how to model Horizontally curved concrete bridge? 4

[yjung]

HI ALL !!

i have found many useful information from this site since i got the first job in bridge design. Thanks very much.

I have a project that the bridge is curved a lot. I am trying to model the horizontally curved concrete bridge to obtain the moment and shear.I do not know how to model the curved bridge. I researched about this topic using internet and research papers, but i could not find any usuful design example that i may get some idea how to model this bridge.
I do not want to ask about it to my superviser yet. i would
like to put some effort before asking to my superviser.

Could you please suggest me any good idea how to model this curved bridge or any other information will be appreciated.

yjung

 

[Qshake]

YJUNG, there is nothing wrong with dicussing an approach to a design problem with your supervisor. In fact, most supervisors that I've dealt with and that includes myself like to discuss technical issues with younger engineers to afford them the benefit of experience.

To approach this problem you need to take a look at the AASHTO Guide Specifications for Horizontally Curved Bridges. While much of this material pertains to steel bridges - there is much that can be learned about the approach to curved bridges altogether.

Ultimately, to do this project, you're must have a general structural engineering program available that is capable of modelling such a structure. I would beleive that a grid analysis will be appropriate with the necessary tranverse elements that will allow for the torsional effects due to the curvature. Perhaps after reading the noted references you will have better idea. Presently, with what information you've provided I don't know that a curved analysis is necessary.

Another good source of information on concrete bridges might be those States where concrete bridges are a staple. Check out California and Florida.

 

[zliazmei]

YJUNG,

Try to find AASHTO "Guide Specifications for...."(See Qshake), also Nakai and Yoo "Analysis and design of curved Steel Bridges"- McGraw-Hill

A curved bridge deck can be represented for purpose of analysis by a grillage model composed by curved or straight members.
Note that the transverse memders must be normal to dhe axis of the bridge(be careful with torsional properties for those members).Also, when using straight members, the maximum change in direction at a joint will seldom need to be more than 5deg.This is much smaller than the behaviour of a true curved beam differs significantly from the 'curve' of straight members. In the prototype, moment and tosion interact continuously and smoothly along curved member . In the straight member grilage such interaction only ocurs at joints, so that each type of force is discontinuous. However, the values of forces midway along members are representative of those in the prototype. A smooth distribution can be plotted trough the values at these points, and from it the values elsewere interpolated.

Hope will help.

Regards

 

[yjung]

hi
thanks a lot, Qshake and zliazmel !
(i feel like i am dealing with my supervisor.)

We do not have the AASHTO specification yet.
We gonna order it soon.

Meanwhile, how to calculate the torsion ?
Torsion due to self weight and unbalance of the Live load?
Is that mean, i have another load case for max torsion with loaded only one lane?

Also how to tell you the curvature of the bridge? Is it something like (chord/radius) (same as horizontal curve curvature)?

 

[edward1]

The best and easiest computer program I have used for horizontally curved girders is from MDX. You can get a free evaluation of the program for 30 days from their web site mdxsoftware.com. Good luck

 

[Dinosaur]

I do not think MDX is able to model a concrete bridge.

Will this bridge be built using tangent girders?

Would they be kinked at the piers or would they be spliced using a 'drop in' approach and kinked at the splice points?

Good Luck