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RE: Existing Bar Joist Capacities and Problems.....

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A word of caution for joists with bar webs..... I have seen some joists that change bar web diameters at interior panels. They may not all be the same.

Another option is to add joists between the existing joists. 

Jim K.

-----Original Message-----
From: Stuart, Matthew [mailto:mstuart(--nospam--at)schoordepalma.com]
Sent: Tuesday, July 13, 2004 8:53 AM
To: seaint(--nospam--at)seaint.org
Subject: RE: Existing Bar Joist Capacities and Problems.....


1. J-series were manufactured up through 1963. H-series were manufactured beginning in 1961.  So in the absence of any confirmation of the series type (and designation) you should assume the lightest joist designation for both series and then the joist that provides the lower allowable uniform load capacity. To do other wise would be unconservative.
2. a. See flow chart below for recommended procedures when it comes to strengthen joists (or try this link: http://pdhonline.org - Course S117)
b. You can usually get away with reducing the span of an open web joist that has bars for the web members.  Joists that are constructed with angle web members are a little more problematic because the manufacturer may have provided smaller sections for the tension web members than that provided for the compression web members.  If the revised span condition results in a tension member being used as a compression member you may have problems.



D. Matthew Stuart, P.E., S.E.
MASCE/SEI/BPAD
Senior Project Manager
Schoor DePalma Engineers and Consultants
200 State Highway Nine
Manalapan, NJ 07726
732-577-9000 (Ext. 1283)
732-431-9428 (Fax)
908-309-8657 (Cell)
mstuart(--nospam--at)schoordepalma.com

-----Original Message-----
From: Daniel Boltz [mailto:dboltz(--nospam--at)1st.net]
Sent: Tuesday, July 13, 2004 10:17 AM
To: seaint(--nospam--at)seaint.org
Subject: Existing Bar Joist Capacities and Problems.....

I have a copy of SJI's 60-year manual and know the general procedure for identifying the existing bar joist designation.  However, it is becoming quite common to identify a bar joist but not be able to determine whether the joist is an H-Series or a J-Series. 

1. When no tags can be found to identify the joist, is there another procedure besides testing a sample to see if it is 50 ksi or 36 ksi material?

2. For renovation projects, many times a corridor or office use is required on bar joists that will only support a live load of 40 to 50 psf.  What are the proper procedures for strengthening a bar joist to support the IBC 2000 required loads of 50+20 psf for office space and 80 psf for corridor space?  Is it acceptable to cut the span in half and build a new joist seat or would the possible reversal of forces cause problems for the "new" joist span?

Thanks.
Dan   




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