COMPDYN 2013 4 th ECCOMAS Thematic Conference on Computational Methods in Structural Dynamics and Earthquake Engineering M. Papadrakakis, V. Papadopoulos, V. Plevris (eds.) Kos Island, Greece, 12–14 June 2013 EXPERIMENTAL CYCLIC TESTS OF HOLLOW PIERS WITH DIFFERENT RETROFIT STRATEGIES Pedro Delgado 1 , Patrício Rocha 1 , António Arêde 2 , Nelson Vila Pouca 2 , Aníbal Costa 3 and Raimundo Delgado 2 1 Instituto Politécnico de Viana do Castelo Apartado 574, 4901-908 Viana do Castelo, Portugal pdelgado@estg.ipvc.pt, procha@estg.ipvc.pt 2 Faculdade de Engenharia da Universidade do Porto R. Dr. Roberto Frias, s/n 4200-465 Porto, Portugal aarede@fe.up.pt, nelsonvp@fe.up.pt, rdelgado@fe.up.pt 3 Departamento de Engenharia Civil, Universidade de Aveiro Campus Universitário de Santiago, 3810-193 Aveiro, Portugal acosta@civil.ua.pt Keywords: experimental tests, retrofit strategies, RC hollow piers. Abstract. An experimental cyclic campaign of RC hollow piers has being carried out in the Laboratory for Earthquake and Structural Engineering (LESE) of the Faculty of Engineering of University of Porto (FEUP), aiming to establish, among other purposes, a strategy to ret- rofit RC hollow piers subjected to horizontal cyclic actions with axial load. The retrofit tech- niques intend to increase the shear strength and the ductility capacity through the application of CFRP sheets. The main objective of this paper is to evaluate and calibrate the efficiency of several retrofit solutions. The design criteria for the piers retrofit solutions and the different strategies for the practical application are presented, namely, the CFRP sheets for shear ret- rofit and CFRP base strip, with or without steel bars applied inside the hollow box, for ductil- ity improvement, being the different types of retrofit grouped out in order to understand the main benefits of each one. Results of the experimental campaign allow to discuss and con- clude about the efficiency of each retrofit solution, explicitly regarding the improvement of the shear strength and the ductility capacity. 2514