RETROFITTING OF RC BUILDINGS
Seismic load path in a building:
•The inertial forces originating throughout the building are first transferred to horizontal floor diaphragms,
•The diaphragms transfer these forces to vertical framing system resisting lateral loads;
•The vertical framing system consisting of beam-column frames and shear walls, transfers the seismic force to foundation and supporting soil.
If there is a discontinuity in load path, the building is incapable of transferring the load to ground and it is unable to resist the lateral load during earthquake, irrespective of strength of existing members.
The common examples of such building are those in which shear walls or columns are not started from ground but started at first floor large open spaces at ground floor for commercial purposes. Such columns are commonly known as floating columns. In such buildings, the first floor beams are subjected to very high forces as the forces from floating columns/shear walls are transferred to other columns and walls through these beams.