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2022 Vol. 52, No. 6
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2022, 52(6): 1-6,39.
doi: 10.13204/j.gyjzG21111905
Abstract:
In order to popularize PHC uplift pipe pile in UHV transmission line pile foundation, the uplift bearing performance of the bonding surface between core concrete and the inner wall of pipe pile was investigated. The full-scale tests of 6 PHC 600 B 130 uplift piles were completed. In the test, different core filling lengths and interface treatment methods of the inner wall of the pipe pile were considered, the test results of axial tension, average bond strength of the interface, bond coefficients of the interface, and slip were obtained. The results showed that the maximum axial tensile force of each specimen increased linearly with the increase of core length. The average bond strength test value of the whole length of the core filled concrete interface was between 0.603 MPa and 0.774 MPa, and the core filling length and interface treatment method had little influence on the test results. Along the whole length of the pipe pile core filling, the bond strength and slip of the core filling concrete interface on each section were larger near the loading end while smaller away from the loading end. The core filling concrete near the loading end bears a larger proportion of axial tensile load. The design value of the average bond strength of the whole length of the core concrete interface could be taken as 0.30 MPa.
In order to popularize PHC uplift pipe pile in UHV transmission line pile foundation, the uplift bearing performance of the bonding surface between core concrete and the inner wall of pipe pile was investigated. The full-scale tests of 6 PHC 600 B 130 uplift piles were completed. In the test, different core filling lengths and interface treatment methods of the inner wall of the pipe pile were considered, the test results of axial tension, average bond strength of the interface, bond coefficients of the interface, and slip were obtained. The results showed that the maximum axial tensile force of each specimen increased linearly with the increase of core length. The average bond strength test value of the whole length of the core filled concrete interface was between 0.603 MPa and 0.774 MPa, and the core filling length and interface treatment method had little influence on the test results. Along the whole length of the pipe pile core filling, the bond strength and slip of the core filling concrete interface on each section were larger near the loading end while smaller away from the loading end. The core filling concrete near the loading end bears a larger proportion of axial tensile load. The design value of the average bond strength of the whole length of the core concrete interface could be taken as 0.30 MPa.
2022, 52(6): 7-11,54.
doi: 10.13204/j.gyjzG21111710
Abstract:
In order to improve the insufficient shear capacity of prestressed high strength concrete (PHC) pipe pile head after pile cutting, two reinforcement measures of internal filling concrete core and external wrapping carbon fiber sheet (CFRP) were considered respectively, and the static load test of shear bearing capacity of five full-scale PHC pipe pile specimens (PHC 400 B 95) was completed. The data of cracking shear force, ultimate shear force, failure mode and pile strain deformation were obtained, the enhancement effects of different reinforcement measures on the shear bearing capacity of PHC pipe pile specimens were analyzed, and the reliability of the calculation results of the formula of shear bearing capacity of pile head strengthened with carbon fiber sheet was verified. The results showed that compared with PHC pipe pile with concrete core filling, carbon fiber sheet had better effect on strengthening the shear bearing capacity of pile head after pile cutting, and the shear failure mode of pile head changed to bending failure mode, which delayed the cracking and crushing of pile head concrete and improves the ductility of pile head; according to the analysis of test data, the formula of shear bearing capacity of pile head strengthened with carbon fiber sheet was put forward. The calculation results were safe and reliable, which could be used in engineering design.
In order to improve the insufficient shear capacity of prestressed high strength concrete (PHC) pipe pile head after pile cutting, two reinforcement measures of internal filling concrete core and external wrapping carbon fiber sheet (CFRP) were considered respectively, and the static load test of shear bearing capacity of five full-scale PHC pipe pile specimens (PHC 400 B 95) was completed. The data of cracking shear force, ultimate shear force, failure mode and pile strain deformation were obtained, the enhancement effects of different reinforcement measures on the shear bearing capacity of PHC pipe pile specimens were analyzed, and the reliability of the calculation results of the formula of shear bearing capacity of pile head strengthened with carbon fiber sheet was verified. The results showed that compared with PHC pipe pile with concrete core filling, carbon fiber sheet had better effect on strengthening the shear bearing capacity of pile head after pile cutting, and the shear failure mode of pile head changed to bending failure mode, which delayed the cracking and crushing of pile head concrete and improves the ductility of pile head; according to the analysis of test data, the formula of shear bearing capacity of pile head strengthened with carbon fiber sheet was put forward. The calculation results were safe and reliable, which could be used in engineering design.
2022, 52(6): 12-18.
doi: 10.13204/j.gyjzG22011208
Abstract:
The PHC pipe pile-cap joint is in a complex stress environment, and its mechanical mechanism needs to be further studied. ABAQUS finite element software was used to establish the calculation model of core reinforced concrete-filled pile-cap joint, and the mechanical mechanism of the joint under the combined loading condition of tension and the bending moment was studied. The effects of the embedded depth of pile, the height of cap on the stress distribution and the tensile capacity of the pile were investigated. The calculation results showed that the load-displacement curves of core reinforced concrete-filled pile-cap joint and the damage characteristics of pipe pile and cap calculated by finite element analysis were close to the experimental results. With the increase of pile embedment depth and cap height, the initial stiffness and bearing capacity of the joint increased significantly. When the embedded depth of pipe pile was small, the stiffness of joint was mainly caused by the yield of prestressed reinforcement, anchor reinforcement and the damage of concrete components. When the embedded depth of pipe pile was large or the height of cap was small, the overall stiffness of joint was decreased due to the damage of concrete components.
The PHC pipe pile-cap joint is in a complex stress environment, and its mechanical mechanism needs to be further studied. ABAQUS finite element software was used to establish the calculation model of core reinforced concrete-filled pile-cap joint, and the mechanical mechanism of the joint under the combined loading condition of tension and the bending moment was studied. The effects of the embedded depth of pile, the height of cap on the stress distribution and the tensile capacity of the pile were investigated. The calculation results showed that the load-displacement curves of core reinforced concrete-filled pile-cap joint and the damage characteristics of pipe pile and cap calculated by finite element analysis were close to the experimental results. With the increase of pile embedment depth and cap height, the initial stiffness and bearing capacity of the joint increased significantly. When the embedded depth of pipe pile was small, the stiffness of joint was mainly caused by the yield of prestressed reinforcement, anchor reinforcement and the damage of concrete components. When the embedded depth of pipe pile was large or the height of cap was small, the overall stiffness of joint was decreased due to the damage of concrete components.
2022, 52(6): 19-24,60.
doi: 10.13204/j.gyjzG21122311
Abstract:
On the question of the shear capacity of PHC pipe pile, different calculations were proposed in the current specifications and collective drawings. In order to explore the ultimate shear capacity of PHC pipe pile with large diameters, ABAQUS numerical simulation software was used to analyze the shear capacity of PHC pipe pile which was commonly used in engineering and has large diameters (600~1 000 mm), on the basis of the calculation results of the current specifications and the results of previous experiments. By analyzing the shear capacity of concrete and stirrup on the failure surface with shear span ratio of 1.5~3.0 and during shear compression failure, the major conclusions were as follows: the shear capacity of pipe pile showed a fluctuating decline during the decline process; the pipe pile’s maximum shear capacity was not synchronized with the failure of the pipe pile; when the maximum shear capacity is reached, the tensile cracks had occurred in the concrete upper neutral axis of the pipe pile. With the progress of displacement loading, when the tensile cracks were basically penetrated, the pile concrete had destroyed, the stirrup stress had increased, and the stirrup had yielded but the stirrup did not break. Finally, a formula for the shear capacity of PHC pipe pile was proposed on the basis of the current formula and the 45° fracture surface assumption.
On the question of the shear capacity of PHC pipe pile, different calculations were proposed in the current specifications and collective drawings. In order to explore the ultimate shear capacity of PHC pipe pile with large diameters, ABAQUS numerical simulation software was used to analyze the shear capacity of PHC pipe pile which was commonly used in engineering and has large diameters (600~1 000 mm), on the basis of the calculation results of the current specifications and the results of previous experiments. By analyzing the shear capacity of concrete and stirrup on the failure surface with shear span ratio of 1.5~3.0 and during shear compression failure, the major conclusions were as follows: the shear capacity of pipe pile showed a fluctuating decline during the decline process; the pipe pile’s maximum shear capacity was not synchronized with the failure of the pipe pile; when the maximum shear capacity is reached, the tensile cracks had occurred in the concrete upper neutral axis of the pipe pile. With the progress of displacement loading, when the tensile cracks were basically penetrated, the pile concrete had destroyed, the stirrup stress had increased, and the stirrup had yielded but the stirrup did not break. Finally, a formula for the shear capacity of PHC pipe pile was proposed on the basis of the current formula and the 45° fracture surface assumption.
2022, 52(6): 25-30,99.
doi: 10.13204/j.gyjzG21111209
Abstract:
PHC pipe pile has been widely used in foundation engineering due to its high seismic performance and large bearing capacity of single pile. The uplift resistance of pile-pile joints is one of the key issues to be considered when connecting piles. ABAQUS finite element software was used to establish the calculation model of the hooped joint of PHC pipe pile, and the mechanical mechanism of the joint was studied. The effects of the edge width, radial thickness and plate thickness on the stress distribution and the tensile capacity of hooped pile were investigated. The calculation results showed that the size of the U-shaped hoop had a certain influence on the failure mode of the joint under tension. When the load reaches the design load, the model’s maximum stress of the hoop, plate and prestressed reinforcement decreased with the increase of hoop size. With the increase of plate thickness, the maximum stress of hooped clamp and end plate decreased, while the maximum stress of prestressed tendon increased.
PHC pipe pile has been widely used in foundation engineering due to its high seismic performance and large bearing capacity of single pile. The uplift resistance of pile-pile joints is one of the key issues to be considered when connecting piles. ABAQUS finite element software was used to establish the calculation model of the hooped joint of PHC pipe pile, and the mechanical mechanism of the joint was studied. The effects of the edge width, radial thickness and plate thickness on the stress distribution and the tensile capacity of hooped pile were investigated. The calculation results showed that the size of the U-shaped hoop had a certain influence on the failure mode of the joint under tension. When the load reaches the design load, the model’s maximum stress of the hoop, plate and prestressed reinforcement decreased with the increase of hoop size. With the increase of plate thickness, the maximum stress of hooped clamp and end plate decreased, while the maximum stress of prestressed tendon increased.
2022, 52(6): 31-39.
doi: 10.13204/j.gyjzG20112505
Abstract:
With urban development and economic transformation, some traditional mining industries have left a lot of "scars" due to early mining. The transformation of the mining industry into a mine park is currently the main form of domestic mining wasteland management. Based on the status quo of China’s mining wasteland and the concept of urban renewal and ecological restorarion, the principles and methods for reforming mining wasteland under the concept of urban renewal and ecological restorarion were introduced. Combined with the planning example of Xiangtan Manganese Mine National Mine Park, the transformation methods of manganese mining wasteland from the perspectives of urban renewal and ecological restorarion was discussed, in order to provide some references for the restoration and transformation of mining wasteland.
With urban development and economic transformation, some traditional mining industries have left a lot of "scars" due to early mining. The transformation of the mining industry into a mine park is currently the main form of domestic mining wasteland management. Based on the status quo of China’s mining wasteland and the concept of urban renewal and ecological restorarion, the principles and methods for reforming mining wasteland under the concept of urban renewal and ecological restorarion were introduced. Combined with the planning example of Xiangtan Manganese Mine National Mine Park, the transformation methods of manganese mining wasteland from the perspectives of urban renewal and ecological restorarion was discussed, in order to provide some references for the restoration and transformation of mining wasteland.
2022, 52(6): 40-46.
doi: 10.13204/j.gyjzG22010608
Abstract:
Using bibliometric method and visual knowledge mapping, the relevant literature and research hotspots of "Shanshui-city" and urban landscape painting were sorted ont, and the analysis results showed that: 1) "Shanshui-city" and urban landscape painting were intrinsically related; 2) the existing researches seldom explored the construction of "Shanshui-city" from the aesthetic characteristics of urban landscape painting; 3) the current construction of "Shanshui-city" lacked deep research on the spiritual and cultural connotation of the city. Based on this, the aesthetic characteristics of urban landscape painting, such as brush and ink language, light and shadow color and ink, and composition form, were used to explore its inspiration for "Shanshui-city" in three aspects: urban humanistic spirit, landscape planning, and spatial layout.
Using bibliometric method and visual knowledge mapping, the relevant literature and research hotspots of "Shanshui-city" and urban landscape painting were sorted ont, and the analysis results showed that: 1) "Shanshui-city" and urban landscape painting were intrinsically related; 2) the existing researches seldom explored the construction of "Shanshui-city" from the aesthetic characteristics of urban landscape painting; 3) the current construction of "Shanshui-city" lacked deep research on the spiritual and cultural connotation of the city. Based on this, the aesthetic characteristics of urban landscape painting, such as brush and ink language, light and shadow color and ink, and composition form, were used to explore its inspiration for "Shanshui-city" in three aspects: urban humanistic spirit, landscape planning, and spatial layout.
2022, 52(6): 47-54.
doi: 10.13204/j.gyjzG20120208
Abstract:
From the perspective of regionalism and contextualism, the paper discussed the concept and connotation of "environmental view" and analyzed the practical logic of the concept of "regional context" in the renewal of historical district style and the reconstruction of spatial order. Taking the renewal design of South&North Street, a famous national historical and cultural city in Xunxian County, Henan Province as an example, discussed the implementation strategy of the "environmental view" of "regional context" in the renewal and construction of blocks from the two aspects of "overall style control" and "architectural detail renewal" of historical districts, aimed at providing references for relevant domestic renewal and transformation projects.
From the perspective of regionalism and contextualism, the paper discussed the concept and connotation of "environmental view" and analyzed the practical logic of the concept of "regional context" in the renewal of historical district style and the reconstruction of spatial order. Taking the renewal design of South&North Street, a famous national historical and cultural city in Xunxian County, Henan Province as an example, discussed the implementation strategy of the "environmental view" of "regional context" in the renewal and construction of blocks from the two aspects of "overall style control" and "architectural detail renewal" of historical districts, aimed at providing references for relevant domestic renewal and transformation projects.
2022, 52(6): 55-60.
doi: 10.13204/j.gyjzG21083005
Abstract:
Nature aesthetics are aesthetic views taking humans as cognitive subjects and nature as the object of knowledge. The relations of humans, architecture and nature were discussed through the reconstruction of nature aesthetics in architecture, and a non-confrontational architectural concept with nature was proposed. Objective substances, natural laws and theories, and implicit architecture imagery were the three ways of translating nature aesthetics into the language of architectural forms, which were expressed in the concrete transformation of images, the logical isomorph of principles and the comprehensive creation of artistic conception. The harmonious symbiosis among those three provided a diversified and open form language for modern urban architectural design.
Nature aesthetics are aesthetic views taking humans as cognitive subjects and nature as the object of knowledge. The relations of humans, architecture and nature were discussed through the reconstruction of nature aesthetics in architecture, and a non-confrontational architectural concept with nature was proposed. Objective substances, natural laws and theories, and implicit architecture imagery were the three ways of translating nature aesthetics into the language of architectural forms, which were expressed in the concrete transformation of images, the logical isomorph of principles and the comprehensive creation of artistic conception. The harmonious symbiosis among those three provided a diversified and open form language for modern urban architectural design.
2022, 52(6): 61-70.
doi: 10.13204/j.gyjzG21060810
Abstract:
Building envelope is an important part of the structure, to examine the influence of prefabricated building envelope on the seismic performance of frame structure, two trusses of two-story full-scale RC frames with prefabricated light steel keel out-hung wall panels and concrete out-hung wall panels, respectively, were designed and manufactured to carry out the quasi-static test, and the influence of new type exterior wall panels and their connecting joints on bearing capacity, stiffness degradation and energy dissipation of structures were studied. The test results showed that the RC frame structure with prefabricated exterior wall had good aseismic performance, the building envelope with large stiffness could provide additional stiffness to the main structure whose partial structural elements lost the bearing capacity under the large earthquake, so that the structure had better anti-collapse redundancy and could meet the deformation requirement of 1/50 inter-story drift. There was no obvious damage at the new connection joints of the prefabricated exterior wall, which indicated that the design of the joints was more reasonable and could realize the purpose of no slip under frequently occurred earthquake, no stress under moderate earthquake, and provide reliable connection for the building envelope under rarely occurred earthquake.
Building envelope is an important part of the structure, to examine the influence of prefabricated building envelope on the seismic performance of frame structure, two trusses of two-story full-scale RC frames with prefabricated light steel keel out-hung wall panels and concrete out-hung wall panels, respectively, were designed and manufactured to carry out the quasi-static test, and the influence of new type exterior wall panels and their connecting joints on bearing capacity, stiffness degradation and energy dissipation of structures were studied. The test results showed that the RC frame structure with prefabricated exterior wall had good aseismic performance, the building envelope with large stiffness could provide additional stiffness to the main structure whose partial structural elements lost the bearing capacity under the large earthquake, so that the structure had better anti-collapse redundancy and could meet the deformation requirement of 1/50 inter-story drift. There was no obvious damage at the new connection joints of the prefabricated exterior wall, which indicated that the design of the joints was more reasonable and could realize the purpose of no slip under frequently occurred earthquake, no stress under moderate earthquake, and provide reliable connection for the building envelope under rarely occurred earthquake.
2022, 52(6): 71-78,107.
doi: 10.13204/j.gyjzG19021501
Abstract:
It has been shown that as concrete strength increases, the size effect of ultimate flexural capacity becomes more pronounced in columns. However, the size effect of flexural capacity requires further confirmation for high-strength concrete columns. For this purpose, the high-strength concrete columns with a theoretical shear-span ratio of 4 were subjected to axial and monotonic loading in this study. The shear-span ratio, axial load ratio, and volume ratio of stirrup were consistent. The geometric similarity ratio of components was 3∶5∶7. The experimental results indicated that the failure mode of columns was flexural failure, and the splitting effect of concrete cover for large size columns might be a part reason of size effect. Meanwhile, the relative nominal flexural strength, nominal angle of rotation, P-Δ effect, and safety factors and local safety factors for flexural capacity decreased as section size increased, suggesting that size effect existed. Moreover, the size effect of relative nominal flexural strength and safety factors of flexural capacity was stronger for high-strength columns than for conventional concrete columns. In addition, based on the test results and Bažant’s Type 2 model, the calculation method of flexural capacity was modified to provide a constant factor of safety regardless of column size, indicating that the fluexural capacity was safer for large size columns.
It has been shown that as concrete strength increases, the size effect of ultimate flexural capacity becomes more pronounced in columns. However, the size effect of flexural capacity requires further confirmation for high-strength concrete columns. For this purpose, the high-strength concrete columns with a theoretical shear-span ratio of 4 were subjected to axial and monotonic loading in this study. The shear-span ratio, axial load ratio, and volume ratio of stirrup were consistent. The geometric similarity ratio of components was 3∶5∶7. The experimental results indicated that the failure mode of columns was flexural failure, and the splitting effect of concrete cover for large size columns might be a part reason of size effect. Meanwhile, the relative nominal flexural strength, nominal angle of rotation, P-Δ effect, and safety factors and local safety factors for flexural capacity decreased as section size increased, suggesting that size effect existed. Moreover, the size effect of relative nominal flexural strength and safety factors of flexural capacity was stronger for high-strength columns than for conventional concrete columns. In addition, based on the test results and Bažant’s Type 2 model, the calculation method of flexural capacity was modified to provide a constant factor of safety regardless of column size, indicating that the fluexural capacity was safer for large size columns.
2022, 52(6): 79-86.
doi: 10.13204/j.gyjzG21090907
Abstract:
Experimental research was carried out on the precast concrete shear wall connected by grouted bellows and confined with overlapped closed stirrups and its emulative seismic performance was verified. Moreover, the parameter analysis of mechanical properties was conducted by using MATLAB to discuss the influence of key parameters on the seismic properties, such as axial compression ratio, shear span-ratio, boundary element length, vertical reinforcement ratio, stirrup characteristic values of boundary elements, and concrete strength. As axial load ratio increased, the deformation capacity decreased, and the bearing capacity was first rose and then decreased; with the increase of shear-span ratio, the bearing capacity decreased and the deformation capability was improved; as boundary element lengths increased, the bearing capacity of the component increased and the deformation capability rose and then decreased; with the increase of vertical reinforcement ratio, the bearing capacity increased linearly, and the deformation capability changed less; with the increase of stirrup characteristic values of boundary elements, the deformation capability was obviously improved, and the bearing capacity was less variable; with the increase of concrete strength, the bearing capacity and deformation capacity were improved to some extent. According to the test and MATLAB results, it was suggested that for the design of precast concrete shear walls connected by grouted bellows, the axial compression ratio should be controlled below 0.4; the shear-span ratio should not be less than 2.5; the boundary element length could be set according to the current cast-in-place concrete specification; when the design allows and the construction is feasible, it showed that the edge member coupling characteristic value should be improved; the concrete strength should meet the design requirements.
Experimental research was carried out on the precast concrete shear wall connected by grouted bellows and confined with overlapped closed stirrups and its emulative seismic performance was verified. Moreover, the parameter analysis of mechanical properties was conducted by using MATLAB to discuss the influence of key parameters on the seismic properties, such as axial compression ratio, shear span-ratio, boundary element length, vertical reinforcement ratio, stirrup characteristic values of boundary elements, and concrete strength. As axial load ratio increased, the deformation capacity decreased, and the bearing capacity was first rose and then decreased; with the increase of shear-span ratio, the bearing capacity decreased and the deformation capability was improved; as boundary element lengths increased, the bearing capacity of the component increased and the deformation capability rose and then decreased; with the increase of vertical reinforcement ratio, the bearing capacity increased linearly, and the deformation capability changed less; with the increase of stirrup characteristic values of boundary elements, the deformation capability was obviously improved, and the bearing capacity was less variable; with the increase of concrete strength, the bearing capacity and deformation capacity were improved to some extent. According to the test and MATLAB results, it was suggested that for the design of precast concrete shear walls connected by grouted bellows, the axial compression ratio should be controlled below 0.4; the shear-span ratio should not be less than 2.5; the boundary element length could be set according to the current cast-in-place concrete specification; when the design allows and the construction is feasible, it showed that the edge member coupling characteristic value should be improved; the concrete strength should meet the design requirements.
2022, 52(6): 87-92.
doi: 10.13204/j.gyjzG19100102
Abstract:
Soil-structure interaction (SSI) has obvious influence on structural seismic response. To study the effect of SSI on nuclear, taking the third-generation reactor AP1000 containment structure as the object, a 1/40 scale model was fabricated for the shaking table test, and a flexible soil container was applied to simulate the unlimited site and eliminate the boundary effect as far as possible. The results indicate that: 1) for the non-isolated NPP structure, considering SSI will reduce the natural frequency of the model. Meanwhile, the effect makes the high-frequency component of the acceleration decrease, and the peak frequency moves from high frequency to low frequency. Therefore, the soil shows a certain isolation effect and reduces the acceleration of the containment structure; 2) for isolated NPP structure, considering SSI has almost no effect on the natural frequency, but SSI effect will weaken the isolation effect and increase the acceleration value at some frequencies.
Soil-structure interaction (SSI) has obvious influence on structural seismic response. To study the effect of SSI on nuclear, taking the third-generation reactor AP1000 containment structure as the object, a 1/40 scale model was fabricated for the shaking table test, and a flexible soil container was applied to simulate the unlimited site and eliminate the boundary effect as far as possible. The results indicate that: 1) for the non-isolated NPP structure, considering SSI will reduce the natural frequency of the model. Meanwhile, the effect makes the high-frequency component of the acceleration decrease, and the peak frequency moves from high frequency to low frequency. Therefore, the soil shows a certain isolation effect and reduces the acceleration of the containment structure; 2) for isolated NPP structure, considering SSI has almost no effect on the natural frequency, but SSI effect will weaken the isolation effect and increase the acceleration value at some frequencies.
2022, 52(6): 93-99.
doi: 10.13204/j.gyjzG20121408
Abstract:
In order to study the thermal-mechanical coupling effect of hot water storage tank under the action of temperature field and earthquake, the geometric model of hot water storage tank was established by using the additional mass method, and the coupling effect between temperature and earthquake was analyzed by using finite element software ABAQUS. The seismic response characteristics of empty tank and hot water full-loaded tank were investigated. The results showed that the angle of the maximum displacement in the X-Y plane and the height of the tank wall of the hot water storage tank were significantly different between the two conditions of empty tank and full-loaded tank; in addition, the position of the maximum displacement would be different when the thermal-mechanical coupling was considered, and the stress of the tank wall when the thermal mechanical coupling was considered was slightly smaller than that when the thermal-mechanical coupling was not considered.Therefore, the influence of two states of empty tank and full-loaded tank as well as the thermal coupling effect should be considered when the seismic design of the hot water storage tank was carried out.
In order to study the thermal-mechanical coupling effect of hot water storage tank under the action of temperature field and earthquake, the geometric model of hot water storage tank was established by using the additional mass method, and the coupling effect between temperature and earthquake was analyzed by using finite element software ABAQUS. The seismic response characteristics of empty tank and hot water full-loaded tank were investigated. The results showed that the angle of the maximum displacement in the X-Y plane and the height of the tank wall of the hot water storage tank were significantly different between the two conditions of empty tank and full-loaded tank; in addition, the position of the maximum displacement would be different when the thermal-mechanical coupling was considered, and the stress of the tank wall when the thermal mechanical coupling was considered was slightly smaller than that when the thermal-mechanical coupling was not considered.Therefore, the influence of two states of empty tank and full-loaded tank as well as the thermal coupling effect should be considered when the seismic design of the hot water storage tank was carried out.
2022, 52(6): 100-107.
doi: 10.13204/j.gyjzG21031611
Abstract:
In order to explore the mechanical properties of T-shaped wall with stainless steel core plate under biaxial bending and compression, first of all, 12 groups of ABAQUS finite element models were designed for comparative analysis, the mechanical characteristics and failure mechanism in earch stage were studied, and then the influence of 6 variables on the flexural bearing capacity of T-shaped wall was analyzed by changing parameters such as the thickness of the panel, the aspect ratio of wall limb, the thickness of side plate, the thickness of the core tube, axial compression ratio and eccentric angle, it was concluded that the panel thickness and axial compression were the most significant factors. Finally, the obtained Mx and My were normalized to fit the interaction equations of Mx and My under different axial compression ratios.
In order to explore the mechanical properties of T-shaped wall with stainless steel core plate under biaxial bending and compression, first of all, 12 groups of ABAQUS finite element models were designed for comparative analysis, the mechanical characteristics and failure mechanism in earch stage were studied, and then the influence of 6 variables on the flexural bearing capacity of T-shaped wall was analyzed by changing parameters such as the thickness of the panel, the aspect ratio of wall limb, the thickness of side plate, the thickness of the core tube, axial compression ratio and eccentric angle, it was concluded that the panel thickness and axial compression were the most significant factors. Finally, the obtained Mx and My were normalized to fit the interaction equations of Mx and My under different axial compression ratios.
2022, 52(6): 108-113.
doi: 10.13204/j.gyjzG20112805
Abstract:
In order to solve the problem of interface void defect of composite steel plate shear wall, based on the hydration heat of concrete itself, infrared thermal imaging method was used to detect the interface void defect of composite steel plate shear wall by using the temperature difference between steel plate and concrete itself. The results showed that: under the condition of concrete hydration heat, the defect location and size of the interface void of composite steel plate shear wall could be effectively identified. When the temperature difference during molding was 15 ℃, the void defect with an area of more than 1 cm2 could be identified. When the temperature difference during molding was 10 ℃ or 5 ℃, the void defect with an area of more than 4 cm2 could be identified. The method could be more convenient and fast for engineering detection, and could be convenient for real-time tracking detection when pouring concrete. It showed higher practical application value.
In order to solve the problem of interface void defect of composite steel plate shear wall, based on the hydration heat of concrete itself, infrared thermal imaging method was used to detect the interface void defect of composite steel plate shear wall by using the temperature difference between steel plate and concrete itself. The results showed that: under the condition of concrete hydration heat, the defect location and size of the interface void of composite steel plate shear wall could be effectively identified. When the temperature difference during molding was 15 ℃, the void defect with an area of more than 1 cm2 could be identified. When the temperature difference during molding was 10 ℃ or 5 ℃, the void defect with an area of more than 4 cm2 could be identified. The method could be more convenient and fast for engineering detection, and could be convenient for real-time tracking detection when pouring concrete. It showed higher practical application value.
2022, 52(6): 114-119.
doi: 10.13204/j.gyjzG20110324
Abstract:
In order to solve the problem that the traditional steel tower is prone to collapse due to local buckling under axial compression, considering the principle of steel-concrete composite structures, a new type of steel-concrete composite shell hybrid tower for wind power tower structure was proposed. In order to study the buckling bearing capacity of steel plate in steel-concrete composite shell hybrid tower, three specimens were designed considering the key parameters such as the curvature (the reciprocal of radius) and the spacing-to-thickness ratio (the ratio of vertical stud spacing and surface steel plate thickness). The inner and outer steel plates were connected to the concrete by the studs, and the concrete did not directly bear the vertical load and only provided brace to the steel plates. Polytetrafluoroethylene membrane was laid between the steel plates and concrete to eliminate the friction and adhesion between the steel plates and sandwich concrete. The specimens were tested under axial compression, the failure modes and load-displacement curves of the specimens were obtained. The test results showed that: 1)local buckling failure between studs occurred in all specimens. 2)Compared with the specimen with curvature of 0.001 and the flat steel plate specimen, setting curvature structure could greatly improve the buckling bearing capacity. 3)Reducing the spacing-to-thickness ratio could also improve the buckling bearing capacity of the specimen.
In order to solve the problem that the traditional steel tower is prone to collapse due to local buckling under axial compression, considering the principle of steel-concrete composite structures, a new type of steel-concrete composite shell hybrid tower for wind power tower structure was proposed. In order to study the buckling bearing capacity of steel plate in steel-concrete composite shell hybrid tower, three specimens were designed considering the key parameters such as the curvature (the reciprocal of radius) and the spacing-to-thickness ratio (the ratio of vertical stud spacing and surface steel plate thickness). The inner and outer steel plates were connected to the concrete by the studs, and the concrete did not directly bear the vertical load and only provided brace to the steel plates. Polytetrafluoroethylene membrane was laid between the steel plates and concrete to eliminate the friction and adhesion between the steel plates and sandwich concrete. The specimens were tested under axial compression, the failure modes and load-displacement curves of the specimens were obtained. The test results showed that: 1)local buckling failure between studs occurred in all specimens. 2)Compared with the specimen with curvature of 0.001 and the flat steel plate specimen, setting curvature structure could greatly improve the buckling bearing capacity. 3)Reducing the spacing-to-thickness ratio could also improve the buckling bearing capacity of the specimen.
2022, 52(6): 120-126.
doi: 10.13204/j.gyjzG21060710
Abstract:
The characteristics of wind pressure distribution of an ellipsoidal air-supported structure considering fluid-structure interaction and fluctuating wind effect were studied. Firstly, the time-history data of fluctuating wind speed obtained in MATLAB by using linear filter method was imported into Fluent. Secondly, the wind pressure coefficients of the structures under different wind direction angles, heights and internal pressures after the wind-induced response stabilized were obtained by the partitioned weakly coupled algorithm on Workbench 17.0 platform. The results showed that the extreme values of the negative pressure coefficient increased obviously when the fluid-structure interaction was considered. The three variables had influence on the distribution, magnitude and changing rate of wind pressure. The wind pressure extreme values of the structure could be kept at a low level at 400 Pa.
The characteristics of wind pressure distribution of an ellipsoidal air-supported structure considering fluid-structure interaction and fluctuating wind effect were studied. Firstly, the time-history data of fluctuating wind speed obtained in MATLAB by using linear filter method was imported into Fluent. Secondly, the wind pressure coefficients of the structures under different wind direction angles, heights and internal pressures after the wind-induced response stabilized were obtained by the partitioned weakly coupled algorithm on Workbench 17.0 platform. The results showed that the extreme values of the negative pressure coefficient increased obviously when the fluid-structure interaction was considered. The three variables had influence on the distribution, magnitude and changing rate of wind pressure. The wind pressure extreme values of the structure could be kept at a low level at 400 Pa.
2022, 52(6): 127-132.
doi: 10.13204/j.gyjzG21060812
Abstract:
Aiming at the problems for instability and durability of halical steel pipe piles in deep marine soft soil, a helical steel grouting pipe pile was proposed. A two-stage test was designed. In the first stage, different tested piles were used for pile-forming tests to verify the feasibility of pile-forming processes. The influence of sleeves and grouting methods on pile-forming quality was analyzed, and the pile type design and the pile-forming process were optimized. In the second stage, the influence of sleaves and grouting methods on the ultimate bearing capacity of helical steel grounting pipe piles was studied by the compressive bearing capacity tests of improved single piles. The curves of loads and settlement displacement at pile tops and the typical failure characteristics of piles were obtained, and the variation characteristics of pile-soil interaction for helical steel grounting pipe piles were analyzed. Finally, the experimental results were compared with the calculation results by Chance@ Civil Construction: Technical Design Manual compiled by Hubbell Power Systems, Inc. and Micropile Design and Construction Reference Manual issued by Federal Highway Administration of America. The test results showed that the helical paddles expanded the diameters of cemented grouting slurry and sleeves could effectively enhance the stability of piles. The grouting effect was significant and the full-section rotary jet grouting method could significantly increase the bearing capacity of piles under vertical compression.
Aiming at the problems for instability and durability of halical steel pipe piles in deep marine soft soil, a helical steel grouting pipe pile was proposed. A two-stage test was designed. In the first stage, different tested piles were used for pile-forming tests to verify the feasibility of pile-forming processes. The influence of sleeves and grouting methods on pile-forming quality was analyzed, and the pile type design and the pile-forming process were optimized. In the second stage, the influence of sleaves and grouting methods on the ultimate bearing capacity of helical steel grounting pipe piles was studied by the compressive bearing capacity tests of improved single piles. The curves of loads and settlement displacement at pile tops and the typical failure characteristics of piles were obtained, and the variation characteristics of pile-soil interaction for helical steel grounting pipe piles were analyzed. Finally, the experimental results were compared with the calculation results by Chance@ Civil Construction: Technical Design Manual compiled by Hubbell Power Systems, Inc. and Micropile Design and Construction Reference Manual issued by Federal Highway Administration of America. The test results showed that the helical paddles expanded the diameters of cemented grouting slurry and sleeves could effectively enhance the stability of piles. The grouting effect was significant and the full-section rotary jet grouting method could significantly increase the bearing capacity of piles under vertical compression.
2022, 52(6): 133-139.
doi: 10.13204/j.gyjzG21052304
Abstract:
To further understand the mechanical properties of anisotropic structural surfaces, the specimens with gypsum-mortar structural surfaces in four joint roughness coefficients were made based on the standard Barton’s section lines of structural surfaces. Particularly, gypsum and mortar had the similar uniaxial compressive strength. Two kinds of curves between shear stress and displacement were obtained by indoor direct shear tests under three kinds of normal stress. Consequently, the change laws for peak shear strength of specimens with gypsum-mortar structural surfaces with the increase of joint roughness coefficients and normal stress were analyzed. Based on the numerical simulating results, the shear failure modes of anisotropic structural surfaces with similar strength were summarized. The curves between shear stress and displacement of anisotropic structural surfacess with lower roughness coefficients developed to the residual deformation stage after reaching peak values, while the curves of specimens with higher roughness coefficients evolved to the obvious softening stage. The growth rates of shear stress was positively correlated with roughness coefficients and normal stress. Under different normal stress, climbing failure, climbing-gnawing failure and gnawing failure occured successively to the anisotropic structural surfaces with similar strength as the roughness coefficient increased.
To further understand the mechanical properties of anisotropic structural surfaces, the specimens with gypsum-mortar structural surfaces in four joint roughness coefficients were made based on the standard Barton’s section lines of structural surfaces. Particularly, gypsum and mortar had the similar uniaxial compressive strength. Two kinds of curves between shear stress and displacement were obtained by indoor direct shear tests under three kinds of normal stress. Consequently, the change laws for peak shear strength of specimens with gypsum-mortar structural surfaces with the increase of joint roughness coefficients and normal stress were analyzed. Based on the numerical simulating results, the shear failure modes of anisotropic structural surfaces with similar strength were summarized. The curves between shear stress and displacement of anisotropic structural surfacess with lower roughness coefficients developed to the residual deformation stage after reaching peak values, while the curves of specimens with higher roughness coefficients evolved to the obvious softening stage. The growth rates of shear stress was positively correlated with roughness coefficients and normal stress. Under different normal stress, climbing failure, climbing-gnawing failure and gnawing failure occured successively to the anisotropic structural surfaces with similar strength as the roughness coefficient increased.
2022, 52(6): 140-149.
doi: 10.13204/j.gyjzG21050609
Abstract:
To explore the lateral bearing characteristics of two-tier slopes supported with ridge walls of geotextile bags, the model tests of two-tier slopes under non-uniform lateral loading were conducted in the conditions of four kinds of ridge walls supported with geotextile bags, including no support, inclined type supporting, L-shaped supporting and L-shaped supporting with notched sills, and three kinds of slope rates involving 1∶0.3, 1∶0.5 and 1∶0.75, respectively. The displacement of the slopes and earth pressure were analyzed under lateral loading. The results showed that the horizontal displacement of the second tier slopes was greater than those of the first tier slopes. Simultaneously, the earth pressure behind those walls increased with the wall height. And the earth pressure at the connections between the first and second tier slopes was the largest. Taking the non-supporting slope as reference, the horizontal displacement at the tops of the second tier slopes with inclined type, L-shaped and L-shaped supporting with notched sills decreased by 8.6%, 13.2% and 16.5%, respectively, and the earth pressure at the toes of slopes with inclined type supporting increased by 19.3%, and the earth pressure at the toes of the second tier slopes with L-shaped supporting increased by 32.6%. The earth pressure at the toes of the second tier slopes with L-shaped supporting with notched sills increased by 42.2%. Taking the slope at a slope rate of 1∶0.3 as reference, the heave height on crests of the second tier slopes at a slope rate of 1∶0.5 increased by 18.2%, the horizontal displacement of slope tops decreased by 7.1%, and the earth pressure at toes of slope increased by 7.8%. Simultaneously, the heave height on crests of the second tier slopes at a slope rate of 1∶0.75 increased by 34.8%, the horizontal displacement of slope tops decreased by 10.9%, the earth pressure at the toes of slopes increased by 23.1%. It showed that the failure of the second tier slopes preceded that of the first tier slopes. The lateral deformation resistance of the second tier slopes was maximum in support of geotextile-bag ridge walls with the L-shaped supporting with notch sills. In addition, the smaller the slope ratio was, the greater the capacity of the slope to resist lateral deformation was, the greater the capacity of the flexible ridge wall to resist lateral earth pressure was, and the larger the bearing capacity was.
To explore the lateral bearing characteristics of two-tier slopes supported with ridge walls of geotextile bags, the model tests of two-tier slopes under non-uniform lateral loading were conducted in the conditions of four kinds of ridge walls supported with geotextile bags, including no support, inclined type supporting, L-shaped supporting and L-shaped supporting with notched sills, and three kinds of slope rates involving 1∶0.3, 1∶0.5 and 1∶0.75, respectively. The displacement of the slopes and earth pressure were analyzed under lateral loading. The results showed that the horizontal displacement of the second tier slopes was greater than those of the first tier slopes. Simultaneously, the earth pressure behind those walls increased with the wall height. And the earth pressure at the connections between the first and second tier slopes was the largest. Taking the non-supporting slope as reference, the horizontal displacement at the tops of the second tier slopes with inclined type, L-shaped and L-shaped supporting with notched sills decreased by 8.6%, 13.2% and 16.5%, respectively, and the earth pressure at the toes of slopes with inclined type supporting increased by 19.3%, and the earth pressure at the toes of the second tier slopes with L-shaped supporting increased by 32.6%. The earth pressure at the toes of the second tier slopes with L-shaped supporting with notched sills increased by 42.2%. Taking the slope at a slope rate of 1∶0.3 as reference, the heave height on crests of the second tier slopes at a slope rate of 1∶0.5 increased by 18.2%, the horizontal displacement of slope tops decreased by 7.1%, and the earth pressure at toes of slope increased by 7.8%. Simultaneously, the heave height on crests of the second tier slopes at a slope rate of 1∶0.75 increased by 34.8%, the horizontal displacement of slope tops decreased by 10.9%, the earth pressure at the toes of slopes increased by 23.1%. It showed that the failure of the second tier slopes preceded that of the first tier slopes. The lateral deformation resistance of the second tier slopes was maximum in support of geotextile-bag ridge walls with the L-shaped supporting with notch sills. In addition, the smaller the slope ratio was, the greater the capacity of the slope to resist lateral deformation was, the greater the capacity of the flexible ridge wall to resist lateral earth pressure was, and the larger the bearing capacity was.
2022, 52(6): 150-155,149.
doi: 10.13204/j.gyjzG21052007
Abstract:
Pile foundations are a common foundation form for large dynamic machines, the essential and difficult problem in design is to determine the response characteristics of foundations under dynamic loads. The simulation method of finite solid elements for dynamic machine foundations was constructed based on the interaction of foundation, pile foundations and superstructures, and the modal and steady-state simulations were performed. The simulation results were verified by test results of foundations with double piles on site. Then, the steady state analysis for a foundation of axial flow compressors was performed, and the vibration displacement was calculated. Based on the model, the modal damping ratio of the structure, diameter and length of the foundation piles were taken as variables to analyze the laws for the vibration displacement of the axial flow compressor foundation. And corresponding optimization measures were proposed, which could provide reference to the optimization of similar projects.
Pile foundations are a common foundation form for large dynamic machines, the essential and difficult problem in design is to determine the response characteristics of foundations under dynamic loads. The simulation method of finite solid elements for dynamic machine foundations was constructed based on the interaction of foundation, pile foundations and superstructures, and the modal and steady-state simulations were performed. The simulation results were verified by test results of foundations with double piles on site. Then, the steady state analysis for a foundation of axial flow compressors was performed, and the vibration displacement was calculated. Based on the model, the modal damping ratio of the structure, diameter and length of the foundation piles were taken as variables to analyze the laws for the vibration displacement of the axial flow compressor foundation. And corresponding optimization measures were proposed, which could provide reference to the optimization of similar projects.
2022, 52(6): 156-161,70.
doi: 10.13204/j.gyjzG21061905
Abstract:
In-situ test piling is an effective method to reasonably determine the construction technology and the dosage of curing agent, and to evaluate the effect of piling formation. In order to explore the pile-forming effect and applicability of the new drilling bits and the new curing agent for strengthening marine silt, relying on a municipal road project in Doumen District of Zhuhai City, aiming at the properties of marine silt soft soil, both the unconfined compressive strength test (UCS) and direct shear strength test (DST) were conducted to explore the effects of the pile-forming effect with different drill bits and different curing agent dosages.The results showed that the improved drilling bit adopted the construction technology of twice mix for two spraying was more effective, which could save half the construction period. The pile integrity of new curing agent was better than that of pure cement curing agent using the same bit. It was found that the unconfined compressive strength and direct shear strength reduced by RQD value were more suitable for engineering construction. Besides, direct shear strength could take 40% of the unconfined compressive strength.
In-situ test piling is an effective method to reasonably determine the construction technology and the dosage of curing agent, and to evaluate the effect of piling formation. In order to explore the pile-forming effect and applicability of the new drilling bits and the new curing agent for strengthening marine silt, relying on a municipal road project in Doumen District of Zhuhai City, aiming at the properties of marine silt soft soil, both the unconfined compressive strength test (UCS) and direct shear strength test (DST) were conducted to explore the effects of the pile-forming effect with different drill bits and different curing agent dosages.The results showed that the improved drilling bit adopted the construction technology of twice mix for two spraying was more effective, which could save half the construction period. The pile integrity of new curing agent was better than that of pure cement curing agent using the same bit. It was found that the unconfined compressive strength and direct shear strength reduced by RQD value were more suitable for engineering construction. Besides, direct shear strength could take 40% of the unconfined compressive strength.
2022, 52(6): 162-166,113.
doi: 10.13204/j.gyjzG21102005
Abstract:
The durability of concrete can be improved by using functional gradient structure. Functionally gradient concrete (FGC) was prepared with NaOH activated slag (NAS) and Portland cement (PC). Then the carbonation resistance and chloride ion permeability resistance of FGC were studied. At the same time, NAS mortar (or NAS paste) and PC mortar (or PC paste) were analyzed by mercury injection method, thermal analysis and X-ray diffraction(XRD). The results showed that NAS had excellent resistance to chloride ion penetration but poor resistance to carbonation, and PC had good resistance to carbonation but poor resistance to chloride ion penetration. The PC mortar layer on the surface of NAS concrete could significantly improve the carbonation resistance of FGC, and the NAS mortar layer on the surface of PC concrete could significantly improve the chloride ion penetration resistance of FGC.
The durability of concrete can be improved by using functional gradient structure. Functionally gradient concrete (FGC) was prepared with NaOH activated slag (NAS) and Portland cement (PC). Then the carbonation resistance and chloride ion permeability resistance of FGC were studied. At the same time, NAS mortar (or NAS paste) and PC mortar (or PC paste) were analyzed by mercury injection method, thermal analysis and X-ray diffraction(XRD). The results showed that NAS had excellent resistance to chloride ion penetration but poor resistance to carbonation, and PC had good resistance to carbonation but poor resistance to chloride ion penetration. The PC mortar layer on the surface of NAS concrete could significantly improve the carbonation resistance of FGC, and the NAS mortar layer on the surface of PC concrete could significantly improve the chloride ion penetration resistance of FGC.
2022, 52(6): 167-173,139.
doi: 10.13204/j.gyjzG21110802
Abstract:
In order to study the degradation process of durability of recycled aggregate concrete (RAC) under sulfate dry-wet cycle and freeze-thaw cycle, the replacement rate of recycled aggregate (0, 30%, 50%, 70%), fly ash content (10%, 20%, 30%), silica fume content (5%, 8%, 12%), and single and mixed methods were selected as influencing factors to study the influence law of RAC durability. The mass loss rate and relative dynamic elastic modulus were used to describe the mechanism of the above influencing factors on the degradation of RAC durability. Based on the relative dynamic elastic modulus of RAC in freeze-thaw cycle test, the reliability change of RAC was analyzed by using a single Wiener random process to predict the service life of RAC under freeze-thaw environment. The research showed that under the condition of freeze-thaw cycle, compared with the reference parts without recycled aggregate, fly ash and silica fume, the mass loss rate of RAC decreased gradually with the increase of recycled aggregate content. With the increase of fly ash content and silica fume content, the mass loss rate of RAC first decreased and then increased, and the relative dynamic elastic modulus of RAC increased first and then decreased. When the fixed fly ash content was 20% and silica fume content was 8%, the mass loss rate and relative dynamic elastic modulus of RAC decreased gradually with the increase of recycled coarse aggregate content. Under the condition of sulfate dry-wet cycle, the relative dynamic elastic modulus of RAC decreased gradually with the increase of recycled aggregate content. According to the analysis of the model established by the unitary Wiener method, it could be seen that the reliability of the RAC model prepared by replacing natural aggregate with recycled aggregate at 30% substitution rate with 20% fly ash and 8% silica fume had the longest variation time.
In order to study the degradation process of durability of recycled aggregate concrete (RAC) under sulfate dry-wet cycle and freeze-thaw cycle, the replacement rate of recycled aggregate (0, 30%, 50%, 70%), fly ash content (10%, 20%, 30%), silica fume content (5%, 8%, 12%), and single and mixed methods were selected as influencing factors to study the influence law of RAC durability. The mass loss rate and relative dynamic elastic modulus were used to describe the mechanism of the above influencing factors on the degradation of RAC durability. Based on the relative dynamic elastic modulus of RAC in freeze-thaw cycle test, the reliability change of RAC was analyzed by using a single Wiener random process to predict the service life of RAC under freeze-thaw environment. The research showed that under the condition of freeze-thaw cycle, compared with the reference parts without recycled aggregate, fly ash and silica fume, the mass loss rate of RAC decreased gradually with the increase of recycled aggregate content. With the increase of fly ash content and silica fume content, the mass loss rate of RAC first decreased and then increased, and the relative dynamic elastic modulus of RAC increased first and then decreased. When the fixed fly ash content was 20% and silica fume content was 8%, the mass loss rate and relative dynamic elastic modulus of RAC decreased gradually with the increase of recycled coarse aggregate content. Under the condition of sulfate dry-wet cycle, the relative dynamic elastic modulus of RAC decreased gradually with the increase of recycled aggregate content. According to the analysis of the model established by the unitary Wiener method, it could be seen that the reliability of the RAC model prepared by replacing natural aggregate with recycled aggregate at 30% substitution rate with 20% fly ash and 8% silica fume had the longest variation time.
2022, 52(6): 174-182.
doi: 10.13204/j.gyjzG20100301
Abstract:
In order to improve the reinforcement efficiency of fatigue cracks in steel structures, shape memory alloy (SMA) was introduced as a prestressed carrier into the strengthening scheme. First, the mechanical properties and thermodynamic properties of two different shape memory alloys (NiTiNb-SMA and Fe-SMA) were tested to determine the material’s elastic modulus, tensile strength and other mechanical parameters, the heating recovery performance was also investigated, and its optimal size parameters and activation temperature when applied to repair were determined. Then, the finite element method was used to analyze the repair efficiency of the stop-hole method, CFRP patched stop-hole method, NiTiNb-SMA and CFRP patched stop-hole method to strengthen damaged steel plates. Finally, the reliability of the model was verified by static load test. Research results showed that there was a large difference in the constitutive relations between NiTiNb-SMA and Fe-SMA materials, and the mechanical properties of NiTiNb-SMA were higher than those of Fe-SMA.The stress-strain behavior of NiTiNb-SMA material at room temperature and high temperature was quite different, but the elastic modulus and tensile strength were nearly close.At an activation temperature of 170 ℃, the recovery stress of NiTiNb-SMA was 274 MPa, which was about 96 MPa higher than that of Fe-SMA. Compared with the stop-hole method, the finite element results showed that the addition of CFRP, NiTiNb-SMA and CFRP composite patches, and Fe-SMA could reduce the stress at the edge of the hole by 58.8%, 87.0% and 122.4%, respectively. The test results and FEM results were generally in good agreement with the linearity. It is indicated that the shape memory alloy has broad application prospects for strengthening damaged steel structures by introducing prestressing force.
In order to improve the reinforcement efficiency of fatigue cracks in steel structures, shape memory alloy (SMA) was introduced as a prestressed carrier into the strengthening scheme. First, the mechanical properties and thermodynamic properties of two different shape memory alloys (NiTiNb-SMA and Fe-SMA) were tested to determine the material’s elastic modulus, tensile strength and other mechanical parameters, the heating recovery performance was also investigated, and its optimal size parameters and activation temperature when applied to repair were determined. Then, the finite element method was used to analyze the repair efficiency of the stop-hole method, CFRP patched stop-hole method, NiTiNb-SMA and CFRP patched stop-hole method to strengthen damaged steel plates. Finally, the reliability of the model was verified by static load test. Research results showed that there was a large difference in the constitutive relations between NiTiNb-SMA and Fe-SMA materials, and the mechanical properties of NiTiNb-SMA were higher than those of Fe-SMA.The stress-strain behavior of NiTiNb-SMA material at room temperature and high temperature was quite different, but the elastic modulus and tensile strength were nearly close.At an activation temperature of 170 ℃, the recovery stress of NiTiNb-SMA was 274 MPa, which was about 96 MPa higher than that of Fe-SMA. Compared with the stop-hole method, the finite element results showed that the addition of CFRP, NiTiNb-SMA and CFRP composite patches, and Fe-SMA could reduce the stress at the edge of the hole by 58.8%, 87.0% and 122.4%, respectively. The test results and FEM results were generally in good agreement with the linearity. It is indicated that the shape memory alloy has broad application prospects for strengthening damaged steel structures by introducing prestressing force.
2022, 52(6): 183-190.
doi: 10.13204/j.gyjzG21110207
Abstract:
Since the first application case of the lattice-shaped diaphragm wall in Japanese high-speed rail bridges in 1979, it has attracted great attention from domestic and foreign scholars due to its excellent engineering characteristics. Currently, the lattice-shaped diaphragm wall has been used in large-scale bridge foundations at home and abroad and gradually popularized to the enclosure and anti-seepage structure of water conservancy, hydropower and dock foundation excavation engineering. Based on large amount of literature at home and abroad, the application and research status of lattice-shaped diaphragm walls in the bridge foundation was analyzed. The research progress of tests, theoretical calculations and numerical simulations of lattice-shaped diaphragm walls at home and abroad were focused on. Meanwhile, The relevant summary and analysis were implemented to provide certain guidance for the future application and research of lattice-shaped diaphragm walls in the civil engineering.
Since the first application case of the lattice-shaped diaphragm wall in Japanese high-speed rail bridges in 1979, it has attracted great attention from domestic and foreign scholars due to its excellent engineering characteristics. Currently, the lattice-shaped diaphragm wall has been used in large-scale bridge foundations at home and abroad and gradually popularized to the enclosure and anti-seepage structure of water conservancy, hydropower and dock foundation excavation engineering. Based on large amount of literature at home and abroad, the application and research status of lattice-shaped diaphragm walls in the bridge foundation was analyzed. The research progress of tests, theoretical calculations and numerical simulations of lattice-shaped diaphragm walls at home and abroad were focused on. Meanwhile, The relevant summary and analysis were implemented to provide certain guidance for the future application and research of lattice-shaped diaphragm walls in the civil engineering.
2022, 52(6): 191-198.
doi: 10.13204/j.gyjzG21092702
Abstract:
The design and assessment standards of masonry structures in China, the US and Europe were briefly compared. The results showed that the US standard did not reduce the strength, and the European standard defined the adjustment method of partial coefficients. In the seismic assessment, the US and European standards adopted performance-based assessment methods, considering the influence of cognitive level, the representative values of gravity load and the calculation method of seismic bearing capacity were adjusted. The ultimate limit state function of bearing capacity in Chinese assessment and design standards were the same, which was conservative for the safety assessment of existing building structures. It was suggested to introduce the performance-based methods in the future revision of the Chinese assessment standards and modify the partial factors of the ultimate expression of bearing capacity according to the reliability theory.
The design and assessment standards of masonry structures in China, the US and Europe were briefly compared. The results showed that the US standard did not reduce the strength, and the European standard defined the adjustment method of partial coefficients. In the seismic assessment, the US and European standards adopted performance-based assessment methods, considering the influence of cognitive level, the representative values of gravity load and the calculation method of seismic bearing capacity were adjusted. The ultimate limit state function of bearing capacity in Chinese assessment and design standards were the same, which was conservative for the safety assessment of existing building structures. It was suggested to introduce the performance-based methods in the future revision of the Chinese assessment standards and modify the partial factors of the ultimate expression of bearing capacity according to the reliability theory.
2022, 52(6): 199-203.
doi: 10.13204/j.gyjzG21031009
Abstract:
Since the introduction of the special plan for the adjustment and transformation of national old industrial bases, the adjustment and transformation of China’s old industrial bases has made positive progress. Taking an existing factory as an example, the paper discussed the structure and layout adjustment project for the factory, from the aspects of formation history, carrent layout, industry needs, existing problems, planning and positioning, planning ideas, planning objectives, planning schemes, planning effect and so on, and the problems enconntered in optimization and adjustment of the overall layout of the old industrial park were analyzed and summarized, as well as the corresponding solutions.
Since the introduction of the special plan for the adjustment and transformation of national old industrial bases, the adjustment and transformation of China’s old industrial bases has made positive progress. Taking an existing factory as an example, the paper discussed the structure and layout adjustment project for the factory, from the aspects of formation history, carrent layout, industry needs, existing problems, planning and positioning, planning ideas, planning objectives, planning schemes, planning effect and so on, and the problems enconntered in optimization and adjustment of the overall layout of the old industrial park were analyzed and summarized, as well as the corresponding solutions.
2022, 52(6): 204-210.
doi: 10.13204/j.gyjzG21051106
Abstract:
Industrial mining heritage is an important part of industrial heritage, and its conservation and reuse are also important subjects in the field of industrial heritage conservation. The concept of industrial mining heritage and its related contents were introduced, the present condition in domestic and international about the conservation and reuse of industrial mining heritage was sorted out. Taking Wieliczka Salt Mine in Poland as an example, the paper analyzed its ideas and experience of conservation, operating, management, monitoring and reuse under the world heritage protection system, which could provide some references for the conservation and reuse of industrial mining heritage in China.
Industrial mining heritage is an important part of industrial heritage, and its conservation and reuse are also important subjects in the field of industrial heritage conservation. The concept of industrial mining heritage and its related contents were introduced, the present condition in domestic and international about the conservation and reuse of industrial mining heritage was sorted out. Taking Wieliczka Salt Mine in Poland as an example, the paper analyzed its ideas and experience of conservation, operating, management, monitoring and reuse under the world heritage protection system, which could provide some references for the conservation and reuse of industrial mining heritage in China.
