Corrosion is a primary cause of the slippage of friction⁃type high⁃strength bolted(FHSB)T⁃stub connections.This paper attempts to quantify the residual capacity of FHSB T⁃stub connections with corroded nuts.Firstly,co...Corrosion is a primary cause of the slippage of friction⁃type high⁃strength bolted(FHSB)T⁃stub connections.This paper attempts to quantify the residual capacity of FHSB T⁃stub connections with corroded nuts.Firstly,corrosion simulation tests were conducted on 48 manually cut nuts to find out the relationship between the damage degree of nut section and the residual clamping force(RCF)of bolt.Then,static load tests were carried out on 24 FHSB T⁃stub connections with nuts of different degrees of damage to obtain the failure modes.By finite⁃element(FE)models,a comparative analysis was performed on the initial friction load(IFL)and ultimate strength(US)of each connection with corroded nuts.Finally,the parameters of 96 FE models for FHSB T⁃stub connections were analyzed and used to derive the calculation formulas for the degree of damage for each nut and the IFL and US of each connection.The results show that the RCF decay of a bolt is a quadratic function of the equivalent radius loss ratio and the shear failure after nut corrosion;the IFL of each connection had a clear linear correlation with the RCF of the corresponding bolts,and the correlation depends on the applied load and static friction on connecting plate interface induced by the clamping force;the static friction had little impact on the US of the connection;the proposed IFL and US formulas can effectively derive the residual anti⁃slip capacity of FHSB T⁃stub connections from the degree of damage of the corroded nut section.The research results provide a scientific basis for the replacement and maintenance of corroded bolts of FHSB T⁃stub connections.展开更多
With the recent development of material science,high strength steel(HSS)has become a practical solution for landmark buildings and major projects.The current codes for design of bearing-type bolted connections of stee...With the recent development of material science,high strength steel(HSS)has become a practical solution for landmark buildings and major projects.The current codes for design of bearing-type bolted connections of steel constructions were established based on the research of conventional steels.Since the mechanical properties of HSS are different from those of conventional steels,more works should be done to develop the appropriate approach for the design of bearing-type bolted connections in HSS.A review of the research carried out on bearing-type bolted connections fabricated from conventional steel and HSS is presented.The up-to-date tests conducted at Tongji University on four connection types fabricated from three grades of HSS with nominal yield strengths of 550,690,and 890 MPa are presented.The previous research on failure modes,bearing resistance and the design with consideration of bolt hole elongation are summarized.It is found that the behavior of bolted connections in HSS have no drastic difference compared to that of conventional steel connections.Although the ductility is reduced,plastic deformation capacity of HSS is sufficient to ensure the load redistribution between different bolts with normal construction tolerances.It is also found that behavior of each bolt of multi-bolt connections arranged in perpendicular to load direction is almost identical to that of a single-bolt connection with the same end distance.For connections with bolts arranged in parallel to load direction,the deformation capacity of the whole connection depends on the minimum value between the end distance and the spacing distances in load direction.The comparison with existing design codes shows that Eurocode3 and Chinese GB50017-2017 are conservative for the design of bolted connections in HSS while AISC 360-16 may overestimate the bearing resistance of bolted connections.展开更多
文摘Corrosion is a primary cause of the slippage of friction⁃type high⁃strength bolted(FHSB)T⁃stub connections.This paper attempts to quantify the residual capacity of FHSB T⁃stub connections with corroded nuts.Firstly,corrosion simulation tests were conducted on 48 manually cut nuts to find out the relationship between the damage degree of nut section and the residual clamping force(RCF)of bolt.Then,static load tests were carried out on 24 FHSB T⁃stub connections with nuts of different degrees of damage to obtain the failure modes.By finite⁃element(FE)models,a comparative analysis was performed on the initial friction load(IFL)and ultimate strength(US)of each connection with corroded nuts.Finally,the parameters of 96 FE models for FHSB T⁃stub connections were analyzed and used to derive the calculation formulas for the degree of damage for each nut and the IFL and US of each connection.The results show that the RCF decay of a bolt is a quadratic function of the equivalent radius loss ratio and the shear failure after nut corrosion;the IFL of each connection had a clear linear correlation with the RCF of the corresponding bolts,and the correlation depends on the applied load and static friction on connecting plate interface induced by the clamping force;the static friction had little impact on the US of the connection;the proposed IFL and US formulas can effectively derive the residual anti⁃slip capacity of FHSB T⁃stub connections from the degree of damage of the corroded nut section.The research results provide a scientific basis for the replacement and maintenance of corroded bolts of FHSB T⁃stub connections.
基金support by the National Natural Science Foundation of China(Grant No.51408428).
文摘With the recent development of material science,high strength steel(HSS)has become a practical solution for landmark buildings and major projects.The current codes for design of bearing-type bolted connections of steel constructions were established based on the research of conventional steels.Since the mechanical properties of HSS are different from those of conventional steels,more works should be done to develop the appropriate approach for the design of bearing-type bolted connections in HSS.A review of the research carried out on bearing-type bolted connections fabricated from conventional steel and HSS is presented.The up-to-date tests conducted at Tongji University on four connection types fabricated from three grades of HSS with nominal yield strengths of 550,690,and 890 MPa are presented.The previous research on failure modes,bearing resistance and the design with consideration of bolt hole elongation are summarized.It is found that the behavior of bolted connections in HSS have no drastic difference compared to that of conventional steel connections.Although the ductility is reduced,plastic deformation capacity of HSS is sufficient to ensure the load redistribution between different bolts with normal construction tolerances.It is also found that behavior of each bolt of multi-bolt connections arranged in perpendicular to load direction is almost identical to that of a single-bolt connection with the same end distance.For connections with bolts arranged in parallel to load direction,the deformation capacity of the whole connection depends on the minimum value between the end distance and the spacing distances in load direction.The comparison with existing design codes shows that Eurocode3 and Chinese GB50017-2017 are conservative for the design of bolted connections in HSS while AISC 360-16 may overestimate the bearing resistance of bolted connections.
