Fuzzy semi-active control of adjacent buildings connected with MR dampers under far and near-field earthquakes

Damages caused by the impact of adjacent structures in past major earthquakes have shown the importance of structural control systems to reduce the seismic risk of the impact of structures. Connecting energy dissipation devices to adjacent buildings is a practical and effective approach to prevent collisions as well as reduce the seismic responses of structures, and this issue has been an active research field in recent years. One of the semi-active control methods is the use of MR dampers. These dampers use a magnetic fluid that produces large damping forces in a piston-cylinder system that can be controlled instantly by changing the applied voltage to the damper. The Bouc-wen model has been used to take advantage of the unique properties of MR damper as well as to consider its inherent nonlinear behavior. In this study, to evaluate the performance of MR dampers using a fuzzy control system, three- and nine-story standard structures under seismic excitation of two near-field earthquakes including Kobe (1995) and Northridge (1994) and two far-field earthquakes including El centro (1940) and Kern county (1952) with maximum accelerations of 0.1g to 1g are investigated.The MR damper is connected to the third floor level of the two structures and can produce a controlled force equivalent to 1000 kN. The fuzzy system is designed based on the displacement of the third floor of two structures to reduce the risk of collision of structures as well as reduce seismic responses. the benchmark buildings have been modeled in OpenSees and the fuzzy control system was implemented in MATLAB software. The displacement responses of the third floor of structures are considered as the input value of the fuzzy system and the required voltage of MR damper is considered as the output value of the fuzzy system. In addition, triangular membership functions have been used to determine the degree of membership of input values. In general, the control system designed under far-field earthquakes has shown better performance in reducing the responses of two structures compared to near-field earthquakes. According to the results obtained from the dynamical analysis, the fuzzy system used under far-field earthquakes compared to near-field earthquakes and based on evaluation criteria of J1 (maximum roof displacement), J2 (maximum roof acceleration), J3 (maximum Base shear) and J4 (maximum relative displacement of floors) in three-story building 17.35, 4.94, 3.58, 12.17% and in nine-story building 7.93, 7.05, 0.67, 9.13%  showed better performance, respectively. Also, according to the evaluation criterion of J5, which is related to the minimum required gap between two buildings, the fuzzy system used under far-field earthquakes has shown 9.71% better performance than near-field earthquakes.