Study On Failure Mechanism And Explosion-proof Method For Cylindrical Shell Under Internal Explosion

Because of the advantages of large spanning ability and good stiffness, cylindrical reticulated shell has been widely used in large public building. But due to large population flow in this kind of buildings, it is very easy to become the objective of terrorist explosion. The Research on anti-explosion and explosion-proof for cylindrical reticulated shell is necessary. Using the numerical simulation method, a numerical model of cylindrical reticulated shell structure under internal-explosion is established in this paper and the dynamic constitutive model of steel is used which was measured in an impact test. Study on the dynamic response, failure criterion, failure modes and mechanism is carried out, and a design method of explosion-proof is proposed. The main contents in this paper are shown as following.(1) Using the Hopkinson bar technique, the dynamic mechanics property and the fracture property of Q235 and Q345 are studied. The results show that, Q235 and Q345 have a significant effect of strain rate strengthening, Compared with low strain rate, the yielding strength has a obvious promotion under high strain rate; The failure strain is decreasing with the increaing of the stress triaxiality, and with the increasing of the strain rate, the failure strain is increasing of the two kinds of steel.(2) Using the explicit dynamics software LS-DYNA, a cylindrical reticulated shell structure under internal explosion is established which the effect of strain rate is also considered. The influence of dynamic response under internal explosion of using different kinds of constitutive model and whether the action of gravity is considered is compared and analyzed. A parameter analysis of the cylindrical reticulated shell is carried out, the results showed that, the dynamic response of the structure will be stronger with the increasing of connecting stiffness; excessive roof load goes against anti-explosion; with the increasing of length-span ratio, the dynamic response is becoming stronger; with the increasing of rise-span ratio, the degree of dynamic reponse is becoming larger.(3) Basing on the damage model, a failure criterion is established. On this basis scale of the parameter analysis has been enlarged, and 3 failure modes is summarized: Explosion Venting Destruction of Enclosure Structure, Large Deformation Destruction and Collapse Destruction of Reticulated Shell. Distribution law of the failure modes with the changing of parameters is studied, according to the chang of failure modes with the maximum geopotntial energy, reason for the collapse destruction of reticulated shell is explained; A damage assessment method for cylindrical reticulated shell structure under internal explosion is put forward and the damage equivalence curve is drawed,with can be used in the design of proof-explosion.(4) Basing on the research result of failure mechanism, a discuss on design method of explosion-proof of the cylindrical reticulated shell structure under internal explosion is carried out, the result shows that the discreasing of connecting stiffness and the increase of satety factor can improve the explosion-proof ablility effective of stucture; Combine with the feature of internal explosion, a design method of explosion-proof fitting for the cylindrical reticulated shell structure under internal explosion is put forward basing on the damage of structure.