Bolted Web Splice Joint behavior 1

[AK4S]

I am involved in a discussion regarding the behavior of a Bolted Web Splice Joint and looking for some clarity to understand the true behavior of the connection.
In an existing bridge(several simple spans), one of supports appears to have been constructed incorrectly (shifted by 3ft, whereas all other spans are of the same length). So a Bolted Web Splice Joint is observed in the beams of this span (span1).

Splice detail:

As seen above, there is discontinuity at the top & bottom flanges and the concrete deck above is also discontinuous at this location (expansion joint in deck directly above this splice). Hence it is my understanding that this connection is primarily a shear connection would resist shear and the resultant moment caused by eccentricity of the shear load.
i.e. The span 1 is equivalent of a hung span and the splice connection was never intended to take moment, i.e. the beams were not continuous.

The argument I have received from a colleague is that due to the size of the connection, the rotation of the beams is restricted and hence the behavior will be more like a "partial" moment connection with the system behaving like a 2span continuous beam and the web-splice plate carrying/transferring the bending moment at this location.

I do not agree and feel that flange-splice plates are required to transfer the moment at this connection and a web-splice plate only is not adequate. So I would model the two spans with a "hinge" at the splice location.
Bending moments are primarily transferred through flange splice plates and moment transfer through web portion is not significant. See sketch below:

[ul]
[li]Does the behavior change when you have a connection with so many bolts? Like the bolted connections are locked in with dead load and during live load the beam rotation is prevented thus transferring moment through the web-splice connection?[/li] I can understand this may not be a "pure Hinge" condition, But the moment transfer should not be significant to specifically check the web-splice plate to carry it and if so, what is the expected bending moment? carrying full moment through the connection is not valid. Any thoughts?
[/ul]

 

[AK4S]

@rb1957: Agree to what you are saying if we were still designing the bridge. The current scope of my work is to evaluate the condition of the existing bridge as is. We would be recommending a repair of the deteriorated components and evaluation to provide a catcher's mitt approach or other means to support the end below the splice (any repair evaluation to be performed under a different task/scope). Making the beams continuous by providing flange plates and probably also connecting the deck above this point would change the design approach from the original design and needs a full reevaluation to also confirm that the supports below the continuous span can take the increased load.

 

[rb1957]

but you are designing the repair. It sounded like you were building the bridge, that some beams were incorrectly cut or a support incorrectly placed.

If your repair changes how the beam works, then who knows where that'll end up ? But maybe you bridge people have your own way of knowing that it'll be ok. Not a snipe, we plane people understand the plane's structure (as you bridge people understand your bridges) we we know what corners we can cut when something isn't perfect.

In my mind, the repair should return the strength of the structure. In this case I think that means cap straps. Why not ?

"Hoffen wir mal, dass alles gut geht !"
General Paulus, Nov 1942, outside Stalingrad after the launch of Operation Uranus.

 

[WinelandV]

rb1957,

If it's in good condition, and can handle the required loads, then I don't think there's anything to be gained by forcing a full moment connection. Seeing as it's already in use, I would want a good reason to "repair" it, beyond "I like it behaving this way better."

Bridgesmith will probably have a better opinion of this, though, seeing as this is his day job.

[EDIT: My understanding of this bridge is that it was built 30+ years ago and is due for an evaluation (many states require bridge inspections and beyond depending on age), and this task is what the OP is handling - not designing a fix for a construction screw-up.]

 

[rb1957]

that surprises me (built 30 years ago) and people now looking into a misplaced support. Maybe this is a typical "re-evaluation" ?

I'd like to review the original substantiation, although you need to be really careful ... that you don't just follow the previous logic (very easy to do).

I'd've thought that a "re-evaluation" would be inspecting and confirming the condition of the bridge members (corrosion).

"Hoffen wir mal, dass alles gut geht !"
General Paulus, Nov 1942, outside Stalingrad after the launch of Operation Uranus.

 

[BridgeSmith]

I probably should add some clarification to my last response. The state DOT only has jurisdiction over the bridges the state owns. City and county owned bridges are their responsibility. We inspect them every year (for fracture critical bridges) or every other year (for the rest) and make recommendations for repairs, load postings, closures, etc.

AK4S, based on your calcs above, the moment capacity of the splice would be limited to the 1008 k-in.

Also, be aware that this is likely considered a fracture critical detail, but assuming there are 4 or more girders, it would be considered a redundant superstructure. I'm not sure whether the feds require yearly inspections in that circumstance, or not, but the state DOT should be made aware, if they are not already, of the configuration.

Rod Smith, P.E., The artist formerly known as HotRod10

 

[AK4S]

Thank you all for your review and suggestions.
@BridgeSmith: yes, the state DOT is aware of the configuration and special member inspections at shorter intervals seem to be happening to monitor the deterioration of these splice plates.