Abstract:
Carbon Fiber Reinforced Polymer (CFRP) strengthening technique had been shown
excellent performance in externally strengthening reinforced concrete (RC) elements
due to their superior properties compared to the alternative strengthening techniques.
A substantial number of studies have been done to study the behavior of externally
bonded CFRP strengthened RC elements. However, as per the knowledge, while most
studies have focused on the external strengthening of RC beams using CFRP, and very
few studies have focused on strengthening the pre-stressed beams and slabs.
Pre-stressed concrete is most popular building technique in construction buildings.
Steel corrosion is recognized as the most serious and dominant mechanisms of
deterioration for concrete structures. Subsequently, the capacity of the pre-tension
elements decreases after exposure to corrosion. NERD center slab system faces such
unacceptable losses in load carrying capacity, stiffness, and ductility due to severe
corrosion in pre-stressed beams. This study focuses on how CFRP can go for a load
increment after reaching its ultimate load carrying capacity.
The test procedure was arranged in two stages. The first stage testing was used to
show the performance/ behavior of composite slab specimen and pre-stressed beam,
with the application of load. The second stage of testing was carried out to make
comparison between the structural performance of retrofitted and strengthen
specimens. Specimens were selected for retrofitting after application of loading in
stage 1. The total of 12 specimens were exposed to the loading and behavior of each
of the specimen were observed. Specimens were selected as slabs and eight number
of them were composite slabs with or without shear links which have overall
dimensions equal to 1800 * 600 mm and other four were pre-stressed beams with
overall dimensions of 1800 mm in length. In this study, CFRP is proposed as the
economical solution which does not touch the structural integrity of the structure.
All the specimens were tested using universal loading machine. In stage 1, specimens
were loaded up to its ultimate failure. In stage 2, all the tested specimens were
retrofitted using CFRP. In total number of six specimens were used for retrofitting.
Another six specimens were also strengthened using CFRP before loading. In each
stage of loading several observations were done. Such as mode of failure, cracking
width distribution, ultimate load, and each composite panel's corresponding deflection
were also recorded.
In stage 1, flexural and shear cracks propagated in the pre-stressed beam and the beam
failed at the applied load of more than 50 kN. Stage 2 focused on the performance/
behavior of the retrofitted and strengthened specimen after application of CFRP. The
results from stage 2 showed a considerable reduction (nearly 20%) in loading of
retrofitted/ strengthened composite slabs compared to control specimens. Difference
in failure pattern is caused for this discrepancy in load demand of second stage. The
experimental results showed some satisfactory performance in regaining the lost
strength of the composite specimens due to corrosion.
Citation:
Ganewattha, C.K. (2023). Application of CFRP composite for sustainable solution of corroded slab system due to low nominal cover case study on nerd slab system [Master's theses, University of Moratuwa]. Institutional Repository University of Moratuwa. http://dl.lib.uom.lk/handle/123/22084