Blast Loading And Failure Mechanism Of Reticulated Domes Under External Explosions

In recent years,terrorist blast attack and accidental explosion caused by illegal operations in daily production and life have occurred frequently.Large span space structures widely act as landmark public buildings in a region or country.If they encounter explosion,it will cause great casualties and damage to facilities,and will bring incalculable economic loss and create a negative effect on society,so it is necessary to have a certain anti-explosion protection ability during the service period.Overall,it is of great social and economic significance to carry out the research on anti-explosion performance and protection methods of large-span space structure subject to explosion.However,there are few research on the large-span space structure subject to explosion,and there are many unsolved problems.In the aspect of blast load,the external balst load model which is suitable for guiding the design of large-span space structure is still blank,and there is lack of reliable test data as the basis for analyzing the spatial and temporal distribution characteristics and variability characteristics of blast load on these complex curved surface structures;In the aspect of structural dynamic response,there are still some deficiencies in revealing the dynamic response mode and failure mechanism of large-span space structure under external explosion;In the aspect of numerical simulation technology,there are great differences in the results and calculation efficiency with many numerical methods,and there is a lack of targeted verification test to establish efficient and reliable finite element numerical analysis model.Reliability based anti-explosion design is an important development direction in the research of explosion engineering field.Therefore,it has great theoretical and practical significance in the construction and development of anti-explosion theory on large-span space structures to establishe the probability model of structural response considering the uncertain of the blast load and structure,combining with theoretical analysis,numerical simulation and field test.So in this research,the main contents are shown as following:1.Blast tests and blast load characteristics study on the spherical shellBlast tests on spherical shell with different support height and rise-span ratio under external explosion were designed and carried out to investigate the influence of explosion parameters,such as mass of explosive,stand-off distance on the spatial and temporal distribution characteristics on the spherical shell,and try to obtain reliable experimental data;the differences of reflection behavior of blast wave on plane target and curved target were compared and analyzed,and the finite element simulation model which is suitable for studying the blast flow field on the dome structure under external explosion were established.Based on the parametric analysis,the influence of geometric structural parameters and explosion parameters on the distribution of blast load on the dome structure was further discussed.On this basis,a method suitable for describing the external blast load on the spherical shell was proposed.Combined with the spatial and temporal distribution characteristics and the principle of the similarity rate of the blast load on the structure,a widely applicable external blast load model for spherical shell was established.2.Uncertainty analysis of external blast load on the spherical shellConsidering the typical rigid model of spherical shell with support,120 independent explosion field tests under 6 working conditions were carried out and 480 independent samples of blast load parameters such as reflection overpressure,positive impulse,positive duration time and attenuation factor were obtained.Through the uncertainty analysis of each parameter of blast load,the corresponding probability model were optimized,and it is found that the normal distribution is the optimal distribution for each blast load parameter;Base on the calculation of the mean value and variation coefficient statistics of blast load samples,the probability distribution model of external blast load on the dome structure was established.Based on the quantile value,the external blast load model method with consistent assurance rate on the dome structure was proposed.Further,the adaptability of CONWEP method to predict the blast load on the spherical shell was evaluated.It was found that the CONWEP load method based on plane target can not give a blast load model with consistent assurance rate on the spherical shell,which is not suitable for the anti-explosion design of the spherical shell.3.Structural tests and failure mechanism study of single-layer reticulated domesIn order to investigate the failure modes of the single-layer reticulated dome structure under external explosion,the small-scale model tests of Kiewitt-6 single-layer s reticulated dome were designed.The elastic and destructive tests were carried out and three typical response modes were obtained.By comparing the results of several numerical simulation methods with the test results,it was proved that the one-way coupling method based on the blast load model on the dome proposed in this paper is superior in the study of the response of single-layer reticulated dome structure under external explosion.In addition,based on a large number of parametric analysis,the response law of single-layer reticulated dome structure under external explosion was discussed and four response modes were defined;further failure mechanism was also revealed with the perspective of energy distribution and absorption.Furthermore,through a large number of time history analysis of multiple response in the full load domain,two collapse modes,that are dynamic instability and strength failure,were concluded.4.Uncertainty analysis on the dynamic response of reticulated domes under external explosionsFirstly,the local sensitivity method was used to investigate the influence of geometric and material parameters of the member and the uncertainty of explosion parameters on the structural response.It was found that the cross-sectional area of members and explosion parameters act as highly sensitive factors for dynamic response.In addition,based on Sobol's global sensitivity analysis method and Latin hypercube sampling method,the transfer law between the uncertainty of high sensitive input parameters and the structural response was investigated,and the probability model of dynamic response of single-layer reticulated dome structure under external explosion was proposed and established.Furthermore,the assurance rate of various deterministic research methods was evaluated.It was found that CONWEP method is not suitable for the response study of single-layer reticulated dome structure;the proposed method of median load on the dome structure with certain physical significance can be used as the median response result,which is suitable for the dynamic response solution of reticulated dome structure under external explosion;the 1.2 times mass growth factor method can be used as a fast prediction method for the reliability analysis of engineering structure to some extent.