دانلود Retrofitting of Existing RCC Buildings by Method of Jacketing

Abstract

Many parts of the country have suffered earthquake in last three decades. In costal part of South India  faced  Tsunami.  In  first  three  earthquakes  it  was  found  that  many  of  damaged  structures were  build  in  non-engineered  masonry  techniques.  Unreinforced  masonry  structures  are  the most vulnerable during an earthquake. Normally they are designed for vertical loads and since masonry has adequate compressive strength, the structures behave well as long as the loads are vertical. When  such  a  masonry  structure  is  subjected  to  lateral  inertial  loads  during  an earthquake,  the  walls  develop  shear  and  flexural  stresses.  The  strength  of  masonry  under  these conditions often depends on the bond between brick and mortar (or stone and mortar), which is quite  poor.  This  bond  is  also  often  very  poor  when  lime  mortars  or  mud  mortars  are  used.  A masonry  wall  can  also  undergo  failure  in-plane  shear,  if  the  inertial  forces  are  in  the  plane  of the  wall.  Shear  failure  in  the  form  of  diagonal  cracks  is  observed  due  to  this.  However,  catastrophic collapses take place when the wall experiences out-of-plane flexure. This can bring down a roof and cause more damage. Masonry buildings with light roofs such as tiled roofs are more vulnerable to out-of-plane vibrations since the top edge can undergo large deformations. It is  always  useful  to  investigate  the  behavior  of  masonry  buildings  after  an  earthquake,  so  as  to identify any inadequacies in earthquake resistant design. Studying types of masonry construction, their performance and failure patterns helps in improving the design and detailing aspects. In previous earthquakes many R.C.C buildings have also collapsed and are found unsafe due to faulty  workmanship.  Many  other  causes  are  responsible  for  major  collapse  and  damage  to  the R.C.C structures. The review of the codes shows that there were five zones of earth quakes of Indian subcontinents,  But  its  revision  is  now  shoeing  four  zones  of  earth  quake.  Some  part  of  Gujarat  lies  in  zone  V which has largest severity of Earthquake. So as the districts that are located on the boundary of Gujarat – Maharashtra like Nasik, Dhule, Nandoorbar lye in zone III of earthquake zone, zone III is second largest zone of earth quake in India. Therefore it seems to be an compulsion to have an review of the old RCC structures (Likely have completed their service period) in and around Nashik for the structural behaviour to avoid future inconvenience.  This  project  is  just  a  similar  attempt.  A  health  building  in  the  heart  of  Nashik  city  is  being strengthened to overcome the future disorders. From the physical and experimental investigations it was concluded that the building either should be demolished or  at least should be retrofitted with suitable technique to increase its service life. It was then decided to implement RCC column jacketing technique due to its feasibility and ease for execution.  All the columns on both the floors are now suitably jacketed, the loose pockets of concrete that were  investigated during the test are reconcreted, the faulty slabs are completely opened and the rusted reinforcement is replaced with new reinforcement as per the design requirement. And the slabs are recasted with M25 grade of ready mix concrete.