The code really doesn't give a cut off point as to when you have to do a wind tunnel test. It just says where a structure is susceptible to things like vortex shedding, galloping, and so on. (And there are some means to estimate vortex shedding. See this thread for some ideas:
At 60 stories I'd definitely be thinking about it because (for one thing) ASCE 7-10 doesn't even have applicable wind coefficients once you get 500' above the ground. And I'd be nervous about any interpolation (via formula) above that.
In 'Steel, Concrete, & Composite Design of Tall Buildings' (2nd ed, by Taranath, p.234), they admit it is hard to decide when to do it....and give these factors as a "guide in making a decision" (i.e. you may want to do it if your building falls into any of these categories):
1. The building height-to-width ratio is greater than about 5; i.e. the building is slender.
2. Approximate calculations show that there is a likelihood of vortex shedding phenomenon.
3. The structure is light in density on the order 8 to 10 lbs/ft
2.
4. The structure has very little inherent damping, such as welded steel structure.
5. The structural stiffness is concentrated in the interior of the building, making it torsionally flexible.
6. The calculated period of oscillation is long, on the order of 5 to 10 seconds.
7. Existence of unusual near field conditions that could create torsional loads and cause strong buffeting action.
8. The building is sited such that predominant winds blow from a direction most sensitive to the building oscillations.
9. The building occupancy is such that the occupants' comfort plays a more predominant role. Occupants in high-rise apartments, condominiums, and hotels are likely to experience more discomfort from building oscillations than those in office buildings.
