Seismic Assessment, Repair and Retrofit of Existing Corroded Structures Using UHPC Jacketing

The bulk of our developed environment was constructed in the mid to late 20th century, when design codes did not address the importance of ductility and confinement, placing most of today’s concrete infrastructure in danger in case of a seismic event. Current assessment guidelines such as Eurocode 8-III or ASCE 41-17 take the lack of detailing into consideration in the assessment procedure however, they do not address a major concern, reinforcement corrosion. In this dissertation, modifications to current assessment guidelines were proposed and validated in order to take corrosion damage into consideration. Expressions for residual material properties as well as residual mechanical properties of columns were proposed with reinforcement mass loss being the only variable. The viability of using UHPC as both a strengthening and protective material against corrosion was studied in this dissertation. It was found that UHPC fully mitigates corrosion in case no service cracks were present and significantly reduces the corrosion rate in case of cracks between 0.5mm and 2mm were present. The final portion of the dissertation deals with repair and strengthening of corroded lap-spliced columns. Six lap-spliced columns designed based on pre-1970s design standards were constructed and subjected to artificial corrosion. Some of the specimens were tested without any prior strengthening intervention to simulate an earthquake damaging an existing column. They were then repaired using UHPC jacketing and re-tested under cyclic displacement reversals while other columns were strengthened after corrosion and then tested. This was done in order to study the increase in strength and ductility in case the strengthening was done prior to or after seismic activity. The results show a significant increase in strength and ductility of the columns, imparted by thin UHPC jackets replacing the conventional concrete cover.