Login
Register
E-alert
2023 Vol. 53, No. 9
Display Method:
2023, 53(9): 1-9.
doi: 10.13204/j.gyjzG23082202
Abstract:
The acceleration of urbanization has brought many challenges to urban safety. How to protect people's lives and property, as well as to ensure the regular operation of the city is an urgent task to be solved. To practically guide the urban safety management, this study proposes a technical system of "prevention-assessment-improvement-response", which is based on the urban safety theory framework of "risk source-risk exposure-mitigation factor", and presents tasks needed to be done in the four stages of this system and its application in Shenzhen. It takes account of all the factors of "risk source-risk exposure-mitigation factor" and provides a new guideline for the urban safety management so as to give systematic solution for urban safety governance.
The acceleration of urbanization has brought many challenges to urban safety. How to protect people's lives and property, as well as to ensure the regular operation of the city is an urgent task to be solved. To practically guide the urban safety management, this study proposes a technical system of "prevention-assessment-improvement-response", which is based on the urban safety theory framework of "risk source-risk exposure-mitigation factor", and presents tasks needed to be done in the four stages of this system and its application in Shenzhen. It takes account of all the factors of "risk source-risk exposure-mitigation factor" and provides a new guideline for the urban safety management so as to give systematic solution for urban safety governance.
2023, 53(9): 10-17.
doi: 10.13204/j.gyjzG23080112
Abstract:
The bolted connection is the most common type of connections in steel structures. Loosening and detachment of bolts can reduce the bearing capacity of the structure and lead to safety hazards. In order to prevent engineering accidents, researchers have proposed many methods of detecting bolt loosening in recent years. The paper reviewed the working principles and research advances of some commonly used bolt loosening detection techniques, including piezoelectric sensing technology, fiber optic sensing technology, digital image processing technology, and percussion acoustic method. The future development direction of bolt failure detection technology was also discussed.
The bolted connection is the most common type of connections in steel structures. Loosening and detachment of bolts can reduce the bearing capacity of the structure and lead to safety hazards. In order to prevent engineering accidents, researchers have proposed many methods of detecting bolt loosening in recent years. The paper reviewed the working principles and research advances of some commonly used bolt loosening detection techniques, including piezoelectric sensing technology, fiber optic sensing technology, digital image processing technology, and percussion acoustic method. The future development direction of bolt failure detection technology was also discussed.
2023, 53(9): 18-28.
doi: 10.13204/j.gyjzG23090107
Abstract:
Steel-plate concrete structure has excellent performance, and has been more and more widely used in buildings, bridges, tunnels and other projects. When applied to nuclear power plants, steel-plate concrete structure shows strong particularity in terms of the stress characteristics, functional requirements and construction. In recent years, a large number of application studies of steel-plate concrete structure in nuclear power plant engineering have been carried out at home and abroad, forming a relatively complete specification system. In the paper, the application and research of steel-plate concrete structure in nuclear power plant engineering were reviewed, including relevant structural design specifications, typical structural forms, mechanical properties and design methods of basic components and units, structural properties and design methods under special working conditions (accident conditions, large aircraft impact, etc.). Finally, according to the special functional requirements of nuclear power plants and the requirements of fine design and construction, the problems that need to be further studied were put forward, including the complex static performance test of various types of steel-plate concrete elements; the mechanical properties and design conditions of steel-plate concrete structure under special working conditions; reasonable and simple structural details, some key construction techniques such as module machining precision, concrete casting temperature and module deformation control, as well as concrete casting compactness and quality control.
Steel-plate concrete structure has excellent performance, and has been more and more widely used in buildings, bridges, tunnels and other projects. When applied to nuclear power plants, steel-plate concrete structure shows strong particularity in terms of the stress characteristics, functional requirements and construction. In recent years, a large number of application studies of steel-plate concrete structure in nuclear power plant engineering have been carried out at home and abroad, forming a relatively complete specification system. In the paper, the application and research of steel-plate concrete structure in nuclear power plant engineering were reviewed, including relevant structural design specifications, typical structural forms, mechanical properties and design methods of basic components and units, structural properties and design methods under special working conditions (accident conditions, large aircraft impact, etc.). Finally, according to the special functional requirements of nuclear power plants and the requirements of fine design and construction, the problems that need to be further studied were put forward, including the complex static performance test of various types of steel-plate concrete elements; the mechanical properties and design conditions of steel-plate concrete structure under special working conditions; reasonable and simple structural details, some key construction techniques such as module machining precision, concrete casting temperature and module deformation control, as well as concrete casting compactness and quality control.
2023, 53(9): 29-44.
doi: 10.13204/j.gyjzG22101827
Abstract:
Traditional and modern restoration and reinforcement techniques involve a wide range of materials and diverse characteristics in the restoration process. A single restoration technique is inadequate to meet the diverse requirements for restoration and reinforcement of wood components with complex cracking mechanisms. Moreover, ancient buildings possess dignity and contain profound history and culture, as well as prominent values in terms of architecture, art, technology, and aesthetics. When it comes to the restoration and reinforcement of cracked and damaged wood components in ancient buildings, the principle of "restore as it was" should be the premise. Firstly, the factors influencing the cracking of wood components and the corresponding mechanisms of material degradation were analyzed. Secondly, based on the analysis of common forms, widths, depths, and structural positions of cracks in wood components, a classification study was conducted on traditional and modern restoration and reinforcement techniques for cracked wood components in ancient buildings. The current status and issues of restoration and reinforcement techniques for cracked wood components were also summarized. Finally, prospects and explorations were conducted regarding the future development direction of restoration and reinforcement techniques for cracked wood components from the aspects of condition assessment, technical coordination and restoration mode.
Traditional and modern restoration and reinforcement techniques involve a wide range of materials and diverse characteristics in the restoration process. A single restoration technique is inadequate to meet the diverse requirements for restoration and reinforcement of wood components with complex cracking mechanisms. Moreover, ancient buildings possess dignity and contain profound history and culture, as well as prominent values in terms of architecture, art, technology, and aesthetics. When it comes to the restoration and reinforcement of cracked and damaged wood components in ancient buildings, the principle of "restore as it was" should be the premise. Firstly, the factors influencing the cracking of wood components and the corresponding mechanisms of material degradation were analyzed. Secondly, based on the analysis of common forms, widths, depths, and structural positions of cracks in wood components, a classification study was conducted on traditional and modern restoration and reinforcement techniques for cracked wood components in ancient buildings. The current status and issues of restoration and reinforcement techniques for cracked wood components were also summarized. Finally, prospects and explorations were conducted regarding the future development direction of restoration and reinforcement techniques for cracked wood components from the aspects of condition assessment, technical coordination and restoration mode.
2023, 53(9): 45-53.
doi: 10.13204/j.gyjzG23081216
Abstract:
The complex hydrological-, thermal-mechanical interactions between permafrost and roadbed engineering exhibit significant scale effects, which are influenced by spatial scale, temporal scale, and structural state. The in-depth understanding of the scale effects of permafrost roadbed is an important theoretical basis for revealing the thawing risk mechanism of large-scale permafrost roadbed and preventing thawing settlement. In recent decades, based on methods such as laboratory and field experiments and numerical analysis, the study of scale effects on permafrost roadbeds has evolved from phenomena to mechanisms, ultimately forming a theoretical system and achieving full development. The theoretical system and research methods of the scale effects of permafrost roadbed were summarized, and the research advances in recent years in terms of upper boundary conditions, spatial effects, time effects, and structural effects were reviewed. Based on this, some ideas were proposed for future research priorities.
The complex hydrological-, thermal-mechanical interactions between permafrost and roadbed engineering exhibit significant scale effects, which are influenced by spatial scale, temporal scale, and structural state. The in-depth understanding of the scale effects of permafrost roadbed is an important theoretical basis for revealing the thawing risk mechanism of large-scale permafrost roadbed and preventing thawing settlement. In recent decades, based on methods such as laboratory and field experiments and numerical analysis, the study of scale effects on permafrost roadbeds has evolved from phenomena to mechanisms, ultimately forming a theoretical system and achieving full development. The theoretical system and research methods of the scale effects of permafrost roadbed were summarized, and the research advances in recent years in terms of upper boundary conditions, spatial effects, time effects, and structural effects were reviewed. Based on this, some ideas were proposed for future research priorities.
2023, 53(9): 54-61.
doi: 10.13204/j.gyjzG23020102
Abstract:
In order to study the influence of the new double-yield-point prefabricated buckling-restrained braces with replaceable core on the seismic performance of the prefabricated steel frame-support structure, firstly the finite element software Perform-3D was used to establish the finite element models of ordinary braces, buckling-restrained braces and new double-yield-point prefabricated buckling-restrained braces with replaceable core and verified the accuracy of the modeling method. Then, on this basis, a finite element model of steel frame-support structure embedded with new double-yield-point buckling-restrained braces with replaceable core was established, and the seismic performances of ordinary steel frame structure, steel frame-ordinary braces structure, steel frame-buckling-restrained braces structure, and steel frame-support structure embedded with new double-yield-point braces were studied by elastoplastic time-history analysis method. The analysis results show that Perform-3D could accurately simulate ordinary steel braces, ordinary buckling-restrained braces and new double-yield-point prefabricated buckling-restrained braces with replaceable core. The steel frame-support structure embedded with the new double-yield-point prefabricated buckling-restrained braces is better than other structures in terms of the maximum interlayer displacement angle and the top layer displacement of the structure and the base shear force. The new double-yield-point prefabricated buckling-restrained braces with replaceable core play an important role under the action of earthquake, mainly through the new double-yield-point prefabricated buckling-restrained braces with replaceable core to consume energy. It indicates that the steel frame-support structure embedded with the new double-yield-point prefabricated buckling-restrained braces with replaceable core shows a good seismic performance.
In order to study the influence of the new double-yield-point prefabricated buckling-restrained braces with replaceable core on the seismic performance of the prefabricated steel frame-support structure, firstly the finite element software Perform-3D was used to establish the finite element models of ordinary braces, buckling-restrained braces and new double-yield-point prefabricated buckling-restrained braces with replaceable core and verified the accuracy of the modeling method. Then, on this basis, a finite element model of steel frame-support structure embedded with new double-yield-point buckling-restrained braces with replaceable core was established, and the seismic performances of ordinary steel frame structure, steel frame-ordinary braces structure, steel frame-buckling-restrained braces structure, and steel frame-support structure embedded with new double-yield-point braces were studied by elastoplastic time-history analysis method. The analysis results show that Perform-3D could accurately simulate ordinary steel braces, ordinary buckling-restrained braces and new double-yield-point prefabricated buckling-restrained braces with replaceable core. The steel frame-support structure embedded with the new double-yield-point prefabricated buckling-restrained braces is better than other structures in terms of the maximum interlayer displacement angle and the top layer displacement of the structure and the base shear force. The new double-yield-point prefabricated buckling-restrained braces with replaceable core play an important role under the action of earthquake, mainly through the new double-yield-point prefabricated buckling-restrained braces with replaceable core to consume energy. It indicates that the steel frame-support structure embedded with the new double-yield-point prefabricated buckling-restrained braces with replaceable core shows a good seismic performance.
2023, 53(9): 62-68.
doi: 10.13204/j.gyjzG23081701
Abstract:
A prefabricated composite structure system composed of concrete-filled steel tubular columns, steel beams, and composite slabs without protruding rebars was proposed in response to the requirements and structural characteristics of electronic chip plants. Compared to traditional cast-in-place concrete structures, the new composite structure incurs a 33% increase in material costs but reduces the construction period by 28% and diminishes the template engineering quantity by 46%, resulting in substantial overall benefits. Moreover, a numerical analysis was conducted on the prefabricated composite frame structure and the traditional cast-in-place concrete structure. The prefabricated composite structure was observed to have better seismic resistance by decreasing the interlayer displacement angle under earthquake conditions while maintaining the same natural vibration characteristics and failure modes as the traditional structure. However, it is important to note that in comparison to the cast-in-place concrete structure system, the floor's natural vibration frequency using the prefabricated composite system decreased from 51.6 Hz to 30.1 Hz, and the vertical deflection under live load increased from 0.15 mm to 0.39 mm. Therefore, the applicability of the system for electronic workshops that are sensitive to micro-vibrations still needs to be further explored.
A prefabricated composite structure system composed of concrete-filled steel tubular columns, steel beams, and composite slabs without protruding rebars was proposed in response to the requirements and structural characteristics of electronic chip plants. Compared to traditional cast-in-place concrete structures, the new composite structure incurs a 33% increase in material costs but reduces the construction period by 28% and diminishes the template engineering quantity by 46%, resulting in substantial overall benefits. Moreover, a numerical analysis was conducted on the prefabricated composite frame structure and the traditional cast-in-place concrete structure. The prefabricated composite structure was observed to have better seismic resistance by decreasing the interlayer displacement angle under earthquake conditions while maintaining the same natural vibration characteristics and failure modes as the traditional structure. However, it is important to note that in comparison to the cast-in-place concrete structure system, the floor's natural vibration frequency using the prefabricated composite system decreased from 51.6 Hz to 30.1 Hz, and the vertical deflection under live load increased from 0.15 mm to 0.39 mm. Therefore, the applicability of the system for electronic workshops that are sensitive to micro-vibrations still needs to be further explored.
2023, 53(9): 69-77.
doi: 10.13204/j.gyjzG21111011
Abstract:
18 specimens of concrete-filled circular steel tubular long columns were tested for corrosion and subsequently subjected to eccentric compression. The specimens with different corrosion degrees were obtained by accelerated corrosion of electricity. After the corrosion, eccentric compression tests were carried out to explore the effects of local corrosion on the mechanical properties of the circular concrete-filled steel tubes. Three theoretical analysis models of locally corroded circular concrete-filled steel tubes under eccentric compression were established by ABAQUS finite element program, including uniform corrosion, macro uneven corrosion and micro uneven corrosion, which provided references for the locally-corroded concrete-filled circular steel tubular models. The results showed that the locally-corroded concrete-filled circular steel tubes suffered cross-section crush failure. The ultimate bearing capacity decreased with the increase of corrosion rate, circumferential corrosion rate, eccentricity and slenderness ratio. Compared with the uncorroded specimens, when the geometric parameters were the same as the corrosion area, and the corrosion rate increased to 20.00%, the ultimate bearing capacity decreased by 11.70%. When establishing a finite element model of locally-corroded concrete-filled circular steel tube, it was recommended to select different corrosion models according to the surfaces of the corroded steel tubes.
18 specimens of concrete-filled circular steel tubular long columns were tested for corrosion and subsequently subjected to eccentric compression. The specimens with different corrosion degrees were obtained by accelerated corrosion of electricity. After the corrosion, eccentric compression tests were carried out to explore the effects of local corrosion on the mechanical properties of the circular concrete-filled steel tubes. Three theoretical analysis models of locally corroded circular concrete-filled steel tubes under eccentric compression were established by ABAQUS finite element program, including uniform corrosion, macro uneven corrosion and micro uneven corrosion, which provided references for the locally-corroded concrete-filled circular steel tubular models. The results showed that the locally-corroded concrete-filled circular steel tubes suffered cross-section crush failure. The ultimate bearing capacity decreased with the increase of corrosion rate, circumferential corrosion rate, eccentricity and slenderness ratio. Compared with the uncorroded specimens, when the geometric parameters were the same as the corrosion area, and the corrosion rate increased to 20.00%, the ultimate bearing capacity decreased by 11.70%. When establishing a finite element model of locally-corroded concrete-filled circular steel tube, it was recommended to select different corrosion models according to the surfaces of the corroded steel tubes.
2023, 53(9): 78-87.
doi: 10.13204/j.gyjzG23051702
Abstract:
Currently, the connection of prefabricated steel beams often adopts the form of high-strength bolt end-plate splices. The beam components are manufactured in the factory and thus have high manufacture procision. When the beam components arrive at the construction site, high-strength bolts are used to complete the splicing, which is fast and convenient for installation. However, there are often assembly gaps between the end plates of prefabricated steel beams, and filler plates are often used to fill these gaps in the construction process. At present, there is no regulation in the design code regarding the influence of filler plates. In order to study the effect of filler plate on the bending stiffness and bending capacity of end-plate splice, finite element software ABAQUS was used to establish a solid element model of end-plate splice with filler plate, the complex contact relations between these components were set up. By considering the effects of thicknesses of end-plate and filler plate, the paper investigated the working mechanism of the tensile force transmitted by high-strength bolts, the position changes of the neutral axis, the stress state of the filler plate, and the ultimate stress state of the end-plate in the tensile zone. The analysis results indicated that for the H-section steel beam H400×200×8×13 and filler plate -400×200×tp1(tp1=12-24 mm), the initial bending stiffness of the end-plate beam splice increased with the increase of the filler plate thickness, when the filler plate thickness was within 15 mm, the bending capacity of the end-plate beam splice was not significantly influenced by the filler plate thickness.
Currently, the connection of prefabricated steel beams often adopts the form of high-strength bolt end-plate splices. The beam components are manufactured in the factory and thus have high manufacture procision. When the beam components arrive at the construction site, high-strength bolts are used to complete the splicing, which is fast and convenient for installation. However, there are often assembly gaps between the end plates of prefabricated steel beams, and filler plates are often used to fill these gaps in the construction process. At present, there is no regulation in the design code regarding the influence of filler plates. In order to study the effect of filler plate on the bending stiffness and bending capacity of end-plate splice, finite element software ABAQUS was used to establish a solid element model of end-plate splice with filler plate, the complex contact relations between these components were set up. By considering the effects of thicknesses of end-plate and filler plate, the paper investigated the working mechanism of the tensile force transmitted by high-strength bolts, the position changes of the neutral axis, the stress state of the filler plate, and the ultimate stress state of the end-plate in the tensile zone. The analysis results indicated that for the H-section steel beam H400×200×8×13 and filler plate -400×200×tp1(tp1=12-24 mm), the initial bending stiffness of the end-plate beam splice increased with the increase of the filler plate thickness, when the filler plate thickness was within 15 mm, the bending capacity of the end-plate beam splice was not significantly influenced by the filler plate thickness.
2023, 53(9): 88-94.
doi: 10.13204/j.gyjzG23072910
Abstract:
In order to study the flexural performance of variable-section inverted trapezoidal steel beams, the scaled specimens were designed, and four-point static loading tests were carried out, which were compared and analyzed with numerical simulations to reveal the stress distribution law of variable-section inverted trapezoidal beams under vertical loading. The results showed that the flexural capacity of the scaled specimen reached 770 kN, and the in-plane flexural performance was excellent, and there was no instability problem in the test. The numerical model exhibited the same deformation characteristics and the same stress distribution as the test results, and the error in the flexural capacity was 3.9%, and the error in the initial stiffness was 12.4%. Compared with the most unfavorable loading condition of the actual project, the safety coefficient of the bearing capacity of the variable cross-section inverted trapezoidal steel beam was 12.4. The deflection of the member under the design load is 4.14 mm, and it is in elastic stress state, which meets the deflection and engineering safety requirements.
In order to study the flexural performance of variable-section inverted trapezoidal steel beams, the scaled specimens were designed, and four-point static loading tests were carried out, which were compared and analyzed with numerical simulations to reveal the stress distribution law of variable-section inverted trapezoidal beams under vertical loading. The results showed that the flexural capacity of the scaled specimen reached 770 kN, and the in-plane flexural performance was excellent, and there was no instability problem in the test. The numerical model exhibited the same deformation characteristics and the same stress distribution as the test results, and the error in the flexural capacity was 3.9%, and the error in the initial stiffness was 12.4%. Compared with the most unfavorable loading condition of the actual project, the safety coefficient of the bearing capacity of the variable cross-section inverted trapezoidal steel beam was 12.4. The deflection of the member under the design load is 4.14 mm, and it is in elastic stress state, which meets the deflection and engineering safety requirements.
2023, 53(9): 95-103.
doi: 10.13204/j.gyjzG23080410
Abstract:
To study the effect of corrosion on the slip factors of weathering high-strength bolts, the slip factor tests under different corrosion times were conducted on 23 high-strength bolted connecting specimens cleaned by sandblasting and manual cleaning. The test includes 10 specimens composed of Q355GNH weathering steel and NHL10 weathering high-strength bolts, 10 specimens composed of Q355B ordinary steel and NHL10 weathering high-strength bolts, and 3 specimens composed of Q355GNH weathering steel and ML20MnTiB ordinary high-strength bolts. The effects of different surface treatments and materials on the slip factors of weathering high-strength bolted connections were studied. The test results showed that the surface treatment had no noticeable effect on the corrosion rate and speed of the steel plates; the bearing capacity of the weathering high-strength bolted connecting specimens after sandblasting was higher, and the slip factors were more stable; for the connecting specimens composed of weathering steel plates and ordinary high-strength bolts, due to the existence of corrosion potential difference, the time for the corrosion rate of weathering steel plates to stabilize was prolonged; at the same corrosion time, the slip factors of the specimens composed weathering steel plate and weathering high-strength bolts were less affected by corrosion, so the specimens would be more suitable for severe corrosion environments.
To study the effect of corrosion on the slip factors of weathering high-strength bolts, the slip factor tests under different corrosion times were conducted on 23 high-strength bolted connecting specimens cleaned by sandblasting and manual cleaning. The test includes 10 specimens composed of Q355GNH weathering steel and NHL10 weathering high-strength bolts, 10 specimens composed of Q355B ordinary steel and NHL10 weathering high-strength bolts, and 3 specimens composed of Q355GNH weathering steel and ML20MnTiB ordinary high-strength bolts. The effects of different surface treatments and materials on the slip factors of weathering high-strength bolted connections were studied. The test results showed that the surface treatment had no noticeable effect on the corrosion rate and speed of the steel plates; the bearing capacity of the weathering high-strength bolted connecting specimens after sandblasting was higher, and the slip factors were more stable; for the connecting specimens composed of weathering steel plates and ordinary high-strength bolts, due to the existence of corrosion potential difference, the time for the corrosion rate of weathering steel plates to stabilize was prolonged; at the same corrosion time, the slip factors of the specimens composed weathering steel plate and weathering high-strength bolts were less affected by corrosion, so the specimens would be more suitable for severe corrosion environments.
2023, 53(9): 104-110.
doi: 10.13204/j.gyjzG23051114
Abstract:
A new type of double-stage-yield annular steel plate shear damper, DASPSD, was proposed, which is mainly composed of two connecting plates, an inner circular metal damper, and an outer circular metal damper. The inner and outer dampers are equipped with corresponding connectors. The damper has double-stage working mechanism and double-stage-yield energy dissipation characteristics, which is beneficial for mitigating the inter-story deformation concentration effect of frame structures. Firstly, refined numerical simulations were conducted on DASPSD with different parameters to validate the double-stage working mechanism and the double-stage-yield characteristics of the damper. The influence of key design parameters on the mechanical performance of DASPSD was revealed. Secondly, based on nonlinear time history analysis, the superiority of DASPSD in controlling the maximum inter-story drift ratio and the drift concentration effect compared to traditional single-stage U-shaped dampers was clarified.
A new type of double-stage-yield annular steel plate shear damper, DASPSD, was proposed, which is mainly composed of two connecting plates, an inner circular metal damper, and an outer circular metal damper. The inner and outer dampers are equipped with corresponding connectors. The damper has double-stage working mechanism and double-stage-yield energy dissipation characteristics, which is beneficial for mitigating the inter-story deformation concentration effect of frame structures. Firstly, refined numerical simulations were conducted on DASPSD with different parameters to validate the double-stage working mechanism and the double-stage-yield characteristics of the damper. The influence of key design parameters on the mechanical performance of DASPSD was revealed. Secondly, based on nonlinear time history analysis, the superiority of DASPSD in controlling the maximum inter-story drift ratio and the drift concentration effect compared to traditional single-stage U-shaped dampers was clarified.
2023, 53(9): 111-118.
doi: 10.13204/j.gyjzG22091505
Abstract:
Based on the equivalent diagonal web truss-arch model and considering different failure modes and deformation coordination conditions, a method for calculating the shear capacity of small shear-span ratio shear walls was proposed. The effects of both horizontal and vertical reinforcements in the web on the shear capacity of the member through the strain equivalence principle in the truss action were considered in the method, and an empirical formula to calculate the height of the compression zone for determining the section height of the concrete diagonal compression strut were also proposed. The test data of 359 small shear-span ratio shear walls were collected, and their shear capacity was calculated by using the method proposed in the paper, and compared with the Chinese, American, European and Japanese codes. The results showed that except for the Japanese AIJ code, the calculation of shear capacity of small shear-span ratio shear walls were conservative, while the AIJ code overestimated the height of the arch bar, which made its calculation results unsafe; while the proposed formula could calculate the shear bearing capacity of small shear-span ratio shear walls more accurately.
Based on the equivalent diagonal web truss-arch model and considering different failure modes and deformation coordination conditions, a method for calculating the shear capacity of small shear-span ratio shear walls was proposed. The effects of both horizontal and vertical reinforcements in the web on the shear capacity of the member through the strain equivalence principle in the truss action were considered in the method, and an empirical formula to calculate the height of the compression zone for determining the section height of the concrete diagonal compression strut were also proposed. The test data of 359 small shear-span ratio shear walls were collected, and their shear capacity was calculated by using the method proposed in the paper, and compared with the Chinese, American, European and Japanese codes. The results showed that except for the Japanese AIJ code, the calculation of shear capacity of small shear-span ratio shear walls were conservative, while the AIJ code overestimated the height of the arch bar, which made its calculation results unsafe; while the proposed formula could calculate the shear bearing capacity of small shear-span ratio shear walls more accurately.
2023, 53(9): 119-127.
doi: 10.13204/j.gyjzG23022811
Abstract:
Ultra high performance concrete (UHPC) is a kind of cementitious composite material with high strength and durability, and can achieve a new type of fully-prefabricated floor structure with high construction efficiency that is difficult to construct with traditional concrete materials. The performance of the UHPC joint between prefabricated slabs is directly related to the overall performance of floor, and its critical issues are the transmission mechanism and mechanical properties of shear and tensile forces. In order to clarify the mechanical properties of UHPC joints, four tensile tests and seven shear tests were conducted to explore the effects of rebar lap length and shear groove construction on the mechanical properties of the joint, and to analyze the crack development, damage pattern, strain development law and load-displacement curve of the specimens with different parameters. The research results showed that when the lap length of rebars was 12 times diameter, the tensile strength and shear strength of longitudinal rebars in the joint could be fully developed. In addition, the shear groove could significantly improve the shear capacity of the joint, and the shear resistance of the joint could exceed that of the prefabricated slab with shear groove configuration and 8 rebar lap length of 8 times diameter.
Ultra high performance concrete (UHPC) is a kind of cementitious composite material with high strength and durability, and can achieve a new type of fully-prefabricated floor structure with high construction efficiency that is difficult to construct with traditional concrete materials. The performance of the UHPC joint between prefabricated slabs is directly related to the overall performance of floor, and its critical issues are the transmission mechanism and mechanical properties of shear and tensile forces. In order to clarify the mechanical properties of UHPC joints, four tensile tests and seven shear tests were conducted to explore the effects of rebar lap length and shear groove construction on the mechanical properties of the joint, and to analyze the crack development, damage pattern, strain development law and load-displacement curve of the specimens with different parameters. The research results showed that when the lap length of rebars was 12 times diameter, the tensile strength and shear strength of longitudinal rebars in the joint could be fully developed. In addition, the shear groove could significantly improve the shear capacity of the joint, and the shear resistance of the joint could exceed that of the prefabricated slab with shear groove configuration and 8 rebar lap length of 8 times diameter.
2023, 53(9): 128-137.
doi: 10.13204/j.gyjzG23072411
Abstract:
As a typical structure of the prefabricated shear wall buildings, the bottom joint with characteristic of narrow space is prone to hidden defects such as void and leakiness during the process of construction. To achieve effective detection of construction defects in the bottom joint of the prefabricated shear wall structure, both numerical simulation and experimental methods were used to study different detection methods based on the ultrasonic longitudinal wave. Theoretical analysis of the recognition capability of single-side testing method and penetration testing method for different defects in the bottom joints was conducted to select appropriate testing methods and parameters for the rapid detection of construction defects, then the laboratory specimen testing and engineering application were adopted to verify the theoretical analysis results. The results showed that both the single-side testing method and penetration testing method could effectively identify the construction defects in the bottom joints. The variation amplitude of the direct wave of longitudinal wave at the defect location was larger than the corresponding value of the propagation speed, therefore, the signal amplitude of the direct wave was preferred as the primary indicator for judging the defect. The single-side testing method is suitable for the rapid detection of the entire bottom joint, while the penetration testing method is referred to spot-check. During the field detection, advantages of the two testing methods can be integrated to achieve rapid and refined identification of defects in the bottom joints.
As a typical structure of the prefabricated shear wall buildings, the bottom joint with characteristic of narrow space is prone to hidden defects such as void and leakiness during the process of construction. To achieve effective detection of construction defects in the bottom joint of the prefabricated shear wall structure, both numerical simulation and experimental methods were used to study different detection methods based on the ultrasonic longitudinal wave. Theoretical analysis of the recognition capability of single-side testing method and penetration testing method for different defects in the bottom joints was conducted to select appropriate testing methods and parameters for the rapid detection of construction defects, then the laboratory specimen testing and engineering application were adopted to verify the theoretical analysis results. The results showed that both the single-side testing method and penetration testing method could effectively identify the construction defects in the bottom joints. The variation amplitude of the direct wave of longitudinal wave at the defect location was larger than the corresponding value of the propagation speed, therefore, the signal amplitude of the direct wave was preferred as the primary indicator for judging the defect. The single-side testing method is suitable for the rapid detection of the entire bottom joint, while the penetration testing method is referred to spot-check. During the field detection, advantages of the two testing methods can be integrated to achieve rapid and refined identification of defects in the bottom joints.
2023, 53(9): 138-148.
doi: 10.13204/j.gyjzG22102603
Abstract:
Based on the engineering background of reconstruction photovoltaic systems on the light-gauge steel structure roofs of many existing industrial buildings, two categories of reinforcing techniques using prestressed CFRP laminates are applied to reinforce the purlins of such structures. The former uses hydraulic jack to prestress the CFRP laminate, which is close to the lower flange of steel purlin; and the latter uses a prestressing chair at the midspan of the steel purlin to prestress the CFRP laminate, thus the CFRP laminate is far away from the lower flange of the steel purlin and forms a triangular shape. Firstly, the reinforcement mechanisms of the two reinforcing techniques were analyzed. Secondly, based on current codes in China, the direct strength method was applied to form a calculation method of the bearing capacity and the deformation of the reinforced steel purlin, which considered the correlation between the local buckling and strength failure of the reinforced steel purlin and the increase of prestress caused by the deformation of CFRP laminate. The calculation results had good accuracy and the influencing tendencies of the parameters were obtained. It was found that using a large stiffness of CFRP, a large supporting length, and a large prestress value led to a high reinforcing efficiency. Based on this, considering the practical limitations of maximum prestress in the reinforcing stage, CFRP laminate strength and maximum deformation of the reinforced steel purlin, a design method of the reinforced steel purlin was established, and design examples of such steel purlins were given for flexural strength or local buckling enhancement. Through the comparisons of design examples, different applicable conditions of the two categories of reinforcing techniques were obtained. The technique of using prestressed CFRP with prestressing chair was easier to achieve a significant increase in flexural capacity and stiffness. This paper provided references of reinforcing steel purlins with prestressed CFRPs in real engineering.
Based on the engineering background of reconstruction photovoltaic systems on the light-gauge steel structure roofs of many existing industrial buildings, two categories of reinforcing techniques using prestressed CFRP laminates are applied to reinforce the purlins of such structures. The former uses hydraulic jack to prestress the CFRP laminate, which is close to the lower flange of steel purlin; and the latter uses a prestressing chair at the midspan of the steel purlin to prestress the CFRP laminate, thus the CFRP laminate is far away from the lower flange of the steel purlin and forms a triangular shape. Firstly, the reinforcement mechanisms of the two reinforcing techniques were analyzed. Secondly, based on current codes in China, the direct strength method was applied to form a calculation method of the bearing capacity and the deformation of the reinforced steel purlin, which considered the correlation between the local buckling and strength failure of the reinforced steel purlin and the increase of prestress caused by the deformation of CFRP laminate. The calculation results had good accuracy and the influencing tendencies of the parameters were obtained. It was found that using a large stiffness of CFRP, a large supporting length, and a large prestress value led to a high reinforcing efficiency. Based on this, considering the practical limitations of maximum prestress in the reinforcing stage, CFRP laminate strength and maximum deformation of the reinforced steel purlin, a design method of the reinforced steel purlin was established, and design examples of such steel purlins were given for flexural strength or local buckling enhancement. Through the comparisons of design examples, different applicable conditions of the two categories of reinforcing techniques were obtained. The technique of using prestressed CFRP with prestressing chair was easier to achieve a significant increase in flexural capacity and stiffness. This paper provided references of reinforcing steel purlins with prestressed CFRPs in real engineering.
2023, 53(9): 149-155.
doi: 10.13204/j.gyjzG23072614
Abstract:
Through shear tests on 12 polyethylene fiber-reinforced engineered cementitious composite (PE-ECC) V-notched beams, the effects of different mix proportion and fiber content on the shear performance of V-notched PE-ECC beams were studied. The test results showed that the V-notched beam with pure matrix was obvious brittle damage, while the V-notched PE-ECC beam was ductile damage. The cracks of the V-notched PE-ECC beams mainly appeared in the region between the loading point and the support on both sides of the notch, and the V-notched PE-ECC beams exhibited multi-cracking characteristics. When the load reached the peak load, the specimen shows the main crack and the specimen had obvious deflection. When the fiber content is in the range of 0%-2%, the shear capacity and ductility of V-notched PE-ECC beams increased with the increase of fiber content, and the crack propagation of the specimens with 2% fiber content was more sufficient than that of the specimens with 1% fiber content, while the average shear strength of PE-ECC was 9.46 MPa, which was 1.79 times of the axial tensile strength, when the fiber content is 2%.
Through shear tests on 12 polyethylene fiber-reinforced engineered cementitious composite (PE-ECC) V-notched beams, the effects of different mix proportion and fiber content on the shear performance of V-notched PE-ECC beams were studied. The test results showed that the V-notched beam with pure matrix was obvious brittle damage, while the V-notched PE-ECC beam was ductile damage. The cracks of the V-notched PE-ECC beams mainly appeared in the region between the loading point and the support on both sides of the notch, and the V-notched PE-ECC beams exhibited multi-cracking characteristics. When the load reached the peak load, the specimen shows the main crack and the specimen had obvious deflection. When the fiber content is in the range of 0%-2%, the shear capacity and ductility of V-notched PE-ECC beams increased with the increase of fiber content, and the crack propagation of the specimens with 2% fiber content was more sufficient than that of the specimens with 1% fiber content, while the average shear strength of PE-ECC was 9.46 MPa, which was 1.79 times of the axial tensile strength, when the fiber content is 2%.
2023, 53(9): 156-161.
doi: 10.13204/j.gyjzG23081402
Abstract:
China has a large scale of new and existing buildings, but in recent years, building safety accidents have occurred frequently. Research studies have shown that building safety accidents are closely related to design. By improving or optimizing the design, the safety level of the full life cycle of the building can be effectively improved. At the same time, conducting safety control throughout the full life cycle of buildings during the design phase has low cost and high efficiency. Therefore, conducting safety design research is of great significance for safety control throughout the full life cycle of buildings. Based on the Shenzhen Bay Super Headquarters Tower C project, breaking the traditional design mode in the design phase was broken and a joint design team consisting of construction party, design, safety consulting, contractor, and property management was formed. In addition to considering the needs of occupational safety and health in the design, a safety design concept of full life cycle, general scenario, multi-hazards was innovatively proposed, and was applied to the design of the Shenzhen Bay Super Headquarters Tower C to effectively prevent and reduce the occurrence of safety accidents during the subsequent construction and operation phases of the Tower C project. Finally, corresponding strategies and suggestions were proposed for the difficulties encountered in the safety design process. Through this innovative practice, it provided a useful reference for the application and promotion of safety design concepts in high-rise building design in China.
China has a large scale of new and existing buildings, but in recent years, building safety accidents have occurred frequently. Research studies have shown that building safety accidents are closely related to design. By improving or optimizing the design, the safety level of the full life cycle of the building can be effectively improved. At the same time, conducting safety control throughout the full life cycle of buildings during the design phase has low cost and high efficiency. Therefore, conducting safety design research is of great significance for safety control throughout the full life cycle of buildings. Based on the Shenzhen Bay Super Headquarters Tower C project, breaking the traditional design mode in the design phase was broken and a joint design team consisting of construction party, design, safety consulting, contractor, and property management was formed. In addition to considering the needs of occupational safety and health in the design, a safety design concept of full life cycle, general scenario, multi-hazards was innovatively proposed, and was applied to the design of the Shenzhen Bay Super Headquarters Tower C to effectively prevent and reduce the occurrence of safety accidents during the subsequent construction and operation phases of the Tower C project. Finally, corresponding strategies and suggestions were proposed for the difficulties encountered in the safety design process. Through this innovative practice, it provided a useful reference for the application and promotion of safety design concepts in high-rise building design in China.
2023, 53(9): 162-169.
doi: 10.13204/j.gyjzG23081006
Abstract:
As one of China's key industries and economic pillars, the construction industry has long been plagued by low productivity and limited levels of automation. However, large language models present new possibilities for industry advancement. This paper proposes an application framework for large language models in construction engineering, utilizing prompt engineering and a local knowledge base to enhance model performance. The effectiveness of the proposed framework is validated through experimental analysis, exploring its feasibility in various domains within the industry and providing detailed application examples for specific tasks. The experimental results indicate that although there is still room for improvement in tackling complex problems, large language models have already demonstrated their potential to replace certain text-related tasks in construction engineering, offering a new direction for the future development of the construction industry.
As one of China's key industries and economic pillars, the construction industry has long been plagued by low productivity and limited levels of automation. However, large language models present new possibilities for industry advancement. This paper proposes an application framework for large language models in construction engineering, utilizing prompt engineering and a local knowledge base to enhance model performance. The effectiveness of the proposed framework is validated through experimental analysis, exploring its feasibility in various domains within the industry and providing detailed application examples for specific tasks. The experimental results indicate that although there is still room for improvement in tackling complex problems, large language models have already demonstrated their potential to replace certain text-related tasks in construction engineering, offering a new direction for the future development of the construction industry.
