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[SEAOC] Re: [SEAOC] Footings' Tie Beams[Subject Prev][Subject Next][Thread Prev][Thread Next]
- To: seaoc(--nospam--at)power.net
- Subject: [SEAOC] Re: [SEAOC] Footings' Tie Beams
- From: JRisha(--nospam--at)aol.com
- Date: Mon, 17 Jun 1996 00:40:26 -0400
Both the 91 NEHRP and the 90 SEAOC Blue Book, specify that the ties are required when using deep foundation systems, such as piles, caissons, and piers. If you are using spread type footings, it is good practice to tie the footings together but it is only required in zones of highest seismicity or for buildings of essential characteristics, such as a hospital, school, police and fire stations, and buildings with large number of occupants, founded on bad soil. The requirement really is intended for deep foundation types. The reason being that in the eventuality that there is normal soil settlement, earthquake induced consolidation, or liquefaction, the top portions of the piles and pile caps will be exposed with no lateral support; by providing the ties the piles and caps act more like columns and with the tie beam they will act as a frame. Another reason for the ties is to ensure that the building foundations act as a unit, minimizing the differential movement. If you are on good soil, such as bedrock, the supporting soil will act as unit and there is no need for ties, especially that in good soil you will not use deep foundations. Also, the slab can provide that lateral support, with or without additional (slab embedded) reinforcement to create a tie beam. Janah A. Risha, S.E. ...
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