Executive Summary : | Objective: India is witnessing a tremendous increase in demand for energy which involves creation and maintenance of critical infrastructure viz., power plant structures, transmission line and communication towers. On the other hand, seismic resilience of existing bridges is of primary concern which warrants the timely seismic strength assessment and retrofitting measures in a performance based environment. It is a challenging task to ensure the functionality and life enhancement of ageing critical infrastructure due to following reasons: (1) aged lifeline structures are designed for loads as per earlier standards, susceptible for deterioration/distress due to ageing and exposure to aggressive environments (2) There is an increase in demand due to rapid growth in traffic volume and for existing bridges (3) Increased consumption of electricity and demand on energy generated from power plant structures (4) Additional load due to voltage clause up gradation for transmission line towers and installation of additional antennae for communication towers. Main objective of this project is to develop methodologies to assess the existing strength of critical lifeline structures and to propose a cost effective and suitable retrofitting solution involving appropriate repair material and retrofitting methodology in a performance based environment based on expertise acquired through numerical and experimental research carried out at CSIR-Structural Engineering Research Centre. Summary: Bridges, power plants and transmission/communication line towers are essential lifeline structures required for effective functioning of day-to-day activities of a community. Design standards are revised from time-to-time and the increase in demand due to increase in population, urbanization and revision of design procedures and lateral loads pose challenges on the functionality of existing infrastructure. To maintain operation level of the ageing lifeline structures existing strength needs to be assessed as against the demand specified by state-of-the-art design standards, aggressive environment, accounting for the distress/deterioration of the structure and performance-based retrofit strategies have to be developed. It has been reported recently that, over one hundred bridges are susceptible for damage due to future earthquakes because of their current service conditions. This can have huge economic implications in terms of transport interruption and cost involved for replacement. As a part of this project, procedures for quantification of seismic safety of existing bridges before and after retrofitting with passive control devices will be developed and demonstrated in probabilistic performance based environment through numerical modelling using the properties of an existing bridge. Further, in this project, the feasibility of implementing local and global retrofit/selective weakening technique and addition of response control devices viz., semi-active control, isolation will be demonstrated based on numerical and experimental study for power plant structures in a performance-based platform. The major cause for premature deterioration and failure of concrete structures is due to the lack of understanding about the root cause for the deterioration and also poor selection of appropriate repair material and effective repair methodology that can be implemented at site. In this project, a comprehensive and effective repair scheme is proposed to be evolved to improve the intended quality, integrity and water tightness/permeability of poor quality concrete for power plant structures. There is a need to assess the actual wind speed exerted on transmission line and communication towers during failure and to develop base line model of the existing towers for its condition assessment. There is a necessity to examine the cause of the failure of tower and propose cost effective strengthening scheme for existing members of the tower. As a part of this project, strengthening techniques adopted presently by the tower industry will be evaluated and rationalized through proper theoretical and experimental studies. Further, performance-based retrofitting strategies are proposed to be developed for the life enhancement of the existing towers. |