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Nonlinear Response of RC Frame Considering PVM Interaction and Design Amplification Factors for Open Ground Storey StructureAuthor: Swajit Singh Goud Date: 20220414 Report no: IIIT/TH/2022/51 Advisor:Pradeep Kumar Ramancharla AbstractThe extent of damage in a structure can be estimated numerically using Nonlinear analysis (NA). On the basis of the applied forces, NA can further be classified as Static Nonlinear (Pushover Analysis) and Dynamic Nonlinear (Time History Analysis). The response of a structure can be predicted effectively using Nonlinear analysis, provided adequate assumptions are made. The efficacy of Nonlinear analysis depends on the accurate assumptions pertaining to types, locations and pattern of nonlinear hinges. Various hinge definitions that are generally used for NA of a structure includes Axial, Shear, Flexural or Torsional forcedeformation relationships. However, these forcedeformations are seldom mutually exclusive, and can be coupled to achieve a better numerical simulation of actual behaviour, and failure mechanism. The most common combination of hinge definition applied for NA of 2D frames is PM2 hinges (PM2M3 in case of Space Frames). As per the literature, the three most common modes of failure in low and medium rise structures are Shear failure, Flexural failure, and a combination thereof. This observation emphasizes the need to consider the combination of shear and flexural hinge definitions during analysis, to better estimate the behaviour and effectively predict the failure pattern of a structure. The literature also suggests an inversely proportional relationship between the shear and moment capacity of a section beyond first yield. The prevalent practice in a typical design office requires an engineer to define a flexural hinge (in terms of momentrotation/curvature relationship) for a section, and assigning a value for ultimate shear strength causing brittle failure, and thereby neglecting the effect of shear on the nonlinear behaviour of the section. These observations form the primary objective of the work presented here, which is to develop a ShearMoment interaction behaviour for a Reinforced Concrete (RC) section. Among the commonly constructed RC structures, Open Ground Storey (OGS) structures have swiftly become the most preferred type of RC buildings, primarily owing to large open spaces on the ground level. However, structural engineers deem OGS as a form of vertical irregularity, and advice special care while designing, to prevent collapse, especially in seismic prone areas. The literature consists of a plethora work on modelling of infill panels, especially in case of an OGS building. Various models exist to effectively simulate the effect of infill wall panels, the most common of which are single strut model, double struct model and three strut model. However, in a typical design office, buildings are generally analysed as bare frames, thereby neglecting the effect of infill panels, and leading to incorrect estimation of behaviour of the building. This practice, when employed for an OGS building leads to further deviation of analysis results from the actual behaviour. Furthermore, when designed as bare frames, the buildings having OGS exhibit higher strength as well as stiffness on the storeys above the ground storey. Since the OGS is both a soft and a weak storey, it will incur higher stresses, leading to significant damage. The damage sustained by the structural members in the OGS depends primarily on the ductility of columns, relative lateral stiffness and strength with respect to the adjacent upper storeys. Further, the height of the building having an OGS has a significant effect on its behaviour. The various factors governing the behaviour of a building having OGS can be combined together to obtain a Amplification Factor (AF), that can be used as a multiplication factor to modify the demand on the OGS. This forms another important objective of the present work. The AF will primarily depend upon: 1) Material property of masonry, 2) Design type of RC building, 3) Percentage of openings present in upper floors, and 4) Aspect ratio of the building. In present study, an attempt is made to determine the shear capacity of reinforced concrete section with respect to different deformation levels and to understand the effect of shearmoment interaction of reinforced concrete section in nonlinear zone while performing nonlinear analysis of the structure. Alternatively shear hinge of VØ type is proposed in place of existing one value of shear capacity and its effect on nonlinear response of the infilled RC structure because of change in shear failure mechanism is studied. Also an attempt is made to compute design amplification factor (DAF) for safety of OGS during seismic events considering different parameters aforementioned mentioned above and numerical correlation of same with DAF is done using linear regression analysis. Full thesis: pdf Centre for Earthquake Engineering 

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