Page 16 - CEGE Magazine Spring 2017

Le Receives 2017 EMI Leonardo da Vinci Award
JIA-LIANG LE CONT...
equations for such a size effect by using asymptotic analysis.
Case Study
As a case study, Le and his team recently applied the finite weakest-link model
to re-analyze the failure of the ill-fated Malpasset Dam (Figure 3). The dam was built across the canyon of the Reyran Valley in France in 1954, and it failed in 1959 the first time the reservoir was filled to capacity (after 5 days of heavy rain).
It was generally accepted that the failure was due to the development of vertical flexural cracks engendered by the lateral displacement of the abutment. In their re-analysis, Le and his students used a
simplified 2D arch model to represent the mid-height cross-section of the dam. To study the size effect on structural reliabil- ity, they considered a set of geometrically similar arches (Figure 4), the smallest size being a laboratory test specimen and the largest size being the actual Malpasset Dam. The analysis indicated that direct extrapolation of laboratory-scale test results to full-scale design without the consideration of size effect would result in a failure risk 1000 time greater than the tolerable level (Figure 5). To ensure
a prescribed failure risk for structures of different sizes and geometries, design- ers must consider size effect on safety factors.
Figure 3. Malpasset Dam Failure
Existing design approaches assume safety factor to be a constant, regardless of structure size and geometry. The new finite weakest-link model could poten- tially lead to a paradigm change in design practices.
Figure 4. Size effect analysis of a set of geometrically similar arches.
Figure 5. Direct extrapolation of laboratory tests to full scale design will result in a significant increase in failure risk of the actual structure.
Associate Professor Jia-Liang Le has been selected as the recipient of the 2017 EMI Leonardo da Vinci Award. The Engineering Mechanics Institute (EMI) of the American Society for Engineering presents this award to recognize outstanding young investigators (under 35 years of age) for promising ground-breaking developments in the field of Engineering Mechanics and Mechanical Sciences as relevant to Civil Engineering.
The overarching goal of Le’s research is to improve the resilience of civil engineering structures through advancing
the fundamental understanding of probabilistic failure of quasibrittle materials. Le’s expertise uniquely centers at the intersection of fracture mechanics, probabilistic methods, and computational mechanics, which has led to several important results that represent a new paradigm of the analysis and design of structures. The award will be presented at the EMI 2017 Conference in June.
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