Techno Press
Techno Press

Structural Engineering and Mechanics
  Volume 8, Number 6, December 1999 , pages 531-546
DOI: https://doi.org/10.12989/sem.1999.8.6.531
 


Long-term deflection of high-strength fiber reinforced concrete beams
Ashour SA, Mahmood K, Wafa FF

 
Abstract
    The paper presents an experimental and theoretical study on the influence of steel fibers and longitudinal tension and compression reinforcements on immediate and long-term deflections of high-strength concrete beams of 85 MPa (12,300 psi) compressive, strength. Test results of eighteen beams subjected to sustained load for 180 days show that the deflection behavior depends on the longitudinal tension and compression reinforcement ratios and fiber content; excessive amount of compression reinforcement and fibers may have an unfavorable effect on the long-term deflections. The beams having the ACI Code\'s minimum longitudinal tension reinforcement showed much higher time-dependent deflection to immediate deflection ratio, when compared with that of the beams having about 50 percent of the balanced tension reinforcement. The results of theoretical analysis of tested beams and those of a parametric study show that the influence of steel fibers in increasing the moment of inertia of cracked transformed sections is most pronounced in beams having small amount of longitudinal tension reinforcement.
 
Key Words
    beams (supports), deflection, effective moment of inertia, flexural rigidity, high-strength concrete, immediate (instantaneous) deflection, long-term (time-dependent) deflection, reinforced concrete, steel fibers
 
Address
Ashour SA, King Abdulaziz Univ, Dept Civil Engn, Jeddah 21413, Saudi Arabia
King Abdulaziz Univ, Dept Civil Engn, Jeddah 21413, Saudi Arabia
 

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