ASI Finite Element Analysis of Dynamic Collapse Behaviors of Framed Structures Considering Member Fracture

Abstract


The technology used in the demolition of buildings has always been a major interest in the civil engineering field. Conventional demolition techniques using hydraulic concrete crusher, concrete cutter or non-explosive demolition agent requires a longer period of work and higher cost. A demolition technique by controlled explosion using high explosives has developed in recent years. In Japan, the explosive demolition technique has recently been used only in a few demolition cases, such as on the buildings of the international exhibition in Tsukuba or a vacant hotel in Kyoto. The explosive demolition has a high risk of damaging other neighboring buildings especially in urban areas, even though it increases work efficiency. Therefore, the pre-assumption by computational analysis has become an essential matter in the process.
The Great Hanshin Earthquake, which occurred in January 1995, damaged a wide area. The structural design guidelines for buildings especially against vertical seismic wave has been thoroughly reconsidered. Therefore, the arrival of a convenient technique to analyse collapse modes of structure objects under 3 axes of excitation, is now desired.
However, generally used finite element code needs some extra complicated processes to simulate these kinds of dynamic collapse problems which contain strong nonlinearity and discontinuity, such as fracture occurred in flexural damage or shear damage in reinforced concrete members.
The Adaptively Shifted Integration (ASI) technique, which produces the highest computational efficiency in the finite element analyses of framed structures including static and dynamic collapse problems, is applied to the explosive demolition analysis and the seismic damage analysis of a reinforced concrete building. By expressing an explosion or a fracture by a plastic hinge located at the exact position with a simultaneous release of resultant forces on the element, discontinuous problems such as these dynamic collapse problems can be easily analysed even by the finite element code with the displacemental form. By using the algorithms described in this paper, sufficiently reliable solutions for the practical use have been obtained in the explosive demolition and seismic damage analyses of a 5 stories-5 span reinforced concrete building. The present technique can be easily implemented with a minimum effort into the existing finite element codes utilizing the linear Timoshenko beam element.


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