Experimental Research On The Bar Axial Force Of The Space Grid Structure By Frequency Method

The bar axial force testing of the active space grid structure is an important part in the large span space frame structure health monitoring.How accurately and conveniently to detect the bar axial force is one of urgent problems which need to be solved.It has academic values and application prospects necessarily to study the axial force of the single and multiple connected bar under the influence of many factors by frequency method,and provides a new way for health monitoring which is used to be tested bar axial force of the space grid structure quickly and easily.The bar axial force of the space grid structure is studied by experiment based on the basic theory of frequency method.Firstly,effects on the frequency of the bar are studied under many factors,such as forces,lengths,cross sections and boundary conditions.Secondly,effects on the frequency of the bar are studied under different numbers of connected bars.Finally,considering a space grid model as an example,rules of bar axial force testing by frequency method are analyzed.This paper deduces the variable relation between the axial force and frequency of the bar though the analysis of the basic theory by frequency method.The result shows: the values of frequency decrease with the increase of the bar pressure,and increase with the increase of the bar tension;this paper considers effects on different factors through numerical calculation and experiment research on single bar model.The result shows: the effects of length,cross section and bending stiffness have a relatively large influence on frequency,and the effects of force and vertical stiffness have a relatively little influence on frequency;This paper considers effects on different bars which are connected each other through experiment research on multiple connected bar model.The result shows: the values of the frequency increase with the numbers of connected bars,and the quantity of different bars has a different degree effects on the frequency;Experimental research on the frequency of the bar by a reduced scale model of space grid structure is studied.The result shows: the relation between axial force solved by testing frequency and frequency error is obvious.When the frequency error in a smaller range,the calculated axial force has a little error compared with the true value,while the frequency error in a bigger range,the calculated axial force has a relatively large error compared with the true value.