Response of reinforced concrete moment resisting frames towards vertical ground motion

Conventional seismic analyses of buildings primarily focus on horizontal earthquakes, while vertical seismic motions have received less consideration. However, vertical earthquakes can sometimes be more severe than horizontal earthquakes. This study aims to compare the response of buildings to vertical earthquakes, considering ASCE 7-16, IS 1893:2016, and NBC 105:2020. It also investigates the variations in the responses of the structures with variations in height and plinth area. Furthermore, it compares the graphs and results of quasi-static pushover analyses with response spectrum analyses. It was found that ASCE 7-16 has a lower impact on vertical earthquakes, while IS 1893:2016 has a more significant effect than NBC 105:2020. Similarly, buildings of varying heights and plinth areas were modeled in ETABS. Normalised displacements were calculated from top-story maximum vertical displacements, and pushover curves were generated. Both procedures imply that the effect of vertical earthquakes increases with a decrease in the plinth area and height of the building. Additionally, a lower output time step size in quasi-static pushover analysis revealed yielding at lower displacements, and a lower load scale factor resulted in lower damage measures in the building.