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Metrodome Roof CollapseDecember 12, 2010
Steven C. Maki, PE
Director of Facilities & Engineering
MSFC
Metrodome Roof Operation & Care
Monitoring 24/7 basis
Experienced staff
Annual inspection and repair
Periodic roof surveys as recommended by Birdair
Birdair Roof Surveys
Conducted in 2003, 2007, & 2010
2010 survey indicated fabric in good condition
Metrodome Snow/Wind Incidences
3 snow collapses early 1980s with one panel replacement
1 wind incident 1986
No collapse or panel replacement in 27 years
Snow Procedures
Preheat interior to 80-85 deg F air temperature
Hot air (150F) is directed between outer and inner to melt snow
Internal pressure increased by 50%
Manual snow removal if necessary
This procedure worked for 27 years
December 10, 2010
Winter storm warning with projected heavy snow
Typical snow procedure is begun
December 11, 2010
Overnight heavy snow/strong winds
Leo Pidde calls for manual snow removal 10:15am
Steve Maki on roof at 11am
Pressure is raised higher late morning
7 personnel on roof by 1pm
December 11, 2010continued
Significant snow accumulations on roof/strong winds
Inverted triangular panels (tips) North/West sides
Decreasing temperatures
Conditions deteriorate; manual snow removal not effective
December 11, 2010continued
Snow removal crew down at 5:30 pm unsafe conditions
Steve Maki/Leo Pidde pull drain plugs
All personnel off roof 6pm with plans to return next day 8am
Conference call made to postpone game
December 12, 2010
Roof collapse at 5:03am
(play video) This is precursor to FOX video
Staff arrives to begin mitigation
Conference call with MN Vikings/NFL to cancel game.
Initial Damage from Collapse
Panel 104 (triangle) ruptures from snow slide
Panels 43 & 44 (diamonds) rupture sequentially from snow loads as tons of snow and ice funnel to roof center
Panel 15 ruptures spontaneously about 5:30 pm on 12/15
Panel 35 ruptures after attempting to induce drainage 12/20
Other Collateral Damage
Frozen pipes and broken seats
Minor structural damage to wind girt system
Damaged roof vents, lightning rods, inner liner
Other misc damage
12/12/2010 HHH Metrodome
View towards panel 76
12/12/2010 Internal View of Ruptured Diamonds
Approx. 9am view from Section 136 area
12/12/2010 Panel No. 104
View from interior
12/12/2010 View of Roof from Panel No. 104
Roof Stabilization EffortsDecember 12-26, 2010
Significant snow loads/stresses on roof
Safety is no. 1 priority
Low outside temperatures hamper progress
Birdair, Geiger, WPM contacted and to site
Arrangements made with local firms to assist
Roof Stabilization Effortscontinued
Initial focus is on repair
Birdair determines panel 104 is severely damaged and can not be temporarily repaired 12/14
MN Vikings game on 12/20 is switched to U of MN TCF Bank Stadium
Roof Stabilization Effortscontinued
Ruptured panels are curtained or temporarily covered
Panel 15 ruptures suddenly 12/15
Work is stopped, work plan is reviewed for safety
Geiger designs roof restraint system using jersey barriers Birdair/Sowles installs system to ballast for wind loads
Roof Stabilization Effortscontinued
Inner temperatures rise after curtain/covering
Panel drain plugs are pulled
Laser survey is used by WPM to acertain loading/damage
Roof structure is stabilized by Christmas
Roof AssessmentDec. 26, 2010-Jan. 14,2011
Warm weather with rain
Photo survey of roof inner liner conducted; diamond panel liner removed (Geiger recommendation)
WPM recommends fabric samples to be tested
Strong winds New Years Eve tears panel 104 curtain
Sampling starts; cold/snow/winds slow efforts
Roof AssessmentDec. 26, 2010-Jan. 14,2011
Seating reduction curtain removed (Geiger recommendation)
Birdair notes panel no. 100 in bad condition
MSFC requests Birdair perform roof survey
Roof AssessmentJan. 15, 2011 +
Birdair roof inspectors arrive on site Jan. 18
Weather conditions hamper survey
Test results both bad and good
TT requests certain samples
Birdair reports roof panels in poor shape, tears/holes in triangles; survey completed 2/3
Summary of Results to Date
5 panels ruptured with significant damage to remaining roof and liner
Testing results are good and bad
Birdair survey indicates roof in poor condition
Sliding snow/ice have degraded fabric; wind/wicking are negative effects
Public Safety Concerns
No support for partial restoration of the roof
Significant concern if partial restoration, weakened fabric could fail during event causing panic
Conclusions/Recommendations
Replace external roof fabric (cables are ok)
Replace inner liner above seating area (triangles/rectangles)
Save liner cost on diamonds by replacing with acoustical batt + increase heat transfer for snow melting
Conclusions/Recommendationscontinued
New roof clamping required; remainder of roof system is good
Minor collateral damage cost wise
Remove seating reduction curtain
Syracuse experience provides positive results