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Vol. 39 (1998) No. 3 December n. 128


Application of BP system in space structures

< Table of Contents for Vol. 39 (1998) No. 3 December n. 128
  • Journal Name: Journal of the International Association for Shell and Spatial Structures (J. IASS)
  • ISSN: (Electronic Version) 1996-9015
  • ISSN: (Print Version) 1028-365X
  • Issue: Vol. 39 (1998) No. 3 December n. 128
  • Title: Application of BP system in space structures
  • Author(s): B-B Wang
Abstract
In this paper, BP (base reinforced pyramid) simplex is introduced into space trusses to lower maximum bar forces. BP simplex is formed by introducing diagonal reinforcing bars into the base of a rectangular pyramidal simplex. The resulting BP system can be classified into two types: BP 1 grids, formed by introducing BP simplex to reinforce upper layer, bottom layer, or both layers of double layer square on square offset space grids or triple layer square on square space grids; or BP 2 grids, formed by introducing reinforcing bars in the bottom layer of double layer diagonal on square space grids or triple layer diagonal on square space grids based on the same principle. The efficiency of the single layer reinforcement case of BP 1 grids is highest when the reinforcing bars and adjacent chords can share equal forces. It is applicable chiefly in square and circular plans. Both the double layer reinforcement case of BP 1 grids and BP 2 grids have the additional advantage that tensional reaction forces in corner supports, which are caused by large global stiffness within layers because of BP reinforcement, lower the surge of maximum bar forces. So they are also applicable in rectangular and elliptical plans provided that the grids are basically two way load transferring. Case studies show that double layer BP 1 grids can lower the maximum bar forces of square on square offset space grids to about 1/3. While BP 2 grids can lower self weight simultaneously. The advantages of triple layer BP grids are not so obvious in comprison with triple layer diagonal on diagonal space grids as those of double layer form. BP system expands the application scale of double layer space trusses with much smaller bar forces without densifying grids.

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