Static load tests and bearing capacity analyses are carried out for two outer-plated steel-concrete continuous composite beams. The load-deflection curve and the load-strain curve of specimens are obtained and analyze...Static load tests and bearing capacity analyses are carried out for two outer-plated steel-concrete continuous composite beams. The load-deflection curve and the load-strain curve of specimens are obtained and analyzed. The test results indicate that effective cooperation can be achieved by the shearresistant connection between the reinforcement in the negative moment area and the outer-plated steel beam, and the overall working performance of the composite beams is favorable. At the load-bearing limiting state, the plastic strain on the maximum negative and positive moment section becomes fully developed so as to form relatively ideal plastic hinges. With the increase in the reinforcement ratio, the moment-carrying capacity of the composite beams improves significantly, but the ductility of the beams and the rotation ability of the plastic hinges decrease. The formulae for calculating the limit bending capacity in the negative moment area of outer-plated steel-concrete composite beams are proposed based on the test data. The calculated results agree well with the test results.展开更多
The determinations of flexural behavior of some engineering structures are based on different theories and equations, but it has been observed that some of these equations may not give true representation. This work h...The determinations of flexural behavior of some engineering structures are based on different theories and equations, but it has been observed that some of these equations may not give true representation. This work has looked into the difference that may occur between theoretical and experimental results. An experimental test carried out on models of waffle and solid slabs structures were described and results from twenty test samples are presented. Each specimen was subjected to an incremental axial loading of 1 kN interval after 28 days of casting. The flexural moments, deflections and crack width at failure were obtained. The experimental flexural crack and theoretical flexural cracks for both types of slabs were compared. The result for flexural moments for waffle was 5.526 kNm, while solid slab was 3.684 kNm. The deflections showed that waffle slabs has 3.64 mm while solid has 9.28 mm, hence waffle has a higher structural stiffness than solid slabs, but the flexural cracks did not give the same results especially for the estimated crack width. It was concluded that estimated results based on developed equations may not be accurate because it is based on ideal situation.展开更多
According to the concept of virtual bending force,a rational explanation for SHOHET's model was presented. Considering the deformation characters of the work rolls in four-high mill,the deformation model of the wo...According to the concept of virtual bending force,a rational explanation for SHOHET's model was presented. Considering the deformation characters of the work rolls in four-high mill,the deformation model of the work roll was regarded as a cantilever beam and new influence coefficients were deduced.The effect of the bending force was taken into account independently. Therefore,the contribution to work roll deflection caused by rolling load,rolling pressure between rolls and bending force can be got from the new formulas.To validate the accuracy of the formulas,the results obtained from the new formulas were compared with those from SHOHET's formulas.It is found that they highly coincide,which illustrates that the formulas are reliable.展开更多
The rubber circular plate is considered as a kind of membrane. Based on the character that there exists no bending moment inside a membrane, the geometric behavior of the rubber circular plate in expanding state was d...The rubber circular plate is considered as a kind of membrane. Based on the character that there exists no bending moment inside a membrane, the geometric behavior of the rubber circular plate in expanding state was described with the aid of a group of mathematic method. The relationship between deflection and load was attained by means of calculating stress and strain inside the curved surface of rubber plate. Meantime, based on Hencky method, the relationship between deflection and load was attained and considered as the Hencky solution. The different results given rise by the two different resolving methods were compared. The deviation results from the Hencky method was discussed, and a kind of correcting method was put forward.展开更多
Native heart valve leaflets with layered fibrous structures show anisotropic characteristics,allowing them to withstand complex mechanical loading for long-term cardiac cycles.Herein,two types of silk fibroin(SF)fiber...Native heart valve leaflets with layered fibrous structures show anisotropic characteristics,allowing them to withstand complex mechanical loading for long-term cardiac cycles.Herein,two types of silk fibroin(SF)fiber membranes with anisotropic(ASF)and isotropic(ISF)properties were prepared by electrospinning,and were further combined with poly(ethylene glycol)diacrylate(PEGDA)hydrogels to serve as polymeric heart valve(PHV)substitutes(PEGDA-ASF and PEGDA-ISF).The uniaxial tensile tests showed obvious anisotropy of PEGDA-ASF with elastic moduli of 10.95±1.09 and3.55±0.32 MPa,respectively,along the directions parallel and perpendicular to the fiber alignment,while PEGDA-ISF possessed isotropic property with elastic moduli of 4.54±0.43 MPa.The PHVs from both PEGDA-ASF and PEGDA-ISF presented appropriate hydrodynamic properties from pulse duplicator tests according to the ISO 5840-3 standard.However,finite element analysis(FEA)revealed the anisotropic PEGDA-ASF valve showed a lower maximum principle stress value(2.20 MPa)in commissures during diastole compared with that from the isotropic PEGDA-ISF valve(2.37 MPa).In the fully open state,the bending area of the PEGDA-ASF valve appeared in the belly portion and near the attachment line like native valves,however,which was close to free edges for the PEGDA-ISF valve.The Gauss curvature analysis also indicated that the anisotropic PEGDA-ASF valve can produce appropriate surface morphology by dynamically adjusting the movement of bending area during the opening process.Hence,anisotropy of PHVs with bio-inspired layered fibrous struc-tures played important roles in mechanical and hydrodynamic behavior mimicking native heart valves.展开更多
文摘Static load tests and bearing capacity analyses are carried out for two outer-plated steel-concrete continuous composite beams. The load-deflection curve and the load-strain curve of specimens are obtained and analyzed. The test results indicate that effective cooperation can be achieved by the shearresistant connection between the reinforcement in the negative moment area and the outer-plated steel beam, and the overall working performance of the composite beams is favorable. At the load-bearing limiting state, the plastic strain on the maximum negative and positive moment section becomes fully developed so as to form relatively ideal plastic hinges. With the increase in the reinforcement ratio, the moment-carrying capacity of the composite beams improves significantly, but the ductility of the beams and the rotation ability of the plastic hinges decrease. The formulae for calculating the limit bending capacity in the negative moment area of outer-plated steel-concrete composite beams are proposed based on the test data. The calculated results agree well with the test results.
文摘The determinations of flexural behavior of some engineering structures are based on different theories and equations, but it has been observed that some of these equations may not give true representation. This work has looked into the difference that may occur between theoretical and experimental results. An experimental test carried out on models of waffle and solid slabs structures were described and results from twenty test samples are presented. Each specimen was subjected to an incremental axial loading of 1 kN interval after 28 days of casting. The flexural moments, deflections and crack width at failure were obtained. The experimental flexural crack and theoretical flexural cracks for both types of slabs were compared. The result for flexural moments for waffle was 5.526 kNm, while solid slab was 3.684 kNm. The deflections showed that waffle slabs has 3.64 mm while solid has 9.28 mm, hence waffle has a higher structural stiffness than solid slabs, but the flexural cracks did not give the same results especially for the estimated crack width. It was concluded that estimated results based on developed equations may not be accurate because it is based on ideal situation.
基金Project(20050216007) supported by the Specialized Research Fund for the Doctoral Program of Higher Education of China
文摘According to the concept of virtual bending force,a rational explanation for SHOHET's model was presented. Considering the deformation characters of the work rolls in four-high mill,the deformation model of the work roll was regarded as a cantilever beam and new influence coefficients were deduced.The effect of the bending force was taken into account independently. Therefore,the contribution to work roll deflection caused by rolling load,rolling pressure between rolls and bending force can be got from the new formulas.To validate the accuracy of the formulas,the results obtained from the new formulas were compared with those from SHOHET's formulas.It is found that they highly coincide,which illustrates that the formulas are reliable.
文摘The rubber circular plate is considered as a kind of membrane. Based on the character that there exists no bending moment inside a membrane, the geometric behavior of the rubber circular plate in expanding state was described with the aid of a group of mathematic method. The relationship between deflection and load was attained by means of calculating stress and strain inside the curved surface of rubber plate. Meantime, based on Hencky method, the relationship between deflection and load was attained and considered as the Hencky solution. The different results given rise by the two different resolving methods were compared. The deviation results from the Hencky method was discussed, and a kind of correcting method was put forward.
基金supported by the National Natural Science Foundation of China (31300788)the Hundred-Talent Program from Chinese Academy of Sciences
文摘Native heart valve leaflets with layered fibrous structures show anisotropic characteristics,allowing them to withstand complex mechanical loading for long-term cardiac cycles.Herein,two types of silk fibroin(SF)fiber membranes with anisotropic(ASF)and isotropic(ISF)properties were prepared by electrospinning,and were further combined with poly(ethylene glycol)diacrylate(PEGDA)hydrogels to serve as polymeric heart valve(PHV)substitutes(PEGDA-ASF and PEGDA-ISF).The uniaxial tensile tests showed obvious anisotropy of PEGDA-ASF with elastic moduli of 10.95±1.09 and3.55±0.32 MPa,respectively,along the directions parallel and perpendicular to the fiber alignment,while PEGDA-ISF possessed isotropic property with elastic moduli of 4.54±0.43 MPa.The PHVs from both PEGDA-ASF and PEGDA-ISF presented appropriate hydrodynamic properties from pulse duplicator tests according to the ISO 5840-3 standard.However,finite element analysis(FEA)revealed the anisotropic PEGDA-ASF valve showed a lower maximum principle stress value(2.20 MPa)in commissures during diastole compared with that from the isotropic PEGDA-ISF valve(2.37 MPa).In the fully open state,the bending area of the PEGDA-ASF valve appeared in the belly portion and near the attachment line like native valves,however,which was close to free edges for the PEGDA-ISF valve.The Gauss curvature analysis also indicated that the anisotropic PEGDA-ASF valve can produce appropriate surface morphology by dynamically adjusting the movement of bending area during the opening process.Hence,anisotropy of PHVs with bio-inspired layered fibrous struc-tures played important roles in mechanical and hydrodynamic behavior mimicking native heart valves.
