2.1 STUDY METHODOLOGY
In order to assess the damage in Greensburg, two site visits were conducted (May 10-11 and May 21). The observations made during the site visits were used for two purposes. First, the observed damage for 46 residential structures was used to rate the damage according to the EF Scale and thereby derive estimated wind speeds (see Section 3.1). The estimated wind speeds were then mapped (Section 3.3). In addition to these 46 residential structures, additional DOD assessments were made in the field; these assessments included damage to seven non-residential structures and trees in the tornado path.
Second, specific damage information was collected at four sites to perform structural analysis and evaluate the failure stresses in the materials. These buildings were selected where all or a portion of a building was damaged or destroyed, where the damage had not been disturbed, and where, in the Study Team's opinion, there was a possibility of back-calculating the pressures causing the failures to determine the approximate wind speed. Detailed information was collected for: the elementary school pre-engineered metal building (PEMB), the John Deere PEMB, the precast concrete tee roof failure at the hospital, and the glulam beam failures in the First United Methodist Church. After performing a materials analysis to calculate the wind speeds required to cause the observed failures (Section 3.2), the calculated wind speeds were mapped and compared to the wind speeds derived from the EF Scale assessment (Section 3.3).
2.2 FIELD OBSERVATIONS
- 1. The primary site observations were obtained from an initial study of overhead imagery and initial site inspections conducted on May 10-11, 2007:
- a. The most severe swath of damage through the center of town was approximately five to six blocks wide. The damage on either side of this swath was less for about one to two blocks on each side, with even less damage observed for another one to two blocks on the extreme outer edges of the damage swath. See Figure 1 for an aerial view of Greensburg after the event and Figure 8 for a map of the damage swath.
- b. Many of the residential buildings were observed to have basements and some of these buildings were shifted on their basement foundations.
- c. The roofs of many of the buildings located near the edge of the storm's center and along the storm's path had roof coverings that either completely or partially survived the tornadic winds.
- d. Most residential and commercial buildings in town were older than any of the model building codes. Exceptions were the John Deere Building built in the mid-1990s and the elementary school PEMB erected in 2002 (see Figure 8 for locations). The residential and commercial buildings observed during the site visit did not have any specific design features that would have been intended to protect building occupants from the effects of this tornado except for basements or below ground areas and any small interior room, such as a closet or bathroom, used as a best available refuge area. No "tornado shelters" designed to resist the wind and debris associated with a tornado were identified during this effort.
2025-FEFO-00594-000008
