Data Collection - STD-102020020062

DOE-STD-1020-2002

II, which is a detailed evaluation. The Level II process is described below. The steps

include:

(a)

Data collection

(b)

Analysis of element failures

(c)

Postulation of failure sequence

(d)

Comparison of postulated performance with performance goals

3.3.1

Data Collection

Construction or fabrication drawings and specifications are needed to make an evaluation

of potential performance in high winds. A site visit and walkdown is usually required to

verify that the SSCs are built according to plans and specifications. Modifications not shown

on the drawings or deteriorations should be noted.

Material properties are required for the analyses. Accurate determination of material

properties may be the most challenging part of the evaluation process. Median values of

material properties should be obtained. This will allow an estimate of the degree of

conservatism in the design, if other than median values were used in the original design.

3.3.2

Analysis of Element Failures

After determining the as-is condition and the material properties, various element failures

of the SSCs are postulated. Nominal strength to just resist the assumed element failure is

calculated. Since the nominal strength is at least equal to the controlling load combination,

the wind load to cause the postulated failure can be calculated. Knowing the wind load, the

wind speed to produce the wind load is determined using the procedures of ASCE 7 and

working backwards. Wind speeds to cause all plausible failure modes are calculated and

tabulated. The weakest link is determined from the tabulation of element failures. These are

then used in the next step to determine the failure sequence.

3.3.3

Postulation of Failure Sequence

Failure caused by wind is a progressive process, initiating with an element failure.

Examples are failure of a roof to wall connection, inward or outward collapse of an overhead

door, window glass broken by flying roof gravel. Once the initial element failure occurs at

the lowest calculated wind speed, the next event in the failure sequence can be anticipated.

For example, if a door fails, internal pressure inside the building will increase causing larger

outward acting pressures on the roof. The higher pressures could then lead to roof uplift

creating a hole in the roof itself. With the door opening and roof hole, wind could rapidly

circulate through the structure causing collapse of partition walls, damage to ceilings or

ventilation systems or transportation of small objects or debris in the form of windborne

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