Dynamic Response Analysis And Experimental Research Of Single-layer Reticulated Shell Structures Subjected To Impact Loads

Since the human society becomes increasingly complex, the risks that structures suffer extreme accidental loads such as the bomb explosion and car collision increase. Large span reticulated shell structures are usually important buildings wit h larger flow of peopl e, so it may cause incalculable serious consequences once the structures damaged or even collapsed in extreme events. Such extreme attacks can be largely si mplified as impact loads. T he impact load is a strong and short-time accidental load which can i nevitably cause some degree of damage to the structures. Therefore, it is very urgent and realistic to research on the dynamic performance of large span reticulated shell under i mpact load. T his requires that we must take a detailed study on the dynamic re sponse, protection methods a nd measures of reticulated shell s under impact loads. In this paper, three methods of numerical simulation, model test and theoretical analysis are taken to research on the dynamic performance and structural calculation methods of reticulated shell under different impact loads. T hen propose reasonable and effective measures for anti-impact. And the main content s are:(1) Nonlinear explicit dynamic program ANSYS/LS-DYNA was applied for numerical simulation. T he geometric model wa s set up by preprocessing subroutine written independently. T he rate dependent Cowper-Symbol s model was taken as material model. T he method of node-to-surface contact which was based on penalty function method was taken as the contact algorithm method. T he paper described the analysis method of dynami c responses of reticulated shells subjected to impact loads and put forward to the implementation of numerical model, which was suitable for the dynamic impact analysis of reticulated shell s.(2) K6 single-layer spherical reticulated shell was taken as the model, and the whole process of dynamic analysis of reticulated shells under i mpact loads was carried out. T he dynamic responses and impact response modes of reticulated shel l under di fferent impact loads were summarized. T he dynamic responses of the impact response modes were studied, and the indexes for judging the critical state of structures of different impact response modes were proposed. T he critical energy between di fferent impact response modes was calculated, and the failure mechanism of reticulated shell in the per spective of energy absorption was revealed. Combining the impact response modes and damage level of reticulated shell under impact loads, this paper put for ward the dynamic index, performanc e of cl assification and corresponding quantitative indicators.(3) T he most unfavorable loading points were found out through analyzing th e dynamic response of single-layer spherical latticed shell s subjected to different impact loads. T he criterion of dynamic stability which was suitable for the impact and collision probl em of single-layer latticed shell s was proposed. I mpact loads were applied to the most unfavorable loading points of structures to analyze the dynami c stability of structures. T he dynamic response and impact response modes were combined to obtain the critical energy region of dynamic buckling of singl e-layer reticulated shells, and also the relationship between impact energy and displacement shells under impact loads. T he parameter analysis was carried out of structures from the aspect s of rise-span ratio and span.(4) Based on the analysis of 468 cases, the shock resistance of single-layer reticulated shells with lower support was discussed. T he paper summarized the impact response modes of the whole structures as the columns subjected to impact loads, and described the dynamic response and transfer-conversion r elation of energy. And then the regularity of three parameter s included di fferent impact height, mass and speed was di scussed. T he p roportion of plastic member s and defor mation of structures was taken as a basic index. As a result, the extent of damage of reticulated shell could be divided into four levels: basic intact, slight damage, moderate damage and severe damage. And the corresp onding evaluation indexes were proposed.(5) Model experiments of a large scale landing reticulated dome and a same dome supported with st eel tube columns has been conducted. And the impact tests were carried out on a shock table designed by our team. Mean while, the impact processes were shot by a high speed camera. Dynamic strain gauge, displacement sensor and acceleration sensor were used to monitor the time-hi stor y response of the key members and nodes of structures. Comparison of the test results and th e numerical simulation results was made to obtain the dynami c response and propagation law of stress wave of reticulated shells. T hus, the results of numerical simulation were verified.(6) According t o the dynamic characteristics of reticulated shells u nd er impact loads, the conclusion was that the third ring of K6 single-layer spherical lattice shells was the critical region, which was based on component sensitivity and distribution of key components. T he paper proposed four methods of anti-impact, and verified the effect of anti-impact design from two aspects of structural redundancy and shock resistance. Results showed that reinforcing the component s with high sensitivity could improve the redundancy of reticulated shells to some extent, which could enha nce the shock resistance of the structures effectively with a slight increase in the amount of steel. In addition, it could also improve the impact resistance of reticulated shell s by using square steel tubes instead of whole or part of the circular steel tubes of structures.