A three-storey half scale Reinforced Concrete (RC) open ground storey building is fixed with yielding type X-shaped metallic (elasto-plastic) damper at the ground storey level, to study the seismic response characteristics. Experimental studies are carried out using the 4m x 4m triaxial shake table facility to evaluate the seismic performance. Initially the reinforced concrete building is tested for different earthquake inputs in the shake table. During the test, the cracks and hinges are formed in various locations of beams, columns, beam-column joints and infill walls. During the seismic testing, the plastic failure cracks (plastic hinges) are formed in the columns and beam-column joints of the ground storey. The seismically damaged RC building is retrofitted. Two types of retrofitting techniques have been developed. Type 1 is the local retrofitting of columns and beam-column joints in the ground storey using Geopolymer concretes. Type 2 is the global retrofitting of RC building with Chevron type steel bracing incorporating X-plate damper in the ground storey. The dual functioning of X-plate damper is to improve the global stiffness of building thereby protecting the building during earthquake. In general, earthquake loading induces large displacements in an Open Ground Storey (OGS) structure. During such large displacements, a yielding type elasto-plastic device made of X-shaped metallic dampers performs better. The supporting steel frame of Added Damping and Added Stiffness (ADAS) is of chevron type, serially contributing stiffness to the system. Free vibration tests on OGS RC building with and without yielding type X-shaped metallic damper is carried out. The natural frequencies and mode shapes of the model with and without yielding type X-shaped metallic damper are evaluated.