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2021 Vol. 51, No. 7
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2021, 51(7): 1-5,24.
doi: 10.13204/j.gyjzG20102911
Abstract:
In view of the urgent need of dependably technical supports and guidance in safety appraisals and further maintenance decisions for immersed tunnels in operation in China, to explore the long-term evolution laws and causes of structural performances for immersed tunnels, an analysis comparison was conducted on investigated data from Waihuan Tunnel in Shanghai involving long-term subsidence, water pressure in gaskets between segment joints,cracks in segments,quantities of water seepage and bare rebars,and thickness of overlaying soil,the main distribution characteristics of damage, evolution laws of structural properties, and causes of common damage were revealed. The results showed that subsidence was significant uneven along Waihuan Tunnel in Shanghai, in which the subsidence in some sections was not steady yet. Water pressure was measured in gaskets between segment joints of being damaged in waterproof, the seasonal variations of water pressure by temperature reflected the expansion and contraction of segment joints. A main chain of the performance deterioration for Waihuan Tunnel in Shanghai was revealed, that was the poor foundation and heavier loads from overlaying soil caused the uneven subsidence and then led to a series of quality issues that were the deformation of the structure, the evolution of cracks, the water seepage, the exposure and corrosion of rebars in series.
In view of the urgent need of dependably technical supports and guidance in safety appraisals and further maintenance decisions for immersed tunnels in operation in China, to explore the long-term evolution laws and causes of structural performances for immersed tunnels, an analysis comparison was conducted on investigated data from Waihuan Tunnel in Shanghai involving long-term subsidence, water pressure in gaskets between segment joints,cracks in segments,quantities of water seepage and bare rebars,and thickness of overlaying soil,the main distribution characteristics of damage, evolution laws of structural properties, and causes of common damage were revealed. The results showed that subsidence was significant uneven along Waihuan Tunnel in Shanghai, in which the subsidence in some sections was not steady yet. Water pressure was measured in gaskets between segment joints of being damaged in waterproof, the seasonal variations of water pressure by temperature reflected the expansion and contraction of segment joints. A main chain of the performance deterioration for Waihuan Tunnel in Shanghai was revealed, that was the poor foundation and heavier loads from overlaying soil caused the uneven subsidence and then led to a series of quality issues that were the deformation of the structure, the evolution of cracks, the water seepage, the exposure and corrosion of rebars in series.
2021, 51(7): 6-10,38.
doi: 10.13204/j.gyjzG20112306
Abstract:
The scour and deposition in deep channel sections of a river bed make the longitudinal loads acting on river-crossing tunnels complicated and affect the longitudinal deformation of tunnels. Based on the river-crossing tunnel project of Nanjing Metro, the longitudinal deformation properties of the shield tunnel caused by different scoured depth and thalweg locations were studied. Firstly, the finite element model was constructed to obtain the longitudinal deformation of the tunnel in different scoured conditions. According to the deformation curve, the curvature radius of the tunnel and the opening widths between joints were calculated. The results showed that:1) The radius of curvature of the tunnel and the maximum opening widths of segment joints were related to the scoured depth and range. The larger the scoured range, the greater the rebound of the tunnel and the smaller the corresponding curvature radius, the larger the opening between segements. 2) The position of the maximum opening width was near the thalweg. 3) In the vicinity of change point for tunnel slopes, the opening widths of segments were obviously larger than that of constant slope sections. Therefore, the locations of changing slope for tunnels should be away from the zones of depth variation for thalwegs in design.
The scour and deposition in deep channel sections of a river bed make the longitudinal loads acting on river-crossing tunnels complicated and affect the longitudinal deformation of tunnels. Based on the river-crossing tunnel project of Nanjing Metro, the longitudinal deformation properties of the shield tunnel caused by different scoured depth and thalweg locations were studied. Firstly, the finite element model was constructed to obtain the longitudinal deformation of the tunnel in different scoured conditions. According to the deformation curve, the curvature radius of the tunnel and the opening widths between joints were calculated. The results showed that:1) The radius of curvature of the tunnel and the maximum opening widths of segment joints were related to the scoured depth and range. The larger the scoured range, the greater the rebound of the tunnel and the smaller the corresponding curvature radius, the larger the opening between segements. 2) The position of the maximum opening width was near the thalweg. 3) In the vicinity of change point for tunnel slopes, the opening widths of segments were obviously larger than that of constant slope sections. Therefore, the locations of changing slope for tunnels should be away from the zones of depth variation for thalwegs in design.
2021, 51(7): 11-17.
doi: 10.13204/j.gyjzG20072217
Abstract:
As a key index to judge the mechanical properties of soil, the relative density is also an important index for the classification of surrounding rock grades. It is of great significance to study the influence on stratum subsidence and stress during tunnelling. Based on the model test platform for shield tunnels developed by Beijing University of Technology, tunnelling tests were conducted in soil with different relative densities, the surface or stratum subsidence and stress during tunnelling were measured systematically. The test results showed that:with the increase of relative densities, the shapes of subsidence troughs for the stratum changed from the distribution shape of Gaussian Function to the triangular shape, the depth and width were smaller and smaller; the subsidence of the surface lagged more behind the process of being tunnelled; the stress paths at the arch crown and arch shoulder became steeper and steeper, that caused the obvious dilation in soils and brought about the above change laws in the shape of the the stratum subsidence troughs. Therefore, in simulations of tunnelling, it was necessary to consider the dilatancy of soil to ensure the rational predications on surface subsidence.
As a key index to judge the mechanical properties of soil, the relative density is also an important index for the classification of surrounding rock grades. It is of great significance to study the influence on stratum subsidence and stress during tunnelling. Based on the model test platform for shield tunnels developed by Beijing University of Technology, tunnelling tests were conducted in soil with different relative densities, the surface or stratum subsidence and stress during tunnelling were measured systematically. The test results showed that:with the increase of relative densities, the shapes of subsidence troughs for the stratum changed from the distribution shape of Gaussian Function to the triangular shape, the depth and width were smaller and smaller; the subsidence of the surface lagged more behind the process of being tunnelled; the stress paths at the arch crown and arch shoulder became steeper and steeper, that caused the obvious dilation in soils and brought about the above change laws in the shape of the the stratum subsidence troughs. Therefore, in simulations of tunnelling, it was necessary to consider the dilatancy of soil to ensure the rational predications on surface subsidence.
2021, 51(7): 18-24.
doi: 10.13204/j.gyjzG20072901
Abstract:
Based on a highway loess tunnel, the uniaxial creep tests of undisturbed Q2 loess in the different moisture content were conducted to explore the creep properties, and the effect of long-term deformation on the evolution laws of surrounding rock pressure and convergence deformation were analyzed by numerical methods, finally, the distribution modes and calculation methods of surrounding rock pressure were put forward. The results showed that:1) in the course of long-term deformation development of loess strata, the surrounding rock pressure and vertical convergence deformation all showed a trend of increase. 10 years later, the surrounding rock pressure would keep it stable, and the distribution form would be in the "cat's ear" shape. The average magnifications of vertical and horizontal surrounding rock pressure were 1.61 and 1.33, the average vertical subsidence of the arch crown was magnified by 1.22 times and horizontal convergence deformation was reduced by 0.97 times respectively;2) with the increase of tunnel embedment, the ratios of surrounding rock pressure and convergence deformation generally increared, and increase of embedment, the magnified effects on stress and deformation were more obvious; 3) the greater the initial moisture content of the loess, the greater the surrounding rock pressure and convergence deformation, but the ratios of them tended to decrease;4)the surrounding rock pressure ratio was introduced into Terzaghi theory and XIE Jiaxiu's formula, the modified formula of surrounding rock pressure were put forward, and the long-term deformation effect of loess strata on the surrounding rock pressure could be considered.
Based on a highway loess tunnel, the uniaxial creep tests of undisturbed Q2 loess in the different moisture content were conducted to explore the creep properties, and the effect of long-term deformation on the evolution laws of surrounding rock pressure and convergence deformation were analyzed by numerical methods, finally, the distribution modes and calculation methods of surrounding rock pressure were put forward. The results showed that:1) in the course of long-term deformation development of loess strata, the surrounding rock pressure and vertical convergence deformation all showed a trend of increase. 10 years later, the surrounding rock pressure would keep it stable, and the distribution form would be in the "cat's ear" shape. The average magnifications of vertical and horizontal surrounding rock pressure were 1.61 and 1.33, the average vertical subsidence of the arch crown was magnified by 1.22 times and horizontal convergence deformation was reduced by 0.97 times respectively;2) with the increase of tunnel embedment, the ratios of surrounding rock pressure and convergence deformation generally increared, and increase of embedment, the magnified effects on stress and deformation were more obvious; 3) the greater the initial moisture content of the loess, the greater the surrounding rock pressure and convergence deformation, but the ratios of them tended to decrease;4)the surrounding rock pressure ratio was introduced into Terzaghi theory and XIE Jiaxiu's formula, the modified formula of surrounding rock pressure were put forward, and the long-term deformation effect of loess strata on the surrounding rock pressure could be considered.
2021, 51(7): 25-30.
doi: 10.13204/j.gyjzG21031806
Abstract:
In the complex geological environment, it is difficult to accurately calculate the water and earth pressure on shield tunnels. Based on the Jinan Metro line R2 as research basis, two representative sections were selected to measure the water and earth pressure on the lining structure, the evolution and distribution characteristics of water and earth pressure on the shield tunnel segments in different geological environments were analyzed. The results showed:1) In soft and hard nonuniform composite strata, due to differences in the physical and mechanical properties between strata, the water and earth pressure on measured sections would gradually kept it stable after being tunnelled about 20 shield segments away. 2) For normal consolidated soft clay or silty clay, when the thickness of the overlaying soil was greater than 2.5D (D was the outer diameter of the segmenting), the soil arching effect had already occurred, and the calculation method for loose earth pressure proposed by Terzaghi was more reasonable. For a tunnel with a thickness of less than 1.5D, the full soil column method was more appropriate.3) In a stratum with softer uppersoil and harder subsoil, the loads on both sides of the shield tunnel were asymmetrical, and the calculation mode of loads by the conventional correction method exaggerated the base reaction. 4) The measured water pressure on the two sections was generally close to the theoretical static water pressure.
In the complex geological environment, it is difficult to accurately calculate the water and earth pressure on shield tunnels. Based on the Jinan Metro line R2 as research basis, two representative sections were selected to measure the water and earth pressure on the lining structure, the evolution and distribution characteristics of water and earth pressure on the shield tunnel segments in different geological environments were analyzed. The results showed:1) In soft and hard nonuniform composite strata, due to differences in the physical and mechanical properties between strata, the water and earth pressure on measured sections would gradually kept it stable after being tunnelled about 20 shield segments away. 2) For normal consolidated soft clay or silty clay, when the thickness of the overlaying soil was greater than 2.5D (D was the outer diameter of the segmenting), the soil arching effect had already occurred, and the calculation method for loose earth pressure proposed by Terzaghi was more reasonable. For a tunnel with a thickness of less than 1.5D, the full soil column method was more appropriate.3) In a stratum with softer uppersoil and harder subsoil, the loads on both sides of the shield tunnel were asymmetrical, and the calculation mode of loads by the conventional correction method exaggerated the base reaction. 4) The measured water pressure on the two sections was generally close to the theoretical static water pressure.
2021, 51(7): 31-38.
doi: 10.13204/j.gyjzG20040307
Abstract:
According to a practical project, a scale model of 1:100 was constructed, the load-bearing characteristics of anti-silde piles and lining structure for tunnels in the tunnel-landslide system with three kinds of pile spacing were studied, the top displacement of anti-slide piles, tunnel displacement, earth pressure on tunnels in landslides were analyzed. The variable regularities of the moment in pile shafts and tunnels subjected to graded loads and the support effect of anti-slide piles with different spacings for the tunnel-landslide system were observed as well. The experimental results showed as the spacing of anti-slide piles was increased from 2.08 times the length of the pile diameter to 4.16 and 6.24 times,the horizontal displacement of pile tops or tunnels, earth pressure on pile shafts or tunnels,and moment in pile shafts and tunnels gradually increased. As pile spacing was increased from 4.16 times the length of the pile diameter to 6.24 times, the increase of displacement and moment was much larger than that of pile spacing increased from 2.08 times the length of the pile diameter to 4.16 times. Thus, if the thrust of landslides was small, the pile spacing could be promoted properly. When the thrust of landslides was large, the pile spacing should be reduced to beneficially ensured the safety of lining structure for tunnels. Whether it was large or small for thrust, the spacing of anti-slide piles with 4.16 times the length of the pile diameter was a high cost-performance choice for tunnel protection.
According to a practical project, a scale model of 1:100 was constructed, the load-bearing characteristics of anti-silde piles and lining structure for tunnels in the tunnel-landslide system with three kinds of pile spacing were studied, the top displacement of anti-slide piles, tunnel displacement, earth pressure on tunnels in landslides were analyzed. The variable regularities of the moment in pile shafts and tunnels subjected to graded loads and the support effect of anti-slide piles with different spacings for the tunnel-landslide system were observed as well. The experimental results showed as the spacing of anti-slide piles was increased from 2.08 times the length of the pile diameter to 4.16 and 6.24 times,the horizontal displacement of pile tops or tunnels, earth pressure on pile shafts or tunnels,and moment in pile shafts and tunnels gradually increased. As pile spacing was increased from 4.16 times the length of the pile diameter to 6.24 times, the increase of displacement and moment was much larger than that of pile spacing increased from 2.08 times the length of the pile diameter to 4.16 times. Thus, if the thrust of landslides was small, the pile spacing could be promoted properly. When the thrust of landslides was large, the pile spacing should be reduced to beneficially ensured the safety of lining structure for tunnels. Whether it was large or small for thrust, the spacing of anti-slide piles with 4.16 times the length of the pile diameter was a high cost-performance choice for tunnel protection.
2021, 51(7): 39-46,63.
doi: 10.13204/j.gyjzG21040603
Abstract:
To study seismic responses of twin tunnels with different lining stiffness, the seismic responses of twin tunnels with different lining stiffness was calculated and analyzed by the wave theory and combined with numerical calculation methods, taking the Leboguolaji tunnel of the Yalu Expressway as the background. The wave scattering theory was used to analyze the series solutions of dynamic stress coefficients for circular linings under the action of plane P-wave. The wave analysis results showed that the dynamic stress coefficient of circular linings for twin tunnels had important relation with the distance between twin tunnels, lining stiffness and P-wave frequency. The smaller the distance between the twin tunnels and the larger the lining stiffness, the larger the dynamic stress coefficient of the twin tunnels linings.The higher the plane P-wave frequency, the smaller the dynamic stress coefficient of the twin tunnel linings. Based on FLAC3D analysis software, the analysis model of numerical seismic responses for twin tunnels in mountains was constructed. The calculation results showed that the seismic responses of the tunnel structure with the rigid lining was significantly higher than that of the flexible lining, which indicated that the flexible lining could weaken the seismic dynamic responses of tunnels and had a certain shock absorption effect, but the seismic displacement of the flexible lining was higher than that of the rigid lining. The numerical results were in good agreements with the wave theory.
To study seismic responses of twin tunnels with different lining stiffness, the seismic responses of twin tunnels with different lining stiffness was calculated and analyzed by the wave theory and combined with numerical calculation methods, taking the Leboguolaji tunnel of the Yalu Expressway as the background. The wave scattering theory was used to analyze the series solutions of dynamic stress coefficients for circular linings under the action of plane P-wave. The wave analysis results showed that the dynamic stress coefficient of circular linings for twin tunnels had important relation with the distance between twin tunnels, lining stiffness and P-wave frequency. The smaller the distance between the twin tunnels and the larger the lining stiffness, the larger the dynamic stress coefficient of the twin tunnels linings.The higher the plane P-wave frequency, the smaller the dynamic stress coefficient of the twin tunnel linings. Based on FLAC3D analysis software, the analysis model of numerical seismic responses for twin tunnels in mountains was constructed. The calculation results showed that the seismic responses of the tunnel structure with the rigid lining was significantly higher than that of the flexible lining, which indicated that the flexible lining could weaken the seismic dynamic responses of tunnels and had a certain shock absorption effect, but the seismic displacement of the flexible lining was higher than that of the rigid lining. The numerical results were in good agreements with the wave theory.
2021, 51(7): 47-56.
doi: 10.13204/j.gyjzG20061104
Abstract:
The full-scale segmental model test and corresponding analysis were conducted on the assembly monolithic concrete utility tunnel with double compartments to obtain its mechanical performances. The results showed that:1) the failure mode for the larger compartment roof was shear failure after yield of longitudinal rebars, while the shear failure was observed in the smaller compartment roof before the ultimate flexural capacity. The shear bearing capacity of the roof with larger thickness for the tunnel was likely to be the control factor in design; 2) the working performance of the bonding interface could be guaranteed if the anchorage of the web rebars of trusses across the bonding interface was reliable; 3) the overlapping structure between U-shaped rebars reserved in the precast parts of walls and the rebars extending into the cast-in-place layer of the roof could meet load-bearing requirement of connections; 4) the structural design of the existing utility tunnel had sufficient safety reserve and good normal service performances.
The full-scale segmental model test and corresponding analysis were conducted on the assembly monolithic concrete utility tunnel with double compartments to obtain its mechanical performances. The results showed that:1) the failure mode for the larger compartment roof was shear failure after yield of longitudinal rebars, while the shear failure was observed in the smaller compartment roof before the ultimate flexural capacity. The shear bearing capacity of the roof with larger thickness for the tunnel was likely to be the control factor in design; 2) the working performance of the bonding interface could be guaranteed if the anchorage of the web rebars of trusses across the bonding interface was reliable; 3) the overlapping structure between U-shaped rebars reserved in the precast parts of walls and the rebars extending into the cast-in-place layer of the roof could meet load-bearing requirement of connections; 4) the structural design of the existing utility tunnel had sufficient safety reserve and good normal service performances.
2021, 51(7): 57-63.
doi: 10.13204/j.gyjzG20071312
Abstract:
The seismic resistance performances of square single utility tunnels-a shallowly buried slender structure, plays an important role in the safety of lifeline projects and the stability of cities. Based on the three-dimensional finite element method, a nonlinear dynamic interaction model of soil and underground utility tunnels was constructed for the prefabricated square utility tunnels with precast plain joints, precast tongue and groove joints and cast-in-place tunnel with expansion joints. First, the modal analysis was conducted to obtain the natural frequency and structural vibration modals of the three kinds of utility tunnels. According to dynamic responses of the three kinds of structure for utility tunnels exicted by non-uniform seismic action, the evolution of stress and displacement, and the failure modes were revealed. Finally, the seismic responses of tunnel joints or expansion joints were emphatically analyzed. By comparing the evolution laws of acceleration and stress for the three kinds of tunnel joints, it was found that the joints were the key parts for earthquake fortification, in which stress concentration was easy to occure and the dynamic responses including displacement and acceleration were different on both ends of joints. Through numerical simulations and comparative analysis, the damage modes and potential safety threats of the three kinds of utility tunnels were obtained.
The seismic resistance performances of square single utility tunnels-a shallowly buried slender structure, plays an important role in the safety of lifeline projects and the stability of cities. Based on the three-dimensional finite element method, a nonlinear dynamic interaction model of soil and underground utility tunnels was constructed for the prefabricated square utility tunnels with precast plain joints, precast tongue and groove joints and cast-in-place tunnel with expansion joints. First, the modal analysis was conducted to obtain the natural frequency and structural vibration modals of the three kinds of utility tunnels. According to dynamic responses of the three kinds of structure for utility tunnels exicted by non-uniform seismic action, the evolution of stress and displacement, and the failure modes were revealed. Finally, the seismic responses of tunnel joints or expansion joints were emphatically analyzed. By comparing the evolution laws of acceleration and stress for the three kinds of tunnel joints, it was found that the joints were the key parts for earthquake fortification, in which stress concentration was easy to occure and the dynamic responses including displacement and acceleration were different on both ends of joints. Through numerical simulations and comparative analysis, the damage modes and potential safety threats of the three kinds of utility tunnels were obtained.
2021, 51(7): 64-70,97.
doi: 10.13204/j.gyjzG20102503
Abstract:
The longitudinal structural performances of the prefabricated cable tunnels in soft soil foundation in the cases of uneven subsidence were analyzed by the finite element mothod, which respectively have plain joints with prestressing tendons and tongue and groove joints with concave-convex faces and with or without prestressed tendons simultaneously. The vertical displacement, dislocation, opening width of joints, the stress and strain of the concrete, and the shearing forces in circumferential joints were analyzed and compared. It was shown that tongue and groove joints with concave-convex faces could improve the shear resistance of circumferential joints, prestressing tendons could improve the flexural resistance of circumferential joints. Both of them could improve the integrity of the prefabricated cable tunnels. But prestressing tension might result in larger opening width, dislocation and principal tensile stress in circumferential joints at tensioned segments. To avoid excessive deformation or local damage at circumferential joints, some design suggestions for prefabricated cable tunnels were proposed.
The longitudinal structural performances of the prefabricated cable tunnels in soft soil foundation in the cases of uneven subsidence were analyzed by the finite element mothod, which respectively have plain joints with prestressing tendons and tongue and groove joints with concave-convex faces and with or without prestressed tendons simultaneously. The vertical displacement, dislocation, opening width of joints, the stress and strain of the concrete, and the shearing forces in circumferential joints were analyzed and compared. It was shown that tongue and groove joints with concave-convex faces could improve the shear resistance of circumferential joints, prestressing tendons could improve the flexural resistance of circumferential joints. Both of them could improve the integrity of the prefabricated cable tunnels. But prestressing tension might result in larger opening width, dislocation and principal tensile stress in circumferential joints at tensioned segments. To avoid excessive deformation or local damage at circumferential joints, some design suggestions for prefabricated cable tunnels were proposed.
2021, 51(7): 71-77,176.
doi: 10.13204/j.gyjzG20071312
Abstract:
In order to reduce seismic impacts on the operation safety of internal pipes in urban utility tunnels, two new types of seismic supports were developed, the finite element models of the traditional rock-tunnel support system and two types of rock-tunnel aseismic support systems were constructed, and the dynamic characteristics of the two systems were numerically simulated. The dynamic time-history analysis was conducted on the rock-tunnel support systems. Results of the numerical simulation indicated that:1) the first ten natural frequencies of the both systems were lower, which made the systems prone to resonance under seismic action and threaten the safety of pipelines; 2) the natural frequencies of systems were not influenced by the types and arrangements of internal supports, thus the support types could be changed according to technical requirements to improve aseismic performances of utility tunnels. Time-history analysis indicated that:compared with the traditional rock-tunnel support system, the maximum stress, acceleration and displacement of pipelines in the aseismic support system A were reduced by 62%, 42% and 52% respectively; while those ones for the aseismic support B reduced by 51%, 31% and 36%. The aseismic performances of the two new types of aseismic supports were significantly better than the traditional.
In order to reduce seismic impacts on the operation safety of internal pipes in urban utility tunnels, two new types of seismic supports were developed, the finite element models of the traditional rock-tunnel support system and two types of rock-tunnel aseismic support systems were constructed, and the dynamic characteristics of the two systems were numerically simulated. The dynamic time-history analysis was conducted on the rock-tunnel support systems. Results of the numerical simulation indicated that:1) the first ten natural frequencies of the both systems were lower, which made the systems prone to resonance under seismic action and threaten the safety of pipelines; 2) the natural frequencies of systems were not influenced by the types and arrangements of internal supports, thus the support types could be changed according to technical requirements to improve aseismic performances of utility tunnels. Time-history analysis indicated that:compared with the traditional rock-tunnel support system, the maximum stress, acceleration and displacement of pipelines in the aseismic support system A were reduced by 62%, 42% and 52% respectively; while those ones for the aseismic support B reduced by 51%, 31% and 36%. The aseismic performances of the two new types of aseismic supports were significantly better than the traditional.
2021, 51(7): 78-83,112.
doi: 10.13204/j.gyjzG20072118
Abstract:
As the important capital of modern China, Beijing witnessed the great impact of western industrial revolution in the late Qing Dynasty, and became one of the cities that started the industrialization process earlier. After the rule of the Qing government, Beiyang government and the government of the Republic of China, Beijing gradually moved towards the industrial civilization from the agricultural era. Modern industrial construction has an important impact on the evolution of Beijing's urban pattern, architectural style and economic structure, forming the industrial architectural style with Beijing's regional characteristics and unique heritage value. On the basis of systematically combing the evolution of the modern Beijing industry, the style characteristics and heritage values of modern industrial buildings in Beijing were analyzed and studied, with a view to further improve the research of value systems for Beijing industrial heritage, and showed the diversified values of the industrial building heritage in Beijing from a more micro perspective.
As the important capital of modern China, Beijing witnessed the great impact of western industrial revolution in the late Qing Dynasty, and became one of the cities that started the industrialization process earlier. After the rule of the Qing government, Beiyang government and the government of the Republic of China, Beijing gradually moved towards the industrial civilization from the agricultural era. Modern industrial construction has an important impact on the evolution of Beijing's urban pattern, architectural style and economic structure, forming the industrial architectural style with Beijing's regional characteristics and unique heritage value. On the basis of systematically combing the evolution of the modern Beijing industry, the style characteristics and heritage values of modern industrial buildings in Beijing were analyzed and studied, with a view to further improve the research of value systems for Beijing industrial heritage, and showed the diversified values of the industrial building heritage in Beijing from a more micro perspective.
2021, 51(7): 84-89,106.
doi: 10.13204/j.gyjzG21012603
Abstract:
The non-Gaussian distribution characteristics of fluctuating wind loads on a long-span curved roof and the determination method for the peak factor of wind loads in the non-Gaussian distribation region were studied by using synchronous pressure measurement of rigid models in the turbulent flow field simulated atmospheric boundary layers. According to wind pressure data under three typical wind directions, the characteristics of mean wind pressure, fluctuating wind pressure, skewness and kurtosis of fluctuating wind loads on roof surfaces were analyzed, the differences between the probability density function of fluctuating wind loads and standard Gauss distribution curves were also compared. It was found that the skewness, kurtosis and probability density function of wind loads under different wind directions deviated from the standard Gaussian distribution, which had significant non-Gaussianity. Thus, the Hermite moment model was used to calculate the peak factor of wind loads for measured points in non-Gaussian region of curved roof, which provided more reasonable reference values of peak factors of wind loads for the complex long-span curved roof compared to the values of Load Code for the Design of Building Structures(GB 50009-2012).
The non-Gaussian distribution characteristics of fluctuating wind loads on a long-span curved roof and the determination method for the peak factor of wind loads in the non-Gaussian distribation region were studied by using synchronous pressure measurement of rigid models in the turbulent flow field simulated atmospheric boundary layers. According to wind pressure data under three typical wind directions, the characteristics of mean wind pressure, fluctuating wind pressure, skewness and kurtosis of fluctuating wind loads on roof surfaces were analyzed, the differences between the probability density function of fluctuating wind loads and standard Gauss distribution curves were also compared. It was found that the skewness, kurtosis and probability density function of wind loads under different wind directions deviated from the standard Gaussian distribution, which had significant non-Gaussianity. Thus, the Hermite moment model was used to calculate the peak factor of wind loads for measured points in non-Gaussian region of curved roof, which provided more reasonable reference values of peak factors of wind loads for the complex long-span curved roof compared to the values of Load Code for the Design of Building Structures(GB 50009-2012).
2021, 51(7): 90-97.
doi: 10.13204/j.gyjzG20081303
Abstract:
A wind load is the control load in the design of long-span space structure and membrane structure. Taking a practical engineering of streamlined membrane structure with a single ridge as an example, based on the Reynolds time averaged equation and shear stress transfer turbulence model (the SST k-ω model), the distribution of wind pressure on the membrane surface was simulated by ANSYS-CFX 14.0. By comparing and analyzing the distribution of wind pressure, the coefficients of mean wind pressure and turbulence characteristics on the membrane surface in different wind directions, the value ranges of the most unfavorable wind directions, the coefficients of mean wind pressure and the shape coefficients of wind load in different zones on the membrane surface were obtained. The study results showed that the most unfavorable wind direction were between 60° and 90° for the structure, and in the wind directions, the turbulence characteristics on the surface of membrane structure were complex and changeable. The eaves in the windward side formed a higher positive pressure, while the roof ridge in the leeward side formed a higher negative pressure, which made the part more easily damage. A large negative pressure area was formed on the ridge of the leeward side, and the obvious vortex was generated in the middle of the structure, which was mainly represented by suction.
A wind load is the control load in the design of long-span space structure and membrane structure. Taking a practical engineering of streamlined membrane structure with a single ridge as an example, based on the Reynolds time averaged equation and shear stress transfer turbulence model (the SST k-ω model), the distribution of wind pressure on the membrane surface was simulated by ANSYS-CFX 14.0. By comparing and analyzing the distribution of wind pressure, the coefficients of mean wind pressure and turbulence characteristics on the membrane surface in different wind directions, the value ranges of the most unfavorable wind directions, the coefficients of mean wind pressure and the shape coefficients of wind load in different zones on the membrane surface were obtained. The study results showed that the most unfavorable wind direction were between 60° and 90° for the structure, and in the wind directions, the turbulence characteristics on the surface of membrane structure were complex and changeable. The eaves in the windward side formed a higher positive pressure, while the roof ridge in the leeward side formed a higher negative pressure, which made the part more easily damage. A large negative pressure area was formed on the ridge of the leeward side, and the obvious vortex was generated in the middle of the structure, which was mainly represented by suction.
2021, 51(7): 98-106.
doi: 10.13204/j.gyjzG20072305
Abstract:
The reinforced concrete (RC) frame structure with energy-dissipative outdoor-wall cladding panels (EDCP) is a new kind of structural system, in which the U-shaped steel dampers (USDs) are used to connect the cladding panels and the frame structure. The USDs can utilize the relative slip between the panels and frame to dissipate seismic energy, and thus enhance the aseismic performance of structure. The USDs and plastic hinges of beams and columns can successively yield and dissipate seismic energy under the action of fortification and rare earthquakes through rational performance-based design, which means that the main structure can remain elastic under earthquakes and low-damage under rare earthquakes, and thus has a satisfactory resilience. An energy equilibrium-based practical seismic design procedure was proposed for such structure based on the previous study, and the procedure was used to design an 8-story RC frame structure with energy-dissipative outdoor-wall cladding panels. Moreover, nonlinear time-history analysis under the action of fortification or rare earthquakes were conducted to verify the aseismic performance of the structure. The results indicated that the structure could achieve the expected performance objectives under the action of different earthquake intensities and the proposed design procedure was reasonable and feasible.
The reinforced concrete (RC) frame structure with energy-dissipative outdoor-wall cladding panels (EDCP) is a new kind of structural system, in which the U-shaped steel dampers (USDs) are used to connect the cladding panels and the frame structure. The USDs can utilize the relative slip between the panels and frame to dissipate seismic energy, and thus enhance the aseismic performance of structure. The USDs and plastic hinges of beams and columns can successively yield and dissipate seismic energy under the action of fortification and rare earthquakes through rational performance-based design, which means that the main structure can remain elastic under earthquakes and low-damage under rare earthquakes, and thus has a satisfactory resilience. An energy equilibrium-based practical seismic design procedure was proposed for such structure based on the previous study, and the procedure was used to design an 8-story RC frame structure with energy-dissipative outdoor-wall cladding panels. Moreover, nonlinear time-history analysis under the action of fortification or rare earthquakes were conducted to verify the aseismic performance of the structure. The results indicated that the structure could achieve the expected performance objectives under the action of different earthquake intensities and the proposed design procedure was reasonable and feasible.
2021, 51(7): 107-112.
doi: 10.13204/j.gyjzG19120306
Abstract:
To understand the bond performances between concrete mixed with rubber and rebars in the freeze-thaw environment, rebars were slotted and then strain gauges were stuck crosswise on the groove surface, finaly, the rebars were closed and embedded in the rubber-concrete cubes. After being subjected to rapid freeze-thaw, the central pull-out tests were conducted to study the effect of rubber content and freeze-thaw cycles on load-slip curves, rebar strain in effective anchorage length and bond stress in effective length. The results showed that the bond-failure process could be divided into five stages:micro slip, internal crack slip, acceleration slip, slip stable development and slip softening. Under the action of freeze-thaw cycles, with the increase of pull-out loads, the strain of rebars at each point in the anchorage length with the different rubber content increased more evenly, which indicated that concrete mixed with rubber had good frost resistance. When the rubber content was not more than 10%, the change of bond performances between concrete and rebars in the freeze-thaw environment was small, and the peak slip reduced about 6% than that of ordinary concrete. With the increase of freeze-thaw cycles, the overall distribution of bond stress of concrete mixed with rubber was more uniform, and the load transfer capacity was good.
To understand the bond performances between concrete mixed with rubber and rebars in the freeze-thaw environment, rebars were slotted and then strain gauges were stuck crosswise on the groove surface, finaly, the rebars were closed and embedded in the rubber-concrete cubes. After being subjected to rapid freeze-thaw, the central pull-out tests were conducted to study the effect of rubber content and freeze-thaw cycles on load-slip curves, rebar strain in effective anchorage length and bond stress in effective length. The results showed that the bond-failure process could be divided into five stages:micro slip, internal crack slip, acceleration slip, slip stable development and slip softening. Under the action of freeze-thaw cycles, with the increase of pull-out loads, the strain of rebars at each point in the anchorage length with the different rubber content increased more evenly, which indicated that concrete mixed with rubber had good frost resistance. When the rubber content was not more than 10%, the change of bond performances between concrete and rebars in the freeze-thaw environment was small, and the peak slip reduced about 6% than that of ordinary concrete. With the increase of freeze-thaw cycles, the overall distribution of bond stress of concrete mixed with rubber was more uniform, and the load transfer capacity was good.
2021, 51(7): 113-122,208.
doi: 10.13204/j.gyjzG2010908
Abstract:
To sutdy the global buckling property of cold-formed thin-walled lipped channel columns with web openings and the calculated method of the overall stability and loading capacity for the compressive columns, based on the effective width method, the tests of axial compression for the cold-formed thin-walled lipped channel columns were conducted, which had different cross sections of webs, circular or rectangular web openings, and opening sizes.There were 6 specimens without openings, 18 specimens with circular openings, and 18 specimens with rectangular openings. The diameters of normalized circular openings were 0.3, 0.5, and 0.7 times web height. The heights of normalized rectangular openings were 0.3, 0.5, and 0.7 times web height. The ratios of length-to-width of rectangular opening were 2. The test results showed that the specimens with smaller ratios of width-to-thickness were prone to flexural-torsional buckling, whlie the specimens with larger ratios of width-to-thickness were controlled by local interaction buckling, distortional and global buckling. The capacity of local buckling increased with the increase of the normalized hole sizes. Compared with the specimens without openings, the ultimate capcity of the specimens with openings decreased slightly.Then the experiments were simulated by finite element software ABAQUS. The simulation results showed good agreement with the test results which indicated the finite element method could analyze the specimens with web openings accurately and feasibly. Furthermore, the formula to predicte the elastic global buckling critical stress was revised based on parameter analysis of specimens with web openings by FEM.
To sutdy the global buckling property of cold-formed thin-walled lipped channel columns with web openings and the calculated method of the overall stability and loading capacity for the compressive columns, based on the effective width method, the tests of axial compression for the cold-formed thin-walled lipped channel columns were conducted, which had different cross sections of webs, circular or rectangular web openings, and opening sizes.There were 6 specimens without openings, 18 specimens with circular openings, and 18 specimens with rectangular openings. The diameters of normalized circular openings were 0.3, 0.5, and 0.7 times web height. The heights of normalized rectangular openings were 0.3, 0.5, and 0.7 times web height. The ratios of length-to-width of rectangular opening were 2. The test results showed that the specimens with smaller ratios of width-to-thickness were prone to flexural-torsional buckling, whlie the specimens with larger ratios of width-to-thickness were controlled by local interaction buckling, distortional and global buckling. The capacity of local buckling increased with the increase of the normalized hole sizes. Compared with the specimens without openings, the ultimate capcity of the specimens with openings decreased slightly.Then the experiments were simulated by finite element software ABAQUS. The simulation results showed good agreement with the test results which indicated the finite element method could analyze the specimens with web openings accurately and feasibly. Furthermore, the formula to predicte the elastic global buckling critical stress was revised based on parameter analysis of specimens with web openings by FEM.
2021, 51(7): 123-128.
doi: 10.13204/j.gyjzG21041302
Abstract:
To evaluate the threat of horizontal surface deformation caused by mining to the safety of transmission lines, a typical 220 kV transmission tower line system was taken as the research object and its finite element model was constructed by ANSYS. Considering the types of horizontal surface deformation, and directions, the change laws of forces in the tower members were analyzed, and the relations of the failure mode of the tower and the earth's surface horizontal deformation were revealed. The results showed that the buckling of the cross braces and horizontal braces in or near the first diaphragm-bracing plane was the main failure sign of the tower subjected to horizontal surface deformation. The directions of the horizontal ground deformation had a significant impact on the failure modes and deformation resistance of the tower. Compared with the horizontal ground deformation along the line or perpendicular to the line, when the horizontal ground deformation occured at an oblique angle to the line, the anti-ground-deformation capacity of the tower was significantly reduced, and the minimum capacity was at an oblique angle of 45 degrees.
To evaluate the threat of horizontal surface deformation caused by mining to the safety of transmission lines, a typical 220 kV transmission tower line system was taken as the research object and its finite element model was constructed by ANSYS. Considering the types of horizontal surface deformation, and directions, the change laws of forces in the tower members were analyzed, and the relations of the failure mode of the tower and the earth's surface horizontal deformation were revealed. The results showed that the buckling of the cross braces and horizontal braces in or near the first diaphragm-bracing plane was the main failure sign of the tower subjected to horizontal surface deformation. The directions of the horizontal ground deformation had a significant impact on the failure modes and deformation resistance of the tower. Compared with the horizontal ground deformation along the line or perpendicular to the line, when the horizontal ground deformation occured at an oblique angle to the line, the anti-ground-deformation capacity of the tower was significantly reduced, and the minimum capacity was at an oblique angle of 45 degrees.
2021, 51(7): 129-136.
doi: 10.13204/j.gyjzG20031003
Abstract:
A new type of connections between square steel tube columns and H-type beams with inner sleeves was proposed. Moving the splice joints of columns above the panel zone provided spaces for installation of high-strength bolts, while ensured the continuity of panel zones. To analyze the mechanical properties of three improved connections by finite element simulation method, a connection structure of the connection was obtained, which was of outstanding mechanical properties. To study the static performances of the new type connections and the parameters influences, finite element models were constructed and the design parameters including the thickness and the length of the inner sleeves and the thickness of end-plates. The results showed that the new type connection had higher initial stiffness and bearing capacity. Plastic hinges appeared at the end of beam when the connection damaged, which met the seismic design principles that were "strong columns and weak beams" and "strong joints and weak members". The parameters including the thickness or the length of the inner sleeve, and the thickness of end-plate have some effects on joint static performances. Based on the results, design values were suggested. A calculating formula of initial stiffness for the new type connection was given by using components method, and the calculated results were in good agreement with the results simulated by the finite element method.
A new type of connections between square steel tube columns and H-type beams with inner sleeves was proposed. Moving the splice joints of columns above the panel zone provided spaces for installation of high-strength bolts, while ensured the continuity of panel zones. To analyze the mechanical properties of three improved connections by finite element simulation method, a connection structure of the connection was obtained, which was of outstanding mechanical properties. To study the static performances of the new type connections and the parameters influences, finite element models were constructed and the design parameters including the thickness and the length of the inner sleeves and the thickness of end-plates. The results showed that the new type connection had higher initial stiffness and bearing capacity. Plastic hinges appeared at the end of beam when the connection damaged, which met the seismic design principles that were "strong columns and weak beams" and "strong joints and weak members". The parameters including the thickness or the length of the inner sleeve, and the thickness of end-plate have some effects on joint static performances. Based on the results, design values were suggested. A calculating formula of initial stiffness for the new type connection was given by using components method, and the calculated results were in good agreement with the results simulated by the finite element method.
2021, 51(7): 137-144.
doi: 10.13204/j.gyjzG20070705
Abstract:
To study the seismic performance of base joints for prefabricated composite steel-concrete columns, three new specimens with different ratios of shear span to effective length were conducted by quasi-static tests. The finite-element software ABAQUS was also used to simulate the specimens. The rationality of the numerical model was verified by comparing the results between the simulations and tests.The ratios of shear span to effective length and cross-section shapes of steel tubes inside the connection module were taken as variables, the influences of different rations of shear span to effective length and cross-section shapes of steel tubes on the aseismic performances of the composite column foundation were analyzed. It was indicated that when the ratios of shear span to effective length increased, the ultimate bearing capasity and energy dissipation capacity of the test tubes with steel tubes specimens PJ and YC inside the connection module were gradually reduced.The ultimate bearing capacity of PJ and YG reduced by 14.59% and 21.87% evenly. Correspondingly, the energy consumption reduced by 27.75% and 36.71% evenly. With the increase of the ratios of shear-span to effective lenghth, the ductility of PJ gradually weakened and stable gradually, while the YJ gradually weakened.The yield bearing capacity, peak bearing capacity and ultimate bearing capacity of the YG all were lower than that of the PJ, but the energy dissipation capacity and ductility had been significantly improved.
To study the seismic performance of base joints for prefabricated composite steel-concrete columns, three new specimens with different ratios of shear span to effective length were conducted by quasi-static tests. The finite-element software ABAQUS was also used to simulate the specimens. The rationality of the numerical model was verified by comparing the results between the simulations and tests.The ratios of shear span to effective length and cross-section shapes of steel tubes inside the connection module were taken as variables, the influences of different rations of shear span to effective length and cross-section shapes of steel tubes on the aseismic performances of the composite column foundation were analyzed. It was indicated that when the ratios of shear span to effective length increased, the ultimate bearing capasity and energy dissipation capacity of the test tubes with steel tubes specimens PJ and YC inside the connection module were gradually reduced.The ultimate bearing capacity of PJ and YG reduced by 14.59% and 21.87% evenly. Correspondingly, the energy consumption reduced by 27.75% and 36.71% evenly. With the increase of the ratios of shear-span to effective lenghth, the ductility of PJ gradually weakened and stable gradually, while the YJ gradually weakened.The yield bearing capacity, peak bearing capacity and ultimate bearing capacity of the YG all were lower than that of the PJ, but the energy dissipation capacity and ductility had been significantly improved.
2021, 51(7): 145-150,202.
doi: 10.13204/j.gyjzG20070402
Abstract:
To improve the performances of shear walls and the assembly degrees, a novel type of prefabricated cold-formed thin-wall steel walls filled with light weight polymer mortar (LPM) was developed. The shear performance test for six shear walls were conducted. The failure modes, load-displacement relations, shear capacity, ductility were studied comprehensively. The influence factors including presence or absence of cement-fiber panels, mortar types, wall thickness, and the layers of steel wire gauze were studied. The test results showed that the panels and mortar types had great effect on the failure modes, shear bearing capacity and ductility of shear walls, the panels on both sides could increase the bearing capacity of shear walls by 74%. The bearing capacity of shear walls filled with cement-based LPM could be 38.4% higher than that of walls filled with gypsum-based LPM. The layers of steel wire gauze had no obvious influence on the shear bearing capacity but had a great influence on the ductility of wall panels.
2021, 51(7): 151-155.
doi: 10.13204/j.gyjzG19112904
Abstract:
Eight kinds of recycled brick concrete(PFRB concrete)with polypropylene fibers were designed, in which the fiber content was different. The mechanical tests were conducted. The influence of the fiber content on the mechanical properties (cube compressive strength, axial compressive strength and splitting tensile strength) was analyzed based on the test data. Relational mathematical expressions between cubic compressive strength and axial compressive strength, and cubic compressive strength and splitting tensile strength were obtained. And the compressive stress-strain curve equation of PFRB concrete were constructed. The research result showed that with the increase of the fiber content, cubic compressive strength, axial compressive strength and splitting tensile strength of PFRB concrete first increased and then decreased, and the peak strength was in fiber content of 0.1%.
Eight kinds of recycled brick concrete(PFRB concrete)with polypropylene fibers were designed, in which the fiber content was different. The mechanical tests were conducted. The influence of the fiber content on the mechanical properties (cube compressive strength, axial compressive strength and splitting tensile strength) was analyzed based on the test data. Relational mathematical expressions between cubic compressive strength and axial compressive strength, and cubic compressive strength and splitting tensile strength were obtained. And the compressive stress-strain curve equation of PFRB concrete were constructed. The research result showed that with the increase of the fiber content, cubic compressive strength, axial compressive strength and splitting tensile strength of PFRB concrete first increased and then decreased, and the peak strength was in fiber content of 0.1%.
RESEARCH ON OPTIMIZATION OF PROPORTIONS FOR HIGHLY DURABLE CONCRETE MIX BASED ON RF-NSGA-Ⅱ ALGORITHM
2021, 51(7): 156-161.
doi: 10.13204/j.gyjzG20070812
Abstract:
The problem of insufficient durability for concrete has always been a serious in the complex environment of high cold areas. It is of great significance to design the proportion of concrete mix to ensure the good working performances and durability of concrete. A RF-NSGA-II algorithm was adopted. The multi-objective model of optimization design for concrete mix was constructed, in which the two important durability indexes of concrete:frost resistance and impermeability were taken as the objectives, so as to achieve high-precision prediction of the relative elastic moduli, chloride ion permeability coefficient and optimal proportion of concrete mix. Firstly, based on the data of in real time concrete material and mix proportions, the prediction models of random forest (RF) for frost resistance and impermeability of concrete was constructed respectively. Then,the regression prediction function was taken as the objective function, and the constraint range of factors for mix proportions was determinal according to Specification for Mix Proportion Design or Ordinary Concrete(JGJ 55-2011) and engineering requirements. Finally,the NSGA-Ⅱ algorithm was used for multi-objective optimization to obtain the optimal mix proportion. The results showed that the prediction model for relative elastic moduli in time and chloride ion permeability coefficients of concrete was very good, the error of φRMSE was 0.04, the coefficient of determination R2 was in time as 0.985. Through optimization, the optimization target value of the proportion concrete mix met the requirements of durability and mechanical tests, which was consistent with the actual situation of the project.
The problem of insufficient durability for concrete has always been a serious in the complex environment of high cold areas. It is of great significance to design the proportion of concrete mix to ensure the good working performances and durability of concrete. A RF-NSGA-II algorithm was adopted. The multi-objective model of optimization design for concrete mix was constructed, in which the two important durability indexes of concrete:frost resistance and impermeability were taken as the objectives, so as to achieve high-precision prediction of the relative elastic moduli, chloride ion permeability coefficient and optimal proportion of concrete mix. Firstly, based on the data of in real time concrete material and mix proportions, the prediction models of random forest (RF) for frost resistance and impermeability of concrete was constructed respectively. Then,the regression prediction function was taken as the objective function, and the constraint range of factors for mix proportions was determinal according to Specification for Mix Proportion Design or Ordinary Concrete(JGJ 55-2011) and engineering requirements. Finally,the NSGA-Ⅱ algorithm was used for multi-objective optimization to obtain the optimal mix proportion. The results showed that the prediction model for relative elastic moduli in time and chloride ion permeability coefficients of concrete was very good, the error of φRMSE was 0.04, the coefficient of determination R2 was in time as 0.985. Through optimization, the optimization target value of the proportion concrete mix met the requirements of durability and mechanical tests, which was consistent with the actual situation of the project.
2021, 51(7): 162-169.
doi: 10.13204/j.gyjzG20052201
Abstract:
According to replacement rates of recycled coarse aggregate (RCA) of 0%, 50%, 100%, the compressive creep tests of recycled course aggreagte concrete were conducted. The creep properties of recycled coarse aggregate concrete (RAC) were studied. The experimental results indicated that both of the basic creep and total creep of RAC increased with the increase of replacement rates of RCA, and the effect of replacement rates on total creep of RAC was bigger than that of basic creep. Based on the experimental results, the interaction mechanism recycled coarse aggregate, the new mortar and old mortar in the creep process of RAC was studied, a creep calculation model reflecting the creep relation of new mortar, old mortar and RAC was introduced,which was the modified Neville creep model, and the creep of old mortar in the basic creep or the total creep process of RAC was calculated by the modified creep model. Based on software ANSYS, a two-dimensional random convex aggregate model of RAC was put forward to verify the reliability of the modified creep model. In addition, the influence of the random distribution of RCA on the creep of RAC was studied by the finite element model. Finally, a creep prediction model was constructed, which could be used to compute the creep of old mortar and RAC, and also reflect the content and properties of the old mortar in RAC based on the modified creep model.
According to replacement rates of recycled coarse aggregate (RCA) of 0%, 50%, 100%, the compressive creep tests of recycled course aggreagte concrete were conducted. The creep properties of recycled coarse aggregate concrete (RAC) were studied. The experimental results indicated that both of the basic creep and total creep of RAC increased with the increase of replacement rates of RCA, and the effect of replacement rates on total creep of RAC was bigger than that of basic creep. Based on the experimental results, the interaction mechanism recycled coarse aggregate, the new mortar and old mortar in the creep process of RAC was studied, a creep calculation model reflecting the creep relation of new mortar, old mortar and RAC was introduced,which was the modified Neville creep model, and the creep of old mortar in the basic creep or the total creep process of RAC was calculated by the modified creep model. Based on software ANSYS, a two-dimensional random convex aggregate model of RAC was put forward to verify the reliability of the modified creep model. In addition, the influence of the random distribution of RCA on the creep of RAC was studied by the finite element model. Finally, a creep prediction model was constructed, which could be used to compute the creep of old mortar and RAC, and also reflect the content and properties of the old mortar in RAC based on the modified creep model.
2021, 51(7): 170-176.
doi: 10.13204/j.gyjzG21011111
Abstract:
The plant-fiber-reinforced alkali-activated-slag cementitious material is a kind of new green building material with a great application prospect. The application of industrial and agricultural wastes such as slag and straw can be not only reduce the cost of construction cost, but also obviously improve the anti-cracking performances of the block masonry. The compressive performance tests were conducted on 60 pieces of block masonry constructed by different fiber-reinforced alkali-activated-slag cementitious material at normal temperature and after high temperature. The test result showed that the strength grades of fiber-reinforced block masonry constructed by plantfiber,polypropylene fiber or microsteel fiber were equivalent to the concrete block masory of MU7.5, MU10 and MU15 at normal temperature respectively. The plant fiber still had a certain toughening effect on masory after being subjected to 800℃. By means of regression analysis, an equation for calculating the compressive strength of plant-fiber-reinforced block masonry after being subjected to high temperature was constructed.
The plant-fiber-reinforced alkali-activated-slag cementitious material is a kind of new green building material with a great application prospect. The application of industrial and agricultural wastes such as slag and straw can be not only reduce the cost of construction cost, but also obviously improve the anti-cracking performances of the block masonry. The compressive performance tests were conducted on 60 pieces of block masonry constructed by different fiber-reinforced alkali-activated-slag cementitious material at normal temperature and after high temperature. The test result showed that the strength grades of fiber-reinforced block masonry constructed by plantfiber,polypropylene fiber or microsteel fiber were equivalent to the concrete block masory of MU7.5, MU10 and MU15 at normal temperature respectively. The plant fiber still had a certain toughening effect on masory after being subjected to 800℃. By means of regression analysis, an equation for calculating the compressive strength of plant-fiber-reinforced block masonry after being subjected to high temperature was constructed.
2021, 51(7): 177-184.
doi: 10.13204/j.gyjzG20052805
Abstract:
In the face of the global energy crisis and environmental deterioration, passive solar buildings have attracted much attention due to their features of low energy consumption, low cost and no pollution. Scholars all over the world have conducted extensive studies on the components and performances of passive solar buildings. Based on the analysis of the research progress and situations of the integrated design on passive solar buildings in the past 20 years, it was found that the framework system of the design for passive solar buildings had been preliminarily formed, and the geographical distribution of passive solar buildings and solar radiation had significant geographic spaces matching characteristics. There was still a certain gap between developing countries and developed countries in terms of research technique. Research on passive solar buildings in China was mainly focused on severe cold areas,cold areas, and hot summer and cold winter areas. Finally, it was suggested that the research on integrated design of passive solar buildings, the areas of research and application should be expanded, and the research on the combination and application for building components should be made profoundly.
In the face of the global energy crisis and environmental deterioration, passive solar buildings have attracted much attention due to their features of low energy consumption, low cost and no pollution. Scholars all over the world have conducted extensive studies on the components and performances of passive solar buildings. Based on the analysis of the research progress and situations of the integrated design on passive solar buildings in the past 20 years, it was found that the framework system of the design for passive solar buildings had been preliminarily formed, and the geographical distribution of passive solar buildings and solar radiation had significant geographic spaces matching characteristics. There was still a certain gap between developing countries and developed countries in terms of research technique. Research on passive solar buildings in China was mainly focused on severe cold areas,cold areas, and hot summer and cold winter areas. Finally, it was suggested that the research on integrated design of passive solar buildings, the areas of research and application should be expanded, and the research on the combination and application for building components should be made profoundly.
2021, 51(7): 185-193.
doi: 10.13204/j.gyjzG19121615
Abstract:
Based on the quasi-static test, the aseismic properties of earthquake-damaged joints for assembled monolithic concrete frames strengthened with carbon fiber sheets were studied. The effects of failure modes, hysteretic curves, skeleton curves, displacement, ductility, degradation of stiffness and bearing capacity, and damage degrees on the aseismic performances of specimens reinforced by carbon fiber sheets were analyzed. On the basis of finite element simulations, the influence of different parameters on the strengthening effect, the formula for shear capacity of the core areas for reinforced joints was constructed.The results showed that the ultimate bearing capacity of joints strengthened with CFRP sheets could increase by 27.1% at most, the ultimate displacement could increase by at most 23.8%, the energy dissipation and ductility were enhanced, and the degradation of stiffness and bearing capacity for specimens were slowed down. The aseismic performances of the slightly damaged joints strengthened by CFRP sheets had been effectively improved, the moderately damaged joints of being strengthing had not been improved, but it could still be restored to the undamaged state.The shear capacity of the core area calcuatied by the theoretical formula were compared with that in tests and simulations, the errors were less than 10%.
Based on the quasi-static test, the aseismic properties of earthquake-damaged joints for assembled monolithic concrete frames strengthened with carbon fiber sheets were studied. The effects of failure modes, hysteretic curves, skeleton curves, displacement, ductility, degradation of stiffness and bearing capacity, and damage degrees on the aseismic performances of specimens reinforced by carbon fiber sheets were analyzed. On the basis of finite element simulations, the influence of different parameters on the strengthening effect, the formula for shear capacity of the core areas for reinforced joints was constructed.The results showed that the ultimate bearing capacity of joints strengthened with CFRP sheets could increase by 27.1% at most, the ultimate displacement could increase by at most 23.8%, the energy dissipation and ductility were enhanced, and the degradation of stiffness and bearing capacity for specimens were slowed down. The aseismic performances of the slightly damaged joints strengthened by CFRP sheets had been effectively improved, the moderately damaged joints of being strengthing had not been improved, but it could still be restored to the undamaged state.The shear capacity of the core area calcuatied by the theoretical formula were compared with that in tests and simulations, the errors were less than 10%.
2021, 51(7): 194-202.
doi: 10.13204/j.gyjzG20070105
Abstract:
The glass fiber reinforced polymer (GFRP) circular members have been extensively applied in power engineering because of its good insulation performance. A finite element model reflecting the anisotropy of GFRP fiber sheets was constructed for GFRP pipes by filament winding at alternate angles of 0°,90°,0°,90° and 0° from inside to outside. The Hashin failure criterion and Matzenmiller-Lapczyk's damage evolution model were used in the numerical simulations for pipes subjected to axial compression. The evolution rules of damage and stress were revealed. The mechanical properties reflected in the simulation were in agreement with that of tests, which indicated that the numerical simulation method was capable of reflecting the mechanical characteristics of the GFRP pipes of the filament winding method.
The glass fiber reinforced polymer (GFRP) circular members have been extensively applied in power engineering because of its good insulation performance. A finite element model reflecting the anisotropy of GFRP fiber sheets was constructed for GFRP pipes by filament winding at alternate angles of 0°,90°,0°,90° and 0° from inside to outside. The Hashin failure criterion and Matzenmiller-Lapczyk's damage evolution model were used in the numerical simulations for pipes subjected to axial compression. The evolution rules of damage and stress were revealed. The mechanical properties reflected in the simulation were in agreement with that of tests, which indicated that the numerical simulation method was capable of reflecting the mechanical characteristics of the GFRP pipes of the filament winding method.
2021, 51(7): 203-208.
doi: 10.13204/j.gyjzG20092308
Abstract:
The Kiewitt (K6) spherical reticulated shell was used as the research object to study the data-driven damage prediction and assessment of the space frame structure. By numerical simulations, Structural Health Monitoring (SHM) simulation data of structural modal frequency subjected to uniform atmospheric corrosion were obtained. A Long-Short-Term Memory (LSTM) based the deep learning model for structural damage prediction and assessment was constructed. Finally, the LSTM-based damage prediction and assessment method for the space frame structure was summarized. The results showed that LSTM could be used to establish a data-driven deep learning model for SHM data, predict and assess the structural health status. The model performed well on the simulation data with good anti-noise properties which could nicely fit SHM simulation data with a good short-term prediction effect. The updated data sets could readjust the model, so as to achieve the continuous prediction and assessment for structural health status.
The Kiewitt (K6) spherical reticulated shell was used as the research object to study the data-driven damage prediction and assessment of the space frame structure. By numerical simulations, Structural Health Monitoring (SHM) simulation data of structural modal frequency subjected to uniform atmospheric corrosion were obtained. A Long-Short-Term Memory (LSTM) based the deep learning model for structural damage prediction and assessment was constructed. Finally, the LSTM-based damage prediction and assessment method for the space frame structure was summarized. The results showed that LSTM could be used to establish a data-driven deep learning model for SHM data, predict and assess the structural health status. The model performed well on the simulation data with good anti-noise properties which could nicely fit SHM simulation data with a good short-term prediction effect. The updated data sets could readjust the model, so as to achieve the continuous prediction and assessment for structural health status.
2021, 51(7): 209-215,56.
doi: 10.13204/j.gyjzG20090207
Abstract:
In the industrial age, a large number of railway transportation networks were formed in Paris urban area. Under the background of industrial recession and urban regeneration, the urban abandoned railways and areas along railways have become potential resources for renewal in the high-density city environment of Paris. Nowadays, many urban waste railways facilities, and areas along railways in Paris have been transformed into public activity spaces and landscapes, such as trails, shared gardens, art spaces, which have become important destinations for public life and sightseeing and played a positive role in the construction of urban green network. The evolution and revitalization characteristics of the Vincennes Railway Line and small ring railway in Paris were interpreted in terms of the histories, renewal processes, regeneration methods and post-renewal values. The regeneration model of multi-participation and spontaneous regeneration, as well as the multiple regeneration approaches such as implanting multiculturalism, maintaining existing habitats and shaping public lifes, and the post-renewal values in terms of historical memory continuation, cultural image shaping, quality of life improvement, the urban ecological restoration, regional economic development, etc. were summarized. The corresponding thoughts and suggestions were proposed from the aspects of regeneration methods, operation modes and sustainable development.
In the industrial age, a large number of railway transportation networks were formed in Paris urban area. Under the background of industrial recession and urban regeneration, the urban abandoned railways and areas along railways have become potential resources for renewal in the high-density city environment of Paris. Nowadays, many urban waste railways facilities, and areas along railways in Paris have been transformed into public activity spaces and landscapes, such as trails, shared gardens, art spaces, which have become important destinations for public life and sightseeing and played a positive role in the construction of urban green network. The evolution and revitalization characteristics of the Vincennes Railway Line and small ring railway in Paris were interpreted in terms of the histories, renewal processes, regeneration methods and post-renewal values. The regeneration model of multi-participation and spontaneous regeneration, as well as the multiple regeneration approaches such as implanting multiculturalism, maintaining existing habitats and shaping public lifes, and the post-renewal values in terms of historical memory continuation, cultural image shaping, quality of life improvement, the urban ecological restoration, regional economic development, etc. were summarized. The corresponding thoughts and suggestions were proposed from the aspects of regeneration methods, operation modes and sustainable development.
