NON-LINEAR BEVAVIOR OF OLD STRUCTURES RETROFITTED WITH INNOVATIVE MATERIALS AND DEVICES

Huaco Cardenas G.; Jirsa J. · World Conference on Earthquake Engineering proceedings (2021)

Resumen

Old infrastructures are commonly used for university libraries since they represent for faculties and students as monument or special infrastructure which they should keep in use even after a severe earthquake event. To assess and retrofitted them is essential to remain these infrastructure safe also and more importantly the users. Two University libraries older than 50 year, one at Oregon USA and the other at Lima Peru, were structural assessed and proposed the retrofit of them using those innovative techniques. They consist to reinforce old structures with the application of innovative materials and devices such as carbon fiber reinforced polymer CFRP and mechanical splices. CFRP jacketing and anchors for columns, as well diagonal sheets for struts at wall were studied at laboratories having acceptable performance with the extension of ductility and preventing the sliding increasing shear force capacity too. Mechanical Splices provides continuity of the internal reinforcement when lap splices have short lengths which are inadequate to reach the yielding of the bars. Inclusion of behavioral models of new retrofit procedures into current Performance Based Seismic Design procedure (ASCE 41) for strengthening of existing or repaired damaged buildings was used. The models are used to perform a nonlinear static analysis of an existing structure in which the columns have been strengthened using CFRP materials and mechanical splices. The objective of this non-linear static analysis is to demonstrate how these methodologies of retrofit can be used in design. The retrofitted structures reach higher base shear capacity than the original structures. Besides, they are able to develop larger deformation than the as-built structure before the capacity drops. The use of CFRP materials in the reinforcement of structures over 50 years shows that it has a significant increase in capacity and a better response to an important earthquake, as well the use of mechanical splices. Retrofit of concrete walls with diagonal CFRP sheets and installations of CFRP anchors, is obtained better performance than reinforcement in columns with CFRP jackets. This shows that, in buildings over 50 years old with walls present, it is recommendable to reinforce the walls because it releases the greatest amount of seismic energy at the base of the building. Performance points were also obtained according to ATC 40 provisions, having demand curves by national seismic codes of each library and earthquake ground motion records. © The 17th World Conference on Earthquake Engineering.

Instituciones: Universidad Nacional de Ingeniería