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2020 Vol. 50, No. 3
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2020, 50(3): 1-7,12.
doi: 10.13204/j.gyjz202003001
Abstract:
14 short double-skin multi-cavity composite walls with steel truss were tested under axial compression. The influence of the end column of the cavity, the joints spacing of the steel bar truss and the diameter of the steel bar on the failure mode, bearing capacity and ductility of the shear walls were studied. The results showed that the ultimate bearing capacity and yield strength of the specimens were affected to some extent by the diameter of the steel bars, the joints spacing of the steel bar and the different forms of the end columns. The role of internal truss could enhance the cooperative working capacity between steel plate and concrete, and improve the ultimate bearing capacity and yield strength of the specimen.
14 short double-skin multi-cavity composite walls with steel truss were tested under axial compression. The influence of the end column of the cavity, the joints spacing of the steel bar truss and the diameter of the steel bar on the failure mode, bearing capacity and ductility of the shear walls were studied. The results showed that the ultimate bearing capacity and yield strength of the specimens were affected to some extent by the diameter of the steel bars, the joints spacing of the steel bar and the different forms of the end columns. The role of internal truss could enhance the cooperative working capacity between steel plate and concrete, and improve the ultimate bearing capacity and yield strength of the specimen.
2020, 50(3): 8-12.
doi: 10.13204/j.gyjz202003002
Abstract:
The double-skin multi-cavity composite wall consists of two external steel plates and infilled concrete. Mechanical connectors are used to enhance the composite action between the two materials. In the paper, a new truss connector was proposed, which can effectively delay the buckling of the steel plate and improve the overall performance of the wall. The ANSYS finite element software was used to simulate the wall performance, and the validity of the finite element model was verified by comparing the experimental data. Parametric analysis was carried out to study the influence of key parameters such as steel plate thickness, truss spacing and wall height-thickness ratio on the wall performance. The results showed that increasing the thickness of the steel plate could delay the buckling of the steel plate and increase the bearing capacity of the wall; increasing the truss spacing would reduce the restraining effect of the truss on the steel plate and the bearing capacity of the wall; changing the height-thickness ratio of the wall would affect the failure mode of the wall.
The double-skin multi-cavity composite wall consists of two external steel plates and infilled concrete. Mechanical connectors are used to enhance the composite action between the two materials. In the paper, a new truss connector was proposed, which can effectively delay the buckling of the steel plate and improve the overall performance of the wall. The ANSYS finite element software was used to simulate the wall performance, and the validity of the finite element model was verified by comparing the experimental data. Parametric analysis was carried out to study the influence of key parameters such as steel plate thickness, truss spacing and wall height-thickness ratio on the wall performance. The results showed that increasing the thickness of the steel plate could delay the buckling of the steel plate and increase the bearing capacity of the wall; increasing the truss spacing would reduce the restraining effect of the truss on the steel plate and the bearing capacity of the wall; changing the height-thickness ratio of the wall would affect the failure mode of the wall.
2020, 50(3): 13-18,50.
doi: 10.13204/j.gyjz202003003
Abstract:
Based on the quasi-static tests of three wall specimens with different axial compression ratios, the failure modes, bearing capacity, stiffness degradation, energy dissipation capacity, lateral deformation and shear deformation of the double-skin multi-cavity composite wall with steel truss were explored and analyzed in the paper. The results showed that the innovative double-skin composite wall with steel truss had better bearing capacity, ductility and energy dissipation capacity. When the aspect ratio was 2.0, the main failure characteristics of the specimens were local shear buckling of steel plates, fracture and buckling of steel tubes, and compressive crushing of concrete. The shear deformation accounted for 20% to 40% of the overall lateral deformation, and all specimens were damaged in shear-compression mode. The effect of axial compression ratio on the horizontal bearing capacity and stiffness degradation of the specimens was small, and the specimens with small axial compression ratio showed better ductility.
Based on the quasi-static tests of three wall specimens with different axial compression ratios, the failure modes, bearing capacity, stiffness degradation, energy dissipation capacity, lateral deformation and shear deformation of the double-skin multi-cavity composite wall with steel truss were explored and analyzed in the paper. The results showed that the innovative double-skin composite wall with steel truss had better bearing capacity, ductility and energy dissipation capacity. When the aspect ratio was 2.0, the main failure characteristics of the specimens were local shear buckling of steel plates, fracture and buckling of steel tubes, and compressive crushing of concrete. The shear deformation accounted for 20% to 40% of the overall lateral deformation, and all specimens were damaged in shear-compression mode. The effect of axial compression ratio on the horizontal bearing capacity and stiffness degradation of the specimens was small, and the specimens with small axial compression ratio showed better ductility.
2020, 50(3): 19-23,28.
doi: 10.13204/j.gyjz202003004
Abstract:
Based on the construction features of double-skin multi-cavity composite walls with steel truss,four new different configurations of the double-skin multi-cavity composite wall with steel truss to H-shaped steel beams connections proposed, so as to design four full-scale wall-beam joints (standard joint, cover-plate joint, vertical-plate joint and binding-plate joint). The finite element analysis (FEA) of specimens was carried out by using ANSYS software. The results showed that the four joints eventually cracked and failured at the flanges steel beam at the end of external plate, and could achieve the expected goal of shift-away of plastic hinge. The hysteresis loops were plump, which indicated that four wall-beam connections were possessed of good seismic behavior. Therefore, the four joints met the requirements of seismic design of Code for Seismic Design of Buildings (GB 50011—2010), which could be applied to the structure of composite wall with double skins stiffened by steel truss.
Based on the construction features of double-skin multi-cavity composite walls with steel truss,four new different configurations of the double-skin multi-cavity composite wall with steel truss to H-shaped steel beams connections proposed, so as to design four full-scale wall-beam joints (standard joint, cover-plate joint, vertical-plate joint and binding-plate joint). The finite element analysis (FEA) of specimens was carried out by using ANSYS software. The results showed that the four joints eventually cracked and failured at the flanges steel beam at the end of external plate, and could achieve the expected goal of shift-away of plastic hinge. The hysteresis loops were plump, which indicated that four wall-beam connections were possessed of good seismic behavior. Therefore, the four joints met the requirements of seismic design of Code for Seismic Design of Buildings (GB 50011—2010), which could be applied to the structure of composite wall with double skins stiffened by steel truss.
2020, 50(3): 24-28.
doi: 10.13204/j.gyjz202003005
Abstract:
In order to investigate the fire resistance of double-skin multi-cavity composite wall with steel truss, two specimens were tested exposed to one-side ISO-834 standard fire. A specimen was unprotected and the other was protected by thick coated fireproof coating with a thickness of 20 mm. The test results indicated that: 1)the bare specimen reached the fire resistance limit due to the failure of thermal insulation; 2)the thickness of fireproof coating had a significant effect on the fire resistance limit. The specimen with fire protection had a fire resistance limit of more than 180 minutes which was at least twice as long as the specimen without fire protection.
In order to investigate the fire resistance of double-skin multi-cavity composite wall with steel truss, two specimens were tested exposed to one-side ISO-834 standard fire. A specimen was unprotected and the other was protected by thick coated fireproof coating with a thickness of 20 mm. The test results indicated that: 1)the bare specimen reached the fire resistance limit due to the failure of thermal insulation; 2)the thickness of fireproof coating had a significant effect on the fire resistance limit. The specimen with fire protection had a fire resistance limit of more than 180 minutes which was at least twice as long as the specimen without fire protection.
2020, 50(3): 29-35.
doi: 10.13204/j.gyjz202003006
Abstract:
The key to the earthquake-resilience is to ensure that the main components of the joint do not undergo plastic deformation, so after earthquake, the joint function can be restored by replacing the replaceable members. On that basis, a new type of joint called earthquake-resilient prefabricated opening-web channel beam-column joint was proposed. The cantilever beam and the opening-web channel beam were connected by flange cover plates and web connecting plates. The flange of the cantilever beam was strengthened and the flange cover plates were weakened like dog bone, so the plastic hinge could be transferred to the flange cover plates effectively. A total of 5 different numerical examples were designed for finite element analysis, mainly to investigate the influence of the thickness of the flange cover plates, the middle bolts interval, the width of dog bone weakening section and the number of bolts on the mechanical properties and earthquake-resilience of joints. The load-displacement curve, failure modes of joints, relative slip curve, stress curves were analyzed in detail. The results showed that this new type of joint had good bearing capacity and could meet the requirements of earthquake-resilience. The dog bone weakening of flange cover plates could realize the damage control effectively. The thickness of flange cover plates mainly affected the yield load and peak load of the joint. However, the middle bolts interval would affect the peak load of the joint, not the yield load.
The key to the earthquake-resilience is to ensure that the main components of the joint do not undergo plastic deformation, so after earthquake, the joint function can be restored by replacing the replaceable members. On that basis, a new type of joint called earthquake-resilient prefabricated opening-web channel beam-column joint was proposed. The cantilever beam and the opening-web channel beam were connected by flange cover plates and web connecting plates. The flange of the cantilever beam was strengthened and the flange cover plates were weakened like dog bone, so the plastic hinge could be transferred to the flange cover plates effectively. A total of 5 different numerical examples were designed for finite element analysis, mainly to investigate the influence of the thickness of the flange cover plates, the middle bolts interval, the width of dog bone weakening section and the number of bolts on the mechanical properties and earthquake-resilience of joints. The load-displacement curve, failure modes of joints, relative slip curve, stress curves were analyzed in detail. The results showed that this new type of joint had good bearing capacity and could meet the requirements of earthquake-resilience. The dog bone weakening of flange cover plates could realize the damage control effectively. The thickness of flange cover plates mainly affected the yield load and peak load of the joint. However, the middle bolts interval would affect the peak load of the joint, not the yield load.
2020, 50(3): 36-42.
doi: 10.13204/j.gyjz202003007
Abstract:
In order to avoid the interaction between flange cover plates and floor, a kind of earthquake-resilient ductility-reinforced prefabricated opening-web steel channel beam-column joint based on the concept of damage control and buckling-restrain was proposed in the paper. Inner flange cover plates and U-shaped web connecting plates were used to connect the cantilever beam and the opening-web steel channel beam. The flange of the cantilever beam was strengthened and the flange cover plates were weakened like dog bone, so the plastic hinge was transferred to the flange cover plates effectively. A total of four examples with different parameters were calculated by finite element method. The influence of the parameters such as the thickness of the flange cover plates, the width of the dog bone weakening section and the number of connecting bolts on the mechanical properties of the joints was mainly studied. By analyzing the load-displacement curves, stress nephogram of joints, stress distribution of components and bolt tension curves obtained by finite element numerical simulation, the paper demonstrated that by setting the relevant parameters reasonably, the earthquake-resilient ductility-reinforced prefabricated opening-web steel channel beam-column joint had good bearing capacity and plastic rotation capacity, and could transfer the plastic hinge outward to the replaceable inner flange cover plates, meeting the design expectation that the joint function could be restored by replacing the local components after the earthquake. U-shaped web connecting plates could produce the effect of secondary reinforcement to the joint and improve the ductility of the joint effectively.
In order to avoid the interaction between flange cover plates and floor, a kind of earthquake-resilient ductility-reinforced prefabricated opening-web steel channel beam-column joint based on the concept of damage control and buckling-restrain was proposed in the paper. Inner flange cover plates and U-shaped web connecting plates were used to connect the cantilever beam and the opening-web steel channel beam. The flange of the cantilever beam was strengthened and the flange cover plates were weakened like dog bone, so the plastic hinge was transferred to the flange cover plates effectively. A total of four examples with different parameters were calculated by finite element method. The influence of the parameters such as the thickness of the flange cover plates, the width of the dog bone weakening section and the number of connecting bolts on the mechanical properties of the joints was mainly studied. By analyzing the load-displacement curves, stress nephogram of joints, stress distribution of components and bolt tension curves obtained by finite element numerical simulation, the paper demonstrated that by setting the relevant parameters reasonably, the earthquake-resilient ductility-reinforced prefabricated opening-web steel channel beam-column joint had good bearing capacity and plastic rotation capacity, and could transfer the plastic hinge outward to the replaceable inner flange cover plates, meeting the design expectation that the joint function could be restored by replacing the local components after the earthquake. U-shaped web connecting plates could produce the effect of secondary reinforcement to the joint and improve the ductility of the joint effectively.
2020, 50(3): 43-50.
doi: 10.13204/j.gyjz202003008
Abstract:
Based on the ideas of damage control and buckling-restrain, the paper proposed a kind of earthquake-resilient ductility-reinforced prefabricated opening-web steel channel beam-column joint. The seismic behavior of 4 examples was studied by finite element method. The hysteretic curves, failure modes, stress distribution and relative displacement curves of the plates were obtained. The influence of the parameters such as the thickness of the flange cover plates, the width of the dog bone weakening section and the number of bolts on the seismic behavior of the joint was emphatically studied. The results showed that the bearing capacity and seismic behavior of the joint were good. The plastic hinge could be transferred to the flange cover plates effectively, at the same time, the main components such as beam and column were basically elastic at the elastic stage. Therefore, the function of joint could be restored by replacing the connecting device after earthquake. The U-shaped web connecting plates could effectively restrain the buckling deformation of the inner flange cover plates, and improve the ductility of the joint. In addition, parameters which had a great influence on the seismic performance of joints such as thickness of inner flange cover plates, width of dog bone weakening section and number of bolts should be designed reasonably.
Based on the ideas of damage control and buckling-restrain, the paper proposed a kind of earthquake-resilient ductility-reinforced prefabricated opening-web steel channel beam-column joint. The seismic behavior of 4 examples was studied by finite element method. The hysteretic curves, failure modes, stress distribution and relative displacement curves of the plates were obtained. The influence of the parameters such as the thickness of the flange cover plates, the width of the dog bone weakening section and the number of bolts on the seismic behavior of the joint was emphatically studied. The results showed that the bearing capacity and seismic behavior of the joint were good. The plastic hinge could be transferred to the flange cover plates effectively, at the same time, the main components such as beam and column were basically elastic at the elastic stage. Therefore, the function of joint could be restored by replacing the connecting device after earthquake. The U-shaped web connecting plates could effectively restrain the buckling deformation of the inner flange cover plates, and improve the ductility of the joint. In addition, parameters which had a great influence on the seismic performance of joints such as thickness of inner flange cover plates, width of dog bone weakening section and number of bolts should be designed reasonably.
2020, 50(3): 51-57.
doi: 10.13204/j.gyjz202003009
Abstract:
Based on the analysis of the characteristics of existing natural ventilation performance optimization methods, the optimization process based on response surface suitable for design stage was proposed. The core steps were: parameter sensitivity analysis, experimental design, response surface model construction, multi-objective optimization, and collaborative optimization platform was established by using ANSYS Workbench. Taking the typical space model of the National Fitness Center as an example, 11 geometric parameters were explored as input variables, and the air age, temperature and wind speed were selected as the optimization targets. By using the parametric modeling technology and CFD numerical simulation technology, 200 sets of data were obtained, and the response surface model was constructed by Kriging algorithm. The genetic algorithm was used to call the response surface model data for fast optimization, and finally the optimization candidates and the optimization interval of each geometric parameter were obtained.
Based on the analysis of the characteristics of existing natural ventilation performance optimization methods, the optimization process based on response surface suitable for design stage was proposed. The core steps were: parameter sensitivity analysis, experimental design, response surface model construction, multi-objective optimization, and collaborative optimization platform was established by using ANSYS Workbench. Taking the typical space model of the National Fitness Center as an example, 11 geometric parameters were explored as input variables, and the air age, temperature and wind speed were selected as the optimization targets. By using the parametric modeling technology and CFD numerical simulation technology, 200 sets of data were obtained, and the response surface model was constructed by Kriging algorithm. The genetic algorithm was used to call the response surface model data for fast optimization, and finally the optimization candidates and the optimization interval of each geometric parameter were obtained.
2020, 50(3): 58-63,83.
doi: 10.13204/j.gyjz202003010
Abstract:
As the carrier of Mongolian nomadic culture, mongolian yurt embodies prefabricated construction concept in structure or the way of building and dismantling. In the future, Mongolian construction development should integrate the prefabricated construction concept to optimize and update the traditional mongolian yurts. The paper explored how to integrate the prefabricated construction concept with the traditional mongolian yurt design concept by introducing the design concept of the yurt for the A La Tan Hua tribe tourism planning. The main idea of the scheme was to skillfully incorporate prefabricated construction concept, the traditional yurt design concept, and modern ecological energy-saving technology, while fully considering the space needs of modern herders, to create a green, low-carbon suitable and environmentally friendly new prefabricated mongolian yurt for modern herders.
As the carrier of Mongolian nomadic culture, mongolian yurt embodies prefabricated construction concept in structure or the way of building and dismantling. In the future, Mongolian construction development should integrate the prefabricated construction concept to optimize and update the traditional mongolian yurts. The paper explored how to integrate the prefabricated construction concept with the traditional mongolian yurt design concept by introducing the design concept of the yurt for the A La Tan Hua tribe tourism planning. The main idea of the scheme was to skillfully incorporate prefabricated construction concept, the traditional yurt design concept, and modern ecological energy-saving technology, while fully considering the space needs of modern herders, to create a green, low-carbon suitable and environmentally friendly new prefabricated mongolian yurt for modern herders.
RESEARCH ON RECONSTRUCTION AND REUSE OF OLD INDUSTRIAL STRUCTURES FROM THE PERSPECTIVE OF EXPERIENCE
2020, 50(3): 64-68.
doi: 10.13204/j.gyjz202003011
Abstract:
Old industrial structures are an important part of industrial heritage, and their reconstruction and reuse are of great significance for recording industrial civilization and improving urban vitality. From the perspective of users’ experience, the paper analyzed three kinds of experience forms that were common in the reconstruction of old industrial structures, including landscape experience, cultural experience, and space experience, and proposed the reconstruction and reuse strategies for the old industrial structures from the perspective of experience, so as to provide some new thinking.
Old industrial structures are an important part of industrial heritage, and their reconstruction and reuse are of great significance for recording industrial civilization and improving urban vitality. From the perspective of users’ experience, the paper analyzed three kinds of experience forms that were common in the reconstruction of old industrial structures, including landscape experience, cultural experience, and space experience, and proposed the reconstruction and reuse strategies for the old industrial structures from the perspective of experience, so as to provide some new thinking.
2020, 50(3): 69-75.
doi: 10.13204/j.gyjz202003012
Abstract:
Based on the experimental study of two ultra-high performance concrete (UHPC) steel truss composite slabs and a concrete slab,the effect of steel truss on the flexural behavior of the UHPC composite slabs,such as deflection, cracks and concrete strain,was analyzed.And the secondary loaded effect of the UHPC steel truss composite slabs was investigated.The study showed that the UHPC steel truss composite slabs had better flexural behavior than ordinary concrete composite slabs.The section strain basically conformed to the plane hypothesis,the ductility was better, and the secondary stress was not obvious.The steel truss could effectively enhance the overall flexural bearing capacity of composite slabs, and weaken the phenomena of "stress excess" of tensile steel and the phenomena of "strain lag" of compressive concrete. The results, which were calculated by the formula of flexural normal section bearing capacity of steel truss UHPC composite slabs, agreed well with the experimental data when the equivalent tensile effect coefficient k3 of concrete was 0.35.
Based on the experimental study of two ultra-high performance concrete (UHPC) steel truss composite slabs and a concrete slab,the effect of steel truss on the flexural behavior of the UHPC composite slabs,such as deflection, cracks and concrete strain,was analyzed.And the secondary loaded effect of the UHPC steel truss composite slabs was investigated.The study showed that the UHPC steel truss composite slabs had better flexural behavior than ordinary concrete composite slabs.The section strain basically conformed to the plane hypothesis,the ductility was better, and the secondary stress was not obvious.The steel truss could effectively enhance the overall flexural bearing capacity of composite slabs, and weaken the phenomena of "stress excess" of tensile steel and the phenomena of "strain lag" of compressive concrete. The results, which were calculated by the formula of flexural normal section bearing capacity of steel truss UHPC composite slabs, agreed well with the experimental data when the equivalent tensile effect coefficient k3 of concrete was 0.35.
2020, 50(3): 76-83.
doi: 10.13204/j.gyjz202003013
Abstract:
Slab-rib form is one of the important factors that affects the bending fatigue behavior of precast prestressed concrete composite slab.In order to study the effect of slab-rib form on bending fatigue behavior of composite slab, a comparative test of bending fatigue of one T-shaped ribbed plate composite plate specimen and four rectangular ribbed plate composite plate specimens was carried out. The parameters include slab-rib form and fatigue load amplitude. The failure mode, crack distribution, load-deflection curve, load-strain relation curve were obtained. The influence of slab-rib form and fatigue load amplitude on fatigue damage degree of composite slab was analyzed. The results showed that the fatigue bending stiffness of the plate decreased obviously and the fatigue damage increased obviously with the increase of fatigue load amplitude. However, the fatigue damage of superimposed surface was relatively small, which indicated that the existence of superimposed surface would not affect the mechanical propcrties of composite slab. The bending fatigue behaviors of rectangular ribbed composite slab was the same as that of T-shaped ribbed plate.
Slab-rib form is one of the important factors that affects the bending fatigue behavior of precast prestressed concrete composite slab.In order to study the effect of slab-rib form on bending fatigue behavior of composite slab, a comparative test of bending fatigue of one T-shaped ribbed plate composite plate specimen and four rectangular ribbed plate composite plate specimens was carried out. The parameters include slab-rib form and fatigue load amplitude. The failure mode, crack distribution, load-deflection curve, load-strain relation curve were obtained. The influence of slab-rib form and fatigue load amplitude on fatigue damage degree of composite slab was analyzed. The results showed that the fatigue bending stiffness of the plate decreased obviously and the fatigue damage increased obviously with the increase of fatigue load amplitude. However, the fatigue damage of superimposed surface was relatively small, which indicated that the existence of superimposed surface would not affect the mechanical propcrties of composite slab. The bending fatigue behaviors of rectangular ribbed composite slab was the same as that of T-shaped ribbed plate.
2020, 50(3): 84-87,113.
doi: 10.13204/j.gyjz202003014
Abstract:
The most common forms of construction systems in cross-laminated timber (CLT) are platform construction and balloon construction. In order to investigate the effect of construction type on lateral performance of CLT walls, two CLT walls with different construction types (i.e., platform construction and balloon construction) were tested under reversed cyclic loading. Based on the experimental results, the failure mode, peak capacity, elastic stiffness and energy dissipation of the two CLT walls were compared. The results showed that more damage was suffered by the self-tapping screws connected to foundation beam in CLT walls with balloon construction than platform construction. The structural integrity and energy-dissipating capacity of CLT walls with balloon construction were better than those of CLT walls with platform construction. The peak capacity of CLT walls with two construction types were both greatly affected by the performance of connections connected to the foundation beam.
The most common forms of construction systems in cross-laminated timber (CLT) are platform construction and balloon construction. In order to investigate the effect of construction type on lateral performance of CLT walls, two CLT walls with different construction types (i.e., platform construction and balloon construction) were tested under reversed cyclic loading. Based on the experimental results, the failure mode, peak capacity, elastic stiffness and energy dissipation of the two CLT walls were compared. The results showed that more damage was suffered by the self-tapping screws connected to foundation beam in CLT walls with balloon construction than platform construction. The structural integrity and energy-dissipating capacity of CLT walls with balloon construction were better than those of CLT walls with platform construction. The peak capacity of CLT walls with two construction types were both greatly affected by the performance of connections connected to the foundation beam.
2020, 50(3): 88-95.
doi: 10.13204/j.gyjz202003015
Abstract:
To analyze the influencing factors of bearing capacity of joints in segmental columns, the numerical analysis method of mechanical properties of segmental columns was proposed. Comprehensive parametric analysis was then conducted to obtain the influence of the factors such as axial compression force, stirrup ratio, initial tension stress of prestressing tendons, and strength of mortar layer. The results indicated that: the stress features of the segmental columns in different stages could be satisfactorily reflected by the numerical analysis method under axial-flexure-shear coupling behavior; when the design axial compression ratio increased from 13% to 33%, the ultimate bearing capacity of the joints in coventionally reinforced concrete segmental columns increased by 40.3%, and the ultimate bearing capacity of the joints in prestressed concrete segmental columns increased by 17.8%; increasing the initial prestressing stress of prestressing tendons could improve the bearing capacity of joints to a lesser degree; when the strength grade of the mortar layer decreased from C80 to C40, the ultimate bearing capacity of the joints decreased by 19.7%.
To analyze the influencing factors of bearing capacity of joints in segmental columns, the numerical analysis method of mechanical properties of segmental columns was proposed. Comprehensive parametric analysis was then conducted to obtain the influence of the factors such as axial compression force, stirrup ratio, initial tension stress of prestressing tendons, and strength of mortar layer. The results indicated that: the stress features of the segmental columns in different stages could be satisfactorily reflected by the numerical analysis method under axial-flexure-shear coupling behavior; when the design axial compression ratio increased from 13% to 33%, the ultimate bearing capacity of the joints in coventionally reinforced concrete segmental columns increased by 40.3%, and the ultimate bearing capacity of the joints in prestressed concrete segmental columns increased by 17.8%; increasing the initial prestressing stress of prestressing tendons could improve the bearing capacity of joints to a lesser degree; when the strength grade of the mortar layer decreased from C80 to C40, the ultimate bearing capacity of the joints decreased by 19.7%.
2020, 50(3): 96-101,108.
doi: 10.13204/j.gyjz202003016
Abstract:
The traditional sand drain consolidation theory does not consider the significant rheological properties of soft clay and the non-Darcy characteristics of flow, which often leads to a large deviation between the calculated results and the observations. In order to further investigate the consolidation mechanism of sand drain ground in soft clay area, the nonlinear deformation of soil and the non-Darcy characteristics of flow were described by introducing uniform hardening (UH) constitutive model considering time effect and Hansbo's flow model, respectively. The consolidation equation of sand drain ground under the Barron's free strain assumption was modified without consideration of the well resistance and smear effect, and its numerical solutions were obtained by using the implicit finite difference method. The validity of the proposed method was verified by comparison with Berry's explicit numerical solutions. Based on that, the influence of soil viscosity and Hansbo's flow parameters on the nonlinear consolidation process of sand drain ground was analyzed. The numerical results showed that the viscosity of soft clay caused an increase in the pore pressure near the boundary of the influence zone of the sand filled drainage well at the early stage of consolidation, and the phenomenon became more obvious with the increase of viscosity. Meanwhile, Hansbo's flow enhanced the phenomenon of increased pore water pressure. However, at the middle and late stages of consolidation, the viscosity of the soil and the non-Darcy behaviour of the flow would delay the overall dissipation of pore water pressure in the ground with sand drains.
The traditional sand drain consolidation theory does not consider the significant rheological properties of soft clay and the non-Darcy characteristics of flow, which often leads to a large deviation between the calculated results and the observations. In order to further investigate the consolidation mechanism of sand drain ground in soft clay area, the nonlinear deformation of soil and the non-Darcy characteristics of flow were described by introducing uniform hardening (UH) constitutive model considering time effect and Hansbo's flow model, respectively. The consolidation equation of sand drain ground under the Barron's free strain assumption was modified without consideration of the well resistance and smear effect, and its numerical solutions were obtained by using the implicit finite difference method. The validity of the proposed method was verified by comparison with Berry's explicit numerical solutions. Based on that, the influence of soil viscosity and Hansbo's flow parameters on the nonlinear consolidation process of sand drain ground was analyzed. The numerical results showed that the viscosity of soft clay caused an increase in the pore pressure near the boundary of the influence zone of the sand filled drainage well at the early stage of consolidation, and the phenomenon became more obvious with the increase of viscosity. Meanwhile, Hansbo's flow enhanced the phenomenon of increased pore water pressure. However, at the middle and late stages of consolidation, the viscosity of the soil and the non-Darcy behaviour of the flow would delay the overall dissipation of pore water pressure in the ground with sand drains.
2020, 50(3): 102-108.
doi: 10.13204/j.gyjz202003017
Abstract:
T-shaped deep cement mixing (DCM) column is a new type of DCM column with an enlarged column cap. Based on the equal vertical strain assumption, the equations governing consolidation of the surrounding soil around a fully penetrated T-shaped DCM column was derived under instantaneous load. The corresponding analytical solutions were developed by using the one dimensional consolidation theory of a double-layer ground. Then, the accuracy of the proposed analytical solution was evaluated through the comparison of the consolidation rates of the composite ground from the proposed analytical solution with the FEA. Finally, the main influence factors were analyzed to investigate the consolidation behavior of the composite ground. The results showed that the consolidation rate of the composite ground increased with an increase in the constrained modulus of T-shaped DCM column, the area replacement ratio of the DCM column with small diameter under the enlarged cap and the constrained modulus of the subsoil around it. It decreased slightly with the increase of the diameter of the column cap. The length of the column cap had little influence on the consolidation rate when it was less than half of the length of a T-shaped DCM column. However, it increased rapidly with the increase of the column cap length when the column cap length is larger than half of that of a T-shaped DCM column.
T-shaped deep cement mixing (DCM) column is a new type of DCM column with an enlarged column cap. Based on the equal vertical strain assumption, the equations governing consolidation of the surrounding soil around a fully penetrated T-shaped DCM column was derived under instantaneous load. The corresponding analytical solutions were developed by using the one dimensional consolidation theory of a double-layer ground. Then, the accuracy of the proposed analytical solution was evaluated through the comparison of the consolidation rates of the composite ground from the proposed analytical solution with the FEA. Finally, the main influence factors were analyzed to investigate the consolidation behavior of the composite ground. The results showed that the consolidation rate of the composite ground increased with an increase in the constrained modulus of T-shaped DCM column, the area replacement ratio of the DCM column with small diameter under the enlarged cap and the constrained modulus of the subsoil around it. It decreased slightly with the increase of the diameter of the column cap. The length of the column cap had little influence on the consolidation rate when it was less than half of the length of a T-shaped DCM column. However, it increased rapidly with the increase of the column cap length when the column cap length is larger than half of that of a T-shaped DCM column.
2020, 50(3): 109-113.
doi: 10.13204/j.gyjz202003018
Abstract:
Freeze-thaw cycling is one of the main factors influencing the micro-structure and strength of fiber-reinforced cemented soil. A series of unconfined compression tests and freeze-thaw tests were conducted on basalt fiber-reinforced cemented clay specimens to investigate the effects of the number of freeze-thaw cycles, the curing time and the fiber length. The results showed that the strength of cemented soil continued to increase with increasing curing time. The strength of cemented soil was improved when the fiber was added. As the number of freeze-thaw cycles increased, cracks began to appear on the surface of the cemented soil. Obvious cracks appeared on the surface of the cemented soil without fiber after being subjected to 3 freeze-thaw cycles. Then, penetrating cracks appeared in the cemented soil without fiber, and the cemented soil completely lost its bearing capacity after being subjected to 6 freeze-thaw cycles; in contrast, cracks began to appear on the surface of cemented soil with fiber after being subjected to 6 cycles. As the number of freeze-thaw cycles increased, the strength of the fiber-reinforced cemented soil tended to decrease. The strength of cemented soil without fiber decreased the most. The relationship between the strength and the number of freeze-thaw cycles was linear. With the increase of the number of freeze-thaw cycles, the fiber length had less and less influence on the strength. The research indicated that the strength of cemented soil could be effectively improved when fiber was added. Although the strength of a fiber-reinforced cemented soil decreased as the number of freeze-thaw cycles increased, the strength loss decreased, and the frost resistance of a cemented soil was improved when the basalt fiber was added.
Freeze-thaw cycling is one of the main factors influencing the micro-structure and strength of fiber-reinforced cemented soil. A series of unconfined compression tests and freeze-thaw tests were conducted on basalt fiber-reinforced cemented clay specimens to investigate the effects of the number of freeze-thaw cycles, the curing time and the fiber length. The results showed that the strength of cemented soil continued to increase with increasing curing time. The strength of cemented soil was improved when the fiber was added. As the number of freeze-thaw cycles increased, cracks began to appear on the surface of the cemented soil. Obvious cracks appeared on the surface of the cemented soil without fiber after being subjected to 3 freeze-thaw cycles. Then, penetrating cracks appeared in the cemented soil without fiber, and the cemented soil completely lost its bearing capacity after being subjected to 6 freeze-thaw cycles; in contrast, cracks began to appear on the surface of cemented soil with fiber after being subjected to 6 cycles. As the number of freeze-thaw cycles increased, the strength of the fiber-reinforced cemented soil tended to decrease. The strength of cemented soil without fiber decreased the most. The relationship between the strength and the number of freeze-thaw cycles was linear. With the increase of the number of freeze-thaw cycles, the fiber length had less and less influence on the strength. The research indicated that the strength of cemented soil could be effectively improved when fiber was added. Although the strength of a fiber-reinforced cemented soil decreased as the number of freeze-thaw cycles increased, the strength loss decreased, and the frost resistance of a cemented soil was improved when the basalt fiber was added.
2020, 50(3): 114-118,146.
doi: 10.13204/j.gyjz202003019
Abstract:
Through pull-out tests of 12 groups bonding specimens of steel strand and UHPC,the failure mode and mechanism of the slip-breaking specimen with splitting crack in the whole process were emphatically analyzed, and then the effects of protective layer thickness and anchorage length on ultimate load were discussed, whereafter, the formula for calculating the ultimate bond strength and anchor length when the thickness of the protective layer was 2 times the diameter of the steel strand was fitted by the least squares method. The results showed that the number of cracks and crack width between steel strand and UHPC were significantly less those that between steel strand and ordinary concrete on account of steel fiber which could restrain the crack development and increase the splitting strength of UHPC specimens.The ultimate load increased when the thickness of the protective layer and the anchorage length increased. The polynomial fitting method was used to obtain the critical anchoring formula of steel strand in UHPC, and the anchorage length was recommended to be 35d.
Through pull-out tests of 12 groups bonding specimens of steel strand and UHPC,the failure mode and mechanism of the slip-breaking specimen with splitting crack in the whole process were emphatically analyzed, and then the effects of protective layer thickness and anchorage length on ultimate load were discussed, whereafter, the formula for calculating the ultimate bond strength and anchor length when the thickness of the protective layer was 2 times the diameter of the steel strand was fitted by the least squares method. The results showed that the number of cracks and crack width between steel strand and UHPC were significantly less those that between steel strand and ordinary concrete on account of steel fiber which could restrain the crack development and increase the splitting strength of UHPC specimens.The ultimate load increased when the thickness of the protective layer and the anchorage length increased. The polynomial fitting method was used to obtain the critical anchoring formula of steel strand in UHPC, and the anchorage length was recommended to be 35d.
2020, 50(3): 119-123.
doi: 10.13204/j.gyjz202003020
Abstract:
In order to better understand the capillary water absorption characteristics of concrete, the influence of different types of concrete, steel fiber content, and curing conditions on the solution absorption amount were studied in the paper. The capillary water absorption coefficients were also obtained. Moreover, the relationship between pore structure and capillary water absorption coefficient was analyzed. The results showed that the two stages, 15~180 min and 180~480 min, of solution absorption amount of different types of concrete (damage and undamaged) were linear with t1/2. The capillary water absorption coefficient of ultra-high performance concrete (UHPC) was much smaller than that of high-performance concrete (HPC). With the increase of the steel fiber content, the solution absorption amount of the first stage and the capillary water absorption coefficients of UHPC both increased. Under the influence of rehydration, the solution absorption amount of UHPC specimens cured in water was slightly larger than that cured in the room condition at the age of 720 d. The capillary water absorption coefficient was mainly affected by the pore content in the range of 100~3 nm, and the capillary water absorption coefficient in the first stage increased with the increase of its content. Considering the influence of porosity, the cumulative capillary water absorption height was calculated, and the calculation results were in accordance with the actual situation.
In order to better understand the capillary water absorption characteristics of concrete, the influence of different types of concrete, steel fiber content, and curing conditions on the solution absorption amount were studied in the paper. The capillary water absorption coefficients were also obtained. Moreover, the relationship between pore structure and capillary water absorption coefficient was analyzed. The results showed that the two stages, 15~180 min and 180~480 min, of solution absorption amount of different types of concrete (damage and undamaged) were linear with t1/2. The capillary water absorption coefficient of ultra-high performance concrete (UHPC) was much smaller than that of high-performance concrete (HPC). With the increase of the steel fiber content, the solution absorption amount of the first stage and the capillary water absorption coefficients of UHPC both increased. Under the influence of rehydration, the solution absorption amount of UHPC specimens cured in water was slightly larger than that cured in the room condition at the age of 720 d. The capillary water absorption coefficient was mainly affected by the pore content in the range of 100~3 nm, and the capillary water absorption coefficient in the first stage increased with the increase of its content. Considering the influence of porosity, the cumulative capillary water absorption height was calculated, and the calculation results were in accordance with the actual situation.
2020, 50(3): 124-130,141.
doi: 10.13204/j.gyjz202003021
Abstract:
At present, the research on mix proportion of ultra-high performance concrete (UHPC) focus on reactive powder concrete (RPC), and the incorporation of coarse aggregate in RPC can reduce the cost and the shrinkage of concrete, but the research on the mix proportion of CA-UHPC is relatively less. The paper discussed the influence of raw materials, production costs and production processes on the development and application of UHPC, and proposed a more economical and reasonable design of UHPC mix proportion. Under the simulated construction environment and simplifying the curing process, by manufacturing 38 sets of UHPC cube test blocks, the water-binder ratio, silica fume content, steel fiber content, coarse aggregate content and curing condition were studied. The influence rules of these factors on the compressive strength of UHPC were given and the reasons were analyzed. In addition, according to the test results, the optimum steel fiber content and coarse aggregate content were given.
At present, the research on mix proportion of ultra-high performance concrete (UHPC) focus on reactive powder concrete (RPC), and the incorporation of coarse aggregate in RPC can reduce the cost and the shrinkage of concrete, but the research on the mix proportion of CA-UHPC is relatively less. The paper discussed the influence of raw materials, production costs and production processes on the development and application of UHPC, and proposed a more economical and reasonable design of UHPC mix proportion. Under the simulated construction environment and simplifying the curing process, by manufacturing 38 sets of UHPC cube test blocks, the water-binder ratio, silica fume content, steel fiber content, coarse aggregate content and curing condition were studied. The influence rules of these factors on the compressive strength of UHPC were given and the reasons were analyzed. In addition, according to the test results, the optimum steel fiber content and coarse aggregate content were given.
2020, 50(3): 131-135.
doi: 10.13204/j.gyjz202003022
Abstract:
Taking the natural dry hanging stone which has been commonly used in stone curtain wall engineering as an example, under freeze-thaw cydes, the changes of compressive strength and flexural strength of granite, limestone and sandstone with different water absorption and protective treatments were studied through tests, the test results showed that the protective treatment could promote the frost resistance of the stone.By conducting different numbers of freeze-thaw cycling test at the same time, the frost resistance coefficients of three kinds of stones as the change of freeze-thaw cycles was compared and analyzed, the fitting curves of frost resistance coefficient and the number of freezing and thawing cycles were obtained, the attenuation law of frost resistance coefficient with the number of freeze-thaw cycles was obtained and the minimum number of freeze-thaw cycles of three kinds of commonly-used stones occurred damage was predicted.
Taking the natural dry hanging stone which has been commonly used in stone curtain wall engineering as an example, under freeze-thaw cydes, the changes of compressive strength and flexural strength of granite, limestone and sandstone with different water absorption and protective treatments were studied through tests, the test results showed that the protective treatment could promote the frost resistance of the stone.By conducting different numbers of freeze-thaw cycling test at the same time, the frost resistance coefficients of three kinds of stones as the change of freeze-thaw cycles was compared and analyzed, the fitting curves of frost resistance coefficient and the number of freezing and thawing cycles were obtained, the attenuation law of frost resistance coefficient with the number of freeze-thaw cycles was obtained and the minimum number of freeze-thaw cycles of three kinds of commonly-used stones occurred damage was predicted.
2020, 50(3): 136-141.
doi: 10.13204/j.gyjz202003023
Abstract:
The method of adding fiber into concrete has been commonly used in engineering to improve the crack resistance of concrete. The flake is a micron-sized material with good mechanical properties and corrosion resistance. In the paper, six groups of concrete flat plate tests, six groups of concrete flexural strength tests and six groups of acoustic emission tests were carried out by adding different contents of glass flake and basalt flake into concrete. The early crack resistance, mechanical properties after hardening, fracture process of concrete modified by flake and the change law of the development of the middle fracture were studied. The test results showed that flake could effectively reduce the early cracking area of concrete, improve the flexural strength, and mainly improve the micro-crack resistance of concrete.
The method of adding fiber into concrete has been commonly used in engineering to improve the crack resistance of concrete. The flake is a micron-sized material with good mechanical properties and corrosion resistance. In the paper, six groups of concrete flat plate tests, six groups of concrete flexural strength tests and six groups of acoustic emission tests were carried out by adding different contents of glass flake and basalt flake into concrete. The early crack resistance, mechanical properties after hardening, fracture process of concrete modified by flake and the change law of the development of the middle fracture were studied. The test results showed that flake could effectively reduce the early cracking area of concrete, improve the flexural strength, and mainly improve the micro-crack resistance of concrete.
2020, 50(3): 142-146.
doi: 10.13204/j.gyjz202003024
Abstract:
A new type of array combined formwork support system is composed of array aluminium frames, adjustable steel pipe supports, horizontal tubes and plastic templates. A single-span four-column frame unit was selected to perform a full-scale anti-overturning stability experiment on the formwork support system. The experiment results showed that the formwork support system remained stable and exhibited good lateral stiffness under horizontal load. It could meet the requirements of overall anti-overturning stability with the cooperation of beam and column formworks. On this basis, the finite element software MIDAS/Gen was used to establish a three-dimensional analysis model of the experiment frame structure considering the semi-rigidity of joints, and the geometric non-linear analysis was carried out. By comparison, the analysis results were generally consistent with the experimental data, which showed that the modeling and analysis methods in the paper were basically consistent with the actual stress state of the experiment frame structure. The inevitable or expected randomness of member quality, material defects, installation operation and connection construction had a certain effect on the overall stability of the formwork support system.
A new type of array combined formwork support system is composed of array aluminium frames, adjustable steel pipe supports, horizontal tubes and plastic templates. A single-span four-column frame unit was selected to perform a full-scale anti-overturning stability experiment on the formwork support system. The experiment results showed that the formwork support system remained stable and exhibited good lateral stiffness under horizontal load. It could meet the requirements of overall anti-overturning stability with the cooperation of beam and column formworks. On this basis, the finite element software MIDAS/Gen was used to establish a three-dimensional analysis model of the experiment frame structure considering the semi-rigidity of joints, and the geometric non-linear analysis was carried out. By comparison, the analysis results were generally consistent with the experimental data, which showed that the modeling and analysis methods in the paper were basically consistent with the actual stress state of the experiment frame structure. The inevitable or expected randomness of member quality, material defects, installation operation and connection construction had a certain effect on the overall stability of the formwork support system.
2020, 50(3): 147-150,123.
doi: 10.13204/j.gyjz202003025
Abstract:
Combined with the example of prefabricated steel structure construction, the prefabricated enclosure wallboard was studied. The thermal insulation performance of six kinds of composite wallboard was compared, and a box-type ALC+rock wool composite "sandwich" wallboard was selected for engineering application. The loading test of ALC composite wallboard was carried out, and the test results could meet the design requirements of mechanical properties. When the calculation formula was difficult to determine, it was recommended to determine the design value of wallboard resistance based on the test. The wallboard had been applied in engineering with good results.
Combined with the example of prefabricated steel structure construction, the prefabricated enclosure wallboard was studied. The thermal insulation performance of six kinds of composite wallboard was compared, and a box-type ALC+rock wool composite "sandwich" wallboard was selected for engineering application. The loading test of ALC composite wallboard was carried out, and the test results could meet the design requirements of mechanical properties. When the calculation formula was difficult to determine, it was recommended to determine the design value of wallboard resistance based on the test. The wallboard had been applied in engineering with good results.
2020, 50(3): 151-155.
doi: 10.13204/j.gyjz202003026
Abstract:
Beijing has long been at the forefront of the country in the field of academic research and engineering practice of industrial heritage. Over the past ten years, the development and utilization of industrial heritage (remains) has been in full swing, and its experience, characteristics and deficiencies are very representative. The paper reviewed and summarized the current status of Beijing's industrial heritage protection and utilization, and analyzed the experience and characteristics of Beijing, in order to make suggestions on the protection and reuse of industrial heritage in future.
Beijing has long been at the forefront of the country in the field of academic research and engineering practice of industrial heritage. Over the past ten years, the development and utilization of industrial heritage (remains) has been in full swing, and its experience, characteristics and deficiencies are very representative. The paper reviewed and summarized the current status of Beijing's industrial heritage protection and utilization, and analyzed the experience and characteristics of Beijing, in order to make suggestions on the protection and reuse of industrial heritage in future.
2020, 50(3): 156-159,135.
doi: 10.13204/j.gyjz202003027
Abstract:
For the semi-rigid joints of beams and columns connected by two T-shaped steel joints with different thicknesses, the variation of bolt pre-tightening force, hysteretic behavior and stiffness degradation were analyzed by experiments and finite element simulation methods. The results showed that during the quasi-static loading process, the bolt pre-tension attenuation on the column was slower than that on the beam; the increase of the thickness of the T-shaped steel could improve the strength, stiffness and energy dissipation performance of the joint. Degradation meant that an appropriate increase in the thickness of the joint could improve the seismic behavior of this type of joint.
For the semi-rigid joints of beams and columns connected by two T-shaped steel joints with different thicknesses, the variation of bolt pre-tightening force, hysteretic behavior and stiffness degradation were analyzed by experiments and finite element simulation methods. The results showed that during the quasi-static loading process, the bolt pre-tension attenuation on the column was slower than that on the beam; the increase of the thickness of the T-shaped steel could improve the strength, stiffness and energy dissipation performance of the joint. Degradation meant that an appropriate increase in the thickness of the joint could improve the seismic behavior of this type of joint.
2020, 50(3): 160-166.
doi: 10.13204/j.gyjz202003028
Abstract:
The bond behavior of GFRP bar in BFRP-confined concrete was experimentally investigated. 36 specimens were prepared for pull-out test. The test variables included the number of BFRP layers (0, 1, 2 and 3 layers of fiber fabric) and the compressive strength of concrete (40.6, 44.2 and 52.7 MPa). The test results indicated that for BFRP lateral confinement, the typical failure mode of specimens was changed from brittle splitting failure to ductile pull-out failure. The bond behavior between GFRP bars and concrete could be significantly improved due to the lateral confinement from the BFRP jacket. Compared with unconfined specimens, bond strength of confined specimens with one, two and three layers of BFRP increased by 25%~35%, 42%~56% and 52%~88%, respectively, corresponding to three different concrete strengths, and the average bond slip of FRP bars reaching to the bond strength increased by 47%~187%, 86%~267%, 168%~211%, respectively. The confinement from the outer BFRP jacket was activated when the bond stress of confined specimens approximately reached the bond strength of unconfined specimens. The radial confining stress corresponding to bond strength increased with the number of BFRP layers and the concrete strength. Under the same concrete strength conditions, the normalized bond strength of confined specimens approximately linearly increased with the increase of confinement stiffness ratio of BFRP.
The bond behavior of GFRP bar in BFRP-confined concrete was experimentally investigated. 36 specimens were prepared for pull-out test. The test variables included the number of BFRP layers (0, 1, 2 and 3 layers of fiber fabric) and the compressive strength of concrete (40.6, 44.2 and 52.7 MPa). The test results indicated that for BFRP lateral confinement, the typical failure mode of specimens was changed from brittle splitting failure to ductile pull-out failure. The bond behavior between GFRP bars and concrete could be significantly improved due to the lateral confinement from the BFRP jacket. Compared with unconfined specimens, bond strength of confined specimens with one, two and three layers of BFRP increased by 25%~35%, 42%~56% and 52%~88%, respectively, corresponding to three different concrete strengths, and the average bond slip of FRP bars reaching to the bond strength increased by 47%~187%, 86%~267%, 168%~211%, respectively. The confinement from the outer BFRP jacket was activated when the bond stress of confined specimens approximately reached the bond strength of unconfined specimens. The radial confining stress corresponding to bond strength increased with the number of BFRP layers and the concrete strength. Under the same concrete strength conditions, the normalized bond strength of confined specimens approximately linearly increased with the increase of confinement stiffness ratio of BFRP.
2020, 50(3): 167-171,166.
doi: 10.13204/j.gyjz202003029
Abstract:
Fiber-reinforced polymer (FRP) composite sandwich systems has the advantages of light weight, high strength, and long service life. Hybrid core systems were used to manufacture sandwich composites with higher performance. FRP composite sandwich panels with GFRP web-phenolic foam core systems were manufactured by vacuum-assisted molding process. Four-point bending tests were performed on three specimens with different core layers to study the bending properties and failure modes of FRP composite sandwich panels. The test results showed that the failure mode was shear failure, which was manifested in the form of peeling failure of web and surface layer, and buckling failure of web. Increasing the longitudinal web in the middle could significantly improve the bending capacity of the panel; increasing the transverse web could significantly control the damage degree of the panel. Using Timoshenko beam theory, considering the combined effects of bending and shear deformation, the mid-span deflection was analyzed; considering the contribution of the components in the hybrid core layer to the shear capacity, the ultimate bearing capacity was predicted, and the values agreed well with the measured values.
Fiber-reinforced polymer (FRP) composite sandwich systems has the advantages of light weight, high strength, and long service life. Hybrid core systems were used to manufacture sandwich composites with higher performance. FRP composite sandwich panels with GFRP web-phenolic foam core systems were manufactured by vacuum-assisted molding process. Four-point bending tests were performed on three specimens with different core layers to study the bending properties and failure modes of FRP composite sandwich panels. The test results showed that the failure mode was shear failure, which was manifested in the form of peeling failure of web and surface layer, and buckling failure of web. Increasing the longitudinal web in the middle could significantly improve the bending capacity of the panel; increasing the transverse web could significantly control the damage degree of the panel. Using Timoshenko beam theory, considering the combined effects of bending and shear deformation, the mid-span deflection was analyzed; considering the contribution of the components in the hybrid core layer to the shear capacity, the ultimate bearing capacity was predicted, and the values agreed well with the measured values.
2020, 50(3): 172-177.
doi: 10.13204/j.gyjz202003030
Abstract:
Through uniaxial compression tests on five groups of ECC (Engineered Cementitious Composites) prismatic specimens and one group of cement mortar matrix specimens, the effects of PVA (Polyvinyl Alcohol) fiber ratio and water-binder ratio on compressive properties of ECC were studied, as well as the characteristics of complete stress-strain curve of ECC under compression. The test results showed that the impact of PVA fiber volume content on prismatic compressive strength of ECC was not significant. The prismatic compressive strength of ECC increased with the decrease of the water-binder ratio. In addition, the elastic modulus of ECC prisms increased with an increase in compressive strength. Moreover, the PVA fiber volume content and water-binder ratio had little effect on the Poisson's ratio of ECC prisms, and the average value of Poisson's ratio of the ECC prisms was 0.27. Besides, based on the characteristics of complete test stress-strain curves of ECC under compression, the stress-strain relationship model of the ECC under axial compression was proposed, and the accuracy of the model was verified by comparison with the experimental results.
Through uniaxial compression tests on five groups of ECC (Engineered Cementitious Composites) prismatic specimens and one group of cement mortar matrix specimens, the effects of PVA (Polyvinyl Alcohol) fiber ratio and water-binder ratio on compressive properties of ECC were studied, as well as the characteristics of complete stress-strain curve of ECC under compression. The test results showed that the impact of PVA fiber volume content on prismatic compressive strength of ECC was not significant. The prismatic compressive strength of ECC increased with the decrease of the water-binder ratio. In addition, the elastic modulus of ECC prisms increased with an increase in compressive strength. Moreover, the PVA fiber volume content and water-binder ratio had little effect on the Poisson's ratio of ECC prisms, and the average value of Poisson's ratio of the ECC prisms was 0.27. Besides, based on the characteristics of complete test stress-strain curves of ECC under compression, the stress-strain relationship model of the ECC under axial compression was proposed, and the accuracy of the model was verified by comparison with the experimental results.
2020, 50(3): 178-181,189.
doi: 10.13204/j.gyjz202003031
Abstract:
The 3D laser scanning reverse modeling technology has been widely adopted in various fields of building construction due to its high efficiency, accuracy and low cost.However, 3D laser scanning belongs to measurement field while building information modeling belongs to construction field How to seamlessly connect two types of information techniques is worthy to explore by building information modeling. Using some common modeling softwares such as 3ds Max, Rhino, Revit and SketchUp, the paper probed into the realization method of reverse modeling with focus on its key links, and meanwhile explored the application range of several reverse modeling methods respectively according to the features and application requirements of each building information model built in reverse, which could provide a reference for BIM engineers. The realization method of building reverse modeling based on 3D laser scanning not only could achieve cross-discipline application from measurement software to building modeling software, but also enrich the application experience of Building Information Modeling Technology.
The 3D laser scanning reverse modeling technology has been widely adopted in various fields of building construction due to its high efficiency, accuracy and low cost.However, 3D laser scanning belongs to measurement field while building information modeling belongs to construction field How to seamlessly connect two types of information techniques is worthy to explore by building information modeling. Using some common modeling softwares such as 3ds Max, Rhino, Revit and SketchUp, the paper probed into the realization method of reverse modeling with focus on its key links, and meanwhile explored the application range of several reverse modeling methods respectively according to the features and application requirements of each building information model built in reverse, which could provide a reference for BIM engineers. The realization method of building reverse modeling based on 3D laser scanning not only could achieve cross-discipline application from measurement software to building modeling software, but also enrich the application experience of Building Information Modeling Technology.
2020, 50(3): 182-189.
doi: 10.13204/j.gyjz202003032
Abstract:
Tang Yang means building model sample of building in Qing dynasty. Tang Yang in the Forbidden City was used to be submitted to the emperor for preview. A Tang Yang can show the all-around information of a Qing dynasty building such as appearance, constitution, decoration, color and so on. The Tang Yang of Yanxi Palace indicated that the building characteristics of Lingzhao Veranda in Qing dynasty were very similar to those of other buildings in the Forbidden City. The Tang Yangs in the Forbidden City were made by Lei family, whose members of 7 generations contributed the design and construction of the emperors’ buildings in Qing dynasty. The scientific value of Tang Yang is that it can truly reflect the building information, its manufacture and installation are also convenient. Besides, it provides valuable historical information for buildings of Qing dynasty, and deeply represents the architectural culture of the palace buildings in Qing dynasty.
Tang Yang means building model sample of building in Qing dynasty. Tang Yang in the Forbidden City was used to be submitted to the emperor for preview. A Tang Yang can show the all-around information of a Qing dynasty building such as appearance, constitution, decoration, color and so on. The Tang Yang of Yanxi Palace indicated that the building characteristics of Lingzhao Veranda in Qing dynasty were very similar to those of other buildings in the Forbidden City. The Tang Yangs in the Forbidden City were made by Lei family, whose members of 7 generations contributed the design and construction of the emperors’ buildings in Qing dynasty. The scientific value of Tang Yang is that it can truly reflect the building information, its manufacture and installation are also convenient. Besides, it provides valuable historical information for buildings of Qing dynasty, and deeply represents the architectural culture of the palace buildings in Qing dynasty.
