In the last two decades, due to disasters happening around the world have been recorded precisely. People have begun to understand that earthquakes fall under several categories. Most of the earthquake-induced catastrophes, including fallen bridges, building collapses, soil liquefaction, and landslides, can only appear in shear banding zones induced by tectonic earthquakes. It is important to mention that tectonic earthquakes are different from other earthquakes because, in addition to the seismic vibration effect present in all earthquakes, tectonic earthquakes have a shear banding effect. In a tectonic earthquake, the shear banding energy can be more than 90% of the total earthquake energy, and the primary cause of earthquake disasters is the presence of the shear banding. In the past, the cause of earthquake disasters has been generally identified by structure dynamics researchers, without any proof, as the insufficiency of seismic-vibration resistant forces. Therefore, the modification of building codes and specifications has only focused on increasing these resistance forces. However, this type of specification modification cannot guarantee that an earthquake-resistant design structure would not fail due to shear banding. Thus, it is the objective of this study to present appropriate earthquake disaster prevention methods for a tectonic earthquake.
Part of the book: Earthquakes
Although geotechnical engineering design must meet seismic design specifications, many geotechnical failures, including foundations, retaining walls, and slopes, have nevertheless occurred during tectonic earthquakes. The evaluation of the ultimate bearing capacity of the foundation, the active and passive earth pressure of the retaining wall, and the safety factor of the slope all need to use the shear failure band and soil plasticity models at the same time. In view of this, it is first proven that shear failure bands can only appear in the strain softening model. Secondly, it is shown through case studies that traditional evaluation methods for determining the foundation ultimate bearing capacity, the active earth pressure of the retaining wall, and the safety factor of slope stability all adopt both the shear failure band and the perfectly plastic soil model. Since the perfectly plastic soil model is incompatible with shear failure bands, this results in a large number of foundations, retaining walls, and slopes failing during tectonic earthquakes. Based on the research results, it is suggested that a soil strain softening model compatible with shear failure bands be adopted in the analysis of geotechnical engineering projects so as to ensure safety during tectonic earthquakes.
Part of the book: Earthquakes
It is found that the failure of the structure conforming to the current seismic design code can only occur in the shear band of the tectonic earthquake, and with the increase in the amount of shear banding, the boundary conditions of the structure gradually deviate from the original design ones; therefore, the seismic insufficiency of structures therefore continues to increase. With the increase of the seismic insufficiency of the structure, the structure will appear more and more serious damage such as cracking, tilting and subsidence, and collapse. Based on the findings of this study, the author suggests that the main task of the seismic design of structures is to prevent the shear banding of tectonic earthquakes from extending to each element of the structure, rather than continuously increasing the level of vibration fortification of each structural element. Only in this way can it be ensured that the structures complying with the seismic design specifications will not be damaged such as cracks, tilting and subsidence, and collapse due to the deviation of the boundary conditions from the original design ones in shear banding.
Part of the book: Natural Hazards