I created a structural model of a laced strut using plate elements. To study second order effects of bow imperfection, I applied a joint displacement of 20 mm in a SAP 2000 v18 model. When the analysis was completed, I double checked the results and found a large joint reaction in the range of 300,000 kN at the joint with applied displacement. Elsewhere, joint reactions do not exceed 1,000 kN.
The model ran with no warnings or errors. I expected the sum of all forces to be zero for equilibrium, but that seems not to be the case. The global displacement looks fine with the laced strut bending to the specified displacement.
- Should all joint reactions sum to zero, if nodal displacement is applied?
- Should the joint reaction at the node with specified displacement be disregarded?