most significant impact on the axial compressive bearing capacity of such composite members.
To study the axial compression performance of reinforced hollow square steel tube high-strength concrete short columns with ribs, this paper conducted finite element simulations on 18 reinforced concrete filled steel tube members with ribs and steel tube wall thickness as variable parameters including the number of stiffeners and the thickness of steel tube. The results were compared with existing experimental results, and the load displacement curves were well fitted. The finite element analysis results indicate that the stress process of the member can be divided into elastic stage, elastic-plastic stage, plastic strengthening stage, and descending stage. The influence of stiffeners on the axial compressive mechanical properties of the member is manifested in all four stages. Stiffening ribs can effectively suppress local buckling of steel tubes, allowing them to share more axial loads and fully utilize the axial compression performance of the steel. Research has shown that compared to non stiffener members, the ultimate bearing capacity of single-stiffener members has significantly improved. Continuing to increase the number of stiffeners will further enhance the ultimate bearing capacity of the member, but the increase is relatively small. The steel tubes in members with stiffeners will share the internal force and reach the peak earlier, and the share internal force displacement curve will enter the descending stage, while the steel tubes in members without stiffeners will share the internal force and reach the peak later, and the share internal force displacement curve will not have a significant descending segment, indicating that the steel tubes in members with stiffeners can bear more axial loads in the later stage of loading, thereby improving the ductility of the members. Compared to increasing the wall thickness of steel tubes, adopting reasonable reinforcement measures can more effectively enhance the bearing capacity of composite members and save more steel. At the end of this article, a formula for the axial compressive bearing capacity of reinforced hollow square concrete filled steel tube short columns with ribs is provided, and the calculation results have errors within 5% and tend to be conservative.
Hollow concrete filled steel tube is a composite material with excellent performance, widely used in engineering structures such as buildings, bridges, and tunnels. Compared with circular concrete filled steel tube columns, rectangular concrete filled steel tube columns have advantages such as convenient construction and simple node structure. However, research has shown that compared with circular hollow concrete filled steel tube, rectangular members have lower composite strength and poorer ductility. Reinforcement and reinforcement measures can effectively enhance the strength and ductility of composite columns. PHC tubular pile is a hollow circular reinforced concrete prefabricated member made by pre tensioning and centrifugal molding technology and steam curing. The built-in longitudinal bars can improve the bending performance of the tubular pile, and the spiral hoop bars can improve the ductility of the structure. Its single pile bearing capacity is high, the cost is low, and its application range is very wide. This article proposes a new type of composite member-ribbed reinforced hollow square concrete filled steel tube-by placing PHC pile into ribbed steel tube and pouring sandwich concrete afterwards. Previous studies have shown that the wall thickness and width to thickness ratio of the steel tube have the most significant impact on the axial compressive bearing capacity of such composite members.
To study the axial compression performance of reinforced hollow square steel tube high-strength concrete short columns with ribs, this paper conducted finite element simulations on 18 reinforced concrete filled steel tube members with ribs and steel tube wall thickness as variable parameters including the number of stiffeners and the thickness of steel tube. The results were compared with existing experimental results, and the load displacement curves were well fitted. The finite element analysis results indicate that the stress process of the member can be divided into elastic stage, elastic-plastic stage, plastic strengthening stage, and descending stage. The influence of stiffeners on the axial compressive mechanical properties of the member is manifested in all four stages. Stiffening ribs can effectively suppress local buckling of steel tubes, allowing them to share more axial loads and fully utilize the axial compression performance of the steel. Research has shown that compared to non stiffener members, the ultimate bearing capacity of single-stiffener members has significantly improved. Continuing to increase the number of stiffeners will further enhance the ultimate bearing capacity of the member, but the increase is relatively small. The steel tubes in members with stiffeners will share the internal force and reach the peak earlier, and the share internal force displacement curve will enter the descending stage, while the steel tubes in members without stiffeners will share the internal force and reach the peak later, and the share internal force displacement curve will not have a significant descending segment, indicating that the steel tubes in members with stiffeners can bear more axial loads in the later stage of loading, thereby improving the ductility of the members. Compared to increasing the wall thickness of steel tubes, adopting reasonable reinforcement measures can more effectively enhance the bearing capacity of composite members and save more steel. At the end of this article, a formula for the axial compressive bearing capacity of reinforced hollow square concrete filled steel tube short columns with ribs is provided, and the calculation results have errors within 5% and tend to be conservative.
2024, 39(7): 29-37.
doi: 10.13206/j.gjgS23102102
Abstract:
Carbon fiber reinforced polymer (CFRP) has the characteristics of high-strength and good corrosion resistance. Encased I-shaped CFRP profile into concrete-filled square steel tubular structure (CFRP-CFSST) forming a new-typed composite member can not only improve the mechanical properties of the member, but also reduce the material consumption, the dead weight of the structure and the cross-sectional size of the member. It is more suitable for super high-rise, large-span and heavy-load structures. As a critical lateral force-resisting member in structures, CFST often determines the seismic performance of the whole structure when subjected to an earthquake, which is directly related to the safety of people's lives and property. At present, the relevant design codes and standards around the world are not suitable for the seismic design of new composite members, so it is necessary to carry out in-depth research on its seismic performance.
In this paper, finite element analysis software, ABAQUS, was used to study the seismic performance of the flexural behavior of CFRP-CFSST pure bending members. Firstly, considering the accuracy and applicability, the finite element model was verified with the existing literature, and a large number of refined models of CFRP-CFSST pure bending members were established based on the verified model. Then, on this basis, the whole process of stress analysis and stress analysis of each component at characteristic points were carried out based on the typical member. Finally, the effects of concrete compressive strength, steel yield strength and steel ratio on the flexural capacity and energy dissipation capacity of CFRP-CFSST pure bending members were studied.
The simulation results indicated that the load-displacement envelope curves of the CFRP-CFSST pure bending member can be defined as three stages: elastic stage, elastoplastic stage and descending stage. Through the whole process analysis of typical members, in the elastic stage and elastoplastic stage, the load is mainly borne by the steel tube compared to the core concrete and I-shaped CFRP profiles. In the descending section, the load-bearing ratio of the CFRP profile increases, which shows that the encased CFRP profile can effectively improve the bearing capacity and ductility of members in the later loading stage. Therefore, compared with ordinary CFST members, the better tensile performance of CFRP profile efficiently improves the flexural performance of new composite members. Based on the parametric analysis results, the steel ratio has a significant effect on the bearing capacity and energy dissipation capacity of CFRP-CFSST members. When the steel tube thickness increases from 4 mm to 7 mm with an increment of 1 mm, the flexural bearing capacity of CFRP-CFSST members increases by 13. 83%, 8. 99% and 9. 10% respectively, which shows that a 5 mm steel tube thickness is most economic and the cumulative energy dissipation capacities increased by about 16. 57% on average. The steel tube is the main component that bears pure flexural load in the whole loading process, and the change in its strength also has a great influence on the hysteretic behavior of the members. When the steel strength increases from Q235 to Q420, the flexural bearing capacity of the members rises by about 30. 13%, the cumulative energy dissipation increases by about 12. 45%, and the flexural bearing capacity increases linearly with the increasing strength. The compressive strength of core concrete has a minor influence on the bearing capacity and energy dissipation capacity of members, and with the increase of concrete strength, the increase of flexural bearing capacity gradually decreases. When it is increased from C30 to C60, its cumulative energy dissipation capacities only increase by about 3. 44% . Therefore, compared with ordinary CFST members, CFRP-CFSST members have a better seismic performance, and most economic measures recommended are to improve the bearing capacity of new composite members by increasing the steel yield strength or steel ratio.
Carbon fiber reinforced polymer (CFRP) has the characteristics of high-strength and good corrosion resistance. Encased I-shaped CFRP profile into concrete-filled square steel tubular structure (CFRP-CFSST) forming a new-typed composite member can not only improve the mechanical properties of the member, but also reduce the material consumption, the dead weight of the structure and the cross-sectional size of the member. It is more suitable for super high-rise, large-span and heavy-load structures. As a critical lateral force-resisting member in structures, CFST often determines the seismic performance of the whole structure when subjected to an earthquake, which is directly related to the safety of people's lives and property. At present, the relevant design codes and standards around the world are not suitable for the seismic design of new composite members, so it is necessary to carry out in-depth research on its seismic performance.
In this paper, finite element analysis software, ABAQUS, was used to study the seismic performance of the flexural behavior of CFRP-CFSST pure bending members. Firstly, considering the accuracy and applicability, the finite element model was verified with the existing literature, and a large number of refined models of CFRP-CFSST pure bending members were established based on the verified model. Then, on this basis, the whole process of stress analysis and stress analysis of each component at characteristic points were carried out based on the typical member. Finally, the effects of concrete compressive strength, steel yield strength and steel ratio on the flexural capacity and energy dissipation capacity of CFRP-CFSST pure bending members were studied.
The simulation results indicated that the load-displacement envelope curves of the CFRP-CFSST pure bending member can be defined as three stages: elastic stage, elastoplastic stage and descending stage. Through the whole process analysis of typical members, in the elastic stage and elastoplastic stage, the load is mainly borne by the steel tube compared to the core concrete and I-shaped CFRP profiles. In the descending section, the load-bearing ratio of the CFRP profile increases, which shows that the encased CFRP profile can effectively improve the bearing capacity and ductility of members in the later loading stage. Therefore, compared with ordinary CFST members, the better tensile performance of CFRP profile efficiently improves the flexural performance of new composite members. Based on the parametric analysis results, the steel ratio has a significant effect on the bearing capacity and energy dissipation capacity of CFRP-CFSST members. When the steel tube thickness increases from 4 mm to 7 mm with an increment of 1 mm, the flexural bearing capacity of CFRP-CFSST members increases by 13. 83%, 8. 99% and 9. 10% respectively, which shows that a 5 mm steel tube thickness is most economic and the cumulative energy dissipation capacities increased by about 16. 57% on average. The steel tube is the main component that bears pure flexural load in the whole loading process, and the change in its strength also has a great influence on the hysteretic behavior of the members. When the steel strength increases from Q235 to Q420, the flexural bearing capacity of the members rises by about 30. 13%, the cumulative energy dissipation increases by about 12. 45%, and the flexural bearing capacity increases linearly with the increasing strength. The compressive strength of core concrete has a minor influence on the bearing capacity and energy dissipation capacity of members, and with the increase of concrete strength, the increase of flexural bearing capacity gradually decreases. When it is increased from C30 to C60, its cumulative energy dissipation capacities only increase by about 3. 44% . Therefore, compared with ordinary CFST members, CFRP-CFSST members have a better seismic performance, and most economic measures recommended are to improve the bearing capacity of new composite members by increasing the steel yield strength or steel ratio.
2024, 39(7): 38-46.
doi: 10.13206/j.gjgS23110202
Abstract:
Wood is widely used in engineering because of its high load-bearing capacity, green and renewable. In order to reduce the amount of concrete in steel pipe concrete members, and reduce structural weight, the wood is placed in the steel pipe concrete, to form the steel pipe-wood-concrete members. Since the pure bending member is the foundation of the compression bending member and the auxiliary of the compression bending member, the study of the mechanical properties of the pure bending member is of great significance. Reasonable selection of steel, concrete, wood of the constitutive model, this paper uses ABAQUS software to establish a square steel pipe-wood-concrete pure bending member refined analysis model, analyzing the typical member of the stress and neutral axis height change rule, revealing the square steel pipe-wood-concrete pure bending member of the working mechanism. On this basis, the influence of different steel yield strength, steel content rate, concrete compressive strength, wood core cross-section form, wood configuration rate on the flexural performance of the member was studied.
The results indicate that substituting wood for core concrete in the steel tube-wood-concrete members can enhance their flexural capacity and ductility. Additionally, it leads to a 16% reduction in the overall weight of the structure, and its strength-to-weight ratio is significantly increased. When the yield strength of steel components is increased from 235 MPa to 420 MPa, the flexural capacity can be increased by 35. 4%-63. 5%, and the ductility coefficient can be increased by 5. 5%-13%. When the steel content is increased from 8. 5% to 18. 1%, the flexural capacity can be increased by 24. 5% to 71. 4%, and the ductility coefficient can be increased by 4.8% to 16%. The increase of concrete strength has no significant effect on the flexural performance of the members, but it reduces the ductility of the members. The bending capacity of wood increased from 18. 1% to 100%, and the ductility coefficient increased by 5. 4% to 18. 8%. Wood is more likely to play a role when the allocation rate is 8. 1% to 32. 7%. Therefore, when the ratio of wood is 8. 1%-32. 7%, by increasing the yield strength and steel content of the steel component, the ductility and flexural capacity of the composite members can be further enhanced.
Wood is widely used in engineering because of its high load-bearing capacity, green and renewable. In order to reduce the amount of concrete in steel pipe concrete members, and reduce structural weight, the wood is placed in the steel pipe concrete, to form the steel pipe-wood-concrete members. Since the pure bending member is the foundation of the compression bending member and the auxiliary of the compression bending member, the study of the mechanical properties of the pure bending member is of great significance. Reasonable selection of steel, concrete, wood of the constitutive model, this paper uses ABAQUS software to establish a square steel pipe-wood-concrete pure bending member refined analysis model, analyzing the typical member of the stress and neutral axis height change rule, revealing the square steel pipe-wood-concrete pure bending member of the working mechanism. On this basis, the influence of different steel yield strength, steel content rate, concrete compressive strength, wood core cross-section form, wood configuration rate on the flexural performance of the member was studied.
The results indicate that substituting wood for core concrete in the steel tube-wood-concrete members can enhance their flexural capacity and ductility. Additionally, it leads to a 16% reduction in the overall weight of the structure, and its strength-to-weight ratio is significantly increased. When the yield strength of steel components is increased from 235 MPa to 420 MPa, the flexural capacity can be increased by 35. 4%-63. 5%, and the ductility coefficient can be increased by 5. 5%-13%. When the steel content is increased from 8. 5% to 18. 1%, the flexural capacity can be increased by 24. 5% to 71. 4%, and the ductility coefficient can be increased by 4.8% to 16%. The increase of concrete strength has no significant effect on the flexural performance of the members, but it reduces the ductility of the members. The bending capacity of wood increased from 18. 1% to 100%, and the ductility coefficient increased by 5. 4% to 18. 8%. Wood is more likely to play a role when the allocation rate is 8. 1% to 32. 7%. Therefore, when the ratio of wood is 8. 1%-32. 7%, by increasing the yield strength and steel content of the steel component, the ductility and flexural capacity of the composite members can be further enhanced.
2024, 39(7): 47-54.
doi: 10.13206/j.gjgS23111502
Abstract:
Localized pitting corrosion damage can cause an adverse impact on the safety of concrete-filled steel tubes (CFST). This paper conducted a numerical analysis of the axial compression performance of slender CFST with pitting corrosion damage. The failure phenomenon and load-deformation relationships from the existing tests were used to verify the numerical models. Then, the verified models were extended to take the random characteristics of corrosion pits in the aspect of distribution, dimensions, and locations into account. The influence of the degree of local volume loss, material strength, and slenderness ratio on the load-deflection curves was analyzed. According to the same degree of local volume loss, the CFST with equivalent thickness loss was established. The different influences of pitting corrosion and equivalent local defect on the ultimate strength were compared. Finally, based on the equivalent thickness loss, three methods based on the Chinese codes were put forward and to calculate the axial compression performance of CFST column with pitting corrosion damage and compare with the result of FE analysis.
The results show that the influence caused by different distributions of corrosion depth could be ignored. Compared with the equivalent local defect, the pitting corrosion can have a greater decrease in the ultimate strength of the slender CFST. According to the degree of local volume loss, the methods based on GB 50936- 2014 could predict the ultimate strength of CFST with pitting corrosion damage, and the method based on GB 50936-2014 could provide a prediction with good accuracy and moderate consideration.
Localized pitting corrosion damage can cause an adverse impact on the safety of concrete-filled steel tubes (CFST). This paper conducted a numerical analysis of the axial compression performance of slender CFST with pitting corrosion damage. The failure phenomenon and load-deformation relationships from the existing tests were used to verify the numerical models. Then, the verified models were extended to take the random characteristics of corrosion pits in the aspect of distribution, dimensions, and locations into account. The influence of the degree of local volume loss, material strength, and slenderness ratio on the load-deflection curves was analyzed. According to the same degree of local volume loss, the CFST with equivalent thickness loss was established. The different influences of pitting corrosion and equivalent local defect on the ultimate strength were compared. Finally, based on the equivalent thickness loss, three methods based on the Chinese codes were put forward and to calculate the axial compression performance of CFST column with pitting corrosion damage and compare with the result of FE analysis.
The results show that the influence caused by different distributions of corrosion depth could be ignored. Compared with the equivalent local defect, the pitting corrosion can have a greater decrease in the ultimate strength of the slender CFST. According to the degree of local volume loss, the methods based on GB 50936- 2014 could predict the ultimate strength of CFST with pitting corrosion damage, and the method based on GB 50936-2014 could provide a prediction with good accuracy and moderate consideration.
2024, 39(7): 55-57.
doi: 10.13206/j.gjgS24031920
Abstract:
Using the strong connection factors and the pre-established position of the plastic hinges of framed beam given in JGJ 99-2015, the strength demand on the column face is derived, from which the upper limit of the length of the cover plate is determined, and the required area of the cover plates is computed. An example shows that when the frame column using rectangular steel tube, the required area is about 25%-30% of the flange area of the beam. For short beams, the code-specified strong joint factor of JGJ 99-2015 is not great enough, the paper presented a equation to compute required strong joint factor higher than that of JGJ 99-2015.
Using the strong connection factors and the pre-established position of the plastic hinges of framed beam given in JGJ 99-2015, the strength demand on the column face is derived, from which the upper limit of the length of the cover plate is determined, and the required area of the cover plates is computed. An example shows that when the frame column using rectangular steel tube, the required area is about 25%-30% of the flange area of the beam. For short beams, the code-specified strong joint factor of JGJ 99-2015 is not great enough, the paper presented a equation to compute required strong joint factor higher than that of JGJ 99-2015.
