Numerical Evaluation of Pre-Damaged Beam Using Recycled Concrete Aggregate Strengthened by FRP Sheets

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The British University in Dubai (BUiD)
Fiber reinforced polymer (FRP) has been increasingly used nowadays as an effective rehabilitation method in buildings due to structural flaws and aging of building structures, therefore it is an effective method to repair beams, columns, slabs. The research is conducting numerical evaluation to know the behavior of recycled reinforced concrete (RCA) beam samples, in addition to normal weigh aggregate (NWA) beam as control sample with no shear reinforcement, when strengthened by carbon fiber reinforced polymer (CFRP). The purpose of having this kind of research is trying to predict the effect of strengthening RCA reinforced beam samples with CFRP without shear reinforcement on deflection and damage mode types (Shear- Moment). As a result, four numerical models will be investigated, two models of RCA and two models as NWA (Control Samples) beams un-strengthened and strengthened with CFRP-U wrapping. The behaviour of strengthening the reinforced concrete beam with RCA without shear reinforcement, has been studied using three main parameters. The first parameter is type of loading, loads ranges from 81.7-130.9 KN for static and dynamic load. The second parameter is type of FRP carbon fiber, which has been used “Master Brace FIB 600/50 CFS” types. The third parameter is the concrete strength with different strengths varies from 64.5-77.00 MPa. All parameters mentioned above have been considered carefully in the numerical analysis of FRP strengthened the RCA beam samples. The (RCA) beam type has been modelled in two models, one with 0.75% (5D) steel fibers in self consolidating concrete matrix (SCC) and the other without it, but both models using with 100 % coarse recycled aggregate (RCA), while (NWA) beam types has been modelled without steel fibers with compressive strength 70.50 MPa and loads ranges from 120.1-130.1 KN. The advantages of using SCC and steel fibers are to enhance shear capacity by achieving the best performance of structure integrity. Moreover, ductility and post-cracking of RCA beam will be improved. The analytical model cross section of the beam is 200mm depth, 150mm width and 1600mm length with three 12mm bars diameters as bottom reinforcement and for more additional checking, it has been added two 12mm as top reinforcement for the cross section, all rebars having length of 1540mm. On other hand, the longitudinal percentage of reinforcement ρ(As/bd)=1.4% , which has been selected to warranty the shear failure. In other words, along beam no shear steel rebars has been used; although, three closed stirrups rebars with 10mm diameter used at locations along 300mm distances from supports to prevent the concertation of stress and to be steel rebars hangers as well. The research demonstrates the load path with distribution of stress/strain and defection through both models under different values and types of loads using FE software which represents in (ANSYS Workbench). The results illustrate that the 3D modelling shows some differences in deflection values between RCA by and NWA samples when strengthened or strengthened by CFRP laminates and when used compression rebars as well, while no differences have been found in shear loads values under different types of experimental loadings. In addition, 3D-FE model (ANSYS Workbench) illustrates type and location of failure which confirms that where retrofitting is needed. The normal numerical analysis and strengthening calculations has been done as per ACI 318-19& ACI 440-17 standards by using (MIDAS Gen and MIDAS design plus) and compared to experimental results. All in all, numerical evaluations using FE software illustrated good prediction of stress, load path and failures specially shear failure of recycled concrete aggregate reinforced beam strengthened by external bonded CFRP laminates, in addition to identical strengthening calculations as per ACI 318-19 and ACI 440-17R.
Recycled concrete aggregate (RCA), Fiber Reinforced Polymer (FRP), Carbon Fiber Reinforced Polymer (CFRP), Carbon Fiber Reinforced Polymer U-Wrapping (CFRP-U), Reinforced Concrete Beam (RC), Normal Weight Aggregate (NWA), shear strengthening, retrofitting, Self-Consolidating Concrete matrix (SCC), ACI318-19, ACI 440-17R, Finite element (FE), Ansys Workbench, midas design plus, midas gen