COMPARISON OF NON-CONVENTIONAL STRUCTURAL PATTERNS FOR TALL BUILDINGS: DIA-GRID, HEXA-GRID AND TRIHEXAGONAL-GRID STRUCTURAL SYSTEMS by Sukhvir S. Gill
The development of different structural systems has led to an improved status of high rise buildings. The commonly used lateral load-resisting systems are braced frames, rigid frames, with super columns containing a core, supported outriggers and different tubular structures. Among all systems, the Dia-Grid structural system has attracted the attention of designers for tall buildings, due to its tubular behavior and modifiability in architectural planning. In the Dia-Grid structural system, lateral loads are resisted by axial action of the inclined columns (diagonal) compared to bending of vertical columns in framed structure. Another innovative structural system, called ‘Hexa-Grid’, has been added to the tubular structural systems. This structural system is inspired by the ‘Beehive’. Several hexagons of height equal to story height in a unique way as in Beehive are arranged in this structural system. Hexa-Grid has enough potential of force redistribution to resist progressive collapse due to its special configuration. At last, Trihexagonal-Grid structural system is a combination of Dia-Grid and Hexa-Grid structural system. Not many structures have been done using Trihexagonal-Grid Structural System. In the present study, all these three structural systems have been compared to their structural behavior and costs. For this, a typical square floor plan of 30 m × 30 m was considered for each type of structural system. Each structural system consisted 40, 50 and 60 number of stories with a storey height equal to 3 m. Typical beam detail was considered for each type of structural systems. The vertical members located at four corners of both inner and outer tube were kept same for the three structural systems under consideration. The angle of inclination of diagonal structural members was taken as 67° in each type. The present study is based on the non-linear dynamic analysis carried out using ETABS Software. The structures were subjected to El Centro (1940) and Burma Border (1988) Earthquake ground motions, recorded in Southern California and 200 miles from Shillong India. The main step was that, which size of columns to be selected in the present study. For this, the size of columns for each type of structural systems was decided with the help of Auto-Optimization tool in ETABS Software. 10-15 number of different column sections which were used in previous studies were selected and grouped up to 20 stories. Then auto optimization tool gave the optimized section according to required load conditions. So, these optimized sections were used in the present work. At the end, it was found that the top storey displacement and storey drift was found the maximum in the Hexa-Grid structural system as compared to Dia-Grid and Trihexagonal-Grid structural systems. The cost of Hexa-Grid structural system was less than other two structural systems. It was concluded that Hexa-Grid structural system is giving us all requirements at a better economy. Though Dia-Grid, Hexa-Grid and Trihexagonal-Grid are also safe, stable and aesthetic as the steel consumption in them is more, it is comparatively expensive.