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Abstract
Different methods and materials are used to increase the bearing capacity of the structures or to repair the building damages. Different materials are used in the repair and strengthening works such as cement based materials with and without admixtures, adhesives, grouts, steel or plastic fibers, reinforced plastics, steel plates and rolled sections. The current study aims to identify the factors related to the different phases of the construction process and the considerations that should be satisfied in order to guarantee the structural safety during the service life of concrete structures. The study involves extensive experimental testing to evaluate different strengthening configurations utilizing both traditional and advanced materials and techniques in order to improve the structural performance of concrete solid slabs.
The investigated techniques included the use of : externally bonded GFRP strips, added steel reinforcement along with a new concrete cover, added GFRP reinforcement along with a new concrete cover, ferrocement. Those techniques are intended to increase the flexural capacity of the test specimens. The efficiency of the different strengthening techniques is to be evaluated based on the test results in terms of measured deformations and recorded cracking and ultimate loads. All slabs were tested to ultimate load at the middle point of the
slabs. The load was applied and increased by using a hydraulic jack of a
maximum capacity of 10 tons supported by arigid steel frame. The initial crack load, the crack propagation for the tested slabs at different loading stages, deflections and failure loads were recorded.
Based on the experimental results it could be concluded that Both initial and post–cracking stiffness can be increased by the described strengthened techniques due to the increase of the total slab thickness or restricting the development of cracks externally bonded GFRP strips. The use of GFRP reinforcing meshes as internal extra added reinforced might not be expected to cause significant increase in the load carrying capacity compared to the control slab.
The use of externally bonded GFRP strips can better be used to improve the serviceability performance in terms of cracking characteristics and post-cracking. Compared to GFRP reinforcing meshes, the conventional steel meshes provided significantly higher ultimate loads with sufficient ductility associated with flexure failure. In case of square slabs, the added steel meshes provided signifactly higher ultimate loads when aligned at an angle of 45 degrees with respect to the original mesh inside the strengthened slab.
The use of ferrocement, including the use of expanded wire mesh and a high quality mortar cover, provided a superior structural behavior in terms of both serviceability and ultimate load criteria.