OPTIMUM CFRP LENGTH FOR THE HOGGING MOMENT ZONE (HMZ) OF CONTINUOUS RC T-BEAMS

Yıl 2017, Sayı: 1, 158 - 177, 09.11.2017

Mohammad Mohie Eldin Ahmed M. Tarabia Rahma F. Hasson

Öz

Carbon
fiber reinforced polymer (CFRP) laminates were proved as very effective method
for either repairing or strengthening of used structures. However, the
literature has no enough information about the behavior of RC continuous
(two-span) T-section beams strengthened with CFRP laminates, especially in
hogging moment zone (HMZ). This paper examines the effect of CFRP laminates
lengths, used for strengthening of the hogging moment zone, upon the behavior
of such beams, to determine the optimum strengthening length. 3-D theoretical
models using the Finite Element (FE) Package ANSYS are used. The paper contains
the main details of the FE modeling process; used element types, material
properties, meshing, yield criterion and boundary conditions. The results of the
proposed FE model were compared with those of a previous experimental research
and very good agreement was found between both FE and experimental results.
Three parameters were used in the parametric study; CFRP length, CFRP
thickness, percentage ratio of the steel reinforcement (different diameters for
reinforcement steel bars). To examine the effect of changing CFRP strengthening
lengths, different types of results for the proposed parametric study were
obtained for better understanding of behavior. Adding to this, these results
were compared and analyzed at different stages of loading between first
cracking of the RC studied T-beams and their failure. These results include
load-deflection curves, bending moment diagrams, stresses and strains of the CFRP
laminates, stresses and strains of steel reinforcement bars, redistribution of
moments, energy dissipation, ductility, shear (bond) stresses and failure modes
of the studied beams. It can be concluded that changing CFRP length in the HMZ
is very effective upon the overall behavior of T-section continuous RC beams.
This effect begins after first crack and considered as effective after the
yielding of upper steel bars. Increasing the lengths of CFRP laminates
increases capacity, ductility and energy dissipation of strengthened beams in
the hogging moment zone. Also, it improves utilizing of upper steel bars and
redistribution of moments between sagging and hogging moments. Practically,
Design-Codes of using CFRP in strengthening of structures concern only with
both CFRP strengthening length and its corresponding anchorage length. As a
result, definitions of both optimum CFRP strengthening length and CFRP
anchorage length were expressed. Finally, criteria to calculate both of them
were concluded

Anahtar Kelimeler

ANSYS, CFRP, optimum length, rc beam

Kaynakça

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