*Article* **Shared Tuned Mass Dampers for Mitigation of Seismic Pounding**

#### **Rajesh Rupakhety, Said Elias \* and Simon Olafsson**

Earthquake Engineering Research Centre, Faculty of Civil and Environmental Engineering, School of Engineering and Natural Sciences, University of Iceland, Austurvegur 2a, 800 Selfoss, Iceland; rajesh@hi.is(R.R.);simon@hi.is(S.O.)

 **\*** Correspondence: said@hi.is

Received: 17 January 2020; Accepted: 6 March 2020; Published: 11 March 2020

**Abstract:** This study explores the effectiveness of shared tuned mass damper (STMD) in reducing seismic pounding of adjacent buildings. The dynamics of STMDs is explored through numerical simulations of buildings idealized as single and multiple degree of freedom oscillators. An optimization method proposed in the literature is revisited. It is shown that the optimization results in two different solutions. The first one corresponds to the device being tuned to one of the buildings it is attached to. The second solution corresponds to a very stiff system where the TMD mass hardly moves. This solution, which has been described as an STMD in the literature, is shown to be impractical due to its high stiffness and use of a heavy stationary mass that plays no role in response mitigation but adds unnecessary load to the structure. Furthermore, it is shown that the second solution is equivalent to a viscous coupling of the two buildings. As for the properly tuned solution, i.e., the first solution, sharing the device with an adjacent building was found to provide no added benefits compared to when it is placed on one of the buildings. Based on results from a large set of real earthquake ground motions, it is shown that sharing a TMD mass with an adjacent building, in contrary to what is reported in the literature, is not an effective strategy.

**Keywords:** adjacent buildings; seismic pounding; tuned mass damper
