Stressing State Analysis Of CFST Arch Supports Based On Expanded Experimental Data

In recent years,the mining of coal mines and other minerals has turned to the deep strata,and concrete-filled steel tube supports have been used in more and more deep coal mine tunnels,due to their superior bearing capacity.At present,various research results of concrete-filled steel tubular arch structures have been obtained.However,the load conditions,constraint conditions and dimensions of the support structure used in roadway are obviously different from those of the arch structure on the ground.Therefore,the research results may not be applicable to the un derground arch support structures,so it is necessary to specially study the mechanical performance and working behavior of the arch support.However,the bearing capacity of the arch support is often determined by the study under the uncertain ultimate bearing state,and the prediction of the bearing capacity is often empirical and statistical.Hence,it is difficult to ensure the accuracy of the prediction results.By using structural stressing state theory,the regularity of structural working process can be found from a new angle,which opens up a new way to determine the bearing capacity of structure and its working mechanism.Therefore,this paper introduced structural stressing state theory into the analysis of various structural parameters of concrete-filled steel tube arch supports under six-point radial uniformly distributed load:?1?The numerical shape function interpolation method was used to expand the experimental data of arch supports,so as to effectively adapt to the analysis of structural stress state.Firstly,the basic parameter?generalized strain energy density?representing the stress state of arch supports were constructed by using the extended test data.The numerical model and the corresponding characteristic parameters were constructed to represent the stress state of the arch support.Then,the generalized strain energy density sum(GSEDs,i.e.,variable: E_j,norm)were used to characterize the overall stressing state of the arch supports,and the curves of characteristic parameters varying with the load(E_j,norm-Fj curve)was plotted.?2?The Mann-Kendall criterion was used to judge the mutation characteristic points of curve E_j,norm-Fj,revealing the characteristic load of the arch support: failure load?the starting point of the failure process of the arch support?,elastic-plastic branch point load,continuous failure load,etc.Furthermore,the three characteristic loads divided the four working stages of the arch support with different stressing state characteristics: elastic,elastoplastic,failure state and continuous failure stages.?3?The stress state modes of the arch bracket were constructed with the experimental strain and increment,and the mutation characteristics of the stress state modes were investigated.Furthermore,the stress and strain fields of the expanded experimental data were constructed to show the evolution characteristics of the stressing state of the arch support.In addition,the characteristic parameters of internal forces were constructed and their evolution with the increase of load was investigated.All the analysis had verified the regularity mutations of the stressing state pattern before and after the characteristic loads.?4?The stressing state of different parameters?including steel pipe diameter and wall thickness,the rise-span ratio and round steel reinforcement?of concrete-filled steel tube arch supports was analyzed in four aspects of the generalized strain energy density,the response data?strains and displacements?,strain fields and internal forces,to explore the changing characteristics of the stressing state for various concrete filled steel tube arch supports.The influences of various parameters on the characteristics loads were analyzed and the inevitability and regularity of the appears of characteristic loads was further verified.