Cumulative Damage Experiment And Simulation Analysis Of Long-span Spatial Arch Truss

Along with the social development, long-span spatial grid structure is widelyused in public buildings. But a large number of earthquake damage show thatthis kind of structures may occur low-cycle fatigue cumulative damage underthe disastrous earthquake, which product potential threats for a large number oflives and property. Therefore, the research for cumulative damage of space gridstructure has been becoming a current hot topic. This paper takes the steel pipearch truss model as the research object, has conducted the thorough researchfrom the model test, aspects of theoretical analysis and numerical simulation.First, perform the low-cycle fatigue tests of arch truss model under verticalcyclic loading, and according to the test results established damage assessmentmodel based on energy dissipation; Then, improved damage material model ofthe strain and energy ratio by using the energy damage principle, and by theprogram mixed hardening materials subroutine of coupling damage is developed;Finally, the arch truss model is studied by numerical simulation of damage accumulation. The main work and the results are as follows:1、For the first, the research conducted low-cycle fatigue test on6m-spansteel spatial arch truss with0.2,0.3,0.4span under vertical circle load at home,and analyzed the failure process and failure mechanism of the trusses to obtainthe hysteretic curves, skeleton curves, energy dissipation, ductility performanceand stiffness deterioration of trusses. The results show that the plastic strain anddamage are mainly focused on the node, and the node location are failure firstly.Thus damage of node zone has a dominant position in the whole of structure.The node appeared cracks will be parted in five to six loops, at the same time,structure strength, stiffness, energy dissipation capacity decline substantially.2、Based on damage mechanics theory, a damage assessment model based onenergy dissipation is set up. The evaluation model is used to analyze thecumulative damage development process of the arch truss model test, whichcompared with the recognized three damage assessment model. The results showthat this model not only reflect the change law of structure damage, but also canreflect the damage effects for structural cracks, expansion and fracture damage.3、In order to easily apply strain and energy ratio of material damage model,according to the energy damage theory, the model is improved through theintroduction of three axis function. By using ABAQUS software, improvedmaterial damage model was incorporated the user subroutine（UMAT），andmaterials subroutine of mixed hardening with cumulative damage is developed,which is applied to the solid element. 4、Take arch truss with0.2span for example, finite element model ofwhole structure for unstiffened space tubular joints was established based onentity unit for the first. The results of numerical simulation and experimentshow that the material damage influence is not large while plastic deformationis small, and that the effect of material cumulative damage graduallyincreases with the further development of plastic deformation, and that it willlead to overestimate the structure bearing capacity without thinking about theinfluence factors in the calculation, which will make the structure has certainsecurity hidden danger, and that simulation crack and structure failure mode areconsistent with test.