Fiber reinforced polymers (FRP) have been widely used in retrofitting and strengthening of deteriorated or deficient reinforced concrete (RC) elements. A major concern about those systems is their performance under elevated temperature which limits the application of FRP for strengthening requirements. Fire protection of the strengthening FRP system can be made by applying an external coating layer of a thermal resisting material. In order to predict the fire performance of such insulated FRP-strengthened members and their efficiency, experimental investigations are required to be carried out for such elements under realistic fire conditions, which requires time and cost. This paper presents numerical modelling of RC beams strengthened with externally bonded FRP and insulated by a fire protection layer under elevated temperature specified by standard fire tests. The nonlinear time domain transient thermal-stress finite element analysis is performed using the general purpose software ANSYS 12.1 in order to study the heat transfer mechanism and deformation within the beam for fire conditions initiating at the bottom side of the beam. The finite element model accounts for the variation in thermal and mechanical parameters of the constituent materials such as concrete, steel reinforcement bars, FRP and insulation material with temperature. Application is made on an FRP-strengthened and insulated RC T-beam which has been experimentally tested in the published literature in order to verify the adopted modelling procedure. The obtained numerical results are in good agreement with the experimental results regarding the temperature distribution across the beam and mid-span deflection. The presented procedure thus provides an economical and effective tool to investigate the effectiveness of fire insulation layers when subjected to high temperatures and to design thermal protection layers for FRP strengthening systems that satisfy fire resistance requirements specified in building codes and standards.
There is a need to create a new generation of rehabilitation and design processes that integrate performance-based engineering principles. These include evaluating available capacities and structural strength then comparing them to deformation demands related to acceptable performance levels. This paper concerns with structural non-linear static analysis procedure (NSP) to investigate the performance of reinforced concrete (RC) buildings under seismic hazard. Two case studies of constructed high-rise buildings were analyzed using response spectrum analysis (RSA) and pushover analysis (POA) to evaluate the post-yield behavior, relative damage of the structure, story shears, roof displacement, story drifts, story moments, time period, plastic hinges formation, structure performance level and response modification factor (R). Based on the results of performance points for the two case studies, the buildings can sustain seismic base shear ranging from 85% to 65% of their ultimate capacity from POA in X-and Y-Directions. Furthermore, the calculated response modification factor differs from that prescribed by building codes.
In recent decades, Fiber Reinforced Polymers (FRP) have shown tremendous potential for retrofitting or repairing existing deficient or damaged concrete structural elements due to their superior properties such as high strength, corrosion resistance and ease of application. However, concern arises about the vulnerability of FRP material to combustion under fire condition, since they are usually applied to the exterior surface of structural members. Damage of the FRP strengthening layer due to high temperature is likely to decrease the load carrying capacity of the columns and threaten the safety of the structure. This paper presents numerical investigation of the behaviour of reinforced concrete (RC) columns strengthened with FRP sheets and insulated by a thermal resisting coating under service load and fire conditions. The finite element numerical modelling and nonlinear analysis are made using the nonlinear finite element analysis software ANSYS 12.1 [1]. The numerical model is verified for several FRP confined and insulated RC columns that have been experimentally tested under service load and standard fire tests in the published literature. The obtained numerical results are in good agreement with the experimental ones regarding the temperature distribution and axial deformation response. Consequently, the presented modelling gives an economic tool to investigate the behaviour of loaded FRP strengthened RC columns under high temperatures occurring in case of fire, if the modelling is verified against experimental works. Furthermore, the model can be used to design thermal protection layers for FRP strengthened RC columns to fulfill fire resistance requirements specified in building codes and standards.
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