Experimental Study And Theo-Retical Analysis On RC Two-Way Slabs Strengthened With GFRP Strips

There are about five billion square metres of buildings in our country now, half of which need to be strengthened or converted. With the development of economy and social requirement, technologies for strengthening RC elements of structure are developing very quickly.There are several means for strengthening RC two-way slabs, in which the means of bonding FRP strips is being applied more and more extensively, because it can be practiced most easily and quickly, and will not reduce the space of buildings. But the research about strengthening RC elements with FRP have mainly been taken on beam, column, one-way slab and cantilever slab, and scarcely on RC two-way slab.The experimental study is presented for RC two-way thick slab strengthened with GFRP strips at partial dead load. The cracking behavior, deformation, strain of steel bar, strain of FRP, ultimate load, failure progress, failure characteristic, bearing capacity, stiffness, load-steel strain relationship and load-FRP strain relationship are studied. The conclusion is that strengthening RC two-way slab can improve cracking behavior, deformation behavior, stiffness and ultimate bearing capacity.At present the design approach for strengthening RC beam with FRP strips is used for strengthening RC slab, which is approximate and weak. The lineal model, the fan model and the flexure-punching model are respectively adopted to calculate ultimate bearing capacity. Both of the lineal model and the fan model belong to the plastic hinge theory. In the flexure-punching model it is assumed that the RC slab has some flexural deformation, then the punching cone forms and separates, which is in accordance with the experimental phenomenon and the punching failure mechanism of RC slab. By discounting the flexural bearing capacity in plastic hinge theory, simplying the punching bearing capacity calculation in plastic theory, and then adding them up, the calculation approach for the ultimate bearing capacity of RC slab in flexure-punching model is performed.The model of RC two-way slab strengthened with GFRP strips is performed by the finite element method (FEM) program, ANSYS. The analytical and experimental results about mechanical behavior of RC slab are compared. The factors that determine the result of strengthening RC floor slab with GFRP strips are performed by finite element method in the last part.