The Local Joint Flexibility(_(LJF))of steel K-joints reinforced with external plates under axial loads is investigated in this paper.For this aim,firstly,a finite element(FE)model was produced and verified with the re...The Local Joint Flexibility(_(LJF))of steel K-joints reinforced with external plates under axial loads is investigated in this paper.For this aim,firstly,a finite element(FE)model was produced and verified with the results of several experimental tests.In the next step,a set of 150 FE models was generated to assess the effect of the brace angle(θ),the stiffener plate size(ηandλ),and the joint geometry(γ,τ,ξ,andβ)on the_(LJF)factor(f_(LJF)).The results showed that using the external plates can decrease 81%of the f_(LJF).Moreover,the reinforcing effect of the reinforcing plate on the f_(LJF)is more remarkable in the joints with smallerβ.Also,the effect of theγon the f_(LJF)ratio can be ignored.Despite the important effect of the f_(LJF)on the behavior of tubular joints,there is not available any study or equation on the f_(LJF)in any reinforced K-joints under axial load.Consequently,using the present FE results,a design parametric equation is proposed.The equation can reasonably predict the f_(LJF)in the reinforced K-joints under axial load.展开更多
It has been found that the fatigue life of tubular joints is not only determined by the hot spot stress,but also by the stress distribution through the tube thickness represented as the degree of bending(DoB).Conseque...It has been found that the fatigue life of tubular joints is not only determined by the hot spot stress,but also by the stress distribution through the tube thickness represented as the degree of bending(DoB).Consequently,the DoB value should be determined to improve the accuracy of fatigue assessment for both stress-life curve and fracture mechanics methods.Currently,no DoB parametric formula is available for concrete-filled rectangular hollow section(CFRHS)K-joints,despite their wide use in bridge engineering.Therefore,a robust finite element(FE)analysis was carried out to calculate the DoB of CFRHS K-joints under balanced-axial loading.The FE model was developed and verified against a test result to ensure accuracy.A comprehensive parametric study including 190 models,was conducted to establish the relationships between the DoBs and four specific variables.Based on the numerical results,design equations to predict DoBs for CFRHS K-joints were proposed through multiple regression analysis.A reduction of 37.17%was discovered in the DoB,resulting in a decrease of 66.85%in the fatigue life.Inclusively,the CFRHS K-joints with same hot spot stresses,may have completely different fatigue lives due to the different DoBs.展开更多
对承受疲劳载荷的海洋平台K型管节点首先进行了静力测试,确定了沿着焊缝的热应力区的应力分布及热应力区最大应力点的位置,从而判断裂纹产生的位置;然后通过专用测试设备提供循环疲劳载荷,用ACPD(Alternating Current Potential Drop,...对承受疲劳载荷的海洋平台K型管节点首先进行了静力测试,确定了沿着焊缝的热应力区的应力分布及热应力区最大应力点的位置,从而判断裂纹产生的位置;然后通过专用测试设备提供循环疲劳载荷,用ACPD(Alternating Current Potential Drop,即交流电流势能落差法)技术检测裂纹的产生和增长过程,得到裂纹最深点,用S-N曲线估算其疲劳寿命。对已有裂纹的K型管节点,用应力强度因子估计其剩余寿命。同时用测试的结果验证了S-N的准确性和可靠性。展开更多
文摘The Local Joint Flexibility(_(LJF))of steel K-joints reinforced with external plates under axial loads is investigated in this paper.For this aim,firstly,a finite element(FE)model was produced and verified with the results of several experimental tests.In the next step,a set of 150 FE models was generated to assess the effect of the brace angle(θ),the stiffener plate size(ηandλ),and the joint geometry(γ,τ,ξ,andβ)on the_(LJF)factor(f_(LJF)).The results showed that using the external plates can decrease 81%of the f_(LJF).Moreover,the reinforcing effect of the reinforcing plate on the f_(LJF)is more remarkable in the joints with smallerβ.Also,the effect of theγon the f_(LJF)ratio can be ignored.Despite the important effect of the f_(LJF)on the behavior of tubular joints,there is not available any study or equation on the f_(LJF)in any reinforced K-joints under axial load.Consequently,using the present FE results,a design parametric equation is proposed.The equation can reasonably predict the f_(LJF)in the reinforced K-joints under axial load.
基金sponsored by the Fundamental Research Funds for the Central Universities,CHD(No.300102211303)the Scientific Innovation Practice Project of Postgraduates of Chang’an University(No.300103714019).
文摘It has been found that the fatigue life of tubular joints is not only determined by the hot spot stress,but also by the stress distribution through the tube thickness represented as the degree of bending(DoB).Consequently,the DoB value should be determined to improve the accuracy of fatigue assessment for both stress-life curve and fracture mechanics methods.Currently,no DoB parametric formula is available for concrete-filled rectangular hollow section(CFRHS)K-joints,despite their wide use in bridge engineering.Therefore,a robust finite element(FE)analysis was carried out to calculate the DoB of CFRHS K-joints under balanced-axial loading.The FE model was developed and verified against a test result to ensure accuracy.A comprehensive parametric study including 190 models,was conducted to establish the relationships between the DoBs and four specific variables.Based on the numerical results,design equations to predict DoBs for CFRHS K-joints were proposed through multiple regression analysis.A reduction of 37.17%was discovered in the DoB,resulting in a decrease of 66.85%in the fatigue life.Inclusively,the CFRHS K-joints with same hot spot stresses,may have completely different fatigue lives due to the different DoBs.
文摘对承受疲劳载荷的海洋平台K型管节点首先进行了静力测试,确定了沿着焊缝的热应力区的应力分布及热应力区最大应力点的位置,从而判断裂纹产生的位置;然后通过专用测试设备提供循环疲劳载荷,用ACPD(Alternating Current Potential Drop,即交流电流势能落差法)技术检测裂纹的产生和增长过程,得到裂纹最深点,用S-N曲线估算其疲劳寿命。对已有裂纹的K型管节点,用应力强度因子估计其剩余寿命。同时用测试的结果验证了S-N的准确性和可靠性。
