Strengthening of R.C Beams Under Torsion

There are many examples for reinforced concrete sections subject to torsional moment such as Spiral stair case, Pre caste spandrel beams Eccentrically loaded box girders bridges .etc In some of the above mentioned cases the structural member can subject to torsional moment larger than the designed one . In this case it is required to increase the torsional resistance capacity of the member by a suitable strengthening technique to improve the torsional . resistance and make it able to resist the applied torsional loading. In this study a thirteen test specimens were cast and divided to four major groups , the first group included three beams as reference beams ( B 1 , B2 & B3 ) with the same dimensions but with different steel reinforcement to investigate the effect of the beam reinforcement change in the torsional behavior under the same cases of loading. The second, third and fourth groups included ten beams ( B4 , B5, ...... .... & B 13 ) with the same dimensions and steel rei n j()l-cement of the main reference beam (B 1) after strengthening th~l1l by different strengthening techniques . <The beams were tested by a new test set - up to avoid the problem that the liberator machine has also a compression load pine. To create torsional loading in the test zone of the bcams with small bending moments and free from shearing forces in such a way that the torsional moment was the main factor affects in the beam behavior . The test specimens were cast in a certain form with carefully calculatedI )imct1siot1s to ~iv(’ the required loads and by used an inverted U shape .1\ l’l frame (’d.’ry rigid) to transfer the compression load pine to torsional I I”dlll~ \\ ilh hcnding moments rOllr mall1 materials were chosen to be used in strengthening of the 10 beams. 1 ;- Carbon fiber sheets ( 5 cm width) ( used in strengthening 3 beam) 2 ;- Fiber Glass sheets ( 5 cm width) ( used in strengthening 3 beam) 3 :- Steel Plates (5 cm width) ( used in strengthening 2 beam) . 4:- Galvanized Steel Mesh ( used in strengthening 2 beam one of them with steel plates 5 cm width as stiffeners ) . five main strengthening techniques were chosen to be applied in this thesis 1 ;- Closed External stirrups 5 cm width ( 5 / m’ ) 2 ;- External stirrups 5 cm width has II shape (5 / m’ )3:- External two longitudinal sheets / plates (one in the mid height of each side) .4:- External stirrups 5 cm width has U shape (5 / m’ ) .