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RE: 1930's Poured in Place Concrete Building

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Nels,

The deterioration is higher up on the walls. I was told by the field tech from Earth Systems out here that this was similar to the problems found in the Santa Monica area. The walls were formed using a sloppy slurry and the contractors used local sand as in Santa Monica they often used beach sand to form the foundations. The sand in this area is highly mineralized and this as deteriorated some of the reinforcement that was removed in the cores taken.

In short, the walls are probably proficient to take shear in the long walls at the properly lines between buildings. I can deal with the shear at the front an back by moment frames and Gunnite and the distance between the front and rear walls is around 40-feet so it is not a large building.

 

It’s held up well, but my thought is to keep the remodel independent within the shell and use it as a secondary support for older structure with the exception of taking care of the soft stories.

I haven’t seen any of these in L.A. and guess they are more common in the Desert Areas where building materials other than wood were not easily obtainable in the depression era.

 

Regards,

Dennis

 

-----Original Message-----
From: Nels Roselund, SE [mailto:njineer(--nospam--at)att.net]
Sent: Thursday, November 20, 2003 9:39 AM
To: seaint(--nospam--at)seaint.org
Subject: Re: 1930's Poured in Place Concrete Building

 

Dennis,

 

A change in occupancy may result in a requirement that the Building comply with the modern Building Code -- see 1997 UBC Section 3405.

 

Figure out the reason for the deterioration.  Most likely, is poor drainage -- moisture that is not drained sway from the building can saturate the base of the wall and rise by capillarity until it makes its way to the wall surface and evaporates.  In this case, the culprits causing deterioration are salts dissolved from the soil or concrete that crystallize when the moisture evaporates.  The crystals form within the surface of sound concrete and break it up leaving efflorescence on the wall, and fine dust of deteriorated concrete on the ground -- which will probably be blown away between storms, but will probably remain at the base of the wall inside.  Include stormwater control in the project.  Also, look for evidence of corroded rebar -- this causes cracking that follows the rebar pattern, and also causes spalling of larger pieces of debris that will not get blown away.  Expose corroded rebar and re-embed it in fresh mortar before you cover it all up and hide the problems with gunite.

 

[Dennis, thanks for the personal note -- I'm looking forward to hearing from you when you get the chance.]

 

Nels Roselund
Structural Engineer
South San Gabriel, CA
njineer(--nospam--at)att.net