Form-Finding Of Hoisting Induced Self-forming GFRP Elastic Gridshells

The elastic gridshell is a new type of gridshell structure,which consists of long-continuous GFRP circular tubes and forms its shape from an initially flat grid into a three-dimensional shell-like geometry by deforming elastically under gravity during the hoisting process.In addition to the traditional gridshells’ outstanding feature such as covering long spans with low self-weight,high space efficiency and ability to allow for a variety of aesthetical shapes,the elastic gridshell present some other advantage of being simple to construct and demolish rapidly.However,there is few elastic gridshells constructed so far since its first implementation in German,1970,due to the lack of general form-finding method to either predict the forward shape transformation undergone from an originally flat grid into a threedimensional mesh or the backward shape transformation undergone from a pure aesthetical surface to a flat grid.In addition,no efficient design tools are developed to help the engineers design or form-find gridshells.As a result,it’s challenging for engineers to form-find and model the mechanical behavior of gridshell.This thesis presents a study of the hoisting-induced self-forming GFRP elastic gridshell,which take advantage of the GFRP qualities of low density,high strength,relatively low elastic modulus and high flexibility.At first,this thesis presents a form-finding algorithm for a certain type of elastic gridshell that has the single symmetry plane,followed by the numerical simulation of hosting construction process.Secondly,to generalize the form-finding method,a gridshell design tool has been developed to generate a gridshell grid with elements of equal length on an arbitrary surface,and an algorithm has been implemented to flatten the spatial gird.Based on the functionality developed,some kinds of surface are transformed into flat grid to study on the mechanical behavior and the difference between the FEM result and the original geometry.Finally,a gridshell form-finding tool has been developed by integrating the form-finding program and modeling program,with capability of structural design module under the blueprint of structure design software.This thesis shows that the form-finding algorithm proposed is highly efficient to meet the demands of construction.The constructed GFRP gridshell structures are found to behave reliable load bearing capacities.The gridshell design tool is also adaptable and available to arbitrary surface,and the cases studied expand the way to hoist up gridshells,with some understanding of the shape transformation shown.The integrated design tool is multifunctional and helpful to design and analysis the gridshell.