Earthquakes have proven to be very disastrous to the mankind costing thousands of lives and billions of dollars worth property damage. Making earthquake resistant structures have always been a challenge to engineers. Researchers have come up with numerous strategies to build earthquake resistant structures. Implementing control devices in structures is one among those strategies which has proven to be effective and worthwhile. Control devices can be broadly classified into four categories, namely, passive, active, hybrid and semi active. The purpose of this research is to develop semi active controls by varying the damping coefficient of a passive control device in a controlled manner using an algorithm based on fuzzy logic. First, a semi active fuzzy logic based Tuned Mass Damper (TMD) is developed and tested on a one storey structure subject to free and forced harmonic vibrations and its performance is compared with a passive TMD with the same parameters. Comparison is also made between these two TMDs by testing them on a 15 storey structure for the same kind of vibrations. Later these TMDs are tested on a number of one storey structures with different fundamental frequency subject to Kocaeli earthquake motion and their performance is again compared. This way, the effectiveness of TMDs to resist earthquake vibrations in a structure is studied along with establishing the superior performance of a fuzzy TMD over a passive TMD.
Base isolators have proven to be a better passive control device compared to TMDs in suppressing earthquake induced vibrations in a structure. This research also attempts to develop a fuzzy logic based semi active base isolator that outperforms the current state of the art semi active base isolator which uses a control algorithm which is of bang-bang in nature. Tests are done on a two degree of freedom structure for four different earthquakes, namely, El Centro, Hachinohe, Kobe and Northridge with these two controllers and the performance of the developed controller is compared to the performance of the controller discussed in the literature to establish the superior performance of the new controller. Finally, recommendations are made on what else can be done for further research and how this fuzzy logic based semi active controllers can be further improved.