SEISMIC REHABILITATION OF SHORT RECTANGULAR RC COLUMNS

Non-ductile response of structural elements, particularly columns, has been the cause of numerous documented failures during earthquakes. The objective of this experimental study was to evaluate the non-linear behaviour of non-ductile reinforced concrete short columns under lateral cyclic deformations and to evaluate rehabilitation schemes. Three reinforced concrete short columns were tested under cyclic lateral loads and constant axial load. The behaviour and effectiveness of different rehabilitation systems using carbon fibre reinforced polymers (CFRP) were investigated. Two different techniques to improve concrete confinement were used in the two rehabilitated specimens. It was found that it is possible to eliminate the non-ductile modes of failure of short column using anchored CFRP wraps. In addition, an analytical model to predict the confining effect and the total shear resistance of rectangular reinforced concrete columns with anchored fibre wraps was introduced. The confinement model is an extension to an available model for concrete confined by steel reinforcement. The model was used to predict the shear capacity of the tested specimens and has shown good results.     

Estimating the Seismic Performance of CFRP-Retrofitted RC Beam-Column Connections Using Fiber-Section Analysis

Over the past two decades, many experimental techniques have been developed to improve the efficiency of the externally-bonded fiber-reinforced polymers (FRPs) in order to improve the structural performance of reinforced concrete (RC) beam-column connections. Numerical analysis is also being used as a cost-effective tool to predict the experimental results and to further investigate the parameters that are beyond the scope and capacity of experimental tests. In this study, at first, a fiber-section modeling approach is developed for estimating the seismic behavior of RC beam-column connections before and after application of FRP retrofits. The accuracy of the analysis results were validated against a series of the available experimental data under both monotonic and cyclic loadings. It was pointed out that the proposed model can predict the strength and displacement of un-retrofitted and FRP-retrofitted RC beam-column connections up to the failure points. The verified model was then used to perform a parametric study pertaining to the effect of longitudinal reinforcement ratio on the efficiency of the adopted FRP retrofitting technique to improve the structural behavior of RC beam-column connections.     

Flexural Performance of Small Fir and Pine Timber Beams Strengthened With Near-Surface Mounted Carbon-Fiber-Reinforced Polymer (NSM CFRP) Plates and Rods

In order to study the flexural performance of fir and pine timber beams strengthened with near-surface mounted carbon-fiber-reinforced polymer (CFRP) plates and rods, bending tests on 20 specimens are carried out, including four unstrengthened specimens, four specimens strengthened with CFRP plate with the dimension of 1.4 mm × 30 mm, four specimens strengthened with CFRP plate with the dimension of 2.8 mm × 30 mm, four specimens strengthened with one Φ6 mm CFRP rod, and four specimens strengthened with one Φ8 mm CFRP rod. The proportions of fir specimens and pine specimens are 50% and 50%. The results show that compared with the unstrengthened specimens, there is an improvement in flexural capacity and stiffness of the specimens strengthened with near-surface mounted CFRP plates and rods respectively. Finally, the calculation formulas of the flexural capacity of fir and pine timber beams strengthened with near-surface mounted CFRP plates and rods are presented.