Page 399 - Forensic Structural Engineering Handbook

11.30 MATERIAL-SPECIFIC FORENSIC ANALYSES

Purlin Edge
beam
15' 15'
Post
30' 30'
Negligible
brace
Top
Assumed
No brace brace chord
Out of plane
component Buckling Axis of Buckling
shape
of load
Load In plane intermediate shape
diagonal
component
of load Intermediate
diagonal
FIGURE 11.12 Lateral support connection of top chord at mid-length.

FIGURE 11.13 Collapsed roof.

backing bar thickness and any lack of fusion (LOF) at the weld root. The stress intensity
for this condition can be estimated as

K ≅ . 112σπ a (11.15)
max
where a = b + LOF (backing bar thickness + LOF), and is the sum of the dead load stress,
b
residual tensile stress, and live load stress in the beam flange.
The available test data have demonstrated that brittle weld metal is likely when E70T-4
flux core welds exist. The resistance to fracture for the groove weld shown in Fig. 11.14 is
not much different from the base metal in the core of heavy W shapes that do not satisfy
the supplemental CVN notch toughness in the core region. When low-toughness base metal
or weld metal is used, careful attention will be required to assess notch conditions (flame-
cut edges), crack-like geometric details and lack of fusion, and the role that residual stresses