Conceptual Design Of Lightweight Structures: The Role Of Morphological Indicators And The Structural Index
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W. P. De Wilde
Firstly, but in no way exclusively, this paper addresses architectural engineers facing critical design decisions in the phase of so-called \“conceptual design”. The resulting design must yield a structure showing a sound behaviour in both the serviceability limit state (SLS) and in the ultimate limit state (ULS), also meaning that three essential criteria should be satisfied: strength, stiffness and stability (the latter including, if relevant, an acceptable dynamic behaviour). However, the question very often remains open as to which of the three criteria is overruling the other ones. This paper, a synthesis of the work of a research group headed by the author, tries to show that a conceptual design methodology can be developed, hereby using the concept of morphological indicators (originally developed by P. Samyn, subsequently P. Latteur and within the research group) and a structural index (introduced by Shanley). This methodology also gives an answer to the question that very often arises when designing lightweight structures: \“design for strength” or \“design for stiffness”? Examples in subsequent papers, presented during this Conference and thus included in these Proceedings, illustrate the methodology nowadays used by our students in Keywords: conceptual design of architectural structures, strength, stiffness, structural stability, structural vibrations. 1 Morphological indicators The so-called morphological indicators (MI) were introduced by P. Samyn  in 1999. As different papers, both within this conference and in other journals and architectural engineering when designing and analysing their structures.