What do you mean by shockwave? Are you modeling a blast from some sort of explosive? If so, one way to model a blast load (pressure) on a structure without explicitly modeling the explosive and the air is to use the keyword *LOAD_BLAST_ENHANCED to apply a pressure load directly on the structure. You will have to define the equivalent mass of TNT with the “M” parameter for this keyword. You will find more information here:
You will find more papers by searching on dynalook.com
If you know the pressure vs time profile for each element of the structure or if you can assume a constant pressure vs time profile for a group of elements, you can apply the blast load pressure using one of the following keywords:
You can define the pressure vs time profile using LCID and *DEFINE_CURVE. See the LS-DYNA user manual vol I for more information:
Let me know how it goes.