THE CASTIGLIANO THEOREM AND THE PRINCIPLE OF VIRTUAL WORK HU Weiping ¹⁾

The principle of virtual work is used to better understand the role of support reactions in the appliction of Castigliano theorem. The essencial explanation is made to the question why the support reactions should be considered to be independent varibles in statically determinate structures, while they can be regarded as either independent or dependent varibles in statically indeterminate structures. This paper may help to learn the nature of Castigliano theorem besides using it freely.