SLIDE 1 FEDERAL EMERGENCY MANAGEMENT AGENCY MITIGATION DIRECTORATE BUILDING PERFORMANCE ASSESSMENT TEAM OKLAHOMA AND KANSAS Midwest Tornadoes of May 3, 1999 OBSERVATIONS, RECOMMENDATIONS, AND TECHNICAL GUIDANCE SLIDE 2 FEMA Building Performance Assessment Teams Team Members .Representatives of public and private sectors and expertise in: .structural and wind engineering .building design and construction .code development and enforcement .meteorology SLIDE 3 FEMA Building Performance Assessment Teams Team Objectives .Inspect damage to buildings .Assessment performance of buildings .Evaluate design and construction practices .Evaluate code requirements and enforcement .Make recommendations as necessary SLIDE 4 The BPAT Damage Assessment Table SLIDE 5 Illustration of the potential impact of a tornado. SLIDE 6 Potential damage table for impact from a tornado SLIDE 7 Background Oklahoma / Kansas affected .May 3, 1999 .Tornado warnings issued by NWS .70 tornadoes affected both states .4 violent (F4 or F5) tornadoes SLIDE 8 Observations .Residential Building Types Inspected - single and multi-family, one-to two-story - manufactured and modular homes - accessory structures .Non-Residential Building Types Inspected - tilt-up pre-cast concrete with steel joists - load-bearing masonry walls with steel joist and pre-cast concrete hollow-core floor - pre-engineered buildings SLIDE 9 Illustration showing that a building failure is the result of inward wind forces and uplift wind forces acting on a building during a high wind event. SLIDE 10 Photo: Wind uplift acting on this house in Haysville, Kansas, resulted in this corner of the building being lifted off its foundation. SLIDE 11 Photo: This unreinforced masonry (URM) wall failed when inflow winds from a strong tornado acted on this building in Wichita, Kansas. SLIDE 12 Observations Windborne Debris .debris can breach the building envelope that results in overpressurization of the building .debris can cause human injury to individuals who are not in a safe shelter .missiles often completely covered the ground .in many houses, the floors were covered with small tree branches and fragments of broken framing members SLIDE 13 Windborne debris (missiles) and rolling debris classifications. Small missile: typical debris of aggregate roof surfacing, pieces of trees, pieces of wood framing members, bricks; associated damage observed was broken windows, doors, and other glazing, some light roof covering damage Medium missile: typical debris of appliances, HVAC units, long wood framing members, steel deck, trash containers, furniture; associated damage observed was considerable damage to walls, roof coverings, and roof structures Large missile: typical debris of structural columns, beams, joists, roof trusses, large tanks, automobiles, trees; associated damage observed was damage to wall and roof framing members and structural systems SLIDE 14 Photo: these medium sized missiles struck and remained embedded within this manufactured home in Wichita, Kansas. SLIDE 15 Photo: A 2-inch by 6-inch missile penetrating a refrigerator located inside a home in the Country Place subdivision outside Oklahoma City, Oklahoma. SLIDE 16 Photo: Wood framing members and plywood sheathing near the periphery of a violent tornado damage area in Moore, Oklahoma, displaying quantity of flying debris. SLIDE 17 Observations - Residential .Roof and Wall Sheathing .Structural Connections .Exterior Wall Coverings .Garage Doors .Windows and Doors .Masonry Veneer / Chimneys .Manufactured Housing SLIDE 18 Illustration: Platform construction typically observed during the field investigation. It shows typical continuous load paths from roof system to foundation, and typical building connections requiring hurricane clips or straps to create a continuous load path. SLIDE 19 Photo: Failure of base of wall between wall studs and bottom plate. The bottom plate, which was connected to the foundation slab with anchor bolts and nails, has splintered. SLIDE 20 Photo: This double-width garage door failed under a suction load in Moore, Oklahoma. SLIDE 21 Photo: Failure at masonry veneer wall at a home located along the periphery of a violet tornado near Moore, Oklahoma. SLIDE 22 Photo: Failure of brick chimney onto top of home located along the periphery of a violent tornado, More, Oklahoma. SLIDE 23 Photo: Lack of bolts or positive connectors present between the chassis and foundation of a double-wide manufactured house. Haysville, Kansas. The floor framing of the house was still resting on the foundation after the tornado passed. SLIDE 24 Observations -Non-Residential .Continuous Load Path .Increased Load .Building Envelope SLIDE 25 Illustration of critical connections that failed in the load path, resulting in structural damage or collapse. SLIDE 26 Photo: Tilt-up precast concrete walls at a storage building located outside Del City, Oklahoma. After the roof joists separated from the wall, this end wall became unable to withstand suction forces and failed. SLIDE 27 Photo: Metal roof deck (missing in photo) of regional outlet mall, Stroud, Oklahoma, was blown off when hit by a strong tornado vertex. SLIDE 28 Photo: This metal-clad wall covering collapsed and in other areas it was blown completely away. SLIDE 29 Observations -Personal Protection and Sheltering .Type of Shelters .Use of Shelters .Maintenance and Design Issues .Shelter Accessibility .Shelter Location .General Observations SLIDE 30 Photo: Aboveground in-residence shelter hit by strong inflow winds near the vortex of a violent tornado in Del City, Oklahoma. Arrows indicate the extent of this reinforced concrete shelter that cannot be seen due to the brick veneer. SLIDE 31 Photo: Aboveground in-residence shelters under construction in Wichita, Kansas. SLIDE 32 Photo: Entrance to the plastics manufacturing plant group shelter in Haysville, Kansas SLIDE 33 Photo: Group shelters at a manufactured home rental community in Wichita, Kansas. SLIDE 34 Photo: Remains of an interior room (or core) of a home in a Moore, Oklahoma, subdivision that was hit by a violent tornado. SLIDE 35 Photo: A 10-foot long 2-inch by 6-inch missile penetrated the exterior wall of an apartment in this multi-family house, which was sheathed with hardboard panels. The missile, which was generated from the vortex of a strong tornado, then penetrated the gypsum board and plastic tile tub enclosure, the tempered glass shower door, and the interior partition near the door frame. At the interior partition, it pierced through a stud and projected a few inches into the hallway. SLIDE 36 Photo: Northmoor Elementary place of refuge, Moor, Oklahoma, corridor with clerestory windows. This corridor offers little protection from tornadoes as shown in a school of similar design. SLIDE 37 Photo: Kelly elementary School, Moore, Oklahoma, place of refuge, corridor with clerestory windows. These interior corridor walls had brick masonry up to a height f approximately 7 feet. Glass extended from the top of the brick masonry to the top of the wall. SLIDE 38 Conclusions .Residential Property Protection .Non-Residential Property Protection SLIDE 39 Conclusions Building Codes .local codes do not incorporate wind speed design parameters used by 1997 UBC, 1997 SBC, 1996 NBC and ASCE-7-98 .constructing homes to these standards would improve the strength of these structures SLIDE 40 Conclusions -Single and Multi-Family Homes Load Path and Structural Systems .Foundations performed adequately .Where failures were observed, the deficiency was the connection of the structural systems to the foundation SLIDE 41 Conclusions -Single and Multi-Family Homes Increased Load -Breach of Envelope .internal pressurization is a major contributor to poor building performance .many building failures were caused by a breach in the building envelope .garage door failure a primary cause of building envelope breach SLIDE 42 Conclusions -Manufactured Housing .Manufactured housing did not resist wind forces as well as single-family homes .inadequate fastening of roof to wall systems .inadequate resistance to uplift and overturning provided by tie-downs SLIDE 43 Illustration of a proper connection of a manufactured home to a dry stacked CMU foundation using straps only; L-clips are not illustrated here. SLIDE 44 Conclusions -Non-Residential Structures Non-residential structures were as vulnerable to damage, but received less damage than residential structures .Primarily due to engineering required by model building codes SLIDE 45 Conclusions -Non-Residential Structures Failure modes similar to residential structures .lack of attention to uplift and lateral loads .no continuous load path .breach of building envelope .failure of commercial rollup doors SLIDE 46 Conclusions -Residential Shelters Observed Problems: .lightweight doors and hardware .poor maintenance .unprotected ventilators SLIDE 47 Recommendations General recommendations for the rebuilding effort .design buildings to the most current codes and engineering standards .provide safe refuge by constructing engineered shelters SLIDE 48 Illustration of a typical double-wide garage door elevation. SLIDE 49 Recommendations Manufactured Housing .HUD should review its standards and enforcement program .Consider permanently connecting the manufactured home to its foundation SLIDE 50 Recommendations .Non-Residential Buildings .Threaded fasteners to attach metal decking .Essential facilities should not use aggregate and paver roof surfacing .Enhanced wind design for roof coverings SLIDE 51 Recommendations Non-Residential Buildings .Brick veneer walls system should be designed as “stand alone” .Masonry chimney design should change .Design guidelines for installation of laminated glass in essential facilities SLIDE 52 Illustration showing that the proper connections in a reinforced masonry wall provide a continuous load path. It shows the connection of the CMU wall to roof structure and the CMU wall to the foundation. SLIDE 53 Photo: Covers of FEMA 320, Taking Shelter from the Storm, and the National Performance Criteria for Tornado Shelters.