Page 14 - CEGE Magazine Spring 2017

A Paradigm-changing Framework for Reliability-Based Analysis and
Design of Concrete Structures: Jia-Liang Le
No engineering structure lion (108) times, and 2) Design The structure’s peak load
remains risk-free during its entire service lifetime. Engi- neers must design structures
to limit probable risk of failure to a toler- able level. Because many of the factors affecting the risk of failure cannot be known precisely, probabilistic methods have become an indispensable tool for structural design.
For concrete infrastructure (for example, buildings, bridges, dams) the accept- able risk of failure is typically one in one million, or even lower. Ensuring such a low risk poses two unique challenges when designing and analyzing concrete structures: 1) Determining such a low probability of structural failure would require repeating experiments or numer- ical simulations at least one hundred mil-
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extrapolation is required because, in many cases, the actual structures are much larger than laboratory test specimens. Motivated by these challenges, Professor Jia-Liang Le has focused
his research on intertwining
fracture mechanics, damage mechanics, and probabilistic methods to develop a framework for reliability-based structural design and analysis of concrete structures.
Le and his research team recently developed a finite weakest-link model to analyze strength statistics of concrete structures. The underlying concept of the weakest-link model is that a structure is only as strong as its weakest element.
capacity is reached if one material element is fully damaged. Therefore, a structure can be statistically modeled using a “chain”
of material elements. The established practice is to use an infinite weakest-link model, which assumes that there are an infinite number
of material elements in this chain. In contrast, the new finite weakest-link model acknowledges that in concrete structures, material elements have a finite size, and that size may not be negligible compared to the characteristic dimen- sions of the structure.
By explicitly introducing the size of a failing material element, the finite