Fatigue Prone Connection Details

[dagunk909]

Hello.

I am in the middle of putting together several reports about fracture critical members and fatigue prone connections on welded truss bridges. All connections in the trusses themselves are welds, but some of the floor systems of them use a mix and match of welds and bolts. We have to identify E and E' welds (welds that are fatigue prone). I have looked at the Detail Categories for Load-Induced Fatigue (AASHTO Table 6.6.1.2.3-1), and I am having trouble with some of the various connections we encountered in the field in determining if they are considered E or E. welds. I have been all over the internet, and have had trouble finding guidance on examples of these welds. Is there any additional guidance out there I haven't found?

Currently, I have any transverse weld on or at the end of a tension member as an E or E' weld. Is any transverse weld on a tension member a fatigue prone connection? I have all of the tension connections on the gusset as fatigue welds. I can only find examples of tack welds and such on bolted gusset plate bridges. Any help would be greatly appreciated.

Thanks.

 

[bridgebuster]

The difference between E & E' is plate thickness. You can have longitudinal E/E' welds.

 

[cvg]

check out AISC manual of steel construction which also has guidance on fatigue

 

[dagunk909]

Thanks for the comments.

Sorry if I was unclear. I have seen several example reports, but at the truss joints, they all had bolted connections. I was wondering if the transverse welds on the tension members in the truss were actually fatigue prone themselves. My interpretation of the fatigue prone details, specifically detail 3.5, was that they were. I have included a drawing showing what welds I am inquiring about. The red lines are the welds at the ends of the tension members. There are welds where the members and gusset plates meet, as well as where the members terminate inside the gusset plate. There are no bolts in any of these connections.

I just haven't seen much guidance on this type of connection.

Thanks.

 

[EQguys]

dagunk909: Essentially all the welds in the drawing are transverse to the direction of the stress. Check Table A-3.1 of AISC Manual of Steel Construction for some guidance.

 

[wiktor]

All these welds transverse to the direction of the stresses are E' category and extremely dangerous. I haven't see any of such welds yet, so may be these are only textbook examples of how not to design the connection.

 

[dagunk909]

All,

Thank you for taking the time to help me out.

wiktor: Believe it or not, we have had about 20 of these things. We've inspected and load rated them. All of the connections are welds. I'm sure there are way more in the state than that, as well.