Several series of wind tunnel tests (figure 47) were conducted by Rowan Williams Davies & Irwin Inc. (RWDI). A wind tunnel testing increases accuracy, takes into account building and site specific conditions (building's shape and orientation, the roughness of the surrounding terrain, local topographic effects, aerodynamic interactions with nearby buildings- characteristics that cannot be simulated by analytical models due to the high complexity and randomness that they affect the structure). Furthermore, after performing a wind tunnel test, one can decrease the construction cost by minimizing the codes' conservatism (cost savings of $500,000 or more have resulted), increase safety and have a better understanding of torsional effects.