Jie Li, Ph.D.
Distinguished Professor, Tongji University
“For the development of the probability density evolution methods and contributions to seismic reliability based design of large scale civil infrastructure systems”
Thanks a lot, everyone, ladies and gentlemen.
When I walked around the campus of Chongqing University in 1982, I never imaged that one of the winners of Freudenthal medal would be me. On this special occasion, I would like to express my sincere thanks to the award community of ASCE, and I would like to express my sincere thanks to all of my friends in the world, my colleagues in Tongji University, my great associates and students in my group, and of course may be the same important of my life, my wife- Min Xie, there, please. Without their helps and supports, I would not stand here.
On this special occasion, I would like to beg you a pardon for giving me some time to say a story, a little bit story about myself. As I mentioned, you know, I start my academic career in Chongqing University, which locates in the south-west part of China and it is a very beautiful mountain city. In that time, I pursued master degree under the supervision of Professor Dezhong Ding, who graduated from Cornell University in 1930s. I still remember that in autumn 1983, one day afternoon Prof. Ding knocked at the door of my dormitory and said to me “please come to check your beam, may be some wrong in your tested beam.” Since in that time, you know, my professor seldom came to my room, so I rushed very quickly to the lab and checked very details of my tested beams. Finally I found one error- a little error on the tested beam: The designed space of stirrup is 5 centimeters but the real is 7. That was a very little error. I corrected the error and thought the experiment must be very successful. Really, after three months, I got very successful experimental results. But from here – a natural result, I met a very huge problem. That means if I used an identified parameter for every beams, I could get very little errors between the experimental results and theoretical results. But if I wanted to get a set of unifiedparameters for all the tested beams, the error would increase quilt large. So I knew I met a problem firstly, that was just the randomness.
From then to now, the randomness has spoiled my life: What is the randomness? Where is the resource of randomness? It really exists a stochastic rule？ These problems always occupied my mind in my life. It was only ten years later, when I involved in the stochastic modeling of structures under the supervision of Professor Roberts in Sussex University, I first realized that the physical relationship is the basis for the stochastic schemes, which was the first step that we got the PDEM eight years later.
In my opinion, you know, we are living in a world full of uncertainties. Most of people like to use deterministic models to simulate the reality. But some other people think there are two worlds: deterministic world and stochastic world. In my opinion, most important things is, what is the bridge connecting these two worlds. The PDEM could answer the question. Actually, the randomness does not change the physical rule, so the probabilistic structures of a stochastic system will be governed by the physical mechanism of the system. I think this is a new idea about our living world.
In 1994, when I was living in England, I had a talk with Prof. Roberts. In that time I was very excited in our new advancement of stochastic modeling of systems. However, Prof. Roberts told me ‘It is only a start’. From then to now, the words always appear in my mind. Really, it is only a start. With your help and your interesting, I believe, the PDEM could be used in a broader of area. I hope so
Thanks a lot. Thank you.