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# Calculation help for thru bolt in old double wythe brick wall

## Calculation help for thru bolt in old double wythe brick wall

(OP)
I am looking for some help specifying through bolts in old (1940s) clay brick for a 2x roof ledger.  Double wythe, 8 inch wall.  The main loading will be from snow load.  I am probably going to use somewhere between 300-600 psi for the old brick just because it is old based on another forum - it is in fair condition.  I know I need to check:

1 - brick bearing
3 - washer pullout
4 - ledger bearing

As an alternative, someone referenced that you can use L-bolt values.  Does anyone have an example they could post?  I am looking at about 240 PLF loading on the ledger.

Thanks!

### RE: Calculation help for thru bolt in old double wythe brick wall

What kind of bearing distribution are you going to assume for the brick bearing check?

Also what is the basis of your allowable bearing stress range?

### RE: Calculation help for thru bolt in old double wythe brick wall

Is the wall laid with a collar to make the two wythes act together for most uses?

If it is bonded, how far away would bonding units be?

The clamping action of a through bolt could crush the wall if the wythes are separate.

Dick

Engineer and international traveler interested in construction techniques, problems and proper design.

### RE: Calculation help for thru bolt in old double wythe brick wall

Some references from renovation job I did in Everett about 7 years ago:

1.  1997 UBC, Section 403 and Appendix Chapter 1

2.  "Guidelines for the Seismic Retrofit of Existing   Buildings", Chapter 1

3.  City of Tacoma, "Seismic Restoration of Buildings", February 3, 1999

Also, here is half of an 11X17 page with some values you can use.  I'll post the other half of the page in my next post.

Mike McCann
MMC Engineering
Motto:  KISS

### RE: Calculation help for thru bolt in old double wythe brick wall

(OP)
abusementpark - this is a common bond wall (with header course every 6-7 courses) and appears to be partially grouted between wythes, so no real collar.

msquared48 (Mike) - thanks for the references and Tacoma printout!!!

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