Recent progress in the plastic methods of structural analysis

The techniques described in Part I of this paper for the calculation of plastic failure loads under proportional loading are further exemplified by indicating solutions for a rectangular building frame, a Vierendeel girder, and a shed-type portal frame. A method for estimating deflections of a frame just as the collapse load is attained is then described, with some indications as to its reliability. More general conditions of loading than proportional loading are next discussed, and generalized load and failure concepts are defined. The theorems and techniques for determining critical shakedown loads under variable, repeated loading are then described and illustrated. The relation of the elastic-plastic shakedown analysis to the much simpler analysis for failure under single load applications is discussed.     

Short texts to explain problem — Solution structures — and vice versa

Linguistic analysis of short published reports leads to the presentation of an aigorithm that depicts the problem-solving process in terms of a series of evaluative questions. The work shows how reports enable us to define in detail the various stages of problem solving, and it shows that an understanding of these various stages enables us to recognise information structures in written texts; the writing of brief reports of high-priority information on which the whole thinking process is based is thus seen as a vital part of the problem-solving process. One report is analysed in detail to demonstrate the close relationship between information structures in the text and the real-life thought'action process it describes. There is discussion of how paragraphs, sentences and signals within the sentences enable the writer to communicate the information in a conceptual array that represents the actual thought/action process it describes. Educational implications for inter-sentential coherence, discourse analysis, and writing structures, and control of research through written reports are all discussed.     

A control problem with structural choices

The case is considered in which, during the operation of an optimal control system, the optimizer, in addition to applying his usual control, may switch structures. Necessary and sufficient conditions are derived and emphasis is placed on the special characteristics of this problem. Continuous and discrete time set-ups are considered and the separation principle is shown not to hold for the linear quadratic case in the presence of noise.