topic Re: Transferring results in Structural Bridge Design Forum

Transferring results

Anonymous — Sat, 01 May 2021 13:28:51 GMT

Good day,

I have been trying to design a three-span bridge with two different design beams (one for external beams and one for internal beams) assigned to appropriate parts in the model. I have defined four envelopes, and I have this impression that I can transfer the results to the design beams to properly do readjustments to the beam sections.

My four envelopes are one of each: joint max +ve, joint min -ve, beam max +ve, and beam min -ve

(I also don't know how to use this much so some guidance might be helpful. I simply have different vehicle combinations that I defined the exact same envelope with confusion as to what "joint" and "beam" and "max +ve" and "min -ve" mean. I just want to design for the worst case)

Screenshot 1: The results view can display one envelope at a time. I can see member forces and deflections just fine. Surely I can still design for all four envelopes right, just by transferring to the beam?

(Speaking of which, transferring results will automatically follow tributary areas and other mechanics of load transfer, right?)

Screenshot 2: I need help understanding this part. Virtual members are for transferring results to a beam right? Am I doing it wrong by selecting the entire beam?

Screenshot 3: I do not know what is the proper setting to transfer the envelope.

I would love to hear some input.

Thanks for your time!

Re: Transferring results

dave_geeves — Sun, 02 May 2021 14:47:28 GMT

Hi,

Without seeing your model it is quite difficult for me to guess what your model consists of and what you are trying to achieve, but I will make some assumptions and try to explain the basic process.

My first assumption is that your model is a grillage model and that you have used design beams to provide section properties to the longitudinal beam members. You only have two design beams - which is absolutely fine if the design parameters and design reinforcement is going to be the same for each girder- and you want to obtain envelopes of moment and shears so that they can be transferred to the design beams for design verification. So far so good.

As this is a grillage you will not need to define virtual members as the "Longitudinal Beams" you selected when assigning the design beams to the structure will be used.

As you have used the same design beam for several different longitudinal beams then you will need to define and transfer "Property Set" Envelopes (as opposed to single effect or All Effect) for each of the different design criteria and different limit states. This will be just for beam member results as joint results (displacements and reactions) are not transferrable to the design beams.

For example you will have several envelopes, for the internal beam structure property,

Moment +ve for ULS
Moment -ve for ULS
Moment +ve for SLS
Moment -ve for SLS
Shear for ULS
Shear for SLS

And these will be transferred to the appropriate tables in the design beam

Moment +ve (both ULS and SLS)
Moment -ve (both ULS and SLS)
Shear (both ULS and SLS)

Because the envelopes are "Property Set Envelopes" the transferred results will be the worst results at each location for all the beams with the same property. If you look at the results of the analysis in the results viewer and select a property set envelope it will look as though you are looking at the results for just one beam. If you select one of the values in the table and right mouse click, selecting "Drill down", it will expand the table to provide the makeup of this value and where it came from.

The transfer table just for moments may look something like this:

I don't think I can add a great deal more without seeing your data file but I hope this helps.

If this has answered your query then please mark my reply as a solution so that others may find it more easily. Thanks

Kind regards

Dave Geeves

Re: Transferring results

Anonymous — Sun, 02 May 2021 15:10:29 GMT

Thanks, it's getting clearer. I'm still confused about some things though. Also, I am using AASHTO LRFD 7 and not Eurocodes.

I am confused about the difference between BM 1, 2, and 3. Also, I am having envelopes that are not compatible. I do not know how to interpret this as I simply followed 10.1 and used an influence surface and did load optimization.

Transferring moments and shear:

I do not know how to combine the envelopes properly to properly transfer everything to my beams.

Also, I made a few changes to my design beams. I plan to use different reinforcement details, so I made separate design beams for my different spans.

3D Model:

(each color is a different design beam)

Is it correct to put my influence surface on that longitudinal beam I am designing for, or should I just use one influence surface for all my beams?

I understand that the influence surfaces create different compilations. I can simply delete the previous ones after transferring them to their design beam.

Again, thank you so much. You are helping me a lot.