1. Seismic Restraint System for Expanded Polystyrene (EPS) Bridge Support Systems
Steven F. Bartlett, Ph.D. P.E
Associate Professor
Department of Civil and Environmental Engineering
October 11, 2016

2. Temporary Bridge Supported on EPS
Lokkeberg Bridge,
Norway

3. Temporary Bridge Supported on EPS
Grimsoyveien
Norway

4. Permanent Bridge Supported on EPS
EPS block
Hjelmungen bru, Norway

5. Wasatch Fault at Little Cottonwood Canyon
Earthquake Hazard
Wasatch Fault
Wasatch Fault at Little Cottonwood Canyon

6. Modes of Excitation / Failure
Internal Stability
Interlayer Sliding
Horizontal Sway and Shear
External Stability
Basal Sliding
Rocking and Uplift

7. Conceptual Vertical Freestanding Support Embankment

8. Conceptual Sloped Trapezoidal Support Embankment

9. Sizing the Potential Span Lengths of the Bridge

10. Sizing the Potential Span Lengths of the Bridge

11. Numerical Model for Freestanding Embankment – Seismic Excitation

12. Modes of Excitation / Failure
Internal Stability
Interlayer Sliding
Horizontal Sway and Shear
External Stability
Basal Sliding
Rocking and Uplift

13. Interlayer Sliding Evaluations

14. Shear Keys to Prevent Sliding
Sliding begins in the numerical model at about 0.5 g horizontal acceleration. Can be arrested up to 1.0 g with shear keys and cabling.

15. Modes of Excitation / Failure
Internal Stability
Interlayer Sliding
Horizontal Sway and Shear
External Stability
Basal Sliding
Rocking and Uplift

16. Basal Sliding
Without embedment of the EPS embankment, basal sliding began at about 0.6 g; however with about 1 to 1.4 m of embedment, basal sliding resistance can be increased to 1 g.

17. Modes of Excitation / Failure
Internal Stability
Interlayer Sliding
Horizontal Sway and Shear
External Stability
Basal Sliding
Rocking and Uplift

18. Determining Allowable Stress in EPS for Internal Seismic Stability Evaluations – Current Guidelines

19. Cyclic Triaxial Testing and Post-Cyclic Creep

20. Test Protocol
Apply vertical stress associated with 1 percent vertical strain and measure pre-cyclic creep strain (represents allowable dead load for design).
Allow creep to occur under dead load (pre-cyclic creep strain).
Cycle specimen to additional stress to higher strain levels (at least 1 percent additional axial strain.
Measure cyclic strains
Re-apply dead load stress (1 percent strain value)
Measure post-cyclic creep strain

21. Pre-Cyclic Creep Strain

22. Pre-Cyclic Creep Strain

23. Example Test Results - Cycling

24. Cyclic Strains

25. Post-Cyclic Creep Strain

26. Post-Cyclic Creep Strain Results

27. Recommended Allowable Stress Levels

28. Acceleration Versus Peak Shear Stress Resulting from Horizontal Sway

29. Compressive Resistance Versus Axial Strain
Shear resistance can be increased by using high density EPS and by cabling system to restrict sway mode.

30. Cabling and Restriction of Sway

31. Modes of Excitation / Failure
Internal Stability
Interlayer Sliding
Horizontal Sway and Shear
External Stability
Basal Sliding
Rocking and Uplift

32. Uplift Evaluations

33. Uplift Evaluations

34. Uplift Evaluations – Peak Stress at Corner

35. Title

36. Questions