Study On Collapse Patterns Of Building Structures And The Distribution Of Survival Room In Collapsed Building Ruins

All the disastrous earthquakes happened both at home and abroad indicate that building collapse is the dominating reason of casualties. Improving buildings’ capacity of resisting collapse, using proper refuge strategy and taking post-earthquake rescue rapidly are the significant approaches to decrease casualties. Through field survey of earthquake damage, shake table collapse tests, collapse numerical simulations and theoretical analyses, this paper studies the collapse patterns and regularities of 3 typical types of buildings, and concludes the characteristics of building ruins and the types and distribution regularities of survival room in collapsed building ruins. Associating with the actual earthquake circumstance, this paper gives principle advices for refuge and rescue strategy during earthquakes. This paper mainly focuses on the next 6 aspects:1.Based on actual earthquake damage, this paper preliminarily gives the collapse patterns of 3 typical types of buildings, the principles of classifying building ruins and the survival room distribution regularities in relevant ruins. After looking up plenty of earthquake damage materials and conducting a detailed investigation at Old Beichuan, the author selected 28 typical ruin cases from plenty of building ruins, and then investigated into their building sizes, layout patterns, collapse directions and bracing members. By which, the principles of classifying building ruins are given, and the survival room distribution regularities in collapsed building ruins are revealed preliminarily.2.8 typical shake table test scale models representing RC frame structure, masonry structure with bottom frame and brick-concrete masonry structure were designed and relevant shake table tests were conducted. The changes of models’ dynamic characteristics, the emergence and development of destructive cracks and the whole collapse process were recorded and researched in detail. Based on all these new cognitions associated with actual earthquake damage, the collapse patterns of these three typical structures and the survival room distribution regularities are further concluded.3.Guided on the shake table test results of RC frame structure, a high efficient analysis method aiming at using finite element software to analyze the whole process of structure collapse is proposed. Plenty of collapse simulations are carried out with the nonlinear explicit finite element dynamic module of ANSYS. And though comparing simulation results with the shake table test results, the solutions of the problems which need to be noted during collapse numerical simulation are given, such as “gravity prestressing”, “hourglass control”, “strain rate effect”, “eroding contact” and “material selection”. Both advantages and disadvantages of different simulation methods are listed and a high effective simulation method is provided.4.Through the collapse numerical simulation analyses and comparisons of the typical RC frame structure collapse process under 10 sets of ground motion records which have different spectral characteristics and input directions, the influences of ground motion inputs on the collapse patterns of RC frame structures are discussed and relevant regularities are given. Through the collapse numerical analyses of masonry structure with bottom frame and brick-concrete masonry structure, the regularities obtained above are verified. Through the collapse numerical analyses of RC frame structure with internal corridor and multi-span RC frame structure with external corridor, the similarities and differences of collapse patterns between these two types of structures and double-span external corridor type RC frame structures are given. “Torsion abnormality”, “Small span collapse” in RC frame structures, and “Torsion of upper floors”, “sloping direction of upper floors change” in multi-span RC frame structures, which are four special collapse patterns discovered from the collapse numerical simulations, are deeply researched and their mechanisms are revealed.5.Based on the results of a large number of collapse tests and simulation analyses in this paper, the concept of "ground motion direction causing collapse" is put forward, and the "M value" method is established as a new method to identify the structural collapse pattern. Through analyzing the relationship between the ground motion direction and structural collapse pattern in the 8 collapse tests and the numerical simulations, it is proved that the influence on the structural collapse direction of horizontal ground motion has directional property. Thus the concept of "ground motion direction causing collapse" is put forward, and its generation mechanism and influencing factors are further discussed. Based on the above study and associated with the theoretical analysis of the structural collapse process, the "M value" discriminated method of the structural collapse pattern is put forward, and the rationality and feasibility is also verified through the collapse tests and numerical simulations.6. Base on the actual earthquake damage, earthquake simulation tests and numerical analyses results of typical structures, structural characteristics of three types of typical building ruins are deeply analyzed, the distribution regularities of survival room in building ruins of earthquake induced collapse are further given. Based on the collapse patterns of building structures and distribution regularities of survival room achieved above, principle suggestions on the effective escape routes, emergency refuge locations during earthquake, and the emergency rescue methods, the security measures during rescuing after earthquakes are put forward.