Study The Mechanics Inbeings Of Open-Web Grids And Open-Web Sandwich Plates From The Stiffness Variety

The open-web structures have four types, including plane open-web trusses, open-web grids, open-web sandwich plates and open-web shells. They have many properties, such as reasonable stress distribution, ability to realize large span, low building cost and so on, and have been widely used in spatial structures, especially in covers and floors of the buildings. Based on the available researches, the mechanical behaviors of these kinds of structures are studied from the view on stiffness variety.Firstly, the development, the researches and the applications of the open-web structures are introduced, and the characteristics of the four kinds of open-web structures are mainly given in details. The relationships among plane open-web trusses, grids and sandwich slates are presented and furthermore the differences between the open-web grids and the open-web sandwich plates are given especially, the analysis method of the former three structures are expounded as well.Based on the clue that the open-web grid and the open-web sandwich plate are composed of the open-web trusses in several directions, the stiffness variety of the plane open-web truss is studied. As a result, the most reasonable height and the main geometric parameters' influences on the stiffness are deduced. And then some stiffness optimization measures are presented. In order to prove the measures, an example is implemented.Based on the conclusion deduced above, the mechanics inbeings of flat open-web structures are studied from the stiffness variety. The influence of the main geometrical parameters on the stiffness are compared, and then several methods to optimize the structural stiffness are presented, such as selecting reasonable height, changing sections, altering span length, adding diagonal bar. At last, the ANSYS modes are established, and the validity and practicability of the stiffness optimization measures are verified by using different geometric parameter. The section of the vertical bar plays a much more important role on the most reasonable height than others.After the stiffness analysis of the open-web sandwich plate, the further research on "Modified Practicality Analysis Method" has been developed, the formula of the local moment is deduced as well, which accurately reflects the stresses of the end of member. The reasonable method on section design is put forward while thedisadvantages of simplified method put by fore researchers are revealed.At the end of the thesis, some conclusions are summarized and the topics for further research are put forward.