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Steel Construction Published the List of Highly Influential Articles of 2020
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2024 Vol. 39, No. 12
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2024, 39(12): 1-11.
doi: 10.13206/j.gjgS24110501
Abstract:
The performance-based seismic design (PBSD) method transforms the qualitative structural seismic precaution objectives of traditional code-based design methods into multi-level performance objectives which can be quantitatively comalyzed. Based on the numerical simulation analysis, the structural performance accuratery evaluated and targeted seismic measures are ernployed to meet specific structural demands. This method is particularly suitable for out-of-code structures and high-performance design where traditional methods are insufficient to optimize structural performance. The paper introduted a stratified and classified PBSD method, which was developed by the authors’ team through extensive research on performance-based seismic design, component performance evaluation criteria, and engineering applications. The method’s key procedures include defining seismic precaution objectives, conceptual design, performance objective setting, structural analysis, and performance evaluation. The approach emphasizes stratification and classification to refine structural and component performance objectives, integrates elasto-plastic analysis into seismic measures, and uses performance evaluation results as a foundation for design decisions, ensuring alignment with specified performance goals. A multi-storey steel concentrically braced frame located in a high seismic intensity zone was taken as a case study to illustrate the practical application of the proposed method, and the engineering applications of the stratified and classified performance-based seismic design method were discussed as well as its differences from the traditional design methods in codes. The design process began with conceptual design, performance objective setting, and preliminary design based on the "weak brace" concept. Structural analysis, performance evaluation, and design adjustments were iteratively optimized by using computational algorithms to minimize steel usage in primary components. The optimization ensured compliance with predefined performance criteria, including structural drifts, stress ratios of components, and damage grades. The results demonstrated that, compared to the original schemes based on the traditional seismic design methods in codes, in the scheme designed by the stratified and classified performance-based seismic design method, the cross sections of braces decreased significantly, while those of columns connected to braces increased. The steel usage in primary components was reduced by 23%. Furthermore, the scheme designed by the proposed method reduced structural drifts and the maximum total seismic input energy, increased plastic deformation energy dissipation, effectively minimized the damages of vertical components, and distributed the damage of braces more uniformly under rarely occurred earthquake, resulting in a more efficient and resilient energy dissipation system. In conclusion, the proposed stratified and classified PBSD method delivers superior seismic performance while optimizing material usage, demonstrating its potential for efficient and resilient structural design.
The performance-based seismic design (PBSD) method transforms the qualitative structural seismic precaution objectives of traditional code-based design methods into multi-level performance objectives which can be quantitatively comalyzed. Based on the numerical simulation analysis, the structural performance accuratery evaluated and targeted seismic measures are ernployed to meet specific structural demands. This method is particularly suitable for out-of-code structures and high-performance design where traditional methods are insufficient to optimize structural performance. The paper introduted a stratified and classified PBSD method, which was developed by the authors’ team through extensive research on performance-based seismic design, component performance evaluation criteria, and engineering applications. The method’s key procedures include defining seismic precaution objectives, conceptual design, performance objective setting, structural analysis, and performance evaluation. The approach emphasizes stratification and classification to refine structural and component performance objectives, integrates elasto-plastic analysis into seismic measures, and uses performance evaluation results as a foundation for design decisions, ensuring alignment with specified performance goals. A multi-storey steel concentrically braced frame located in a high seismic intensity zone was taken as a case study to illustrate the practical application of the proposed method, and the engineering applications of the stratified and classified performance-based seismic design method were discussed as well as its differences from the traditional design methods in codes. The design process began with conceptual design, performance objective setting, and preliminary design based on the "weak brace" concept. Structural analysis, performance evaluation, and design adjustments were iteratively optimized by using computational algorithms to minimize steel usage in primary components. The optimization ensured compliance with predefined performance criteria, including structural drifts, stress ratios of components, and damage grades. The results demonstrated that, compared to the original schemes based on the traditional seismic design methods in codes, in the scheme designed by the stratified and classified performance-based seismic design method, the cross sections of braces decreased significantly, while those of columns connected to braces increased. The steel usage in primary components was reduced by 23%. Furthermore, the scheme designed by the proposed method reduced structural drifts and the maximum total seismic input energy, increased plastic deformation energy dissipation, effectively minimized the damages of vertical components, and distributed the damage of braces more uniformly under rarely occurred earthquake, resulting in a more efficient and resilient energy dissipation system. In conclusion, the proposed stratified and classified PBSD method delivers superior seismic performance while optimizing material usage, demonstrating its potential for efficient and resilient structural design.
2024, 39(12): 12-19.
doi: 10.13206/j.gjgS24102901
Abstract:
The applications of performance-based design methods on eccentric web member steel truss structural system were discussed. Based on the mechanical properties of non-uniform beams, the study examineed the influence of the ratio of the stiffness between the middle section of the eccentric web member steel truss and the connecting beams at the both ends on the internal force distribution of the truss. Through rational preliminary design, the bending stiffness ratio between the middle part and connecting beams was controlled, which allowed the demands of connecting beams to be easily satisfied while simultaneously reducing the demands of components and connections within the relevant ranges of the main structure. The seismic performance, stress of joints, human comfort of floor vibration, and progressive collapse prevention of the eccentric web member steel truss corridor structure were designed and assessed respectively. The results demonstrated that, through rational performance-based design, each index satisfied the requirements of expected performance objectives. The research also could provide references for similar projects.
The applications of performance-based design methods on eccentric web member steel truss structural system were discussed. Based on the mechanical properties of non-uniform beams, the study examineed the influence of the ratio of the stiffness between the middle section of the eccentric web member steel truss and the connecting beams at the both ends on the internal force distribution of the truss. Through rational preliminary design, the bending stiffness ratio between the middle part and connecting beams was controlled, which allowed the demands of connecting beams to be easily satisfied while simultaneously reducing the demands of components and connections within the relevant ranges of the main structure. The seismic performance, stress of joints, human comfort of floor vibration, and progressive collapse prevention of the eccentric web member steel truss corridor structure were designed and assessed respectively. The results demonstrated that, through rational performance-based design, each index satisfied the requirements of expected performance objectives. The research also could provide references for similar projects.
2024, 39(12): 20-28.
doi: 10.13206/j.gjgS24112803
Abstract:
The study aimed to evaluate the deformation capacity of box-section steel members. The strain ductility coefficient, a stain-based evaluation index, was proposed for box-section steel members. tests quasi-static were conducted oedsix box-section steed mombers, the experimental failure modes and hysteretic responses were investigated, and the ultimate deformation and plastic zome length of the specimers were extracted to obtain the strain dultility coefficients. The results show that the failure mode of all specimens involved local buckling deformation of both the flanges and webs, and the deformation processes of the two were coordinated with ench other. All specimens had full hysteresis curves with no significant pinching phenomenon, demonstrating good ductility and energy dissipation capacity. The ultimate strains and strain ductility coefficients of box sections decreased with the increase of the width-to-thickness ratio and axial compression ratio. Based on the test results, validated and reliable finite element models were established, and parametric studies were conducted to investigate the effects of flange width-to-thickness ratio, web height-to-thickness ratio, and axial compression ratio on the strain ductility coefficients. The results indicated that the strain ductility coefficients of box-section steel members exhibitsed a decreasing trend with the increase in flange width-to-thickness ratio, web height-to-thickness ratio, and axial compression ratio. The regression analysis was conducted to establish a calculation recommendation formula for the strain ductility coefficients. The validity of the formula was verified.
The study aimed to evaluate the deformation capacity of box-section steel members. The strain ductility coefficient, a stain-based evaluation index, was proposed for box-section steel members. tests quasi-static were conducted oedsix box-section steed mombers, the experimental failure modes and hysteretic responses were investigated, and the ultimate deformation and plastic zome length of the specimers were extracted to obtain the strain dultility coefficients. The results show that the failure mode of all specimens involved local buckling deformation of both the flanges and webs, and the deformation processes of the two were coordinated with ench other. All specimens had full hysteresis curves with no significant pinching phenomenon, demonstrating good ductility and energy dissipation capacity. The ultimate strains and strain ductility coefficients of box sections decreased with the increase of the width-to-thickness ratio and axial compression ratio. Based on the test results, validated and reliable finite element models were established, and parametric studies were conducted to investigate the effects of flange width-to-thickness ratio, web height-to-thickness ratio, and axial compression ratio on the strain ductility coefficients. The results indicated that the strain ductility coefficients of box-section steel members exhibitsed a decreasing trend with the increase in flange width-to-thickness ratio, web height-to-thickness ratio, and axial compression ratio. The regression analysis was conducted to establish a calculation recommendation formula for the strain ductility coefficients. The validity of the formula was verified.
2024, 39(12): 29-37.
doi: 10.13206/j.gjgS24031902
Abstract:
To investigate the seismic performance of self-centering structural systems and the simplified modeling methods for energy-dissipating components, the paper proposed a novel prefabricated self-centering steel frame-support system based on traditional rigid-frame steel structures. This system incorporates replaceable components, including double-yield-point prefabricated buckling-restrained braces and self-centering prestressed steel frame beam-column joints with dog-bone weakened cover plates, into the traditional rigid-frame structure. A simplified calculation model for the replaceable components was developed by using the finite element software OpenSEES, and its accuracy was verified through a comparison with existing data. Based on the proposed seismic performance-based design objectives, the novel system was designed and its seismic performance was studied through elastic-plastic time-history analysis (NLTHA). The study indicated that the proposed simplified calculation model had high accuracy and could be applied to the elastic-plastic time history analysis of the system. The novel prefabricated system, designed based on the proposed seismic performance indicators, exhibited superior seismic performance compared to traditional systems. The maximum top-floor displacement and maximum inter-story drift of the novel prefabricated system were smaller than those of both the traditional rigid-frame steel structure and the traditional rigid-frame steel bracing structure. Specifically, the maximum top-floor displacements and maximum inter-story drifts in the x-and y-directions were, on average, reduced by 28.35%, 10.13%, and 26.86%, 10.42%, respectively, compared to the traditional rigid-frame steel structure. The double-yield-point prefabricated buckling-restrained braces could control the inter-story drift of the structure, while the inclusion of self-centering prestressed steel frame beam-column joints with dog-bone weakened cover plates could further enhance its energy dissipation capacity.
To investigate the seismic performance of self-centering structural systems and the simplified modeling methods for energy-dissipating components, the paper proposed a novel prefabricated self-centering steel frame-support system based on traditional rigid-frame steel structures. This system incorporates replaceable components, including double-yield-point prefabricated buckling-restrained braces and self-centering prestressed steel frame beam-column joints with dog-bone weakened cover plates, into the traditional rigid-frame structure. A simplified calculation model for the replaceable components was developed by using the finite element software OpenSEES, and its accuracy was verified through a comparison with existing data. Based on the proposed seismic performance-based design objectives, the novel system was designed and its seismic performance was studied through elastic-plastic time-history analysis (NLTHA). The study indicated that the proposed simplified calculation model had high accuracy and could be applied to the elastic-plastic time history analysis of the system. The novel prefabricated system, designed based on the proposed seismic performance indicators, exhibited superior seismic performance compared to traditional systems. The maximum top-floor displacement and maximum inter-story drift of the novel prefabricated system were smaller than those of both the traditional rigid-frame steel structure and the traditional rigid-frame steel bracing structure. Specifically, the maximum top-floor displacements and maximum inter-story drifts in the x-and y-directions were, on average, reduced by 28.35%, 10.13%, and 26.86%, 10.42%, respectively, compared to the traditional rigid-frame steel structure. The double-yield-point prefabricated buckling-restrained braces could control the inter-story drift of the structure, while the inclusion of self-centering prestressed steel frame beam-column joints with dog-bone weakened cover plates could further enhance its energy dissipation capacity.
2024, 39(12): 38-48.
doi: 10.13206/j.gjgS24011101
Abstract:
There are some problems such as low construction efficiency, high labor cost and environmental pollution in the traditional full penetration welding joints of square steel tubular columns. In order to solve the above problems, the research group proposed the full-bolted connection joint of square steel tubular column with built-in octagonal core barrel. The joint connects the upper and lower columns by setting the core tube and high-strength bolts to realize the complete assembly on site. At present, a series of quasi-static, pseudo-dynamic and shaking table tests have been completed. The results showed that the joint form had the same mechanical properties as the welded joint, and could also realize the efficient assembly of the construction site. Furthermore, to enhance construction convenience and economy, as well as reduce the amount of steel and welding labor, a cross-shaped core barrel was suggested. The barrel was designed to have the same elastic bearing capacity as the octagonal core barrel. The finite element software ABAQUS was used to create a finite element analysis model for fully-bolted joints of square steel columns with built-in octagonal core barrels and built-in cross-shaped core barrels. The whole process of stress of the two connection joint members was analyzed, and the plastic development and final failure mode of the whole specimen and local members at the stress characteristic points were compared respectively. On this basis, the seismic performance of the two connection joints was further compared and analyzed, including hysteresis curve, skeleton curve, stiffness degradation, energy dissipation performance and residual deformation.
The results of finite element analysis showed that the two types of joints damage under reciprocating loading were relatively similar, and both were plastic hinge section damage at the bottom of the column.The hysteresis curves of the forms of the two joints were full and there were no obvious pinching phenomenon. The equivalent viscous damping coefficients were between 0.25 and 0.28, and the seismic performance of the two was good. The elastic interlayer displacement angle ranged from 1/36 to 1/22, and the elastic-plastic interlayer displacement angle was 1/15, both of which met the requirements of Code for Seismic Design of Buildings(GB/T 50011—2010). Compared with the form of the joint with built-in octagonal core barrels, the yield bearing capacity of the form of the joint with built-in cross-shaped core barrels was reduced by 7.5%-16.3%, the peak bearing capacity was reduced by 7.8%, and the ductility performance was improved by about 66.7%. When the displacement angle was 1/100, 1/50 and 1/15, the stiffness of the joints with built-in cross-shaped core barrels was 0.94%, 2.05% and 8.43% higher,respectively. When the negative load was loaded to the displacement angle of 1/100,1/50 and 1/15, the stiffness of the joints with built-in cross-shaped core barrels was 0.91%, 1.85% and 8.51% higher, respectively. After loading, the residual deformation of the joints with built-in cross-shaped core barrels was 4.9% lower than that of the the joints built-in octagonal core barrels. The above research results showed that the joints with built-in octagonal core barrels had higher bearing capacity and energy dissipation capacity, and their hysteresis curves were fuller ; the stiffness degradation of the joints with built-in cross-shaped core barrels was gentle, the residual deformation after the earthquake was small, and the ductility performance was better. Both joint forms have good application prospects.
There are some problems such as low construction efficiency, high labor cost and environmental pollution in the traditional full penetration welding joints of square steel tubular columns. In order to solve the above problems, the research group proposed the full-bolted connection joint of square steel tubular column with built-in octagonal core barrel. The joint connects the upper and lower columns by setting the core tube and high-strength bolts to realize the complete assembly on site. At present, a series of quasi-static, pseudo-dynamic and shaking table tests have been completed. The results showed that the joint form had the same mechanical properties as the welded joint, and could also realize the efficient assembly of the construction site. Furthermore, to enhance construction convenience and economy, as well as reduce the amount of steel and welding labor, a cross-shaped core barrel was suggested. The barrel was designed to have the same elastic bearing capacity as the octagonal core barrel. The finite element software ABAQUS was used to create a finite element analysis model for fully-bolted joints of square steel columns with built-in octagonal core barrels and built-in cross-shaped core barrels. The whole process of stress of the two connection joint members was analyzed, and the plastic development and final failure mode of the whole specimen and local members at the stress characteristic points were compared respectively. On this basis, the seismic performance of the two connection joints was further compared and analyzed, including hysteresis curve, skeleton curve, stiffness degradation, energy dissipation performance and residual deformation.
The results of finite element analysis showed that the two types of joints damage under reciprocating loading were relatively similar, and both were plastic hinge section damage at the bottom of the column.The hysteresis curves of the forms of the two joints were full and there were no obvious pinching phenomenon. The equivalent viscous damping coefficients were between 0.25 and 0.28, and the seismic performance of the two was good. The elastic interlayer displacement angle ranged from 1/36 to 1/22, and the elastic-plastic interlayer displacement angle was 1/15, both of which met the requirements of Code for Seismic Design of Buildings(GB/T 50011—2010). Compared with the form of the joint with built-in octagonal core barrels, the yield bearing capacity of the form of the joint with built-in cross-shaped core barrels was reduced by 7.5%-16.3%, the peak bearing capacity was reduced by 7.8%, and the ductility performance was improved by about 66.7%. When the displacement angle was 1/100, 1/50 and 1/15, the stiffness of the joints with built-in cross-shaped core barrels was 0.94%, 2.05% and 8.43% higher,respectively. When the negative load was loaded to the displacement angle of 1/100,1/50 and 1/15, the stiffness of the joints with built-in cross-shaped core barrels was 0.91%, 1.85% and 8.51% higher, respectively. After loading, the residual deformation of the joints with built-in cross-shaped core barrels was 4.9% lower than that of the the joints built-in octagonal core barrels. The above research results showed that the joints with built-in octagonal core barrels had higher bearing capacity and energy dissipation capacity, and their hysteresis curves were fuller ; the stiffness degradation of the joints with built-in cross-shaped core barrels was gentle, the residual deformation after the earthquake was small, and the ductility performance was better. Both joint forms have good application prospects.
2024, 39(12): 49-60.
doi: 10.13206/j.gjgS23112803
Abstract:
In order to study the seismic performance and stress mechanism of inner sleeve splicing joints of modular steel construction, based on the experimental study on the seismic performance of the inner sleeve splicing joints, a finite element analysis model with the same size and load conditions as the test joint specimens was established, and the validity of the finite element model was verified. By changing the structural parameters of the joint, the influence of the length of the inner sleeve, the height of the inner sleeve, and the inner partition of the column on the seismic performance of the joint was studied. The calculation formula of the contact force between the inner sleeve and the column wall under the action of axial compression was derived, and compared with the finite element calculation results, the validity of the theoretical calculation formula of the contact force was proved. The results showed that the established finite element model could effectively simulate the working state and ultimate bearing capacity of the inner sleeve splicing joints. The inner sleeve splicing joints had good seismic performance, and the stress state of the joint could be improved by reasonable construction, which could promote the plastic hinge of the beam end to move outward to realize the ductile failure of the joint. Increasing the thickness of the inner sleeve and the length of the inner sleeve had no obvious effect on the bearing capacity of the joint. The setting of inner clapboard could significantly improve the bearing capacity and energy dissipation capacity of the joint. The contact force between the bending deformation of the steel tube column and the inner sleeve increased the stress of the column section under the original load state and produces local stress concentration, the adverse effects should be considered in the design.
In order to study the seismic performance and stress mechanism of inner sleeve splicing joints of modular steel construction, based on the experimental study on the seismic performance of the inner sleeve splicing joints, a finite element analysis model with the same size and load conditions as the test joint specimens was established, and the validity of the finite element model was verified. By changing the structural parameters of the joint, the influence of the length of the inner sleeve, the height of the inner sleeve, and the inner partition of the column on the seismic performance of the joint was studied. The calculation formula of the contact force between the inner sleeve and the column wall under the action of axial compression was derived, and compared with the finite element calculation results, the validity of the theoretical calculation formula of the contact force was proved. The results showed that the established finite element model could effectively simulate the working state and ultimate bearing capacity of the inner sleeve splicing joints. The inner sleeve splicing joints had good seismic performance, and the stress state of the joint could be improved by reasonable construction, which could promote the plastic hinge of the beam end to move outward to realize the ductile failure of the joint. Increasing the thickness of the inner sleeve and the length of the inner sleeve had no obvious effect on the bearing capacity of the joint. The setting of inner clapboard could significantly improve the bearing capacity and energy dissipation capacity of the joint. The contact force between the bending deformation of the steel tube column and the inner sleeve increased the stress of the column section under the original load state and produces local stress concentration, the adverse effects should be considered in the design.
2024, 39(12): 61-73.
doi: 10.13206/j.gjgS23110303
Abstract:
In order to analyze the collapse of long-span space structures subjected to strong earthquakes, SAP 2000 software was used to model and analyze the seismic performance of a gymnasium in Xi’an University. Firstly, the natural vibration characteristics of the structure were analyzed, and the low-order mode and natural vibration period of the structure were understood. Subsequently, the seismic performance of the structure was investigated through the response spectrum analysis of mode decomposition. On this basis, the elastoplastic time-history analysis of the structure was focused on, and the plastic development process of the structure under different peak seismic waves was deeply discussed. According to the maximum deformation of the structure, combined with the number and state of plastic hinge, whether the structure could meet the expected capability target of the structure under the specified seismic load was determined, and the response laws of the structure were summarized. The method of determining whether the structure collapsed was obtained. The results showed that the structure had good seismic performance under the action of 8 degree earthquake and rarey occurred earthquakes. Under the action of three-way input RSN55_SFERN seismic wave, the structure did not collapse when the peak value of seismic wave was 1 000 cm/s2. Under the action of artificial fitted seismic wave of unidirectional rarely occurred earthquakes, when the peak value of Y-direction input seismic wave was 1 400 cm/s2, more than half of the lattice columns completely failed at 7.3 s, and the overall maximum displacement of the structure was 2.2 m, which indicated the collapse of the structure. Under the action of artificial fitting seismic waves of a three-way major earthquake, when the peak value of local seismic waves was 600 cm/s2, almost all the lattice columns of the main library failed at 20.8 s, nearly half of the auxiliary columns failed, and the overall deformation of the main library exceeded 2.72 m. Based on the hinge and deformation conditions, the structure collapse was determined at this time. The plastic hinge distribution of the structure occurred on the lattice column and the chord member of the central main truss. It is necessary to investigate the multi-directional seismic wave action when investigating the seismic and collapse resistance performance of long-span structures.
In order to analyze the collapse of long-span space structures subjected to strong earthquakes, SAP 2000 software was used to model and analyze the seismic performance of a gymnasium in Xi’an University. Firstly, the natural vibration characteristics of the structure were analyzed, and the low-order mode and natural vibration period of the structure were understood. Subsequently, the seismic performance of the structure was investigated through the response spectrum analysis of mode decomposition. On this basis, the elastoplastic time-history analysis of the structure was focused on, and the plastic development process of the structure under different peak seismic waves was deeply discussed. According to the maximum deformation of the structure, combined with the number and state of plastic hinge, whether the structure could meet the expected capability target of the structure under the specified seismic load was determined, and the response laws of the structure were summarized. The method of determining whether the structure collapsed was obtained. The results showed that the structure had good seismic performance under the action of 8 degree earthquake and rarey occurred earthquakes. Under the action of three-way input RSN55_SFERN seismic wave, the structure did not collapse when the peak value of seismic wave was 1 000 cm/s2. Under the action of artificial fitted seismic wave of unidirectional rarely occurred earthquakes, when the peak value of Y-direction input seismic wave was 1 400 cm/s2, more than half of the lattice columns completely failed at 7.3 s, and the overall maximum displacement of the structure was 2.2 m, which indicated the collapse of the structure. Under the action of artificial fitting seismic waves of a three-way major earthquake, when the peak value of local seismic waves was 600 cm/s2, almost all the lattice columns of the main library failed at 20.8 s, nearly half of the auxiliary columns failed, and the overall deformation of the main library exceeded 2.72 m. Based on the hinge and deformation conditions, the structure collapse was determined at this time. The plastic hinge distribution of the structure occurred on the lattice column and the chord member of the central main truss. It is necessary to investigate the multi-directional seismic wave action when investigating the seismic and collapse resistance performance of long-span structures.
2024, 39(12): 74-85.
doi: 10.13206/j.gjgS24011802
Abstract:
The prefabricated steel-concrete composite structure is a type of prefabricated structure with broad application prospect, there is a kind of semi-rigid joint among the joints of prefabricated concrete columns and steel beams, and the rotational stiffness and seismic performance of the semi-rigid joint are closely related to the structure of the joint. In order to study the seismic performance and rotational stiffness of the dry connection joint between the precast concrete column and the steel beam, a full-scale component with a semi-rigid connection joint beween the precast concrete column and steel beam was designed and subjected to quasi-static loading tests. The yield characteristics of the steel joint module, the joint core area reinforcing steel, and the longitudinal rebars of the precast column were analyzed in the connection joint, as well as the bearing capacity, hysteretic behavior, and failure mechanism of the connection joint’s seismic performance indicators and rotational stiffness. The key components in the connection joint were simulated by using the ABAQUS finite element software, and the concrete damage plastic model was used to simulate the concrete failure process. The uniaxial compression and tension constitutive models of concrete were adopted from the model provided in the Code for Design of Concrete Structures (GB/T 50010—2010), and the constitutive model of steel rebars was adopted from the ABAQUS user-defined material subroutine package PQ-Fiber developed by Tsinghua University, which used the uniaxial elastic-plastic hysteretic constitutive model of steel rebars (USteel02). The key components include the thickness of the side plates of steel joints module, the diameter of the tie rods, the thickness of the stiffeners on the corbels, the thickness of the vertical plate on the corbels, the thickness of the horizontal plate on the corbels, and the diameter of the high-strength bolts for connection. The research showed that the failure modes of the connection joint were beam hinge mechanism failure, concrete crushing of the slab, and yielding of the steel joint module side plates and internal tie rods. The existence of the steel joint module ensured the stiffness and bearing capacity of the beam-column node zone, which could meet the requirements of "strong joints" in seismic design. The displacement angle between adjacent storeys exceeded 2% when the connection joint showed obvious damage, and the bearing capacity had not yet decreased. When the displacement angle exceeded 2.75%, the steel joint module side plates experienced tensile outward bulging at the corresponding location, and the tie rods yielded, but no obvious damage was found in the steel corbels or the welds. The hysteretic curve of the specimen was in the shape of a spindle, the skeleton curve experienced a long strengthening section, and the bearing capacity decreased slowly. The bending moment-angle curve of the beam ends indicated that the joint had the characteristics of a semi-rigid joint, and the positive and negative rotation stiffnesses were not consistent, with the negative rotation stiffness being six times greater than the positive rotation stiffness. The components that had a significant impact on the rotational stiffness of the connected joints were the thickness of the steel module side plates, the diameter of the tension rods, and the thickness of the vertical plate on the corbels. The thickness of the side plates and the diameter of the tension rods had a significant impact on the positive rotational stiffness, while the thickness of the vertical plate and the stiffeners could effectively improve the negative rotational stiffness, but their thickness had little effect on the positive rotational stiffness.
The prefabricated steel-concrete composite structure is a type of prefabricated structure with broad application prospect, there is a kind of semi-rigid joint among the joints of prefabricated concrete columns and steel beams, and the rotational stiffness and seismic performance of the semi-rigid joint are closely related to the structure of the joint. In order to study the seismic performance and rotational stiffness of the dry connection joint between the precast concrete column and the steel beam, a full-scale component with a semi-rigid connection joint beween the precast concrete column and steel beam was designed and subjected to quasi-static loading tests. The yield characteristics of the steel joint module, the joint core area reinforcing steel, and the longitudinal rebars of the precast column were analyzed in the connection joint, as well as the bearing capacity, hysteretic behavior, and failure mechanism of the connection joint’s seismic performance indicators and rotational stiffness. The key components in the connection joint were simulated by using the ABAQUS finite element software, and the concrete damage plastic model was used to simulate the concrete failure process. The uniaxial compression and tension constitutive models of concrete were adopted from the model provided in the Code for Design of Concrete Structures (GB/T 50010—2010), and the constitutive model of steel rebars was adopted from the ABAQUS user-defined material subroutine package PQ-Fiber developed by Tsinghua University, which used the uniaxial elastic-plastic hysteretic constitutive model of steel rebars (USteel02). The key components include the thickness of the side plates of steel joints module, the diameter of the tie rods, the thickness of the stiffeners on the corbels, the thickness of the vertical plate on the corbels, the thickness of the horizontal plate on the corbels, and the diameter of the high-strength bolts for connection. The research showed that the failure modes of the connection joint were beam hinge mechanism failure, concrete crushing of the slab, and yielding of the steel joint module side plates and internal tie rods. The existence of the steel joint module ensured the stiffness and bearing capacity of the beam-column node zone, which could meet the requirements of "strong joints" in seismic design. The displacement angle between adjacent storeys exceeded 2% when the connection joint showed obvious damage, and the bearing capacity had not yet decreased. When the displacement angle exceeded 2.75%, the steel joint module side plates experienced tensile outward bulging at the corresponding location, and the tie rods yielded, but no obvious damage was found in the steel corbels or the welds. The hysteretic curve of the specimen was in the shape of a spindle, the skeleton curve experienced a long strengthening section, and the bearing capacity decreased slowly. The bending moment-angle curve of the beam ends indicated that the joint had the characteristics of a semi-rigid joint, and the positive and negative rotation stiffnesses were not consistent, with the negative rotation stiffness being six times greater than the positive rotation stiffness. The components that had a significant impact on the rotational stiffness of the connected joints were the thickness of the steel module side plates, the diameter of the tension rods, and the thickness of the vertical plate on the corbels. The thickness of the side plates and the diameter of the tension rods had a significant impact on the positive rotational stiffness, while the thickness of the vertical plate and the stiffeners could effectively improve the negative rotational stiffness, but their thickness had little effect on the positive rotational stiffness.
2024, 39(12): 86-94.
doi: 10.13206/j.gjgS24102802
Abstract:
With growing urbanization, long-span pedestrian bridges have become an integral part of modern urban infrastructure due to their unique structural forms and essential architectural functions. However, such bridges are prone to significant wind-induced vibrations under wind loads, potentially compromising structural safety and user comfort. The wind-induced vibration control for a long-span pedestrian bridge was investigated, and a wind-resistant design method based on comfort performance was proposed. Using the ribbon-like pedestrian bridge of the Suzhou Cultural Expo Center as a case study, wind load characteristic data for the bridge under various wind speeds and directions were obtained from wind tunnel experiments and nonlinear time-history analysis, and its dynamic responses were also systematically analyzed. A comfort-based wind-resistance performance design framework was established to improve the comfort of the pedestrian bridge by optimizing structural design and vibration reduction measures. The study employed multi-tuned mass damper (MTMD) technology to effectively control the first three-ordor vibration modes of the structure. The results indicated that the acceleration response of the structure was significantly reduced with the MTMD system in the field, achieving a vibration reduction efficiency exceeding 50%. Under large wind speeds, the peak accelerations in both vertical and lateral directions met the requirements of relevant standards.
With growing urbanization, long-span pedestrian bridges have become an integral part of modern urban infrastructure due to their unique structural forms and essential architectural functions. However, such bridges are prone to significant wind-induced vibrations under wind loads, potentially compromising structural safety and user comfort. The wind-induced vibration control for a long-span pedestrian bridge was investigated, and a wind-resistant design method based on comfort performance was proposed. Using the ribbon-like pedestrian bridge of the Suzhou Cultural Expo Center as a case study, wind load characteristic data for the bridge under various wind speeds and directions were obtained from wind tunnel experiments and nonlinear time-history analysis, and its dynamic responses were also systematically analyzed. A comfort-based wind-resistance performance design framework was established to improve the comfort of the pedestrian bridge by optimizing structural design and vibration reduction measures. The study employed multi-tuned mass damper (MTMD) technology to effectively control the first three-ordor vibration modes of the structure. The results indicated that the acceleration response of the structure was significantly reduced with the MTMD system in the field, achieving a vibration reduction efficiency exceeding 50%. Under large wind speeds, the peak accelerations in both vertical and lateral directions met the requirements of relevant standards.
2024, 39(12): 95-102.
doi: 10.13206/j.gjgS24103101
Abstract:
The extended end-plate joint is mainly used to transfer gravity and seismic effects. However, in extreme states, connecting joints also have a significant impact on the overall performance of the structure and the prevention of continuous collapse. Among various disasters, fire is still one of the disasters with the highest frequency and the widest range of influence. At present, research on fire resistance performance mainly focuses on the heating stage of a fire, but materials, components, and structures may exhibit different characteristics during the cooling stage compared to the heating stage. During the entire process of a fire, steel joints will be subjected to the tension generated by the "catenary effect" caused by the large deflection of the beam span, as well as the tension generated by the cold shrinkage of the steel. Under the combined action of tension and bending, the steel joints will be damaged, leading to the collapse of the entire steel frame structure. At present, there is relatively little research on the mechanical properties of extended end-plate joints of steel frames during the entire fire process, both domestically and internationally. Therefore, it is urgent to conduct in-depth research on them to provide technical supports for performance-based fire protection design. This ensures that the main structural components are not damaged within a certain period of time after a fire, allowing sufficient time for personnel in the building to escape and for firefighters to carry out their rescue operations.
In the present study, nonlinear thermal-mechanical coupling analysis of extended end-plate joints under the combined action of tension and bending was conducted by using the ABAQUS finite element software. Firstly, a three-dimensional thermal analysis and structural response nonlinear analysis model was established for the extended end-plate joint in the fire heating stage. The accuracy of the modeling method was verified by using the results of heating tests under constant bending effect in existing literature. On this basis, the joints’ temperature field distribution during the entire temperature rise and fall process in a fire was obtained through transient thermal analysis. The thermal-structure coupling analysis were performed to obtain the mechanical properties of joints under the combined action of tension and bending, while the parametric analysis was conducted on the influence of factors such as the fire’s temperature rise and fall history and the magnitude of tensile loads on the mechanical behavior of joints. The results indicated that throughout the entire fire process, the deflection of joints would continue to increase during the cooling stage due to the influence of temperature hysteresis, leading to their failure in the early stage of cooling. At the same time, due to the influence of the catenary effect and the tensile force generated by the cold shrinkage deformation of steel beams, bolt tension was detrimental to the fire resistance time and residual deformation of the joint. In addition, parameter analysis of different tensile forces on joints showsed that when the bending moment of the joint remained constant, the tensile force would have a significant impact on the mechanical behavior of the joint. When the tensile for increased, the deformation and residual strain of the joint gradually increased during the cooling stage, eventually leading to joint failure. Therefore, in fire analysis, the entire process of the fire and the influence of tensile forces on the mechanical behavior of joints should be comprehensively considered, and a rational assessment and detailed calculation analysis of the additional tensile forces exerted on these joints should be conducted.
The extended end-plate joint is mainly used to transfer gravity and seismic effects. However, in extreme states, connecting joints also have a significant impact on the overall performance of the structure and the prevention of continuous collapse. Among various disasters, fire is still one of the disasters with the highest frequency and the widest range of influence. At present, research on fire resistance performance mainly focuses on the heating stage of a fire, but materials, components, and structures may exhibit different characteristics during the cooling stage compared to the heating stage. During the entire process of a fire, steel joints will be subjected to the tension generated by the "catenary effect" caused by the large deflection of the beam span, as well as the tension generated by the cold shrinkage of the steel. Under the combined action of tension and bending, the steel joints will be damaged, leading to the collapse of the entire steel frame structure. At present, there is relatively little research on the mechanical properties of extended end-plate joints of steel frames during the entire fire process, both domestically and internationally. Therefore, it is urgent to conduct in-depth research on them to provide technical supports for performance-based fire protection design. This ensures that the main structural components are not damaged within a certain period of time after a fire, allowing sufficient time for personnel in the building to escape and for firefighters to carry out their rescue operations.
In the present study, nonlinear thermal-mechanical coupling analysis of extended end-plate joints under the combined action of tension and bending was conducted by using the ABAQUS finite element software. Firstly, a three-dimensional thermal analysis and structural response nonlinear analysis model was established for the extended end-plate joint in the fire heating stage. The accuracy of the modeling method was verified by using the results of heating tests under constant bending effect in existing literature. On this basis, the joints’ temperature field distribution during the entire temperature rise and fall process in a fire was obtained through transient thermal analysis. The thermal-structure coupling analysis were performed to obtain the mechanical properties of joints under the combined action of tension and bending, while the parametric analysis was conducted on the influence of factors such as the fire’s temperature rise and fall history and the magnitude of tensile loads on the mechanical behavior of joints. The results indicated that throughout the entire fire process, the deflection of joints would continue to increase during the cooling stage due to the influence of temperature hysteresis, leading to their failure in the early stage of cooling. At the same time, due to the influence of the catenary effect and the tensile force generated by the cold shrinkage deformation of steel beams, bolt tension was detrimental to the fire resistance time and residual deformation of the joint. In addition, parameter analysis of different tensile forces on joints showsed that when the bending moment of the joint remained constant, the tensile force would have a significant impact on the mechanical behavior of the joint. When the tensile for increased, the deformation and residual strain of the joint gradually increased during the cooling stage, eventually leading to joint failure. Therefore, in fire analysis, the entire process of the fire and the influence of tensile forces on the mechanical behavior of joints should be comprehensively considered, and a rational assessment and detailed calculation analysis of the additional tensile forces exerted on these joints should be conducted.
