content: WTC7 was quite poorly designed. It's layout was rather unorthodox even with regards to WTC 1 and 2. While it utilized design elements of 1 and 2, a central core with exterior columns, the central frames were not entirely orthogonal with one another, and it utilized cantilever girders to transfer story loads. Because cantilever systems are so reliant on connection and support design, we try to avoid using them in practice. When all said and done, the way the structure was framed made it incredibly susceptible to damage, as when the first half of the penthouse fell in, it effectively destroyed half of the structural core of the building. So while it was sufficient for what it was designed for, it was not at all resilient.