February 2, 2006, 2:00 – 3:00 p.m., Holmes Hall 244
Leiming Zhang, Associate Professor, Deparment of Civil Engineering, Shanghai Jiaotong University

Network of Energy Flow in Framed Structures and its Preliminary Application

Nowadays full-process analysis of structures under disastrous loadings, such as strong ground shaking and blast, starting from linear elastic to plastic stage, even further to collapse, becomes more and more important. Its aim is to find out how to prevent collapsing in order to save lives. Unfortunately, there are several difficulties that need intensive further research.
Another way to save life in case of collapse is to indicate what elements of structures are most probably subjected to failure when an extreme loading shocks, and to set alarm in advance based on monitoring these members. It is also helpful if the importance of elements of a structure can be classified and more attention is put on the highly important members in different life stages of the structure.
Obviously a structure might suffer different failures subjected to different loadings. In order to consider the influence of loadings, from an energy point of view is a good idea to carry out such kind of analysis. The first trial is made on framed structures.
Based on the energy flow in framed structures under various loading conditions, a network of energy flow is constructed considering the energy passing through structural members and joints. By graph theory, the key path of energy flow in framed structures, namely the most important loading-carrying path, is determined in accordance with the energy flowing in/out members/joints. By comparing the change of the strain energy stored in the structure with different members removed, the index of member importance is introduced. Then by tracing the change of the index of member importance due to failures of members, the most important failure mode is determined.
A three-story frame collapsed in Tangshan Earthquake is analyzed, which shows the procedure presented is effective to determine the index of member importance, the most important load-carrying path as well as the most important failure mode, with full consideration of different loading conditions.
Future investigations might be focused on rank structural members according to their effects on the energy flow network, under dynamic loading.

Keywords: Network of energy flow, Importance of member, most important load-carrying path, most important failure mode