Structural Assessment and Retrofitting of Old Buildings Exibiting Disparity in Their Design and Implementation

Abstract

Reinforced concrete buildings are widely used in seismic regions due to their lower construction cost and ductile behavior under lateral loads. However, the seismic performance of these buildings is highly dependent on their design and implementation. Seismic hazards pose a significant risk to structures in earthquake prone areas, and it is essential to ensure that the buildings are constructed with adequate seismic resistance. In the recent past, earthquakes have caused significant damage to poorly constructed and designed reinforced concrete buildings, dictating the need to improve the seismic performance of such types of buildings. Past survey of buildings reveals huge disparity between the design and its implementation for reinforced concrete buildings in term of concrete strength, clear cover, concrete mixing, water cement ratio, stirrups spacing, lapping zones, hook angles, bar sizes etc. Furthermore, it is noted that several old buildings were constructed either without any seismic provisions using outdated codes or just based on mason’s experience. Such buildings are susceptible and vulnerable to seismic hazards which may result in collapse and loss of life. This research focuses on assessment of an existing (old building) and one prototype/model building by incorporating design and implementation disparity issues. To determine their performance, their static push over analysis (POA) and dynamic (NLTHA, IDA) analyses are conducted. Analysis results are then utilized to rehabilitate and retrofit these buildings to improve their seismic performance. Results show that by adopting selected retrofitting techniques, old buildings with poor design construction quality history can be rehabilitated to withstand seismic forces, thus saving precious lives.