The effect of vertical near-field ground motions on the collapse risk of high-rise reinforced concrete frame-core wall structures

According to the observations of past earthquakes, the vertical ground motions have had a striking influence on the engineering structures, especially reinforced concrete ones. Nevertheless, the number of studies on their aftermath is insufficient, and despite some endeavors done by researchers, there is still a shortage of knowledge about the inclusion of vertical excitation on the seismic performance and the collapse probability of RC buildings. Hence, the variation in the collapse risk of three high-rise RC frame-core wall structures when they undergo bi-directional ground motions is discussed. In this paper, incremental dynamic analyses are carried out under two circumstances, including the horizontal (H) and the combined horizontal and vertical (H+V) earthquakes, and the seismic fragility curves are derived. The inter-story drift ratio corresponding to the onset of collapse has also been defined. The buildings collapse risk under the two circumstances is obtained from the risk integral. Results indicate that in the H+V state, structures meet the collapse criteria for lower intensity measures. Thus, the collapse risk increases as the structures are subjected to bi-directional seismic loads, and the consideration of this effect leads to a more accurate evaluation of buildings seismic performance.