I-71/I-670 InterchangeBest Value Design-Build Method

REConews

Location: Columbus, OH

Travelers going east or west through Columbus, Ohio, have three route options: south of downtown along I-70, through downtown on I-670, or bypass the city using circumferential I-270. All three routes are intersected at different points by I-71, which runs north-south across the city and straight through the heart of Columbus. The downtown maze where I-70, I-71 and I-670 intersect has long been characterized by high traffic volumes, geometric deficiencies, closely spaced ramps requiring intricate weaving patterns, and a high percentage of both commercial vehicles and large, limited-maneuverability trucks. By the end of

the 1990s the heart of the problem, the I-71/I-670 interchange, had the highest crash rate in Ohio and was in critical need of reconstruction and widening to improve safety and traffic flow. In 2001 the Ohio DOT (ODOT) began studying ways to improve the downtown interstate network in general and this interchange in particular.

A law passed in 2010 authorized ODOT to use the best value design-build method (contractor selection based on technical qualifications, project schedule and cost), allowing interchange reconstruction to begin two and a half years earlier than planned and saving $40 million compared to traditional project delivery methods.

In this Issue

Cover Story:

I-71/I-670 Interchange ............................. .1

SR 154 Bangerter Highway ..................... 4

Upcoming Events ........................................ 5

Jimmy DeLoach Parkway ........................ 6

Noteworthy Projects ................................. 8

Summer 2015

Double-T panels constructed in front of temporary shoring.

REINFORCED EARTH®

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Continues on page 2...

The project comprised of one mile of I-71, one and a half miles of I-670 eastbound, 18 ramps, 18 new bridges, 2 new flyover bridges, 2 reconstructed bridges, 26 retaining walls, and 2 new local urban avenues. Planners took a comprehensive approach to improve traffic operations, restore safe travel, and support the social and economic vitality of the area.

An advisory committee was created and public involvement was maintained throughout the project using venues such as community meetings, surveys, newsletters and a project website. This community outreach clearly identified protecting the Shiloh Baptist Church as a very high priority. Completed in 1923 and designated an historic site, the church plays a central role in the Columbus community. The interchange widening would place the new two-lane ramp from I-71 north to I-670 east and west much closer to the church, eliminating the existing slope down to the highway. The only way to adequately protect the church, along with several nearby residential and child care structures, was with a retaining wall constructed in the narrow space between those structures and the road. Beginning at the portal of a short tunnel and running north along the ramp, much of the wall would rise 25-29 ft. above top of footing.

Design and construction of this retaining wall was the responsibility of the design-build general contractor, Kokosing Construction Company Inc., teamed with design consultant CH2M Hill and CH2M’s foundation/geotechnical subconsultant,

E. L. Robinson Engineering. The first plan was a traditional ODOT-design cast-in-place cantilevered wall – on a spread footing thanks to the excellent bearing available on the granular material at this location – but Kokosing wanted a faster, easier and lower-cost way to build the wall. Based on prior positive experiences building Reinforced Earth® mechanically stabilized earth (MSE) walls supplied by The Reinforced Earth Company (RECo), the contractor turned to RECo for assistance. The problem with an MSE approach, however, was the extremely narrow space behind the wall face and the 2:1 slope rising 5-10 ft. from the top of the wall. In an MSE design, the soil reinforcements behind the wall are about 70% as long as the loaded height of the wall. Therefore, including the effect of the 2:1 slope, many of these reinforcements needed to be 23 ft., far longer than the 13 ft. available in front of the excavated and temporarily supported backslope.

Next Kokosing considered a back-to-back Reinforced Earth wall, often used for ramps that must be retained on both sides, but the space was too narrow to develop adequate sliding resistance and global stability given the forces exerted by the high backslope. So when RECo suggested an alternative concept that could satisfy most

structural requirements, meet the geometric constraints of the site, and also speed up construction, the contractor was interested. In general, the proposal was to construct a precast post-tensioned double- or triple-tee retaining wall, using a modification of the original ODOT-design cast-in-place footing. RECo had a form available for casting the very tall panels required for the project and on-staff designers with previous experience with post-tensioning design and the details of this wall system.

Panels were cast of 5000 psi concrete and ranged from 6.5 ft. to 29.75 ft. tall. P-T bars were precisely positioned and cast into the footing by Kokosing, allowing a perfect fit when the panels were set down over the bars. Panels rested on structural shims, allowing precise levelling; the space under

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Figure 1. Double-T precast panels showing holes for single and double post-tensioning bars.

Figure 2. Panel bears on structural shims, non-shrink grout packed under panelsprior to stressing P-T bars.

the panels was then dry-packed with non-shrink grout (Figure 2) prior to P-T bar stressing (Figure 3).

Slope stability during construction required excavation support behind taller portions of the retaining wall. The contractor’s choice was a soldier pile and lagging wall that would be left in place. The geotechnical engineer took advantage of this configuration to offset the limited space for the heel of the wall (maximum 12.5 ft.). A HP 10x42 steel pile was welded to the face of each soldier pile and embedded in the footing concrete of the permanent wall, acting as a “deadman” to anchor the wall in place.

Panel fabrication was performed by Norwalk Concrete Industries and used a series of form liners to produce a varying but repeating pattern. Norwalk set up the complete form, including the T forms.

With only one form and 125 panels, this process occurred once per day and required more than 6 months to complete. Setting up the form liner was a major task, so the precaster had to cast all panels using a particular liner before moving on to the next liner type. The only exception occurred at the tunnel end of the wall, where the first 20 panels – 200 ft. of wall – had to be erected on a fast-track schedule, during the winter, to protect and allow access to the child care center and residences directly above. Winter and spring weather was generally terrible, pushing the balance of wall erection to the late spring and summer months.

Design-build projects inspire creativity by all parties, and the I-71/I-670 Interchange was no exception. Where an MSE wall would not work, The Reinforced Earth Company customized and supplied a different precast wall system. Where

typical foundation design would not work, a temporary wall was repurposed as a deadman. ODOT evaluated and approved new ways to solve problems and Kokosing Construction made it all happen. And the community benefitted through sensitive design and better and safer traffic flow along I-71 and I-670 in downtown Columbus.

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Figure 3. Initial tightening followed by instrumented torquing to required load.

Location: Riverton, UT

Along the southern boundary of Riverton, UT, on the southern edge of the Salt Lake City metropolitan area, two major commuter routes intersected at grade in the middle of a rapidly-growing bedroom community and its supporting commercial development. The resulting traffic nightmares on both east/west Bangerter Highway (SR 154) and north/south South Redwood Road (SR 68) necessitated replacing this signalized intersection with a grade-separated interchange. Utah DOT (UDOT) required a single point urban interchange, with seismic design requirements of 0.66g for walls within 50 ft. of the abutments and 0.43g for walls elsewhere, and suggested a 250 ft. long bridge taking Bangerter over Redwood. The project, advertised in early 2014 as design-bid, was to be awarded based on price + time scoring and specifically required maintaining all existing traffic lanes and movements.

The winning bidder, Wadsworth Brothers Construction (teamed with Wilson & Company, engineers, and Fehr & Peers,

transportation consultants), proposed a 350 ft. long, 3-span continuous bridge due to its relatively shallower depth, resulting in shorter abutments and lower approach fill embankments on this settlement-prone site. To fit the interchange into the neighborhood required retaining walls; Wadsworth Brothers selected Reinforced Earth® mechanically stabilized earth (MSE) retaining walls from The Reinforced Earth Company (RECo). Why Reinforced Earth walls? Because they offer low and even bearing pressure, rapid and simple construction, a variety of architectural options and, of course, an economical price. But the clincher was RECo’s high level of service, including the ability to deliver the first wall in just 8 weeks.

The settlement-prone foundation soils significantly influenced geotechnical design of this project. Although the lower-height abutments and approach fills somewhat reduced the expected foundation loading Gerhart Cole Inc., geotechnical engineers, wanted to assure long-term embankment stability by

forcing additional settlement to occur during the construction process. But a typical way to force settlement, by preloading with or without wick drains, was not possible because there was neither space for the necessary preload embankments nor time to wait for the settlement to occur. So instead of using extra weight to produce more settlement, the designers opted to use lightweight fill to produce less settlement. The lightweight cellular concrete product Cell-Crete, with its ±32 pcf unit weight (only 25-30% the weight of ordinary fill) was selected for the lower portion of the embankments, but these embankments were also the backfill of the Reinforced Earth structures. Therefore, it was left to RECo to design their walls using enough Cell-Crete to achieve the required load reduction, then switch to soil backfill for the upper portions of the walls.

Sufficient weight reduction could be achieved by using cellular concrete from the bottom of the required undercut (which varied in thickness) up to just below the tops of the traffic barriers that would be constructed in front of the walls. By using its Terratrel® (TRL) wire faced wall system (instead of precast panels) behind the barriers, RECo reduced the overall facing cost and gave the contractor a little flexibility in locating the multiple layers of reinforcing strips which would run through the cellular concrete (which was the backfill for the TRL walls). The leveling pad for the precast panel facing would then sit atop the Cell-Crete and only the panel portion of the wall would be visible above the traffic barrier. As expressed by Susan Rafalko, P.E., RECo’s Western Division Engineering Manager, “The design for the bottom of the wall was challenging because each wall’s foundation elevation had numerous steps, the thickness of cellular concrete necessary for reduced bearing pressure varied with the height of each wall, and we had to be sure the TRL facing was not exposed. We also had to keep in mind that the cold joints in the cellular concrete could not coincide with

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Figure 1. Reinforcing strips connect to TerraTrel wire mesh facing (background), supported by staked crossbars, prior to cellular concrete placement.

SR 154 Bangerter HighwaySalt Lake City Interchange Improvements

the reinforcing strip levels. This was not easy given all the foundation steps and the frequently changing elevations of the strip levels along the bottom of the wall.”

The process of constructing the cellular concrete portion of the walls had its own challenges. The several layers of reinforcing strips – that would be embedded in the Cell-Crete at different elevations along the length of the walls – had to be connected and held in position in thin air while Cell-Crete was placed and cured. To position these strips, the contractor drove vertical rebar stakes approximately 4 ft. apart parallel to the strips’ alignment (Fig. 1). Horizontal crossbars, parallel to the wall face, were tied to the vertical stakes to support the strips in an essentially horizontal position, as if they were lying on the surface of compacted backfill. Lift thickness of the Cell-Crete mixture varied, but every layer of reinforcing strips had to have a minimum of 6 in. of Cell-Crete both above and below, to avoid strips being in or near a cellular concrete cold joint. Normal reinforcing strip lengths of 70% of structure height were used throughout the project, except within 50 ft. of the abutments where the UDOT-specified increased seismic acceleration required a 0.75H strip length to provide increased pullout resistance.

Two walls along the north side of the project were required early in the job as part of the maintenance of traffic plan. Originally conceived by the contractor as two-stage walls (first build a flexible, wire-faced MSE wall, allow it to settle, then add a permanent concrete facing), RECo’s ability to use the cellular concrete and build these walls in one continuous process promised to save both time and money. But it was RECo’s ability to design and deliver wall materials in only 8 weeks that clinched the deal, allowing Wadsworth to get farther into the project sooner and have more work completed prior to the inevitable slowdowns of winter in Salt Lake City. And drivers benefitted by having traffic continue to flow in the direction to which they were accustomed, without confusing detours and out-of-direction travel.

Upcoming EventsMobility 21 August 28, 2015 Anaheim, CA

Western Bridge SeminarSeptember 9-11, 2015Reno, NV

Railway InterchangeOctober 4-6, 2015 Minneapolis, MN

STGECOctober 19-23, 2015Greenville, SC

Accelerated Bridge ConferenceDecember 7-8, 2015Miami, FL

Transportation Research BoardJanuary 11-13, 2016Washington, DC

Figure 2. Granite Templar architectural finish on 5 ft. x 10 ft. precast facing

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Jimmy DeLoach Parkway Eases Flow of Panama Canal Freight: Relieves Truck Congestion

Figure 1.. Square piles behind Reinforced Earth mixed abutment MSE wall.

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Location: Savannah, GA

Did you know that the Panama Canal flows all the way to Savannah, Georgia? Maybe not literally, but the Port of Savannah has the largest single container terminal in North America and, in its fiscal year ending June 30, 2015, handled 3.66 million Twenty-foot Equivalent [container] Units, or TEUs. The TEU is the standard measure of containerized freight, equivalent to 20 ft. x 8 ft. x 8 ft., and containers based on this standard can be moved seamlessly between ships and trucks.

Fully one third of the containers arriving or departing the Port of Savannah passed

through the Panama Canal, which is now undergoing a major expansion to add a third set of significantly wider and deeper locks (completion in 2016). The new locks will allow the transit of “post-Panamax” ships carrying 13,000 TEUs, or 260% of what Panamax ships now carry, requiring the port to dredge its waterways to handle these massive, deeper draft ships. On the land side, the growing number of containers moving into and out of the port by truck will seriously challenge the current roadway system, so the Georgia Department of Transportation (DOT) is building a new roadway, the Jimmy DeLoach Connector, to improve port access.

The current route to the port is via I-95 and GA SR 21, then onto local road Bourne Avenue for about a mile to the port entrance. With about 8,000 trucks now entering or leaving port facilities daily, there is already major traffic congestion throughout the area, even before the post-

Panamax ships arrive. The new 3.1 mile Jimmy DeLoach Connector, beginning near the existing Jimmy DeLoach Parkway terminus at SR 21 and extending south to Bourne Avenue at a point close to the port gates, will relieve truck congestion, shorten travel time, and keep most port-associated trucks off Hwy 21 and local roads.

The Jimmy DeLoach Connector requires six new bridges and new interchanges at Grange Road and at Jimmy DeLoach Parkway, all under a $73 million design-build contract awarded to Archer-Western Contractors of Atlanta and their design partner, The LPA Group (now Michael Baker International) of Norcross. Five bridges each require 2 tall abutments, configured with a mechanically stabilized earth (MSE) retaining wall in front of a bridge seat supported on (square precast concrete) piles (Figure1). This arrangement (Figure 2) is known as a “mixed” MSE abutment, because the MSE structure retains the soil while the piles carry the bridge load through the reinforced soil to the foundation below. In addition to the new abutments, an existing Reinforced Earth® wall (where the original Jimmy DeLoach Parkway transitions into the Jimmy DeLoach Connector) had to be reconfigured and extended. Archer Western asked The Reinforced Earth Company (RECo) to design and supply the MSE structures for this project.

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Figure 2. Mixed MSE Abutment

GDOT generally requires the use of mixed abutments in settlement-prone areas such as this coastal environment. To avoid formation of settlement-induced voids beneath these pile-supported bridge seats, and possible resulting undermining of the approach slabs, the DOT also requires a waiting period before pouring the bridge seat. Geotechnical engineer United Consulting, (Norcross), developed a table of short term (during construction) and long term (post-construction) estimated settlements for each abutment. Some settlement estimates were as much as 24 in. short term/30 in. long term. At some of the higher-settlement locations, United recommended a staged construction process, i.e., building the abutment wall to mid-height, waiting 30 days for settlement to take place, completing the wall, then the typical 30-day waiting period prior to casting the bridge seat. To further reduce the magnitude of settlement, several of the MSE walls were specified to be undercut by 18 in. and backfilled with granular material. Having identified an excellent local source for the MSE structure backfill (well-graded sand, φ = 33°, unit weight 115 pcf. at optimum moisture content), the contractor simply backfilled the undercuts with the same material.

Archer Western stated a strong preference for the Reinforced Earth option offered by GDOT’s contract, not only because of its many successful projects completed with RECo, but also because RECo is known for its thorough designs, attention to detail, and high quality precasting (in this case, provided by a company-owned precast plant in Newnan, GA). So it is no surprise that both the Archer-Western/RECo relationship and the construction process itself flowed so smoothly. RECo works hard to make and keep such relationships, because good products and good relationships benefit all parties.

The abutments were built in pairs, working mostly south to north along the project alignment. The contractor requested precast coping for the abutments and chose a precast half-connector (Figure 3) to serve as both the coping and the foundation for the cast-in-place traffic barrier atop the reconfigured and lengthened existing Reinforced Earth wall. Contractors like RECo’s precast top-out units (copings, traffic barriers, and half-connectors) because they are

precision-cast to fit correctly and they significantly reduce top-of-wall forming and labor, improving work flow, safety and the bottom line. The forms are owned and maintained by RECo, assuring timely production on every job.

One bridge spanned the Norfolk Southern Railroad (NSRR). Since the walls were outside the railroad’s mandatory track clearance envelope (Figure 4) and all wall erection work could be done on the backfill side of the wall face, there were no railroad-induced MSE construction delays. The only substantial railroad-related impact occurred during superstructure construction, when

working directly the over the tracks, but of course that was long after the Reinforced Earth abutments had been completed.

So whether you are receiving container shipments from the Panama Canal, building an airport or a highway or an industrial project, or retaining a simple cut or fill in your home town, be sure to take advantage of the quality, predictability and experience of The Reinforced Earth Company.

PrecastHalf-connector

C.I.P. Traffic Barrier

(For Clarity Not all Rebar Shown)

C.I.P. Moment Slab

(Solid Bars are Included in Precast Unit)

Front Face ofWall Panel 50mm x 4mm Ribbed Reinforcing Strip

Level Up Concrete

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Figure 3. Precast Half-connector and C.I.P. Moment Slab

Figure 4 . Mixed abutment adjacent to Norfolk Southern RR

Noteworthy Projects

I-5 AlondraReinforced Earth®

Location: Santa Fe Springs, CA

Owner: California DOT

Contractor: C.C. Myers, Inc.

Engineer: California DOT

IH-35 @ Main Street Reinforced Earth®

Location: Norman, OK

Owner: Oklahoma DOT

Contractor: Manhattan Road & Bridge

Engineer: Oklahoma DOT

Rt. 340 Bridge Replacement Reinforced Earth®

Location: Little Rock, AR

Owner: Arkansas State Hwy & Transportation Dept.

Contractor: Manhattan Road & Bridge

Engineer: Bridgefarmer Assoc., Inc.

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