In order to validate the accuracy of nonlinear fire simulation programs,comparison analysis is carried out between simulation and experiment induced from small-scale specimens,and then fire resistance of large-scale p...In order to validate the accuracy of nonlinear fire simulation programs,comparison analysis is carried out between simulation and experiment induced from small-scale specimens,and then fire resistance of large-scale prestressed concrete slabs is further investigated through parameter expansion.The influences on fire resistance ratings controlled by deflection are explored and discussed,including effective span,concrete cover thickness,load level,prestress degree,effective prestress,composite reinforcement index and other factors.The calculated results indicate that fire resistance ratings of large-scale bonded prestressed concrete simply supported slabs are bigger than those of small-scale ones.Finally,the calculation formulas of fire resistance ratings controlled by deflection are established,which rationally consider the influence of effective span,concrete cover thickness,load level,composite reinforcement index and so on key factors.展开更多
A new analytical study on stresses around a post-tensioned anchor in rocks with two perpendicular joint sets is presented. The assumptions of orthotropic elastic rock with plane strain conditions are made in derivatio...A new analytical study on stresses around a post-tensioned anchor in rocks with two perpendicular joint sets is presented. The assumptions of orthotropic elastic rock with plane strain conditions are made in derivation of the formulations. A tri-linear bond-slip constitutive law is used for modeling the tendon-grout interface behavior and debonding of this interface. The bearing plate width is also considered in the analysis. The obtained solutions are in the integral forms and numerical techniques that have been used for evaluation. In the illustrative example given, the major principal stress is compressive in the anchor free zone and compressive stress concentrations of 815 k Pa and 727 k Pa(for the anchor load of 300 k N) are observed under the bearing plate and the bond length proximal end, respectively. However, large values of tensile stresses with the maximum of-434 k Pa are formed at the bond length distal end. The results obtained using the proposed solution are compared very those of numerical method(FEM).展开更多
An experimental study is performed on five post-tensioned concrete beams to explore the effects of different fracture positions on secondary transfer length and residual prestress of fractured strand.A numerical model...An experimental study is performed on five post-tensioned concrete beams to explore the effects of different fracture positions on secondary transfer length and residual prestress of fractured strand.A numerical model is developed and used to predict the secondary transfer length and residual prestress of fractured strand in post-tensioned concrete beams.The model change interaction,which can deactivate and reactivate the elements for simulating the removal and reproduction of parts of the model,is used to reproduce the secondary anchorage of fractured strand.The numerical model is verified by experimental results.Results shows that the fractured strand can be reanchored in concrete through the secondary anchorage,and the secondary transfer length of fractured strand with the diameter of 15.2 mm is 1133 mm.The residual prestress of fractured strand increases gradually in the secondary transfer length,and tends to be a constant beyond it.When the fractured strand is fully anchored in concrete,a minor prestress loss will appear,and the average prestress loss is 2.28%in the present study.展开更多
基金Sponsored by the National Natural Science Foundation of China(Grant No.50678050)
文摘In order to validate the accuracy of nonlinear fire simulation programs,comparison analysis is carried out between simulation and experiment induced from small-scale specimens,and then fire resistance of large-scale prestressed concrete slabs is further investigated through parameter expansion.The influences on fire resistance ratings controlled by deflection are explored and discussed,including effective span,concrete cover thickness,load level,prestress degree,effective prestress,composite reinforcement index and other factors.The calculated results indicate that fire resistance ratings of large-scale bonded prestressed concrete simply supported slabs are bigger than those of small-scale ones.Finally,the calculation formulas of fire resistance ratings controlled by deflection are established,which rationally consider the influence of effective span,concrete cover thickness,load level,composite reinforcement index and so on key factors.
文摘A new analytical study on stresses around a post-tensioned anchor in rocks with two perpendicular joint sets is presented. The assumptions of orthotropic elastic rock with plane strain conditions are made in derivation of the formulations. A tri-linear bond-slip constitutive law is used for modeling the tendon-grout interface behavior and debonding of this interface. The bearing plate width is also considered in the analysis. The obtained solutions are in the integral forms and numerical techniques that have been used for evaluation. In the illustrative example given, the major principal stress is compressive in the anchor free zone and compressive stress concentrations of 815 k Pa and 727 k Pa(for the anchor load of 300 k N) are observed under the bearing plate and the bond length proximal end, respectively. However, large values of tensile stresses with the maximum of-434 k Pa are formed at the bond length distal end. The results obtained using the proposed solution are compared very those of numerical method(FEM).
基金the National Natural Science Foundation of China(Grant No.52008035)the Science Fund for Creative Research Groups of Hunan Province(No.2020JJ1006)+3 种基金the Science and Technology Innovation Program of Hunan Province(No.2020RC4024)the Special Funds for the Construction of Innovative Provinces in Hunan Province(No.2019SK2171)the Natural Science Foundation of Hunan Province(No.2021JJ40574)National-Local Joint Laboratory of Engineering Technology for Long-term Performance enhancement of Bridges in Southern District(Changsha University of Science&Technology)(No.19KB03).
文摘An experimental study is performed on five post-tensioned concrete beams to explore the effects of different fracture positions on secondary transfer length and residual prestress of fractured strand.A numerical model is developed and used to predict the secondary transfer length and residual prestress of fractured strand in post-tensioned concrete beams.The model change interaction,which can deactivate and reactivate the elements for simulating the removal and reproduction of parts of the model,is used to reproduce the secondary anchorage of fractured strand.The numerical model is verified by experimental results.Results shows that the fractured strand can be reanchored in concrete through the secondary anchorage,and the secondary transfer length of fractured strand with the diameter of 15.2 mm is 1133 mm.The residual prestress of fractured strand increases gradually in the secondary transfer length,and tends to be a constant beyond it.When the fractured strand is fully anchored in concrete,a minor prestress loss will appear,and the average prestress loss is 2.28%in the present study.
