Improvement in seismic performance of stone masonry using galvanized steel wire
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This research is about using either freely available natural stone or rubble left behind earthquake disasters to build a seismic resistant house. The bottom line of this research is to develop a simple and effective technique for building a stone masonry house that will not collapse during the seismic event. Traditionally constructed stone masonry houses are highly vulnerable to seismic loadings. In the past, most of the un-reinforced stone masonry buildings had collapsed causing many casualties during the earthquake events. In order to address this problem, various options have been recommended by the researchers for reinforcing new stone masonry buildings as well as strengthening existing buildings. However, developing an economically viable and socially acceptable option for improving seismic performance of the residential stone masonry houses is still remaining a great challenge. In this context, a system of reinforcing rubble masonry using galvanized steel wire (GSW) mesh has been proposed in this research. A gabion like technique is adopted for wrapping the wall with a mesh. It is a simple technique, which can be easily learnt by the users and applied to build their houses. This method is suitable even in remote and isolated areas, where access to the technical inputs is not available. In addition, this technique seems to be useful during reconstruction phase after the earthquake disaster, for clearing up sites and building safer houses side by side. The performance of the proposed reinforcement system was investigated both experimentally and analytically under static and dynamic loadings. Suitable materials for this research were identified and the required materials were collected. All specimens were prepared and cured in the laboratory environment. Wall specimens were constructed with due considerations to the owner builder construction mode, where owners themselves construct their houses. Both unreinforced and reinforced wall specimens were prepared for static test as well as shake table testing simulating strong earthquakes. Two types of reinforcement schemes have been proposed in this research. In the first method, reinforcement mesh is woven around the wall using steel wire, whereas in the second method, pre-fabricated meshes are used. Developing connecting techniques between adjacent meshes are some of the significant contributions of this investigation. This method makes this reinforcement system practicable using pre-fabricated meshes. Moreover, a simple method for tightening the mesh has been developed in this research. This tightening technique makes the proposed reinforcement system more effective in seismic performance than other types of external mesh by allowing limited deformation of the building during ground motions. Most of the testing procedures required for this research were not covered in the existing standard methods. Therefore, several additional techniques required for preparing the specimens and testing have been developed during this research, which are given in the relevant sections. Two terminologies have been proposed for describing the strength of rubble wall in flexure. Materials were tested for some basic properties as well as few reference parameters, which can be used for comparing the results of this research to the relevant cases. Static tests on unreinforced wall specimens have provided the basic strength properties of the wall, whereas testing on reinforced specimens have indicated potential effectiveness of the proposed scheme under dynamic loading. This has been verified by shake table testing. A theory has been proposed for explanation of the behaviour of an externally reinforced beam and some relations have been derived. Deformation characteristics of a hexagonal mesh have been derived so that the theory developed for externally reinforced beam could be applied to the GSW reinforced wall. A set of analytical procedures have been developed and applied for the assessment of a single storey and two storey buildings.
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