STRENGTHENING OF TWO WAY -REINFORCED CONCRETE SLABS

Abstract

The occurence of cracks or distress in. R.C. structures is quite common these days. The distress may appear soon after the construction or at later date and may be caused due to structural or non-structural reasons. Experience has shown that if proper care is taken in the planning, design and construction of the building, the menace of cracking can be minimized if not totally avoided. The art of diagnosis of a distress and the rehabilitation of the distressed structures is becoming a highly specialized field in the areas of emerging technologies. If the cracks have appeared due to non-structural reasons, it merely requires to repair the building. However, in many situations, it is required to strengthen the existing members to safely transmit the design loads. Two commonly encountered reasons requiring strengthening of two way slabs are: (1) to permit overloading due to change of occupancy or (ii) to restore normal design strength of a slab laid in weak concrete due to bad workmanship and control at site. In the present study, differents techniques available for the-strengthening of two way slabs have been comparedd on a scientific basis and their relative efficacy investigated. Presently there is no procedure documented for the design of strengthening measures, and towards this a rational basis for such a design, based the limit state approach, has been proposed. The results of the experimental study and the investigation have established that it is now possible to design for such strengthening with confidence. The strengthened slabs have exhibited behaviour similar .to the normal slabs with respect to'both over loading and ductility. r