The paper demonstrates concepts for designing stiffer structures. They are: (a) the more direct the internal force path, the stiffer the structure; (b) the more uniform the internal force distribution, the stiffer the structure; and (c) the smaller the internal forces, the stiffer the structure. These concepts are applicable to the design of many structures. Two ways of implementing the concepts into practice are provided. Simple examples are given to illustrate the implementation and the efficiency of the concepts. Laboratory tests and the demonstration of two physical models further confirm the findings. Several practical designs are also provided to show the applicability and significance of these concepts. An alternative definition of structural stiffness is given which complements the existing definition and allows for designing stiffer structures. It is interesting to note that using the concepts may lead to not only stiffer but also more economical and elegant designs. Tianjian Ji, PhD, CEng, MIStructE Manchester Centre for Civil and Construction Engineering, University of Manchester Institute of Science and Technology, Manchester M60 1QD UK
Steel-concrete-steel (double skin), composite, construction consists of a core of concrete sandwiched between relatively thin steel plates. Elements of double skin construction have structural applications in submerged tunnels, gravity seawalls, bridge deck slabs and blast walls. For efficiency, full composite interaction is required between the core and surface skins. This can be promoted using steel with textured surfaces and this paper describes experimental details on beams using steel plate having four different interface preparations: plain, Durbar, Expamet and Wavy wire. 32 beams were tested in all, inclusive of three grades of core concrete: C40, C80 and C150. Full composite behav-iour was observed utilising Durbar, Expamet, and Wavy wire interfaces. Expamet and Wavy wire details are recommended for practical application. N. K. Subedi, BSc(Eng), PhD, CEng, FIStructE, FICE, FASCE Reader, Department of Civil Engineering, University of Dundee, Dundee DD1 4HN