Effect of retrofitting on beam-column joints

Abstract

During the serviceable life of R.C.C structures they are found to show evidence of distress due to various reasons. To bring such structures back to their functional/serviceable condition these structures need urgent attention and enquiry for finding out reasons of distress along with appropriate remedial treatments so as to increase serviceable life of such structures and bring them back to their functional use. So the process of retrofitting involves upgrading and enhancing the strength of deficient structures and their components. Safety of life is a priority issue to be addressed in process of retrofitting. For preventing injury and death of occupants and for preventing damage to structural components and collapse of structure as a whole, some retrofitting techniques try to deal with the issue to avoid damage. As a retrofitting technique, ferrocement technique is one of commonly used procedure of improving strength which is due to their good durability, less cost, easy availability and ease in application with requirement of intricate formwork. Application of ferrocement can be quickly done on the damaged structural elements without any requirements of chemical bonding agents. Also the ferrocement application requires less skill labour in comparison to other retrofit solutions available these days. Ferrocement is light in weight, easy to construct & have low self weight which is why it is preferred to other techniques of retrofitting. It has higher tensile strength then R.C.C. Also the thickness of ferrocement is a fraction of thickness of R.C.C. structural elements which makes it a complementary material for prefabricated structures. In the present study six R.C.C. Beam column joint specimens were casted. Two controlled specimens were initially stressed to ultimate load (100% damage) and other four specimens are stressed to prefixed percentages of ultimate load. All six specimens were then retrofitted using ferrocement for upgrading the strength of Beam column joints in flexure and shear. Chicken wire mesh is wrapped all around the specimen. From the study it is observed that retrofitted specimens has shown considerable decrease in deflection if we compare them to controlled specimens. Also the percentage decrease in deflection for specimens subjected to 75% and 50% of ultimate loads is considerably higher to those specimens which are subjected to 100% damage i.e. ultimate load.