Dallas+Cowboys+Indoor+Practice+Facility

Overview
In 2003, the Dallas Cowboys built a new indoor training facility. The fabric-covered steel frame building resembled more of a tent than a building, serving as an economical and simple covering for the field below. On May 2, 2009, a storm hit suburban Dallas, blasting the region with winds of over 60 miles per hour. As media, staff, and 27 Dallas rookies all took part in the practice below, the lights above began to sway and the fabric covering began to shake violently, prompting some to leave the premises. Soon the steel framing began to twist and pop, and within seconds the whole building came down.

by: //Cody McKean, Matt Underwood, Kourtney Wright// toc

Abstract
The Cowboys, along with all the other NFL teams that use similar facilities, know the value of practice and know that slacking off has great repercussions. It is ironic then, that the builders of their training facility acted with such poor professional practice. While there are many glaring problems with this entire debacle, they are all fundamentally based on poor procedure and sheer laziness. The building stood sturdily for nearly 6 full years, but when put into an extreme environment the poor craft of the structural framing, the lack of testing, and the sheer expediency of the facility led to a nearly fatal collapse.

Key Words

 * Dallas Cowboys
 * indoor facility
 * collapse
 * practice
 * failure
 * gable-roof structure
 * wind

Building Specifications and Purpose
The company, Canada-based Cover-All Building Systems and its U.S. subsidiary, Summit Structures, built the facility in 2003. In plan, the building was 204 ft by 406 ft (mere feet from the boundaries of the playing field below) and rose about 86 ft high. The structure consisted of 28 truss gable frames spaced 15 ft on center. The individual module was made of a triangular truss web that was supposed to be rigid and withstand winds of 90 miles per hour. However, the peak was a clear weak point because the trusses did not reinforce the top and bottom chords vertically. Also, the framing thinned to a point where it touched the ground, so the foundation was not as strong as it could have been. Cross-bracing in the structure provided lateral support, although none existed in the keystone section of the roof. The frame of the facility was steel that rose to gabled roof at a joint, and tensioned fabric covered the whole skeleton, both inside and out although the inner layer was untensioned, and only the outer layer put a force on the framing. The shelter served as a way of expanding the off-season practice complex while also providing shelter from the sweltering Dallas sun.

The Collapse
Although the builders of the facility assured the Cowboys that the facility would withstand gale force winds of 90 miles per hour, things already appeared wrong when a storm blasted suburban Dallas with winds between 60 and 70 miles per hour. However, due to the height of the structure, the wind forces near the top could have been even higher. Within minutes, the suspended lights began rocking, and the fabric walls began to ripple and shake. Finally, when the sound of popping steel could be heard, players, staff, and media all began to flood out of the space as the rest of the building fell shortly thereafter (see Video). Most escaped, but for some it happened too quickly - in all, 12 Dallas players and staff members were injured, including the Special Teams coach Joe DeCamillis, who suffered several non-paralytic vertabrae fractures in his spine. Others were scratched, knocked unconscious, or stabbed by debris, but all injuries were non-fatal and the players and on-site staff members all "went into rescue mode" (Formby) and managed to save everybody.

Causes of Failure
The causes for this failure lie mainly with the design and construction of the structure. Many of the original flaws were not even reinforced in the routine, scheduled 2008 upgrade. Many of the failures of the design were in the category of wind and air pressures. The design used the ASCE Standards for low-rise buildings (average height under 60 ft.) even though the structure had an average height of 66.4 ft. The design also only calculated the external forces near the center of the building instead of the higher pressures near the two end walls. The calculations of the designers used a slope of 11 degrees for calculating wind pressures even though the actual slope was 21 degrees. The design team classified the building as fully enclosed, but with the number of vents and door openings the facility should only have been classified as partially enclosed (Figure 2). This meant the design team gave little consideration to the internal air pressures changing along with the external ones. (Gross 2009, 83-84)

The structure was designed using an effective length factor of K=0.5 even though it should have been twice as much. Also there were unbraced members that were not consistent with the design drawings. The structure was also designed with the intent that the stretched fabric would act as lateral bracing for the frames, which it did inadequately. The joint details produced large bending moments and shear forces unconsidered in the design. The 2008 upgrades only slightly affected the structure as they only increased the compression capacity of certain members and many of the critical members received no reinforcement. (Gross 2009, 84)

With these factors taken into account the 60 m.p.h. winds of the storm caused buckling of an inner straight section of the east (leeward) roof which in turn caused a kink in the frame. The failures of the knees on both leeward and windward sides allowed the structure to sway east with the wind. The east keystone web failed in compression and led to fracture of inner and outer chords at the ridge. This spread the failures through load redistribution and reduction in bracing causing a total collapse. (Engineer's Edge)

Aftermath
Because this accident occurred to such a high profile organization, public recognition of the collapse was greater than most other collapses. Although twelve members of the team and staff were injured, all of them recovered by the season opener and the Cowboys made it all the way to the second round of the playoffs, when they lost to the Minnesota Vikings. While the team was minimally affected in the long run, structural analysis continued into January 2010 when the government released an analysis of what went wrong (See Document). The results of the study affected the construction of other similar temporary structures of the same type, such as the facilities of the New England Patriots.

Failure Prevention
The failure could have been prevented if the facility was constructed according to its true standards. Also, if the reinforcements placed in 2008 had been more strategically placed in greater numbers throughout the whole structure, not for only a few members, the collapse could have been prevented because of the greater compressive strength and lateral reinforcement. Also, if the joints had been designed for greater loads they would not hav e failed and begun the buckling.

Lessons Learned
The NSIT recommended that future construction of similar structures use lateral bracing and not rely on the fabric to be the lateral bracing for the structural frames. A new classification for structures similar to the facility is recommended so there is no gray area between “fully enclosed” and “partially enclosed” structures in the future. Also, the structural system with lateral bracing must be able to maintain its structural integrity.

Industry Changes
The industry was able to create retrofits to reinforce current structures built similarly to the Dallas Cowboys Indoor Practice Facility. As of now it is unknown if all the recommendations of NSIT will be enforced and become standard practice since the report is only two months old.

Lessons Unlearned
As of now there have been no similar collapses to the Practice Facility and it is unknown if the industry still makes the same mistakes. The publicity of the collapse and the simplicity of improvements will most likely make these issues obsolete. Cover-All, the company that built the structure, quickly went bankrupt and warned all former clients of potential code violations.

Facts:
__**Building Specifics:**__
 * The building was 204 ft by 406 ft in plan and 86 ft high
 * The building was a gable-roof frame building with a fabric-covered frame
 * The building had an outer layer and an inner layer of fabric
 * The outer layer was in tension and the inner layer was an untensioned liner
 * The structure consisted of 28 truss gable frames spaced 15 ft on center
 * There was cross-bracing for lateral support, but none in the keystone section

__**Building Facts:**__
 * Name is Dallas Cowboys Valley Ranch Training Facility
 * Constructed in Irving, TX in 2003 by Summit Structures, LLC.
 * Reinforced in 2008 with added purlins, members, and a new roof covering
 * Based off 1998 ASCE requirements
 * Collapsed mid-afternoon on May 2, 2009

__**Collapse Facts:**__
 * Collapsed in wind speeds of 55-65 mph
 * The structure began to tremble and light fixtures swayed just prior to collapse
 * The facility had 70 people inside
 * 12 people were injured

**Additional Resources**
This article is after the official investigation report was released and gives a synopsis and reaction to the report.
 * Wood, Debora. (Februrary 3,2010). //NSIT Recommends Code Changes for Fabric-Covered Steel Structure//s. Engineering News-Record.**