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Steel Construction Published the List of Highly Influential Articles of 2020
2025 Vol. 40, No. 1
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2025, 40(1): 1-17.
doi: 10.13206/j.gjgS24080629
Abstract
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Abstract:
Spatial structures, widely utilized in long-span, large-space, and large-area buildings, playing a significant role in national infrastructure and urban development. China has become a major country in the field of spatial structures, gradually developing its own technological characteristics and steadily advancing toward becoming a strong nation in spatial structures. This paper summarized China’s 40-year development and innovative achievements in structural systems, theoretical methods, and engineering technologies of spatial structures. In terms of structural systems, this paper discussed the classification methods of modern spatial structures, and elaborated on the mechanical characteristics and engineering practices of three major categories: rigid, rigid-flexible, and flexible spatial structures. It demonstrated that China’s spatial structural systems were continuously expanding, exhibiting diversification and modernization trends. Regarding theoretical methods, the paper reviewed the evolution of theories and methods for spatial structural calculation, analysis, and design. It delved into several key issues, such as multi-stage whole-process simulation analysis methods, collaborative optimization and control analysis method for cable systems, finite particle method for structural complex behavior analysis, and spatial structure morphologies. In the aspect of engineering technology, the paper summarized the technological advancements in the design, construction, and operation maintenance phases. In design, the standard specification system had been improved, a series of specialized design software had been developed, and model testing and joint testing technologies had been established. In construction, various efficient construction technologies had been innovated, promoting digital and intelligent construction, and enhancing precision manufacturing and intelligent processing of members. For operation and maintenance, technologies such as structural sensing, data analysis, and state assessment had made certain progress and had been applied in engineering projects. Finally, the paper concluded with prospects for the future development of spatial structures in China, including the development of new structural systems, intelligent spatial structures, green and low-carbon spatial structures, and the assessment and reinforcement of existing spatial structures.
Spatial structures, widely utilized in long-span, large-space, and large-area buildings, playing a significant role in national infrastructure and urban development. China has become a major country in the field of spatial structures, gradually developing its own technological characteristics and steadily advancing toward becoming a strong nation in spatial structures. This paper summarized China’s 40-year development and innovative achievements in structural systems, theoretical methods, and engineering technologies of spatial structures. In terms of structural systems, this paper discussed the classification methods of modern spatial structures, and elaborated on the mechanical characteristics and engineering practices of three major categories: rigid, rigid-flexible, and flexible spatial structures. It demonstrated that China’s spatial structural systems were continuously expanding, exhibiting diversification and modernization trends. Regarding theoretical methods, the paper reviewed the evolution of theories and methods for spatial structural calculation, analysis, and design. It delved into several key issues, such as multi-stage whole-process simulation analysis methods, collaborative optimization and control analysis method for cable systems, finite particle method for structural complex behavior analysis, and spatial structure morphologies. In the aspect of engineering technology, the paper summarized the technological advancements in the design, construction, and operation maintenance phases. In design, the standard specification system had been improved, a series of specialized design software had been developed, and model testing and joint testing technologies had been established. In construction, various efficient construction technologies had been innovated, promoting digital and intelligent construction, and enhancing precision manufacturing and intelligent processing of members. For operation and maintenance, technologies such as structural sensing, data analysis, and state assessment had made certain progress and had been applied in engineering projects. Finally, the paper concluded with prospects for the future development of spatial structures in China, including the development of new structural systems, intelligent spatial structures, green and low-carbon spatial structures, and the assessment and reinforcement of existing spatial structures.
2025, 40(1): 18-25.
doi: 10.13206/j.gjgS23091402
Abstract:
Long-span spatial steel structures play an important role in the related fields of human productive activities and life, and large-scale double-layer reticulated shell structures have been widely used in actual projects. Due to the accidental events suffered during the actual service period of the structure is full of contingency, there are many cases of continuous collapse of the whole reticulated shell caused by the local failure of some key members. For example, affected by certain factors, the bending of critical members or the fracture of high-strength bolts at the joints make the reticulated shell structure unable to form an effective load transfer path after the failure of the critical members, and then the extension damage occurs, and finally the continuous collapse occurs, so it is necessary to study the effect of the reinforcement of the critical members on the collapse resistance of the double-layer reticulated shell structure in-depth. In this context, an actual double-layer reticulated shell structure was taken as the research object, and the SAP 2000 finite element software was used for modeling and analysis. Under the premise of considering the double nonlinearity of the structure and the initial defects, the whole process of nonlinear analysis was carried out for the reticulated shell under the action of displacement control, and combined with the development of plastic hinges, the location of failed rods was identified, and the critical rods were determined according to the importance coefficients of the failed rods. Critical rods were determined according to the importance coefficients of the failed rods. Three different reinforcement methods were selected to reinforce the critical members of the structure, and the ultimate capacity of the structure to resist collapse under static loads was analyzed before and after reinforcement. The dynamic time-history analysis of the double-layer reticulated shell structure was carried out under seismic actions, and the strain energy principle was introduced to analyze the collapse resistance of the structure under rarely occurred earthquakes, and compared and analyzed the dynamic response of the critical members before and after reinforcement.The results showed that: the strengthening of critical members could effectively improve the collapse resistance of the double-layer reticulated shell structure; the dynamic nonlinear time-history analysis of the double-layer reticulated shell structure was carried out by using the transient load method, and the correctness of the identification method of the critical members was verified by removing the failed members and analyzing the responses of the remaining structure; the comparison revealsed that the overall structural-bearing capacity could be improved by enhancing the strength of the critical members or increasing their cross-sectional area only, but the degree of improvement was limited. It was found that only by enhancing the material strength of the critical members or increasing their cross-sectional area could improve the bearing capacity of the whole structure, but the degree of improvement was limited, and by adopting the reinforcement method of enhancing the material strength and cross-sectional area of the critical members at the same time, the collapse resistance of the whole structure under static loads could be effectively improved; the collapse analysis of the structure under rarely occurred earthquakes was carried out, and the change of the strain energy of the double-layer reticulated structure with the reinforcement of critical members was smaller than that of the original structure before the reinforcement. It was further verified that effective reinforcement measures for the critical members of the double-layer reticulated shell structure could effectively improve the collapse resistance under earthquakes.
Long-span spatial steel structures play an important role in the related fields of human productive activities and life, and large-scale double-layer reticulated shell structures have been widely used in actual projects. Due to the accidental events suffered during the actual service period of the structure is full of contingency, there are many cases of continuous collapse of the whole reticulated shell caused by the local failure of some key members. For example, affected by certain factors, the bending of critical members or the fracture of high-strength bolts at the joints make the reticulated shell structure unable to form an effective load transfer path after the failure of the critical members, and then the extension damage occurs, and finally the continuous collapse occurs, so it is necessary to study the effect of the reinforcement of the critical members on the collapse resistance of the double-layer reticulated shell structure in-depth. In this context, an actual double-layer reticulated shell structure was taken as the research object, and the SAP 2000 finite element software was used for modeling and analysis. Under the premise of considering the double nonlinearity of the structure and the initial defects, the whole process of nonlinear analysis was carried out for the reticulated shell under the action of displacement control, and combined with the development of plastic hinges, the location of failed rods was identified, and the critical rods were determined according to the importance coefficients of the failed rods. Critical rods were determined according to the importance coefficients of the failed rods. Three different reinforcement methods were selected to reinforce the critical members of the structure, and the ultimate capacity of the structure to resist collapse under static loads was analyzed before and after reinforcement. The dynamic time-history analysis of the double-layer reticulated shell structure was carried out under seismic actions, and the strain energy principle was introduced to analyze the collapse resistance of the structure under rarely occurred earthquakes, and compared and analyzed the dynamic response of the critical members before and after reinforcement.The results showed that: the strengthening of critical members could effectively improve the collapse resistance of the double-layer reticulated shell structure; the dynamic nonlinear time-history analysis of the double-layer reticulated shell structure was carried out by using the transient load method, and the correctness of the identification method of the critical members was verified by removing the failed members and analyzing the responses of the remaining structure; the comparison revealsed that the overall structural-bearing capacity could be improved by enhancing the strength of the critical members or increasing their cross-sectional area only, but the degree of improvement was limited. It was found that only by enhancing the material strength of the critical members or increasing their cross-sectional area could improve the bearing capacity of the whole structure, but the degree of improvement was limited, and by adopting the reinforcement method of enhancing the material strength and cross-sectional area of the critical members at the same time, the collapse resistance of the whole structure under static loads could be effectively improved; the collapse analysis of the structure under rarely occurred earthquakes was carried out, and the change of the strain energy of the double-layer reticulated structure with the reinforcement of critical members was smaller than that of the original structure before the reinforcement. It was further verified that effective reinforcement measures for the critical members of the double-layer reticulated shell structure could effectively improve the collapse resistance under earthquakes.
2025, 40(1): 26-33.
doi: 10.13206/j.gjgS23092103
Abstract:
To study the structural response of prestressed double-layer cable flexible photovoltaic brackets under fluctuation wind loads, an analytical solution for cable horizontal tension without considering temperature effects under uniformly distributed loads was obtained based on the energy variational method. A finite element model with a span of 30.48 meters was established, and the correctness of the model was verified. Based on the Davenport spectrum and considering the spatial correlation of fluctuating wind loads, the AR linear filtering method was used to simulate the time histories of fluctuating wind speeds. Applying 0° and 180° fluctuating wind loads at 7 nodes in the span direction, including 0, L/6, 2L/6, 3L/6, 4L/6, 5L/6, and L, consider the impact of P-Δ effects and large deformations, Perform nonlinear dynamic time-history analysis of structures was carried out. The results showed that the structural vibration mode was mainly Z-axis translational, and the first-order vibration mode frequency was 2.844 Hz; the fluctuating wind load in the X direction had an impact on the displacement responses of the structure in all three directions, with the X and Z directions having the greatest impact; the transverse and vertical stiffnesses of the structure were weak at the mid span, and the longitudinal stiffness at the support was weak; in the 180° wind condition, the displacement response range in the X-direction of the structure and the tension response range of the load-bearing cable increased by 20% compared to that in the 0° wind condition, The impact of the 180° pulsating wind on the structure was greater; the horizontal tension response of the structure did not show significant changes compared to the applied prestress, and the impact of fluctuation wind on the internal force of the prestressed double-layer cable flexible photovoltaic bracket was relatively small.
To study the structural response of prestressed double-layer cable flexible photovoltaic brackets under fluctuation wind loads, an analytical solution for cable horizontal tension without considering temperature effects under uniformly distributed loads was obtained based on the energy variational method. A finite element model with a span of 30.48 meters was established, and the correctness of the model was verified. Based on the Davenport spectrum and considering the spatial correlation of fluctuating wind loads, the AR linear filtering method was used to simulate the time histories of fluctuating wind speeds. Applying 0° and 180° fluctuating wind loads at 7 nodes in the span direction, including 0, L/6, 2L/6, 3L/6, 4L/6, 5L/6, and L, consider the impact of P-Δ effects and large deformations, Perform nonlinear dynamic time-history analysis of structures was carried out. The results showed that the structural vibration mode was mainly Z-axis translational, and the first-order vibration mode frequency was 2.844 Hz; the fluctuating wind load in the X direction had an impact on the displacement responses of the structure in all three directions, with the X and Z directions having the greatest impact; the transverse and vertical stiffnesses of the structure were weak at the mid span, and the longitudinal stiffness at the support was weak; in the 180° wind condition, the displacement response range in the X-direction of the structure and the tension response range of the load-bearing cable increased by 20% compared to that in the 0° wind condition, The impact of the 180° pulsating wind on the structure was greater; the horizontal tension response of the structure did not show significant changes compared to the applied prestress, and the impact of fluctuation wind on the internal force of the prestressed double-layer cable flexible photovoltaic bracket was relatively small.
2025, 40(1): 34-41.
doi: 10.13206/j.gjgS23112101
Abstract:
In consideration of the requirements for "normal use", the Aseismic Technical Guidelines Based on Maintaining the Normal Use Function of Buildings (RISN-TG046—2023) incorporates control requirements for "floor horizontal acceleration" by incorporating calculations of conventional structural deformation and component bearing capacity. With advancements in energy dissipation and damping technology, commonly used damping products in engineering primarily consist of displacement-type dampers and velocity-type dampers. These different damper types possess distinct technical principles and product performance characteristics. Currently, single-type damping products are predominantly utilized in practical engineering; however, they have certain limitations and deficiencies when it comes to comprehensive index control over structural deformation, component bearing capacity, and floor horizontal acceleration. To address this issue under the new requirement for "normal use," an organic combination of displacement type and velocity type damping products was proposed. The floor horizontal acceleration should not exceed 0.25g during moderate earthquakes or 0.45g during rarely occurred earthquakes, except for the roof panel; furthermore, only a small number of members within the combined damping scheme were hinged under rarely occurred earthquakes and not hinged under moderate earthquakes in structural damage analysis with a depth not exceeding the "IO state". Comparative results across various indicators demonstrated that the combined damping scheme effectively enhanced and controlled structural responses while outperforming single damping schemes, thereby achieving the goal of normal use during moderate earthquakes.
In consideration of the requirements for "normal use", the Aseismic Technical Guidelines Based on Maintaining the Normal Use Function of Buildings (RISN-TG046—2023) incorporates control requirements for "floor horizontal acceleration" by incorporating calculations of conventional structural deformation and component bearing capacity. With advancements in energy dissipation and damping technology, commonly used damping products in engineering primarily consist of displacement-type dampers and velocity-type dampers. These different damper types possess distinct technical principles and product performance characteristics. Currently, single-type damping products are predominantly utilized in practical engineering; however, they have certain limitations and deficiencies when it comes to comprehensive index control over structural deformation, component bearing capacity, and floor horizontal acceleration. To address this issue under the new requirement for "normal use," an organic combination of displacement type and velocity type damping products was proposed. The floor horizontal acceleration should not exceed 0.25g during moderate earthquakes or 0.45g during rarely occurred earthquakes, except for the roof panel; furthermore, only a small number of members within the combined damping scheme were hinged under rarely occurred earthquakes and not hinged under moderate earthquakes in structural damage analysis with a depth not exceeding the "IO state". Comparative results across various indicators demonstrated that the combined damping scheme effectively enhanced and controlled structural responses while outperforming single damping schemes, thereby achieving the goal of normal use during moderate earthquakes.
2025, 40(1): 42-51.
doi: 10.13206/j.gjgS24070801
Abstract:
In recent years, an increasing number of super high-rise structures have adopted more complex cross-sectional forms (such as variable cross-section, chamfered cross-section, cross-section torsion, etc.) to meet the requirements of aesthetic and iconic design. Although super high-rise irregular buildings with twisted facade have higher ornamental and experiential values, they also bring much greater difficulties to structural analysis and construction than traditional forms of buildings. Glass curtain walls was a commonly-used exterior enclosure structure for super high-rise structures. In the design stage of its main components and connecting parts, the design load is the most critical, especially the wind load used in the design is the most complex. The wind load value of glass curtain walls is mainly based on the provisions of the Code for Load of Building Structures (GB 50009—2012) for the wind load values of enclosure structures. However, the code only considers the shape coefficient and gust coefficient values for regular polygons, and does not take into account the torsional facade situation. The reasonable values of wind load shape coefficients are directly related to the structural safety and performance of such structural glass curtain walls, considering the combination of twisted shapes and non-regular polygons. Based on the Jinhua EPC project, aiming at the special-shaped double-layer glass curtain wall on the facade of the twisted high-rise structure, the computational fluid dynamics (CFD) method was used to reconstruct the flow field of the twisted high-rise building, obtain the characteristics of the flow field structure around the building, analyze the local wind load distribution characteristics of the glass curtain wall and explore its generation mechanism. Based on the numerical simulation results, the shape coefficients of wind loadings were discussed. Preliminary studies had shown that for typical non-regular octagonal cross-sections, two distinct energy vortices were formed on the upper and lower sides of the windward side, and over time, these energy vortices moved along the longer side of the side to the leeward side, and then reformed on the windward side. In comparison, no obvious energy vortices were found on the windward side, and only smaller separated vortices were found at the junction of the long and short sides of the cross-section. Whether in the windward or leeward zone, the maximum and minimum shape coefficients of wind loads were close to the values specified in the specifications; however, the maximum and minimum shape coefficients in the crosswind zone were slightly higher than the standard values.
In recent years, an increasing number of super high-rise structures have adopted more complex cross-sectional forms (such as variable cross-section, chamfered cross-section, cross-section torsion, etc.) to meet the requirements of aesthetic and iconic design. Although super high-rise irregular buildings with twisted facade have higher ornamental and experiential values, they also bring much greater difficulties to structural analysis and construction than traditional forms of buildings. Glass curtain walls was a commonly-used exterior enclosure structure for super high-rise structures. In the design stage of its main components and connecting parts, the design load is the most critical, especially the wind load used in the design is the most complex. The wind load value of glass curtain walls is mainly based on the provisions of the Code for Load of Building Structures (GB 50009—2012) for the wind load values of enclosure structures. However, the code only considers the shape coefficient and gust coefficient values for regular polygons, and does not take into account the torsional facade situation. The reasonable values of wind load shape coefficients are directly related to the structural safety and performance of such structural glass curtain walls, considering the combination of twisted shapes and non-regular polygons. Based on the Jinhua EPC project, aiming at the special-shaped double-layer glass curtain wall on the facade of the twisted high-rise structure, the computational fluid dynamics (CFD) method was used to reconstruct the flow field of the twisted high-rise building, obtain the characteristics of the flow field structure around the building, analyze the local wind load distribution characteristics of the glass curtain wall and explore its generation mechanism. Based on the numerical simulation results, the shape coefficients of wind loadings were discussed. Preliminary studies had shown that for typical non-regular octagonal cross-sections, two distinct energy vortices were formed on the upper and lower sides of the windward side, and over time, these energy vortices moved along the longer side of the side to the leeward side, and then reformed on the windward side. In comparison, no obvious energy vortices were found on the windward side, and only smaller separated vortices were found at the junction of the long and short sides of the cross-section. Whether in the windward or leeward zone, the maximum and minimum shape coefficients of wind loads were close to the values specified in the specifications; however, the maximum and minimum shape coefficients in the crosswind zone were slightly higher than the standard values.
2025, 40(1): 52-57.
doi: 10.13206/j.gjgS23090801
Abstract:
Long-span light-gauge steel industrial buildings are typical wind-induced sensitive structures, which are prone to wind-induced disasters. The wind load is closely related to the shape of the building. Due to functional requirements,long cantilevered awnings are usually set in industrial buildings. There is no corresponding shape coefficients of wind loads of the cantilevered awning structure on both sides in the current code Load Code for the Design of Building Structures (GB 50009—2012) and Technical Code for Steel Structure of Light-Weight Building with Gabled Frames (GB 51022—2015). Therefore, selecting a reasonable shape coefficient of wind loads becomes the key to wind resistance design. Taking the industrial building with through-length awnings on both sides as the research background, the influence of different overhang lengths and inclination angles of the awnings on the shape coefficients of wind loads at typical positions of the building based on the software Fluent. It was compared with the current code GB 50009—2012 and GB 51022—2015, and provided the wind resistance design suggestions of structure with overhanging awnings. The results indicated that: the length of awning had a significant effect on the upper wall of the awning and the shape coefficient of the awning. The shape coefficient of wind loads on the upper wall of the windward awning changed from positive to negative with the increase of awning length at positive inclination angle, and was positive at negative inclination angle. The shape coefficients of the whole roof and the leeward side were negative, and the length of awning had little effect. The angle of the awning had great influence on the shape coefficient of the awning and the upper wall of the awning on the windward side, but had little influence on the other positions. When the awning angle was positive, the upper wall shape coefficient of the awning was negative and decreased with the increase in the awning angle, and the wind suction of the awning increased with the increase in the awning angle. When the angle of the awning was negative, the shape coefficient of the upper wall of the awning was positive and increased with the increase in the angle, and the wind suction of the awning decreased with the increase in the angle. By comparing with the current codes, GB 50009—2012 and GB 51022—2015, the shape coefficient of the windward awning was -1.37 when the awning length was 8 m and the angle was 0°. The shape coefficient of eaves on the windward side was close to -1.4 in item 16 of table 8.3.1 of Load Code for the Design of Building Structures, but the shape coefficients of wind load at other positions were different. And for other awning lengths and angles corresponding to the structure of the shape coefficients of wind loads were different from the current codes, enough attention should be paid to the design.
Long-span light-gauge steel industrial buildings are typical wind-induced sensitive structures, which are prone to wind-induced disasters. The wind load is closely related to the shape of the building. Due to functional requirements,long cantilevered awnings are usually set in industrial buildings. There is no corresponding shape coefficients of wind loads of the cantilevered awning structure on both sides in the current code Load Code for the Design of Building Structures (GB 50009—2012) and Technical Code for Steel Structure of Light-Weight Building with Gabled Frames (GB 51022—2015). Therefore, selecting a reasonable shape coefficient of wind loads becomes the key to wind resistance design. Taking the industrial building with through-length awnings on both sides as the research background, the influence of different overhang lengths and inclination angles of the awnings on the shape coefficients of wind loads at typical positions of the building based on the software Fluent. It was compared with the current code GB 50009—2012 and GB 51022—2015, and provided the wind resistance design suggestions of structure with overhanging awnings. The results indicated that: the length of awning had a significant effect on the upper wall of the awning and the shape coefficient of the awning. The shape coefficient of wind loads on the upper wall of the windward awning changed from positive to negative with the increase of awning length at positive inclination angle, and was positive at negative inclination angle. The shape coefficients of the whole roof and the leeward side were negative, and the length of awning had little effect. The angle of the awning had great influence on the shape coefficient of the awning and the upper wall of the awning on the windward side, but had little influence on the other positions. When the awning angle was positive, the upper wall shape coefficient of the awning was negative and decreased with the increase in the awning angle, and the wind suction of the awning increased with the increase in the awning angle. When the angle of the awning was negative, the shape coefficient of the upper wall of the awning was positive and increased with the increase in the angle, and the wind suction of the awning decreased with the increase in the angle. By comparing with the current codes, GB 50009—2012 and GB 51022—2015, the shape coefficient of the windward awning was -1.37 when the awning length was 8 m and the angle was 0°. The shape coefficient of eaves on the windward side was close to -1.4 in item 16 of table 8.3.1 of Load Code for the Design of Building Structures, but the shape coefficients of wind load at other positions were different. And for other awning lengths and angles corresponding to the structure of the shape coefficients of wind loads were different from the current codes, enough attention should be paid to the design.
2025, 40(1): 58-67.
doi: 10.13206/j.gjgS23122602
Abstract:
Delayed cracks are particularly difficult to detect and can be highly hazardous. Their location is often difficult to predict, and if not identified in a timely manner, the cracks may expand during bridge operation, which usually leads to brittle fracture of the structure and poses a significant threat to the safety of the welded structure. To investigate the location of delayed cracks, a slant Y bevel welding test was designed while considering residual stress. The welding process was monitored using the DIC test system to measure the residual stress generated. The results were compared with the finite element ABAQUS calculated results of welded residual stress to validate and improve the finite element analysis method. Based on the residual stress results after welding, the distribution of diffusible hydrogen was simulated to predict the location of crack emergence. The stress field and diffusible hydrogen enrichment were taken into account for this prediction. In the test to verify the feasibility of the prediction method, the location of delayed crack generation was also observed. This was compared with the finite element prediction results.
The data indicated that: 1) The residual stress distribution in flat plate butt welding structures was inconsistent, with relatively uniform stress in the middle. Longitudinal and transverse stresses were the main residual stress. The stress showed a trend of tensile-pressure distribution, with the longitudinal residual stress in the center of the weld as a large tensile stress, reaching a maximum value of 320 MPa. As the distance between the weld center and the center of the plate decreased, the stress was converted into compressive stress. The residual stress distribution exhibited an 'M’ shape, with a maximum value of 336 MPa. The weld centerline experienced compressive stress. The transverse and longitudinal residual stresses did not exceed the initial yield strength, indicating a self-balancing state within the welded structure. In general, the simulated values of the numerical model and the measured values of residual strain DIC were in good agreement. 2) The distribution of hydrogen concentration in the heat-affected zone was affected by the residual stress gradient, which was higher in the weld zone than in the heat-affected and base metal zones. Additionally, there was a sudden change in residual stress in the transition region from the weld to the heat-affected zone. The distribution of hydrogen concentration in the weld and heat-affected zone was significantly higher than in the surrounding base metal. The root of the weld heat-affected zone exhibited an obvious hydrogen enrichment phenomenon, with the highest concentration of hydrogen in this region. The concentration of hydrogen was the second lowest in the weld area and the lowest in the base metal. As the distance increases, the concentration of hydrogen gradually converged to the initial set concentration. 3) Weld cracks were initiated in the heat-affected zone at the root of the weld. After initiation, the cracks expanded upward in the weld metal and then stopped cracking in the weld. This ensured that the hydrogen-rich and stress-concentrated locations in the finite-element simulation aligned with the location of the test weld crack initiation. The location of crack initiation was determined by the concentration of hydrogen, and changed in the hydrogen-rich area could alter the direction of the cracks.
Delayed cracks are particularly difficult to detect and can be highly hazardous. Their location is often difficult to predict, and if not identified in a timely manner, the cracks may expand during bridge operation, which usually leads to brittle fracture of the structure and poses a significant threat to the safety of the welded structure. To investigate the location of delayed cracks, a slant Y bevel welding test was designed while considering residual stress. The welding process was monitored using the DIC test system to measure the residual stress generated. The results were compared with the finite element ABAQUS calculated results of welded residual stress to validate and improve the finite element analysis method. Based on the residual stress results after welding, the distribution of diffusible hydrogen was simulated to predict the location of crack emergence. The stress field and diffusible hydrogen enrichment were taken into account for this prediction. In the test to verify the feasibility of the prediction method, the location of delayed crack generation was also observed. This was compared with the finite element prediction results.
The data indicated that: 1) The residual stress distribution in flat plate butt welding structures was inconsistent, with relatively uniform stress in the middle. Longitudinal and transverse stresses were the main residual stress. The stress showed a trend of tensile-pressure distribution, with the longitudinal residual stress in the center of the weld as a large tensile stress, reaching a maximum value of 320 MPa. As the distance between the weld center and the center of the plate decreased, the stress was converted into compressive stress. The residual stress distribution exhibited an 'M’ shape, with a maximum value of 336 MPa. The weld centerline experienced compressive stress. The transverse and longitudinal residual stresses did not exceed the initial yield strength, indicating a self-balancing state within the welded structure. In general, the simulated values of the numerical model and the measured values of residual strain DIC were in good agreement. 2) The distribution of hydrogen concentration in the heat-affected zone was affected by the residual stress gradient, which was higher in the weld zone than in the heat-affected and base metal zones. Additionally, there was a sudden change in residual stress in the transition region from the weld to the heat-affected zone. The distribution of hydrogen concentration in the weld and heat-affected zone was significantly higher than in the surrounding base metal. The root of the weld heat-affected zone exhibited an obvious hydrogen enrichment phenomenon, with the highest concentration of hydrogen in this region. The concentration of hydrogen was the second lowest in the weld area and the lowest in the base metal. As the distance increases, the concentration of hydrogen gradually converged to the initial set concentration. 3) Weld cracks were initiated in the heat-affected zone at the root of the weld. After initiation, the cracks expanded upward in the weld metal and then stopped cracking in the weld. This ensured that the hydrogen-rich and stress-concentrated locations in the finite-element simulation aligned with the location of the test weld crack initiation. The location of crack initiation was determined by the concentration of hydrogen, and changed in the hydrogen-rich area could alter the direction of the cracks.
2025, 40(1): 68-73.
doi: 10.13206/j.gjgS23110302
Abstract:
This paper studied the method of calculating the length of the vertical rods of steel pipe fully-supported frames with fasteners in construction. The linear interpolation method for calculating the length coefficient in the current specification:according to Appendix D of Technical Standard for Safety of Steel Tubular Scaffold with Couplers in Construction (T/CECS 699—2020), the step length h of the fully-supported frame or the length a of the vertical rod extending from the center line of the top horizontal rod to the support point increased with a fixed step length, and the initial calculated lengthLC of the vertical pole section was taken as an independent variable, firstly, the calculated length coefficient (μ1 or μ2) of the vertical bar of the fully-supported frame was calculated by linear insertion method, and then the calculated lengthLL of the corresponding vertical rod segment was calculated. The newly proposed direct linear interpolation method for calculating length was as follows:the length coefficient (μ1 or μ2 based on theoretical and experimental results) was calculated according to the specific parameters given in Appendix D of T/CECS 699—2020 (step distance h, distance between vertical poles, length a from the center line of the vertical rod extending out of the top horizontal rod to the support point), firstly, the mechanical calculation lengthLL of the vertical rod section under specific parameters was calculated, and then the step distance h of the fully-supported frame or the length a (or h+2a) of the vertical pole extending from the center line of the top horizontal rod to the support point was increased by a fixed step, and the initial calculated length LC (h+2a orh) of the vertical rod section was taken as the independent variable, then, the corresponding mechanical length LL of the vertical rod segment was calculated by linear insertion method. By analyzing the scatter plots and fitting functions of the mechanical calculation length LL of the vertical rod segment and the initial calculation length LC(a or h+2a, h) of the above two insertion methods, it was found that the calculation results of the linear interpolation method of the calculation length coefficient in the current specification violated the basic principle of linear interpolation (the interpolated dependent variable exceeded the scope of the interpolated dependent variable). Further analysis showed: the initial calculation lengthLC and mechanical calculation length LL in Appendix D of T/CECS 699—2020 were fitted according to linear function with sufficient accuracy, and could be regarded as linear relations; the calculated length L0, the slenderness ratio λ, the stability coefficient φ and the stability bearing capacity were all linear; in the current specification, the function which was actually a concave LC-μ quadratic term or power was wrongly regarded as a linear function, which led to the reason that the calculated lengthLL (or bearing capacity) of the vertical rod segment violated the basic principle of linear interpolation. Based on the measured results and finite element analysis of the stable bearing capacity in relevant literatures, and referring to the calculation method in the current British standard BS 5975[DK]∶2019, a method of directly calculating the length of the vertical rod with linear insert fasteners was proposed, taking the initial calculation length LC (h+2a orh) as the independent variable.
This paper studied the method of calculating the length of the vertical rods of steel pipe fully-supported frames with fasteners in construction. The linear interpolation method for calculating the length coefficient in the current specification:according to Appendix D of Technical Standard for Safety of Steel Tubular Scaffold with Couplers in Construction (T/CECS 699—2020), the step length h of the fully-supported frame or the length a of the vertical rod extending from the center line of the top horizontal rod to the support point increased with a fixed step length, and the initial calculated lengthLC of the vertical pole section was taken as an independent variable, firstly, the calculated length coefficient (μ1 or μ2) of the vertical bar of the fully-supported frame was calculated by linear insertion method, and then the calculated lengthLL of the corresponding vertical rod segment was calculated. The newly proposed direct linear interpolation method for calculating length was as follows:the length coefficient (μ1 or μ2 based on theoretical and experimental results) was calculated according to the specific parameters given in Appendix D of T/CECS 699—2020 (step distance h, distance between vertical poles, length a from the center line of the vertical rod extending out of the top horizontal rod to the support point), firstly, the mechanical calculation lengthLL of the vertical rod section under specific parameters was calculated, and then the step distance h of the fully-supported frame or the length a (or h+2a) of the vertical pole extending from the center line of the top horizontal rod to the support point was increased by a fixed step, and the initial calculated length LC (h+2a orh) of the vertical rod section was taken as the independent variable, then, the corresponding mechanical length LL of the vertical rod segment was calculated by linear insertion method. By analyzing the scatter plots and fitting functions of the mechanical calculation length LL of the vertical rod segment and the initial calculation length LC(a or h+2a, h) of the above two insertion methods, it was found that the calculation results of the linear interpolation method of the calculation length coefficient in the current specification violated the basic principle of linear interpolation (the interpolated dependent variable exceeded the scope of the interpolated dependent variable). Further analysis showed: the initial calculation lengthLC and mechanical calculation length LL in Appendix D of T/CECS 699—2020 were fitted according to linear function with sufficient accuracy, and could be regarded as linear relations; the calculated length L0, the slenderness ratio λ, the stability coefficient φ and the stability bearing capacity were all linear; in the current specification, the function which was actually a concave LC-μ quadratic term or power was wrongly regarded as a linear function, which led to the reason that the calculated lengthLL (or bearing capacity) of the vertical rod segment violated the basic principle of linear interpolation. Based on the measured results and finite element analysis of the stable bearing capacity in relevant literatures, and referring to the calculation method in the current British standard BS 5975[DK]∶2019, a method of directly calculating the length of the vertical rod with linear insert fasteners was proposed, taking the initial calculation length LC (h+2a orh) as the independent variable.
2025, 40(1): 74-78.
doi: 10.13206/j.gjgS24120420
Abstract:
The cross-sectional classification and the related structural performance factors of European, Japan, AISC and China were briefly reviewed and summarized in the paer. Tabulated values revealed that the classifications of AISC specifications were sometimes irregular and confusing; European classification was based on plastic/elastic analysis and cross-sectional moment capacity, but was used in seismic design; Japan and China’s classification was one-to-one correspondent to the system performance factors. Based on results of earlier systematic study, new classifications were proposed.
The cross-sectional classification and the related structural performance factors of European, Japan, AISC and China were briefly reviewed and summarized in the paer. Tabulated values revealed that the classifications of AISC specifications were sometimes irregular and confusing; European classification was based on plastic/elastic analysis and cross-sectional moment capacity, but was used in seismic design; Japan and China’s classification was one-to-one correspondent to the system performance factors. Based on results of earlier systematic study, new classifications were proposed.
