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|Title:||SEISMIC RETROFITTING OF UNREINFORCED MASONRY BUILDINGS|
UNREINFORCED MASONRY BUILDINGS
|Abstract:||The Dissertation presents a brief account of the process of seismic retrofitting of unreinforced masonry (URM) constructions. Motivational fcoctors behind the retrofitting are discussed. Some of the effective techniques for retrofitting unreinforced masonry are presented. The galvanised welded wire method as prescribed by IS 13935: 2009 is applied as retrofitting technique in the study. To illustrate the process of retrofitting the URM constructions, numerical analysis of an existing building is presented. Survey of a block masonry' school building, located in zone IV, Uttarakhand is conducted. Measurement of the dimensions of the various components of the buildings i's done at site. Linear analysis of the building is performed using fief• analysis method'. Safety of piers in in-plane and out-of-plane are done. The material properties of the masonry are taken from various codes due to lack of available data. Torsional effect has also been considered in the analysis. Buildings resist lateral forces by their inelastic deformations. Hence a `non-linear analysis ' is also performed. The force-deformation parameters of the piers are determined as per FEMA 356: 2000. A 3-dimensional model of the building is developed in SAP 2000. The building is analysed for equivalent lateral forces acting at floor levels. The building is allowed to move in horizontal plane and rotate about a vertical axis to allow for torsional effects. Foundation is modelled as the lower most nodes fixed it all six degrees of freedom. The pushover curve so obtained represents the force-deformation characteristics of the building. Performance point of the building is determined as per ASCE 41: 2006 for Design Basis Earthquake (DBE) and Maximum Considered Earthquake (MCE) conditions. Iterations are done to find the idealised force-displaceinent curve by equal area method. The building is found to be 'unsafe' at MCE condition for life safely' level. Therefore `retrrfifting' of the building is suggested. Retrofit design for the building is carried out using galvanised welded wire mesh technique in accordance with IS 13935: 2009. Splints are provided at each corner positions and bandages are provided at the lintel level. Along the door and window openings also the wire mesh is provided. The mesh is connected to the walls properly by use of connectors and whole mesh is covered with cement mortar or micro-concrete. Drawings of a typical retrofitted wall and a section are shown|
|Appears in Collections:||MASTERS' DISSERTATIONS (Earthquake Engg)|
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