1. Barritt Lovelace, PE WSB and Associates May 25 th , 2011 Segmental Bridge Abutment Design Using Solid Finite Elements

2. Lafayette Bridge

Spans the Mississippi River east of Downtown St. Paul

3. Project Description

Two options were designed

• Segmental Concrete

• Steel Box Girder

WSB Teamed with Figg Engineering Group to form the concrete design team

4. Abutments

Resists vertical loads from Superstructure

Resists lateral loads from earth pressure

5. Two Dimensional Analysis

Typical Design Method

• Loads from superstructure are assumed to be equally distributed along abutment

• Pile loads are determined by calculating the neutral axis of the structure

6. Segmental Bridge Loads

Segmental concrete bridges typically have only two to three bearings

7. Three Dimensional Approach

Produces large concentrated loads

Abutments need to be analyzed in three dimensions to determine distribution

8. Finite Element Analysis

Definition

• The finite element method is a numerical technique for finding approximate solutions of partial differential equations as well as of integral equations.

• In the FEM, the structural system is modeled by a set of appropriate finite elements interconnected at points called nodes.

9. Finite Element Analysis 10. Solid Finite Element Analysis 11. Advantages of 3-D Analysis

Improved accuracy

Eliminates variability in pile loads

Reduces pile quantities

Capacity to more accurately place piles

Ability to integrate the wingwall geometry

12. Summary of Results 13. Conclusions

Very effective for shorter abutments

More accurate for all abutment heights

Potential to provide economical designs on all types of bridges and abutments

With better computer hardware these types of designs will be more common

14. Project Team Members

MnDOT

Manjula Louis, Kevin Western, Paul Kivisto

FIGG

Russ Call, Mike Keller, Chris Burgess

WSB

Barritt Lovelace, Sabri Ayaz, Jim Archer,

Dave Vincent, Brad Robinson

15. Questions

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