Experimental testing was done to investigate the flexural behaviours of internal roof beam-column connections. Four specimens were studied under static loads, one of which was specified as a reference reinforced concrete beam-column connection with regular bars as a conventional reinforcement for beam and column. The other specimens featured cold-formed steel plates with the equivalent area to regular bars as reinforcement, with square steel tube cross-sections filled with concrete used for columns. The results showed an increase in load carrying capacity and toughness for the experimental specimens as compared with conventional reinforcement beam-column connection. The concrete prevented local buckling of the cold-formed steel sections and improved the flexural bending capacity.

The present study includes an experimental investigations for the behavior and the load carrying capacity of hybrid beam-column connections subjected to static and repeated loading condition. The goals were to evaluate the effect of using slurry infiltrated fiber concrete (SIFCON). Experimental program consists of testing six beam-column connections, two of them casted with normal concrete and the other using SIFCON in crtical section in addation to normal concrete. Also, the program testing three of connection subjected to static load and the similar other subjected to repeated loads. Results show an improve in flexural behavior for specimens with SIFCON as compared with normal concrete under static and condition, on the other hand, the reduction in flexural strength when was exposed to repeated loads in comparison with that under static loads reach 2.6% at hybrid connection. While, the reduction was increased to 5.1% for the specimen without SIFCON.

Strengthening and rehabilitation by confinement technique of reinforced concrete columns was investigated. The columns were confined by external steel collars. Behavior and failure load of columns were experimentally investigated. Results show thatConfinement in concrete column has improved its strength and ductility. Effect of confined area, size of collar and compressive strength of concrete on strengthening was investigated .Confined areahad significanteffect on the failure loadfor strengthened specimens and had more effective on the failure load for repaired specimens. The confinment hadclearer effect with low compressive strength of concrete.The result show an increase in ultimate axial load reach to (12.36 –56.04%)for strengthening columns and (47.5 –96.7%)for reaparingcolumns