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Thomas Keller

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Publications associées (309)

Total light transmittance of glass fiber-reinforced polymer laminates for multifunctional load-bearing structures

Julia De Castro San Roman Fest, Thomas Keller, Andreas Schueler, Anastasios Vassilopoulos, Carlos Pascual Agullo

The total light transmittance of hand lay-up glass fiber-reinforced polymer laminates for building construction was investigated with a view to two architectural applications: translucent load-bearing structures and the encapsulation of photovoltaic cells ...

SAGE Publications2014

FRP-balsa composite sandwich bridge deck with complex core configuration

Julia De Castro San Roman Fest, Thomas Keller, Anastasios Vassilopoulos, Michael Osei-Antwi

The aim of this work was to investigate to what extent the performance of a glass fiberreinforced polymer (GFRP) sandwich slab-bridge with uniform high-density balsa core could be improved in terms of structural efficiency and weight thanks to a more compl ...

2014

GFRP-balsa sandwich bridge deck: Concept, design and experimental validation

Julia De Castro San Roman Fest, Thomas Keller, Michael Osei-Antwi

The concept, design and experimental validation of the new Avançon Bridge in Bex, Switzerland, are described. The lightweight glass fiber-reinforced polymer (GFRP) sandwich bridge deck adhesively bonded to steel girders reduced the traffic disruption perio ...

2014

Structural limits of FRP-balsa sandwich decks in bridge construction

Julia De Castro San Roman Fest, Thomas Keller, Michael Osei-Antwi

The span limits of two glass fiber-reinforced polymer (GFRP) bridge concepts involving GFRP-balsa sandwich plates are discussed. The sandwich plates were either used directly as slab bridges or as decks of a hybrid sandwich-steel girder bridges. In the lat ...

International Association for Bridge and Structural Engineering2014

Thermal performance evaluation of fiber-reinforced polymer thermal breaks for balcony connections

Julia De Castro San Roman Fest, Thomas Keller, Anastasios Vassilopoulos, Kyriaki Goulouti

The potential effects of high-performance fiber-reinforced polymer thermal breaks for balcony connections on the thermal losses and heating needs of a typical residential building in Switzerland were investigated. In an optimized form, these new thermal br ...

Elsevier2014

Light diffusion in GFRP laminates for building construction

Julia De Castro San Roman Fest, Thomas Keller, Andreas Schueler, André Gabriel Kostro, Carlos Pascual Agullo

The light diffusion of hand lay-up glass fiber-reinforced polymer (GFRP) laminates was investigated with a spectrophotometric set-up using an integrating sphere. Reinforcement weights of the laminates ranged from 410 to 3280 g/m2 and fiber volume fractions ...

2014

Creep behaviour of sandwich panels with rigid polyurethane foam core and glass-fibre reinforced polymer faces: Experimental tests and analytical modelling

Thomas Keller, Mário Alexandre De Jesus Garrido

This paper presents experimental and analytical investigations about the creep behaviour of sandwich panels comprising glass-fibre reinforced polymer faces and rigid polyurethane foam core for civil engineering applications. A full-scale sandwich panel was ...

SAGE Publications2014

Fracture in complex balsa cores of fiber-reinforced polymer sandwich structures

Julia De Castro San Roman Fest, Thomas Keller, Anastasios Vassilopoulos, Michael Osei-Antwi

Fracture in the complex balsa cores of fiber-reinforced polymer (FRP) sandwich beams was analyzed. The cores were composed of high- and low-density balsa layers separated by a circular adhesive interface or FRP arch. The balsa layers were cut from panels w ...

Elsevier2014

Analytical modeling of local stresses at Balsa/timber core joints of FRP sandwich structures

Julia De Castro San Roman Fest, Thomas Keller, Anastasios Vassilopoulos, Michael Osei-Antwi

In order to optimize sandwich structures, core materials of different density and thus different stiffness and strength are often combined. The material discontinuities at joints of dissimilar core materials may lead to abrupt changes of the shear angles a ...

Elsevier2014

Effect of thermal lag on glass transition temperature of polymers measured by DMA

Thomas Keller, Anastasios Vassilopoulos, Wei Sun

This paper investigates the influence of thermal lag on the glass transition temperature of polymers measured under different heating rates during dynamic mechanical analysis (DMA). The E-modulus-temperature curves of a two-component epoxy adhesive and a p ...

Elsevier2014

Modeling of axial and shear stresses in multilayer Sandwich beams with stiff core layers

Julia De Castro San Roman Fest, Thomas Keller, Anastasios Vassilopoulos, Michael Osei-Antwi

In order to optimize the load-bearing behavior of sandwich structures and adapt it to specific requirements, their core may be composed of layers of different materials with tailored properties. These layers may consist not only of soft foam or honeycomb m ...

Elsevier2014

MODELING THE PROGRESSIVE DAMAGE OF ADHESIVELY BONDED JOINTS

Thomas Keller, Anastasios Vassilopoulos, Roohollah Sarfaraz Khabbaz, Moslem Shahverdi

A quasi-static progressive damage model based on the fracture mechanics approach was developed for adhesively-bonded pultruded glass fiber-reinforced polymer (GFRP) joints. The model comprises the implementation in a numerical algorithm of a mixed-mode fra ...

2014

Diffuse light transmittance of glass fiber-reinforced polymer laminates for multifunctional load-bearing structures

Julia De Castro San Roman Fest, Thomas Keller, Andreas Schueler, André Gabriel Kostro, Anastasios Vassilopoulos, Carlos Pascual Agullo

The diffuse light transmittance of hand lay-up glass fiber-reinforced polymer (GFRP) laminates was investigated. Spectrophotometric experiments were performed on unidirectional and cross-ply glass fiber-reinforced polymer specimens with fiber volume fracti ...

SAGE Publications2014

Punching shear strengthening of flat slabs using prestressed carbon fiber-reinforced polymer straps

Thomas Keller, Robert Koppitz

An experimental study of full-scale reinforced concrete flat slabs crosswise strengthened with prestressed carbon fiber-reinforced polymer (CFRP) straps against punching shear was performed. The effects of two strap anchoring systems and of slab thickness ...

Elsevier2014

Structural limits of FRP-balsa sandwich decks in bridge construction

Julia De Castro San Roman Fest, Thomas Keller, Anastasios Vassilopoulos, Michael Osei-Antwi

Elsevier2014

Mixed-mode quasi-static failure criteria for adhesively-bonded pultruded GFRP joints

Thomas Keller, Anastasios Vassilopoulos, Moslem Shahverdi

The strain energy release rates of adhesively-bonded pultruded GFRP joints were determined experimentally. The crack propagated in the adherend along paths outside the symmetry plane accompanied by fiber bridging. A new method, designated the "extended glo ...

Elsevier2014

Mixed-Mode I/II fracture behavior of asymmetric adhesively-bonded pultruded composite joints

Thomas Keller, Anastasios Vassilopoulos, Moslem Shahverdi

The mixed-mode fracture behavior of adhesively-bonded pultruded glass fiber-reinforced polymer joints was experimentally investigated using asymmetric mixed-mode bending specimens. The crack propagated along paths outside the symmetry plane and, therefore, ...

Elsevier2014

Tension Chord Model Modification for Uniaxial Unloading and Reloading in Elastic and Plastic States

Thomas Keller, Robert Koppitz

The bond properties between concrete and steel reinforcement influence structural stiffness and deformation behavior as a result of tension stiffening. In specific cases, the load-bearing capacity of engineering structures depends on the deformation behavi ...

Asce-Amer Soc Civil Engineers2014

Mixed-mode fatigue failure criteria for adhesively-bonded pultruded GFRP joints

Thomas Keller, Anastasios Vassilopoulos, Moslem Shahverdi

The behavior of adhesively-bonded pultruded GFRP joints under cyclic loading was experimentally investigated. Three specimen types were examined: double cantilever beam, end load split, and mixed-mode bending specimens for Mode I, Mode II, and mixed-Mode I ...

Elsevier2013

Carbon Fiber-Reinforced Polymer Punching Reinforcement and Strengthening of Concrete Flat Slabs

Thomas Keller, Robert Koppitz

Three different carbon fiber-reinforced polymer (CFRP) systems were used to reinforce new or strengthen existing concrete slabs against punching. Untensioned CFRP plates or only very low prestressed CFRP straps could not prevent brittle punching failure. S ...

American Concrete Institute2013

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