The 8-node iso-parametric thin shell element was employed in the study of stress concentrations in the welded tubular “K” joint. Element equilibrium equations were derived using isoparametric formulation based on th...The 8-node iso-parametric thin shell element was employed in the study of stress concentrations in the welded tubular “K” joint. Element equilibrium equations were derived using isoparametric formulation based on thin shell theory. After assembly, the resulting system equations were solved using existing fortran programs. Numerical experiments were conducted to isolate and locate ideal gap (positions) for the two braces of the “K” joint. The nominal stresses were calculated from which stress concentration factors were obtained. The resulting stress concentration factors were presented both as tables and as figures. A good agreement between our solutions and those for model joints in the literature is good and acceptable. It was found that the wider apart the brace spacing is, the weaker the strength of the joint. It was also found that the best location for the braces occurs when the stress level changes sign either from positive to negative or vice versa at a critical sampling point.展开更多
Instability of a damaged pile due to a statically or dynamically applied overload is studied in this work using the finite element method. A damage parameter from such a pile is calculated using fracture mechanics con...Instability of a damaged pile due to a statically or dynamically applied overload is studied in this work using the finite element method. A damage parameter from such a pile is calculated using fracture mechanics concepts. The parameter is used to modify the beam element at the cracked or damaged location. Soil samples were obtained from the site of the pile and were subjected to laboratory tri-axial tests to obtain shear strength parameters c and . Other soil parameters such as Young’s modulus E and Poisson’s ratio were also obtained from the tri-axial tests. These were used to calculate shear strength and sub-grade modulus k for the soil. The parameters , E, and k were later used together with the damage parameter in the finite element simulation of the strength of the damaged pile using Eigen value analyses. The layered soil modulus is approximated by taking the mean value and is denoted by . The discrete element matrices are assembled into a system Eigen-value equation, the solution of which provides the stability or instability loads for the damaged pile. The results obtained for a pile without damage, that is, when =0 , are in good agreement with those published in the literature. It has also been found that higher soil resistance is needed to support the damaged pile. It is concluded that the proposed model is a good candidate for use in the analysis and repair of damaged piles due to earthquake overload by soil stabilization methods.展开更多
文摘The 8-node iso-parametric thin shell element was employed in the study of stress concentrations in the welded tubular “K” joint. Element equilibrium equations were derived using isoparametric formulation based on thin shell theory. After assembly, the resulting system equations were solved using existing fortran programs. Numerical experiments were conducted to isolate and locate ideal gap (positions) for the two braces of the “K” joint. The nominal stresses were calculated from which stress concentration factors were obtained. The resulting stress concentration factors were presented both as tables and as figures. A good agreement between our solutions and those for model joints in the literature is good and acceptable. It was found that the wider apart the brace spacing is, the weaker the strength of the joint. It was also found that the best location for the braces occurs when the stress level changes sign either from positive to negative or vice versa at a critical sampling point.
文摘Instability of a damaged pile due to a statically or dynamically applied overload is studied in this work using the finite element method. A damage parameter from such a pile is calculated using fracture mechanics concepts. The parameter is used to modify the beam element at the cracked or damaged location. Soil samples were obtained from the site of the pile and were subjected to laboratory tri-axial tests to obtain shear strength parameters c and . Other soil parameters such as Young’s modulus E and Poisson’s ratio were also obtained from the tri-axial tests. These were used to calculate shear strength and sub-grade modulus k for the soil. The parameters , E, and k were later used together with the damage parameter in the finite element simulation of the strength of the damaged pile using Eigen value analyses. The layered soil modulus is approximated by taking the mean value and is denoted by . The discrete element matrices are assembled into a system Eigen-value equation, the solution of which provides the stability or instability loads for the damaged pile. The results obtained for a pile without damage, that is, when =0 , are in good agreement with those published in the literature. It has also been found that higher soil resistance is needed to support the damaged pile. It is concluded that the proposed model is a good candidate for use in the analysis and repair of damaged piles due to earthquake overload by soil stabilization methods.
