One of the most important bridges that the Louisiana Department of Transportation and Development (LADOTD) manages is the I-10 Twin Span Bridge crossing Lake Pontchartrain between Slidell, La., and New Orleans. Approximately 5.5 miles in length, this crossing includes a total of 11 miles of bridges that connect New Orleans, New Orleans ports and the petrochemical industry along the Mississippi River. The bridge, which serves as one of the main evacuation routes for New Orleans, was severely damaged by Hurricane Katrina, rendering it unusable in either direction. Although the LADOTD temporarily repaired the bridge, the extensive damage meant that it would need to be replaced. To rebuild and repair these structures following Hurricane Katrina, LADOTD turned to Bentley software—including InRoads, STAAD and LEAP CONSPAN—to help ensure the success of the project.
DOTD acts quickly in a challenging environment
When Hurricane Katrina devastated the Gulf Coast in August 2005, both the east- and westbound lanes of the I-10 Twin Span Bridge suffered severe damage, including 64 lost spans, 473 spans with shifted alignment and approximately 4.3 km of broken bridge railing. Given the extent of the destruction in the entire region, the LADOTD faced many challenges in repairing and ultimately replacing the bridge, including enormous competition for resources—especially equipment and personnel.
“With these conditions, it was hard to do any project, let alone a project of this magnitude,” said LADOTD Bridge Engineer Administrator Arthur W. D’Andrea.
The LADOTD, however, was quick to initiate plans to repair damaged I-10 bridge structures, with construction beginning just 14 days after Katrina and temporary repairs completed within four-and-a-half months. It was clear, however, that the repaired structure was only a temporary solution—the bridge would need to be replaced.
“Selling” the new bridge
The LADOTD’s next challenge was securing federal funding to replace the heavily damaged bridge. Its goals for the replacement bridge included better storm protection, safe accommodation of six traffic lanes, enhanced barge collision resistance and utilization of well-known materials and techniques to provide for a low-maintenance and 100-year-long service life.
“It took us about six months to actually get a final commitment to get the money,” said D’Andrea.
To help convince the U.S. federal government of the necessity for a new bridge, the LADODT used Bentley’s MicroStation, with its Luxology rendering engine.
“With MicroStation we were able to create renderings, which really helped us sell the need for the replacement bridge,” said D’Andrea.
Collaborating on new bridge designs
Planning for the replacement bridge began in September 2005, with construction scheduled to start in spring 2006. The engineers had only four months to complete the entire design, acquire permits, complete the geotechnical analysis and assemble over 1,000 engineering drawings. The LADOTD designed the new I-10 Twin Span Bridge using an integrated set of Bentley software with MicroStation as its primary design tool, InRoads for roadway design, STAAD for general structural design, LEAP CONSPAN for bridge superstructure and LEAP RC-PIER for substructure design. All together, these products were used to create and manage more than 1,700 plan sheets that included designs for a structure with 444,000 linear ft of 36-in. precast concrete piles, 317,300 linear ft of BT78 girders and 29,600 linear ft of AASHTO TYPE III girders.
The LADOTD knew that collaboration would be essential to successfully deliver a project of this magnitude. Civil engineers, bridge engineers and geotechnical engineers needed information to be accessible and presented in a format that could be understood and consumed easily. They also recognized that all the information collected and generated during the design project would be critical to ensuring the continuity of the new I-10 Twin Span Bridge through operations and maintenance.
Bentley software helped those involved in the project collaborate quickly and efficiently. For example, using ProjectWise, they were able to quickly integrate a design team distributed over multiple locations and enable everyone to work together efficiently on bridge design. The design team could share files in a reusable format, open them using their preferred software, quickly review submittals and make changes and relate the data automatically to relevant aspects of the overall design. ProjectWise was also used to store all data received by partners, consultants and contractors.
“Not only were there thousands of drawings, but tens of thousands of e-mails with attachments,” said D’Andrea. “One of the contractors had over 10,000 major activities that were being tracked. And within each of those 10,000 activities, if each one generated three e-mails, you’d have 30,000 e-mails.”
Equally important, ProjectWise was able to maintain the massive volumes of bridge design data with full integrity and security.
Bentley’s bridge design products also provided flexibility with the analysis of structural systems enabling LADOTD to be able to predict the performance of the bridge to meet the new design criteria for a safer bridge. In addition, Bentley design tools, including MicroStation, assisted the engineers by enabling them to present various scenarios visually, which provided clarity to the design; this clarity was essential in avoiding costly change orders and project delays. In addition, STAAD provided flexibility with the analysis of structural systems predicting behavior and producing better design outcomes.
Project delivered ahead of schedule and under budget
The $750-million project was executed by five separate contracting teams that took on different tasks on a tight schedule, including:
• repairing and adding to the old structures severely damaged by Hurricane Katrina;
• demolishing the damaged twin span structures;
• constructing the brand-new Twin Span Bridge; and
• disassembling and storing the one mile of temporary ACROW bridge.
Adding to the complexity of these tasks, contractors had to complete tasks while maintaining ongoing traffic flows, respecting the state’s right-of-ways and working in a chaotic, post-Katrina environment.
Using Bentley software, the Louisiana LADOTD successfully avoided common challenges facing bridge infrastructure projects—fragmented data, lost time searching for information, lack of software interoperability, difficulty reusing data throughout the bridge lifecycle and constant re-engineering. As a result, the project was delivered quickly and under budget in very challenging conditions.
“We were able to not only complete the project ahead of schedule, but also return approximately 12% of the original $803 million to the hurricane relief fund,” said D’Andrea.
In September 2011, six years after the hurricane, both new 5.5 mile-long structures opened, providing enhanced service and hope for communities in the area.