hi expert.. i am begginer in Hypermesh and Lsdyna interface. now i am running for bus rollover structure analysis using hypermesh and LSDyna interface. i already put all the boundary condition/material/properties/load body/contact and others. for these im using unit mm/s/tonne and i also check for consistent unit all the time. after calculation is complete.. the bus structure is not falling down but the model is going up and horizontally (likely fly away).. in my boundary condition, i put the load body in Y-direction and its pointing vertically.. my load body curve is X; 0 y: 1 X; 2 y: 1 the gravitational accelaration is 9810 mm/s2 and time termination is 2s.. contact used: surface to surface/ single surface/ node to surface and rigiwalls planar. so what can i do to make the bus structure is falling down.?? hope somebody can help me..