Diagrid Systems in High-Rise Reinforced Concrete Frame Structures

The performance and prolongation of a building is mostly influenced by the loads it undergoes in its life span. The load can be both vertical and lateral, and it becomes more critical as the building height increases. In this study, earthquake load is considered as governing lateral load. For the structure to withstand the design lateral load, it should be well profound in capacity and ductility. There are numerous lateral load resisting systems to minimize building drift and deflection that have undergone many evolutions and continue to evolve. Among various innovative techniques, the “diagrid” system is particularly notable. This approach in structural engineering employs a network of triangular elements along the building’s perimeter, effectively resisting both vertical and lateral loads. The performance and efficiency of the diagrid system are significantly influenced by the angle at which its diagonal members are tilted and the overall shape of the building. This study examines reinforced cement concrete buildings of mainly three different heights—10, 18 and 26 stories—to identify the optimal diagrid inclination angle. In case of response spectrum analysis, the results are derived from building heights varying from 10 to 50 stories. There are six varying diagrid angles, viz. 50°, 60°, 71°, 74°, 76°, and 78°, which were analyzed for each building type using linear static and dynamic methods as preliminary analyses, followed by nonlinear static pushover and time history analysis. Nonlinear time history analyses were performed in OpenSees using 10 scaled ground motion records with varying peak ground acceleration from 0.1 to 1.0 g to generate fragility curves. In this study, the effective diagrid angle primarily ranged between 50° and 71° as determined through various analytical methods. The fragility curves were developed for three performance levels: immediate occupancy, life safety and collapse prevention.