Effect of Earthquake-Induced Pounding on Adjacent Building Structures with Unequal Number of Stories

Structural pounding among insufficiently separated buildings constitutes one of the main reasons for damage and the possible collapse of structures during severe earthquakes. Building pounding is still not properly understood, as it involves several complex phenomena, leading to unclear patterns for the dynamic behaviour of the colliding structures. Hence, this study considers floor-to-floor collisions between fixed-base reinforced concrete buildings under earthquake excitations. The different number of stories and separation distances are considered to analyze the results in terms of story shear forces and interstory drifts. Finite element models are constructed, considering a fibre-based approach to model the inelasticity at the ends of structural members. Structural pounding was simulated through the use of a viscoelastic impact model, the Kelvin-Voight model. Results showed that the stories above the points of impact experienced 50% to almost 100% increases in interstory drifts and shear force demands, which may lead to brittle failures of the columns. The number and magnitude of pounding forces were higher for upper stories. The case with no gap size did not always lead to the worst scenario, and a separation distance close to the no-pounding case still presented pounding forces of significant magnitude, emphasizing the importance of proper separation of building structures. In conclusion, the buildings in the scenarios with an unequal number of stories were more vulnerable to pounding forces, experiencing higher increases in story shear and interstory drift.