Dynamic Response Control of a Building Model using Bracings

Construction of tall and flexible structures has become easier now-a-days because of advances in analytical techniques and availability of more efficient materials. However, these structures are more sensitive towards dynamic loadings. Dynamic response of such structures under various excitations can be quantified by displacement and acceleration response time history. Excessive dynamic response of structure leads to substantial damage to the structural components and hence it need to be controlled. Passively, this is achieved by adding either mass or stiffness or both of them. This paper covers experimental study on controlling dynamic response of a building model using two types of bracings, namely, Concentric- and Eccentric bracing. A building model is fabricated using aluminum flats and plates and bracings are fabricated using linear springs of moderate stiffness. A model represented as Single Degree of Freedom (SDOF) system is subjected to sinusoidal excitations of various frequencies through small scale shake table. Acceleration response of a uncontrolled building model (model without bracings) is obtained using accelerometers and Data Acquisition System (DAQ) – LabVIEW 8.0. Displacement response is derived through numerical integration from acceleration response using LabVIEW. Acceleration and displacement response of controlled building model (model with bracings) are extracted and compared with uncontrolled system. Dynamic properties like Natural Time Period and Damping Ratio for both types of bracing systems are obtained and comparisons are made among them. It is found that natural time period and damping ratio of controlled building model is increased as compared to uncontrolled system due to stiffness addition. Displacement and Acceleration response are reduced appropriately for controlled system as compared to uncontrolled system.