| With the rapid development of China's railway construction,the “Y”shaped platform canopy structures with single-column are wildly used in small and medium-sized railway passenger stations.The “Y” shaped single-column canopy structure is a statically indeterminate structure along the direction of the track,and a statically fixed structure perpendicular to the direction of the track.The number of components in this simple structure system is less so that the structural redundancy is seriously insufficient.In the event of an accident such as the explosion or the impact by a derailment train,the probability of progressive collapse for the canopy structure is extremely high.The seismic performance of single-column canopy structures has been studied deeply while the research and the related theory on the progressive collapse resistance of single-column canopy structures is still limited.The progressive collapse performance of single-column canopy structures is systematically investigated in this study.The main research contents and conclusions are as follows:(1)Based on a progressive collapse experiment of plane frame structure,the fiber model and the material constitutive model were verified by the test results using the finite element software ANSYS/LS-DYNA.(2)In order to investigate the resistance mechanisms and failure models of a typical“Y” shaped single-column reinforced concrete canopy structure,nonlinear dynamic analyses from the alternative path method were carried out in twelve collapse conditions while one beam or column of the canopy structure was removed at a time.By using the element importance index based on generalized structural stiffness to evaluate the importance of every component of the canopy structure,the results show that the side column is the critical component.(3)A serial of single-column canopy structures with different design parameters were designed based on current norms of China.The progressive collapse performance of these structures were studied through numerical analysis.By using data processing methods including correlation analysis and tornado diagram,the influence of each design parameters to the canopy structure were compared.The results indicate that the seismic fortification level,the slab type and the column spacing are the most critical parameters,followed by the frame beam height,the variable cross-section cantilever beam length,the concrete strength grade and the diameter of column.(4)The progressive collapse resistance of two single-column canopy structures with different structure forms in practical engineering had been compared.The results show that the canopy structure with concrete-filled steel tubular column has better performance on the progressive collapse resistance than the canopy structure with reinforced concrete column.(5)Five measures for resisting progressive collapse were provided.The influences of these measures on the progressive collapse performance were compared from durability and steel consumption.Among these measures setting diagonal bar,setting steel truss and setting diagonal stay cable were effective in improving the progressive collapse resistance while the other two measures including horizontal tie and increasing reinforcement in beams and columns were not effective enough.(6)Based on current progressive collapse design codes and above all research results,general design principles and some particular design suggestions were introduced in this paper for the single-column canopy structure design in our country.According to the existing progressive collapse design method based on the principle of energy conservation,the values of the resistance correction parameters under different column removing conditions which were used in linear static analysis were discussed for the single-column canopy structure.A simplified model were proposed for static analysis of progressive collapse response of single-column canopy structure under removing inner column and the calculation methods of three resistance mechanism were also provided under uniform loading. |
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