Blast Resistant Design
Full Session with Abstracts
338132-5 - Brittle Failure in Blast-Resistant Structural Design
Saturday, April 21
10:00 AM - 11:30 AM
Theories of structural failure begin with an assumption that the mode of failure is either ductile or brittle. For ductile failure, significant material elongation occurs prior to fracture. For brittle failure, the material’s stress state and the existence of cracks within it combine to cause fracture prior the material elongating significantly. It is a matter of engineering judgment, prior to analysis, which theory is applicable to the design problem at hand.
For blast-resistant structural design, ductile failure is the typical assumption. The component of interest is resolved into a single-degree-of-freedom (SDOF) spring-mass element, its peak response is calculated and that response is compared to published response limits. This approach implicitly assumes that no elements (bolts, welds, heat-affected zone, sectional material, etc.) represented by the SDOF abstraction exhibit brittle mode of failure.
Preventing brittle failure in the elements that compose the SDOF component can require exacting control over fabrication and erection of the component. This fact is illustrated using a case study of brittle failure of a pressure vessel. An accident investigation identified the causal factors from manufacture and fabrication of the vessel that resulted in the vessel’s brittle failure at an internal pressure much less than the maximum operating pressure.
In this present paper, the causal factors for the vessel’s failure are summarized and applied to fabrication and erection in the context of blast-resistant structural design. The paper will provide new information regarding: (1) how fabrication and erection techniques can introduce a brittle failure mode in a structure; (2) fabrication and erection considerations for minimizing the possibility of brittle failure; and (3) recommendations for future testing to understand the importance of brittle failure mode to blast-resistant structures.