Suspension bridge anchor block analysis 2

[D. Rojas]

Hi everybody, I'm a junior civil engineer from Peru, so please excuse my bad english, hope i can get some help.
I'm actually working on the design of a 130 meters long suspensión bridge (center clear span, unloaded backstays, 2 lanes) and I'm finding a bit difficult to analyze and calculate the Steel reinforcement for the anchor block. The proposed geometry for the anchor block structure is similar to the ones of many suspensión bridges here in Peru (attached image) and I'm short of ideas with the analysis of this structure as a solid body. I've been thinking on determine the Steel reinforcement for the "fixing arm" same as a corbel (shear friction reinforcement) yet I have no clue how to determine the Steel for the rest of the body (outer concrete Surface) and for the highly compressed zones. I've been told that this should be analyzed with the strut and tie method, but i'm already out of time with this Project to think on studying the method.

Any tip or help should be really appreciated. Thanks

 

[rapt]

Talk to your supervising engineer.

 

[BridgeSmith]

If you don't have time to analyze it properly, the only thing I can suggest is look at those similar past projects, scale the reinforcement by the capacity of the suspension cables of those installations compared to yours, and then double the area of reinforcement in each zone.

 

[rapt]

HotRod10,

Worse than that according to his question. He does not know how to do it and he does not have time to learn how to do it properly. So he wants us to give him a shortcut to avoid learning.

That is not how engineering should be practiced.

 

[hokie66]

A 130 metre span is not to be trifled with. Experience is required, and cannot be acquired by trial and error, or by asking questions on the internet.

 

[BridgeSmith]

hokie66 and rapt, I agree with your assessment. My suggestion was somewhat tongue-in-cheek, suggesting that if he does not have the experience to do a proper design, relying on a massively conservative approximation is possibly the only safe way to get around involving someone who does have the expertise. Obviously, the right thing to do is defer to someone who knows how to do the design, and learn how it's done by watching them.

 

[bridgebuster]

When in doubt, check with the master - D.B. Steinman that is. The attached has a sentence about your question. To me the anchor block design analogous to anchor bolt pull out. 30 years ago I was working as a field engineer on the repair of a suspension bridge cable. we had to core through the anchorage in order to bring in the sections of the transfer girder that the cable would get reattached to. It seems back in the day D.B. and his peers didn't bother much with rebar; the eyebars were buried in a lot of concrete.

 

[hokie66]

"A lot of concrete" is the key. Just because some other bridges have used a given anchor block size doesn't make it right.

 

[D. Rojas]

HotRod10. That would actually work but I have to properly sustain that in my report, this is going to be under revision. I've been stuying the construction plans of a previous 150 m bridge, in which the main reinforcement for the anchor zone was calculated as a cantilever beaam but I don't find it as simple as that.

rapt and hokie66. I totally understand that. Don't get me wrong when I say I am short of time, I've been looking for information during the last week all over the internet (books, papers, reports, plans) with no success. It seems that there not much information about this kind of structures, all I've got are basic concepts and past practice schemes. I'm well aware that special care should be given to this design and being conservative. I've attempted to know the structure behavior with some 2D models observing where the stress lines go and where are stressed zones but that is as far as I can get with my short expertise.

bridgebuster. Thanks, I'll take a look that book.