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RE: PRECAST / PRESTRESSED CONCRETE

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Thanks Mr. Gilligan. 

It's as if saying "sorry" to the owners of prestressed concrete building
structures.
Well, we both feel the same with regards to using steel but here in the
Philippines, the problem is with the welding works. That's where the
question of economy comes in. It's hard to find a good steel contractor with
a reasonable price for its labor and also conducting tests here is a quite
expensive process, if you are building say a two-three storey structure.

But I'm still puzzled with the prestressed buildings. I tried to do a sample
structure and modelled it and designed it using prestressed concrete (by the
book) and the results are not good. And even if it was good theoretically, I
would not use it. I'd better go for steel and RC.

Anyway, can anybody help me how to find downloadable reports regarding
prestressed buildings subjected to earthquakes? Where could I find them ? I
hope they're free of charge cause if you convert the peso to a dollar this
days, thats a lot of money here in the Philippines. Thanks guys !!!

A. Yango, CE/SE
TMP



> ----------
> From: 	Mark Gilligan[SMTP:MarkKGilligan(--nospam--at)compuserve.com]
> Reply To: 	seaint(--nospam--at)seaint.org
> Sent: 	Friday, May 14, 1999 10:28 AM
> To: 	INTERNET:seaint(--nospam--at)seaint.org
> Subject: 	RE: PRECAST / PRESTRESSED CONCRETE
> 
> Mr Yango
> 
> 
> Remember that the actual seismic displacements will be significantly
> larger
> than those calculated using the code level forces.  Thus when the
> earthquake occurs there will be extensive cracking in the concrete.
> 
> The problem withprestressed structures is that when the concrete cracks
> extensively on the compression face the tensioning will not be very
> effective and the section will deteriorate rapidly.
> 
> Historicaly the problem with precast concrete is that the connections are
> not as good as monolythic concrete.  As a result these systems have a
> tendency to fall apart.
> 
> Recently several systems have been developed to overcome these problems. 
> What they have done is to design the connections as fusable links that can
> absorb energy and tie the members together while protecting the rest of
> the
> member from excessive loads.
> 
> I still believe that properly designed steel structures will probably
> perform better.   having said that I would probably consider using one of
> the new systems if the circumstances were favorable and the client
> appreciated the risks.
> 
> I believe that the 1997 UBC has a number of new provisions dealing with
> prestressed and precast members in seismic areas.
> 
> 
> 
> Mark Gilligan
> 
> 
>