Study On Seismic Measures Of Rural Farmer-built Multi-story Masonry Buildings

It is found in seismic damage surveying that the rural farmer-built masonry building accounts for a large proportion of all structures which were serious damaged by earthquake. Farmer-built multi-story masonry building, as the most common type of housing in rural area, are comprised of load-bearing walls constructed with clay brick or hollow brick, and the roof system constructed with wooden rafter and purlin or reinforced concrete. Lacking formal design and standard construction practice combind with poor quality examination on building materials, this kind of housing do not often meet seismic safety standards and have poor seismic performance. Hence, it is necessary to study earthquake-proofing technique of rural farmer-built multi-story masonry buildings to enhance their earthquake-resistance behavior and capability.Using survey evidence from Ms8.0 Wenchuan earthquake, rural farmer-built multi-story masonry buildings in typical region in the different intensity zone are selected as study object and their characteristics of seismic damage at the different intensity zone are analyzed using quantifier to describe seismic damage, only the vibration failure under the seismic action will be considered. Meanwhile, it is summed up seismic damage of walls, roof and nonstructural components of masonry housing in the different intensity zone. In addition, as load-bearing components of the masonry house, walls have been the key factor in earthquake surveying and researching on seismic damage. The impacts of damage level of walls for the failure mode of masonry are concluded through studying on seismic damage feature of walls in the different intensity zone. As walls bear a shear-compression kind of seismic action, a corresponding relation between three types of wall cracks and shear failure is analyzed.Through surveying the rural farmer-built masonry buildings in different regions in Gansu province, it is clear that this kind of housing is easily damaged by earthquake, and the reasons for their vulnerability are summed up. These factors include the bad construction sites, wrong ways of ground treatment, undesirable conceptual design, seismic damage being caused by walls and seismic measures being not used in buildings, etc. Moreover, this paper detailedly researches the countermeasure and methods to alleviate the earthquake damage that caused by the factors given above.Three kinds of ways, which is economic, simple equipped and fit for using of rural farmer-built masonry, are proposed. "Invisible constructional column" and "Bind method" apply to the low intensity zone, and the method of sand cushion sliding base isolation is fit for the high intensity zone. At the same time, this paper simulates the nonlinear damage of wall that adopts the "Invisible constructional column" with ANSYS. The result indicates that the method can effectively enhance the anti-seismic capability of the masonry walls. In addition, three-stories brick masonry building which use the sand cushion at foundation is calculated by ANSYS, and the results suggest that the building have longer natural period of vibration, can weaken seismic oscillation and enhance the anti-seismic performance.