Elastic interactions

When a bolt is tightened it partially compresses the joint members “in its own neighborhood.”  When nearby bolts are tightened later, they further compress the joint in this region. This allows the first bolt to relax a little (lose a little preload). Tightening bolts on the opposite side of the joint, however, might INCREASE preload in some of the earlier bolts tightened on the near side.  These shifts and changes in the elastic energy stored in individual bolts, during assembly, are called elastic interactions.