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2021 Vol. 51, No. 1
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2021, 51(1): 1-7.
doi: 10.13204/j.gyjzG20072201
Abstract:
Dzong is a special type of traditional architecture in the Tibetan culture area. Its main characteristics are of both military defense and administrative management functions. From the perspective of military defense, the systematical defensive design of Tibetan Dzongs in terms of the site selection, functional layout, defense construction and traffic organization was analyzed, and the military defensive design characteristics were expounded from three aspects: the hierarchical spatial layout, vertical spatial structure and transportation system for peacetime and wartime. Furthermore, the specific role and effect of the military defensive design for Tibetan Dzongs in actual wars were illustrated by a case analysis on the military campaign of fighting against British Army invasion the Gyantse Dzong. Finally, the military defensive design concept of Tibetan Dzongs and its significance to heritage protection were summarized.
Dzong is a special type of traditional architecture in the Tibetan culture area. Its main characteristics are of both military defense and administrative management functions. From the perspective of military defense, the systematical defensive design of Tibetan Dzongs in terms of the site selection, functional layout, defense construction and traffic organization was analyzed, and the military defensive design characteristics were expounded from three aspects: the hierarchical spatial layout, vertical spatial structure and transportation system for peacetime and wartime. Furthermore, the specific role and effect of the military defensive design for Tibetan Dzongs in actual wars were illustrated by a case analysis on the military campaign of fighting against British Army invasion the Gyantse Dzong. Finally, the military defensive design concept of Tibetan Dzongs and its significance to heritage protection were summarized.
2021, 51(1): 8-16,23.
doi: 10.13204/j.gyjzG20033108
Abstract:
Minshenglu Matou, formerly known as the Blue Funnel Wharf which built by British Butterfield & Swire in 1908, was designated as Shanghai historical and cultural sites under government protection in 2014. In recent years, to develop, utilize, preserve and renovate Minshenglu Matou better, scheme design and function adjustment of multi rounds have been conducted. From the perspective of value interpretation, the historical evolution process of Minshenglu Matou was clarified, the industrial and architectural characteristics as a wharf were extracted, the historical, technological, architectural, landscaped, emotional and other values as industrial heritage were refined, and same suggestions for conservation and utilization, interpretation and presentation were put forward, which could provide reference to the value interpretation of other industrial heritage.
Minshenglu Matou, formerly known as the Blue Funnel Wharf which built by British Butterfield & Swire in 1908, was designated as Shanghai historical and cultural sites under government protection in 2014. In recent years, to develop, utilize, preserve and renovate Minshenglu Matou better, scheme design and function adjustment of multi rounds have been conducted. From the perspective of value interpretation, the historical evolution process of Minshenglu Matou was clarified, the industrial and architectural characteristics as a wharf were extracted, the historical, technological, architectural, landscaped, emotional and other values as industrial heritage were refined, and same suggestions for conservation and utilization, interpretation and presentation were put forward, which could provide reference to the value interpretation of other industrial heritage.
2021, 51(1): 17-23.
doi: 10.13204/j.gyjzG20072704
Abstract:
In the past century, higher education and campus construction have made great progress in China. University campuses and campus buildings, because of their great values in history, culture, and resources, have attracted more and more attention. However, in many cases, there are common problems in existing buildings such as single space forms and pooy adaptability due to construction for specific functions, which can not meet the increasingly diverse needs of eduction and research. Based on long-term effective optimization perspective of campus buildings, taking the southwest building in Gulou Campus of Nanjing University as an example, optimal design of campus buildings was studied in the light of systematic investigation. According to study of optimal design for which the structure system & space layout of existing buildings, as well as optimization and sorting of the relation between "fixed" space and "changeable" space, the long-term effective optimal design of existing campus buildings was realized, with great improvement in the adaptability of buildings, offered campus buildings opportunities to meet not only current needs of faculties and students but also the change of their needs in the future.
In the past century, higher education and campus construction have made great progress in China. University campuses and campus buildings, because of their great values in history, culture, and resources, have attracted more and more attention. However, in many cases, there are common problems in existing buildings such as single space forms and pooy adaptability due to construction for specific functions, which can not meet the increasingly diverse needs of eduction and research. Based on long-term effective optimization perspective of campus buildings, taking the southwest building in Gulou Campus of Nanjing University as an example, optimal design of campus buildings was studied in the light of systematic investigation. According to study of optimal design for which the structure system & space layout of existing buildings, as well as optimization and sorting of the relation between "fixed" space and "changeable" space, the long-term effective optimal design of existing campus buildings was realized, with great improvement in the adaptability of buildings, offered campus buildings opportunities to meet not only current needs of faculties and students but also the change of their needs in the future.
2021, 51(1): 24-29.
doi: 10.13204/j.gyjzG20011801
Abstract:
As a living fossil of Chinese agricultural history and culture, traditional villages are sites to carry the social attributes such as people’s living and breeding in the period of agricultural society. Because of the powerful analysis functions of GIS on the geographic information data in traditional villages, the application research of GIS on traditional villages has made scientific research have higher academic values.Combining with the gradually focused on the research results showed with the development of the application of GIS, the discussion humanistic spirit cores of traditional villages based on humanism, by which the scientific sustainable development access of traditional villages in our countries was explored. The statistical analysis and literature analysis methods,based on the analysis of GIS application data on traditional villages from CNKI.
As a living fossil of Chinese agricultural history and culture, traditional villages are sites to carry the social attributes such as people’s living and breeding in the period of agricultural society. Because of the powerful analysis functions of GIS on the geographic information data in traditional villages, the application research of GIS on traditional villages has made scientific research have higher academic values.Combining with the gradually focused on the research results showed with the development of the application of GIS, the discussion humanistic spirit cores of traditional villages based on humanism, by which the scientific sustainable development access of traditional villages in our countries was explored. The statistical analysis and literature analysis methods,based on the analysis of GIS application data on traditional villages from CNKI.
2021, 51(1): 30-36,72.
doi: 10.13204/j.gyjzG19121807
Abstract:
In order to study the flexural properties for segmental pracast girders of prestressed ultra-high performance concrete (HHPC), 5 test girders were completed, and the study parameters were mainly with or without joints, tenon forms and compressive prestress of UHPC. The failure modes, stress increments of steel strands in the tensive zones, load-deflection curves and strain development laws of the test girders were obtained. The test results showed that all the test girders presented typical flexural failure, and the UHPC in the compression zone was crushed. In the damage case, the maximum compressive strain at the compression edge could reach more than 7.2×10-3, and the strain along the section height basically met the plane-section assumption and had nothing to do with the joints. Moreover, different from the cracking characteristics of integal casting girders, the cracks of the segmental precast girders mainly occured in the joint. The UHPC girders had good ductility, and segmental precast girders had better ductility than integal casting girders. The prestress influenced the cracking load of the girders but it had little effect on the ultimate load. The flexural capacity of the precast girders were 9% to 15% lower than that of the integal casting girders subjeted to the same compressive prestress, and the forms of joints also influenced the flexural bearing capacity. The bearing capacity of girders with multi-tenon joints was 4.5% lower than that with the single-tenon joint, and the bearing capacity of the flat-tenon members was 5.7% lower than that with the multi-tenon joint. Based on the experimental analysis, it was found that the reduction factor for joints proposed by the AASHTO specification for segmental girder design was basically suitable for the UHPC precast segmental girders, but the reduction coefficient should further considered the type of joint.
In order to study the flexural properties for segmental pracast girders of prestressed ultra-high performance concrete (HHPC), 5 test girders were completed, and the study parameters were mainly with or without joints, tenon forms and compressive prestress of UHPC. The failure modes, stress increments of steel strands in the tensive zones, load-deflection curves and strain development laws of the test girders were obtained. The test results showed that all the test girders presented typical flexural failure, and the UHPC in the compression zone was crushed. In the damage case, the maximum compressive strain at the compression edge could reach more than 7.2×10-3, and the strain along the section height basically met the plane-section assumption and had nothing to do with the joints. Moreover, different from the cracking characteristics of integal casting girders, the cracks of the segmental precast girders mainly occured in the joint. The UHPC girders had good ductility, and segmental precast girders had better ductility than integal casting girders. The prestress influenced the cracking load of the girders but it had little effect on the ultimate load. The flexural capacity of the precast girders were 9% to 15% lower than that of the integal casting girders subjeted to the same compressive prestress, and the forms of joints also influenced the flexural bearing capacity. The bearing capacity of girders with multi-tenon joints was 4.5% lower than that with the single-tenon joint, and the bearing capacity of the flat-tenon members was 5.7% lower than that with the multi-tenon joint. Based on the experimental analysis, it was found that the reduction factor for joints proposed by the AASHTO specification for segmental girder design was basically suitable for the UHPC precast segmental girders, but the reduction coefficient should further considered the type of joint.
2021, 51(1): 37-44,80.
doi: 10.13204/j.gyjzG20033010
Abstract:
The tests were conducted on three reinforced concrete-filled steel square tubular columns with tie bars, which included one axial compressive test for S-1 and two pseudo-static tests for S-2 and S-3. The bearing capacity, failure modes, failure paths, hysteretic energy dissipation capacity, displacement ductility, strength and stiffness degradation were examined. The research indicated that the compression deformation occurred to specimen S-1. Binding action was provided for concrete by steel tubes. The expansion from concrete to steel tubes occured because of the concrete’s cracking inside and bulking. Half-wave shapes of the steel tubes between tie bars occurred due to the bucking of thin steel tubes and the local constraint of tie bars. The bottom of concrete was crushed and steel tubes was buckled in quasi-static tests. The bottom of specimen S-3 without reinforcing stiffening rings at the two ends and with smaller shear span-to-effective depth ratios was more seriously damaged and the energy dissipation capacity was lower than specimen S-2. A design formula to calculate axial bearing capacity of columns was proposed, and the influence of the constraint effect from tie bars on the plastic hinge length of column ends was discussed.
The tests were conducted on three reinforced concrete-filled steel square tubular columns with tie bars, which included one axial compressive test for S-1 and two pseudo-static tests for S-2 and S-3. The bearing capacity, failure modes, failure paths, hysteretic energy dissipation capacity, displacement ductility, strength and stiffness degradation were examined. The research indicated that the compression deformation occurred to specimen S-1. Binding action was provided for concrete by steel tubes. The expansion from concrete to steel tubes occured because of the concrete’s cracking inside and bulking. Half-wave shapes of the steel tubes between tie bars occurred due to the bucking of thin steel tubes and the local constraint of tie bars. The bottom of concrete was crushed and steel tubes was buckled in quasi-static tests. The bottom of specimen S-3 without reinforcing stiffening rings at the two ends and with smaller shear span-to-effective depth ratios was more seriously damaged and the energy dissipation capacity was lower than specimen S-2. A design formula to calculate axial bearing capacity of columns was proposed, and the influence of the constraint effect from tie bars on the plastic hinge length of column ends was discussed.
2021, 51(1): 45-53,109.
doi: 10.13204/j.gyjzG19111215
Abstract:
25 prefabricated skip-floor shear wall models were established for static elastoplastic analysis to explore the load-bearing mechanism at the connection interface. Then, the influence of axial compression ratios, length-to-width ratios and other factors on the bearing capacity of the bolts at the interface were analyzed, and the fitting formulas for shearing unevenness coefficients of bolts and shear ratios of bolts were proposed. Finally, the bolts of the prefabricated skip-floor shear wall were designed according to the formulas, and the seismic performances of prefabricated and cast-in-place skip-floor shear walls were compared by quasi-static elastoplastic simulations. The research results showed that the frictional resistance at the connection interface in most cases accounted for more than 80% of the total shearing force, prefabricated skip-floor shear walls designed with consideration of the uneven shear of bolts were of excellent seismic performance.
25 prefabricated skip-floor shear wall models were established for static elastoplastic analysis to explore the load-bearing mechanism at the connection interface. Then, the influence of axial compression ratios, length-to-width ratios and other factors on the bearing capacity of the bolts at the interface were analyzed, and the fitting formulas for shearing unevenness coefficients of bolts and shear ratios of bolts were proposed. Finally, the bolts of the prefabricated skip-floor shear wall were designed according to the formulas, and the seismic performances of prefabricated and cast-in-place skip-floor shear walls were compared by quasi-static elastoplastic simulations. The research results showed that the frictional resistance at the connection interface in most cases accounted for more than 80% of the total shearing force, prefabricated skip-floor shear walls designed with consideration of the uneven shear of bolts were of excellent seismic performance.
2021, 51(1): 54-60.
doi: 10.13204/j.gyjzG20190926006
Abstract:
In order to study seismic damage of interior joints in integrally prefabricated reinforced concrete frames, quasi-static tests were conclucted on one cast-in-place joint and three integrally prefabricated joints with different axial compression ratios. The damage process was observed and the mechanical properties of load-deformation and stiffness degradation were analyzed. Besides, the effects of axial compression ratios were compared. Finally, the modified Park-Ang’s damaged index model was used to discuss the influences such as axial compression ratios, concrete strength, stirrup eigenvalues and longitudinal reinforcement ratios on joint damage, and the total process damage of joints was quantitatively analyzed and classified. The results showed that the joints in the integrally prefabricated reinforced concrete frame under low cyclic loading went through five damaged stages in the test, in which the joints between beam ends and lower columns were the weak parts. The larger axial compression ratios could accelerate the joints damage. The increase of concrete strength, stirrup eigenvalues and longitudinal reinforcement ratios could obviously slow down the joint damage. The damaged index model used in the paper could better reflect the seismic damage of the tested joints.
In order to study seismic damage of interior joints in integrally prefabricated reinforced concrete frames, quasi-static tests were conclucted on one cast-in-place joint and three integrally prefabricated joints with different axial compression ratios. The damage process was observed and the mechanical properties of load-deformation and stiffness degradation were analyzed. Besides, the effects of axial compression ratios were compared. Finally, the modified Park-Ang’s damaged index model was used to discuss the influences such as axial compression ratios, concrete strength, stirrup eigenvalues and longitudinal reinforcement ratios on joint damage, and the total process damage of joints was quantitatively analyzed and classified. The results showed that the joints in the integrally prefabricated reinforced concrete frame under low cyclic loading went through five damaged stages in the test, in which the joints between beam ends and lower columns were the weak parts. The larger axial compression ratios could accelerate the joints damage. The increase of concrete strength, stirrup eigenvalues and longitudinal reinforcement ratios could obviously slow down the joint damage. The damaged index model used in the paper could better reflect the seismic damage of the tested joints.
2021, 51(1): 61-67,93.
doi: 10.13204/j.gyjzG19112302
Abstract:
To explore the effects of ratios of shear spans to effective depths, axial pressure, and structural measures on seismic performances of prefabricated concrete-block walls, low cycle reciprocated loading tests on six block walls were conducted and hysteretic characteristics, bearing capacity, stiffness degradation and ductility of the prefabricated concrete-block walls were analyzed. The results showed that the seismic performances of walls were significantly affected by structure columns or core columns, and ratios of shear spans to effective depths and axial pressure could significantly influcence shear capacities of walls. In practical engineering, the seismic performances of the walls could be improved by adding appropriate structure columns or core columns.
To explore the effects of ratios of shear spans to effective depths, axial pressure, and structural measures on seismic performances of prefabricated concrete-block walls, low cycle reciprocated loading tests on six block walls were conducted and hysteretic characteristics, bearing capacity, stiffness degradation and ductility of the prefabricated concrete-block walls were analyzed. The results showed that the seismic performances of walls were significantly affected by structure columns or core columns, and ratios of shear spans to effective depths and axial pressure could significantly influcence shear capacities of walls. In practical engineering, the seismic performances of the walls could be improved by adding appropriate structure columns or core columns.
2021, 51(1): 68-72.
doi: 10.13204/j.gyjzG20082811
Abstract:
In order to improve the assembly efficiency of structure members, a new type of prefabricated beam-column-corbel combined joint in industrial structures was proposed. RC column corbels were welded with steel bars which would inserted into the reserved holes on beams during installation, and between the columns and beams, foam blocks were filled, which were sealed with epoxy, and grouted with M7.5 non-shrink mortar between epoxy blocks and beams. A finite element model of the combined joint was established by ABAQUS and simulations of mechanical properties was performed. The failure mode, bearing capacity, ductility and energy dissipation capacity were simulated. The results showed that the hysteretic curves of the joints were full and round that was to be of good ductility and energy dissipation capacity. Main failure occurred at the beam ends, in which the plastic hinge was formed finally, meeting to the design principles of "strong columns and weak beams"and "strong joints and weak members".
In order to improve the assembly efficiency of structure members, a new type of prefabricated beam-column-corbel combined joint in industrial structures was proposed. RC column corbels were welded with steel bars which would inserted into the reserved holes on beams during installation, and between the columns and beams, foam blocks were filled, which were sealed with epoxy, and grouted with M7.5 non-shrink mortar between epoxy blocks and beams. A finite element model of the combined joint was established by ABAQUS and simulations of mechanical properties was performed. The failure mode, bearing capacity, ductility and energy dissipation capacity were simulated. The results showed that the hysteretic curves of the joints were full and round that was to be of good ductility and energy dissipation capacity. Main failure occurred at the beam ends, in which the plastic hinge was formed finally, meeting to the design principles of "strong columns and weak beams"and "strong joints and weak members".
2021, 51(1): 73-80.
doi: 10.13204/j.gyjzG20010803
Abstract:
Central pulling test on 44 cubic specimens of conventional concrete and recycled concrete (the replacement ratio of coarse aggregate is 100%) were subjected to high temperatures. Tthe damage laws of bonding performances of the steel bars and concrete after and in high temperatures and the characteristics of bond-slip (τ-s) relation curves were studied.The experimental results showed that after and in high temperatures, the ultimate bond strength of steel bars and concrete decreased with increase of temperatures, and the ultimate slip values increased with increase of temperatures.According to the changing characteristics of the bond-slip curves between steel bars and concrete, the bond-slip failure process of steel bars and concrete in high temperaturs could be divided into five stages to analyze the bond performance damage.By setting damage variables and using regression analysis methods, to establish the τ-s relation equations between steel bars and concrete after and in high temperatures. And through the calculation of test deviation, the calculation results were in good agreements with the test results.
Central pulling test on 44 cubic specimens of conventional concrete and recycled concrete (the replacement ratio of coarse aggregate is 100%) were subjected to high temperatures. Tthe damage laws of bonding performances of the steel bars and concrete after and in high temperatures and the characteristics of bond-slip (τ-s) relation curves were studied.The experimental results showed that after and in high temperatures, the ultimate bond strength of steel bars and concrete decreased with increase of temperatures, and the ultimate slip values increased with increase of temperatures.According to the changing characteristics of the bond-slip curves between steel bars and concrete, the bond-slip failure process of steel bars and concrete in high temperaturs could be divided into five stages to analyze the bond performance damage.By setting damage variables and using regression analysis methods, to establish the τ-s relation equations between steel bars and concrete after and in high temperatures. And through the calculation of test deviation, the calculation results were in good agreements with the test results.
DYNAMIC RESPONSE ANALYSIS OF NEAR-FAULT EFFECTS OF RIGID-FRAMED BRIDGES BASED ON SHAKING TABLE TESTS
2021, 51(1): 81-85.
doi: 10.13204/j.gyjzG20070717
Abstract:
A shaking tables test considering multi-support excitation was conducted on the 1∶10 scale three-span rigid-framed bridge. Taking the results of the test as a base, the finite element model of the bridge was established. Ten typical near-fault ground motions were selected for analysis. Then, the comparative analysis of the dynamic responses between the far-field ground motions and near-fault ground motions was completed. The research showed that the spatial effect of ground motion was unfavorable to the deformation and stress of piers, and its influence was closely related to the constraint forms of piers and girders and the wave velocity. Compared with the far-field ground motion, the aPGV/aPGA of the near-fault ground motion was larger. Considering the near-fault effect, the deformation and stress of the piers increased, and the mid-span bending moment and horizontal displacement of the main girders also increased. Therefore, near-fault effect and ground motion spatial effect should be considered in seismic design to make the analysis results more accurate.
A shaking tables test considering multi-support excitation was conducted on the 1∶10 scale three-span rigid-framed bridge. Taking the results of the test as a base, the finite element model of the bridge was established. Ten typical near-fault ground motions were selected for analysis. Then, the comparative analysis of the dynamic responses between the far-field ground motions and near-fault ground motions was completed. The research showed that the spatial effect of ground motion was unfavorable to the deformation and stress of piers, and its influence was closely related to the constraint forms of piers and girders and the wave velocity. Compared with the far-field ground motion, the aPGV/aPGA of the near-fault ground motion was larger. Considering the near-fault effect, the deformation and stress of the piers increased, and the mid-span bending moment and horizontal displacement of the main girders also increased. Therefore, near-fault effect and ground motion spatial effect should be considered in seismic design to make the analysis results more accurate.
2021, 51(1): 86-93.
doi: 10.13204/j.gyjzG20011702
Abstract:
Based on the idea of damage control, a composite load-bearing self-resetting beam-column joint was proposed, which provided pretension for the structure through high-strength prestressed steel cables so that the structure could realize self-resetting subjected to earthquake action. The dog-bone weakened cover plate installed on the joint could be replaced after earthquake so that the structure was repaired. The finite element simulation for five joint models was conducted. By changing initial cable forces of high-strength prestressed cables and the thickness of dog-bone weakened cover plates, the influences of the two on the bearing capacity, energy dissipation capacity, self-resetting capacity and repairability after earthquake of the joints were studied, and the load-displacement curves, cable force change curves and stress distribution forms of the five models were obtained. The research showed based on the premise of ensuring the self-resetting of the model, the plastic damage without dog-bone weakened cover plates was more serious. The specimens with dog-bone weakening cover plates could effectively reduce the plastic damage of the main elements of the joints. Increasing the thickness of dog-bone weakening cover plates and cable forces could both improve the bearing capacity and energy consumption capacity of joints, but increasing the thickness of dog-bone weakening cover plates was more obvious.
Based on the idea of damage control, a composite load-bearing self-resetting beam-column joint was proposed, which provided pretension for the structure through high-strength prestressed steel cables so that the structure could realize self-resetting subjected to earthquake action. The dog-bone weakened cover plate installed on the joint could be replaced after earthquake so that the structure was repaired. The finite element simulation for five joint models was conducted. By changing initial cable forces of high-strength prestressed cables and the thickness of dog-bone weakened cover plates, the influences of the two on the bearing capacity, energy dissipation capacity, self-resetting capacity and repairability after earthquake of the joints were studied, and the load-displacement curves, cable force change curves and stress distribution forms of the five models were obtained. The research showed based on the premise of ensuring the self-resetting of the model, the plastic damage without dog-bone weakened cover plates was more serious. The specimens with dog-bone weakening cover plates could effectively reduce the plastic damage of the main elements of the joints. Increasing the thickness of dog-bone weakening cover plates and cable forces could both improve the bearing capacity and energy consumption capacity of joints, but increasing the thickness of dog-bone weakening cover plates was more obvious.
2021, 51(1): 94-99.
doi: 10.13204/j.gyjz20092706
Abstract:
A partially fabricated concrete-filled steel square tubular column with a inner tie bar frame was designed. In order to reduce the cost and determine the optimal proportion of steel mass consumed in the structure, according to the orthogonal experimental design method, 9 groups of specimens and 3 groups of control specimens were designed for axial compression tests of short columns. The results indicated that the bearing capacity of the new kind of column subjected to axial compression could be improved effectively in the same consumption of steel. The axial compressive bearing capacity of the member was higher when the steel consumption of steel pipes, vertical rebars and horizontal tie bars was about 45∶35∶20. If the ratio of horizontal tie bars was too small, a significant reduction in axial bearing capacity would take place due to insufficient tie forces, and the recommended value was not less than 20%. Besides, the influence with or without tie-bar frames on the ductility of the structure was not obvious in the same total consumption of steel. For pre fabricated structures, the influence of the fabrication errors of members and the quality of cast concrete on the bearing capacity of members could be ignored.
A partially fabricated concrete-filled steel square tubular column with a inner tie bar frame was designed. In order to reduce the cost and determine the optimal proportion of steel mass consumed in the structure, according to the orthogonal experimental design method, 9 groups of specimens and 3 groups of control specimens were designed for axial compression tests of short columns. The results indicated that the bearing capacity of the new kind of column subjected to axial compression could be improved effectively in the same consumption of steel. The axial compressive bearing capacity of the member was higher when the steel consumption of steel pipes, vertical rebars and horizontal tie bars was about 45∶35∶20. If the ratio of horizontal tie bars was too small, a significant reduction in axial bearing capacity would take place due to insufficient tie forces, and the recommended value was not less than 20%. Besides, the influence with or without tie-bar frames on the ductility of the structure was not obvious in the same total consumption of steel. For pre fabricated structures, the influence of the fabrication errors of members and the quality of cast concrete on the bearing capacity of members could be ignored.
2021, 51(1): 100-109.
doi: 10.13204/j.gyjzG20040803
Abstract:
Large numbers of self-tapping screws are used to fix aluminum sheets in the metal roofing system where the pull-out accidents of screw connections were reported frequently subjected to the wind uplift loads. In order to study the pull-out characteristics and presented a calculation method of self-tapping stainless steel screws to connect aluminum sheets, tensile tests of 198 connected specimens with different drilling methods, thicknesses of aluminum sheets, pitch and major diameters were conducted. Based on the results, the influences of different factors on the pull-out characteristics of self-tapping screws fixed aluminum sheets. The results indicated that the pull-out bearing capacity increased with the increase of aluminum sheet thickness, pitch and major diameters. The pull-out bearing capacity of specimens for carbon steel screw was better than that for stainless steel screw. The specimens with small pitch was susceptible of construction, which affected the pull-out bearing capacity. The test results were compared with the calculated results from the formulas recommended by codes of home and abroad. The formula for pull-out bearing capacity of self-tapping screws to fix aluminum sheets was modified. The results calculated by the modified formula fitted well with the test results.
Large numbers of self-tapping screws are used to fix aluminum sheets in the metal roofing system where the pull-out accidents of screw connections were reported frequently subjected to the wind uplift loads. In order to study the pull-out characteristics and presented a calculation method of self-tapping stainless steel screws to connect aluminum sheets, tensile tests of 198 connected specimens with different drilling methods, thicknesses of aluminum sheets, pitch and major diameters were conducted. Based on the results, the influences of different factors on the pull-out characteristics of self-tapping screws fixed aluminum sheets. The results indicated that the pull-out bearing capacity increased with the increase of aluminum sheet thickness, pitch and major diameters. The pull-out bearing capacity of specimens for carbon steel screw was better than that for stainless steel screw. The specimens with small pitch was susceptible of construction, which affected the pull-out bearing capacity. The test results were compared with the calculated results from the formulas recommended by codes of home and abroad. The formula for pull-out bearing capacity of self-tapping screws to fix aluminum sheets was modified. The results calculated by the modified formula fitted well with the test results.
2021, 51(1): 110-117.
doi: 10.13204/j.gyjzG20011302
Abstract:
To ascertain the influential mechanisms of the microstructure for soft soil on the macroscopic mechanical properties, consolidation shear tests of mucky soil in Nansha zone of Guangzhou were conducted. Combined with the scanning electron microscope and the microscopic tomography technique, the microstructure changes of the upper and lower parts for specimens and the influential mechanisms on the shear strength were qualitatively and quantitatively analyzed. The results showed that the void ratios of the soft soil gradually decreased with the continuous increase of consolidation pressure, and the final void ratios were mostly between 0.5 to 0.6. There were obvious inflection points for void ratios, and the values of lg(p/kPa) were mostly between 1.5 and 2.0. After shear failure, the moisture contents of the soil specimens from lower locations were significantly higher than that from of the upper, and the differences ranged from 1.8% to 3.3%.The cohension values of mucky soil had little relation with the initial moisture contents of the specimens, and the values of angles for internal friction were about 14° measured by quick direct shear tests. From the perspective of spatial structure, Nansha mucky soil had a variety of structural types, including honeycomb, spongy and flocculent structure, as well as flake, skeleton and agglomerate structure. The contact modes were mainly face-face, face-side, angle-face and angle-angle. The response mechanisms of consolidation pressure, free water and particles could well explain phenomena of engineering silting.
To ascertain the influential mechanisms of the microstructure for soft soil on the macroscopic mechanical properties, consolidation shear tests of mucky soil in Nansha zone of Guangzhou were conducted. Combined with the scanning electron microscope and the microscopic tomography technique, the microstructure changes of the upper and lower parts for specimens and the influential mechanisms on the shear strength were qualitatively and quantitatively analyzed. The results showed that the void ratios of the soft soil gradually decreased with the continuous increase of consolidation pressure, and the final void ratios were mostly between 0.5 to 0.6. There were obvious inflection points for void ratios, and the values of lg(p/kPa) were mostly between 1.5 and 2.0. After shear failure, the moisture contents of the soil specimens from lower locations were significantly higher than that from of the upper, and the differences ranged from 1.8% to 3.3%.The cohension values of mucky soil had little relation with the initial moisture contents of the specimens, and the values of angles for internal friction were about 14° measured by quick direct shear tests. From the perspective of spatial structure, Nansha mucky soil had a variety of structural types, including honeycomb, spongy and flocculent structure, as well as flake, skeleton and agglomerate structure. The contact modes were mainly face-face, face-side, angle-face and angle-angle. The response mechanisms of consolidation pressure, free water and particles could well explain phenomena of engineering silting.
2021, 51(1): 118-124,130.
doi: 10.13204/j.gyjz20052030
Abstract:
The conventional triaxial test and the improved triaxial test are mainly used to study change laws of mechanical properties for soil in mining areas before and after being disturbed by mining. Based on the results of the triaxial tests subjected to lateral unloading or loading and the attenuation characteristics of physical and mechanical parameters for coal gangue under the coupling effects of natural factors, soft foundation and mining influence, the evolution laws of stability for railway embankments of coal gangue in subsidence zones affected by mining were researched. The results showed that under the influences of mining, the mechanical indexes of the foundation soil decreased, the reduction factor for soft soil was about 0.9 to 1.0, and the reduction factor was 0.6 to 0.7 for other soil. The overall and local stability analysis showed that the safety factors of embankments for coal gangue on conventional foundation conditions were the largest at the same groundwater level, the safety factors of embankments of coal gangue on soft foundation decreased sharply due to being mined. Under the same foundation conditions, the higher the level of groundwater, the samller the safety factors of embankments, the stability to embankments of coal gangue on soft foundation affected by mining was lower when the groundwater level was higher than 5 m, the safety factors of embankments could not meet the Code for Design on special Railway Earth Structure TB 10035-2018. Therefore, under the coupling action of rainwater and weathering, embankments in the subsidence zone should be reinforced.
The conventional triaxial test and the improved triaxial test are mainly used to study change laws of mechanical properties for soil in mining areas before and after being disturbed by mining. Based on the results of the triaxial tests subjected to lateral unloading or loading and the attenuation characteristics of physical and mechanical parameters for coal gangue under the coupling effects of natural factors, soft foundation and mining influence, the evolution laws of stability for railway embankments of coal gangue in subsidence zones affected by mining were researched. The results showed that under the influences of mining, the mechanical indexes of the foundation soil decreased, the reduction factor for soft soil was about 0.9 to 1.0, and the reduction factor was 0.6 to 0.7 for other soil. The overall and local stability analysis showed that the safety factors of embankments for coal gangue on conventional foundation conditions were the largest at the same groundwater level, the safety factors of embankments of coal gangue on soft foundation decreased sharply due to being mined. Under the same foundation conditions, the higher the level of groundwater, the samller the safety factors of embankments, the stability to embankments of coal gangue on soft foundation affected by mining was lower when the groundwater level was higher than 5 m, the safety factors of embankments could not meet the Code for Design on special Railway Earth Structure TB 10035-2018. Therefore, under the coupling action of rainwater and weathering, embankments in the subsidence zone should be reinforced.
2021, 51(1): 125-130.
doi: 10.13204/j.gyjzG20041107
Abstract:
Energy piles are combinations of pile foundations and ground source heat pumps. They not only bear the upper building load but also act as media for heat exchange with the shallow geothermal energy, which are of advantage on energy-saving and pollution reduction. Based on indoor model tests, the displacement of pile tops, pile bottom pressure, temperature stress and side friction resistance of energy piles in clay foundation under the action of cyclic temperature were experimentally studied. It was concluded that the rise or fall in temperature could also cause tensile and compressive stress in piles, stress increased first and then decreased in pile shafts from tops to bottoms of piles, and the maximum stress was close to the lower middle parts of piles. The compressive stress of pile bottoms increased with the increase of temperature, and the maximum compressive stress decreased with the increase of temperature cycles. Friction resistance of pile sides increased with the increase of temperature. During the period of being heated and cooled, and the negative friction resistance would be generated on upper parts and lower parts of piles respectively.
Energy piles are combinations of pile foundations and ground source heat pumps. They not only bear the upper building load but also act as media for heat exchange with the shallow geothermal energy, which are of advantage on energy-saving and pollution reduction. Based on indoor model tests, the displacement of pile tops, pile bottom pressure, temperature stress and side friction resistance of energy piles in clay foundation under the action of cyclic temperature were experimentally studied. It was concluded that the rise or fall in temperature could also cause tensile and compressive stress in piles, stress increased first and then decreased in pile shafts from tops to bottoms of piles, and the maximum stress was close to the lower middle parts of piles. The compressive stress of pile bottoms increased with the increase of temperature, and the maximum compressive stress decreased with the increase of temperature cycles. Friction resistance of pile sides increased with the increase of temperature. During the period of being heated and cooled, and the negative friction resistance would be generated on upper parts and lower parts of piles respectively.
2021, 51(1): 131-134.
doi: 10.13204/j.gyjz20021050
Abstract:
In order to improve the seismic performances of tubular piles of prestressed high-strength concrete (PHC), carbon fibers were mixed into concrete to improve seismic performances. Based on low-cycle reciprocating loading tests of 4 tubular piles of PHC for two types. The experimental phenomena were observed, and the change trend of hysteretic curves, skeleton curves, strength and stiffness degradation, ductility and energy dissipation performances were analyzed, and the influences of carbon fibers mixed into concrete on the seismic performances of PHC piles were emphatically studied. The results showed that: mixing carbon fibers into concrete could improve adhensive force of concrete, improve the tensile performances of concrete, delay concrete crack, reduce the stiffness degradation of PHC piles, improve the stiffness, strength and energy dissipation performance of PHC piles.
In order to improve the seismic performances of tubular piles of prestressed high-strength concrete (PHC), carbon fibers were mixed into concrete to improve seismic performances. Based on low-cycle reciprocating loading tests of 4 tubular piles of PHC for two types. The experimental phenomena were observed, and the change trend of hysteretic curves, skeleton curves, strength and stiffness degradation, ductility and energy dissipation performances were analyzed, and the influences of carbon fibers mixed into concrete on the seismic performances of PHC piles were emphatically studied. The results showed that: mixing carbon fibers into concrete could improve adhensive force of concrete, improve the tensile performances of concrete, delay concrete crack, reduce the stiffness degradation of PHC piles, improve the stiffness, strength and energy dissipation performance of PHC piles.
2021, 51(1): 135-139,145.
doi: 10.13204/j.gyjzG20021502
Abstract:
According to the actual conditions of construction projects in Africa, the properties and microstructure of two kinds of high fluidity concrete were compared. Compared with Portland slag cement concrete mixed with silica fumes used now, the optimized ordinary Portland cement concrete had been appropriately reduced the water-binder ratio, increased the paste-aggregate ratio, and adjusted the type and amounts of admixture. Slump flow of fresh concrete and compressive strength of hardened concrete were measured, early hydration exothermic characteristics of paste were studied, and microstructure and pore characteristics of harden paste were analyzed by SEM and MIP. The results showed that the performances of flow, slump retention, and compressive strength at each age of ordinary Portland cement concrete were better than that of slag Portland cement concrete mixed with silica fumes. The early hydration degree of ordinary Portland cement paste was higher than that of slag Portland cement paste mixed with silica fume, and the pore structure of ordinary Portland cement paste was denser.
According to the actual conditions of construction projects in Africa, the properties and microstructure of two kinds of high fluidity concrete were compared. Compared with Portland slag cement concrete mixed with silica fumes used now, the optimized ordinary Portland cement concrete had been appropriately reduced the water-binder ratio, increased the paste-aggregate ratio, and adjusted the type and amounts of admixture. Slump flow of fresh concrete and compressive strength of hardened concrete were measured, early hydration exothermic characteristics of paste were studied, and microstructure and pore characteristics of harden paste were analyzed by SEM and MIP. The results showed that the performances of flow, slump retention, and compressive strength at each age of ordinary Portland cement concrete were better than that of slag Portland cement concrete mixed with silica fumes. The early hydration degree of ordinary Portland cement paste was higher than that of slag Portland cement paste mixed with silica fume, and the pore structure of ordinary Portland cement paste was denser.
2021, 51(1): 140-145.
doi: 10.13204/j.gyjzG20111009
Abstract:
Compared with the traditional steam curing technique of ultra-high performance concrete (UHPC), the UHPC under natural curing technique is of lower energy consumption and boarder application prospects in bridge engineering. Based on the compression test of concrete cubes, axial compression test, flexural test, elastic modulus measuring, and et al, To increase the mechanical properties of UHPC, the traditional production process was improved with conventional materials in the normal temperature curing. The effects of types of water reducers, volume fractions of steel fiber and curing condition on the mechanical characteristics of UHPC were examized. The results showed that the polycarboxylate superplasticizers could improve the compressive strength of UHPC specimens with the same volume fractions of steel fiber better than the naphthalene water reducers. The compressive strength and flexural tensile strength of UHPC specimens were significantly increased with the increase of steel fiber volume fractions within of 2%, and the other mechanical properties of UHPC specimens except the flexural tensile strength, were close to that of the UHPC specimens in the standard curing state.
Compared with the traditional steam curing technique of ultra-high performance concrete (UHPC), the UHPC under natural curing technique is of lower energy consumption and boarder application prospects in bridge engineering. Based on the compression test of concrete cubes, axial compression test, flexural test, elastic modulus measuring, and et al, To increase the mechanical properties of UHPC, the traditional production process was improved with conventional materials in the normal temperature curing. The effects of types of water reducers, volume fractions of steel fiber and curing condition on the mechanical characteristics of UHPC were examized. The results showed that the polycarboxylate superplasticizers could improve the compressive strength of UHPC specimens with the same volume fractions of steel fiber better than the naphthalene water reducers. The compressive strength and flexural tensile strength of UHPC specimens were significantly increased with the increase of steel fiber volume fractions within of 2%, and the other mechanical properties of UHPC specimens except the flexural tensile strength, were close to that of the UHPC specimens in the standard curing state.
2021, 51(1): 146-151.
doi: 10.13204/j.gyjzG20012801
Abstract:
The three-point bending tests on notched beams of different ages were conducted. The effects of ages on the fracture properties of oriented steel fiber-reinforced cementitious composites and randomly oriented steel fiber-reinforced cementitious composites were studied. Based on the curves of loadimg and crack opening displacement, the whole process of crack development of steel fiber-reinforced cementitious composites at different curing ages was analyzed. The results showed that, the flexural strength of steel fiber-reinforced cementitious composites increased with the increase of curing ages. The fracture energy of the composites increased rapidly in the stage of the first 7 days, and then slowed down and tended to be stable. When the volume contents of steel fiber varied from 1.2% to 2.0%, the fracture energy increased significantly, and the inprovement effect of the fracture energy of the composites was more obvious than that of randomly oriented fiber-reinforced cementitions conposites.
The three-point bending tests on notched beams of different ages were conducted. The effects of ages on the fracture properties of oriented steel fiber-reinforced cementitious composites and randomly oriented steel fiber-reinforced cementitious composites were studied. Based on the curves of loadimg and crack opening displacement, the whole process of crack development of steel fiber-reinforced cementitious composites at different curing ages was analyzed. The results showed that, the flexural strength of steel fiber-reinforced cementitious composites increased with the increase of curing ages. The fracture energy of the composites increased rapidly in the stage of the first 7 days, and then slowed down and tended to be stable. When the volume contents of steel fiber varied from 1.2% to 2.0%, the fracture energy increased significantly, and the inprovement effect of the fracture energy of the composites was more obvious than that of randomly oriented fiber-reinforced cementitions conposites.
2021, 51(1): 152-156,178.
doi: 10.13204/j.gyjzG19102204
Abstract:
According to test results of pull-out tests for 6 specimens and uniaxial tensile tests for 27 grouted sleeve-splicing specimens,the influences of PVA fiber, anchorage length of rebars and with or without confines of grouted sleeves on splicing were analyzed. The results showed that the addition of PVA fiber could improve the bonding strength between the unconfined rebars and grouting materials, but had not obvious impact on the properties of grouted sleeve splicing. The rigidity of grouted sleeve splicing increased with the increase of anchorage length and the load-displacement curves was also more smoother. When the strength of the grouting materials was up to 85 to 90 MPa, the anchorage length of six times diameter of rebars could well meet the strength requirement of the grouted sleeve splicing. The constraint of sleeves could improve the bonding strength of the sleeves, grouting materials and rebars.
According to test results of pull-out tests for 6 specimens and uniaxial tensile tests for 27 grouted sleeve-splicing specimens,the influences of PVA fiber, anchorage length of rebars and with or without confines of grouted sleeves on splicing were analyzed. The results showed that the addition of PVA fiber could improve the bonding strength between the unconfined rebars and grouting materials, but had not obvious impact on the properties of grouted sleeve splicing. The rigidity of grouted sleeve splicing increased with the increase of anchorage length and the load-displacement curves was also more smoother. When the strength of the grouting materials was up to 85 to 90 MPa, the anchorage length of six times diameter of rebars could well meet the strength requirement of the grouted sleeve splicing. The constraint of sleeves could improve the bonding strength of the sleeves, grouting materials and rebars.
2021, 51(1): 157-162,199.
doi: 10.13204/j.gyjzG20022712
Abstract:
Taking Q460 and Q600 high-strength steel as research objects, the mechanical properties of 14 perforated high-strength steel specimens under uniaxial tension were tested. The damage characteristics, stress-strain hysteresis curves and corresponding energy dissipation of specimens were analyzed in detail. The results showed that the fracture of non-perforated specimens accompanied apparent necking; as stress concentration, the opening positions were the weakest parts destroyed for specimens. Q600 steel reflected the advantage of more higher strength, energy dissipation capability and ductility than that of Q460 steel. Increasing the thickness could improve the ultimate strength, plastic deformation capacity and energy dissipation capacity of the steels. The mechanical properties would be reduced to a certain extent because of perforation. The influence of the openings on energy dissipation capability was obvious. Comparing with the specinens with openings perpendicaular to the tensile direction, the specimens with openings along the tensile direction were of better capability of energy dissipation.
Taking Q460 and Q600 high-strength steel as research objects, the mechanical properties of 14 perforated high-strength steel specimens under uniaxial tension were tested. The damage characteristics, stress-strain hysteresis curves and corresponding energy dissipation of specimens were analyzed in detail. The results showed that the fracture of non-perforated specimens accompanied apparent necking; as stress concentration, the opening positions were the weakest parts destroyed for specimens. Q600 steel reflected the advantage of more higher strength, energy dissipation capability and ductility than that of Q460 steel. Increasing the thickness could improve the ultimate strength, plastic deformation capacity and energy dissipation capacity of the steels. The mechanical properties would be reduced to a certain extent because of perforation. The influence of the openings on energy dissipation capability was obvious. Comparing with the specinens with openings perpendicaular to the tensile direction, the specimens with openings along the tensile direction were of better capability of energy dissipation.
2021, 51(1): 163-168.
doi: 10.13204/j.gyjzG201908130001
Abstract:
The profiled steel sheet specimens with different thickness and corrosion degrees were obtained by accelerated corrosion tests. Based on the three-dimensional surface forms and tensile test results, the variation law of surface roughness parameters with corrosion time, failure modes of specimens with different corrosion degrees, difference of stress-strain curves, functional relations between tensile property parameters and corrosion rates were analyzed. A constitutive model of performance degradation for profiled steel sheets was proposed. The results showed that the surface roughness parameters of specimens changed in grades with the increase of corrosion time. With the increase of corrosion rates, the fracture mode of specimens changed from smooth oblique fracture to serrated or echelon form fracture, while the yield platforms and striction sections were gradually shortened, and the tensile mechanical indexes were gradually degraded. The degraded constitutive model could well characterize the degraded law of steel properties with different corrosion degrees.
The profiled steel sheet specimens with different thickness and corrosion degrees were obtained by accelerated corrosion tests. Based on the three-dimensional surface forms and tensile test results, the variation law of surface roughness parameters with corrosion time, failure modes of specimens with different corrosion degrees, difference of stress-strain curves, functional relations between tensile property parameters and corrosion rates were analyzed. A constitutive model of performance degradation for profiled steel sheets was proposed. The results showed that the surface roughness parameters of specimens changed in grades with the increase of corrosion time. With the increase of corrosion rates, the fracture mode of specimens changed from smooth oblique fracture to serrated or echelon form fracture, while the yield platforms and striction sections were gradually shortened, and the tensile mechanical indexes were gradually degraded. The degraded constitutive model could well characterize the degraded law of steel properties with different corrosion degrees.
2021, 51(1): 169-178.
doi: 10.13204/j.gyjzG20090813
Abstract:
The construction of lunar bases is of great significance for long-term human presence on the moon. The environmental and resource conditions regarding lunar base construction were reviewed and researched. It was demonstrated that the in-situ construction using lunar regolith was a practical and feasible construction scheme considering its various advantages including construction convenience and cost efficiency. The existing studies on construction technology based on lunar regolith could be categorized into two groups: downward excavation and upward construction. In particular, the upward construction employed the different techniques including lunar regolith concrete, lunar regolith sintering, lunar regolith bonding and regolith bags. Based on the review and analysis, a novel lunar in-situ construction scheme was proposed, which comprehensively used the techniques including 3D printed lunar regolith concrete and regolith bags, so as to realize the automatic construction using in-situ resources. It provided a new technical path for lunar base construction.
The construction of lunar bases is of great significance for long-term human presence on the moon. The environmental and resource conditions regarding lunar base construction were reviewed and researched. It was demonstrated that the in-situ construction using lunar regolith was a practical and feasible construction scheme considering its various advantages including construction convenience and cost efficiency. The existing studies on construction technology based on lunar regolith could be categorized into two groups: downward excavation and upward construction. In particular, the upward construction employed the different techniques including lunar regolith concrete, lunar regolith sintering, lunar regolith bonding and regolith bags. Based on the review and analysis, a novel lunar in-situ construction scheme was proposed, which comprehensively used the techniques including 3D printed lunar regolith concrete and regolith bags, so as to realize the automatic construction using in-situ resources. It provided a new technical path for lunar base construction.
2021, 51(1): 179-186,193.
doi: 10.13204/j.gyjzG20022803
Abstract:
In order to study the blast-resistant capacity of concrete-filled steel tube columns confined with fiber-reinforced polymer(FRP) under axial compression, the numerical simulations and analysis on the dynamic response of 16 axial compressive column specimens subjected to blast loads was calculated by finite element software ANSYS/LS-DYNA. And the effects of axial compression ratios, slenderness ratios, the pasting method of FRP sheets and the type of FRP sheets on the blast resistant capacity of specimens were studied by parametric analysis. The results showed that when the axial compression ratio was not exceed 0.5, the existence of axial pressure could improve the anti-detonation performances of the specimens, however, when the axial compression ratio was greater than 0.5, the existence of axial pressure greatly weakened the anti-detonation performances of the specimens. With the increase of slenderness ratios, the mid-span displacement of the specimens increased, and the blast resistant capacity decreased. Pasting FRP sheets could improve the anti-explosion performances of the specimens, and the specimens locally pasted FRP with reasonable design could achieve the constraint effect with those fully pasted. Under the condition that other parameters remained unchanged, pasting CFRP sheets was more effective in improving the blast-resistant performances of specimens than pasting GFRP sheets.
In order to study the blast-resistant capacity of concrete-filled steel tube columns confined with fiber-reinforced polymer(FRP) under axial compression, the numerical simulations and analysis on the dynamic response of 16 axial compressive column specimens subjected to blast loads was calculated by finite element software ANSYS/LS-DYNA. And the effects of axial compression ratios, slenderness ratios, the pasting method of FRP sheets and the type of FRP sheets on the blast resistant capacity of specimens were studied by parametric analysis. The results showed that when the axial compression ratio was not exceed 0.5, the existence of axial pressure could improve the anti-detonation performances of the specimens, however, when the axial compression ratio was greater than 0.5, the existence of axial pressure greatly weakened the anti-detonation performances of the specimens. With the increase of slenderness ratios, the mid-span displacement of the specimens increased, and the blast resistant capacity decreased. Pasting FRP sheets could improve the anti-explosion performances of the specimens, and the specimens locally pasted FRP with reasonable design could achieve the constraint effect with those fully pasted. Under the condition that other parameters remained unchanged, pasting CFRP sheets was more effective in improving the blast-resistant performances of specimens than pasting GFRP sheets.
2021, 51(1): 187-193.
doi: 10.13204/j.gyjzG19122610
Abstract:
To confine concrete with fiber-reinforced polymer (FRP) can greatly improve the mechanical properties of concrete, which has been used in some application. However, the brittle failure of concrete confined with FRP restricted its application in some fields. To solve the problem, chopped basalt fiber (BF) was mixed to concrete while confining concrete with basalt fiber-reinforced polymer (BFRP) composites. By changing the number of BFRP layers and the volume content of BF, the mechanical properties of basalt-fiber-reinforced concrete confined with BFRP were studied experimentally. The results showed that the compressive strength and the maximum flexural resistance of the concrete increased with the increase of the number of BFRP layers, and the addition of BF could not only improve the strength of concrete but also the toughness of the concrete, changing the failure mode from brittle failure to plastic failure. The best performances of BF concrete confined with BFRP were at the BF content of 0.1%. Therefore, the addition of BF to concrete confined with BFRP could not only improve its mechanical properties but also its failure mode.
To confine concrete with fiber-reinforced polymer (FRP) can greatly improve the mechanical properties of concrete, which has been used in some application. However, the brittle failure of concrete confined with FRP restricted its application in some fields. To solve the problem, chopped basalt fiber (BF) was mixed to concrete while confining concrete with basalt fiber-reinforced polymer (BFRP) composites. By changing the number of BFRP layers and the volume content of BF, the mechanical properties of basalt-fiber-reinforced concrete confined with BFRP were studied experimentally. The results showed that the compressive strength and the maximum flexural resistance of the concrete increased with the increase of the number of BFRP layers, and the addition of BF could not only improve the strength of concrete but also the toughness of the concrete, changing the failure mode from brittle failure to plastic failure. The best performances of BF concrete confined with BFRP were at the BF content of 0.1%. Therefore, the addition of BF to concrete confined with BFRP could not only improve its mechanical properties but also its failure mode.
2021, 51(1): 194-199.
doi: 10.13204/j.gyjzG20082807
Abstract:
In order to study seismic responses of industrial workshops with SRC hybrid structure, an actual industrial workshop was simulated and analyzed by the finite element software SAP2000. Through modal analysis, response spectrum analysis, elastic time-history analysis and elastic-plastic time-history analysis, the results showed that the period ratio of the structure was less than 0.9. Under frequent and rare earthquakes, the maximum drift angle of stories by the modal decomposition method for response spectrum and elastic time-history analysis was 1/717, and the peak drift angle of the top floor analyzed by elastoplastic time-history was 1/81, both of which met the requirements of the specification GB 50011-2010 on the drift angles. The displacement responses and acceleration responses of the structure increased with the increase of earthquake intensities, and the instantaneous energy dissipation mainly occured in the peak acceleration periods, and the energy dissipation under rare earthquakes was much higher than that under frequent earthquakes.
In order to study seismic responses of industrial workshops with SRC hybrid structure, an actual industrial workshop was simulated and analyzed by the finite element software SAP2000. Through modal analysis, response spectrum analysis, elastic time-history analysis and elastic-plastic time-history analysis, the results showed that the period ratio of the structure was less than 0.9. Under frequent and rare earthquakes, the maximum drift angle of stories by the modal decomposition method for response spectrum and elastic time-history analysis was 1/717, and the peak drift angle of the top floor analyzed by elastoplastic time-history was 1/81, both of which met the requirements of the specification GB 50011-2010 on the drift angles. The displacement responses and acceleration responses of the structure increased with the increase of earthquake intensities, and the instantaneous energy dissipation mainly occured in the peak acceleration periods, and the energy dissipation under rare earthquakes was much higher than that under frequent earthquakes.
