A form-finding method of beam string structures — Offload by steps method

Abstract

The problem of form-finding of beam string structures was studied, and the method named offload by steps was put forward in accordance with the properties of the mechanical status of the structures. This method was used to find the form of the unstrained state on the basis of the pre-stressed state without the need to assume the unstrained form first. Numerical simulations and experimental research on the form-finding of beam string structures were carried out to verify the offload by steps method and, more importantly, to study the application of the method in engineering practice. The scale of the experimental model was 1/20, and the stretching pattern was the same as that in practical engineering. Comparisons of internal forces and deformations corresponding to unstrained and pre-stressed states of the model were made between experimental and calculation results. The following conclusions were drawn. First, the offload by steps method can be applied to the engineering practice without assuming the form of the unstrained state, and the form of the unstrained state corresponding to that of the pre-stressed state can be obtained directly. Second, the internal forces of the beam string structures in their pre-stressed states can be obtained easily by using the statically-determinate calculation model in the offload by steps method, which can guide design effectively. Third, the method for estimating the cable tension by balancing the deadweight of the beam string truss can be applied to engineering practice.