Strand 7 help Modelling a vehicle impact with a bridge
Strand 7 help Modelling a vehicle impact with a bridge
(OP)
Hi guys,
My current project involves modelling an excavator arm impacting a series of cross-beams on a steel bridge.
I have little to no experience in Strand 7 and am looking for a few pointers on how to go about the model! If anyone has some tips to direct me along that would be fantastic.
So far I have modelled a single I-beam, and am currently trying to determine how to model the impact of the vehicle colliding through the lower 3rd of the beam.
The I-beam was modelled using beam elements to represent the cross-section, then extruded as plates and fixed at each end.
Should I be using contact elements and a load factor table to represent the impact over a short time? I am looking to find the permanent dispacement and nodal reactions caused by the colliding vehicle, and then translate those through the rest of the bridge structure.
Cheers,
Cam
My current project involves modelling an excavator arm impacting a series of cross-beams on a steel bridge.
I have little to no experience in Strand 7 and am looking for a few pointers on how to go about the model! If anyone has some tips to direct me along that would be fantastic.
So far I have modelled a single I-beam, and am currently trying to determine how to model the impact of the vehicle colliding through the lower 3rd of the beam.
The I-beam was modelled using beam elements to represent the cross-section, then extruded as plates and fixed at each end.
Should I be using contact elements and a load factor table to represent the impact over a short time? I am looking to find the permanent dispacement and nodal reactions caused by the colliding vehicle, and then translate those through the rest of the bridge structure.
Cheers,
Cam





RE: Strand 7 help Modelling a vehicle impact with a bridge
To do a detailed impact analysis as you descrbe is a major undertaking, even for someone familiar with dynamic FEA, which I'm guessing you are not.
Practical options are:
- Apply an equivalent static load specified in a design code or from research on impacts under similar conditions.
- Do a "pushover" type analysis, looking at the deflection required to absorb the energy of the load.
This really isn't a software related question. I think you need to do some research on the specific impact type and decide on a design and analysis approach, then look at how it might be implemented in a specific software package.Doug Jenkins
Interactive Design Services
http://newtonexcelbach.wordpress.com/
RE: Strand 7 help Modelling a vehicle impact with a bridge
Correct you are, I'm not familiar with FEA.
I have about 4 weeks to finalise my model. Thanks for the suggestions above, I did a bit of research into both and it will probably suit me to run with option 1).
I will use the equivalent static load, as I have a report from the incident detailing equivalent loads determined by an external commission.
I think my workflow here is to apply the load over an area, with a time vs load factor graph, in the nonlinear transient dynamic load, using an appropriate number of time steps?
What is a simple method to spread the impacting load over an area of say, 50cm on the lower flange and lower section of the web? Create a contact element from beams, or create some springs that apply the load in compression over that area?
Sorry for the complete lack of understanding on my behalf. I appreciate your time and knowledge on this one!
Cheers,
Cam
RE: Strand 7 help Modelling a vehicle impact with a bridge
Sorry about that, but there is more to FEA than producing pretty plots for managers to look at.
Cheers
Greg Locock
New here? Try reading these, they might help FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm?
RE: Strand 7 help Modelling a vehicle impact with a bridge
Doug Jenkins
Interactive Design Services
http://newtonexcelbach.wordpress.com/
RE: Strand 7 help Modelling a vehicle impact with a bridge
If your willing to help that would be great! However I understand that there are real world problems that deserve more attention..
cheers!
RE: Strand 7 help Modelling a vehicle impact with a bridge
One approach that might work with Strand7 is to use it to ascertain the force vs deflection curve up to full plasticity at the point of impact. You can then use a spreadsheet to model the behaviour of a rigid mass as it strikes this non linear spring.
That is more or less how we used to do crash before non linear FEA was available and accurate, that is build a series of non linear springs and then cascade them.
Cheers
Greg Locock
New here? Try reading these, they might help FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm?