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Steel Construction Published the List of Highly Influential Articles of 2020
2023 Vol. 38, No. 6
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2023, 38(6): 1-11.
doi: 10.13206/j.gjgS22110301
Abstract
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Abstract:
With the application and promotion of prefabricated structures in China, the application value of PEC members in engineering has been greatly improved due to its characteristics of convenient mass production and rapid assembly. Some companies begin to try to apply PEC members in actual projects, and proposed a novel shear wall-PEC shear wall. Three full-scale PEC shear wall specimens were designed based on engineering application, and tested under low-cycle pseudo-static horizontal loading.The test phenomenon and failure process of PEC shear wall were observed, and the failure mode and deformation characteristics under the reciprocating load were studied by analyzing the stress and strain conditions of key parts. The hysteretic curve, skeleton curve, energy dissipation capacity, ductility, bearing capacity, stiffness and other mechanical properties of PEC shear wall under the low cyclic loading were analyzed to evaluate its lateral resistance properties. The influence of the flange crimping construction on the failure characteristics, deformation and lateral resistance were compared to verify its validity. And the influence of the axial compression ratio on the lateral performance of PEC walls with crimping construction was analyzed. The test results show that: 1)all PEC shear wall specimens failed after yielding due to bending, and the steel flange yielded before reaching the maximum bearing capacity. The concrete collapse at the bottom of specimen SW1 caused local buckling of the steel flange, while the bottom steel flange of specimen SW2 and SW3 did not buckled, and finally the base anchoring failure occurred. 2)Specimen SW1 hysteresis curve of SW1 is full, which has strong ability of plastic energy dissipation; hysteresis curves of specimen SW2 and specimen SW3 have a certain degree of pinch phenomenon. The ductility indexes are greater than 3.4, which has good deformation ability. The deterioration of wall resistance is much limited, and stiffness degrades is at a slower rate during later loading stages. All of the specimens keep stable bearing capacity within 1/30 inter-story drift.3) The crimping construction efficiently confines the concrete at the bottom corner of the PEC shear wall, postpones the collapse of the concrete, and makes the PEC shear walls have better bearing capacity. 4)Under high axial compression ratio, the specimen will compressively yield earlier, while the initial stiffness of the PEC shear wall will increase somewhat, meanwhile, its ductility and energy dissipation capacity will be reduced. 5) The deformation capacity of PEC shear wall is closer to that of steel plate shear wall than that of concrete shear wall. The deformation limit for seismic design of PEC shear wall can be appropriately enlarged.
With the application and promotion of prefabricated structures in China, the application value of PEC members in engineering has been greatly improved due to its characteristics of convenient mass production and rapid assembly. Some companies begin to try to apply PEC members in actual projects, and proposed a novel shear wall-PEC shear wall. Three full-scale PEC shear wall specimens were designed based on engineering application, and tested under low-cycle pseudo-static horizontal loading.The test phenomenon and failure process of PEC shear wall were observed, and the failure mode and deformation characteristics under the reciprocating load were studied by analyzing the stress and strain conditions of key parts. The hysteretic curve, skeleton curve, energy dissipation capacity, ductility, bearing capacity, stiffness and other mechanical properties of PEC shear wall under the low cyclic loading were analyzed to evaluate its lateral resistance properties. The influence of the flange crimping construction on the failure characteristics, deformation and lateral resistance were compared to verify its validity. And the influence of the axial compression ratio on the lateral performance of PEC walls with crimping construction was analyzed. The test results show that: 1)all PEC shear wall specimens failed after yielding due to bending, and the steel flange yielded before reaching the maximum bearing capacity. The concrete collapse at the bottom of specimen SW1 caused local buckling of the steel flange, while the bottom steel flange of specimen SW2 and SW3 did not buckled, and finally the base anchoring failure occurred. 2)Specimen SW1 hysteresis curve of SW1 is full, which has strong ability of plastic energy dissipation; hysteresis curves of specimen SW2 and specimen SW3 have a certain degree of pinch phenomenon. The ductility indexes are greater than 3.4, which has good deformation ability. The deterioration of wall resistance is much limited, and stiffness degrades is at a slower rate during later loading stages. All of the specimens keep stable bearing capacity within 1/30 inter-story drift.3) The crimping construction efficiently confines the concrete at the bottom corner of the PEC shear wall, postpones the collapse of the concrete, and makes the PEC shear walls have better bearing capacity. 4)Under high axial compression ratio, the specimen will compressively yield earlier, while the initial stiffness of the PEC shear wall will increase somewhat, meanwhile, its ductility and energy dissipation capacity will be reduced. 5) The deformation capacity of PEC shear wall is closer to that of steel plate shear wall than that of concrete shear wall. The deformation limit for seismic design of PEC shear wall can be appropriately enlarged.
2023, 38(6): 12-21.
doi: 10.13206/j.gjgS22101102
Abstract:
Partially encased composite walls(PEC walls) have been widely used in the field of prefabricated buildings. In recent years, it has been gradually applied in building structures. However, the researches on the stability performance of PEC remain to be improved. In this paper, the stability performance of PEC wall under axial compression is studied. Based on the existing experiments, a finite element model is established. The influence of parameters such as calculation length, material strength, main steel section thickness and, section size of components on the wall stability is investigated, and the calculation formula of the PEC wall axial compression stability curve is proposed. The research shows that the calculated values of the formula are in good agreement with the finite element results. In this paper, the finite element software ABAQUS is used to establish a finite element analysis model, and the accuracy of the model is verified by existing experimental data. Then, this paper analyzes the the axial compression stability performance of PEC wall under parameters, and investigates the influence of different parameters on the stability performance of components, including calculated length, material strength, steel section thickness of the main steel parts, and the cross-sectional size of the components. The parameter analysis process adopts the control variable method to study the influence of each parameter on the stability performance of PEC wall, and summarize the mechanical characteristics and regulations. Then, based on the stability theory of the composite structure, the equivalent strength fEQ and equivalent elastic modulus EEQ of the composite section are comprehensively determined according to the composition of concrete and main steel parts in the composite section, and the regularized slenderness ratio λn of the PEC wall components is derived. Then, based on the results of finite element analysis, the axial stability curve of PEC wall is drawn, and the stability curves of four types of sections of steel structure are compared with the stability curve of PEC wall, the regulation is summarized, and the calculation method suitable for the stability curve of PEC wall components is found. Finally, based on the parameter analysis results, the influence of each component parameter on the stability curve of PEC wall is summarized, and the key component parameters are introduced as control variables in the calculation formula of the axial compression stability curve of PEC wall, and the calculation formula of the axial compression stability curve of the "three-stage" PEC wall is proposed based on the characteristics of the failure mode of the components under different calculated lengths. The results show that: 1) the calculated length l0 of the component has a great influence on the destruction form of PEC wall, and with the increase of l0, the destruction form of the component and its ultimate bearing capacity change from material strength control to overall stability control; 2) among the parameters of each component of PEC wall, the flange thickness and the section thickness of the main steel parts had significant effects on the stability performance, and the material strength, web thickness of the main steel parts, and the cross-sectional height of the components had relatively little effect on the stability performance; 3) the relevant specifications for PEC wall design have not been promulgated at home and abroad, and the four types of section stability curves provided by China′s current design code Steel Structure Design Standard(GB 50017—2017) are not applicable to the determination of the axial compressive stability coefficient of PEC wall; 4) the calculation formula of the axial compressive stability coefficient of PEC wall proposed in this paper is "three-stage". The calculated value of the formula is in good agreement with the finite element results, and can maintain high accuracy for PEC walls of different materials and sizes, which can be used to determine the axial compressive stability coefficient of PEC walls.
Partially encased composite walls(PEC walls) have been widely used in the field of prefabricated buildings. In recent years, it has been gradually applied in building structures. However, the researches on the stability performance of PEC remain to be improved. In this paper, the stability performance of PEC wall under axial compression is studied. Based on the existing experiments, a finite element model is established. The influence of parameters such as calculation length, material strength, main steel section thickness and, section size of components on the wall stability is investigated, and the calculation formula of the PEC wall axial compression stability curve is proposed. The research shows that the calculated values of the formula are in good agreement with the finite element results. In this paper, the finite element software ABAQUS is used to establish a finite element analysis model, and the accuracy of the model is verified by existing experimental data. Then, this paper analyzes the the axial compression stability performance of PEC wall under parameters, and investigates the influence of different parameters on the stability performance of components, including calculated length, material strength, steel section thickness of the main steel parts, and the cross-sectional size of the components. The parameter analysis process adopts the control variable method to study the influence of each parameter on the stability performance of PEC wall, and summarize the mechanical characteristics and regulations. Then, based on the stability theory of the composite structure, the equivalent strength fEQ and equivalent elastic modulus EEQ of the composite section are comprehensively determined according to the composition of concrete and main steel parts in the composite section, and the regularized slenderness ratio λn of the PEC wall components is derived. Then, based on the results of finite element analysis, the axial stability curve of PEC wall is drawn, and the stability curves of four types of sections of steel structure are compared with the stability curve of PEC wall, the regulation is summarized, and the calculation method suitable for the stability curve of PEC wall components is found. Finally, based on the parameter analysis results, the influence of each component parameter on the stability curve of PEC wall is summarized, and the key component parameters are introduced as control variables in the calculation formula of the axial compression stability curve of PEC wall, and the calculation formula of the axial compression stability curve of the "three-stage" PEC wall is proposed based on the characteristics of the failure mode of the components under different calculated lengths. The results show that: 1) the calculated length l0 of the component has a great influence on the destruction form of PEC wall, and with the increase of l0, the destruction form of the component and its ultimate bearing capacity change from material strength control to overall stability control; 2) among the parameters of each component of PEC wall, the flange thickness and the section thickness of the main steel parts had significant effects on the stability performance, and the material strength, web thickness of the main steel parts, and the cross-sectional height of the components had relatively little effect on the stability performance; 3) the relevant specifications for PEC wall design have not been promulgated at home and abroad, and the four types of section stability curves provided by China′s current design code Steel Structure Design Standard(GB 50017—2017) are not applicable to the determination of the axial compressive stability coefficient of PEC wall; 4) the calculation formula of the axial compressive stability coefficient of PEC wall proposed in this paper is "three-stage". The calculated value of the formula is in good agreement with the finite element results, and can maintain high accuracy for PEC walls of different materials and sizes, which can be used to determine the axial compressive stability coefficient of PEC walls.
2023, 38(6): 22-31.
doi: 10.13206/j.gjgS22090103
Abstract:
Partially encased composite steel and concrete structure is referred to as the PEC structure, with the advantages of concrete structure and steel structure. The filling concrete can effectively improve the anti-flexural capacity of the steel, and the flange is formed by welding steel bars. The connecting rod enhances the constraints of the steel flange and concrete, thereby increasing the bearing capacity and stiffness of the structure. At present, there are many studies on platform PEC beams at home and abroad, but there are few researches on corrugated web PEC beams. In order to study the bending performance of the corrugated web PEC beams, the flat belt of the H-type steel is replaced with a sinusoidal corrugated web on the basis of the PEC beams, and the sinusoidal corrugated web PEC beam is proposed to study the bending performance, in order to provide reference for the practical application of this structure. Four sinusoidal corrugated web PEC beam specimens were designed, and the structural measures of reinforcement and weld form were changed respectively, and data such as deflection, slip and strain was collected by four-point bending loading test. Through load-middle span deflection curve analysis, bearing capacity analysis, deformation analysis, strain analysis, steel-concrete slip analysis, etc., the flexural strength, ductility, bond slip and other properties of four sinusoidal corrugated web PEC beam specimens were investigated. The advantages and disadvantages of different structures were compared.The test results show that the measured bearing capacity of the specimen is greater than theoretical bearing capacity, the yield bearing capacity and ultimate bearing capacity of the four structures have little difference, and the bearing capacity can be calculated by edge yield criteria and full cross-sectional plasticity criteria. There is no significant difference in bearing capacity and deformation between specimen with single fillet weld and double fillet weld between corrugated web and upper and lower flange, therefore the corrugated web of PEC beam and flange plate can be welded by single fillet weld. But the quality of the weld must be strictly ensured when making it. The strain of the main steel component along the web height of the beam was very small and did not reach the yield strain. The strain began to increase near the flange, and the strain at the flange increased sharply, indicating that the bending normal stress was almost completely borne by the flange, and the web strain of the main steel parts did not conform to the assumption of plane section. There is little difference in the slip amount of PEC beams of four kinds of structures. The slip at the support is small, and the maximum slip amount is basically within 1 mm. Due to serious concrete cracking in the mid-span belly, the slip quantity includes the influence of crack width, leading to much larger measured results. The data are for reference only. In the test, none of the sinusoidal corrugated web PEC beams of the four structural forms reached section failure in the end. The test was stopped due to excessive deflection, and the load-middle span deflection curve did not decline. The subsequent improvement will be considered, and the end of the test will be controlled according to the final failure of the specimen, so as to further explore the performance of the specimen.
Partially encased composite steel and concrete structure is referred to as the PEC structure, with the advantages of concrete structure and steel structure. The filling concrete can effectively improve the anti-flexural capacity of the steel, and the flange is formed by welding steel bars. The connecting rod enhances the constraints of the steel flange and concrete, thereby increasing the bearing capacity and stiffness of the structure. At present, there are many studies on platform PEC beams at home and abroad, but there are few researches on corrugated web PEC beams. In order to study the bending performance of the corrugated web PEC beams, the flat belt of the H-type steel is replaced with a sinusoidal corrugated web on the basis of the PEC beams, and the sinusoidal corrugated web PEC beam is proposed to study the bending performance, in order to provide reference for the practical application of this structure. Four sinusoidal corrugated web PEC beam specimens were designed, and the structural measures of reinforcement and weld form were changed respectively, and data such as deflection, slip and strain was collected by four-point bending loading test. Through load-middle span deflection curve analysis, bearing capacity analysis, deformation analysis, strain analysis, steel-concrete slip analysis, etc., the flexural strength, ductility, bond slip and other properties of four sinusoidal corrugated web PEC beam specimens were investigated. The advantages and disadvantages of different structures were compared.The test results show that the measured bearing capacity of the specimen is greater than theoretical bearing capacity, the yield bearing capacity and ultimate bearing capacity of the four structures have little difference, and the bearing capacity can be calculated by edge yield criteria and full cross-sectional plasticity criteria. There is no significant difference in bearing capacity and deformation between specimen with single fillet weld and double fillet weld between corrugated web and upper and lower flange, therefore the corrugated web of PEC beam and flange plate can be welded by single fillet weld. But the quality of the weld must be strictly ensured when making it. The strain of the main steel component along the web height of the beam was very small and did not reach the yield strain. The strain began to increase near the flange, and the strain at the flange increased sharply, indicating that the bending normal stress was almost completely borne by the flange, and the web strain of the main steel parts did not conform to the assumption of plane section. There is little difference in the slip amount of PEC beams of four kinds of structures. The slip at the support is small, and the maximum slip amount is basically within 1 mm. Due to serious concrete cracking in the mid-span belly, the slip quantity includes the influence of crack width, leading to much larger measured results. The data are for reference only. In the test, none of the sinusoidal corrugated web PEC beams of the four structural forms reached section failure in the end. The test was stopped due to excessive deflection, and the load-middle span deflection curve did not decline. The subsequent improvement will be considered, and the end of the test will be controlled according to the final failure of the specimen, so as to further explore the performance of the specimen.
2023, 38(6): 32-41.
doi: 10.13206/j.gjgS22092702
Abstract:
A PEC(Partially Encased Composite) member is the composite component with concrete filling between the flanges of I-beam or H-shaped steel, and reinforcement or flange connecting bars in the concrete. The structure using PEC members is called PEC structure, whose load bearing capacity, ductility and stiffness are better than pure steel and reinforced concrete structures, and has good fire resistance. A special technical specification CECS 719-2020 has already been developed for PEC structures by our national researchers, but the experimental research on the mechanical performance of rigid connection between PEC columns and beams in the weak axis direction is still insufficient. So in this paper, three sub-structural joint specimens between PEC columns and beams in the weak axis direction were designed, which were numbered JM, JH, BH. The monotonic static loading and hysteresis loading tests were carried out to investigate the mechanical performance and the failure modes. The joints were connected by the endplate and bolt. To meet the requirements of prefabrication and assembly in engineering projects, the divided plate and flat steel were used in the specimen design. Based on the technical specifications in Europe, Canada and China, many factors such as loading mode, failure mode, loading path, steel strength and concrete strength were taken into account for the design of the test apparatus, loading regime and testing scheme. And then, by using antisymmetric loading at the beam ends, one monotonic static loading test and two hysteresis loading tests were carried out. Among the 3 specimens, the column flange and plane zone of JM and JH specimens were weakened, JM specimen was loaded by static monotonic loading and JH specimen was loaded by hysteresis loading; both of them showed column failure mode, and the ultimate loading capacity of JH specimen was lower than that of JM specimen; the beam flange and web of BH specimen were weakened and loaded by hysteresis loading, and finally the beam failure mode appeared. The results show that: 1)The tested joint between PEC beam and column in its weak axis direction can meet the requirements of rigid joints. 2) By using the calculation method of bearing capacity of beam, column and weak axis connection joints specified in CECS specification, the failure mode of specimens can be predicted correctly, which guiding significance for the projects. 3) Due to the lateral restraint from the concrete in the beam member, the concrete portion of the PEC weak-axis joint can effectively increase the shear loading capacity of the joint. 4) The accumulation of damage to the concrete under hysteresis loading will cause a reduction in the ultimate loading capacity of the PEC specimens.
A PEC(Partially Encased Composite) member is the composite component with concrete filling between the flanges of I-beam or H-shaped steel, and reinforcement or flange connecting bars in the concrete. The structure using PEC members is called PEC structure, whose load bearing capacity, ductility and stiffness are better than pure steel and reinforced concrete structures, and has good fire resistance. A special technical specification CECS 719-2020 has already been developed for PEC structures by our national researchers, but the experimental research on the mechanical performance of rigid connection between PEC columns and beams in the weak axis direction is still insufficient. So in this paper, three sub-structural joint specimens between PEC columns and beams in the weak axis direction were designed, which were numbered JM, JH, BH. The monotonic static loading and hysteresis loading tests were carried out to investigate the mechanical performance and the failure modes. The joints were connected by the endplate and bolt. To meet the requirements of prefabrication and assembly in engineering projects, the divided plate and flat steel were used in the specimen design. Based on the technical specifications in Europe, Canada and China, many factors such as loading mode, failure mode, loading path, steel strength and concrete strength were taken into account for the design of the test apparatus, loading regime and testing scheme. And then, by using antisymmetric loading at the beam ends, one monotonic static loading test and two hysteresis loading tests were carried out. Among the 3 specimens, the column flange and plane zone of JM and JH specimens were weakened, JM specimen was loaded by static monotonic loading and JH specimen was loaded by hysteresis loading; both of them showed column failure mode, and the ultimate loading capacity of JH specimen was lower than that of JM specimen; the beam flange and web of BH specimen were weakened and loaded by hysteresis loading, and finally the beam failure mode appeared. The results show that: 1)The tested joint between PEC beam and column in its weak axis direction can meet the requirements of rigid joints. 2) By using the calculation method of bearing capacity of beam, column and weak axis connection joints specified in CECS specification, the failure mode of specimens can be predicted correctly, which guiding significance for the projects. 3) Due to the lateral restraint from the concrete in the beam member, the concrete portion of the PEC weak-axis joint can effectively increase the shear loading capacity of the joint. 4) The accumulation of damage to the concrete under hysteresis loading will cause a reduction in the ultimate loading capacity of the PEC specimens.
2023, 38(6): 42-50.
doi: 10.13206/j.gjgS22090801
Abstract:
The rise of logistics industry has given birth to the concept of logistics architecture, which is characterized by large load, large span and high floor height. For such buildings, the existing steel-concrete composite beams and steel reinforced concrete beams are not only expensive, but also resource consuming, which runs counter to the new green construction mode advocated in our country. In practical engineering applications, the owner urgently needs to reduce the project cost. Therefore it is particularly important to develop new horizontal components for such buildings. In order to solve the above problems, a prefabricated partially encased concrete beam(PPECB) by combining partially encased concrete beam(PECB) with unsupported construction method is proposed in this paper. In order to study the shear behavior of prefabricated partially encased concrete beams, eight partially prefabricated beams and one PEC beam(monolithic casting comparison specimen) were designed to study the shear behavior. The main purpose is to observe and record the whole test process, and obtain the shear failure characteristics, crack development, strain development law, and mid-span deflection curve of prefabricated partially encased concrete beams under vertical load. The shear failure mechanism of precast partially encased concrete beams is clarified. The influence of pouring method, steel web thickness, concrete strength, stirrup diameter, stirrup spacing and shear span ratio on the shear performance of precast partially encased concrete beams is discussed. The shear bearing capacity model of precast partially encased concrete beams is established, and the calculation method of shear bearing capacity of precast partially encased concrete beams is deduced. The test results show that the prefabricated partially encased concrete beam can basically maintain the overall working performance, which is more consistent with the shear performance of the cast-in-place partially encased concrete composite beam(PECB), and its shear bearing capacity is slightly lower than the cast-in-place partially encased concrete composite beam. In general, it is considered that the different pouring methods of pouring and prefabrication have little influence on the bearing capacity of specimens. The shear failure mode of prefabricated partially encased concrete beams is shear failure. The largest crack develops slowly before yielding and rapidly after yielding. The concrete strength, stirrup spacing and diameter have great influence on the crack development rate. With the increase of concrete strength grade, the shear capacity of prefabricated partially encased concrete beams increases. The shear capacity of prefabricated partially encased concrete beams increases with the increase of steel web thickness. Increasing the diameter of stirrups and decreasing the spacing of stirrups can improve the shear capacity of prefabricated partially encased concrete beams. When the shear span ratio is between 1.5 and 2.5, the shear capacity of prefabricated partially encased concrete beams decreases with the increase of shear span ratio. With reference to the existing specifications, the formula for calculating the shear capacity of prefabricated partially encased concrete beams is preliminarily given. Based on this theory, the calculated results are in good agreement with the test values, which can provide reference for practical engineering applications.
The rise of logistics industry has given birth to the concept of logistics architecture, which is characterized by large load, large span and high floor height. For such buildings, the existing steel-concrete composite beams and steel reinforced concrete beams are not only expensive, but also resource consuming, which runs counter to the new green construction mode advocated in our country. In practical engineering applications, the owner urgently needs to reduce the project cost. Therefore it is particularly important to develop new horizontal components for such buildings. In order to solve the above problems, a prefabricated partially encased concrete beam(PPECB) by combining partially encased concrete beam(PECB) with unsupported construction method is proposed in this paper. In order to study the shear behavior of prefabricated partially encased concrete beams, eight partially prefabricated beams and one PEC beam(monolithic casting comparison specimen) were designed to study the shear behavior. The main purpose is to observe and record the whole test process, and obtain the shear failure characteristics, crack development, strain development law, and mid-span deflection curve of prefabricated partially encased concrete beams under vertical load. The shear failure mechanism of precast partially encased concrete beams is clarified. The influence of pouring method, steel web thickness, concrete strength, stirrup diameter, stirrup spacing and shear span ratio on the shear performance of precast partially encased concrete beams is discussed. The shear bearing capacity model of precast partially encased concrete beams is established, and the calculation method of shear bearing capacity of precast partially encased concrete beams is deduced. The test results show that the prefabricated partially encased concrete beam can basically maintain the overall working performance, which is more consistent with the shear performance of the cast-in-place partially encased concrete composite beam(PECB), and its shear bearing capacity is slightly lower than the cast-in-place partially encased concrete composite beam. In general, it is considered that the different pouring methods of pouring and prefabrication have little influence on the bearing capacity of specimens. The shear failure mode of prefabricated partially encased concrete beams is shear failure. The largest crack develops slowly before yielding and rapidly after yielding. The concrete strength, stirrup spacing and diameter have great influence on the crack development rate. With the increase of concrete strength grade, the shear capacity of prefabricated partially encased concrete beams increases. The shear capacity of prefabricated partially encased concrete beams increases with the increase of steel web thickness. Increasing the diameter of stirrups and decreasing the spacing of stirrups can improve the shear capacity of prefabricated partially encased concrete beams. When the shear span ratio is between 1.5 and 2.5, the shear capacity of prefabricated partially encased concrete beams decreases with the increase of shear span ratio. With reference to the existing specifications, the formula for calculating the shear capacity of prefabricated partially encased concrete beams is preliminarily given. Based on this theory, the calculated results are in good agreement with the test values, which can provide reference for practical engineering applications.
2023, 38(6): 51-60.
doi: 10.13206/j.gjgS23030201
Abstract:
As theoretical research and engineering applications continue to advance, partially encased steel-concrete composite beams(PEC beams) have been shown to exhibit not only superior fire resistance but also significantly enhanced load-bearing capacity, stiffness, and resistance to buckling when compared to traditional steel-concrete composite beams. In order to study the mechanical performance and stiffness calculation methods of PEC beams subjected to hogging bending moment, static bending tests on three PEC beams with different force ratios and one steel-concrete composite beam were conducted. In addition, the effect of reinforced concrete between the flanges of steel beam on the bending stiffness under negative bending moment was also analyzed. The experimental results suggest that the flexural capacity and stiffness of PEC beams subjected to hogging bending moment compared with steel-concrete composite beam are increased by 40% and 25%, respectively. The ultimate bearing capacity of PEC beams increases with the increase of the force ratio. The width of cracks observed in the flange concrete of PEC beams is significantly smaller than that of normal composite beam. Furthermore, it has been observed that the crack width in both the flange concrete and web concrete of PEC beams decreases as the cross-sectional area of the longitudinal reinforcement increases. When subjected to negative bending moments, the section stiffness of the composite beams experiences a reduction due to the occurrence of tensile cracking within the concrete. As these cracks continue to propagate, the contribution of the web concrete to the overall stiffness of the beam gradually diminishes. Nevertheless, given that the web concrete is confined by the steel beam and that cracks have not fully penetrated it, concrete between the flanges remains capable of contributing to the stiffness of PEC beams. When the load approached its maximum capacity, the load-deflection curves gradually flatten which indicates favorable ductility characteristics of PEC beams. During the initial stages of loading, composite beams conform to the plane section assumption. However, as the load increases, slippage between the concrete slab and steel beam increases, which causes the difference in strain at their connection interface gradually increases. Considering the influence of reinforced concrete between the flanges of steel beam on the stiffness of composite beam, as well as slip effect of the interface between steel beam and concrete slab, the formulas for calculating the bending stiffness of PEC beams are proposed based on experiments. The test results verify the accuracy of the proposed calculation methods.
As theoretical research and engineering applications continue to advance, partially encased steel-concrete composite beams(PEC beams) have been shown to exhibit not only superior fire resistance but also significantly enhanced load-bearing capacity, stiffness, and resistance to buckling when compared to traditional steel-concrete composite beams. In order to study the mechanical performance and stiffness calculation methods of PEC beams subjected to hogging bending moment, static bending tests on three PEC beams with different force ratios and one steel-concrete composite beam were conducted. In addition, the effect of reinforced concrete between the flanges of steel beam on the bending stiffness under negative bending moment was also analyzed. The experimental results suggest that the flexural capacity and stiffness of PEC beams subjected to hogging bending moment compared with steel-concrete composite beam are increased by 40% and 25%, respectively. The ultimate bearing capacity of PEC beams increases with the increase of the force ratio. The width of cracks observed in the flange concrete of PEC beams is significantly smaller than that of normal composite beam. Furthermore, it has been observed that the crack width in both the flange concrete and web concrete of PEC beams decreases as the cross-sectional area of the longitudinal reinforcement increases. When subjected to negative bending moments, the section stiffness of the composite beams experiences a reduction due to the occurrence of tensile cracking within the concrete. As these cracks continue to propagate, the contribution of the web concrete to the overall stiffness of the beam gradually diminishes. Nevertheless, given that the web concrete is confined by the steel beam and that cracks have not fully penetrated it, concrete between the flanges remains capable of contributing to the stiffness of PEC beams. When the load approached its maximum capacity, the load-deflection curves gradually flatten which indicates favorable ductility characteristics of PEC beams. During the initial stages of loading, composite beams conform to the plane section assumption. However, as the load increases, slippage between the concrete slab and steel beam increases, which causes the difference in strain at their connection interface gradually increases. Considering the influence of reinforced concrete between the flanges of steel beam on the stiffness of composite beam, as well as slip effect of the interface between steel beam and concrete slab, the formulas for calculating the bending stiffness of PEC beams are proposed based on experiments. The test results verify the accuracy of the proposed calculation methods.
2023, 38(6): 61-63.
doi: 10.13206/j.gjgS22123020
Abstract:
An important aspect of the theory of concrete filled circular pipes is to determine the limiting confining coefficient at which the axial force-strain curves become ideal elastic-plastic. This article proposed a simple way for computing this limiting confining coefficient, the results are in good agreement with the test results reported by the literature, implying the correctness of the proposed method.
An important aspect of the theory of concrete filled circular pipes is to determine the limiting confining coefficient at which the axial force-strain curves become ideal elastic-plastic. This article proposed a simple way for computing this limiting confining coefficient, the results are in good agreement with the test results reported by the literature, implying the correctness of the proposed method.
