This paper presents an exact structural static reanalysis method for l
ocally modified structures. Through the introduction of structural rig
id body motion eigenvectors, the generalized structural compliance mat
rix can be obtained and the original stiffness equation is transformed
into a linear system of much lower order. The general solution of dis
placements can be expressed prior to any assignment of boundary condit
ions. For a structure with given boundary and loading conditions, the
displacements can be obtained by solving this linear system. For local
ly modified structures, the structural compliance matrix can be adjust
ed quickly. This static reanalysis method can be used for structures w
ith modifications on structural elements, boundary and loading conditi
ons, either independently or in combination. Two test examples are pro
vided in the paper to prove the efficiency of the method.