For Response spectrum analysis using Staad Select series 6 version, sum of nodal reactions are higher than base shear value reported in output file. Is there any command to match nodal reactions and output base shear?
The wiki below has the answer to your question
https://communities.bentley.com/products/ram-staad/w/structural_analysis_and_design__wiki/29001/base-shear-does-not-match-the-summation-of-shears