2014 Freudenthal奖获奖词

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”

李杰先生获奖感言

(原文) 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.

(译文) 女士们、先生们，非常感谢大家。 1982年，当我徜徉在重庆大学校园时，我从来没有想过今天会成为Freudenthal奖的得主。在这个特殊的场合，我要向美国土木工程师协会的奖励委员会表达我诚挚的谢意。同时，我要真诚地感谢我在世界各地的朋友们、同济大学的同事、课题组的助手和学生。当然，还要特别感谢与我生命同等重要的、我的妻子谢闽女士。没有他们的帮助与支持，我就不会站在这里。 在这个特殊的场合，请允许给我一点时间向大家讲一段故事，一段关于我自己的故事。诚如我刚才提到的，我的学术生涯是从重庆大学开始的。重庆大学位于中国西南部，是一座以山城闻名的城市。当时，我跟随我的导师丁得忠先生攻读硕士学位。丁先生在上世纪30年代毕业于美国康乃尔大学(Cornell University)。我依然记得，1983年秋天的一天下午，丁先生专程来到我的寝室告诉我：“请去检查一下你的试验梁，可能有问题”。你知道，在当时先生是很少到学生宿舍来的。所以我很快奔入试验室、仔细检查每一个细节。最终，我发现了一个失误（这个在今天的试验中被认为是可以忽略的误差）：某两根箍筋的设计间距是5cm，而实际间距是7cm。尽管是可以忽略的误差，但我还是仔细修正了这个失误，当时我想，我的试验必然会成功。的确，三个月后我获得了非常好的试验结果。然而，从这样一个试验、一个非常普通的试验，我却碰到了很大的问题：如果我对每一个梁分别采用识别的参数，试验与理论分析之间的误差会非常小；但如果对所有梁采用同一组参数，误差将会变得相当大。我知道，我第一次遇到了真正的问题：随机性。 从那时到现在，随机性已经打乱了我的生活：什么是随机性？随机性的本源是什么？真的存在统计规律吗？这些问题总是占据我的头脑和我的生活。直到十年之后，我到英国Sussex大学在Roberts教授指导下从事结构系统随机建模研究时，我才开始意识到物理关系是随机系统的基础，这成为八年后我们提出概率密度演化方法的关键一步。 您知道，我们生活在一个充满不确定性的世界里。大多数人习惯于采用确定性方法反映客观世界，也有一部分人认为存在两个不同的世界：确定性的世界和随机的世界。在我的观念中，重要的是：联系两个世界的桥梁是什么？概率密度演化理论能够回答这个问题。事实上，随机性不会改变物理规律，因此，随机系统的概率结构将受控于系统的物理机制。我想这是对关于我们生活着的世界的一个新认识。 1994年，当我在英格兰访学时，我与Roberts教授有过一次谈话。当时，我对我们在随机系统建模方面的新进展非常痴迷。但Roberts教授告诉我：“这仅仅只是开始”。直到现在，这句话还时常在我脑海中萦绕。是的，这仅仅只是一个开始。在您的关心和帮助下，我相信，概率密度演化理论将会被应用到更为广阔的领域。我希望这样。 非常感谢，谢谢大家！