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2020 Vol. 50, No. 9
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2020, 50(9): 1-7,11.
doi: 10.13204/j.gyjzG20063012
Abstract:
On the basis of studying oversea disposal technology of high level radioactive wastes, the concept of geological disposal of high-level radioactive wastes was conceived in our country. On account of the conditions of repository sites and the features of high-level radioactive wastes, disposal technical schemes for vertical hole disposal, drift disposal, and tunnel disposal respectively in the granite or clay layer were proposed, which could provide reference to geological disposal of high-level radioactive wastes in our country in the future.
On the basis of studying oversea disposal technology of high level radioactive wastes, the concept of geological disposal of high-level radioactive wastes was conceived in our country. On account of the conditions of repository sites and the features of high-level radioactive wastes, disposal technical schemes for vertical hole disposal, drift disposal, and tunnel disposal respectively in the granite or clay layer were proposed, which could provide reference to geological disposal of high-level radioactive wastes in our country in the future.
2020, 50(9): 8-11.
doi: 10.13204/j.gyjzG20063013
Abstract:
Based on the conception of geological disposal for high level radioactive wastes, combined with the geological conditions of Beishan in Gansu Province and the buffer and backfill materials composed of Gaomiaozi bentonite from Inner Mongolia, the design parameter indexes of buffer materials in geological disposal repositories for high-level radioactive wastes were proposed, which could provide technical reference to corresponding experimental research on buffer materials for geological disposal repositories of high-level radioactive wastes in China.
Based on the conception of geological disposal for high level radioactive wastes, combined with the geological conditions of Beishan in Gansu Province and the buffer and backfill materials composed of Gaomiaozi bentonite from Inner Mongolia, the design parameter indexes of buffer materials in geological disposal repositories for high-level radioactive wastes were proposed, which could provide technical reference to corresponding experimental research on buffer materials for geological disposal repositories of high-level radioactive wastes in China.
2020, 50(9): 12-16.
doi: 10.13204/j.gyjzG20063018
Abstract:
As an important part of the engineering barrier system of high-level waste geological disposal repositories, the backfill material in the disposal drifts should have appropriate compressibility to limit the upward expansion of buffer materials in disposal holes. Based on the concept of geological disposal of high-level radioactive wastes in China, the interaction between backfill and buffer materials was researched, by combining the relevant research results on candidate buffer materials (Gaomiaozi bentonite) and backfill materials (bentonite-sand mixtures). Based on theoretical calculations, the effect of densities of backfills in disposal drifts on densities of buffers in disposal holes after expansion was analyzed, and the densities of backfills that satisfied compressible requirements were determined.
As an important part of the engineering barrier system of high-level waste geological disposal repositories, the backfill material in the disposal drifts should have appropriate compressibility to limit the upward expansion of buffer materials in disposal holes. Based on the concept of geological disposal of high-level radioactive wastes in China, the interaction between backfill and buffer materials was researched, by combining the relevant research results on candidate buffer materials (Gaomiaozi bentonite) and backfill materials (bentonite-sand mixtures). Based on theoretical calculations, the effect of densities of backfills in disposal drifts on densities of buffers in disposal holes after expansion was analyzed, and the densities of backfills that satisfied compressible requirements were determined.
2020, 50(9): 17-20.
doi: 10.13204/j.gyjzG20072301
Abstract:
Backfill materials in disposal tunnels are important parts of engineering barrier systems, and the engineering design is closely related to the long-term safety of repositories. Based on investigation of design requirements on backfill materials in Sweden which has advanced geological disposal technology, including backfill material composition, properties of backfill blocks and pellets (water content, geometry, density) and installation schemes. The concept of geological disposal of high-level radioactive wastes in China was put forward, the composition of the backfill material was Gaomiaozi bentonite and sand, the design requirements on backfill blocks including geometric states and dry densities were proposed. The research could provide reference to the related experimental research of backfill materials for geological disposal repositories of high-level radioactive wastes in China.
Backfill materials in disposal tunnels are important parts of engineering barrier systems, and the engineering design is closely related to the long-term safety of repositories. Based on investigation of design requirements on backfill materials in Sweden which has advanced geological disposal technology, including backfill material composition, properties of backfill blocks and pellets (water content, geometry, density) and installation schemes. The concept of geological disposal of high-level radioactive wastes in China was put forward, the composition of the backfill material was Gaomiaozi bentonite and sand, the design requirements on backfill blocks including geometric states and dry densities were proposed. The research could provide reference to the related experimental research of backfill materials for geological disposal repositories of high-level radioactive wastes in China.
2020, 50(9): 21-24,74.
doi: 10.13204/j.gyjzG20072114
Abstract:
Backfill materials in disposal drifts are important engineering barriers in geological disposal repositories of high-level radioactive wastes; a certain installed dry density is required to meet its barrier function. Based on the concept of geological disposal of high-level radioactive wastes in China and the design concept of backfill materials, the sensitivity analysis of factors affecting installed densities of backfill materials by combining the reference design of backfill blocks and pellets was carried out. It was found that block dry densities and filling degree were the dominant factors. Then, combining the design requirements of the installed dry densities for backfills, feasible plans to meet the requirements were proposed on an analysis of 36 possible installation schemes. The study could provide technical reference to related experimental research of backfills in geological disposal repositories of high-level radioactive wastes in China.
Backfill materials in disposal drifts are important engineering barriers in geological disposal repositories of high-level radioactive wastes; a certain installed dry density is required to meet its barrier function. Based on the concept of geological disposal of high-level radioactive wastes in China and the design concept of backfill materials, the sensitivity analysis of factors affecting installed densities of backfill materials by combining the reference design of backfill blocks and pellets was carried out. It was found that block dry densities and filling degree were the dominant factors. Then, combining the design requirements of the installed dry densities for backfills, feasible plans to meet the requirements were proposed on an analysis of 36 possible installation schemes. The study could provide technical reference to related experimental research of backfills in geological disposal repositories of high-level radioactive wastes in China.
2020, 50(9): 25-29,54.
doi: 10.13204/j.gyjzG20063009
Abstract:
The geological disposal of high-level radioactive wastes can realize long-term containment and isolation to radioantive wastes by multi-barrier systems constructed of natural barriers (surrounding rock) and engineering barriers. The buffer materials basically composed of bentonite rich montinorillonie were built up an important engineering barrier, which ought to be of good thermal conductivity, low permeability, stable chemical and favourable mechanical properties, a strong ability to absorb nuclides and so on. They must ensure a certain saturated density in the disposal environment for a long time. The sizes of disposal holes, blocks and containers, the densities and moisture contents of buffer materials significantly influenced on saturated densities of buffer materials. Based on properties of Gaomiaozi bentonite of Inner Mongolia, combined with the conceptual design of high-level radioactive-waste geological disposal and design requirements of buffer materials, parameter influencing factors of saturated densities for buffer materials were analyzed, which could provide reference to the design of buffer materials for geological disposal of high-level radioactive wastes in China.
The geological disposal of high-level radioactive wastes can realize long-term containment and isolation to radioantive wastes by multi-barrier systems constructed of natural barriers (surrounding rock) and engineering barriers. The buffer materials basically composed of bentonite rich montinorillonie were built up an important engineering barrier, which ought to be of good thermal conductivity, low permeability, stable chemical and favourable mechanical properties, a strong ability to absorb nuclides and so on. They must ensure a certain saturated density in the disposal environment for a long time. The sizes of disposal holes, blocks and containers, the densities and moisture contents of buffer materials significantly influenced on saturated densities of buffer materials. Based on properties of Gaomiaozi bentonite of Inner Mongolia, combined with the conceptual design of high-level radioactive-waste geological disposal and design requirements of buffer materials, parameter influencing factors of saturated densities for buffer materials were analyzed, which could provide reference to the design of buffer materials for geological disposal of high-level radioactive wastes in China.
2020, 50(9): 30-33.
doi: 10.13204/j.gyjzG20063008
Abstract:
Based on the function and property requirements of buffer materials in geological repositories of high-level radioactive wastes in Japan, and combined with experimental results of buffer materials, according to the properties of Gaomiaozi bentonite of Inner Mongolia, the influences of buffer material block thicknesses on the dry densities of buffer materials were discussed, which could provide reference to design of buffer materials in geological repositories for high-level radioactive wastes in China.
Based on the function and property requirements of buffer materials in geological repositories of high-level radioactive wastes in Japan, and combined with experimental results of buffer materials, according to the properties of Gaomiaozi bentonite of Inner Mongolia, the influences of buffer material block thicknesses on the dry densities of buffer materials were discussed, which could provide reference to design of buffer materials in geological repositories for high-level radioactive wastes in China.
2020, 50(9): 34-37,33.
doi: 10.13204/j.gyjzG20063015
Abstract:
Buffer materials are important parts of barrier systems in geological disposal of high-level radioactive wastes. Based on the physical properties of MX-80 bentonite, a Swedish buffer material, the design parameters such as permeability coefficients, swelling forces and material composition were analyzed. The saturated densities of buffer materials were taken as the long-term safety evaluation indexes to analyze the main influencing factors (outer clearance widths, densities of blocks and pellets), which could provide reference to design of buffer materials in geological disposal for high-level wastes in China.
Buffer materials are important parts of barrier systems in geological disposal of high-level radioactive wastes. Based on the physical properties of MX-80 bentonite, a Swedish buffer material, the design parameters such as permeability coefficients, swelling forces and material composition were analyzed. The saturated densities of buffer materials were taken as the long-term safety evaluation indexes to analyze the main influencing factors (outer clearance widths, densities of blocks and pellets), which could provide reference to design of buffer materials in geological disposal for high-level wastes in China.
2020, 50(9): 38-41,20.
doi: 10.13204/j.gyjzG20063017
Abstract:
Deep geological disposal of high-level radioactive wastes can effectively contain and isolate radioactive wastes by natural and engineering barriers (including waste containers, disposal containers and buffer materials). Based on the granite disposal site, Gaomiaozi bentonite was used as buffer materials, and FLAC 3D software was used to analyze the barrier system of the disposal repository on large time scale in China. The change thermal rules of the thermal field for the disposal environment with time under the condition of decay and heat release of radioactive wastes were studied, and the impact of buffer materials with different thermal conductivity on the thermal field of the disposal environment was analyzed.
Deep geological disposal of high-level radioactive wastes can effectively contain and isolate radioactive wastes by natural and engineering barriers (including waste containers, disposal containers and buffer materials). Based on the granite disposal site, Gaomiaozi bentonite was used as buffer materials, and FLAC 3D software was used to analyze the barrier system of the disposal repository on large time scale in China. The change thermal rules of the thermal field for the disposal environment with time under the condition of decay and heat release of radioactive wastes were studied, and the impact of buffer materials with different thermal conductivity on the thermal field of the disposal environment was analyzed.
2020, 50(9): 42-48,98.
doi: 10.13204/j.gyjzG20031206
Abstract:
Xipo village in Liulin County is a typical representative of the traditional villages in the gullied terrain area of Western Shanxi Province. The village are in a radial layout. The village is built according to the changes of the mountain situation, forming a unique village pattern and residential building form. Based on the combination of on-the-spot investigation and theoretical method, the paper systematically analyzed the three parts of Xipo village,site selection and layout, overall village construction, courtyard construction and single building construction, from the macro, meso and micro perspectives and summarized the construction wisdom and characteristics of Xipo ancient village under the unique gully terrain conditions, and put forward the protection and development strategies of traditional villages, aiming to provide a new perspective and new methods for the protection and development of traditional villages in gully terrain areas.
Xipo village in Liulin County is a typical representative of the traditional villages in the gullied terrain area of Western Shanxi Province. The village are in a radial layout. The village is built according to the changes of the mountain situation, forming a unique village pattern and residential building form. Based on the combination of on-the-spot investigation and theoretical method, the paper systematically analyzed the three parts of Xipo village,site selection and layout, overall village construction, courtyard construction and single building construction, from the macro, meso and micro perspectives and summarized the construction wisdom and characteristics of Xipo ancient village under the unique gully terrain conditions, and put forward the protection and development strategies of traditional villages, aiming to provide a new perspective and new methods for the protection and development of traditional villages in gully terrain areas.
2020, 50(9): 49-54.
doi: 10.13204/j.gyjzG19082704
Abstract:
The flexural behavior of 4 steel fiber reinforced high-strength concrete beams with HRB600 steel bars was tested with different steel fiber contents and concrete strength grades. At the same time, the failure characteristics, deflection, bearing capacity, longitudinal reinforcement strain and crack width were compared and analyzed, and the calculation methods of ultimate bearing capacity, deflection and crack width were evaluated. The test results showed that the section strain change of steel fiber reinforced concrete beam with HRB600 steel bars conformed to flat section assumption. Steel fiber could effectively improve the bending cracking load and deformability of high-strength concrete beams and limit the generation and development of the bending vertical cracks. With the increase of steel fiber content, the flexural bearing capacity of steel fiber reinforced high-strength concrete beams increased. The current calculation method of CECS 38∶2004 Technical Specification for Fiber Reinforced Concrete Structures was still applicable to the calculation of the ultimate bearing capacity, maximum crack width and deflection of the steel fiber reinforced high-strength concrete beams with HRB600 steel bars.
The flexural behavior of 4 steel fiber reinforced high-strength concrete beams with HRB600 steel bars was tested with different steel fiber contents and concrete strength grades. At the same time, the failure characteristics, deflection, bearing capacity, longitudinal reinforcement strain and crack width were compared and analyzed, and the calculation methods of ultimate bearing capacity, deflection and crack width were evaluated. The test results showed that the section strain change of steel fiber reinforced concrete beam with HRB600 steel bars conformed to flat section assumption. Steel fiber could effectively improve the bending cracking load and deformability of high-strength concrete beams and limit the generation and development of the bending vertical cracks. With the increase of steel fiber content, the flexural bearing capacity of steel fiber reinforced high-strength concrete beams increased. The current calculation method of CECS 38∶2004 Technical Specification for Fiber Reinforced Concrete Structures was still applicable to the calculation of the ultimate bearing capacity, maximum crack width and deflection of the steel fiber reinforced high-strength concrete beams with HRB600 steel bars.
2020, 50(9): 55-61.
doi: 10.13204/j.gyjzG20011508
Abstract:
In order to optimize the joint structure of superimposed slabs and analyze the flexural performance of the joint, three locally strengthened joint construction measures were proposed. Three specimens of the reinforced superimposed slabs were designed and tested under static load. The nonlinear finite element analysis of the specimens was carried out by ABAQUS software and compared with the test results. The results showed that the crack distribution, failure mode and flexural capacity of the superimposed slabs were in good agreement with the test results. Based on the finite element model, the parametric analysis of the flexural bending capacity were conducted on the superimposed slabs with groove joint. The influences of the reinforcement ratio, the thickness of the cast-in-place layer, the depth of the groove and the overlapping length of the joint reinforcement on the bearing capacity of the superimposed slabs were investigated.The results showed that the reinforcement ratio, the thickness of the cast-in-place layer and the depth of the groove had a significant impact on the bearing capacity of the superimposed slabs, and the overlapping length of the joint reinforcement had a impact on the bearing capacity of the superimposed slabs. When the overlapping length was less than 1.4la (1.4la was defined as the anchorage length of tensile bar), the bearing capacity increased with the increase of overlapping length. When the overlapping length was greater than 1.4la, there was little impact on the bearing capacity.
In order to optimize the joint structure of superimposed slabs and analyze the flexural performance of the joint, three locally strengthened joint construction measures were proposed. Three specimens of the reinforced superimposed slabs were designed and tested under static load. The nonlinear finite element analysis of the specimens was carried out by ABAQUS software and compared with the test results. The results showed that the crack distribution, failure mode and flexural capacity of the superimposed slabs were in good agreement with the test results. Based on the finite element model, the parametric analysis of the flexural bending capacity were conducted on the superimposed slabs with groove joint. The influences of the reinforcement ratio, the thickness of the cast-in-place layer, the depth of the groove and the overlapping length of the joint reinforcement on the bearing capacity of the superimposed slabs were investigated.The results showed that the reinforcement ratio, the thickness of the cast-in-place layer and the depth of the groove had a significant impact on the bearing capacity of the superimposed slabs, and the overlapping length of the joint reinforcement had a impact on the bearing capacity of the superimposed slabs. When the overlapping length was less than 1.4la (1.4la was defined as the anchorage length of tensile bar), the bearing capacity increased with the increase of overlapping length. When the overlapping length was greater than 1.4la, there was little impact on the bearing capacity.
2020, 50(9): 62-67.
doi: 10.13204/j.gyjzG19111005
Abstract:
In order to further expand the application range of long-span prestressed double-tees, a prestressed double-tees was designed, it can withstand a live load of 30 kN/m2, and it was applied to an experimental office building project. Through the static load test of full size double-tees, the deformation characteristics, crack development law, bearing capacity of normal section and inclined section of the double-tees were obtained, and the mechanical properties of double-tees could meet the use requirements of heavy-load floor and the feasibility of calculation method was verified. The results showed that the prestressed double-tees had a suitable bearing capacity at middle span section and shear bearing capacity of dapped end, and the crack resistance coefficient and deflection of the component could meet the requirements of relevant codes and design; the truss reinforcement set on the double-tees rib top further enhanced the cooperative effect performance of the cast-in-place surface layer and the precast part. There was no cracking of the cast-in-place layer and the precast part during the test. The reasonable construction measures were proposed, which could effectively avoid the generation of cracks in rib plate top and dapped end in the production and construction process of double-tees, and having the value of practice.
In order to further expand the application range of long-span prestressed double-tees, a prestressed double-tees was designed, it can withstand a live load of 30 kN/m2, and it was applied to an experimental office building project. Through the static load test of full size double-tees, the deformation characteristics, crack development law, bearing capacity of normal section and inclined section of the double-tees were obtained, and the mechanical properties of double-tees could meet the use requirements of heavy-load floor and the feasibility of calculation method was verified. The results showed that the prestressed double-tees had a suitable bearing capacity at middle span section and shear bearing capacity of dapped end, and the crack resistance coefficient and deflection of the component could meet the requirements of relevant codes and design; the truss reinforcement set on the double-tees rib top further enhanced the cooperative effect performance of the cast-in-place surface layer and the precast part. There was no cracking of the cast-in-place layer and the precast part during the test. The reasonable construction measures were proposed, which could effectively avoid the generation of cracks in rib plate top and dapped end in the production and construction process of double-tees, and having the value of practice.
2020, 50(9): 68-74.
doi: 10.13204/j.gyjzG19032703
Abstract:
A high-rise building with shear wall structure has been built to 27 floors above ground, and the actual strength of the shear wall concrete on the ground floor is lower than the design strength. The research used the unsupported shear wall replacement method to strengthen the shear wall. Based on field measured data and ABAQUS simulation, the vertical bearing capacity of the high-rise building shear wall during the unsupported replacement process and the seismic behavior of the shear wall after replacement were analyzed. The measured data and the study of 7 model specimens showed that the shear wall reinforced by segmental replacement method could meet the requirements of the bearing capacity of the shear wall during the construction process; after the reinforcement, there was a stress lag phenomenon in the replacement shear wall and different strength replacement construction of concrete had no significant effect on the stress lag phenomenon; 7 quasi-static simulation tests were performed by using 7 shear lag replacement shear wall model specimens, and the relevant seismic parameters of the one-time pouring shear wall under the original design were compared. With the improvement of the strength of the replacement concrete, the seismic performance of the shear wall reinforced by segmental replacement method was gradually improved, which could meet the original seismic design requirements.
A high-rise building with shear wall structure has been built to 27 floors above ground, and the actual strength of the shear wall concrete on the ground floor is lower than the design strength. The research used the unsupported shear wall replacement method to strengthen the shear wall. Based on field measured data and ABAQUS simulation, the vertical bearing capacity of the high-rise building shear wall during the unsupported replacement process and the seismic behavior of the shear wall after replacement were analyzed. The measured data and the study of 7 model specimens showed that the shear wall reinforced by segmental replacement method could meet the requirements of the bearing capacity of the shear wall during the construction process; after the reinforcement, there was a stress lag phenomenon in the replacement shear wall and different strength replacement construction of concrete had no significant effect on the stress lag phenomenon; 7 quasi-static simulation tests were performed by using 7 shear lag replacement shear wall model specimens, and the relevant seismic parameters of the one-time pouring shear wall under the original design were compared. With the improvement of the strength of the replacement concrete, the seismic performance of the shear wall reinforced by segmental replacement method was gradually improved, which could meet the original seismic design requirements.
2020, 50(9): 75-82.
doi: 10.13204/j.gyjzGYJZ201908010011
Abstract:
The paper presented an experimental study on the seismic behavior of reinforced concrete group silos with column-supported.A shaking table tests under three seismic waves were carried out on a 1×3 group silos model with a scale of 1∶25.The dynamic characteristics,acceleration and displacement responses of column-supported group silos were obtained in different earthquake levels under three storage conditions of empty, semi-storage and full silo.The seismic response and the variation regulation were analyzed under different conditions. The different seismic responses of single silos were revealed in different locations,and the base shear of single silos were acquired. The results indicated that the influence of stored material on dynamic characteristics of group silos was related to the stiffness discrepancy in different directions. The acceleration and displacement responses of single silos at different locations were significantly different, which was associated with the direction of seismic action and storage conditions. The single silo base shear forces at different locations were different.The base shear force at the end location was larger than that at the middle location in the X direction, while it was opposite in the Y direction,and the difference decreased with the increase of the stored material. It was suggested that each single silo in the group should carry out seismic checking calculation according to its position.
The paper presented an experimental study on the seismic behavior of reinforced concrete group silos with column-supported.A shaking table tests under three seismic waves were carried out on a 1×3 group silos model with a scale of 1∶25.The dynamic characteristics,acceleration and displacement responses of column-supported group silos were obtained in different earthquake levels under three storage conditions of empty, semi-storage and full silo.The seismic response and the variation regulation were analyzed under different conditions. The different seismic responses of single silos were revealed in different locations,and the base shear of single silos were acquired. The results indicated that the influence of stored material on dynamic characteristics of group silos was related to the stiffness discrepancy in different directions. The acceleration and displacement responses of single silos at different locations were significantly different, which was associated with the direction of seismic action and storage conditions. The single silo base shear forces at different locations were different.The base shear force at the end location was larger than that at the middle location in the X direction, while it was opposite in the Y direction,and the difference decreased with the increase of the stored material. It was suggested that each single silo in the group should carry out seismic checking calculation according to its position.
2020, 50(9): 83-88,117.
doi: 10.13204/j.gyjzG201906300001
Abstract:
To explore the seismic response and effects of isolation of the rocking self-centering bridge piers, two kinds of bridge piers which are called the high damping rubber pads pier and the reset springs pier were proposed. The shaking table test models of bridge piers were made a 1∶15 similar proportion and the seismic response and effects of isolation of two kinds of bridge piers were analyzed in comparison with traditional railway gravity bridge piers. The test results showed that the maximum values of the acceleration on the top and the stress in the bottom of two kinds of new rocking self-centering bridge piers were remarkably decreased in comparison with traditional railway gravity bridge piers under different seismic intensities, and the damage to bridge piers caused by earthquake was reduced, thus, the new rocking self-centering bridge piers had evident effects of isolation. But at the same time, the horizontal displacement on the top of bridge piers would increase correspondingly and the value of displacement was closely related to the stiffness of the restraint parts. In comparison with the rocking self-centering pier with the self-centering springs, the rocking self-centering pier with high damping rubber pads not only could reduce the acceleration and stress response by lift reaction and energy dissipation, but also could control the values of horizontal displacement on the top of bridge piers. Therefore, it was a reasonable structure form of rocking self-centering bridge piers.
To explore the seismic response and effects of isolation of the rocking self-centering bridge piers, two kinds of bridge piers which are called the high damping rubber pads pier and the reset springs pier were proposed. The shaking table test models of bridge piers were made a 1∶15 similar proportion and the seismic response and effects of isolation of two kinds of bridge piers were analyzed in comparison with traditional railway gravity bridge piers. The test results showed that the maximum values of the acceleration on the top and the stress in the bottom of two kinds of new rocking self-centering bridge piers were remarkably decreased in comparison with traditional railway gravity bridge piers under different seismic intensities, and the damage to bridge piers caused by earthquake was reduced, thus, the new rocking self-centering bridge piers had evident effects of isolation. But at the same time, the horizontal displacement on the top of bridge piers would increase correspondingly and the value of displacement was closely related to the stiffness of the restraint parts. In comparison with the rocking self-centering pier with the self-centering springs, the rocking self-centering pier with high damping rubber pads not only could reduce the acceleration and stress response by lift reaction and energy dissipation, but also could control the values of horizontal displacement on the top of bridge piers. Therefore, it was a reasonable structure form of rocking self-centering bridge piers.
2020, 50(9): 89-93.
doi: 10.13204/j.gyjzG19120207
Abstract:
In order to investigate the shear bearing capacity of inclined cross screws in timber-concrete composite beams with timber board interlayer, mechanical mechanism of inclined cross screws was studied. Mechanical models for single plastic hinge and two plastic hinges in the shear-compression loaded screw were established. Mechanical models of lateral crushing of timber, single plastic hinge and two plastic hinges in the shear-tension loaded screw were established. The analytical model for predicting shear bearing capacity of inclined cross screw in timber-concrete composite beams with interlayer was proposed, and the calculated results were compared with the experimental results. The results showed that the shear bearing capacity of inclined cross screws could be predicted well by using the calculation method.
In order to investigate the shear bearing capacity of inclined cross screws in timber-concrete composite beams with timber board interlayer, mechanical mechanism of inclined cross screws was studied. Mechanical models for single plastic hinge and two plastic hinges in the shear-compression loaded screw were established. Mechanical models of lateral crushing of timber, single plastic hinge and two plastic hinges in the shear-tension loaded screw were established. The analytical model for predicting shear bearing capacity of inclined cross screw in timber-concrete composite beams with interlayer was proposed, and the calculated results were compared with the experimental results. The results showed that the shear bearing capacity of inclined cross screws could be predicted well by using the calculation method.
2020, 50(9): 94-98.
doi: 10.13204/j.gyjzG19111605
Abstract:
A new high performance composite, namely, stainless steel strand reinforced Engineered Cementitious Composite (ECC), which is formed by inserting stainless steel strand into ECC. At present, the research on the stainless steel strand reinforced ECC composite material is still in the initial stage. In this paper, six groups of stainless steel strand reinforced ECC tension specimens were designed and fabricated, and the tension tests was carried out considering the test variables such as ECC tensile strength, reinforcement ratio of stainless steel strands in tension direction and so on. The results showed that as the reinforcement ratio or ECC tensile strength increased, the cracking stress, cracking strain, ultimate stress and ultimate strain of the stainless steel strand reinforced ECC were enhanced, and the increase of ultimate stress and ultimate strain was significantly greater than that of cracking stress and cracking strain. According to the test results, the stress-strain curve of this new composite material of this new composite material was obtained. The research presented in the paper could provide theoretical support for further application of this composite material.
A new high performance composite, namely, stainless steel strand reinforced Engineered Cementitious Composite (ECC), which is formed by inserting stainless steel strand into ECC. At present, the research on the stainless steel strand reinforced ECC composite material is still in the initial stage. In this paper, six groups of stainless steel strand reinforced ECC tension specimens were designed and fabricated, and the tension tests was carried out considering the test variables such as ECC tensile strength, reinforcement ratio of stainless steel strands in tension direction and so on. The results showed that as the reinforcement ratio or ECC tensile strength increased, the cracking stress, cracking strain, ultimate stress and ultimate strain of the stainless steel strand reinforced ECC were enhanced, and the increase of ultimate stress and ultimate strain was significantly greater than that of cracking stress and cracking strain. According to the test results, the stress-strain curve of this new composite material of this new composite material was obtained. The research presented in the paper could provide theoretical support for further application of this composite material.
2020, 50(9): 99-105,167.
doi: 10.13204/j.gyjzG20050903
Abstract:
The problem of concrete shrinkage and cracking seriously endangers the structural safety and normal use of building engineering, and the accurate and rapid prediction of early crack resistance of concrete has become the research focus. In this paper, random forest combined with support vector machine algorithm (RF-SVM) was introduced into the study of early-age cracking resistance of concrete. Taking a project as an example, an index system of early-age cracking resistance of concrete was established by selecting 12 influencing factors based on material and mix ratio, in this paper, the random forest regression algorithm based on importance ranking was used to extract the features of the impact factors, select the optimal feature variable set, and achieve the goal of dimension reduction,at the same time, the factors that should be paid more attention to in the actual project were clarified. Then the parameters of the SVM model were optimized by the method of 10-fold cross-validation, and the selected samples were trained and predicted by the SVM model, and the predicted results were output, and compared it with the SVM model and the artificial neural network model without feature selection, the results showed that the prediction result of RF-SVM was the closest to the measured value and the model had the highest precision. The RF-SVM prediction model proposed in this paper could provide an effective method for rapid prediction of early crack resistance of concrete.
The problem of concrete shrinkage and cracking seriously endangers the structural safety and normal use of building engineering, and the accurate and rapid prediction of early crack resistance of concrete has become the research focus. In this paper, random forest combined with support vector machine algorithm (RF-SVM) was introduced into the study of early-age cracking resistance of concrete. Taking a project as an example, an index system of early-age cracking resistance of concrete was established by selecting 12 influencing factors based on material and mix ratio, in this paper, the random forest regression algorithm based on importance ranking was used to extract the features of the impact factors, select the optimal feature variable set, and achieve the goal of dimension reduction,at the same time, the factors that should be paid more attention to in the actual project were clarified. Then the parameters of the SVM model were optimized by the method of 10-fold cross-validation, and the selected samples were trained and predicted by the SVM model, and the predicted results were output, and compared it with the SVM model and the artificial neural network model without feature selection, the results showed that the prediction result of RF-SVM was the closest to the measured value and the model had the highest precision. The RF-SVM prediction model proposed in this paper could provide an effective method for rapid prediction of early crack resistance of concrete.
2020, 50(9): 106-111.
doi: 10.13204/j.gyjzG20040106
Abstract:
Shenzhen Ping’an Financial Center is a super-high-rise building in China. The pile foundation of the project is rock-socketed end-bearing piles with a super large diameter. Due to the creep and shrinkage of concrete materials, the compression of pile body and the settlement of pile top caused by the creep and shrinkage of concrete should not be ignored. In order to explore the influence of non-load factors on the long-term settlement of super-large diameter piles in this project, the settlement of pile foundation in the whole construction process of this project was analyzed and predicted by using SAP 2000, a finite element software. During the analysis some time-dependent volume varying models of concrete were adopted to reflect the time-varying characteristics of the concrete in the super-large diameter piles. To check the rationality of the calculation results, comparison was made between the calculation results and the measured results. The results showed that it was reasonable and necessary for large diameter end-bearing pile to predict the settlement of pile foundation considering the creep and shrinkage property of concrete. The frequently used models, such as CEB-FIP 90、ACI 209R-92 and GL2000, could give a correct prediction closed to the measuring results.
Shenzhen Ping’an Financial Center is a super-high-rise building in China. The pile foundation of the project is rock-socketed end-bearing piles with a super large diameter. Due to the creep and shrinkage of concrete materials, the compression of pile body and the settlement of pile top caused by the creep and shrinkage of concrete should not be ignored. In order to explore the influence of non-load factors on the long-term settlement of super-large diameter piles in this project, the settlement of pile foundation in the whole construction process of this project was analyzed and predicted by using SAP 2000, a finite element software. During the analysis some time-dependent volume varying models of concrete were adopted to reflect the time-varying characteristics of the concrete in the super-large diameter piles. To check the rationality of the calculation results, comparison was made between the calculation results and the measured results. The results showed that it was reasonable and necessary for large diameter end-bearing pile to predict the settlement of pile foundation considering the creep and shrinkage property of concrete. The frequently used models, such as CEB-FIP 90、ACI 209R-92 and GL2000, could give a correct prediction closed to the measuring results.
2020, 50(9): 112-117.
doi: 10.13204/j.gyjzG201904160007
Abstract:
In order to investigate the mechanic properties of steel tubular scaffold (STC), a nonlinear numerical analysis model of the STC based on the beam-column method considering the second-order effect and the nonlinear semi-rigid connection was proposed. Meanwhile, the efficiency and applicability of the presented method was validated by comparing with the results of the field test for the STCs. Finally, the internal forces and the displacements of the STC varying with some parameters (e.g. span of the vertical poles, story height, horizontal load) was studied with the proposed model. The results showed that the proposed model was of high accuracy, since the results produced by the proposed model were well agreement with that of the field test. Furthermore, the mechanic properties of the STC with small ratio of height to width was not influenced by coupling of the second-order effect and the nonlinear semi-rigid connection, and the mechanic properties of the STC with large ratio of height to width was not affected by the nonlinear semi-rigid connection.
In order to investigate the mechanic properties of steel tubular scaffold (STC), a nonlinear numerical analysis model of the STC based on the beam-column method considering the second-order effect and the nonlinear semi-rigid connection was proposed. Meanwhile, the efficiency and applicability of the presented method was validated by comparing with the results of the field test for the STCs. Finally, the internal forces and the displacements of the STC varying with some parameters (e.g. span of the vertical poles, story height, horizontal load) was studied with the proposed model. The results showed that the proposed model was of high accuracy, since the results produced by the proposed model were well agreement with that of the field test. Furthermore, the mechanic properties of the STC with small ratio of height to width was not influenced by coupling of the second-order effect and the nonlinear semi-rigid connection, and the mechanic properties of the STC with large ratio of height to width was not affected by the nonlinear semi-rigid connection.
2020, 50(9): 118-121,146.
doi: 10.13204/j.gyjzG201904210001
Abstract:
The formwork supporting frame with new pulley-clip style, used in the complex teaching building located in the new campus of Hebei Normal University, was selected as the study object. Based on engineering practice, the axial compression of vertical poles and the pull-out resistance of bottom reinforcing tubes were tested and compared with relevant specifications. The results showed that, it was more reasonable to choose 3.0 kN/m2 as the standard value of construction live load, and the value of 2 kN/m2 provided by Unified Standard for Safety of Scaffold in Construction (GB 51210—2016) was relatively low. By assuring the adapter plug was knocked at least twice during construction, the pull-out resistance of bottom reinforcing tubes could basically meet the requirement of 1.2 kN prescribed by some relevant specifications. However, the pull-out resistance value of 3 kN prescribed by some other relevant specifications, was difficult to achieve, suggesting that these requirements needs a further discussions.
The formwork supporting frame with new pulley-clip style, used in the complex teaching building located in the new campus of Hebei Normal University, was selected as the study object. Based on engineering practice, the axial compression of vertical poles and the pull-out resistance of bottom reinforcing tubes were tested and compared with relevant specifications. The results showed that, it was more reasonable to choose 3.0 kN/m2 as the standard value of construction live load, and the value of 2 kN/m2 provided by Unified Standard for Safety of Scaffold in Construction (GB 51210—2016) was relatively low. By assuring the adapter plug was knocked at least twice during construction, the pull-out resistance of bottom reinforcing tubes could basically meet the requirement of 1.2 kN prescribed by some relevant specifications. However, the pull-out resistance value of 3 kN prescribed by some other relevant specifications, was difficult to achieve, suggesting that these requirements needs a further discussions.
2020, 50(9): 122-127.
doi: 10.13204/j.gyjzGYJZ201908080006
Abstract:
In order to study the constant-amplitude fatigue performance of 8.8 grade high-strength bolts under axial tension-tension condition, 3 static tensile tests and 15 M24 bolts with 35K material were carried out. S-N curves were fitted and the fatigue fracture surfaces of representative specimens were analyzed macroscopically and microscopically. In addition, all the test results were compared with those calculated based on the relevant formula of Standard for Classification of Steel Structures (GB 50017—2017). The conclusions are as follows: The fatigue test data were generally discrete, but all within 95% confidence interval; The S-N curves could basically reflect the fatigue life of specimens under different stress amplitudes; At the root of the screw thread, the stress concentration was especially serious, punctiform fatigue source was easy to expand to form linear fatigue source, the notch effect of the specimen was evident; Comparing the test results with the recommended values of allowable fatigue strength stipulated in the national standards, the corresponding fatigue strength of 2×106 times was 1.61 times of the recommended value.
In order to study the constant-amplitude fatigue performance of 8.8 grade high-strength bolts under axial tension-tension condition, 3 static tensile tests and 15 M24 bolts with 35K material were carried out. S-N curves were fitted and the fatigue fracture surfaces of representative specimens were analyzed macroscopically and microscopically. In addition, all the test results were compared with those calculated based on the relevant formula of Standard for Classification of Steel Structures (GB 50017—2017). The conclusions are as follows: The fatigue test data were generally discrete, but all within 95% confidence interval; The S-N curves could basically reflect the fatigue life of specimens under different stress amplitudes; At the root of the screw thread, the stress concentration was especially serious, punctiform fatigue source was easy to expand to form linear fatigue source, the notch effect of the specimen was evident; Comparing the test results with the recommended values of allowable fatigue strength stipulated in the national standards, the corresponding fatigue strength of 2×106 times was 1.61 times of the recommended value.
2020, 50(9): 128-132.
doi: 10.13204/j.gyjzG20042007
Abstract:
The slag bin is an important storage device in the slag discharge system of thermal power plants. In order to study its fatigue properties, a slag bin in an actual project was taken as an example, and a large-scale finite element software was used to establish a finite element model considering contact. The load conditions were analyzed in detail to determine the loading mode, and the structural stress and displacement of the slag bin were obtained. On this basis, the fatigue life of the slag bin was calculated. The result showed that the cylinder of the encryption rib had the maximum stress which value was 349.5 MPa. The fatigue damage was prone to occur near the ring beam and the encryption rib after 2.495×103 cycles.
The slag bin is an important storage device in the slag discharge system of thermal power plants. In order to study its fatigue properties, a slag bin in an actual project was taken as an example, and a large-scale finite element software was used to establish a finite element model considering contact. The load conditions were analyzed in detail to determine the loading mode, and the structural stress and displacement of the slag bin were obtained. On this basis, the fatigue life of the slag bin was calculated. The result showed that the cylinder of the encryption rib had the maximum stress which value was 349.5 MPa. The fatigue damage was prone to occur near the ring beam and the encryption rib after 2.495×103 cycles.
2020, 50(9): 133-138,155.
doi: 10.13204/j.gyjzG19111107
Abstract:
The behavior of steel silo under seismic forces is different with regular structures. In this paper, through a shake table test of steel silo model, the sine wave, El Centro wave and Taft wave of different maximum accelerations were applied, and the dynamic strains and accelerations of measuring points on silo wall were obtained. According to test results, the stress mode of steel silo with solids was analyzed. Combined with the finite element model, the dynamic pressure of the solids on the silo wall during vibration was fitted. At the end, the distribution of solids pressure to silo wall under seismic action was researched and a simplified distribution for practical application was presented.
The behavior of steel silo under seismic forces is different with regular structures. In this paper, through a shake table test of steel silo model, the sine wave, El Centro wave and Taft wave of different maximum accelerations were applied, and the dynamic strains and accelerations of measuring points on silo wall were obtained. According to test results, the stress mode of steel silo with solids was analyzed. Combined with the finite element model, the dynamic pressure of the solids on the silo wall during vibration was fitted. At the end, the distribution of solids pressure to silo wall under seismic action was researched and a simplified distribution for practical application was presented.
2020, 50(9): 139-146.
doi: 10.13204/j.gyjz201904300010
Abstract:
Creep experiments of two groups of CFT eccentric compression members with eccentricity, concrete strength grade and loading age as parameters were carried out. Then 6 commonly used creep prediction models were compared and analyzed. The results from experiment indicated that with the increase of eccentricity, the maximum creep strain (near load side) of CFT eccentric compression members was larger, and the relationship between eccentricity and creep strain was basically linear. The higher the strength grade of concrete was, the smaller the maximum creep strain (near load side) of eccentrically compressed specimens was. Compared with C50 specimens, the creep strain of C40 specimens with loading age of 14 d increased by 12.2%, 26.0%, 21.7% and 23.7% respectively at 60 d, 120 d, 180 d and 240 d. The earlier the loading age was, the larger the maximum creep strain was. The creep strain of concrete with strength grade of C40 increased by 15.8%, 30.1%, 21.1% and 16.8% respectively on the 14th day compared with that on the 28th day at 60 d, 120 d, 180 d and 240 d. Analytical results indicated that the prediction accuracy of fib MC2010 model, ACI 209R-92 model and CEB-FIP MC90 model was better than that of other prediction models. The prediction accuracy of fib MC2010 model was the best one, the average and standard deviation were 0.992 and 0.282, respectively. The second was ACI 209R-92 model, the two values were 1.102 and 0.381, respectively. The third one was CEB-FIP MC90 model, the two values were 1.167 and 0.327, respectively. According to the results of this paper, it was suggested that, the partial safe prediction model of creep final value could be used for creep calculation of CFT eccentric compression members in the structural design.
Creep experiments of two groups of CFT eccentric compression members with eccentricity, concrete strength grade and loading age as parameters were carried out. Then 6 commonly used creep prediction models were compared and analyzed. The results from experiment indicated that with the increase of eccentricity, the maximum creep strain (near load side) of CFT eccentric compression members was larger, and the relationship between eccentricity and creep strain was basically linear. The higher the strength grade of concrete was, the smaller the maximum creep strain (near load side) of eccentrically compressed specimens was. Compared with C50 specimens, the creep strain of C40 specimens with loading age of 14 d increased by 12.2%, 26.0%, 21.7% and 23.7% respectively at 60 d, 120 d, 180 d and 240 d. The earlier the loading age was, the larger the maximum creep strain was. The creep strain of concrete with strength grade of C40 increased by 15.8%, 30.1%, 21.1% and 16.8% respectively on the 14th day compared with that on the 28th day at 60 d, 120 d, 180 d and 240 d. Analytical results indicated that the prediction accuracy of fib MC2010 model, ACI 209R-92 model and CEB-FIP MC90 model was better than that of other prediction models. The prediction accuracy of fib MC2010 model was the best one, the average and standard deviation were 0.992 and 0.282, respectively. The second was ACI 209R-92 model, the two values were 1.102 and 0.381, respectively. The third one was CEB-FIP MC90 model, the two values were 1.167 and 0.327, respectively. According to the results of this paper, it was suggested that, the partial safe prediction model of creep final value could be used for creep calculation of CFT eccentric compression members in the structural design.
2020, 50(9): 147-155.
doi: 10.13204/j.gyjz201904260011
Abstract:
Double-steel-plate concrete (DSPC) composite wall is increasingly used in high-rise residential buildings, but there is no corresponding fire protection standard. In the paper, autoclaved lightweight concrete plate (ALC plate) and non-expansive fire retardant coatings were used to protect the structure. By using ABAQUS to establish the DSPC composite wall models under different working conditions, this paper simulated the temperature distribution and deformation of the structure and analyzed its fire resistance, which was under the combined action of axial compression with unilateral ISO-834 standard heating curve. It was found that with the increase of fire time, the temperature gradient became smaller and smaller, and the temperature difference value between middle part of concrete and steel plate of fire surface was more than 67% from 30 min to 180 min; increasing the distance between studs and split bolts would increase axial expansion deformation and axial compression deformation of the wall at the beginning of the fire; when the height-thickness ratio was greater than 16, the change of the height-thickness ratio had no obvious effect on the axial expansion displacement value under 180 min; increasing the axial compression ratio would reduce the axial expansion displacement of the wall at the initial stage of fire, and the axial compression deformation would be increased under the same temperature. Using 20 mm ALC board or 10 mm non-expansive fire-retardant coating to protect the composite wall, the temperature of structure could not reach the critical temperature. The results showed that the thickness of the fire protection layer of the composite shear wall could be further optimized.
Double-steel-plate concrete (DSPC) composite wall is increasingly used in high-rise residential buildings, but there is no corresponding fire protection standard. In the paper, autoclaved lightweight concrete plate (ALC plate) and non-expansive fire retardant coatings were used to protect the structure. By using ABAQUS to establish the DSPC composite wall models under different working conditions, this paper simulated the temperature distribution and deformation of the structure and analyzed its fire resistance, which was under the combined action of axial compression with unilateral ISO-834 standard heating curve. It was found that with the increase of fire time, the temperature gradient became smaller and smaller, and the temperature difference value between middle part of concrete and steel plate of fire surface was more than 67% from 30 min to 180 min; increasing the distance between studs and split bolts would increase axial expansion deformation and axial compression deformation of the wall at the beginning of the fire; when the height-thickness ratio was greater than 16, the change of the height-thickness ratio had no obvious effect on the axial expansion displacement value under 180 min; increasing the axial compression ratio would reduce the axial expansion displacement of the wall at the initial stage of fire, and the axial compression deformation would be increased under the same temperature. Using 20 mm ALC board or 10 mm non-expansive fire-retardant coating to protect the composite wall, the temperature of structure could not reach the critical temperature. The results showed that the thickness of the fire protection layer of the composite shear wall could be further optimized.
2020, 50(9): 156-162.
doi: 10.13204/j.gyjzG19112401
Abstract:
In order to study the axial compression performance of prefabricated SRCT shear wall, 11 prefabricated SRCT shear walls and one reinforced concrete shear wall were tested under analysis of numerical simulation. The influences of distance-thickness ratio, steel strength and section of tie-rebar on the axial compression properties of the specimens were analyzed. The analysis results showed that the results of the finite element model could reflect the axial compression properties of SRCT shear wall. Compared with RC shear wall, SRCT shear wall had better bearing capacity and axial stiffness. In the process of stress, crushing of concrete in SRCT shear wall was earlier than yield of steel plate. Reasonable design could remain the tie-rebar in the elastic stage during the loading process.
In order to study the axial compression performance of prefabricated SRCT shear wall, 11 prefabricated SRCT shear walls and one reinforced concrete shear wall were tested under analysis of numerical simulation. The influences of distance-thickness ratio, steel strength and section of tie-rebar on the axial compression properties of the specimens were analyzed. The analysis results showed that the results of the finite element model could reflect the axial compression properties of SRCT shear wall. Compared with RC shear wall, SRCT shear wall had better bearing capacity and axial stiffness. In the process of stress, crushing of concrete in SRCT shear wall was earlier than yield of steel plate. Reasonable design could remain the tie-rebar in the elastic stage during the loading process.
2020, 50(9): 163-167.
doi: 10.13204/j.gyjzG19101105
Abstract:
Taking a new type of light-gauge steel keel fireproof floor slab as the research object, the experimental research on the mechanical properties of four full-scale light-gauge steel keel fireproof floor slab specimens under vertical load was carried out, and the damage characteristics of fireproof slabs were observed. The load-deflection curve and load-strain curve were used to analyze the influencing factors of the bending capacity. The calculation formula of the bending capacity of the light-gauge steel keel fireproof floor slab and the improvement suggestions for the slab design were proposed.
Taking a new type of light-gauge steel keel fireproof floor slab as the research object, the experimental research on the mechanical properties of four full-scale light-gauge steel keel fireproof floor slab specimens under vertical load was carried out, and the damage characteristics of fireproof slabs were observed. The load-deflection curve and load-strain curve were used to analyze the influencing factors of the bending capacity. The calculation formula of the bending capacity of the light-gauge steel keel fireproof floor slab and the improvement suggestions for the slab design were proposed.
2020, 50(9): 168-173.
doi: 10.13204/j.gyjz201908210007
Abstract:
To investigate the bending behavior of reinforced concrete beams reinforced with near-surface-mounted prestressed CFRP rods, a total 5 reinforced specimens and 1 unreinforced specimen were designed for bending test. Two parameters were considered in the test, the inital prestressed level of CFRP rods and longitudinal steel ratio. Three important properties, such as bearing capacity, ductility and energy dissipation capacity of CFRP rods were analyzed in detail and the calculation method of flexural bearing capacity of reinforced specimens was discussed. The results showed that the failure modes of reinforced specimens were mostly ductile failure, and some specimens were brittle failure. With the increase of the initial prestress level of CFRP rods, the ultimate bearing capacity of strengthened specimens increased and the maximum increase was 98%, but the ductility of strengthened specimens was reduced. The main strain of reinforced specimen could conform to stress plain section assumption. With the same longitudinal reinforcement ratio, the energy dissipation capacity of the specimens decreased with the increase of the initial prestress level of the CFRP rods; when the initial prestress level was the same, increasing the longitudinal reinforcement ratio could improve the energy dissipation capacity of the specimens to a certain extent.
To investigate the bending behavior of reinforced concrete beams reinforced with near-surface-mounted prestressed CFRP rods, a total 5 reinforced specimens and 1 unreinforced specimen were designed for bending test. Two parameters were considered in the test, the inital prestressed level of CFRP rods and longitudinal steel ratio. Three important properties, such as bearing capacity, ductility and energy dissipation capacity of CFRP rods were analyzed in detail and the calculation method of flexural bearing capacity of reinforced specimens was discussed. The results showed that the failure modes of reinforced specimens were mostly ductile failure, and some specimens were brittle failure. With the increase of the initial prestress level of CFRP rods, the ultimate bearing capacity of strengthened specimens increased and the maximum increase was 98%, but the ductility of strengthened specimens was reduced. The main strain of reinforced specimen could conform to stress plain section assumption. With the same longitudinal reinforcement ratio, the energy dissipation capacity of the specimens decreased with the increase of the initial prestress level of the CFRP rods; when the initial prestress level was the same, increasing the longitudinal reinforcement ratio could improve the energy dissipation capacity of the specimens to a certain extent.
2020, 50(9): 174-180.
doi: 10.13204/j.gyjzG20010406
Abstract:
Traditional reinforcement maintenance methods are difficult to obtain the full-life cycle monitoring status of the bridge during the reinforcement process as well as the reinforcement effect. Therefore, a method for coupling a CFRP board with a pre-compressed long-range fiber bragg grating (FBG) sensor to make a self-sensing CFRP board was proposed. In order to test the stress and strain measurement accuracy of the fiber grating self-sensing CFRP board, based on the relevant calculation principle of national standard static performance index, the calibration and tension test of light grating sensing performance index in self-sensing CFRP plate were carried out, and the error of sensing characteristic theory and test strain sensitivity were analyzed. The test results showed that the fiber grating in self-sensing CFRP had good sensing performance, its strain reached more than 1.2×10-2, the test strain sensitivity was not less than 1.18 pm/10-6, the hysteresis was not more than 1.52%, the linearity was not more than 3.35%, and the repeatability was not more than 2.29%. The total accuracy was not more than 3.92%, which could meet the actual engineering requirements.
Traditional reinforcement maintenance methods are difficult to obtain the full-life cycle monitoring status of the bridge during the reinforcement process as well as the reinforcement effect. Therefore, a method for coupling a CFRP board with a pre-compressed long-range fiber bragg grating (FBG) sensor to make a self-sensing CFRP board was proposed. In order to test the stress and strain measurement accuracy of the fiber grating self-sensing CFRP board, based on the relevant calculation principle of national standard static performance index, the calibration and tension test of light grating sensing performance index in self-sensing CFRP plate were carried out, and the error of sensing characteristic theory and test strain sensitivity were analyzed. The test results showed that the fiber grating in self-sensing CFRP had good sensing performance, its strain reached more than 1.2×10-2, the test strain sensitivity was not less than 1.18 pm/10-6, the hysteresis was not more than 1.52%, the linearity was not more than 3.35%, and the repeatability was not more than 2.29%. The total accuracy was not more than 3.92%, which could meet the actual engineering requirements.
2020, 50(9): 181-185.
doi: 10.13204/j.gyjzG19122008
Abstract:
The structure form of a project in shenzhen is "frame-support structure with suspension layer", which consists of core tube and six mega suspension frames arranged by asymmetric staggered layers. According to the installation sequence, the finite element software MIDAS was used to simulate the whole construction process and calculate the deformation. The deformation of tower construction was controlled by core tube reverse pre-deflection and outer frame structure pre-lifting. At the same time, according to the comparative analysis of construction simulation, the optimal support unloading sequence was selected to achieve the overall deformation control of the structure. It was found that the deformation value before and after unloading was basically in accordance with the theoretical calculation.
The structure form of a project in shenzhen is "frame-support structure with suspension layer", which consists of core tube and six mega suspension frames arranged by asymmetric staggered layers. According to the installation sequence, the finite element software MIDAS was used to simulate the whole construction process and calculate the deformation. The deformation of tower construction was controlled by core tube reverse pre-deflection and outer frame structure pre-lifting. At the same time, according to the comparative analysis of construction simulation, the optimal support unloading sequence was selected to achieve the overall deformation control of the structure. It was found that the deformation value before and after unloading was basically in accordance with the theoretical calculation.
