Posted by d on September 19, 2002 at 10:51:12:
In Reply to: Re: Future High Rise Design: More Concrete posted by Paul Malo on September 19, 2002 at 10:13:20:
Of course, I agree, and you are quite right that the towers used various diagonals, as in the trusses.
What I am getting at , though, is the degree to which an architect chooses either to “express” or “suppress” the necessary diagonals- and why.
After all, in a large building like the WTC tower, if I understand its construction , the rigidity in the walls was , yes, partially diagonal, but in the covert form of “Vierendiel” strength; the vertical columns being connected by broad webs at each floor. This, in turn, reduced the window aperture; but could not larger windows have been attained, for the same size building, if the same degree of rigidity were accomplished by very large diagonal bracing? Why was this method not chosen?
I simply can’t resist the thought, especially given Yamasaki’s background, that given a choice between huge diagonals ( as in a railroad bridge), or rectilinear construction, (as in traditional Japanese building and, most conspicuously, the Shinto style) he would choose the latter.
Although you have mentioned the traditional roof truss as an example of accepted triangulation, it still seems to me that this is used as an independent element, primarily to resist deflection of ceilings; but the crucial area, that addressed by the diagonal beams in medieval half-timbered construction, is the corner conection between wall and roof . Even in house construction from the last century (before plywood), it’s normal to find diagonals embedded in the walls, “let into” the studs and corner columns.; but again- they are typically covered up.
Its curious to me, that the same customer (to resort to a banal example) who might like an imitation “ beamed ceiling” in his great room- would probably rather not have fake diagonal bracing added to the walls...
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