Login
Register
E-alert
2022 Vol. 52, No. 3
Display Method:
2022, 52(3): 1-9.
doi: 10.13204/j.gyjzG21083106
Abstract:
In order to explore the effect of horizontal freezing in water-rich fine sand layers, an experimental model tests was conducted. The effects of different salt water temperatures (at -20 ℃, -25 ℃ and -30 ℃) on frozen wall thickness, time of closure for the frozen wall, final frozen temperatures and frozen ranges were studied. The numerical model of horizontal freezing was established. By comparsion with the measured data, the numerical model was verified. The effects of initial temperatures, seepage speeds and clear space between two freezing tubes on the frozen temperature field were further simulated. The results showed that increasing the initial environmental temperature would reduce the thickness of frozen walls and delay the time for closure of frozen walls, but has little influence on the final frozen temperature. Groundwater seepage would migrate the cooling energy down to the lower zone, which would make the frozen wall in the upper zone thinner than that in the lower zone. The greater the seepage speed, the more obvious the difference between them. To increase the clear space between the two freezing tubes would reduce the thickness of the frozen wall, greatly delay the time of closure for frozen walls and lead to the increase of final frozen temperature.
In order to explore the effect of horizontal freezing in water-rich fine sand layers, an experimental model tests was conducted. The effects of different salt water temperatures (at -20 ℃, -25 ℃ and -30 ℃) on frozen wall thickness, time of closure for the frozen wall, final frozen temperatures and frozen ranges were studied. The numerical model of horizontal freezing was established. By comparsion with the measured data, the numerical model was verified. The effects of initial temperatures, seepage speeds and clear space between two freezing tubes on the frozen temperature field were further simulated. The results showed that increasing the initial environmental temperature would reduce the thickness of frozen walls and delay the time for closure of frozen walls, but has little influence on the final frozen temperature. Groundwater seepage would migrate the cooling energy down to the lower zone, which would make the frozen wall in the upper zone thinner than that in the lower zone. The greater the seepage speed, the more obvious the difference between them. To increase the clear space between the two freezing tubes would reduce the thickness of the frozen wall, greatly delay the time of closure for frozen walls and lead to the increase of final frozen temperature.
2022, 52(3): 10-16.
doi: 10.13204/j.gyjzG21063015
Abstract:
In the tunneling process of overlapping shield tunnels, the construction of post tunnelling tunnels may have a certain influence on tunnels constructed first and cause structure deformation of the tunnels, even affect their safety. Therefore, it was necessary to study the tunnelling process of overlapping tunnels in sandy pebble strata. Based on the tunnel project of Chengdu Metro Line No.6, different tunnelling modes of overlapping shield tunnels in sandy pebble strata were analyzed, and the optimal tunnelling mode was selected from the perspective of subsidence of the earth’s surface. The superposition effect of subsidence caused by tunnelling of overlapping tunnels was analyzed. Grouting reinforcement between overlapping tunnels was performed to improve compressive and shear strength of soil between tunnels and ensure the safety and stability of shield tunnelling. Finally, by comparing the measured data with the numerical simulation results, the errors were all within 5%. The transverse subsidence of the earth’s surface above the tunnel constructed first was approximately U-shaped. Although the subsidence of the tunnel constructed first was still in evolution during the construction of post tunnelling tunnels, the changes tended to be stable and the subsidence was lagging obversely, soil deformation was under control after grouting reinforcement.
In the tunneling process of overlapping shield tunnels, the construction of post tunnelling tunnels may have a certain influence on tunnels constructed first and cause structure deformation of the tunnels, even affect their safety. Therefore, it was necessary to study the tunnelling process of overlapping tunnels in sandy pebble strata. Based on the tunnel project of Chengdu Metro Line No.6, different tunnelling modes of overlapping shield tunnels in sandy pebble strata were analyzed, and the optimal tunnelling mode was selected from the perspective of subsidence of the earth’s surface. The superposition effect of subsidence caused by tunnelling of overlapping tunnels was analyzed. Grouting reinforcement between overlapping tunnels was performed to improve compressive and shear strength of soil between tunnels and ensure the safety and stability of shield tunnelling. Finally, by comparing the measured data with the numerical simulation results, the errors were all within 5%. The transverse subsidence of the earth’s surface above the tunnel constructed first was approximately U-shaped. Although the subsidence of the tunnel constructed first was still in evolution during the construction of post tunnelling tunnels, the changes tended to be stable and the subsidence was lagging obversely, soil deformation was under control after grouting reinforcement.
2022, 52(3): 17-23.
doi: 10.13204/j.gyjzG21022405
Abstract:
The construction of underground utility tunnels will inevitably be affected by ground fracture activities in urban areas where ground fissures are widely distributed. Based on existing physical model test results of rectangular tunnels, the damage effect and process caused by ground fracture were analyzed, and the numerical model was constructed. The validity of the numerical model was verified by comparing the test results and numerical simulation results. By constructing a three-dimensional finite element model of underground utility tunnels crossing ground fissures, four kinds of settlement cases of 50 mm, 100 mm, 150 mm and 200 mm were setted, and the length, height and angle of sand cushions were taken as variables. Numerical simulations were parformed and the results showed that the maximum longitudinal stress of utility tunnels had a decreasing trend with the gradual increase of the length, thickness and angle of the sand cushions within a certain range. Beyond a certain limit, the trend would abate. The optimal length, thickness and angle of sand cushions were 6 m, 3 m and 60° respectively. The maximum longitudinal stress in underground utility tunnels with sand replacement was significantly reduced by about 20% compared with that of underground utility tunnels which were untreated.
The construction of underground utility tunnels will inevitably be affected by ground fracture activities in urban areas where ground fissures are widely distributed. Based on existing physical model test results of rectangular tunnels, the damage effect and process caused by ground fracture were analyzed, and the numerical model was constructed. The validity of the numerical model was verified by comparing the test results and numerical simulation results. By constructing a three-dimensional finite element model of underground utility tunnels crossing ground fissures, four kinds of settlement cases of 50 mm, 100 mm, 150 mm and 200 mm were setted, and the length, height and angle of sand cushions were taken as variables. Numerical simulations were parformed and the results showed that the maximum longitudinal stress of utility tunnels had a decreasing trend with the gradual increase of the length, thickness and angle of the sand cushions within a certain range. Beyond a certain limit, the trend would abate. The optimal length, thickness and angle of sand cushions were 6 m, 3 m and 60° respectively. The maximum longitudinal stress in underground utility tunnels with sand replacement was significantly reduced by about 20% compared with that of underground utility tunnels which were untreated.
2022, 52(3): 24-28.
doi: 10.13204/j.gyjzG21062306
Abstract:
According to the influence of the lifting for immersed tubes, the roughness for bottom plates of immersed tubes and different injection sequences on the final expansion radius and gap filling of sand-deposite in the process of foundation treatment for immersed tube tunnels by the sand flow method, a full-scale test model of the sand flow method was constructed, and the influences of the above conditions on the expansion equilibrium and quality for sand-deposite were discussed by measuring and calculating filling degrees of the top surface, volume and radius of sand-deposite. Combined with the analysis of the expansion laws of sand-deposite, it was shown that the upward lifting of the pipe section was unfavourable to the expansion of sand-deposite, lower the filling degree was, poorer the expansion equilibrium and quality of sand-deposite were; the smooth material was used at the bottom of the pipe sections, which was conducive to expansion of sand-deposite and had a high filling degree and could improve the expansion equilibrium and quality of sand-deposite; the appropriate boundary sealing caused by different sand injection sequences would benefitted the improvement on filling degree of sand-deposite, improve the expansion equilibrium and quality of sand-deposite, and had no adverse effect on the final expansion equilibrium and filling quality of sand-deposite in gaps.
According to the influence of the lifting for immersed tubes, the roughness for bottom plates of immersed tubes and different injection sequences on the final expansion radius and gap filling of sand-deposite in the process of foundation treatment for immersed tube tunnels by the sand flow method, a full-scale test model of the sand flow method was constructed, and the influences of the above conditions on the expansion equilibrium and quality for sand-deposite were discussed by measuring and calculating filling degrees of the top surface, volume and radius of sand-deposite. Combined with the analysis of the expansion laws of sand-deposite, it was shown that the upward lifting of the pipe section was unfavourable to the expansion of sand-deposite, lower the filling degree was, poorer the expansion equilibrium and quality of sand-deposite were; the smooth material was used at the bottom of the pipe sections, which was conducive to expansion of sand-deposite and had a high filling degree and could improve the expansion equilibrium and quality of sand-deposite; the appropriate boundary sealing caused by different sand injection sequences would benefitted the improvement on filling degree of sand-deposite, improve the expansion equilibrium and quality of sand-deposite, and had no adverse effect on the final expansion equilibrium and filling quality of sand-deposite in gaps.
Effects of Jointed Rock Masses on Stability of Shield Tunnels Under Tunnelling and Ground Loss Rates
2022, 52(3): 29-37.
doi: 10.13204/j.gyjzG21052114
Abstract:
To explore the influence of joint rock masses on the stability of tunnels under tunnelling and the ground loss rates, taking the tunnel in Nanchang as a research object, the numerical model was constructed by the discrete element software UDEC. The influence of inclined joint angles on surrounding rock deformation and subsidence was analyzed, and the ground loss rate was obtained by fitting. The simulated values were compared with the measured values in order to study the influence of joint spacing, shield tunnel spacing and tunnel buried depth on subsidence. According to the actual project, a large displacement of surrounding rock of the tunnel occurred at the joint surface, and the existence of dip angles led to the eccentric compression phenomenon of rock around the tunnel. When the dip angle was 60° and 90°, it was prone to lose stability. The maximum value of subsidence occurred when the dip angle was 60°, and the minimum value occured when the dip angle was 45°. According to the Peck curve, the ground loss rate of the project section ranged from 0.658% to 0.896%. The subsidence was in negative correlation with buried depth, tunnel spacing and joint spacing.
To explore the influence of joint rock masses on the stability of tunnels under tunnelling and the ground loss rates, taking the tunnel in Nanchang as a research object, the numerical model was constructed by the discrete element software UDEC. The influence of inclined joint angles on surrounding rock deformation and subsidence was analyzed, and the ground loss rate was obtained by fitting. The simulated values were compared with the measured values in order to study the influence of joint spacing, shield tunnel spacing and tunnel buried depth on subsidence. According to the actual project, a large displacement of surrounding rock of the tunnel occurred at the joint surface, and the existence of dip angles led to the eccentric compression phenomenon of rock around the tunnel. When the dip angle was 60° and 90°, it was prone to lose stability. The maximum value of subsidence occurred when the dip angle was 60°, and the minimum value occured when the dip angle was 45°. According to the Peck curve, the ground loss rate of the project section ranged from 0.658% to 0.896%. The subsidence was in negative correlation with buried depth, tunnel spacing and joint spacing.
2022, 52(3): 38-43.
doi: 10.13204/j.gyjzG21090708
Abstract:
The gravity and the time-varying viscosity of slurry have a significant impact on the effective diffusion range and diffusion form of slurry, and the diffusion range of slurry plays a decisive role in the safety of tunnels. Based on the fluid-solid coupling theory and seepage mechanics theory, a grouting slurry diffusion equation was constructed considering the coupling effect of the gravity and the time-varying viscosity of slurry. The numerical simulation of grouting diffusion processes of pipe sheds in weathered slate in the Jiuzhai tunnel engineering was performed by software COMSOL Multiphysics. The influences of grouting pressure, time variation of slurry viscosity and grouting time on effective diffusion ranges of grouteing and formation of grouting reinforcement rings were analyzed. The results showed that the diffusion pattern of slurry in rock and soil was ellipsoid in consideration of the gravity of slurry. The smaller the grouting pressure and the longer the grouting time, the more significant the influence of slurry gravity on the diffusion pattern was. The diffusion ranges of the grouting above the horizontal level of the grouting hole was much smaller than that below the horizontal level, and the diffusion ranges of the grouting on the left and right sides of the grouting hole were symmetrical, which was consonant with the mechanism of gravity. The effect of time-varying viscosity on slurry diffusion was significant. The distribution form of the grouting reinforcement ring was closely related to the embedding angle of grouting pipes. The smaller the embedding angle of grouting pipes, the larger the thickness of the grouting reinforcement ring. The reasonable arrangements of small pipes were key to obtain the effective grouting reinforcement ring.
The gravity and the time-varying viscosity of slurry have a significant impact on the effective diffusion range and diffusion form of slurry, and the diffusion range of slurry plays a decisive role in the safety of tunnels. Based on the fluid-solid coupling theory and seepage mechanics theory, a grouting slurry diffusion equation was constructed considering the coupling effect of the gravity and the time-varying viscosity of slurry. The numerical simulation of grouting diffusion processes of pipe sheds in weathered slate in the Jiuzhai tunnel engineering was performed by software COMSOL Multiphysics. The influences of grouting pressure, time variation of slurry viscosity and grouting time on effective diffusion ranges of grouteing and formation of grouting reinforcement rings were analyzed. The results showed that the diffusion pattern of slurry in rock and soil was ellipsoid in consideration of the gravity of slurry. The smaller the grouting pressure and the longer the grouting time, the more significant the influence of slurry gravity on the diffusion pattern was. The diffusion ranges of the grouting above the horizontal level of the grouting hole was much smaller than that below the horizontal level, and the diffusion ranges of the grouting on the left and right sides of the grouting hole were symmetrical, which was consonant with the mechanism of gravity. The effect of time-varying viscosity on slurry diffusion was significant. The distribution form of the grouting reinforcement ring was closely related to the embedding angle of grouting pipes. The smaller the embedding angle of grouting pipes, the larger the thickness of the grouting reinforcement ring. The reasonable arrangements of small pipes were key to obtain the effective grouting reinforcement ring.
2022, 52(3): 44-52,37.
doi: 10.13204/j.gyjzG21111717
Abstract:
The void phenomenon behind the tunnel lining has become the main cause of tunnel diseases, which easily triggers the damage of tunnel lining structure, shedding, water seepage and other diseases, and seriously threatened the normal operation of tunnels. The void behind the lining seriously reduced the aseismic capacity of tunnels. The mechanical parameters of surrounding rock were calculated in inversion by the optimizing analysis method of improved system identification sensitivity, and the numerical model for the dynamic response of tunnels was optimized by the improved inversion results to study the repair effect and aseismic capacity of the Longmianshan tunnel repaired the void behind the lining grouted by polymer. The results showed that the displacement and stress in the repaired zone at the top of the secondary lining of the tunnel were significantly reduced and close the normal; however, there were significantly different in the stress and displacement at the top of the secondary lining subjected to seismic waves of the same peak acceleration in different site conditions, indicating that the dynamic response of the tunnel model had significant sensitivity to the seismic wave spectrum.
The void phenomenon behind the tunnel lining has become the main cause of tunnel diseases, which easily triggers the damage of tunnel lining structure, shedding, water seepage and other diseases, and seriously threatened the normal operation of tunnels. The void behind the lining seriously reduced the aseismic capacity of tunnels. The mechanical parameters of surrounding rock were calculated in inversion by the optimizing analysis method of improved system identification sensitivity, and the numerical model for the dynamic response of tunnels was optimized by the improved inversion results to study the repair effect and aseismic capacity of the Longmianshan tunnel repaired the void behind the lining grouted by polymer. The results showed that the displacement and stress in the repaired zone at the top of the secondary lining of the tunnel were significantly reduced and close the normal; however, there were significantly different in the stress and displacement at the top of the secondary lining subjected to seismic waves of the same peak acceleration in different site conditions, indicating that the dynamic response of the tunnel model had significant sensitivity to the seismic wave spectrum.
2022, 52(3): 53-59,104.
doi: 10.13204/j.gyjzG20122322
Abstract:
To improve the safety of tunnel construction, the calculation methods for tunnel deformation caused by calculation methods deep aucavation construction were discussed. The influencing factors of heave deformation on tunnels were analyzed, and the for heave deformation caused by unloading during excavation were simplifien. The additional load on tunnels and foundation beam stiffness of tunnels caused by unloading in excavation were analyzed by two-stage analysis method. Finally, the finite element analysis method was used to analyze the tunnel deformation caused by municipal construction of Line 2 in Xi’an. The results showed that: The application of two-stage stress analysis method successfully calculated the additional load on the tunnel caused by unloading deep excavation. The Pasternak model, Winkler model, and Kerr model were used, and the Kerr model was more accurate.
To improve the safety of tunnel construction, the calculation methods for tunnel deformation caused by calculation methods deep aucavation construction were discussed. The influencing factors of heave deformation on tunnels were analyzed, and the for heave deformation caused by unloading during excavation were simplifien. The additional load on tunnels and foundation beam stiffness of tunnels caused by unloading in excavation were analyzed by two-stage analysis method. Finally, the finite element analysis method was used to analyze the tunnel deformation caused by municipal construction of Line 2 in Xi’an. The results showed that: The application of two-stage stress analysis method successfully calculated the additional load on the tunnel caused by unloading deep excavation. The Pasternak model, Winkler model, and Kerr model were used, and the Kerr model was more accurate.
2022, 52(3): 60-66,84.
doi: 10.13204/j.gyjzG21081712
Abstract:
The stability of underground structures and the deformation control of surrounding environments are key and difficult subjects in shallow tunnels crossing below important infrastructures,and the pipe-shed method is an important technical measure, which can improve the stability for the environment of rock and soil. Combined with an engineering practice of a long-span, flat and superly shallow tunnel in Fujian Province, which was used the superly long pipe-shed method to cross below main lines, the working principles of the pipe-shed system were analyzed, and the construction methods and crucially technical points of superly long pipe-sheds in ultra shallow tunnels were summarized and put forward. Based on the Winkler elastic foundation beam theory,considering the construction process of three-step tunnelling to reserve core soil,the laws for subsidence of the earth’s surface and the internal force distribution characteristics of the tunnel support structure were analyzed to guide the setting of support parameters and support measures on site. Based on the measured results, the rationality of the calculation results and support measures were vindicated. Combined with the construction process and environmental characteristics, the principle of the subsidence was discussed in detail. Finally,based on the measured subsidence,the subsidence characteristics and influencing factors caused by superly long pipe-shed construction were analyzed systematically. According to the actual engineering characteristics,the control measures of rail deformation were proposed,and the subsidence control methods were proposed from key points of construction techniques.
The stability of underground structures and the deformation control of surrounding environments are key and difficult subjects in shallow tunnels crossing below important infrastructures,and the pipe-shed method is an important technical measure, which can improve the stability for the environment of rock and soil. Combined with an engineering practice of a long-span, flat and superly shallow tunnel in Fujian Province, which was used the superly long pipe-shed method to cross below main lines, the working principles of the pipe-shed system were analyzed, and the construction methods and crucially technical points of superly long pipe-sheds in ultra shallow tunnels were summarized and put forward. Based on the Winkler elastic foundation beam theory,considering the construction process of three-step tunnelling to reserve core soil,the laws for subsidence of the earth’s surface and the internal force distribution characteristics of the tunnel support structure were analyzed to guide the setting of support parameters and support measures on site. Based on the measured results, the rationality of the calculation results and support measures were vindicated. Combined with the construction process and environmental characteristics, the principle of the subsidence was discussed in detail. Finally,based on the measured subsidence,the subsidence characteristics and influencing factors caused by superly long pipe-shed construction were analyzed systematically. According to the actual engineering characteristics,the control measures of rail deformation were proposed,and the subsidence control methods were proposed from key points of construction techniques.
2022, 52(3): 67-70,76.
doi: 10.13204/j.gyjzG21060907
Abstract:
Taking power tunnels as research objects, the field measurement was conducted to study and analyze the force characteristics of jacked pipes under construction of a large-diameter, long-distance and spatially C-shaped curve. The results showed that: in the case of pipe sections in full contact with slurry, the total thrust had few relations with the cumulative jacked distances, and the thickness of overlying soil had an effect on the contact pressure of pipe walls, but the grouting pressure was the dominant factor; the stress in circumferential rebas was mainly in compression, pipe sections was in compression on the inside and in tension on the outside, and the diameters at the ends of pipe sections were compressed to "ellipsoid"; the longitudinal rebars in the left and upper parts of pipe sections were in compression, as well as the rebars in the right and lower parts of pipe sections were in tension, and the pipe sections were deflected under the action of bending moment and the middle part of the pipe sections deflected to the right. Thus, the reasonable distribution of rebars and increasing prestressed rebars could optimize the pipeline design, improve pipeline performances and economic benefits.
Taking power tunnels as research objects, the field measurement was conducted to study and analyze the force characteristics of jacked pipes under construction of a large-diameter, long-distance and spatially C-shaped curve. The results showed that: in the case of pipe sections in full contact with slurry, the total thrust had few relations with the cumulative jacked distances, and the thickness of overlying soil had an effect on the contact pressure of pipe walls, but the grouting pressure was the dominant factor; the stress in circumferential rebas was mainly in compression, pipe sections was in compression on the inside and in tension on the outside, and the diameters at the ends of pipe sections were compressed to "ellipsoid"; the longitudinal rebars in the left and upper parts of pipe sections were in compression, as well as the rebars in the right and lower parts of pipe sections were in tension, and the pipe sections were deflected under the action of bending moment and the middle part of the pipe sections deflected to the right. Thus, the reasonable distribution of rebars and increasing prestressed rebars could optimize the pipeline design, improve pipeline performances and economic benefits.
2022, 52(3): 71-76.
doi: 10.13204/j.gyjzG21043001
Abstract:
At the urban level, the aggregation degree of travels in the streets can reflect the significance of different street segments on urban public life. There are limitations in the previous quantification research on street network. Based on the improvement of the space syntax segment maps, the paper proposed to evaluate the travel aggregation degree of street segments at the urban level by placing them in the urban street network. First of all, the data of study area was collected, and the topological radius of common travel modes were selected to format the segment maps. Then, the accessibility of models with different travel modes was analyzed. Secondly, taking the proportion of different travel modes as weight, the superposition calculation of additional weights was performed, and the models were classified and evaluated in terms of the travel aggregation degree of street networks. Finally, the effects of street network’s travel aggregation degree evaluation on function adjustment and capacity improvement of space along street were discussed, as well as the significance of selection and renewal design of key street intersections and segments. The study could provide a method for the overall understanding of street segments’ value on public life. It could be a design reference for the return of public life to the street.
At the urban level, the aggregation degree of travels in the streets can reflect the significance of different street segments on urban public life. There are limitations in the previous quantification research on street network. Based on the improvement of the space syntax segment maps, the paper proposed to evaluate the travel aggregation degree of street segments at the urban level by placing them in the urban street network. First of all, the data of study area was collected, and the topological radius of common travel modes were selected to format the segment maps. Then, the accessibility of models with different travel modes was analyzed. Secondly, taking the proportion of different travel modes as weight, the superposition calculation of additional weights was performed, and the models were classified and evaluated in terms of the travel aggregation degree of street networks. Finally, the effects of street network’s travel aggregation degree evaluation on function adjustment and capacity improvement of space along street were discussed, as well as the significance of selection and renewal design of key street intersections and segments. The study could provide a method for the overall understanding of street segments’ value on public life. It could be a design reference for the return of public life to the street.
2022, 52(3): 77-84.
doi: 10.13204/j.gyjzG20112503
Abstract:
In the post-industrial era, cultural and creative industries are growing rapidly. With its unique landscape, many old industrial districts have transformed into ideal spaces for the development of cultural and creative industries. Taking the cultural and creative parks transformed from old factory in Guangzhou as an example, the paper studied the factors influencing the satisfaction of these parks, so as to provide suggestions for future improvement. Based on the traditional location theory, the paper introduced the scene theory to construct the index system of influencing factors of satisfaction of these parks, and used the factor analysis method to evaluate the influencing factors. The study found that the characteristics and location conditions of cultural activity scenes were the key factors influencing the satisfaction of the cultural and creative parks transformed from old factories. Other cultural scene characteristics, such as convenient services and facilities, talent and cultural values, also played important roles in the transformation. In order to achieve long-term and healthy development of the cultural and creative parks, the development trend of cultural and creative industry should be closely followed, the level of scene construction should be improved, personalized cultural and creative parks should be built, the construction of talent team should be strengthened, the supporting facilities of park should be optimizied, and finally, the corresponding planning and policy guidance should be improved.
In the post-industrial era, cultural and creative industries are growing rapidly. With its unique landscape, many old industrial districts have transformed into ideal spaces for the development of cultural and creative industries. Taking the cultural and creative parks transformed from old factory in Guangzhou as an example, the paper studied the factors influencing the satisfaction of these parks, so as to provide suggestions for future improvement. Based on the traditional location theory, the paper introduced the scene theory to construct the index system of influencing factors of satisfaction of these parks, and used the factor analysis method to evaluate the influencing factors. The study found that the characteristics and location conditions of cultural activity scenes were the key factors influencing the satisfaction of the cultural and creative parks transformed from old factories. Other cultural scene characteristics, such as convenient services and facilities, talent and cultural values, also played important roles in the transformation. In order to achieve long-term and healthy development of the cultural and creative parks, the development trend of cultural and creative industry should be closely followed, the level of scene construction should be improved, personalized cultural and creative parks should be built, the construction of talent team should be strengthened, the supporting facilities of park should be optimizied, and finally, the corresponding planning and policy guidance should be improved.
2022, 52(3): 85-91.
doi: 10.13204/j.gyjzG22010416
Abstract:
Learning the status quo of thermal environment comfort is necessary for the renewal and retrofit of traditional buildings. At present, physical environment measurement and subjective survey are the basic methods of thermal environment evaluation, but the different emphasis of decision-making model between them leads to the obvious difference of evaluation results. Taking the typical brick-timber dwellings of Daokou Town in North Henan Province as an example, the research data were obtained by combining the results of wind environment simulation, physical environment measurement and questionnaire survey. PMV, APMV, adaptive thermal comfort model and thermal sensation were used for evaluation and comparative analysis. The research showed that: 1)there was a big difference between the residents’ subjective feeling about the thermal environment and the objective evaluation. From the evaluation results, the APMV model were closer to the thermal sensation; 2)residents’ cold adaptability was an important reason for the difference between evaluation results of different models. Considering residents’ desire for thermal comfort, the thermal adaptability as well as thermal preference of local people should be fully considered in renewal and transformation process; 3)the status quo of indoor thermal environment deviated greatly from the thermal comfort standard of urban residential buildings, so it was not suitable to adopt urban standards to improve the thermal environment of traditional dwellings; 4)the air tightness of enclosure systom, the fluctuation of indoor temperature, and the protection of historical building style were important concerns in the renewal and retrofit process of traditional dwellings.
Learning the status quo of thermal environment comfort is necessary for the renewal and retrofit of traditional buildings. At present, physical environment measurement and subjective survey are the basic methods of thermal environment evaluation, but the different emphasis of decision-making model between them leads to the obvious difference of evaluation results. Taking the typical brick-timber dwellings of Daokou Town in North Henan Province as an example, the research data were obtained by combining the results of wind environment simulation, physical environment measurement and questionnaire survey. PMV, APMV, adaptive thermal comfort model and thermal sensation were used for evaluation and comparative analysis. The research showed that: 1)there was a big difference between the residents’ subjective feeling about the thermal environment and the objective evaluation. From the evaluation results, the APMV model were closer to the thermal sensation; 2)residents’ cold adaptability was an important reason for the difference between evaluation results of different models. Considering residents’ desire for thermal comfort, the thermal adaptability as well as thermal preference of local people should be fully considered in renewal and transformation process; 3)the status quo of indoor thermal environment deviated greatly from the thermal comfort standard of urban residential buildings, so it was not suitable to adopt urban standards to improve the thermal environment of traditional dwellings; 4)the air tightness of enclosure systom, the fluctuation of indoor temperature, and the protection of historical building style were important concerns in the renewal and retrofit process of traditional dwellings.
2022, 52(3): 92-97,157.
doi: 10.13204/j.gyjzG20090801
Abstract:
Industrial buildings often generate a lot of waste heat and noxious gases in the operation process. Good ventilation can dissipate the outdoor pollutants in the industrial building clusters and thereby improve the working environment and adjust local micro-climate. Optimizing the outdoor wind environment for industrial building clusters at the design phrase can effectively improve the ventilation effect of the built environment. This research broke down the simulation procedure for wind environment in industrial building clusters, and used digital technology to build up simulation modules. The new simulation method would automatically run the repeated steps in the numerical modeling. It also established a numerical simulation method that could efficiently compare different design options using evaluation factors such as comfortable wind zone ratio, calm wind zone ratio and so on. Based on the case study of a packaging materials plant, the outdoor wind environment of the factory was analyzed by numerical simulation in the design stage, and the distance between each partition of the finishing workshop was optimized. It was found that, based on the on-site measurement, the wind speed in the industrial building clusters would meet the requirements for outdoor wind environment.
Industrial buildings often generate a lot of waste heat and noxious gases in the operation process. Good ventilation can dissipate the outdoor pollutants in the industrial building clusters and thereby improve the working environment and adjust local micro-climate. Optimizing the outdoor wind environment for industrial building clusters at the design phrase can effectively improve the ventilation effect of the built environment. This research broke down the simulation procedure for wind environment in industrial building clusters, and used digital technology to build up simulation modules. The new simulation method would automatically run the repeated steps in the numerical modeling. It also established a numerical simulation method that could efficiently compare different design options using evaluation factors such as comfortable wind zone ratio, calm wind zone ratio and so on. Based on the case study of a packaging materials plant, the outdoor wind environment of the factory was analyzed by numerical simulation in the design stage, and the distance between each partition of the finishing workshop was optimized. It was found that, based on the on-site measurement, the wind speed in the industrial building clusters would meet the requirements for outdoor wind environment.
2022, 52(3): 98-104.
doi: 10.13204/j.gyjzG21061603
Abstract:
In order to demand the design method of efficient use of small-area residential space, based on the key techniques of "people-oriented", "simple and easy" and "space adaptability" of the residential building system and the multi-dimensional utilization form of residential space and time, the design of the deversity of residential space based on user needs was explored from the aspects of the diversification of the number of rooms, the efficient use of space constants such as the individualization of partition shape and the differentiation of space layout, the efficient use of space variables such as the diversity of sets, the exchange of space diversity, and the sharing of space diversity, as well as the flexibility of furniture and space partitions in daily life and the variability of spatial constants and spatial variables in long-term development. It was proposed that the design of residence with efficient use of space should not only be varied from person to person, but also need to be precisely designed according to needs, and should be appropriately integrated into sustainable development design according to needs, in addition, the principle of "easy to build, changeable, easy to evolve" should be taken into account in the construction process, so that the design of residence could can make adaptive and efficient use of space and center on user needs from indoor to house or from results to process, and thus the design mode of efficient space utilization based on household needs was summarized.
In order to demand the design method of efficient use of small-area residential space, based on the key techniques of "people-oriented", "simple and easy" and "space adaptability" of the residential building system and the multi-dimensional utilization form of residential space and time, the design of the deversity of residential space based on user needs was explored from the aspects of the diversification of the number of rooms, the efficient use of space constants such as the individualization of partition shape and the differentiation of space layout, the efficient use of space variables such as the diversity of sets, the exchange of space diversity, and the sharing of space diversity, as well as the flexibility of furniture and space partitions in daily life and the variability of spatial constants and spatial variables in long-term development. It was proposed that the design of residence with efficient use of space should not only be varied from person to person, but also need to be precisely designed according to needs, and should be appropriately integrated into sustainable development design according to needs, in addition, the principle of "easy to build, changeable, easy to evolve" should be taken into account in the construction process, so that the design of residence could can make adaptive and efficient use of space and center on user needs from indoor to house or from results to process, and thus the design mode of efficient space utilization based on household needs was summarized.
2022, 52(3): 105-111.
doi: 10.13204/j.gyjzG21020311
Abstract:
Based on the existing prefabricated concrete frame structure, the paper proposed a new type of prefabricated asymmetric hybrid connection joint (PPEFF joint). The longitudinal reinforcement of the beam of this joint was arranged asymmetrically, and only energy-dissipating steel bars were installed on the upper part of the beam. While the joint meets high construction efficiency, shear steel bars were installed on the contact surface of the beam and column, which improved the bearing capacity of the contact surface of the beam and column, so as to ensure the safety of the structure after the accidental failure of the joint prestress. In order to study the influence of the reinforcement ratio of shear steel bars on the seismic performance of PPEFF joints, the paper combined low-cycle reciprocating load test and ABAQUS finite element software simulation analysis, focusing on bearing capacity of joint, energy-dissipating capacity, stiffness degradation and self-restting capacity, etc. The influence of the reinforcement ratio of shear steel bars on the seismic performance of joints was analyzed from these four aspects. Through the research in this paper, it was found that the PPEFF joint had better seismic performance, and the increase in the reinforcement ratio of the shear steel bars would increase the joint bearing capacity, stiffness, and energy dissipation capacity. However, the setting of shear reinforcement improved the section stiffness of the joint and inhibited the self-resetting capacity of the joint to a certain extent, which violated the original intention of the self-resetting capacity of the pre-compressed assembled joint. Therefore, it was recommended that the reinforcement ratio of shear steel bars in PPEFF joints should be set to 0.3% to 0.5%. At the same time, the calculation formula for the bearing capacity of the beam-column contact surface of the PPEFF joint was proposed, and the applicability of the calculation formula for the bearing capacity of the beam-column contact surface was verified through the test data and the simulation data.
Based on the existing prefabricated concrete frame structure, the paper proposed a new type of prefabricated asymmetric hybrid connection joint (PPEFF joint). The longitudinal reinforcement of the beam of this joint was arranged asymmetrically, and only energy-dissipating steel bars were installed on the upper part of the beam. While the joint meets high construction efficiency, shear steel bars were installed on the contact surface of the beam and column, which improved the bearing capacity of the contact surface of the beam and column, so as to ensure the safety of the structure after the accidental failure of the joint prestress. In order to study the influence of the reinforcement ratio of shear steel bars on the seismic performance of PPEFF joints, the paper combined low-cycle reciprocating load test and ABAQUS finite element software simulation analysis, focusing on bearing capacity of joint, energy-dissipating capacity, stiffness degradation and self-restting capacity, etc. The influence of the reinforcement ratio of shear steel bars on the seismic performance of joints was analyzed from these four aspects. Through the research in this paper, it was found that the PPEFF joint had better seismic performance, and the increase in the reinforcement ratio of the shear steel bars would increase the joint bearing capacity, stiffness, and energy dissipation capacity. However, the setting of shear reinforcement improved the section stiffness of the joint and inhibited the self-resetting capacity of the joint to a certain extent, which violated the original intention of the self-resetting capacity of the pre-compressed assembled joint. Therefore, it was recommended that the reinforcement ratio of shear steel bars in PPEFF joints should be set to 0.3% to 0.5%. At the same time, the calculation formula for the bearing capacity of the beam-column contact surface of the PPEFF joint was proposed, and the applicability of the calculation formula for the bearing capacity of the beam-column contact surface was verified through the test data and the simulation data.
2022, 52(3): 112-116,207.
doi: 10.13204/j.gyjzG21052901
Abstract:
To investigated the distortion effect and the influence of diaphragms in the span on the distortion of the simply supported thin-walled box girder. Based on the improved distortion analysis theory of box girder, the distortion control differential equation with the web vertical deflection as the unknown quantity was established and solved by Galerkin methods. The relationship between distortion sector coordinates and distortion warping moment inertia of rectangular cross section box girder with distortion angle and web distortion deflection as unknown quantity were analyzed. Through an example, the influence of the number of diaphragms on the distortion deformation of simply supported box girder was studied by analytical method. The results show that the influence of the number of diaphragms on the distortion deformation of box girder by Galerkin methods is more intuitive. When end diaphragms existence, three diaphragms set in the box girder, the web vertical deflection can be reduced to 98.84% of that only end diaphragms. When there are more than three diaphragms in the box girder, the effect of limiting the distortion deformation of box girder can not be significantly improved. The distortion deflection calculated by proposed method is close to the finite element results, and is in good agreement with the calculated results of the modified relevant literature formulas.
To investigated the distortion effect and the influence of diaphragms in the span on the distortion of the simply supported thin-walled box girder. Based on the improved distortion analysis theory of box girder, the distortion control differential equation with the web vertical deflection as the unknown quantity was established and solved by Galerkin methods. The relationship between distortion sector coordinates and distortion warping moment inertia of rectangular cross section box girder with distortion angle and web distortion deflection as unknown quantity were analyzed. Through an example, the influence of the number of diaphragms on the distortion deformation of simply supported box girder was studied by analytical method. The results show that the influence of the number of diaphragms on the distortion deformation of box girder by Galerkin methods is more intuitive. When end diaphragms existence, three diaphragms set in the box girder, the web vertical deflection can be reduced to 98.84% of that only end diaphragms. When there are more than three diaphragms in the box girder, the effect of limiting the distortion deformation of box girder can not be significantly improved. The distortion deflection calculated by proposed method is close to the finite element results, and is in good agreement with the calculated results of the modified relevant literature formulas.
2022, 52(3): 117-122.
doi: 10.13204/j.gyjzG21062921
Abstract:
The construction period of super high-rise building is long. In the whole construction process when the overall stiffness of the structure has not been formed, the safety of the structure under various construction loads, environmental wind and earthquake in the construction period was one of the key problems worthy of attention. In order to study the above problems, the numerical simulation method was adopted in this paper. The influence of strong earthquake on structural safety during construction was analyzed at different stages when the overall stiffness of the structure is incomplete. The South Tower of the Yinchuan Greenland Center super high-rise project was taken as an example. The structure consists of an outrigger truss connected steel frame-reinforced and concrete core tube. The birth and death technology of the element in ANSYS was used to simulate the whole process of the construction of the South Tower. Through calculation and analysis, the obtained maximum stress was compared with the allowable stress of the material, the maximum displacement was compared with the displacement limit required by the specification, and the safety of the structure was evaluated. The results showed that the maximum stress, inter-story displacement and inter-story drift ratio were smaller than the limits in the specification, and the structure could meet the reliability requirements during construction. It was found that the outrigger truss could significantly improve the lateral stiffness of the structure before and after connecting the inner and outer tubes, the maximum Y-direction displacement was reduced by 12.1%, and the maximum Mises stress of the outer frame tube and the core tube was reduced by 33.3% and 25.2% respectively.
The construction period of super high-rise building is long. In the whole construction process when the overall stiffness of the structure has not been formed, the safety of the structure under various construction loads, environmental wind and earthquake in the construction period was one of the key problems worthy of attention. In order to study the above problems, the numerical simulation method was adopted in this paper. The influence of strong earthquake on structural safety during construction was analyzed at different stages when the overall stiffness of the structure is incomplete. The South Tower of the Yinchuan Greenland Center super high-rise project was taken as an example. The structure consists of an outrigger truss connected steel frame-reinforced and concrete core tube. The birth and death technology of the element in ANSYS was used to simulate the whole process of the construction of the South Tower. Through calculation and analysis, the obtained maximum stress was compared with the allowable stress of the material, the maximum displacement was compared with the displacement limit required by the specification, and the safety of the structure was evaluated. The results showed that the maximum stress, inter-story displacement and inter-story drift ratio were smaller than the limits in the specification, and the structure could meet the reliability requirements during construction. It was found that the outrigger truss could significantly improve the lateral stiffness of the structure before and after connecting the inner and outer tubes, the maximum Y-direction displacement was reduced by 12.1%, and the maximum Mises stress of the outer frame tube and the core tube was reduced by 33.3% and 25.2% respectively.
2022, 52(3): 123-131.
doi: 10.13204/j.gyjzG20072410
Abstract:
In order to explore the vibration dynamic performance of the gymnasium floor structure under complex excitation, a dynamic signal acquisition and analysis was used system to experimentally determine the speed response and energy distribution change rules of different distribution pilots of the gymnasium. The vibration characteristics under the excitation of single people and two people were summarized through experimental analysis. The energy distribution of each pilot site was affected by factors such as the supported constraints, different types of excitation modes, and the location of the loaded excitation. Among them, the excitations loaded in different distribution pilotss locations was the main factor which determined the law of energy distribution. Compared with different excitation types such as walking, jumping, dancing, and bouncing, jumping excitation had more input energy than bouncing excitation, so that the response of each pilot exhibited a more regular form of beat vibration. The energy was absorbed by the floor, showing a random structural dynamic response.
In order to explore the vibration dynamic performance of the gymnasium floor structure under complex excitation, a dynamic signal acquisition and analysis was used system to experimentally determine the speed response and energy distribution change rules of different distribution pilots of the gymnasium. The vibration characteristics under the excitation of single people and two people were summarized through experimental analysis. The energy distribution of each pilot site was affected by factors such as the supported constraints, different types of excitation modes, and the location of the loaded excitation. Among them, the excitations loaded in different distribution pilotss locations was the main factor which determined the law of energy distribution. Compared with different excitation types such as walking, jumping, dancing, and bouncing, jumping excitation had more input energy than bouncing excitation, so that the response of each pilot exhibited a more regular form of beat vibration. The energy was absorbed by the floor, showing a random structural dynamic response.
2022, 52(3): 132-140.
doi: 10.13204/j.gyjzG21082001
Abstract:
In order to study the static behavior of CHS-to-SHS gap N-joins and its relations with the behavior of overlap joints, two CHS-to-SHS gap N-joints and two corresponding overlap joints were tested. The test revealed that the bearing capacity of the gap joints was lower than that of the overlap joints with the same diameter of the tubes. Obvious local plasticity failure of the chord occurred in all the four joints, and local buckling also occurred in the two joints with smaller branches. Meanwhile, the relative deformation of the chord wall of the gap joints was larger than that of the corresponding overlap joints at the ultimate state. Based on the experiment, the finite element analysis models of CHS-to-SHS gap N-joints were established, and the finite element analysis of the joints with different brace-to-chord width ratios, chord width-to-thickness ratios, brace-to-chord thickness ratio, axial loads of chord and gap sizes between braces was carried out. The analysis results showed that the main failure modes of the gap joints were the brace member failure(BMF), the chord plasticity failure(CP), and the combined failure of brace local buckling and chord plasticity(BLB+CP). Moreover, the influence of brace-to-chord width ratio, chord width-to-thickness ratio, brace-to-chord thickness ratio and axial force of chord on the bearing capacity of CHS-to-SHS gap N-joints was similar to that of corresponding overlap joints. Furthermore, the effect of gap size between braces on the bearing resistance of CHS-to-SHS gap N-joints could not be neglected. Finally, based on the design equation in the code, a formula for predicting the ultimate bearing capacity of CHS-to-SHS gap N-joints was proposed by applying multivariate regression analysis.
In order to study the static behavior of CHS-to-SHS gap N-joins and its relations with the behavior of overlap joints, two CHS-to-SHS gap N-joints and two corresponding overlap joints were tested. The test revealed that the bearing capacity of the gap joints was lower than that of the overlap joints with the same diameter of the tubes. Obvious local plasticity failure of the chord occurred in all the four joints, and local buckling also occurred in the two joints with smaller branches. Meanwhile, the relative deformation of the chord wall of the gap joints was larger than that of the corresponding overlap joints at the ultimate state. Based on the experiment, the finite element analysis models of CHS-to-SHS gap N-joints were established, and the finite element analysis of the joints with different brace-to-chord width ratios, chord width-to-thickness ratios, brace-to-chord thickness ratio, axial loads of chord and gap sizes between braces was carried out. The analysis results showed that the main failure modes of the gap joints were the brace member failure(BMF), the chord plasticity failure(CP), and the combined failure of brace local buckling and chord plasticity(BLB+CP). Moreover, the influence of brace-to-chord width ratio, chord width-to-thickness ratio, brace-to-chord thickness ratio and axial force of chord on the bearing capacity of CHS-to-SHS gap N-joints was similar to that of corresponding overlap joints. Furthermore, the effect of gap size between braces on the bearing resistance of CHS-to-SHS gap N-joints could not be neglected. Finally, based on the design equation in the code, a formula for predicting the ultimate bearing capacity of CHS-to-SHS gap N-joints was proposed by applying multivariate regression analysis.
2022, 52(3): 141-145.
doi: 10.13204/j.gyjzG20103102
Abstract:
The steel spherical hinged support is in complex stress states subjected to various load combinations. In order to assess its mechanical properties and the influence on integral structural safety, taking the large support of T2 of Guangzhou Baiyun International Airport as an example, the numerical simulation analysis and full-scale model experiment for the shear properties of the support subjected to axial compressive load were carried out. It was indicated that the stress and deformation curves of experiments and numerical simulation results were coincident. The support was in low stress level. In addition, the relations between horizontal displacement and horizontal shear force was linear. On this basis, according to the test and simulation results, the fitted shear stiffness model of the support subjected to axial compressive load was proposed for the refinement mechanical analysis of integral structure.
The steel spherical hinged support is in complex stress states subjected to various load combinations. In order to assess its mechanical properties and the influence on integral structural safety, taking the large support of T2 of Guangzhou Baiyun International Airport as an example, the numerical simulation analysis and full-scale model experiment for the shear properties of the support subjected to axial compressive load were carried out. It was indicated that the stress and deformation curves of experiments and numerical simulation results were coincident. The support was in low stress level. In addition, the relations between horizontal displacement and horizontal shear force was linear. On this basis, according to the test and simulation results, the fitted shear stiffness model of the support subjected to axial compressive load was proposed for the refinement mechanical analysis of integral structure.
2022, 52(3): 146-149,190.
doi: 10.13204/j.gyjzG20041009
Abstract:
Taking a SJ2-18 deviation angle tower with 220 kV voltage level designed by a design company in Anhui as an example, the research on full-scale test of the tower was carried out to verify the safety of weather-resistant cold-formed steel applied to deviation angle towers. The SJ2-18 deviation angle tower made of weather-resistant cold-formed steel passed the 100% design load test under 8 working conditions. The shear failure of the connecting bolts between the SJ2-18 leg and the SJ2-18 foot occurred when the load reached 140%. The test results showed that the structure design of the SJ2-18 deviation angle tower was reasonable, with safe and reliable strength which could meet the requirements of DL/T 5154-2012. The research results could provide an experimental basis for the application of weather-resistant cold-formed steel deviation angle towers, and provide technical support for the promotion of weather-resistant cold-formed steel deviation angle towers.
Taking a SJ2-18 deviation angle tower with 220 kV voltage level designed by a design company in Anhui as an example, the research on full-scale test of the tower was carried out to verify the safety of weather-resistant cold-formed steel applied to deviation angle towers. The SJ2-18 deviation angle tower made of weather-resistant cold-formed steel passed the 100% design load test under 8 working conditions. The shear failure of the connecting bolts between the SJ2-18 leg and the SJ2-18 foot occurred when the load reached 140%. The test results showed that the structure design of the SJ2-18 deviation angle tower was reasonable, with safe and reliable strength which could meet the requirements of DL/T 5154-2012. The research results could provide an experimental basis for the application of weather-resistant cold-formed steel deviation angle towers, and provide technical support for the promotion of weather-resistant cold-formed steel deviation angle towers.
2022, 52(3): 150-157.
doi: 10.13204/j.gyjzG21081911
Abstract:
In order to study the asynchronous lifting performance of the attached lifting scaffold, the all-steel integrated attached lifting scaffold was used as the test frame to measure the stress changes of the main stressed components during the lifting process. The finite element model of the frame was established in ABAQUS and the correctness of the finite element analysis results was verified according to the test results. On this basis, the asynchronous motion performance under 32 working conditions was analyzed. The results showed that when the displacement difference between adjacent hoister exceeded 30 mm or when the hoister overload and hoister load loss occurred, the maximum asynchronous coefficient was 2.33 and its minimum was 1.16. Its average value was 1.82.At present, the non-uniformity coefficient of load was 2.0 in the Safety Technical Code for Construction Tool Scaffold (JGJ 202-2010). Based on the analysis results, it was suggested to increase the non-uniformity coefficient of load to 2.35 or decrease the allowable position displacement difference to ensure the safe using of lifting scaffold.
In order to study the asynchronous lifting performance of the attached lifting scaffold, the all-steel integrated attached lifting scaffold was used as the test frame to measure the stress changes of the main stressed components during the lifting process. The finite element model of the frame was established in ABAQUS and the correctness of the finite element analysis results was verified according to the test results. On this basis, the asynchronous motion performance under 32 working conditions was analyzed. The results showed that when the displacement difference between adjacent hoister exceeded 30 mm or when the hoister overload and hoister load loss occurred, the maximum asynchronous coefficient was 2.33 and its minimum was 1.16. Its average value was 1.82.At present, the non-uniformity coefficient of load was 2.0 in the Safety Technical Code for Construction Tool Scaffold (JGJ 202-2010). Based on the analysis results, it was suggested to increase the non-uniformity coefficient of load to 2.35 or decrease the allowable position displacement difference to ensure the safe using of lifting scaffold.
2022, 52(3): 158-163,131.
doi: 10.13204/j.gyjzG21042009
Abstract:
A novel type of sinusoidal corrugated steel-reinforced concrete circular pipe was proposed to present the solution to the electromagnetic shielding problem of ordinary reinforced concrete power pipelines. The segment at the top of circular pipe under bending was selected and studied, and a total of 12 beam specimens were designed and fabricated. Three-point bending tests were performed to acquire the relations between moment and deflection, as well as the failure modes of the beam specimens. It was revealed that the moment resistance of beam specimens decreased as the wavelength and wave height of the encased corrugated sheet increased, and the moment resistance was closely related to the position of the encased corrugated sheet. A fine numerical model accounting for the mechanical properties of encased corrugated sheet and the damage development of concrete was developed by using ABAQUS. The flexural performance of the tested corrugated steel reinforced concrete beams was carefully simulated, and it was shown that the numerically obtained failure modes and moment resistances were in good agreement with the experimental results, thus verifying the accuracy of the developed finite element (FE) model.
A novel type of sinusoidal corrugated steel-reinforced concrete circular pipe was proposed to present the solution to the electromagnetic shielding problem of ordinary reinforced concrete power pipelines. The segment at the top of circular pipe under bending was selected and studied, and a total of 12 beam specimens were designed and fabricated. Three-point bending tests were performed to acquire the relations between moment and deflection, as well as the failure modes of the beam specimens. It was revealed that the moment resistance of beam specimens decreased as the wavelength and wave height of the encased corrugated sheet increased, and the moment resistance was closely related to the position of the encased corrugated sheet. A fine numerical model accounting for the mechanical properties of encased corrugated sheet and the damage development of concrete was developed by using ABAQUS. The flexural performance of the tested corrugated steel reinforced concrete beams was carefully simulated, and it was shown that the numerically obtained failure modes and moment resistances were in good agreement with the experimental results, thus verifying the accuracy of the developed finite element (FE) model.
2022, 52(3): 164-170,226.
doi: 10.13204/j.gyjzG21061808
Abstract:
In order to study the mix proportion and compression size effect of engineered cementitious composites (ECC) under hygrothermal curing environment with average relative humidity of 80% and daytime average temperature of 30 ℃ in spring and summer, material tests on 108 specimens in 2 categories involving variables of fly ash, polyvinyl alahol fiber (PVA) fibers, curing environment, and geometrical dimensions were conducted. Based on the experimental results, favorable mix proportions and size effect coefficients of the ECC under the hygrothermal curing environment were obtained. The results indicated that the compression, shearing, and tensile performance of ECC was determined by the amount of PVA fibers, and the fly ash contributed to the shear strength of ECC, but reduced its tensile strength. Under the hygrothermal curing environment of South China, the ECC mix proportion with 35% fly ash and 1.0% PVC fibers had the most favorable mechanical properties, and the size effect coefficients for cubic and prism strengths of the ECC were fcu70.7∶fcu100∶fcu150=0.93∶1.00∶0.78 and fc70.7∶fc100∶fc150=0.96∶1.00∶0.93, respectively. The temperature and humidity had obvious size effect on the prism and cube specimen with the cross section of 70.7 mm side length.
In order to study the mix proportion and compression size effect of engineered cementitious composites (ECC) under hygrothermal curing environment with average relative humidity of 80% and daytime average temperature of 30 ℃ in spring and summer, material tests on 108 specimens in 2 categories involving variables of fly ash, polyvinyl alahol fiber (PVA) fibers, curing environment, and geometrical dimensions were conducted. Based on the experimental results, favorable mix proportions and size effect coefficients of the ECC under the hygrothermal curing environment were obtained. The results indicated that the compression, shearing, and tensile performance of ECC was determined by the amount of PVA fibers, and the fly ash contributed to the shear strength of ECC, but reduced its tensile strength. Under the hygrothermal curing environment of South China, the ECC mix proportion with 35% fly ash and 1.0% PVC fibers had the most favorable mechanical properties, and the size effect coefficients for cubic and prism strengths of the ECC were fcu70.7∶fcu100∶fcu150=0.93∶1.00∶0.78 and fc70.7∶fc100∶fc150=0.96∶1.00∶0.93, respectively. The temperature and humidity had obvious size effect on the prism and cube specimen with the cross section of 70.7 mm side length.
2022, 52(3): 171-176,215.
doi: 10.13204/j.gyjzG20110912
Abstract:
In order to reduce the drying shrinkage strain of traditional ECC and the shrinkage difference between concrete and ECC, firstly the paper determined the water-binder ratio and sand-rubber ratio, so that the ECC’s dimensional change rate was coordinated with the concrete deformation; secondly, the effects of fly ash content, mineral powder content and PVA fiber content on ECC drying shrinkage rate were studied based on orthogonal method, the drying shrinkage value was further optimized. Finally, the tensile, compression, and bending properties of the ECC were studied to ensure the mechanical properties of structural members. The results showed that the shrinkage strain of ECC increased with the increase of water-binder ratio and sand-rubber ratio, and the effect of water-binder ratio on drying shrinkage was much greater than that of sand-rubber ratio; in addition, the shrinkage value decreased with the increase of fly ash content, mineral powder content and PVA fiber content. Among them, fly ash had the best inhibitory effect on drying shrinkage, followed by mineral powder, and PVA fiber had the smallest effect on it. The compressive strength of the ECC with low drying shrinkage could reach 44.5 MPa, and the tensile and flexural strengths reached 2.5 MPa and 10 MPa respectively, and the ultimate tensile strain was stable more than 3%.
In order to reduce the drying shrinkage strain of traditional ECC and the shrinkage difference between concrete and ECC, firstly the paper determined the water-binder ratio and sand-rubber ratio, so that the ECC’s dimensional change rate was coordinated with the concrete deformation; secondly, the effects of fly ash content, mineral powder content and PVA fiber content on ECC drying shrinkage rate were studied based on orthogonal method, the drying shrinkage value was further optimized. Finally, the tensile, compression, and bending properties of the ECC were studied to ensure the mechanical properties of structural members. The results showed that the shrinkage strain of ECC increased with the increase of water-binder ratio and sand-rubber ratio, and the effect of water-binder ratio on drying shrinkage was much greater than that of sand-rubber ratio; in addition, the shrinkage value decreased with the increase of fly ash content, mineral powder content and PVA fiber content. Among them, fly ash had the best inhibitory effect on drying shrinkage, followed by mineral powder, and PVA fiber had the smallest effect on it. The compressive strength of the ECC with low drying shrinkage could reach 44.5 MPa, and the tensile and flexural strengths reached 2.5 MPa and 10 MPa respectively, and the ultimate tensile strain was stable more than 3%.
2022, 52(3): 177-182.
doi: 10.13204/j.gyjzG21052108
Abstract:
In order to study the influence of slag and aeolian sand on the strength of concrete, a batch of single-mixed slag (replacement ratios from 0% to 30%) was designed to replace cement of equal masses in initial concrete and single-mixed aeolian sand (replacement ratios from 0% to 30%) to substitute river sand of equal masses in initial concrete, and mixed slag (a replacement ratio of 30%) and mixed aeolian sand (replacement ratios from 0% to 30%) in the same time to respectively substitute the equal masses of cement and river sand, and the compressive strength, splitting strength, flexural strength and pull-out tests were conducted to compare the effect of slag and aeolian sand on concrete in different replacement ratios. Scanning electron microscope (SEM) was used to analyze the concrete microstructure. The results showed that when slag and aeolian sand were mixed separately, the effect of aeolian sand on the improvement of the compressive strength and splitting strength of concrete was more significant than that of slag, but with the increase of the replacement ratio of slag or aeolian sand, the flexural strength of concrete decreased. The combined action of slag and aeolian sand could effectively improve the compressive strength, splitting strength of concrete and the bonding strength between concrete and steel bars. When the replacement ratios of slag and aeolian sand were 30%, the mechanical property of concrete was better.
In order to study the influence of slag and aeolian sand on the strength of concrete, a batch of single-mixed slag (replacement ratios from 0% to 30%) was designed to replace cement of equal masses in initial concrete and single-mixed aeolian sand (replacement ratios from 0% to 30%) to substitute river sand of equal masses in initial concrete, and mixed slag (a replacement ratio of 30%) and mixed aeolian sand (replacement ratios from 0% to 30%) in the same time to respectively substitute the equal masses of cement and river sand, and the compressive strength, splitting strength, flexural strength and pull-out tests were conducted to compare the effect of slag and aeolian sand on concrete in different replacement ratios. Scanning electron microscope (SEM) was used to analyze the concrete microstructure. The results showed that when slag and aeolian sand were mixed separately, the effect of aeolian sand on the improvement of the compressive strength and splitting strength of concrete was more significant than that of slag, but with the increase of the replacement ratio of slag or aeolian sand, the flexural strength of concrete decreased. The combined action of slag and aeolian sand could effectively improve the compressive strength, splitting strength of concrete and the bonding strength between concrete and steel bars. When the replacement ratios of slag and aeolian sand were 30%, the mechanical property of concrete was better.
2022, 52(3): 183-190.
doi: 10.13204/j.gyjzG21071908
Abstract:
In order to study the change law of bonding performance between ordinary deformed steel bar and ceramic concrete under the combined action of continuous load and chloride corrosion. The study analyzed the influence of three factors of ceramic concrete strength, salt solution concentration and load holding level through pull-out test, a total of 66 pull-out specimens, and putted forward the calculation formula of ultimate bond strength under the combined action of continuous load and chloride corrosion. It was found that the specimen under the combined action of continuous load and chloride erosion had splitting failure, which was the same as the control specimen, but the debris produced after splitting increased. The effect of load holding level on the ultimate bond strength was different. When the salt solution concentration was 5%~15%, the ultimate bond strength of the specimen with 20% load holding level was higher than that of the specimen without load holding, but when the load holding level was 40%, the ultimate bond strength of the specimen was lower. The fitting result of the proposed calculation formula of ultimate bond strength was good.
In order to study the change law of bonding performance between ordinary deformed steel bar and ceramic concrete under the combined action of continuous load and chloride corrosion. The study analyzed the influence of three factors of ceramic concrete strength, salt solution concentration and load holding level through pull-out test, a total of 66 pull-out specimens, and putted forward the calculation formula of ultimate bond strength under the combined action of continuous load and chloride corrosion. It was found that the specimen under the combined action of continuous load and chloride erosion had splitting failure, which was the same as the control specimen, but the debris produced after splitting increased. The effect of load holding level on the ultimate bond strength was different. When the salt solution concentration was 5%~15%, the ultimate bond strength of the specimen with 20% load holding level was higher than that of the specimen without load holding, but when the load holding level was 40%, the ultimate bond strength of the specimen was lower. The fitting result of the proposed calculation formula of ultimate bond strength was good.
2022, 52(3): 191-199.
doi: 10.13204/j.gyjzG21072305
Abstract:
In order to study the uniaxial compression performance of rubber concrete,9 groups of specimens were prepared by orthogonal design method with rates of water to cementitious materials, rubber replacement ratios, rubber particle sizes and fly ash replacement ratios as the influencing factors, and uniaxial compression tests were conducted. The sensitivity analysis of the mechanical properties such as peak stress, peak strain, elastic moduli, ultimate strain, toughness indexes, brittleness indexes was carried out by the range analysis method. the influence law of the most sensitive factor, namely the replacement ratio of rubber, on the mechanical properties was analyzed, and the dimensionless functional relation between the mechanical properties and the replacement ratio of rubber was obtained. The stress-strain curve model of rubber concrete was established by fitting the test results with the Guo model, Yang model and Saenz model. The results showed that the strength of concrete was reduced with the addition of rubber particles, but the ductility, toughness and energy dissipation capacity of rubber concrete were improved. The proposed stress-strain curve model was in good agreement with the test results and could accurately describe the stress-strain characteristics of rubber concrete under uniaxial compression.
In order to study the uniaxial compression performance of rubber concrete,9 groups of specimens were prepared by orthogonal design method with rates of water to cementitious materials, rubber replacement ratios, rubber particle sizes and fly ash replacement ratios as the influencing factors, and uniaxial compression tests were conducted. The sensitivity analysis of the mechanical properties such as peak stress, peak strain, elastic moduli, ultimate strain, toughness indexes, brittleness indexes was carried out by the range analysis method. the influence law of the most sensitive factor, namely the replacement ratio of rubber, on the mechanical properties was analyzed, and the dimensionless functional relation between the mechanical properties and the replacement ratio of rubber was obtained. The stress-strain curve model of rubber concrete was established by fitting the test results with the Guo model, Yang model and Saenz model. The results showed that the strength of concrete was reduced with the addition of rubber particles, but the ductility, toughness and energy dissipation capacity of rubber concrete were improved. The proposed stress-strain curve model was in good agreement with the test results and could accurately describe the stress-strain characteristics of rubber concrete under uniaxial compression.
2022, 52(3): 200-207.
doi: 10.13204/j.gyjzG21062304
Abstract:
In order to compare the fatigue characteristics of high-strength steel bars with that of HRB400 steel bars, the allowable stress amplitudes of HRB600E and HRB500E steel bars were obtained through stress and strain fatigue tests, and the effects of diameters of steel bars and fatigue loading frequencies on the allowable stress amplitudes were analyzed; the stress-strain cycling properties of high-strength steel bars under constant-amplitude strain fatigue were studied and Coffin-Manson and Hollomon formulas and three-parameter fatigue formulas were established. Energy dissipation toughness was used for the first time to evaluate the capability of steel bars to dissipate seismic energy during strain fatigue (or repeated earthquake action). The test showed that the low cycle fatigue life of strain and cycle toughness of HRB500E steel bars produced by V-N microalloying were better than those of HRB500E steel bars produced by V-N-Nb method; high-strength steel bars were of benefit to improving their fatigue lifes, allowable stress amplitudes and total energy dissipation toughness. The total energy-consuming toughness was related to the strain amplitudes, increasing the strain amplitude decreased the total energy-consuming toughness; the fatigue life of T63E high strength steel bars was longer than that of HRB400 steel bars under the same strain amplitude. Finally, the relation between the total strain amplitude and the loss coefficient of strength or the plastic strain range was established.
In order to compare the fatigue characteristics of high-strength steel bars with that of HRB400 steel bars, the allowable stress amplitudes of HRB600E and HRB500E steel bars were obtained through stress and strain fatigue tests, and the effects of diameters of steel bars and fatigue loading frequencies on the allowable stress amplitudes were analyzed; the stress-strain cycling properties of high-strength steel bars under constant-amplitude strain fatigue were studied and Coffin-Manson and Hollomon formulas and three-parameter fatigue formulas were established. Energy dissipation toughness was used for the first time to evaluate the capability of steel bars to dissipate seismic energy during strain fatigue (or repeated earthquake action). The test showed that the low cycle fatigue life of strain and cycle toughness of HRB500E steel bars produced by V-N microalloying were better than those of HRB500E steel bars produced by V-N-Nb method; high-strength steel bars were of benefit to improving their fatigue lifes, allowable stress amplitudes and total energy dissipation toughness. The total energy-consuming toughness was related to the strain amplitudes, increasing the strain amplitude decreased the total energy-consuming toughness; the fatigue life of T63E high strength steel bars was longer than that of HRB400 steel bars under the same strain amplitude. Finally, the relation between the total strain amplitude and the loss coefficient of strength or the plastic strain range was established.
2022, 52(3): 208-215.
doi: 10.13204/j.gyjzG20101105
Abstract:
Steel structural components that are subjected to alternating loads often have no obvious signs of fatigue failure, which can easily cause huge economic losses and heavy casualties. Therefore, how to effectively improve the fatigue performance of steel and steel structural components and prolong their fatigue life has always been highly valued by scholars at home and abroad.Based on a comprehensive review of the current status and recent advances in fatigue repair and life prolongation techniques for steel structures at home and abroad, the paper focused on the cold spraying technique and its application in fatigue repair and life prolongation of steel structures. The process parameters and cold spraying powder coatings with excellent performance on the surface of steel components can effectively improve the fatigue performance of steel structural components.On the basis of summarizing the existing results, combined with the research results and experience in improving the fatigue performance of steel by cold spraying, it was pointed out that cold spraying technique showed a great application potential in the fatigue repair and life prolongation of steel structures. The combination mechanism of the spray coating and the steel substrate, the cooperative force and deformation behavior of the two, and the fatigue fracture mechanism and other related theories needed to be improved. Exploring the application scenarios and technical system of cold spraying technique suitable for steel structure engineering should be the main development direction in the fields of fatigue repair and life prolongation.
Steel structural components that are subjected to alternating loads often have no obvious signs of fatigue failure, which can easily cause huge economic losses and heavy casualties. Therefore, how to effectively improve the fatigue performance of steel and steel structural components and prolong their fatigue life has always been highly valued by scholars at home and abroad.Based on a comprehensive review of the current status and recent advances in fatigue repair and life prolongation techniques for steel structures at home and abroad, the paper focused on the cold spraying technique and its application in fatigue repair and life prolongation of steel structures. The process parameters and cold spraying powder coatings with excellent performance on the surface of steel components can effectively improve the fatigue performance of steel structural components.On the basis of summarizing the existing results, combined with the research results and experience in improving the fatigue performance of steel by cold spraying, it was pointed out that cold spraying technique showed a great application potential in the fatigue repair and life prolongation of steel structures. The combination mechanism of the spray coating and the steel substrate, the cooperative force and deformation behavior of the two, and the fatigue fracture mechanism and other related theories needed to be improved. Exploring the application scenarios and technical system of cold spraying technique suitable for steel structure engineering should be the main development direction in the fields of fatigue repair and life prolongation.
2022, 52(3): 216-226.
doi: 10.13204/j.gyjzG21062512
Abstract:
In order to study the flexural behavior of concrete beams strengthened by fiber reinforced polymer (FRP) grid and cement substrate, 5 tested specimens were estabilshed finite element model with bond-slip cohesive element. The damage evolution mechanism in the interface between the FRP mesh-cement substrate layer and the RC beam during bending failure was analyzed. Parametric finite element models were established guided by the grid unit reinforcement and the beam reinforcement ratio. An improved calculation model for flexural bearing capacity about FRP grid reinforced RC beams based on the bond-slip cohesive model was proposed, and the correctness and applicability of the calculation model were verified by some references. The research indicated that finite element model established by the bond-slip cohesive model could effectively fit the test process and results. The interface damage between the composite layer and the RC beam appearred from the shear span and developed along the direction of the grid. The unit reinforcement amount and reinforcement ratio had great influence on the bending capacity of RC beam. The improved calculation model was correct and applicable, and could better predict the flexural bearing capacity of reinforced specimens and the meshed-span strain.
In order to study the flexural behavior of concrete beams strengthened by fiber reinforced polymer (FRP) grid and cement substrate, 5 tested specimens were estabilshed finite element model with bond-slip cohesive element. The damage evolution mechanism in the interface between the FRP mesh-cement substrate layer and the RC beam during bending failure was analyzed. Parametric finite element models were established guided by the grid unit reinforcement and the beam reinforcement ratio. An improved calculation model for flexural bearing capacity about FRP grid reinforced RC beams based on the bond-slip cohesive model was proposed, and the correctness and applicability of the calculation model were verified by some references. The research indicated that finite element model established by the bond-slip cohesive model could effectively fit the test process and results. The interface damage between the composite layer and the RC beam appearred from the shear span and developed along the direction of the grid. The unit reinforcement amount and reinforcement ratio had great influence on the bending capacity of RC beam. The improved calculation model was correct and applicable, and could better predict the flexural bearing capacity of reinforced specimens and the meshed-span strain.
2022, 52(3): 227-232,240.
doi: 10.13204/j.gyjzG21031005
Abstract:
The reconstruction and function renewal of old industrial buildings have become one of the key points of urban development at present. Taking the reconstruction of the plant area of North Micro-Electro-Mechanical Intelligent Group Co., Ltd., in Tongzhou District of Beijing as an example, the architectural techniques and ideas of the project were summarized from the perspective of renewal and weaving of functions and image. From the three aspects of layout, buildings and space, the whole park was reorganized. The paper discussed a reconstruction method that could be applicable to old industrial parks, as well as the possibilities for renewal and weaving of industrial buildings.
The reconstruction and function renewal of old industrial buildings have become one of the key points of urban development at present. Taking the reconstruction of the plant area of North Micro-Electro-Mechanical Intelligent Group Co., Ltd., in Tongzhou District of Beijing as an example, the architectural techniques and ideas of the project were summarized from the perspective of renewal and weaving of functions and image. From the three aspects of layout, buildings and space, the whole park was reorganized. The paper discussed a reconstruction method that could be applicable to old industrial parks, as well as the possibilities for renewal and weaving of industrial buildings.
