King+Dome+-+Roof+Performance+Failures+and+Ceiling+Collapse

King Dome - Roof Performance Failures and Ceiling Collapse //Jordan Miller, B.A.E., Pennsylvania State University 2014 // toc
 * Seattle, Washington - July 19, 1994 **

Introduction
On July 19, 1994, an hour before the Seattle Mariners were to play the Baltimore Orioles; a 4-ft. long acoustical ceiling tile fell 180 ft. from the roof of the 18-year-old Kingdome. Additional tiles fell and before long it was realized that all 40,000 fiberboard tiles must be replaced before the stadium could be used again. (1995 Mariners, 2009) As the tiles began to be pulled off the ceiling, it was quickly evident there was severe water seepage through the concrete roof system. Subsequent repair activities lasted much longer than expected, cost more than the initial construction itself, and included an accident which claimed the lives of two workers. The Kingdome was never again able to regain its good reputation and in 2000, only 24 years after it opened, the Kingdome was demolished in a controlled implosion.

Key Words
//Seattle, Kingdome, Tectum tiles, thin-shell concrete, ceiling tile failure, moisture resistance, crane collapse//

History
The first ideas and conversation about a domed stadium in Seattle arose as early as 1960 and initially had very enthusiastic local backing. (McIntosh, 2010) The city had smaller stadiums but wanted to attract a professional football team and put the city's sports in the national spotlight. Over the next decade much effort was expended to pass funding and subsequently decide on a location for the home of Seattle's sports teams. By 1967, $40 million were budgeted for the stadium as part of an over $800 million proposed overhaul of city infrastructure. However, a number of problems including rising interest rates, the Environmental Protection Act and higher citizen opposition stymied the progress of the project. Over 100 sites were considered ranging from Seattle to Tacoma and eventually the stadium's King Street location was finalized amid growing dissent, and groundbreaking was held in 1972. Over those 12 years funding initiatives fell through as the budget grew from an original estimate of $15 million to the final bid of $40 million. Arguments among political leaders and community activists muddled the city's plans for the stadium throughout the planning process, and cast the construction of a once heralded project in a negative light for most citizens. Throughout the planning process and construction phase many marches and protests were led by concerned citizens of the area surrounding the stadium site. This area was heavily populated by Asian-Americans and other nationalities, and the marches were often led by members of these social and ethnic groups, as seen in the image below.

Construction
Because of the location of the stadium in Seattle's International District, many citizen groups thought the project would cast a negative shadow on the area. Light and noise pollution, traffic, and the overwhelming size of the project were just a few of the problems activists lobbied against throughout the planning and construction phase. (McIntosh, 2010) However, the promoters of the stadium sang its praises as the most economically constructed domed, air conditioned stadium of its size in the world. The construction process had many difficulties including accidents and schedule issues. In January 1973, steel towers which were to form the core of the stadium's concrete piers fell on a worker and proceeded to knock down other towers like dominos. (McIntosh, 2010) Additionally, the primary contractor responsible for much of the dome's construction, had his contract terminated for being 300 days behind schedule and failing at 'basic performance'. To make matters worse, the project team promoted the stadium for setting economic records, something that probably contributed to cut corners in both design and implementation. The Kingdome was eventually opened on March 27, 1976; with a ceremony consisting of many civic groups ranging from various ethnic groups, military personnel, and school choirs. Many hoped that the positive use of the stadium would end the dissent lobbed toward the project for the last 16 years and help unite the city through the events held there.

Failure Components
Unbeknownst to many, the innovative Kingdome roof began to leak 3 months before the building even opened. (Nalder, 1994). The roof was composed of forty-one concrete ribs, dividing the roof like wedges of a pie. (Q-Metrcis, 2002). Between these ribs, was a roof of thin-shell concrete which was supposed to be a unique and efficient design; not often used on a structure of such monumental size. The concrete shell spanning the structure was as little as 5 inches thick at places and helped the project achieve such a low construction cost. (Boothby, 1998)

Throughout its life, the Kingdome underwent numerous repair attempts to try to stop the leaking issues. According to a report by Eric Nalder and Thomas Guillen of the Seattle Times; two major projects were undertaken during the 1980's which turned out to let in more moisture than before and had to be undone. (Nalder, 1994) These projects consisted of actually cutting slots into the roof in order to drain moisture out of the saturated materials. However, due to improper execution and covering of the slots, more moisture was let into the roof system. Nalder and Guillen chalk the Kingdome's problems up to tight budgets, bad luck, and oversights from the very beginning.

Several main issues contributed to the weak design of the Kingdome ceiling and roof. These issues consisted of: lack of moisture control, acoustical tiles not bonded to the ceiling, the dome's reverse arch sections. Some of these issues are illustrated in the image below.

One of the initial issues with the moisture control of the roof was that vapor emitted by the thousands of fans attending events moved through the entire roof until it was blocked by an impermeable outer coating. (Nalder, 1994) Because the building could neither breathe, or block the moisture on the inner-most layer; the water was soaked up by the ceiling tiles and insulation. Further adding to the roof problems was the state of the concrete itself. Major areas of severe honeycombing and cracking were found which contributed to the weakening of the concrete, reinforcement and tile fasteners. Wiss, Janney, Elstner Associates (WJE) performed close up inspections and testing of the ceiling panels and concrete dome shell. Most of this investigation was to determine the extent of voiding and consolidation deficiencies in the shell. (Wiss, Janney, Elstner Associates, Inc.) The voiding issues in the concrete shell further allowed moisture to easily travel through the concrete dome and wreak havoc on the system.

In an attempt to stop leaking in the roof in 1993, King County made an incredibly poor decision that may have further decreased the performance of the roof and added weight to the already mounting stadium financial woes. The county decided to strip the urethane foam on the roof which seemed prone to attracting moisture, but neglected to hire a single engineer for the project. The county decided to try to use a modified cement grout and silicone elastomeric coating to replace the foam; however, this product did not bond well with the roof. Additionally, the ceiling no longer had any insulation which was a direct violation of the state energy code. (Rosenbaum, 1995) Because the removal process was taking long, the crews switched to pressure washing the roof. This procedure was being carried out at the time the roof tiles fell.

This action highlighted a major rift within the management and oversight of the stadium. The stadium facilities manager oversaw everything in the interior of the structure, while the facilities manager for the county was responsible for the exterior. (Rosenbaum, 1995) The stadium manager complained profusely to the county about the pressure washing, but to no avail. However, at this point in the life of the building, the pressure washing probably did not make much of a difference. Despite the pressure washing likely not causing much damage, King County was able to prove in court that this was one of the causes and received $6.8 million from the general contractor. (ENR, 1996)

The Tectum tiles used for the ceiling were bonded straight to the concrete using metal clips with a felt backing between the tile and the concrete. The felt, coupled with the omission of sealant on the seams between tiles, allowed moisture to soak between the tiles and the concrete and loosened the tiles from the clips supporting them. (Nalder, 1994) According to the investigation performed by WJE; the tiles were capable of absorbing water up to 92% of its own weight. The investigators also found a loss of strength up to 75% of the original design. (Daniels, 1994) It was thought by some that maintenance and cleaning procedures happening to the exterior of the concrete roof at the time of collapse were to blame for the failure; but Robert LaFraugh, Seattle branch manager for WJE said this was not true as WJE had found bigger problems with the roof during investigations. (Daniels, 1994)

Because of the reverse arch action of the concrete shell roof, a very efficient and minimal design was achieved which allowed the roof to span great lengths without much thickness. However, this left the ceiling tiles bowed around the outside of the curve which led to spaces forming between the tiles. Instead of having the tile edges pushed together like they would be on the inside of a curve, these spaces continued to grow with time and left room for moisture to seep into the concrete shell. (Nalder, 1994) While this was not necessarily a mistake, it was a negative consequence of the chosen design.

Eventually all 40,000 ceiling tiles were removed and a project team was tasked with designing a replacement system. The figure below shows the cranes used to remove the old ceiling tiles.

Repair Accident
In 1994, after ceiling tiles fell from the dome before a Seattle Mariners baseball game, two workers sandblasting the ceiling with a hose were killed when they fell from the crane bucket they were in, more than 250 feet above the ground. (ENR, 1994) The crane basket struck the ceiling of the Kingdome, causing the boom to collapse onto the cab of the crane also seriously injuring the operator. (AP, 1995) According to the investigation report, the radio in the cab used to communicate with the workers in the basket was found to be turned off (ENR, 1994(2)) Subsequent investigations found the crane contractors were in violation of 14 'serious' safety and health regulations, and fines totaling almost $40,000 were levied against the contractors. (Rosenbaum, 1995)

Repair Strategy and Costs
On February 15, 1995, repair crews completed the final leak test on the new roof system which included over 700,000 new holes for mechanical fasteners securing the roofing material. (Rosenbaum, 1995) Officials assured the public that the new multi-layer system was the best to minimize interior heat loss, ensure fire safety and deter seagulls which had severely damaged the previous system. (Rosenbaum, 1995) In fact, seagulls had damaged the previous roof exterior so much that enough dirt and moisture were collecting in the roof to enable small trees and plants to grow. The new system consisted of an asphalt layer to fill in holes in the concrete roof, an asphalt vapor barrier, a layer of rigid fiberglass insulation plus two layers of polyisocyanurate insulation, siliconized gypsum panels, and a weather-tight polyvinylchloride membrane. (Rosenbaum, 1995) The interior ceiling tiles were replaced with a spray on insulation which does not require fasteners and can resist condensation damage. (Q-Metrics, 2002) The total repair cost of the Kingdome roof cost $70 million which was more than the original construction cost itself. Due to financial woes and continued performance issues, the Kingdome was imploded in 2000, and the taxpayers of King County still owed $26 million on the facility. (Brown, 2010) Thousands of the city's citizens were on hand to watch the implosion which signifies the Kingdome had a major impact on Seattle whether for good or bad.

Lessons Learned
I think there are numerous lessons to be learned from the Kingdome and its monumental failures. Most of the takeaways from this case study for me deal with the problems of cutting corners, unclear communication, beauracractic discrepencies, and not truly understanding the design. King County wanted to severely limit the budget and still have a monumental stadium that would be world famous and draw thousands of people. From my point of view these two ideals do not work together. It is one thing to cost-cut extravagant components such as large TV screens or plush luxury boxes; but to skimp on the bare necesseties a building needs to function is not acceptable. From my point of view it appears the cost cutting measures were partly because of politics but also in response to citizen outrage. The issue of communication was apparent in my research, especially in the area of building maintenance. Having two seperate entities governing the oversight of the exterior and interior of the buildings seems like a recipe for disaster and definitely contributed to the Kingdome failures. Additionally, it seems that in the early phases of planning and design, communication issues played a part in achieving the proper detailing and execution of the roof and ceiling system. Beauracratic discrepencies jumped into view for me when I read about the county doing projects on the roof without hiring an engineer or consulting code officials. It seems that the county wanted to get things done quickly and without the public knowing about it so they approved maintenance projects that were not helpful for the building. A much better way to go about things would have been to get a team of engineers, officials, and stadium management to devise a solution that would fix the problems once and for all. Lastly, it seemed as if the designers and contractors did not truly understand how their system would function in a real-life situation. I believe that if someone had taken the time to really think through the system either during the intitial design phase or the construction; they would have realized where some of the weak points were and what could be done to fix them. However, it does seem that the stringent financial and time constraints on the project inhibited this type of behavior from happening.

Conclusion
I believe a quote from Kingdome repairs Project Director E.D. Cohen sums up the structure and it's woes appropriately. "I'll never be so happy as the day I walk off this job. I'm not bitter, but the politics made it miserable." (Rosenbaum, 1995) I believe that the Kingdome did have a place in the hearts of Seattle citizens despite it's many shortcomings. Stadiums, whether for sports, music or other events; are a venue for people to go and simply enjoy themselves. Entertainment is held very high in our culture, and the structures we view entertainment in are part of the experience. Unfortunately, politics, finances, design failures and poor construction practices marred what could have been one of the great structures of its era.