| Abstract: |
-Concrete structures reinforced with normal steel bars has questionable durability inaggressive environments. They suffer corrosion, cracking, spalling and deterioration thatrequire expensive repair and continuous maintenance. Moreover, due to its high demand,the row steel abundance is decreasing year after year. Therefore, researchers have beenlooking for a corrosion resistant alternative to replace the traditional steel reinforcing barsthat has a comparable competence. Reinforcing bars which manufactured from compositematerials made of resin impregnated fibers (FRP) promise a reasonable substitute toconventional steel bars in concrete structures in aggressive environments. The behavior ofconcrete beams reinforced with FRP bars under torsion is not well understood, andresearches in the subject are needed to help designers and structural code officials. Thisstudy introduces an experimental investigation of the torsional behavior of FRP-reinforcedconcrete beams.There are many examples representing the reinforced concrete beams subjected totorsional loadings, these structures including spiral stair case, pre caste spandrel beams andeccentrically loaded box girders bridges ... etc, for concrete elements reinforced by normalsteel bars they could have too much problems and suffer premature deterioration in anaggressive environments, when exposed to chlorides, water and / or sulfates in marineareas, hot and salt laden environment (e.g. Arabian Gulf); marine and sea frontenvironment (e.g. Alexandria and read sea areas), Hence, steel reinforced concretestructures are unfavorable in such environments, as they suffer from corrosion, cracking,spalling and loss of strength ~rthermore their serviceability and durability are impaired thematter which require an expensive repair and continuous maintenance to keep the buildingstrengthened, this continuous repairs could required too much time, efforts and money.An experimental program was carried out in this study including eighteen testspecimens divided to six groups, casted and tested. Group (1) included four referencebeams (Bl,B2,B3&B4) reinfroced by normal steel bars with different cases, each one ofthem represented a torsional resistance case for the beam. Group (2) included three beams(B5,B6&B7) contained the normal steel bars as main longitudinal reinforcement with asteel stirrups & additional GFRP reinforcement. Group ( 3 ) included two beams(B 15&B 16) contained GFRP bars as main reinforcement with steel stirrups and additionalnormal steel stirrups. Group (4) included three beams (B12,B13&BI4) contained GFRPbars as main reinforceGroup (5) included fouand additional reinfon(B 17) contained steeladditional CFRP reinflongitudinal reinforcemAll beams wereto avoid the problem thmoments and free fromThe test specidimensions to give the nrigid) to transfer the eoAn anlytical stud’IFEM using commerciaprogram results, the metin the field of continuudivision of the domain iField function parametersnodal point. The goveminnumber of equations whicwhole domain.
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