Problem using SparseSYM

[YuZhang]

Hi guys,

I am building a large tall building model now, which is a 3-D model and has about 10000 nodes. I have used the SparseSYM for dynamic analysis without any problems in my previous models, and I think it is more efficient for large models than the generally used UmfPack. As for my present model, the UmfPack runs relatively slowly for each iteration but gets converged after less than 30 iterations for the most of the time steps; On the contrary, the SparseSYM runs much faster for each iteration but cannot get converged at all after just a few time steps. Moreover, the UmfPack works for the pushover analysis, though relatively slowly, while the SparseSYM could not work for even one displacement step. I am kind of confused of these results. Is SparseSYM sensitive to some elements, or material models, or rigid elements, or something else? Could anyone be kind enough to give me some suggestions upon them? Thanks very much in advance.