Some remarks on load modeling in nonlinear structural analysis–Statics with large deformations–Consistent treatment of follower load effects and load control

Load modeling in nonlinear statics, particularly incorporating large deformations differs significantly from the treatment in linear analysis. As in structural dynamics masses in a gravity field generate the loading, their location, and their modifications within the deformation process must be considered in a nonlinear simulation. A specific view besides loading by masses is on gas and fluid interaction with structures. In addition, load control using specifically designed algorithms is evaluated with respect to realistic applications. Within the load modeling an unavoidable, however side aspect, is the general discussion about the so-called follower forces and non-conservative loading. As an example of real-world applications, the specifics of inflated rubber dams are presented

Finite element analysis on multi-chamber tensairity-like structures filled with fluid and/or gas

The concept of Tensairity-structures [6] developed by the company Airlight in Biasca, Switzerland, has been known since 2004. The advantages of the airbeams with a compression element and a spiraled cable are essentially their light weight and that such beams can be used for wide span structures. To achieve a further weight reduction Pronk et al [8] proposed to replace the compression element by an additional slim chamber filled with water. Experiments with these multi-chamber beams with and without cables showed a stiffer behavior in bending tests compared to only air filled beams. In the current contribution different tests like - primarily - the bending of multi-chamber beams will be simulated with finite elements. Explicit and implicit finite element simulations with LS-DYNA [7] and FEAP-MeKa [11] respectively will be performed with a special focus on the interaction of structural deformations and the gas/fluid filling in combination with the cables contacting the membranes. The specific features have been implemented in the above codes. The fluid and/or gas filling is replaced by an energetically equivalent load and corresponding stiffness matrix contributions to simulate quasi-static fluid-structure interaction taking the effect of the deformations of the chambers on the fluid/gas filling into account. This approach has already been introduced for fluid-structure interaction problems with large deformations and stability analysis in [1], [2]. For the implicit simulation the cables will be added using special solid-beam finite elements [5]. A new curve-to-surface contact algorithm is developed to model the contact interaction between cables and the deformable shell structure

On contact between curves and rigid surfaces – from verification of the euler-eytelwein problem to knots

A general theory for the Curve-To-Curve contact is applied to develop a special contact algorithm between curves and rigid surfaces. In this case contact kinematics are formulated in the local coordinate system attached to the curve, however, contact is defined at integration points of the curve line (Mortar type contact). The corresponding Closest Point Projection (CPP) procedure is used to define then a shortest distance between the integration point on a curve and the rigid surface. For some simple approximations of the rigid surface closed form solutions are possible. Within the finite element implementation the isogeometric approach is used to model curvilinear cables and the rigid surfaces can be defined in general via NURB surface splines. Verification of the finite element algorithm is given using the well-known analytical solution of the Euler-Eytelwein problem – a rope on a cylindrical surface. The original 2D formula is generalized into the 3D case considering an additional parameter H-pitch for the helix. Finally, applications to knot mechanics are shown