Tesis doctoral de Francesc Puigvert Cobos
In prestressed structures subjected to corrosive environments, consideration is being given to replacing the steels tendons with non-corrosive tendons. In this respect, fibre reinforced polymer (frp) materials are a durable option in the design of prestressed concrete structures for use in corrosive environments due to their high mechanical properties, light weight and high resistance to corrosion. However, one of the challenges associated with this option lies in developing a suitable anchorage system for frp tendons. in the present work, the mechanical response of circular adhesively bonded anchorages for frp tendons has been investigated under quasi-static, time-dependent and fatigue loading. This has been achieved through a combination of an experimental campaign and finite element modelling work. experimental quasi-static tests of adhesively bonded anchorages were undertaken with failure occurring in the adhesive-tendon interface. The main variables assessed were the adhesive thickness and the bonded length. In order to investigate the quasi-static response of the bonded anchorage and its failure mechanism, a campaign of numerical modelling was carried out with different material models of increasing complexity for the adhesive layer. A cohesive zone model with progressive damage in the bonded joint was found to be in reasonable agreement with the experimentally recorded data. additionally, an analytical formulation was developed (and validated against experimental data) with the aim to provide an approximate shear stress distribution in the bonded joint for circular anchors with adhesives which mainly behave linearly elastic up to failure. the adhesively bonded anchor for frp tendons was also investigated under the time-dependent phenomena. Creep tests on single lap joints (sljs) were conducted in order to obtain an experimental creep law whereas stress relaxation tests were conducted on adhesively bonded anchorages to study the load loss in time. furthermore, the restressing technique was assessed during the stress relaxation tests by restressing the specimens, to the original tensioning load, when the load loss was stabilised and constant. It was found that the restressing technique allows for the working load of the composite tendon to be reached with a minimum load loss. a visco-plastic material model, based on the bailey-norton law, was calibrated with the experimental data obtained from the creep tests and utilised to predict the creep time to failure of sljs and anchorages. The creep damage was modelled by degrading the plastic yield stress of the adhesive. The viscoelastic model was also used to predict the load loss of the anchors under the stress relaxation phenomenon. The predicted load loss results were found to be in good agreement with the experimental results recorded. finally, the fatigue response of the bonded anchorages was investigated. Anchorages with four different adhesive thicknesses were evaluated under three constant amplitude fatigue loadings. The experimental fatigue response of adhesively bonded anchorages was discussed and an experimental load-life average curve was obtained for all the anchorages. the fatigue behaviour was also predicted using finite element analysis. A multi-linear traction-separation cohesive zone model was implemented at the adhesive-tendon interface. The cohesive law obtained in the quasi-static analysis was utilised in the fatigue model. The fatigue damage model utilised in this research was based on the degradation of the cohesive elements taking into account the fatigue damage evolution. The damage model was able to successfully predict the fatigue damage evolution and failure life experimentally observed. from the experimental and numerical work conducted in this investigation, the most relevant recommendations are proposed for a potential use of adhesively bonded anchorages for cfrp tendons in prestressing applications.
Datos académicos de la tesis doctoral «Analysis of circular bond-type anchorages for prestressing composite rods under quasi-static, fatigue and time-dependent loads«
- Título de la tesis: Analysis of circular bond-type anchorages for prestressing composite rods under quasi-static, fatigue and time-dependent loads
- Autor: Francesc Puigvert Cobos
- Universidad: Politécnica de catalunya
- Fecha de lectura de la tesis: 20/10/2014
Dirección y tribunal
- Director de la tesis
- LLuis Gil Espert
- Tribunal
- Presidente del tribunal: Luis Torres llinas
- dora Foti (vocal)
- (vocal)
- (vocal)