Need Help Requesting a University Engineering Study.

[Jobsaver]

I am interested to form a group of like-minded individuals that can contribute to the effective execution of preparing a request for an engineering study by a university’s engineering department.

The purpose of the study is to determine some practical prescriptive building codes designed to allow for the use of blocks of dimensional lumber as framing anchors for joists, (known as pressure-blocking or power-blocking).

Are any among you, like-minded, having experience preparing such a request, or approaching a university for consideration? Are there any among you any having a personal contact at an appropriate university.

This idea results from the discussion of pressure-blocking within this forum.

"Thanks. That is a good idea that I will pursue. Since joining this forum, I have become motivated and signed up to participate in our COAR, the body of code officials in our state that helps with revisions for our state building code. I have already talked to a couple of guys having influence in this group, and they are receptive to this idea. I believe the students, and a university, might be more receptive to performing a study on behalf of legitimate organizations of building code professionals. Who knows that the like-minded members of this forum can't pull together on this one and back me up on something tangible that can be accomplished despite the other lobbyists and special interest groups. I say we become our own special interest group advocating for common sense building methods that promote efficiency and building craft. If there is anyone reading this that has experience approaching a university asking for such a study, I could use some pointers."

 

[conarb]

Jobsaver:

Put together several hundred thousand dollars in grant money and universities will talk to you, no money no work. In my day it was "publish or perish", now it's "bring in grant money or perish".

Here is an excellent study on decks by Frank Woeste of Virginia Tech (who sometimes posts here), it's a great study, but you see Simpson products used in it because it was funded by Simpson.

 

[Jobsaver]

Here is an excellent study on decks by Frank Woeste of Virginia Tech (who sometimes posts here).

Thanks for the example study.

 

[DRP]

IIRC the authors of that study paid for most of it out of their pockets...

 

[RJJ]

Ya Frank is the man! We need to get him back on this site.

 

[Jobsaver]

I spent a little time today starting a email address list of contacts within applicable university departments . . . a future contact list. I am going to get a few pics together, and basically throw the idea out there and see what happens.

It is my thinking that the simple thing that needs to be accomplished, is to prove whether or not pressure-blocking, according to a specified nailing pattern, will meet uniform floor and ceiling loads, and at what spans, if any, does failure occur.

 

[AegisFPE]

During the senior year of my undergraduate studies, when we were all given our senior project, it did not seem that all involved were donating to the school - perhaps they were. I think it's a win-win for the school to get a project with someone who will take the time to meet periodically with the students, explain the problem needing to be solved, listen to their thought progression, help guide the process, and then critique them at the end of the year. However, the work is done by a group of undergraduate students with limited supervision. They may develop a reasonable theory, but you would probably not get a SE faculty to seal their term paper for you - though you may be able to hire one to review the final product.

 

[Jobsaver]

Roof Framing Connections in Conventional Residential Construction 4.4 MB /PDF

Wrong study, but on the right track. Still looking.

 

[Jobsaver]

Oops! Tried to create a link. Didn't happen.

 

[Jobsaver]

From the

U.S. Department of Housing and Urban Development

Office of Policy Development and Research

Residential Structural Design Guide:

2000 Edition

"EXAMPLE 7.5 Side-Bearing Joist Connection

Given

· A 2x10 Douglas-Fir joist is side-bearing (shear connection) on a built-up wood

girder

· The design shear load on the side-bearing joint is 400 lb due to floor live and

dead loads

Find 1. The number of 16d box toenails required to transfer the side-bearing (shear)

load.

2. A suitable joist hanger

Solution

1. Determine the number of 16d box toenails required

Z’ = ZCDCdCtn

Z = 103 lb (NDS Table 12.3A)

CD = 1.0 (normal duration load)

Cd = 1.0 (penetration into main member > 12D)

Ctn = 0.83 (NDS·12.3.7)

Z’ = (103 lb)(0.83) = 85 lb

The number of toenails required is determined as follows:

(400 lb)/(85 lb/nail) = 4.7 nails

Use 6 toenails with 3 on each side of the joist to allow for reasonable construction

tolerance in assembling the connection in the field.

2. As an alternative, select a suitable manufactured joist hanger.

Data on metal joist hangers and various other connectors are available from a number

of manufacturers of these products. The design process simply involves the selection of

a properly rated connector of the appropriate size and configuration for the application.

Rated capacities of specialty connectors are generally associated with a particular

fastener and species of framing lumber. Adjustments may be necessary for use with

various lumber species and fastener types.

Conclusion

The example problem details the design approach for two simple methods of

transferring shear loads through a side-bearing connection. One approach uses a

conventional practice of toe-nailing the joist to a wood girder. This approach is

commonly used for short-span floor joists (i.e., tail joist to header joist connections at a

floor stairwell framing). For more heavily loaded applications, a metal joist hanger is

the preferred solution."

The above calculation is for a short-span floor joist to header connection toe-nailed only. No ledger. No hanger. no pressure-blocks offering additional nailing surfaces. The six 16d box nails used in this example are the approved hanger. This example essentially provides a prescriptive manner to ascertain the design shear load on the side-bearing joint at 400 lb due to floor live and

dead loads. I wonder what the shear loads are on the side-bearing joints for a series of fourteen foot ceiling joists spaced 16 O.C. per table R802.4, to obtain the required fastener pattern for joists serving uninhabitable attics with limited storage. (an example).

Again, from the design guide:

"The NDS recognizes in NDS·7.1.1.4 that “extensive experience”

constitutes a reasonable basis for design; therefore, the designer may use Table

7.1 for many, if not all, connections. However, the designer should consider

carefully the footnote to Table 7.1 and verify that the connection complies with

local requirements, practice, and design conditions for residential construction."

There are some posting in this forum that have suggested that we already have the information available (engineering) to prescribe pressure-blocking (nailing patterns) as legitimate framing anchors.

Maybe we just need to do the math . . . a lot of math . . . to determine some prescriptive solutions.

Can anybody steer me in the right direction for determining shear loads required for various common joist loading scenarios?

 

[DRP]

What year NDS are you in?

You looked up an allowable shear for the fastener, multiplied it by a toenail factor (Ctn) and divided the design load by the allowable load per fastener. If the kid at McDonalds can make change he can do this. We've been Simpsonized, nothing wrong with them but that is how effectively they have done their marketing. The AWC needs to do the same kind of marketing, somehow the way they are doing it isn't "clicking" for the majority.

Can anybody steer me in the right direction for determining shear loads required for various common joist loading scenarios?

Uniformly loaded simple span;

V=R

Half the joist's total uniform load is the shear load on each end

For your 14' joist on 16" centers

16" = 1.33'

1.33' x 14' x (40 psf LL + 10 psf DL)=931 lbs load on the joist

Each end is supporting half that load... 465.5 lbs

I'm going to shoot a .131 x 3.25" nail into SPF, so 82lbs x .83= 68.06 lbs/fastener.

465.5/68.06= 6.84 nails... 7 or more properly done toenails.

Pressure block it? check the end grain factor, Ceg. "When dowel type fasteners are inserted into the end grain of the main member, with the fastener axis parallell to the wood fibers, reference lateral design value, Z, shall be multiplied by the end grain factor, Ceg=.67.

Judging from the descriptions this may be the more appropriate number to use. 60 lbs/nail... 7.75... 8 or more nails.

This is a good example of why I asked for staff or a trainer to answer some questions in Denver. This is a perfect training opportunity.

 

[Jobsaver]

DRP. Thanks for the equation.

The HUD study cited was performed in 2000. I'm not sure which year NDS was used, but wouldn't think it would matter. Shear values should remain constant.

It seems plausible to me at this point that some basic prescriptions can be tabulated from the information on hand. I am going to work on it, of course with consideration for all of the information including wood species multipliers, end grain multipliers, etc. It will take a bit of time, but will be worthwhile.

This exercise is proving to be a good training opportunity for me.