Burj Khalifa was designed by Adrian Smith then of Skidmore, Owings and Merrill (SOM), whose firm also designed the Willis Tower and the One World Trade Center. Hyder Consulting was chosen to be the supervising engineer with NORR Group Consultants International Limited chosen to supervise the architecture of the project. The design of Burj Khalifa is derived from patterning systems embodied in Islamic architecture, incorporating cultural and historical elements particular to the region such as the spiral minaret. The Y-shaped plan is designed for residential and hotel usage. A buttressed core structural system is used to support the height of the building, and the cladding system is designed to withstand Dubai's summer temperatures. A total of 57 elevators and 8 escalators are installed, with the elevators having a capacity of 12 to 14 people per cabin.