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Graeme · Guest

I have some retaining walls to draw on a bridge project. The road is curved
and I have the vert profile drawings and topographical plan from the civils.
I haven't really done bridges before so I'm wondering how I should draw the
walls in elevation.
Should I;
a. draw an elevation straight on. (wouldn't seem to be of much use
structurally.)
b. use the civils profiles and draw the wall elevations based on the wall
location perpendicular to the centreline. (eg. inside wall and outside wall
on a curved road 100 feet long on centre would both be drawn 100 foot long)
c. develop the wall elevations correctly ( eg. inside wall on a curved
road 100 feet long on centre would be drawn shorter and outside wall would
be drawn longer).
d. none of the above.

Some more info, we are partially following DOT Colorado but, it's not on a
public road, so I'm glad to say I dont have to sit and leaf through 150
pages of drafting standards while doing this.

Any help will be appreciated

Graeme

teiarch · Guest

Graeme:

The question that should be asked is: "What needs to be shown?"

If the extent of these retaining walls is not clearly defined by (as you call them) the "civils", then standard orthographic projections (or 3D model) would be in order. Full elevation of the exposed side, plan and one side view would probably be approriate.

Your task would most likely be to show the walls and their relationship to the road and finished grades plus any accessories such as guard rails, drainage curbs and other related details.

Part of this exercise involves graphically verifying that the civil information already developed is accurate and complete. Sometimes elevation studies will reveal details and information that has not been completely developed.

Good Luck!

TRJ · Guest

I concur wholeheartedly!

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Graeme · Guest

Thanks for replying. We have basically been asked to prepare retaining wall
elevations for pricing. They are pretty much purely dimensional. Rebar will
be shown in section and in a table based on retained height. So all they
show is the steps in the footings, there is a ledge just below grade for
stone facing, which we have to show too.

I was hoping that there was a standard practice for this.

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teiarch · Guest

Graeme: This looks like a clear case for modeling in 3D. Since you will not be required to show reinforcing details, 3D solids (if curved) or 3dfaces/regions (if straight or segmented) would be appropriate if you or someone in your firm is at ease with working in 3D.

Plop the 3D objects in model space, throw on some dimensions, set up some views in paperspace and you're off to the races! Might have to put the dimensions on separate layers for each plane they reside in so you can control their visibility in each view but that's not a big hassle if you think about it ahead of time.

I always encourage people to try to break away from the traditional thinking of drawing orthographic views in 2D because the full version of AutoCad is capable of 3D (yeah, I know it's limited so please, 3D experts, refrain from suggesting that he buy $15K worth of modeling software).

OLD-CADaver · Guest

AFAIK, there is no "standard" pricing for this kind of work, it's usually based on volume of material, excavation, backfill, concrete, etc. The local library may have a "Means Catalog" for estimating manhours for construction.

As "teiarch" pointed out, this is an excellent opportunity to stretch out your 3D muscle. If you use 3DSOLIDS for the entire construction, MASSPROP will extract the volume for you, which may be useful for pricing. Annotating in PS will alleviate the multiple dim layers he spoke of.

Graeme · Guest

Thanks teiarch, but I'm not looking for the method of how to draw it, I was
hoping that someone had experience with DOT standards for bridges and how to
present the wall elevations.

No matter how much I love using 3D to draw, I'm not high enough up the food
chain here to make that kind of decision and to be honest I have no idea how
to create a developed elevation of a 3d surface in AutoCAD. I did, however,
draw the bridge deck in 3d as a dxf for the engineer to import into his
design program.

And yeah, I agree with you that with a bit of experimenting, there are not
many 3d shapes that cant be created in plain ole AutoCAD.

Graeme

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Graeme · Guest

I'm not doing the pricing, someone else is doing it. The job is in Colorado
and I'm in Vancouver. I've been using CDOT manual for bridges but all their
typical project details are of straight walls parallel to the road
centreline.

I get to stretch my 3d muscle all the time.... at lunch time that is.
Structural engineering is still very much stuck in the 2d world. The big
question is always "how am I supposed to draw rebar in 3D?", since it's
drawn very diagrammatically. Steelwork is easy, works like a charm. It's
still gonna be a while before the powers that be are convinced.
I think the learning curve freaks people out too. Hell, most people here
have grips and noun/verb selection turned off because they dont like new
things, we're using AutoCAD 2004, have some pretty nice computers, dual
monitors, and most people are still using AutoCAD as if they were using
Release 9, need I say more ?

Graeme

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jim_johnson · Guest

Graeme
i'd say the answer is a combination of c and d..
i've been drawing and designing bridges for 25 years and the way i've always drawn them is to draw the outside face of the wall in a developed view. in other words, draw it as if it's a flat wall with the dimensions of the curved wall. if it's 100 feet along the project centerline, it's going to be slightly shorter on the inside of the curve and slightly longer on the outside of the curve. forget about the inside face of the wall, the end faces will probably be radial, so placement of the bars will not be affected by it.
keep in mind too that the profile is the place to start when it comes to figuring out the height of the wall, but there are more factors to consider, the reduction in/addition to the height due to the superelevation of the roadway, the slope of the shoulder of the road and how far out from the edge of the road the wall is. all these factors combine to get the top of wall height.
and as someone said earlier, i'd check the plan and profiles i got from 'the civils' to be sure it was correct. i've had my share of bad information from people who are supposed to know what's going on to check everything i get from someone else.

..........................Jim

Graeme · Guest

Thank you Jim

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teiarch · Guest

Jim J.: All well and good to use the traditional old 2D philosophy but you're description of how the 2D elevations need to be constructed make a good case for modeling it in 3D. If you get the corners and the curves correctly, the rest will pretty much take care of itself.

Let the software do the work; it'll be more accurate
Graeme: I hear you! I guess I could understand civil types being a little reluctant about "letting" you produce this is 3D but I run into the same thing with architects who allegedly pride themselves for being able to conceptualize in 3D.

Conceptualize? Maybe yes; produce it in 3D? Oh, my....well, we don't do that....

Fear of the unknown.....

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