Natural Jute Fibre-Reinforced Polymer Composite System for Posttensioned Beam Strengthening in Flexure

Existing structures require repair and strengthening owing to degradation caused by incorrect design and construction, environmental impacts, or structural upgradation to meet new seismic design standards or to correct execution problems that occurred during construction. These strengthening requirements can be satisfied by a variety of strengthening techniques. The creation of a fibre-reinforced polymer (FRP) composite system offers a new design method for the strengthening of existing structures. In this study, posttensioned beams are strengthened by using sustainable materials such as natural jute fibre-reinforced polymer (FRP) composites. The performance of these composite systems in the flexural strengthening of posttensioned beams was used to assess their effectiveness. Consequential result for longitudinal reinforcement throughout the length of the beam for flexural strengthening was evaluated. Flexural performance, crack width, ductility, and load-deflection relationship study of control beams (Scheme A) and retrofitted beams (Schemes B and C) under different wrappings were considered in the investigation. An experimental study depicts that using the full wrapping (FW) technique increases the flexural strength of PSC beams wrapped in JFRP by 23% and, by using the strip wrapping (SW) technique, the flexural strength is increased by 10%. The JFRP composite system of strengthening has shown the highest deformability index and showed that the JFRP material has enormous potential as a structural strengthening material.

Combined Flexural and Shear Strengthening of RC T-Beams with FRP and TRM: Experimental Study and Parametric Finite Element Analyses

Due to inadequacies of reinforcement design in older structures and changes in building codes, but also the change of building use in existing structures, reinforced concrete (RC) beams often require upgrading during building renovation. The combined shear and flexural strengthening with composite materials, fibre-reinforced polymer sheets (FRP) and textile reinforced mortars (TRM), is assessed in this study. An experimental campaign on twelve half-scale retrofitted RC beams is presented, looking at various parameters of interest, including the effect of the steel reinforcement ratio on the retrofit effectiveness, the amount of composite material used for strengthening and the effect of the shear span, as well as the difference in effectiveness of FRP and TRM in strengthening RC beams. Significant effects on the shear capacity of composite retrofitted beams are observed for all studied parameters. The experimental study is used as a basis for developing a detailed finite element (FE) model for RC beams strengthened with FRP. The results of the FE model are compared to the experimental results and used to design a parametric study to further study the effect of the investigated parameters on the retrofit effectiveness.

Numerical study on the flexural performance of RC beams with externally bonded CFRP sheets

The numerical investigations on the structural performance of reinforced concrete (RC) beam strengthened with externally bonded carbon fiber-reinforced polymer (CFRP) sheets are presented. The nonlinear characteristics of materials (i.e., stress-strain relationships of steel reinforcement, concrete, CFRP, and CFRP/concrete bond stress-slip behavior) were adopted in three-dimensional finite element (FE) models. The validation of FE models was conducted by comparing the laboratory works carried out on two RC beam specimens with 2000 mm length, 300 mm height, and 120 mm width. The numerical results show a good correlation with the experimental results of the beam specimens, such as load-displacement curves, crack patterns, and failure modes. They allow confirming the capability of the developed FE model to predict the flexural performance of strengthened beams considering CFRP/concrete interfacial behavior. Furthermore, parametric investigations were performed to determine the effect of flexural strengthening schemes, CFRP length with or without U-wraps, and multiple CFRP layers on the flexural performance of strengthened beams.