Impact damage to steel bridge beams

[RDW100]

I am analysing a steel-concrete composite bridge that has been impacted by an oversized load, causing large plastic deformation of the lower flange and web.

Could anyone advise whether this plastic deformation will have altered the material properties of the high yield steel beams? With particular reference to young's modulus and ultimate strength.

Thanks.

 

[cloa]

Young's modulus is fixed for a material.

 

[RDW100]

True (doh!) but is there any other effect to do with material properties that I should be thinking of? I'm am only asking because the client raised the question and we want to make sure we've covered everything.

 

[metengr]

The bulk properties of the beam will remain as per original specification requirements. The concern is for cracks and/or tears that could have been introduced from the impact damage. For the steel portion of the impact damage I would suggest surface nondestructive testing in addition to the visual inspection.

 

[EdStainless]

The local yield strength will be changed, the UTS less so, by plastic deformation.
The ductility of the material may be much less than before.
But those are minor compared to the risk of cracks having started.


= = = = = = = = = = = = = = = = = = = =
Plymouth Tube

 

[stanweld]

In addition to the comments above, loads may be locally concentrated depending on the severity of the geometrical changes incurred.

 

[mrfailure]

Even if cracks did not form from impact, you still may have a concern because the deformation induced static residual stresses which may, in conjunction with cyclic service stress loading, induce fatigue crack formation in the future.

Aaron Tanzer

http://www.lehightesting.com

 

[RDW100]

Does anyone have any quantitative methods for trying to come up with a fatigue life for the bridge? I am using BS 5400-10 and it is mainly about weld details. If there is a detail that can be classed as similar to the damage that has happened then perfect.

 

[metengr]

Residual stress can be removed by local heating of damaged regions in steel girders. This is nothing new and heat straightening is an option.

I would suggest you review DOT information related to bridge assessment methods and damage to bridge structures. Also, post this question in the forum below below;

forum607

 

[Guest102023]

The material properties are not as much a concern as the shape of the flange. The strength of these members lies very much in where the steel is placed, and material in a wide flange gives the maximum resistance to bending. A bridge design engineer, inspectors, and your local inspector/authority need to be involved. Probably you will be lucky and there is enough redundancy and safety factor designed in.

The other concern is cracks; I don't think you have any option but to repair those.