Risa 3d Multispan Jack Beam

[Attention2Details]

I’m doing a bridge jacking and the assembly has a top and bottom jack beam. My question is that is there any way to model a support with a reaction for -Y loads only. In other words, bearing reaction only so that it doesn’t restrict uplift? I am analyzing another engineers design and their propitiatory software accounts for residual moment resulting in uplift in the middle of the span. I suppose a compression spring with a constant of 50000 would probably act similar but does not give a reaction value during analysis.

 

[dold]

Try using a Compression Only member instead of a spring? Not sure why a spring would give zero reaction though. Is the model stable otherwise?

 

[JoshPlumSE]

I believe you have the option of using a compression only spring as well. Just set the compression spring stiffness to 1E6 and you should have a pretty rigid, compression only support.

Dold's idea should work too. I just usually reserve that for when I want a support that isn't aligned with the global axes.