Effect of Percentage of Reinforcement on Beams Retrofitted with Ferrocement Jacketing

Abstract

Almost all the structures whether industrial, commercial or housing are constructed of RCC. There structure fare nicely under normal circumstances, but in the event of major earthquakes, higher load imposition etc. the structure may suffer permanent damage. This poses a more difficult scenario for a structural engineer than constructing a new building. This is due to number of restraints an already constructed building throws up like non engineered construction, wear & tear etc. instead of torning apart the structure one can strengthen the deficient structural elements of the structure. Thanks to the advancement in technology with the help of non-destructive testing one can easily identify such deficient elements. Once identified the best way out is to retrofit such elements. Retrofitting is different from repair or rehabilitation. It is basically a process of strengthening and enhancement of the performance of deficient structural elements in a structure or of the structure as whole. Retrofitting of deficient buildings can be done by increasing the strength, stiffness and/or ductility of its specific constituent elements or of the whole building. For any building, depending upon the requirement, a combination of the above may also be selected. Retrofitting of individual members or elements is referred to as local retrofitting. A civil engineer is not really spoilt for choices when it comes to retrofitting, he has to keep in mind a number of options before embarking on the work of retrofitting. The options available include Glass Fibre Reinforced Plastic or GFRP, Carbon Fibre Reinforced Plastic or CFRP or Ferrocement. He has to maintain a balance between aesthetic, availability, ease of working & above all economy. Ferrocement jacketing though lacks a bit in the aesthetical part but it wins by leaps & bounds in all other considerations. The reason for this is it is readily available, is easy to work with and is not even a quarter as costly as GFRP or CFRP. The endeavour of our present study is to observe the effect of different percentage of tensile reinforcements on the behaviour of beams retrofit with ferrocement jacketing. The effect of percentage increase in tensile reinforcement vis-à-vis the percentage increase in ultimate load carrying capacity is studied. Also the deflections of retrofitted and non retrofitted beams are compared at different stress levels. The results shows an increase in load carrying capacity of retrofit beams though the increase varies with percentage of tensile reinforcements. The percentage increase in load carrying capacity is maximum in case of two bars of 8 mm dia as tensile reinforcement. The deflections also decreased considerably with the increase in percentage of tensile reinforcement.