This paper presents a nonlinear finite element analysis of RC beam-column joints. A numerical study carried out through a simulation on beam-column joints failed in flexure presented by experimental study. A verification procedure was performed on two joints by finite element analysis with ANSYS APDL. The verification with the experimental work revealed a good agreement through the load-displacement relationship, ultimate load, and displacement, and crack pattern. Also, the parametric study was implemented which including strengthening the concrete members by a variable ratio of steel fibers with normal ratios (0.5%, 1%, 1.5%, and 2%) and ratios of slurry infiltrated fiber concrete SIFCON (steel fibers up to 4%, 6%, and 8%) in addition to using of partial and full strengthening with and without stirrups. The test results revealed that steel fibers enhanced the flexural strength and ductility of the tested joint. Increase the ratio of steel fibers increased the flexural capacity by (101%, 153%, 177%, and 193%) for the four normal ratios of steel fibers respectively. SIFCON concrete ratios (4%, 6%m and 8%) enhanced ultimate strength by (521%, 802%, and 906%) respectively. The use of steel fibers reinforcement instead of steel rebar enhanced the ultimate load capacity by (101%) with large displacement. Full strengthening method by use of SIFCON presented pure flexural failure with cracks spread in the joint region but use the SIFCON concrete as a partial strengthening changed the failure mode to the shear failure.

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The study aimed to explore the possibility of strengthening RC corbels with many strengthening techniques. The research analyzed the RC corbels behavior under a wide range of variables. The theoretical study consisted of twelve models reinforced with GFRP bars with strengthening by steel plate. Finite element analysis with ANSYS APDL was used to verify five specimens. This research deals with a static nonlinear FE simulation to investigate the behavior of RC Corbels reinforced internally and externally. The verification with experimental work demonstrated a satisfactory agreement in the load-displacement relationship, ultimate load and displacement, and failure mode. The parametric study was implemented which included strengthening the four concrete corbels externally and four corbels internally by a steel plate in many configurations while the remaining three were modeled with varied compressive strength (30, 40, and 50) MPa. The external strengthening included the placing of steel plate externally around the corbel in a U-shaped form and partial strengthening by strips and bottom plate. The models with internal strengthening involved placing the steel plate internally instead of stirrups. The results discovered that the strengthening provided enrichments in the stiffness, ductility, and energy absorption by 37 %, 4 %, and 26 %. In addition, in the case of full external strengthening more than internal retrofitting, there is a maximum improvement in the cracking and ultimate load carrying capacity. The external strengthening was better than internal one due to the confinement effect of the concrete. The stress distribution and crack pattern were affected by the strengthening techniques and more cracks appeared in the corbels with external steel plates.