Last September, at the scene of a structural collision incident on I-45 in downtown Houston, Texas, transportation officials encountered a troublesome set of circumstances. A southbound-traveling semi-truck - too tall to pass safely under the West Dallas Street bridge - had slammed into the structure, wedging itself beneath the overpass. Damaged beyond repair, the bridge required immediate replacement.
After engineers from the Texas Department of Transportation (TxDOT) evaluated the situation, the agency fast-tracked this $2.7-million emergency repair project by enlisting the services of contractors handling the nearby construction of new entrance ramps at Houston Avenue and Allen Parkway. Houston-based mc2 main lane industries ltd. (mc2 main lane), a subsidiary mc2 civil inc., was selected as the prime contractor.
A Fast-Track Undertaking
The original bridge was demolished and the new bridge built - including the placement of beams and pouring of concrete - over a six-week period. Work began with the demolition of the West Dallas bridge over a single weekend in early November. Crews then placed steel girders over the main lanes of I-45 and completed the pouring of the concrete for the bridge surface over a series of weekends and evenings.
"The project team had a good game plan, and the boots on the ground made our efforts successful," says David Boehm, President of NBG Constructors. "What impressed me the most were the foremen, superintendents and laborers who devoted their time on weekends and overnight to reconstruct the bridge."
The bridge replacement project achieved substantial completion in December, and the new freeway overpass was opened to commuters in the same month. "It was a remarkable feat to get an entire bridge reconstructed in a short period of time," says Quincy Allen, P.E., TxDOT Houston District Engineer. "We are thankful to the community for their patience and our crews and the contractors for their hard work and dedication."
Typically, it takes a minimum of four-to-five months to execute this type of project - and that is after the design has been formulated and shop drawings approved, which can take anywhere from six to 12 months for this size and type of structure.
"The most challenging aspect of the project was the accelerated timeline for design and construction. Hence, the project team met daily to resolve issues and revise plans as necessary," says mc2 main lane Chief Operating Officer Billy Mitchell.
According to TxDOT, one of the most urgent concerns on this project involved temporarily decommissioning a bridge that links West Houston Street to the downtown area. Transportation officials worked double-time to fast-track planning and approvals processes to minimize the bridge replacement's impact on tourism and important events within the community.
One factor driving quick project delivery involved the Super Bowl. In February, the city hosted the NFL's 51st championship game at the NRG Stadium, where the New England Patriots faced off against the Atlanta Falcons in one of the world's biggest sporting events. This iconic event would take place just five months after the big-rig accident. In the two weeks leading up to the game, several pre-game events were scheduled to take center stage in downtown Houston.
"Having the bridge partially closed or closed during those two weeks would have been very bad. The efforts of all those involved averted a major situation for the city," says Danny Perez, TxDOT Public Information Officer.
Mitchell adds, "This project was treated in a manner similar to a design-build project. Team members stayed in constant contact while remaining open to the best solutions to project challenges during the entire process. All parties had the same goal in mind - to get the project safely completed in accordance to the plans and specifications, on time or ahead of schedule."
A Collective Focus on Creative Solutions
"It takes a village."These first four words of a well-known proverb perfectly describe the dynamics needed to successfully complete a project of this scope and scale. A whole host of infrastructure planners, design experts, builders, materials suppliers and others rallied together find creative solutions that helped accelerate the project timeline.
As general contractor, mc2 main lane took the lead on building the approach slabs, setting up traffic control, and coordinating with and assisting subcontractors and suppliers. Mitchell states, "I am most proud that our teams participated in and supported each subcontractor's work scope in order to assure their success. This was a great example of everyone working together to achieve a common goal."
The key players responsible for developing bridge demolition plans included mc2 main lane, NBG Constructors and Southern Crushed Concrete. "Bridge demolition was difficult due to the structure being damaged," notes Mitchell. "Significant effort went into the planning of the structure demolition in order to avoid collapsing the structure as opposed to systematically disassembling it. This was particularly a concern when the bridge deck was being removed due to the weight of the demolition equipment and the need for that equipment to be on the bridge during demolition of the deck."
King Fabrication, which specializes in heavy specialty steel-fabricated products, designed and fabricated the 138-foot-long steel bridge. During conception stages the fabricator addressed constructability issues and provided budget estimates - an added boost to the overall project timeline. Additionally, the utilization of readily-available building materials sped completion of the structural steel for the bridge, greatly reducing the lead time for procurement and fabrication.
After modifying the existing bridge abutments and the support in the center of the freeway, crews installed a total of four prefabricated steel beam pairs across the span to support the rebuilt roadway. On the night that beams were being set for the new bridge, team members who were onsite were given the freedom to make critical decisions as work progressed, which saved several days in the project schedule.
The steel beams were fabricated in pairs, with the diaphragms welded in place and the finish coating applied at the shop. Another method that hastened construction efforts involved the assembly and erection of girders in pairs with the permanent metal bridge decking. Heavy-duty lifting eyes were placed on the beams to facilitate the setting of the paired assemblies, with diaphragms placed between the pairs immediately afterward.
Bridge's Increased Vertical Clearance Heightens Safety
The new West Dallas bridge has approximately 18 inches of added height, resulting in a vertical clearance of more than 16 feet. The added clearance is intended to help prevent future collisions with the underside of the structure.
For the protection of motorists - and to preserve roadways and bridges - the state of Texas has strict size and weight limitations for vehicles and loads on state-maintained roads. According to Chapter 621, Section 207 of the Texas Transportation Code, the maximum height of a vehicle and its load may not exceed 14 feet without a special permit (and sometimes a traffic escort is also required). Furthermore, the operator of a vehicle that is higher than 13 feet, 6 inches is responsible for ensuring that the vehicle can safely pass through all structures in its path (such as bridges and underpasses) without touching the structures. Ultimately, if the height of a vehicle causes any damage, the owner of the vehicle may be held liable for the damages.
With a vertical height topping out at 14 feet, 7 inches, the semi that collided with the West Dallas bridge last September was too tall to pass safely beneath the structure, which at the time had a vertical clearance of 14 feet, 1-inch. Had the vehicle operator gone through the mandatory special-permitting process for this overheight load, he likely would have been directed to use Loop 610 of the Sam Houston Tollway instead. During an interview with the Houston Chronicle last year, Adam Shaivitz, a spokesman for the Texas Department of Motor Vehicles, stated that permit loads are not generally routed for travel through the heart of downtown Houston.
A Calculated Approach to Traffic Control
Work windows and lane closure times had to be significantly condensed, since the West Dallas bridge spans a heavily-traveled roadway within Houston's active central business district. According to TxDOT, various traffic control scenarios could have significantly increased the duration of the project. In an effort to find the most ideal traffic control solutions for the area, TxDOT hosted multiple meetings where input was solicited from local area experts, including Lone Star Traffic Safety and police officer representatives. "TxDOT consistently stressed that coordination with impacted stakeholders such as the city of Houston and the Downtown District was also crucial," adds Mitchell.
TxDOT's Public Information Office and other entities carefully coordinated their efforts to keep the traveling public up to speed on road closures and to provide helpful information about alternate routes. One contributor to this effort was Houston TranStar, an organization comprised of Houston city officials and other representatives from Harris County, METRO and TxDOT.
While construction activities took place, all northbound and southbound mainlanes of I-45 between I-10 and U.S. 59 were shut down. During these closures, northbound travelers were rerouted to U.S. 59 northbound, then to I-10 westbound before re-entering I-45. Southbound traffic was rerouted to I-10 eastbound, then to U.S. 59 southbound before returning to I-45.
"While many in the community, including those in downtown Houston, had concerns about the closures needed for this work to happen, once work began and they all saw how quickly the old bridge was demolished and the new bridge constructed, they were very appreciative of all our efforts," says Perez. "This was absolutely a team effort."
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