The Elements Manual states that the wave amplitude, ETA, is calculated at the integration points. The Theory Manual states that there are no integration points for the stiffness and mass matrices, but there are two integration points for the hydrodynamic loads. Are there integration points for the PIPE59 element, and, if so, where are they located?


For most elements, integration points are used to perform the numerical integration necessary to form the various matrices. For some elements, like most beam and pipe elements, we know the closed form of the integration and the matrices are calculated directly from that. PIPE59 falls into this catagory and the stiffness and mass matrices are created directly in a manner similar to BEAM4. Some line elements, like BEAM189, require numerical integration to create the stiffness and mass matrices and BEAM189 has 3 integration points along its length.

We need the integration points for PIPE59 to calculate the hydrodynamic loads from the WATER Table since the form of the hydrodynamic loads is unknown a priori. Chapter 13 describes the integration points for the various elements. For line elements such as the PIPE59 element, the possibility exists for 1, 2 or 3 integration points. PIPE59 has 2 integration points as it relates to the hydrodynamic effects and these are located at X = +/- 0.57735.... This is measured in the elements natural coordinate system that varies from X = -1 to X = +1. So, if the element were 10 long, the integration points would be located at (1-.57735)*5 = 2.11325 and 1.57735*5 = 7.88675.





Show Form
No comments yet. Be the first to add a comment!