Seismic Response Of Soft Story Rc Building Using Fluid Viscous Damper

Abstract

Due to the various functional purposes, the buildings nowadays have open (not containing infill wall) ground floor to accommodate parking, reception lobbies, bank branches, stores, restaurants, offices and the upper story are used as dwellings. Similarly, open at intermediate floor levels are also in practice for the purpose of restaurant, gym hall, yoga center etc., especially in city area. The columns in the soft story will stress more than those in other story because of the less rigidity in soft story. Failure of soft story building in past earthquakes are mainly due to the higher drift ratio at soft story levels. NBC 105: 2020 states that the ratio of the inter-story deflection to the corresponding story height shall not exceed 0.025 at ultimate state and 0.006 at serviceability limit state. Inter-story drift is an indicator of structural damage as story drift beyond certain levels may cause damages to the structural systems. Passive energy dissipation devices like fluid viscous damper activates only when the two ends of the device are in motion and dissipates the kinetic energy developed during earthquake into the heat energy thus reducing the building response. This thesis aims to investigate whether the fluid viscous damper in soft story reduces the responses in building during earthquake and lie within a limit defined by NBC 105:2020. Ten story reinforced concrete moment resisting frame building with 4 bays having 5m span in both direction and soft story at various floor levels located in seismic zone having zone factor 0.35 and soil type D is considered for this study. Total five building models are analyzed for cases a) without fluid viscous damper and b) with fluid viscous damper. Infill walls are modeled as a compression only equivalent diagonal strut. Non-linear model time history analysis (FNA) is carried out for all the models and results are compared. The study shows minimum 25% and maximum 39% reduction in base shear after addition of fluid viscous dampers at building with soft story at ground floor level and soft story at ground and second floor level respectively. Comparing the maximum roof displacement, it is seen that up to 49% decrease in roof displacement after the application of fluid viscous dampers in building. Similarly, story drift ratio decreases from 2.745% to 1.51%, 3.645% to 1.6%, 3.19% to 1.756%, 2.5% to 1.2% and 2.7% to 1.32% for buildings with soft story at ground floor, ground and 2nd floor, ground and 4th floor, ground and 6th floor and ground and 8th floor level respectively.