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Jan. 5, 2015

Louisiana’s Segment K blends aesthetics into complex job

In north Louisiana, not far from the Arkansas state line, the Louisiana Department of Transportation and Development (DOTD) has been undertaking a megaproject with the intent of tying together a wide array of communities via the I-49 North Corridor. And now it looks as though the home stretch is finally in sight.

The I-49 North Corridor is a 36-mile corridor project to provide a four-lane interstate system with a 4-ft inside shoulder and a 10-ft outside shoulder from I-220 in Shreveport, La., up to the Arkansas state line. During the planning phase, the project was divided into 11 segments labeled A through K, the better to gauge and demonstrate strategic progress. Segments E through I opened tp traffic in November 2013. Segments A through D opened November 2014 leaving the final two segments (J and K) for completion. Segment J was awarded for construction in early 2013, and recently DOTD selected TRC Engineers Inc. to provide all of the engineering services associated with the provision of preliminary bridge plans and final bridge plans for Segment K in Shreveport. AFJM was tasked to provide riadway design services. 

The Segment K project begins at its proposed interchange with I-220 and proceeds in a northerly direction for approximately 1 mile to a proposed interchange with Martin Luther King, Jr. Drive (S.R. 3194). The project includes the design of a portion of the I-49/I-220 interchange, and a partial cloverleaf interchange at MLK Drive. The project includes seven structures. The Ramp EN (3,070 ft), SE (3,300 ft) and WN (700 ft) bridges incorporated dual design with precast concrete segmental post-tensioned box girder and trapezoidal steel box girder superstructure alternatives. The I-49 over MLK Drive bridges (462 ft each) consist of twin BT-72 precast pre-stressed concrete bulb-T girder superstructures. The I-220 over Russell Road bridges (322.5 ft each) consist of widening the existing steel plate girder bridges. 

The project was on an accelerated schedule where multiple TRC design teams and sub-consultants completed the work with 100% final plans submitted to DOTD on Feb. 14, 2014, approximately 12 months following the Advance Notice-To-Proceed. During final design services, the project was divided into two phases to aid in funding and acquiring final authorization from FHWA.

Design development

On June 6, 2006, TRC was given Notice-to-Proceed for the preliminary design of all bridges on the project. On May 25, 2007, the project was placed on hold due to funding and other program-related items. On July 7, 2011, DOTD set up a meeting with the American Segmental Bridge Institute (ASBI), TRC and another consultant to discuss the potential for the incorporation of segmental bridge construction on the Segment K interchange project and another interchange design located in New Orleans, La. On Jan. 5, 2012, TRC learned DOTD would move forward with the development of final plans for the implementation of a segmental bridge design for the three ramp structures (EN, SE and WN) that facilitate traffic movement to and from I-49 and I-220.

One of the key issues in regard to the consideration of segmental construction was the number of segments to be fabricated. The estimated number of segments included a minimum of 750 for the three bridges. This number of segments was considered beneficial to facilitate an economical bid for segmental construction. Another option for consideration to facilitate an economical design was the core section of the box girder. From the preliminary layout of the span arrangements for the bridges, it was determined that the three ramp bridges could use the same geometric core of the segmental box in accordance with an ASBI standard segmental box section. Only the cantilever wings would vary to accommodate variable bridge widths.

Following the determination that post-tensioned segmental concrete box girder construction was a viable alternative, the design team discussed the consideration of adding a second alternative to incorporate trapezoidal steel box girder construction. The steel box girder alternative provides an aesthetically pleasing structure, as does the segmental option. Two other benefits include added torsional capacity and ready shipment of the sections from the fabrication plant. Designing the two alternatives would aid in keeping the bid prices competitive. Thus, the DOTD had the project scoped to include both post-tensioned segmental concrete box girder and trapezoidal steel box girder construction.

The three ramp bridges include a total length of 7,070 ft of bridge structures. With the I-220 roadway on the surface level, Ramp EN is on the third level, Ramp SE is on the fourth level and Ramp WN is by itself a bridge structure elevated from the ground level. 

Bridging aesthetics

The design team believed in the creation of a bridge where public involvement and context sensitivity were integral parts of the design. To that end, the project architect and engineers worked closely to identify the elements in the project which present visual enhancement opportunities. The design team focused on the development of pleasing and harmonious shapes for the piers, abutments and the superstructure. Those dominant elements also were supplemented through detailing of reveals, barriers, lighting, decorative panels, and abutments.

The design process was complicated by the need to advance both a concrete superstructure and steel superstructure through final design. Both options were used during the bidding process with the lowest responsible bid alternative to be selected by the DOTD. Therefore, both the steel and concrete options needed to be visually similar, ensuring that the results were as close to the same as possible regardless of the bridge selected for construction. The design team began by focusing on the development of a family of piers that would satisfy the wide-ranging requirements of both the span configuration and the variation in superstructure types. 

After further refinements, a meeting was held between the design team, DOTD and the Shreveport Regional Arts Council (SRAC) to discuss the design approach to the bridges. Focus was centered on ways to provide input into the design of the bridges by the broader art community of Shreveport. Two areas were identified where this input could be provided in a manner consistent with the goals of the project. 

First, the final design for the pier decorative panels was to be determined through a call-to-artists. Interested artists were provided with the set parameters for the decorative panels, including overall size and maximum depth of reveal. The final design would then be incorporated into the bridge project without affecting constructability, price or schedule of the project.

Pier medallions also were developed for the MLK interchange. These medallions depict an image of Martin Luther King, Jr. Due to the smaller size of the bridge piers in this location, the medallions will be fabricated from steel plate and mounted 2 in. off the face of the pier to create a strong shadow line.

The second area identified for refinement included the retaining walls at the MLK interchange. The SRAC expressed a desire to install a large mosaic tile image on an area of the bridge. DOTD agreed to adjust the configuration of the abutments to create a half-height retaining wall at the interchange. This wall creates an area where the art installation can occur at a future date. 

Options for aesthetic lighting were discussed and SRAC expressed an interest in aesthetic lighting for the bridges. Options were developed and discussed with both DOTD and SRAC. The final option selected for the project utilized color-changing fixtures that can be set to a number of combinations. The color-changing lighting can reflect seasons, community events or holidays, and can serve as a palette for future design by the art community.

Finally, the color of the bridge was discussed and the colors were chosen to allow the bridge to sit quietly on the landscape and blend with the natural surroundings. The color selection also considered long-term durability and fading, so that the bridges would continue to look aesthetically pleasing for many years in the future. 

Always on time

During the development phase of the final design services for this project, TRC developed a comprehensive Project Quality Control Plan (PQCP). This PQCP provided project-specific guidance to the project team on the minimum quality control (QC) and quality assurance (QA) procedures, responsibilities and/or requirements for this project. This PQCP was developed in accordance with DOTD’s Policy on Quality Control and Quality Assurance (October 2012) and the FHWA/AASHTO Guidance on QC/QA in Bridge Design In Response to NTSB Recommendation (H-08-17) (August 2011).

Adherence to the PQCP helped the team achieve an on-time plan delivery at every phase of the accelerated project; compliance with DOTD expectations and requirements; minimal questions by the contractor during bidding; and success at timely delivery of quality contract documents while managing large design teams located in multiple national offices that included a number of sub-consultants.

Ready for lift off

Phase I of the project was let Feb. 5, 2014. It included most of the roadway work and the twin bridges of I-49 over MLK. The winning bid was $33.2 million. 

Phase II of the project, which includes three ramp bridges with dual alternatives and one bridge widening, was let April 30, 2014. The engineer’s cost estimate for Phase II was $129.4 million for the steel alternative and $135.9 million for the segmental alternative. The final winning bid is approximately 1.4% over the engineer’s estimate for that alternative.

The prime contractor for Phase 1 is Best Yet Builder, LLC and they have completed clearing and grubbing of the site as well as all utility relocations. The box culvert construction at McCain Creek is in progress and traffic has been shifted to the detour route where demolition and excavation at the I-49 over MLK interchange is underway. While no bridge work has started, all foundations will be drilled shafts. The first test shaft is scheduled to be installed the first week of January 2015.

The prime contractor for Phase 2 is PCL Civil Constructors, Inc. and they have completed clearing and grubbing of the site as well as all earthwork for the segment casting and storage yards. All foundations will be drilled shafts and they have installed three test shafts so far. They have begun construction of the widening of I-220 at the Russell Road Bridges that are to be widened under this contract. R&B

About The Author: Krone, Paul and Liu work for TRC Enginners Inc. Touchstone works for Touchstone Architecture.

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