ber-reinforced polymer (FRP) for the seismic retrofit  of existing reinforced concrete (RC) structures were assessed on a full-scale three-story  framed  structure。 The structure, designed only for gravity loads, was subjected to a bi-directional pseudo-dynamic (PsD) test at peak ground acceleration (PGA) equal to 0。20g at the ELSA Laboratory of the Joint Research Centre。

The seismic deficiencies exhibited by the structure after the test were confirmed by post-test assessment of structural seismic capacity performed by nonlinear static pushover analysis implemented on the lumped plasticity model of the structure。 In order to allow the structure to withstand 0。30g PGA seismic actions, a retrofit using glass fiber-reinforced polymer (GFRP) laminates was designed。 The retrofit design was targeted to achieve a more ductile and energy dissipating global performance of the structure by increasing the ductility of columns and preventing brittle failure modes。 Design assumptions and criteria along with nonlinear static pushover analysis to assess the overall capacity of the FRP-retrofitted structure are presented and discussed。 After the retrofit execution, a new series of PsD tests at both 0。20g and 0。30g PGA level were carried out。 Theoretical predictions are compared with the main experimental outcomes to assess the effectiveness of the proposed retrofit technique and validate the adopted design procedures。 Copyright q 2007 John Wiley & Sons,   Ltd。72191

KEY WORDS:    GFRP; full scale; RC; seismic retrofit; biaxial bending; nonlinear pushover    analysis

1。 INTRODUCTION

The main hazard in southern European countries consists in the number of existing reinforced concrete (RC) structures which are under-designed or designed under outdated regulations or con- struction practice。 Casualties and losses are mainly due to deficient RC buildings not suitably

designed for earthquake resistance。 In the framework of the SPEAR (Seismic PErformance As- sessment and Rehabilitation) research project, specifically targeted to evaluate current assessment and rehabilitation methods and at development of new assessment and retrofitting techniques, a series of full-scale bi-directional pseudo-dynamic (PsD) tests on a torsionally unbalanced three- story RC framed structure was carried out。 The SPEAR structure represents a typical building in most earthquake-prone areas of Europe; thus, it is characterized by plan-irregularity, poor local detailing, scarcity of reinforcement, insufficient confinement and weak joints combined with older construction practice。

The full-scale RC structure was subjected to a bi-directional PsD test in the ELSA laboratory of the Joint Research Centre (JRC) in Ispra (Italy) under the Montenegro Herceg Novi record scaled to a PGA of 0。20g。 Subsequently, a post-test lumped plasticity model of the structure was implemented to assess the theoretical seismic capacity of the structure。 Since both theoretical and experimental results showed that the ‘as-built’ structure was unable to withstand a larger seismic action, a retrofit intervention by using FRP laminates was designed。 Once the design of the glass fiber-reinforced polymer (GFRP) retrofit was provided, the structure was subjected to a new series of two tests with the same input accelerogram selected for the ‘as-built’ specimen but scaled to a peak ground acceleration (PGA) value of 0。20g and 0。30g, respectively。

The opportunity of using composite materials as an effective technique for the seismic retrofit of RC frames is herein evaluated。 The background, philosophy and calculation procedures followed to carry out the design of the GFRP retrofit are presented along with the comparison between the experimental and theoretical performance of the ‘as-built’ and retrofitted structure。

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