Bridge Pier/Bent Design - temperature/shrinkage internal forces

[bridgeman8]

When designing rigid frame bridge bents, is it appropriate to account for substructure member length changes (bent cap) due to temperature and shrinkage? RCPier allows you to input strain loads to model temperature and shrinkage effects of the bent. When the bent cap gets shorter in length due to shrinkage and temperature drop, a significant force may be produced in the columns. I am curious how others approach this. I see three options:

1. Neglect temperature and shrinkage internal forces.

2. Include a strain load for the temperature and shrinkage forces in RCPier, and use Igross for the column (elastic analysis). This should be very conservative, but large uplift forces my be developed for the piles/spread footings of the exterior column footings.

3. Include a strain load for the temperature and shrinkage forces in RCPier, and use Icracked for the column (non-linear analysis). In RCPier, a "factor of reduced moment of inertia" can be applied to the columns. This is used to model the cracking effect. This factor will be multiplied by the moment of inertia of the original section. This method should greatly reduce the forces transmitted to the exterior column footings.

Which option do you use when designing multi-column piers? Can I simply neglect the internal stresses due to temperature change and shrinkage forces for rigid frame bents? AASHTO LRFD 3.4.1 discusses this issue briefly, but our state DOT does not provide any guidance.

 

[bridgebuster]

I've never used RCPier. On rigid frame pier bents I've always considered temperature and shrinkage in the design of the the columns and cap beam. They're included in the group loadings.

Before RCPier, I thought 50, 60, whatever pages to design and pier by hand was a lot. I remember when we got the program someone said the output for a four column bent was over 800 pages.

 

[asixth]

I use to do it an a general purpose FE package. I would convert the temperature changes, shrinkage and creep to an equivalent temperature forces. Run the analysis and design accordingly.