A hybrid solution
Concrete garage to accommodate Bossier's developing Riverwalk

By Sam Barnes

As rising fuel costs pushed the envelope this winter and spring, 20 trucks lumbered down the interstate each day to deliver structural and architectural precast concrete for a new parking garage in Bossier City.

The $20 million hybrid garage is made of 6,500 pieces of precast and 10,000 cu. yds. of poured-in-place concrete and will accommodate the Louisiana Riverwalk retail development along the Red River. Walton Construction Co. LLC of Shreveport is building the garage.

Rising fuel costs prompted precast supplier TDI Parking of Tulsa, Okla., to begin looking for a production area a little closer to the site.

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"We began doing some of the work in Dallas because it's a lot closer to the jobsite than Tulsa (the main production site)," said Gene Matthews, TDI erection manager. "Moving some of the work there helped keep costs down." The structural precast members were manufactured in Tulsa and Dallas and the architectural panels that clad the garage exterior were made in Little Rock.

Having to coordinate deliveries from three locations created scheduling dilemmas for Matthews because no more than a day's worth of precast could be stockpiled at Walton Construction's laydown yard less than a mile away. This meant the precast had to arrive "just in time."

"To make it work, we had a majority of the precast manufactured before the job even began," he added. "We could only produce about six precast components a day but we erected about 20 a day, so we had to have more than half of them made before the project started."

The four-level hybrid garage has a poured-in-place concrete deck, which also lowers cost by reducing the foundation necessary to support the garage.

Decking for the four-level parking garage required 4,500-psi concrete supplied by TXI's Bossier City plant. The 5-in.-thick elevated slabs are reinforced with post-tensioning cables.

Walton is pouring the first garage deck and TDI is pouring the upper level concrete.

"To adhere to a tight schedule we're making two 9,000-sq.-ft. pours a day,"said DeWayne Akins, general superintendent. "We start at about midnight and pump them back to back. By noon we're finished."

Placing the concrete during the early morning hours reduces traffic complications and service problems from the concrete supplier.

"We also get it down before the sun heats things up and slows our setting time," Akins added.

Matthews said TDI is using a new flying form system at the site to place the ready-mix for the upper garage levels.

"We've got a patented form that allows us to set up to 10,000 sq. ft. of forms, get a rod buster on it and get it poured the next day," he added.

The hybrid garage can be built faster than an all-precast garage, Matthews said, "since precast has to have a three- to four-month lead time to allow for production. Less precast means less lead time." The garage design was initially created by Culp & Tanner Inc. of Chico, Calif., to withstand earthquakes "and we found that it works good everywhere," Matthews added.

Brad Roberts, project manager with Walton Construction, said contractors were given the choice of bidding the project as precast, cast-in-place or hybrid.

"To bid the job as hybrid we had to do a good bit of re-design to existing plans by Carter & Burgess Inc. of Dallas," Roberts said. "The re-design was figured into the price of the hybrid system when we bid the job. Easier constructability was the main reason we went with the hybrid system. The project had a tight schedule and the hybrid system seemed to be faster and easier to erect."

The decision appears to have been a wise one. The project is running a few days ahead of schedule despite about 40 days of rain delays since the project's December groundbreaking. The garage will be finished in September.

L. G. Barcus & Sons of Oklahoma City had to drill about 1,200 14-in.-diameter, 65-ft.-deep shafts as foundation for the garage. The process was originally expected to take 30 days.

"Weather really hit us hard during the middle of drilling auger-cast piles and 30 days turned into more than two months," Roberts said.

To make up lost time, crews worked seven days a week when possible.

Akins said the jobsite was formerly a residential area, so site preparation required the removal of underground utilities and some house slabs.

"We also installed a 42-in.-diameter concrete stormdrain directly beneath the footprint of the new garage to facilitate site drainage," he added.

Once out of the ground, the job progressed more smoothly.

"With much of the precast columns, beams and girders already produced, it became a matter of just piecing the garage together," Akins said.

By the end of April, all of the structural precast and one-third of the architectural precast had been erected. Architectural precast is "is colored a light brown and has some reveals, but nothing really fancy," Akins said.

Other components of the parking garage include a lobby with skylights, two elevators, two escalators and a stairwell.

"Eventually, the developer will work out a way to connect the garage to adjoining buildings (that are not yet built), but as of right now that's not in the plans," Roberts said.

The crew is also building a road off of Bass Pro Shop Drive leading to the new garage and installing a steel arched-culvert bridge across a pond that was dug for landscaping purposes.

"We're still trying to push the project further ahead of schedule," Roberts said. "There's a $10,000-a-day bonus for finishing early, with no cap."

Useful Sources:

For more information about the Louisiana Riverwalk, go to: http://www.louisianariverwalk.com/