Yeah his presentation was very interesting. His perspective/evaluation of the structural failures from an engineering standpoint was quite eye opening. A lot of structures failed under relatively low wind loads. The Franklin Tech building especially. I remember seeing some before photos of that building, and it appeared to be a very strong, well built building. Tim's survey revealed some interesting/startling weaknesses in the structure of that facility.
After Tim's presentation he answered a few questions from the audience. One question brought up the impact on how much debris loading had on structural integrity. Also, the extreme amount of debris swirling in the large tornado no doubt contributed to the accelerated failure of structures that may not have failed, or failed as quickly without the aid of added wind-blown debris. Such a large tornado moving over a densely populated location will no doubt lead to greater damage than would normally be expected relative to wind velocity, as the added debris will surely aid in damage/wind load on structures within the circulation. All of that could conceivably open a big can of worms on how much debris loading in an urban environment can impact EF-scale values in a positive direction, but in the end all that really matters to most is the damage the tornado does (EF scale damage).