Over the past months, I have been modelling a 27 story RC building with shear walls - columns - beams using STAAD.pro 2002 and am satisfied with the results. My structure is being modelled for UBC97 Zone 4 seismic loads (which STAAD is able to generate quite nicely, too).
I have used both the column - beam only simplification and then moved on to modelling the shear walls of the building using FEM technique, continuosly checking the results between one analysis and the other. Once satisfied that they were close enough, I have continued with the FEM only.
To address the issues you mentioned and were brought up by HILLBILLY, yes I am satisfied that STAAD is handling the in-plane stiffness properly.
By the way, I have NOT used the Master/Slave, but have kept a close watch on the deformations in my diafragms, both vertical and horizontal, finding them to be acceptable.
I would suggest 4 things:
1. Upgrade to STAAD.pro 2002. I have no experience with 2000, but from reading the postings of others and FAQs on their website, it seems they have improved many things in the last couple of years.
2. Browse in the "Research Engineers STAAD Products" FORUM for a lot of good info on STAAD.
3. Purchase the Research Engineers one year technical support package. I have bombarded them with questions and have found them to be very helpful in taking me from a complete novice to a pretty good user of their product in this time.
4. Read their manual, electronic help and the FAQ on their website. I have also found them to be quite useful. Their Example No. 9 in the electronic help (STAAD.pro 02 version) has an example of vertical RC shear wall. In migrating from the Beam-Stiff Beam-Col. analogy to Shear Wall, I used their example as a test case and modified its geometry and load conditions considerably, until satisfied I was getting reasonable answers. Then I used the technique to model the shear walls in my structure.
PS. A proposito, habla usted español? Supuse que por su apellido es de descendencia latina. Creo haber visto su seudonimo en otros foros anteriormente. Saludos R. Monterroso.