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# How to model a bridge in DYNAMO and calculate it with SAP2000 as frame element?

## How to model a bridge in DYNAMO and calculate it with SAP2000 as frame element?

(OP)
Good afternoon,

I would like to present an idea that has come up with the development of my Master Thesis for what you would offer me your point of view. First, tell you that I do not know if I should have framed the doubt in this forum, excuse me if it is not, and I would appreciate if the post was moved in case it was deemed convenient.

I am designing a two-spaced prestressed concrete bridge, with a slab type section, with the traditional method, that in this case is:

1. Design of the main sections in AutoCad.

2. Obtaining mechanical characteristics.

3. For geometric reasons, height / length ratio, it is decided to make a beam type model in SAP2000.

4. Obtaining efforts to which the structure is subject.

Well, I throw the doubt that has arisen: would it be possible to model in Dynamo, the bridge in question, and then load it into the SAP2000 program, as a frame element?

PD: Attached capture of the simple SAP2000 beam model, of variable section, in case it helps to better understand the problem.
Replies continue below

### RE: How to model a bridge in DYNAMO and calculate it with SAP2000 as frame element?

You mean like this?

You can also just build the model from scratch in SAP2000. If it's just line elements, then it should be real easy. Sounds like you are talking about running a grillage model. They are quick, simple, and dirty, but work fine for straight non-skewed bridges. One step up from that would be to model the girder with line elements and the deck using shell elements. Makes post-processing more tedious, though.

I sometimes like to import .dwg files into my FEA program if the layout is complicated or if I want to manually mesh the shell elements outside of the FEA program. From my memory of using SAP2000 in school, it is not very "wizard driven" which is good, because it is more of a general FEA program that can be used to model general structures. Unlike, say something like CSI Bridge.

Looking at your attachment, I can't tell if that line element represents the whole superstructure or just one girder line.

What is it that you are trying to get out of SAP2000? Are you modeling the Strength level loads, running a moving load analysis (which I'm not sure if SAP can do), running an extreme level dynamic analysis? For the superstructure design, unless it's highly skewed, or curved, or has some unique staged post-tensioning, you can design it by hand. For the substructure, yes, modeling it in SAP with soil-structure interaction and running a dynamic analysis to obtain force demands would be typical and prudent.

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