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Bracing Up: Protecting Your Construction Investment

After Hurricane Katrina hit in 2005, the sleepy area of Covington, Louisiana, began to experience an industry boom as a result of many companies seeking a safer, more elevated area. Chevron, Corp. needed a new headquarters for their Gulf of Mexico Operations as a result of the hurricane. Covington’s safe elevation and remote setting fit the needs of this building. The Chevron project, a $78 million, 300,000-square-foot, design-build project office building, was built in Covington in a record eight months. The building design incorporates low rise three- to four-story concrete Tilt-Up panels and glass. Constructing a building of this type in a hurricane region – during hurricane season – required extra bracing to protect the panels. The contractor and the owner made additional bracing considerations to ensure that the building was well reinforced and protected in an area where wind speeds can suddenly become ferocious.

Bracing design guidelines developed by the Tilt-Up Concrete Association (TCA) recommend that panels be braced for period wind conditions that might influence life-safety, per ASCE 7. Standard bracing designs are therefore not expected to withstand the intense wind loads of storms that would have cleared the jobsite well in advance of the incident.

However, bracing the panels for hurricane wind speeds was important for the builder risk insurance. If high winds occurred after the panels were erected there was a good chance that the some of the panels could blow down, causing major construction delays. To avoid this, the Tilt-Up panel bracing capacities were increased to withstand hurricane force winds.

At the start of the project a few challenges immediately arose:

    • Could the project schedule be met?
    • Could the panels be cast on site with limited space?
    • Could a cost effective 300-ton crane be found to erect panels?
    • Could the panels be braced to the outside of the building to expedite structural steel erection?
    • The owner’s insurance company requested the panels be braced for 120 mph wind speeds since the Tilt-Up panels would be standing without structural steel complete during the hurricane season. They were willing to pay a premium for the bracing. Could this be done?
    • How can 2 foot wide x 68 feet tall link panels be braced?


The Chevron project consisted of 116,969-square-feet of Tilt-Up panels, 65,000-square-foot casting bed, two months of 300 ton crawler crane rental and two months of brace and Burke Badger rental. The schedule required for the project included a 16-week time frame for the foundations (April 30 to August 23, 2007) and an 18-week interval for the Tilt-Up panels (May 3 to September 9, 2007).

The Chevron panel bracing design involved a special bracing analysis to accommodate the higher wind speeds than normal. A hurricane analysis was modeled to ensure the best bracing solutions were used. Due to the severe forces being transferred to the braces and the relative height of the panels in relation to the floor slab, a bracing scheme was devised incorporating the largest Tilt-Up braces in the market, Super 52’s and “Badgers,” auger-like brace anchors that are driven into the ground outside the perimeter of the building and attached to the massive braces to substantially increase the load transfer capacity of the brace to the ground. The biggest challenge of all was a 194 kip panel (194,000 pounds) being pushed by the severe 120 mph wind load at a height of 70 feet.

The overall construction schedule was already set at an eight-month duration spanning from the start of earthwork through to the issuance of the temporary certificate of occupancy. The Tilt-Up panels were on the critical path of this schedule and accommodating the increased bracing scheme only heightened the intensity during this section. Once the Tilt-Up panels were lifted and braced, then structural steel could proceed, followed by the placement of concrete on the floor decks. To accelerate the Tilt-Up panel schedule, casting beds were installed for the panels that would not fit of the floor slab. The crew worked overtime seven days a week and the reinforcing crew worked during the night.

The site wasn’t very large and had a lot of constraints that would dictate the location of the casting beds. There was a large retention pond to the south and a large fence with a public street to the north. The construction around these obstacles had to be carefully sequenced.

One challenge was that the Tilt-Up panels weighed around 200k which required a 300-ton crawler crane to erect the panels. The local market did not have a 300-ton crawler crane that was available and had any experience erecting tall, heavy, Tilt-Up panels. Sunshine Erectors, a Tilt-Up panel erector out of Florida was contacted. Sunshine Erectors had a 300-ton crane, it was available for the time frame needed, and the most important part is Sunshine’s crane operator had experience erecting large, four-story Tilt-Up panels.

The brace design proved tricky, since the steel erection had to be expedited. An inside as well as an outside brace design was used. The panels were initially braced to the inside, which allowed a faster panel erection schedule, and then braces were reinstalled to the exterior to allow the faster steel erection. Areas such as the retention pond did not allow room to brace to the exterior, leaving one corner of the three-story building with interior braces.

A big concern early on in the planning stages of the project was how to brace the 68 foot tall x 6 foot wide panels. They were in the connecting link that joined the four- and three-story building together. These panels also had a full height glass curtain wall between them. The first concern was how to erect a panel so narrow. Then the challenge was how to brace the panels so they would stay plumb (in both directions) until the structural steel was erected. The solution was that in addition to the typical panel brace design, a horizontal tube brace was installed that went between the panels at the same elevation as the brace point on the panels. The horizontal tube brace held the panels and in the correct position (left to right) while the structural steel was erected. This horizontal tube brace was a success and the entire glass curtain wall fit correctly.


The panel bracing design for the Chevron building started out with a standard 72 mph wind design with standard equipment. It required 14 Super 32s each with two 10-foot extensions. They were too many braces to use with Badgers, an exterior helical ground anchor system.

The standard wind load design uses a force coefficient factor Cf = 1.2, which is intended for solid panels. However, ASCE 7-95 allows the removal of openings from the projected area of the panel with an increase in the Cf factor. (Note: The latest version of ASCE 7 is ASCE 7-05, but the section referred to in the TCA document is unchanged from ASCE 7-95. For the sake of consistency with TCA, ASCE 7-95 is used here.) It provides a chart with various force coefficients dependent on the ratio ! of solid area to gross area. For example, in Panel 8 the gross area of the panel is 2,305 square feet and the total area of the openings in the panel is 938 square feet. Therefore, ratio ! = (2,305-938)/ 2305 = 0.59. With this area ratio, Cf is raised to 1.6, which results in a 33 percent increase in wind pressures, but the 41 percent decrease in surface area yields a total resultant wind force that is reduced by 21 percent and the number the number of Super 32 plus extensions to 11.

Substituting the Super 32s with stronger Super 52s with no extensions and a 10,700-pound safe working load, the number of braces was reduced to four. This made the Badgers much more economical with installation spacings at approximately 8 feet.


The owner was then concerned about construction during the hurricane season (June – August) and wanted extra protection for panels during this period. He expressed the opinion that the design wind load for bracing should be 120 mph with exposure B per structural requirements in accordance with ASCE 7-02 and ASCE 37-02 (120 x 0.8 = 96 mph). The request came after the bids were submitted and approved, bringing the question, who is responsible for the costs of increased protection? The options to provide the extra protection were to brace panels on both faces or to add extra braces to the exterior.

The largest panels (panel 8) were then reanalyzed at 80 mph (0.8 x 100), 88 mph (0.8 x 110), 96 mph (0.8 x 120) and 104 mph (0.8 x 130). Doubling the Super 52 braces met 96 mph requirements with standard safety factors (120 mph at ultimate strengths). After it had been established how to achieve the extra protection, the question arose as to who is responsible for the costs of meeting this extra protection. Tilt-Up Concrete Association’s Wind Bracing Guideline SEI/ASCE 37- 02 offers recommendations for building in hurricane areas and who is responsible for the costs of extra protection:

“Between August 1 and October 31, a basic wind speed of 90 mph (40m/s) shall be permitted provided additional bracing is prepared in advance and applied in time before the onset of an announced hurricane.”

Then the Guidelines wisely goes on,

“The SEI/ASCE 37-02 document is not clear as to what wind velocity is to be used for the design of this additional bracing, 0.520V50, 0.8V50 or V50. For reference, a wind velocity of 112 mph (0.8 x 140 mph) increases the load generated by a 72 mph wind velocity by 142 percent. A wind velocity of 140 mph (V50) increases the load generated by a 72 mph wind velocity by 278 percent, which could triple the number of panel braces required. The additional braces could be expansion bolted to the panels, if required, or additional brace inserts could be cast into the panels during construction to allow the installation of additional braces. However, even with additional braces in place, the floor slab will more than likely not be strong enough to resist the additional brace loading. Should the floor slab then be thickened and/or reinforced in advance for this potential additional load? This could significantly impact the cost of constructing Tilt-Up buildings in hurricane regions.

“The determination of wind velocities to be used to design Tilt-Up panel bracing, or any bracing for that matter, during construction is a complex issue. For areas outside of hurricane regions, the loads to be used are clearly delineated. In regions subject to hurricanes, an argument can be made that the wind velocity used for the design of construction period wind bracing becomes, after the level necessary for life safety, a risk-based determination and not a life safety issue since the project site would surely be abandoned during a hurricane. Then the decision regarding what construction period wind speed to use for bracing design should be made by the owner and their insurance provider if they want bracing designed for more than that required for life safety since they are the one paying the cost and taking the risk.”

Without this guideline and statement from TCA, concrete sub-contractor and TCA member, Concrete Strategies, may have been on the hook for costs associated with the extra hurricane protection. Instead, the owner agreed to and approved all expenses for the extra protection.

The project then faced a new challenge: the three-story panels required the same bracing scheme as the four-story panels but the proximity to ponds limited the Badger location from the South wall line. The solution was to make shorter Super 52s with the same 10,700 pound strength. Therefore, the Super 42 was born out of necessity.


The panel erection bending stresses approached 2,500 psi in the thinner 91⁄2 inch thick leg sections, which is five times the specified strength of 500 psi. It required a strongback that had a moment capacity of 85 kip-ft.

A custom double channel strongback would be sized at 12C20.7, resulting in an enormous expense. The solution was to stack two standard C8x11.5 double channel strongbacks. The combined section properties yielded a strength of 92 kip-ft. That’s nearly three times the strength of a single C8x11.5 double channel strongback. It required special fabrication of new strongbacks that had predrilled holes in flanges for bolting stacked channels to each other. Also, it allowed the concrete accessories distributor to justify purchasing new strongbacks, and then re-rent them to Concrete Strategies (and use them as standard channel strongbacks later).

In summary, Chevron was a ground- breaking project for Tilt-Up bracing concerns. In addition to the innovation in meeting the construction challenges of building in a hurricane zone, Chevron’s facility is the first office in Louisiana to receive the federal government’s LEED certification from the United States Green Building Council. This project has achieved LEED Gold certification.

The challenges faced in building this facility allowed Meadow Burke the opportunity to launch and implement on a large scale several new products. These included: Super 52 and 42 Braces, Badgers, Double Brace Badger Connector, and 8C11.5 Stackable Strongbacks.

The bottom line for the preconstruction phase of any future Tilt-Up project with unordinary panels is to consult with your erection and bracing engineer from your Tilt-Up concrete accessory supplier. You never know what non-standard analysis or non-standard product will be developed to help overcome panel erection and bracing challenges.

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TILT-UP TODAY, a publication of the Tilt-Up Concrete Association, is THE source for Tilt-Up industry news, market intelligence, business strategies, technical solutions, product information, and other resources for professionals in the Tilt-Up industry. A subscription to TILT-UP TODAY is included in a TCA membership. Subscriptions for potential TCA members are also available. If you would like to receive a complimentary subscription to the publication, please contact the TCA.