Design of Expansion & Fixed Bearing Supports 1

[oengineer]

I am seeking design information (i.e. technical design guides, design example calculations, etc.) for the design of Expansion & Fixed Bearing Supports (see image) based on AREMA criteria.

Suggestions/comments are appreciated.

 

[structuralCADspecialist]

I used to know a lot about this stuff back when I used to work on bridges. I've dug-up some links that helped me way back in the day. Design approaches appear to have changed since the days back when I had my head wrapped around this topic, so I'll refrain from offering design tips. If you dig around the manufacturer's site you might find some design guides. The Elastomeric design guides were pretty easy to follow if I recall but a couple guys kept getting them wrong. Different railways also have their own unique approaches as you'll see with my first link. I also know quite a bit about 'historical' bridge bearings; if that's of value let me know .

https://www.canambridges.com/wp-content/uploads/2015/11/goodco-z-tech-elastomeric-bearings.pdf

https://www.canambridges.com/wp-content/uploads/2015/07/goodco-z-tech-spherical-bearings.pdf

https://www.canambridges.com/publications-2/technical/

 

[oengineer]

What would be the best approach to go about determining the "Location of ribs and diaphragms to reinforce the vertical plates" for the Expansion Bearing supports?

It is mentioned in a check for the expansion bearing design (see image below), but it does not give an example on how to carry out the design.

Also, is it acceptable to use the ACI code to design anchor bolts for expansion bearing supports or does AREMA (or AASHTO) have their own method of anchor bolt design?

 

[BridgeSmith]

Also, is it acceptable to use the ACI code to design anchor bolts for expansion bearing supports or does AREMA (or AASHTO) have their own method of anchor bolt design?

Depends on what you're designing the anchor bolts for - For a building, use ACI; for a highway bridge (carrying auto & truck traffic), use AASHTO; for a railway bridges (carrying rail loads), use AREMA.

I can't help you with the design of the type of bearings you're trying to design; in 19 years of bridge design, I've never designed one. I've done lots of steel reinforced elastomeric bearings, fixed and expansion, including some with PTFE sliding surfaces. I've also designed elastomeric replacements for the bearings like you're showing. Occasionally, we've replaced a few of them in-kind; for those we just had the fabricator replicate the configuration of the existing bearings.

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

 

[oengineer]

Depends on what you're designing the anchor bolts for - For a building, use ACI; for a highway bridge (carrying auto & truck traffic), use AASHTO; for a railway bridges (carrying rail loads), use AREMA.

The anchor bolt design is for the Expansion Bearing support.

Could you let me know where the AREMA code (particular section) discusses the design of anchor bolts?

 

[BridgeSmith]

The anchor bolt design is for the Expansion Bearing support.

Of a bridge carrying what kind of loads?

Could you let me know where the AREMA code (particular section) discusses the design of anchor bolts?

I have no idea where (or if) the AREMA discusses anchor bolts. I design highway bridges, so I only use AASHTO.



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

 

[structuralCADspecialist]

Here's what I recall: The forces on the anchor bolts were obtained using the loads from the AREMA manual (as would the loads and forces for the entire bridge). Track speed will be a big factor in the loads. AREMA might have specified some minimums including minimum bolt diameter, embedment, etc... but I can't recall and it might have changed since I last worked with it. Design of Anchor bolts themselves would be obtained from the relevant steel/concrete manuals per the country or region (AISC/ACI manuals for the U.S.). Furthermore, each Railway might have their own standards on how the anchor bolts are to be designed. This could also be regional as many railways have various 'preferred contractors' in each region and they'd 'prefer' not to test out anything unfamiliar to those contractors. The manuals prescribe 'minimums' but conditions might call for more. For example, many bridge abutments/piers are subject to pretty harsh conditions (extra edge distance is a good idea).

The office I was in was lucky in that the engineers that preceded the team I worked with left some pretty-near-perfect design examples complete with design briefs, all done by hand and easy to learn from.

The type of bearing you are proposing to design is very dated (note the riveted steel construction). The modern version of that would likely be welded and therefore $$$ (casting/machining likely being even more expensive). Sharing a bit more of the nature of your project would help elicit better replies. If you're designing a bridge for a class 1 railway intended to be used with frequent trains at full-speed it would entail a much different design than a bridge for a short-line intended to be used infrequently at at low speeds.

 

[oengineer]

I have no idea where (or if) the AREMA discusses anchor bolts. I design highway bridges, so I only use AASHTO.

Could you please let me know the section of AASHTO that discusses anchor bolt design?

Design of Anchor bolts themselves would be obtained from the relevant steel/concrete manuals per the country or region (AISC/ACI manuals for the U.S.)

This is mainly what I am trying to verify regarding the design of anchor bolts.

AREMA might have specified some minimums including minimum bolt diameter, embedment, etc...

This would be important to know.

 

[oengineer]

I found this article (see image) in regards to anchor bolt design using AASHTO:

Based on this, the ACI 318 provisions for anchor bolt design should be adequate for a bridge based on AASHTO. I believe this is what you were saying, structuralCADspecialist.

 

[oengineer]

The image below shows what I have found regarding anchor bolt design criteria from AREMA:

@structuralCADspecialist - The AREMA code does provide requirements for anchor bolt size and embedment.

I am not seeing any mention of ACI 318 or AISC design requirements in AREMA (so far) regarding anchor bolts.

 

[structuralCADspecialist]

Yep. And forgive my advise for being so vague. It's been 6+ years since I worked with railway bridges and I don't have access to the manuals themselves. You'll likely need the AISC manual as well for the anchor bolt design itself. It might also have recommendations for edge distance, embedment depth, etc... but best to reference both manuals (ACI & AISC). And as mentioned, offices would have their own standards including my example of using extra edge distance.

Edit: I see you posted as I was posting. That page looks familiar and conjures up old memories. Remember that those are minimums. Meaning even if your calculations arrive at an anchor bolt diameter of 1" you'd still need to use 1 1/4" (as your absolute minimum). For the style of expansion bearings in my previous post's link, even more diameter would be required as the bolts stick out quite a ways. So yes, AREMA provides some 'minimums' but you still need to use the AISC manual for your actual sizes (and size-up if you're under that minimum) and use the ACI manual for concrete-related stuff.

Railways will have somewhat different load requirements compared to a highway bridge. For example, AREMA has formulas for things like a flat-spotted wheel jack-hammering your bridge, something you'd (hopefully) not encounter on a public road. AASHTO bearings likely won't be suitable for a Railway Bridge and vice versa. Some railway bridges will actually dislodge if they receive enough lateral force. In fact they even place railway cars on bridges during floods so that they don't wash away. I'm not even sure which would require stronger bearings (but would assume AREMA has heavier loading). Other than universal information I know next to nothing about road/highway bridges.

http://www.okthepk.ca/dataCprSiding/news/2011/2011110903.htm

 

[BridgeSmith]

The article you posted the excerpt from was obviously referring to the concrete confinement of the anchor bolts, rather than the design of the anchor bolts themselves. AASHTO has always had provisions for the design of anchor bolts. It gives general guidance in 14.8.3, which directs the user to 6.13.2.10.2 to determine the tensile resistance, 6.13.2.12 for shear resistance, and 6.13.2.11 for combined tension and shear.

You still haven't told us what loads the bridge is carrying, which will determine what design spec is applicable. You'll only confuse yourself, and probably doing things incorrectly, by looking at design specs that aren't applicable to your design.

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

 

[oengineer]

AASHTO has always had provisions for the design of anchor bolts. It gives general guidance in 14.8.3, which directs the user to 6.13.2.10.2 to determine the tensile resistance, 6.13.2.12 for shear resistance, and 6.13.2.11 for combined tension and shear.

My question is does the AREMA code have sections (similar to what you just mentioned for AASHTO) for the design of anchor bolts? It appears that you just answered the question in regards to ASSHTO. I am asking the same in regards to AREMA.

 

[BridgeSmith]

My question is does the AREMA code have sections (similar to what you just mentioned for AASHTO) for the design of anchor bolts? It appears that you just answered the question in regards to ASSHTO. I am asking the same in regards to AREMA.

Again, what kind of bridge are you designing? If it's a highway bridge, it doesn't matter what AREMA says, and if it's a railway bridge, AASHTO is not applicable.

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

 

[bridgebuster]

oengineer,

ribs and diaphragms resist lateral loads. However, they also help reduce base place thickness. You layout a pattern and use it to come up with plates thickness. I have a drawing I'll post later; I have to get on a call right now. Unfortunately, work sometimes gets in the way of other things.

 

[oengineer]

oengineer,

ribs and diaphragms resist lateral loads. However, they also help reduce base place thickness. You layout a pattern and use it to come up with plates thickness.

Thank you for the comment, bridgebuster!

Do you happen to have available information regarding the design procedure/criteria for anchor bolts using AREMA?

I see no mention of AISC or ACI in the AREMA code in regards to anchor bolt design ( actually I have yet to see much design info in AREMA about anchor bolts other then material properties and the minimum required size & embedment for the anchor ).

 

[oengineer]

@BridgeSmith - The image below is what I am seeking guidance on in regards to the anchor bolt design:

The example in the image is using AREMA specification, so it would be helpful to know the anchor bolt design requirements for AREMA.

 

[BridgeSmith]

So you're designing a bearing and anchorage for a railroad bridge? I don't see any anchor bolts in the example you posted.

If that's the case, I can't help you with any of the specifics of the loads, load combinations and load factors; those would come from the superstructure design. Once you have those, the anchor bolt (steel) design is a fairly straightforward matter of calculating the shear capacity of the anchor bolts, assuming the minimum axial load is enough to prevent uplift on the bolts due to lateral load. If not you'll have combined tension and shear.

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

 

[oengineer]

the anchor bolt (steel) design is a fairly straightforward matter of calculating the shear capacity of the anchor bolts, assuming the minimum axial load is enough to prevent uplift on the bolts due to lateral load.

Do you happen to know what sections of the AREMA code describes the criteria to determine the shear capacity of anchor bolts?

 

[BridgeSmith]

Do you happen to know what sections of the AREMA code describes the criteria to determine the shear capacity of anchor bolts?

As I said, I have no familiarity with AREMA, nor do I have it available to me.

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

 

[bridgebuster]

This is half of a 1983 NYSDOT Standard Sheet for high rockers. maybe a little hard to read but the hard copy isn't much better. If you can't make something out Let me know.