The Failure Theory And Dynamic Test Of Single-layer Spherical Lattice Shell Considered Damage

Single layer spherical lattice shells are widely used in modern large span space structures due to its light weight, graceful shape, and many other advantages.However, in recent years, because of the frequent earthquakes, as well as the stability of single-layer spherical reticulated shell, the development of single-layer spherical reticulated shell has been plagued.The dynamic failure of single layer spherical reticulated shell is mainly discussed in the following aspects: considering the material damage evolution, the failure criterion of single-layer spherical reticulated shell is explored in terms of energy. Thereafter the test which stimulates the overall process of dynamic failure test of single layer spherical reticulated shell is worked out combining the failure criterion, and thus the correctness of the criterion is verified; the simulation method is verified in this paper through test comparison and simulation process,considering the damage development and the structural dynamic failure of the lattice shell under dynamic action. In the end, effective collapse resistance methods of single layer spherical reticulated shell is proposed considering the computer simulation results and experimental data.(1) A structural damage evolution simulation method based on fiber damage of the bar is establishedFor the material damage of bars, combining FORTRAN interface of material subroutine in ABAQUS material subroutine was written by considering the material damage accumulation process. By the way of dividing space bar cross section into multiple integration points to realize the damage calculation of cross section fibe r, then observe the change of material damage process from the microscopic view. Co mbined with several existing test results, computer simulation results verify the accura cy of material subroutine. So it lays a foundation for further study on the dynamic da mage process of the single spherical reticulated shell.(2)Time-sensitive damage evolution and analysis of bearing capacity of single layer spherical shellResearches on the structure failure and the duration of seismic action are not yet prevalent by far. Simulation was made according to the stiffness change of the rod due to material damage caused by fiber fracture. Considering the damage accumulation of steel, the response of a single-layer spherical reticulated shell model under strong earthquake is analyzed using the material subroutine based on ABAQUS. The test results show that along with the earthquake, the failure of single layer spherical shell originates in the unit damage followed by subsequent progressive development. In this paper, the evolution law of failure caused by structural damage is discussed and the failure mode of single-layer spherical reticulated shell is established. By further analyzing the ultimate bearing capacity of single spherical shell at different time under different PGA conditions, it is noted that the evaluation of the ultimate bearing capacity of the structure needs to take both the magnitude and duration of the earthquake peak value into account, which contributes to the safety assessment of post earthquake structures.(3) A study of the single-layer spherical reticulated shell dynamic failure criterion based on the kinetic energyThe structure may experience irreparable plastic process under earthquake load.Standards and methods of many existing failure criterion of single-layer spherical reticulated shell dynamic are established based on statistics and evaluation. Some methods even predicts the damage degree of integral structure simply based on the plasticity of the rod. This type of methods have limitations in project engineering and thus are rarely suitable for spot test and experimental research. Within this context,this paper endeavors to explore the failure criterion of the single-layer spherical reticulated shell in terms of kinetic energy.This failure criterion can be established considering both the overall damage degree of reticulated spherical shell caused by changes in the kinetic energy increment and the kinetic energy increment vibration curve.(4) Secondary development of ABAQUS based on PythonAn interface is established through the ABAQUS scripting and customized using the Python language. Interactions are directly carried out through the scripting interface and software kernel. The secondary development of ABAQUS is carried out considering the single-layer spherical reticulated shell failure criterion based on the kinetic energy. This secondary development aims to possess automatic function of failure judgment during ABAQUS’s dynamic calculation of single-layer spherical which could greatly save the time cost of nonlinear failure of the single-layer spherical reticulated shell.(5) Experimental test of the integral dynamic failure process of the reticulated spherical shellTraditional experimental tests of the integral dynamic failure process of the reticulated spherical shell are apt to fail in presenting the integral failure process of the structure due to the unpredictability of dynamic damage. This paper endeavors to find out how to measure the plastic development of the single layer spherical reticulated shell plastic using the existing laboratory conditions and measuring devices. In line with the test targets, the process of the integral dynamic failure process of the reticulated spherical shell is observed by adopting an appropriate methods and evaluating collected data(6) The measures to improve the anti failure capability of single-layer spherical reticulated shell are put forwardCombined with experimental data and simulation analysis, it is found that the circular members first enter the plastic phase with the overall structure under severe earthquake action. Considering the postponing of the plastic development caused by the structure,a multitude of comparison analysis, is conducted on the plastic development of the structure when different circular member bars are reinforced. All these efforts are targeted to find the best reinforcement approach which can effectively postpone the plastic development. The shell is eventually reinforced by setting ribbed slabs onto the spherical joints according to the distribution of the broken bars of the structure and thus a refined model is established. Careful comparisons are made between the refined modeling and simplified modeling of the single-layer spherical reticulated shell through simple simulation method.Consequently the refined single-layer spherical reticulated shell perform better than the previous simple model in collapse resistance.