Analytical Behavior of Conventional and Virtual Outrigger Structural Systems by Using Modal Pushover Analysis

The population census conducted by the BPS – Statistics Indonesia in September 2020 revealed that Indonesia's total population was 270.20 million, an increase of 32.56 million people from the population census conducted in 2010. This circumstance influences the shortage of residential land. However, vertical land use through a series of outrigger structures can be a solution. This is due to the structural system's effectiveness in increasing stiffness and decreasing lateral drift, particularly when used in structures with more than 40 stories. In practice, there are two types of outrigger structural systems, i.e. conventional and virtual outrigger structural systems. Both require stiffeners, but their behaviors are distinct. Hence, in this study, they were examined using the modal pushover analysis approach, with a focus on the behavior of outrigger beams against various heights between floors. The study concludes that the height between the floors of an outrigger structural system is directly proportional to the drift, displacement, and stiffness, but inversely proportional to the level of performance. In addition, the number of structural members that fail is inverse to their stiffness. Comparatively, the virtual outrigger structural system is more effective than the conventional outrigger structural system.