Failure Mechanism Of Reticulated Shells Under Impact

With the wide application of large span structures in large public buildings, the mechanical properties of large span structures under impact and explosion have been gradually taken into account. The occurance probability of load has gradually increased due to due to the terrorist attacks: 9/11 incident is a typical example of such attack. Though the design of World Trade Center (WTC) represents the advanced level at that time, WTC still progressively collapsed in 9/11 incident. Besides, an airplane was forced to land the grid structure roof of Sao Paulo Exhibition Center in 1980s. It also proved the possibility that the large-span structures might be impacted. The research is required pressingly on many problems, such as Analysis method of dynamic response for Reticulated Shell under impact. It also has broad application prospects in other similar large and complex structures because it is at nearly blank stage for those structures. Therefore, the research is of obviously practical significance, and needs in-depth study. In view of this, the method for analyzing the impact response of the reticulated shell is proposed. Then, the research on the failure mode and failure mechanism is carried out in-depth. Based on the results of a large number of parametric analyses, the failure law is generalized. And the impact test is carried out to verify the analysis method and numeric conclusion. Finally, some protective measured are suggested.The main contents in this paper are shown as following.1. Analysis method of dynamic response for Reticulated Shell under impactThe practical and effective analysis method for impact response of Reticulated Shell is established, characteristic indicates of impact response, which contains the load and characteristic response, for Reticulated Shell is defined, analysis flow is discussed, and accurate numerical model of Reticulated Shell under impact is established. This paper systematically presents the process of analyzing the dynamic response by stages2. Failure mode and mechanics for Reticulated Shell under impactBased on the results of a large number of parametric analyses, the typical examples of single-layer Reticulated Shell and single-layer reticulated cylindrical shell subjected to impact have been illustrated. The whole course of failure cased by the impact and characteristic of load and characteristic response are described in detail. Based on the studies above, three failure modes of Reticulated Shell under impact are defined, the whole impact course is partitioned to three stages, and the failure mechanism for each mode is disclosured.3. Failure law of Reticulated Shell under impactIn order to make sure the failure law of Reticulated Shell under impact loads, a large number of parametre analyse has been investigated. The relationship between the largest dynamic responses/failure mode and energy obtained by shell was discovered, and the effection of initial kinetic energy of impactor on failure mode was discussed. And failure coefficient of global collapse is proposed to evaluate the anti-impact ability of structure. Then in order to make sure the failure law of global collapse, a large number of parametre analyse has been done by changing parameters of load and structure. The effection law of initial impact condition on global collapse of structure is obtained.4. Research on impact test of Reticulated ShellThe tests on Kiewitt-6 single-layer Reticulated Shell were carried out to verify the analysis method and analysis conclusion. The test consists of mode analysis, elastic impact test and the ruinous test. The results of test verify the true analysis method and typical failure modes of Reticulated Shell (local dent of structure and global collapse of structure). Then some factors which effect impact response are specified, such as support condition, initial deflection of impactor, damp and defection.5. Defence design methods and defence design suggestion of Reticulated Shell under impactOn the basis of former research on failure mechanism and failure flow, defence design method of Reticulated Shell under impact is proposed aiming at resisting global collapse of structure. The three defence design methods are light roof, global reinforced and critical position reinforced. Then defence effection is analysised, and defence design suggestion is put forward. Based on the theory obove, the theoretical framework of the Reticulated Shell under impact was primarily established.