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RE: Positive connection

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Maybe not structures, but I believe there were plenty of RTUs which experienced 
 net uplift on top of buildings during 1994 Northridge.

T. William (Bill) Allen, S.E. (CA 2607)
A L L E N   D E S I G N S
Consulting Structural Engineers
33171 Paseo Cerveza, Suite 221
San Juan Capistrano, CA 92675
V (949) 248-8588 • C (949) 374-1536

-----Original Message-----
From: seaint-seaosc(--nospam--at) [mailto:seaint-seaosc(--nospam--at)] On 
Behalf Of Steve Gordin Sent: Tuesday, April 22, 2014 8:18 AM
To: seaint-seaosc(--nospam--at)
Subject: Re: [SEAINT-SEAOSC] Positive connection

Neil and Larry,

AFAIK, out of 7 bridges collapsed during the Northridge earthquake, only one 

- the I-5 to I-14 interchange - can be somehow linked to the issue discussed. 

This collapse, however, is mostly attributable to the combination of the 
skewed/curved geometry, short in-span expansion joint seat, and the flexibility 
 of the columns (Bridge Design Handbook, Proceeding of NEHRP…).  This, and 
 several other, collapses were caused not by the lack of the gravity support 
 (or positive connection, for that matter), but rather by a design flaw - 
insufficient width of the abutment/joint seat.   Subsequently, the code 
increased the requirements for the seat widths and introduced other measures 
 against such failures.

To my knowledge, despite vertical PGAs, there are no records of the net 
uplift on the bridges - or, for that matter, on any structures - during the 
 Northridge earthquake.  This is why I am so interested in - and would

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