An important consideration in predicting the dynamic motion of highly deformable structures subject to blast loads is the effect of drag force. A representative example of this condition is a blast-loaded non-breathable fabric roof, typically used for tents or other aesthetic fabric structures. A fully coupled fluid-structure interaction (FSI) analysis to simulate the interaction of the fabric roof with the air domain is theoretically possible, but is complex and requires significant computational effort. This study presents an alternative approach of including drag force in LS-DYNA® without the need to employ any form of computational fluid dynamics (CFD). Using the keyword *LOAD_MOTION_NODE, the velocity component of each node of the roof fabric elements is used as a variable to calculate the nodal drag force using the dynamic pressure equation. The calculated drag force is then applied at each time step as a nodal force that is opposite to the direction of motion and parallel to the element normals that represent the roof fabric. Results from a validation study using this approach are presented, and a case study involving the response of an arched roof fabric canopy subjected to blast loads is also discussed.
Structural response in fire is complex and can only be properly investigated using finite element analysis considering non-linear geometry and material properties. Full scale fire testing to investigate the real response of structural forms to severe fires represents significant risks to researchers and is also expensive and difficult to undertake effectively. Therefore, computational tools are necessary for the safe design of structures under fire conditions. The majority of the computational tools currently used for structural fire analyses use static solvers. Explicit dynamic solvers such as in LS-DYNA are rarely used even though they are capable of dealing with highly non-linear problems.
Concrete structures are designed and constructed to serve their anticipated service life, generally with minimal consideration of accidental loads such as impact or explosion. The behaviour of reinforced concrete structures under impact loads has been widely discussed in the last decades, however, there are few studies on the behaviour of plain concrete under impact loading. This paper presents a finite element model of plain concrete beams using nonlinear finite element analysis. The numerical results are compared to experimental data taken from an existing study. The experiments consist of drop-weight tests with varying drop-heights. A parametric study is conducted with respect to the concrete material model and mesh size of elements in order to fine-tune the model and to understand the dynamic response of the beam under low-velocity impact load.
Drag Force Simulation on Blast Loaded Fabric Roof