Superstructure Loads What Precast Pipe and Box Designers

Superstructure Loads What Precast Pipe and Box Designers Need to Know About Mechanically Stabilized Earth (MSE) Walls American Concrete Pipe Association Short Course Orlando Florida Tuesday March 3rd, 2015 WAYNE HODGE, PE 2 Presentation Topics: Basic Understanding of MSE Walls Culvert / MSE Interaction Understanding and Addressing the Complexities of Designing Each System www.concrete-pipe.org 3

BASIC UNDERSTANDING OF MSE WALLS www.concrete-pipe.org 4 What Are MSE Walls? MSE walls are earth retaining structures that are constructed by placing alternating layers of reinforcement and compacted soil behind a facing element to form a composite material which acts integrally to restrain lateral forces. www.concrete-pipe.org 5

MSE Wall Components Facing Panels Reinforced Fill Reinforcement Leveling Pad www.concrete-pipe.org 6 What year was the modern method of soil reinforcement developed?

1895 1921 1957 1982 7 Historical Overview of MSE Walls 1957 - Henri Vidal develops reinforced soil concept. 8 Historical Overview of MSE Walls 1957 - Henri Vidal develops reinforced soil concept. 1963 Vidal first publishes his

research and files the patent for Reinforced Earth 9 Historical Overview of MSE Walls 1971 Vidal brought his technology to the US 1972 First MSE wall constructed in US (California SH 32 near Los Angeles) 1974 First Reinforced Earth structure in US to be used as bridge abutment (I-80 near Lovelock, NV) 10 Historical Overview of MSE Walls 1970s Introduction of competitive wall systems using welded wire grids. 1980s Introduction of geosynthetic reinforced walls.

1990s dramatic increase in the use of geosynthetic reinforced walls with the introduction of segmental retaining walls. 11 Historical Overview of MSE Walls Currently over 60,000 MSE walls higher than 35 ft are in service along the US highway system. Approximately 9 million ft2 are added annually, accounting for more than half of all types of retaining wall usage. 12 Sea-Tac Third Runway www.concrete-pipe.org 13 MSE Wall Applications

14 Advantages of Using MSE Walls Low Cost Ease of Construction Structural Tolerance to Foundation Settlement Performance under seismic loading events Wide range of possible facing types, colors, and textures. 15 Systems / Manufacturers KeySystem I by Keystone Retaining Wall Systems, Inc. Mesa HP System by Tensar Earth Technologies, Inc. Reinforced Earth Classic Panel by The Reinforced Earth Company EarthTrac HA by Earth Tec International, LLC Sanders MSE Wall by Sanders Pre-Cast Concrete Systems Company

Strengthened Soil by Shaw Technologies Sine Wall by Sine Wall, LLC MSE Plus by SSL Construction Products Vist-A-Wall by Vist-A-Wall Systems, LLC Tricon Retained Soil by Tricon Precast 16 Facing Systems Segmental Precast Concrete Panels Dry Cast Modular Block Wall (MBW) Units Welded Wire Mesh (WWM) Gabion Facing Geosynthetic Facing Post-Construction Facing 17 Reinforcement Types Materials Metallic

Geosynthetics Configurations Strips Straps Grids Mesh 18 Failure Modes of MSE Walls External Stability Internal Stability Compound Stability 19 External Stability

Sliding Bearing Capacity Eccentricity Overall Stability 20 Internal Stability Reinforcement Rupture Reinforcement Interaction with Reinforced Fill Connection Strength 21 Compound Stability

Modes initiated outside the reinforced zone and exit through the reinforcement and facing. 22 Construction Sequence of MSE Walls with Precast Panel Facings Preparation of subgrade. Placement of a leveling pad for the erection of the facing elements. Erection of the first row of facing panels on the prepared leveling pad. Placement and compaction of reinforced wall fill on the subgrade to the level of the first layer of reinforcement and its compaction. Placement of the first layer of reinforcing elements on the wall fill. Placement of the wall fill over the reinforcing elements to the level of the next reinforcement layer and compaction of the wall fill. Construction of traffic barriers and

copings. 23 CULVERT / MSE WALL INTERACTION www.concrete-pipe.org 24 Questions Loads Factored or Unfactored Load Type Dead Load or Live Load (Traffic Surcharge) Influence Zone of Load Load Distribution Through Soil Back-to-Back Walls Culvert Placement and Orientation 25 Comparison of MSE Wall Project Data

MSE WALL DATA MSE Project Wall Mfgr A B B B C C C C C C C C C D D E E E 1 2

2 2 3 3 3 3 3 3 3 3 3 4 4 4 4 4 H (ft) L (ft) L/H

Wall A1-1 B2-1 B2-2 B2-3 C3-1 C3-2 C3-3 C3-4 C3-5 C3-6 C3-7 C3-8 C3-9 D4-1 D4-2 E4-1 E4-2 E4-3 34.1 8.0 33.8

32.3 42.0 36.0 46.5 43.3 17.7 12.4 33.0 20.1 22.0 20.0 20.0 10.5 18.5 14.0 26.0 8.0 24.0 23.0 29.4 25.2 32.6 30.3

12.4 8.7 23.1 14.1 15.4 14.0 14.0 7.4 13.0 9.8 0.76 1.00 0.71 0.71 0.70 0.70 0.70 0.70 0.70 0.70 0.70 0.70 0.70

0.70 0.70 0.70 0.70 0.70 BP (psf) 6,210 1,560 5,690 5,500 7,148 6,213 9,220 8,633 3,380 2,578 5,523 3,749 3,868 4,052 5,267 3,160

3,530 2,580 BP ult (psf) FS 2,280 8,140 7,870 1.46 1.43 1.43 5,470 7,114 4,260 4,760 4,264 1.35 1.35

1.35 1.35 1.65 General "Rule of Thumb" has been to assume this value is 0.7. This appears to be a fairly safe assumption. ge Soil Load w/o MSE Wall h * EV Fe we (pcf) (psf) 120 120 120 120 120

120 120 120 120 120 120 120 120 120 120 120 120 120 1.15 1.15 1.15 1.15 1.15 1.15 1.15 1.15 1.15 1.15

1.15 1.15 1.15 1.15 1.15 1.15 1.15 1.15 4,712 1,110 4,660 4,451 5,796 4,968 6,417 5,975 2,443 1,711 4,554 2,774 3,036 2,760 2,760

1,449 2,553 1,932 1.37 1.37 1.37 1.37 1.37 1.37 1.37 1.37 1.37 1.37 1.37 1.37 1.37 1.37 1.37 1.37 1.37 1.37 w eu

(psf) BP / w e BP ult / w eu Max BP/w e 6,432 1,514 6,361 6,075 7,912 6,781 8,759 8,156 3,334 2,336 6,216 3,786 4,144 3,767 3,767 1,978 3,485 2,637 1.32

1.41 1.22 1.24 1.23 1.25 1.44 1.44 1.38 1.51 1.21 1.35 1.27 1.47 1.91 2.18 1.38 1.34 1.51 1.28 1.30 1.45 1.89

2.15 1.37 1.62 General "Rule of Thumb" has been to assume this value is 1.35. It appears that this assumption is often unconservative. Actual values appear to vary a fair amount (1.21 to 2.18). This amount of variance can have a significant effect on the RCB or RCP design. Notes: * All green shaded cells are input cells and the information listed was obtained from the MSE wall manufacturer. H - Height of MSE wall L - Length of soil reinforcement ties. BP - Unfactored applied bearing pressure measured at the base of the wall. BP ult - Factored applied bearing pressure measured at the base of the wall. FS - Factor of safety for applied bearing pressure (BP ult / BP) ge - Assumed unit weight of backfill soil used in standard RCB designs. F e - Soil-structure interaction factor used in standard RCB designs. w e - Unfactored vertical earth pressure acting on top of RCB when top of top slab is located at a depth, H , below finished grade. h - Load modifier for non-redundant structures under earth fill (equal to 1.05 per AASHTO LRFD and ASTM C1577) EV - Vertical earth pressure load factor used in RCB designs (equal to 1.3 in AASHTO LRFD and ASTM C1577) w eu - Factored vertical earth pressure acting on top of RCB when top of top slab is located at a depth, H , below finished grade. 1.32

1.51 1.28 1.30 1.23 1.25 1.44 1.44 1.38 1.51 1.21 1.35 1.27 1.47 1.91 2.18 1.38 1.62 26 UNDERSTANDING AND ADDRESSING THE COMPLEXITIES WHEN DESIGNING EACH

SYSTEM www.concrete-pipe.org 27 Involvement of Multiple Entities Owner / Agency Project Civil / Structural Design Engineer Geotechnical Engineer MSE Wall Design Engineer MSE Wall Supplier MSE Wall Installer QA Testing Firm Precast Pipe/Box Supplier

28 Division of Responsibility External Stability Owner / Geotech Consultant Global stability of structure Bearing capacity analysis Settlement analysis Internal Stability MSE Wall System Supplier / Designer Pullout and rupture of reinforcements Design of all wall system components Check sliding and overturning Determine eccentricity of structure and applied bearing pressure at base of structure 29

Design Methods Coherent Gravity Method Tieback Wedge Design Method AASHTO Simplified Method FHWA Structure Stiffness Method K-Stiffness Method Ehrlich and Mitchell Model 30 MSE Wall Specifications ASD / LRFD US / Metric Units FHWA Standard Specifications for Reinforced Earth (MSE Walls) AASHTO Standard Specification for

Highway Bridge AASHTO LRFD Bridge Design Specification State DOT Specifications 31 QUESTIONS AND COMMENTS www.concrete-pipe.org

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