Degree and quality of details 2

[haynewp]

I would like to know what other engineers on this forum think about the extent of detailing a job and it's outcome on structural adequacy and on the project budget.


I have seen a lot of engineers (in my short time) who give a few basic details and leave the rest to the imagination. They believe this to be acceptable and the best way to make money.

I have also seen engineers who detail a job so that every possible situation is shown.

And another case, where every detail is shown, and everything about the details are perfect. From every bolt, nail, etc. to scale, all text has to be lined up perfect, no lines cross dimension strings etc.

I tend to think that major things in a detail should at least be drawn to scale, that gives me a good perspective of how things are going together, and with most situations being shown.

Any opinions?

 

[prex]

Personally I like to issue only drawings conforming to the following description:
-all details needed to fabricate and erect are defined
-the representation is by no means pictorial: a lot of information, including some key dimensions, is found in the bill of materials, bolts and nuts are often represented only by their axes, etc.
-as far as possible the drawing is kept to scale, but this is not crucial
-I try to avoid to the maximum extent possible any repetition of information: e.g. quotes are put only once in a series of drawings for a single project, etc. This makes them a little criptic for a generic reader, but not for the man that must make the pieces, and reliability is improved. prex

http://www.xcalcs.com

Online tools for structural design

 

[LPPE]

I think things should be drawn to scale, and show as much information as possible. The more you show now, the less phone calls you get later. However, I've detailed everything only to inevitably have things changed (I've detailed bolted moment connections to have them changed t full pen welded connections, and then detailed full pen welded connections changed to bolted connections.) Off topic, but it seems that if you detail everything, someone always thinks they have a better way than what you show.

 

[dougantholz]

Good topic.
I am now in the unique position of starting with a start-up consulting engineering firm in the central US. We are in the process of devoloping our standards and details, and have talked at length about how much to show. Here is what we are trying to do:
1. Try to convey as much information as is readable on a set of plans, such that using industry standards a fabricator can make the pieces (geared mostly toward steel construction). We let the steel detailer come up with a lot of things to make it fit together.
2. Show details to scale, for a real situation, and make that detail work as many places as possible. This is to say if we have a W12 spandral condition, we do not redraw for a W24 with a similar framing.
3. Show all members on the plans to the greatest extent possible, only show angles, small tubes other miscellanous steel on the details. The rule of thumb we use is the details should only show members that the contractor should be able to find at the supplier as a stock shape.
4. Don't detail connection specifics, unless paid for them. We are consultants, if the owner wants us to detail the connections we can, but that is typically outside our original contract- it takes extra time so it takes extra money.
5. We generate typical notes to cover misc. steel that the architect usually details. This covers stairs, loose brick lintels, etc.
6. We usually have about 1 page of notes, one of typical details, and one page of details for every page of plans. This usually works, but of course there are exceptions.
Sorry for the long post. Hope this helps.

 

[Kramer]

I have worked on the West Coast (U.S.) and the Midwest and have encountered two very different philosophies. On the West Coast, all elements of the connections are spelled out on the design drawings. The Engineer of Record is responsible for design of all connections. As you go East, the detailing that the EOR performs is typically much less, leaving this to the fabricator. I believe the difference is because when you are designing for seismic events (West Coast philosophy), connections are critical. However, connections are critical for ALL types of loadings. My question is, when most life-threatening structural failures occur due to inadequate connections, how can we as EOR's, not design and take responsibility for the connections?

 

[JedClampett]

I don't think the Engineer of Record is ever "off-the-hook" as far as connection details. Back in the '70's we used to tell the contractor to provide an AISC Table II connection using A325F 7/8" diameter bolts. Whether or not this was a detailed design is a matter of debate. However, we did check all shop drawings to confirm compliance with this.
Now where I work there's not as much steel framing. We do have typical details for connections. Outwardly, this looks like it is better detailed than using a note. But really it is not a big improvement.
My belief is that giving more details improves the design engineer's understanding of the project. Even if they're changed, the contractor is given an expectation for the end product. The amount of detailing is governed by the budget.
When all is said and done, whoever's name is on the bottom of the sheet is going to be blamed for an inadequate design, not the detailer.

 

[dougantholz]

Kramer,
We do take responsibility for the connections, but we must supply forces if the contractor/detailer is to design the connection. If we show a size for plate, weld, etc., we are the ones who should have the calcs available to prove that it works - another rule on our detailing load.

 

[whymrg]

Wery good article "Joint Efforts" on connection design and details in September 2002 "Structural Engineer" magazin.
Try contact them for copy at

http://www.gostructural.com

 

[whyun]

Few things I would consider:

1. Avoid details that create "optical Illusion", i.e. major elements in a detail should be shown to scale. OWJ depth and concrete wall thickness for example.
2. Cover all the differing conditions.
3. Do not have options for a given condition unless absolutely necessary.
4. Incomplete detail is better than wrong detail.
5. Clearly identify where EOR's responsibility "ends" - when indicating elements to be designed by others.
6. Having good set of typical details is extremely helpful since typical details can cover 80% of all conditions. Special details can be generated for unique conditions or conditions where connectors in the typical need to be increased.

Things that really happen:
1. Where inspection is NOT required, you never can predict how contractor will construct the detail.
2. In a retrofit project, details from as-builts will always be different from the site condition. Like a box of chocolates (Forest Gump)
3. Murphy will always be with you.

my few cents plus a few bad jokes...