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RE: PRECAST / PRESTRESSED CONCRETE

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Good day fellow ENGINEERS !!!

	During my college days, I was able to come up with an undergraduate
thesis entitled "Design Aids for Prestressed Concrete Beams". It's like the
AISC Manual and ACI Manual . It includes charts for determining the
reinforcements (prestressed and non-prestressed) and prestressed forces.  I
was a "believer" of prestressed concrete back then. But when I started
working, I did not used prestressed concrete for the structures that I
designed. They were mostly concrete and steel. The reason was that for
earthquake loading, the performance of prestressed concrete was not
appreciable. (My mentors told me that) And I believed in that too.

	But I see a lot of prestressed building structures under
construction. Their beams and girders are prestressed. For beams, I think
it's ok. They are only subjected to gravity loads. But for girders, how
would they perform?
	Even if partial prestressing is employed and reinforcing bars are
used, would the structural system perform well? What would happen under
cyclic loading and stress reversals? The moment at the girders due to
prestressing (midspan and ends) would add to the earthquake forces .
	How can that be counteracted?

	I know that many out there have experienced designing prestressed
building structures. Please give me some feedbacks and comments.
	Maybe my stand on prestressed concrete would change. 

	Thanks.

	A. Yango
	Civil / Structural Engineer
	Toyota Motor Philippines