DEFLECTION CONTROL IN RCC BEAMS BY USING MILD STEEL STRIPS (AN EXPERIMENTAL INVESTIGATION)

Abstract

It is well recognised that in modern practice, structural failures are all too common in terms of Serviceability and are relatively rare in terms of Safety. Adoption of limit state of design and higher grades of concrete and steel in modern RCC structures has led to overall thinner member sections and high stress levels at service loads. These in turn have resulted in larger deflections, crackwidths, vibrations etc. In particular, it is the Serviceability Limit state of ‘Durability’ that calls for particular attention, because ‘Deflection’ is a very important criteria need to be taken into account. Due to architectural constrain generally depth of beams are restricted, that leads to more deflection in a beam . An attempt has been made through this project to check the feasibility and efficiency of Mild Steel sheets used as a composite material with traditional RCC beams to modify its serviceability criteria. MS Sheets are used due to their economy, durability and are also easily available in large variety of cross-sections (gauges). MS sheets also have the property of being cast to any shape without much need of significant formwork. The composite construction has an edge over the conventional reinforced concrete material because of its ease of construction, thinner sections as compared to RCC, efficient bonding with concrete due to its large surface area & high tensile strength (per unit weight) which makes it a favourable material for prefabrication also. The ill effect of corrosion is reduced here as the MS Strips are embedded into the concrete material, thus less prone to exposure and also has no aesthetic issues. Extra care can be taken by providing coating also. The main aim of this project is to increase the stiffness of beam in order to control the deflection. Mild steel sheets and strips of varying thickness (gauges) were embedded into traditional RCC beam vertically along side faces in longitudinal direction. This increases both moment of inertia as well as modulus of elasticity of beam, thus increasing its stiffness and controlling deflection. The test results are compared and it has been observed that deflection is controlled by about 30% and strength is increased by about 25% in MS-strip composite beams as compared to control beam.