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Thomas Keller

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Publications associées (309)

Neutron Larmor diffraction investigation of the rare-earth pyrochlores R2Ti2O7 (R = Tb, Dy, Ho)

Thomas Keller, Felix Groitl

In this work, we present a neutron Larmor diffraction study of the rare-earth pyrochlores R2Ti2O7 with R = Tb, Dy, Ho. We measured the temperature dependence of the lattice parameter with precision 10(-5), between 0.5 and 300 K in each of the three compoun ...

Amer Physical Soc2016

Anomalous thermal decoherence in a quantum magnet measured with neutron spin echo spectroscopy

Thomas Keller, Felix Groitl

The effect of temperature dependent asymmetric line broadening is investigated in Cu(NO3)(2)center dot 2.5D(2)O, a model material for a one-dimensional bond alternating Heisenberg chain, using the high resolution neutron-resonance spin echo (NRSE) techniqu ...

Amer Physical Soc2016

Time-dependent correlations in quantum magnets at finite temperature

Thomas Keller, Felix Groitl

In this Rapid Communication we investigate the time dependence of the gap mode of copper nitrate at various temperatures. We combine state-of-the-art theoretical calculations with high precision neutron resonance spin-echo measurements to understand the an ...

Amer Physical Soc2016

Structural concept and design of a GFRP-polyurethane sandwich roof structure

Thomas Keller, Sonia Yanes Armas

This work presents the concept and structural design of a 1000-m2 glass fiber-reinforced polymer (GFRP) sandwich roof replacing a timber roof over an indoor swimming pool. The advantages offered by the lightweight, multifunctional GFRP-polyurethane (PUR) s ...

2016

FRP sandwich structures in bridge and building construction

Thomas Keller

Selected applications of fiber-reinforced polymer (FRP) sandwich structural elements in building and bridge construction are discussed. It is shown how in building construction this technology enables the integration of functions such as load-bearing capac ...

2016

Pull-out behavior of CFRP ground anchors with two-strap ends

Thomas Keller, Anastasios Vassilopoulos, Haifeng Fan

Pull-out experiments were performed on three carbon fiber-reinforced polymer (CFRP) ground anchors simulating their applications in different rock types which provided different confinement levels. The CFRP tendons comprised, on the ground side, a prefabri ...

The Hong Kong Polytechnic University2016

Aramid/glass fiber-reinforced thermal break - thermal and structural performance

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

Energetically weak points in thermally insulated building envelopes are formed by thermal breaks that are implemented to structurally connect external balconies to internal slabs. Current thermal breaks comprise stainless steel bars that penetrate the insu ...

Elsevier2016

Twin-shaped CFRP-sandwich pedestrian bridge

Thomas Keller

A concept of a nature-inspired pedestrian bridge which tries to merge architectural, structural and manufacturing aspects in an optimized way is presented. The 18.0-m-span bridge is designed as an overhead spatial frame of a complex double-curved shape, wh ...

2016

The statistical variability and length effects in the tensile transverse behavior of clear timber

Thomas Keller, Anastasios Vassilopoulos, Alireza Farajzadeh Moshtaghin, Steffen Franke

In this work, clear timber specimens of different lengths with a small cross-sectional area were cut in the transverse direction of timber boards and tested under tensile loading. Regularly positioned and randomly positioned specimens were cut from differe ...

2016

System transverse in-plane shear stiffness of pultruded GFRP bridge decks

Julia De Castro San Roman Fest, Thomas Keller, Sonia Yanes Armas

The static transverse behavior of two pultruded GFRP deck systems with trapezoidal (DS) and triangular (AS) cell cross-sectional geometry was experimentally investigated in order to study their transverse in-plane shear stiffness. Symmetric three-point ben ...

Elsevier2016

Aramid/glass fiber-reinforced thermal break - Structural system performance

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

Energetically critical points in thermally insulating building envelopes are caused by penetrations of building interior concrete slabs through the envelope insulation layers to create external balconies. A new highly insulating balcony thermal break eleme ...

Elsevier2016

Effect of Natural Weathering on Durability of Pultruded Glass Fiber-Reinforced Bridge and Building Structures

Julia De Castro San Roman Fest, Thomas Keller, Anastasios Vassilopoulos, Nikolaos Alexandros Theodorou

After 17 and 15years of use, respectively, a detailed inspection of a pedestrian bridge and a 5-story building structure composed of partly adhesively bonded pultruded glass fiber-reinforced polymer (GFRP) profiles was conducted accompanied by full-scale s ...

American Society of Civil Engineers2016

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

Thomas Keller, Anastasios Vassilopoulos, Moslem Shahverdi

The partitioning of the total strain energy release rate, G(tot), into the Mode I, G(I), and Mode II, G(II), components is challenging, especially in asymmetric cracks. Although many researchers have studied the fracture behavior of composite materials und ...

Elsevier Science Bv2016

Effect of service temperature on the shear creep response of rigid polyurethane foam used in composite sandwich floor panels

Thomas Keller, Mário Alexandre De Jesus Garrido

This paper presents an experimental and analytical study about the effect of temperature on the shear creep response of a rigid polyurethane (PUR) foam within the scope of sandwich panel application in building floors. Shear creep tests were carried out on ...

Elsevier2016

Effect of service temperature on the flexural creep of vacuum infused GFRP laminates used in sandwich floor panels

Thomas Keller, Mário Alexandre De Jesus Garrido

This paper presents an experimental and analytical study about the effect of temperature on the flexural creep of GFRP laminates produced by vacuum infusion. Such laminates are considered for use in the faces of sandwich panels for building floor applicati ...

Elsevier2016

Pull-out behavior of CFRP single-strap ground anchors

Thomas Keller, Anastasios Vassilopoulos, Haifeng Fan

Pull-out experiments were performed on four carbon fiber-reinforced polymer (CFRP) ground anchors simulating their applications in rock and soil. The CFRP tendons used in these anchors comprise a single-strap end on both the ground and air sides. On the gr ...

2016

Random field-based modeling of size effect on the longitudinal tensile strength of clear timber

Thomas Keller, Anastasios Vassilopoulos, Alireza Farajzadeh Moshtaghin, Steffen Franke

In the current study, a random field-based size effect model has been proposed for the longitudinal tensile strength of clear timber. Since the failure mode is brittle, the problem is basically an extreme value problem of finding the distribution of minima ...

Elsevier2016

Creep-fatigue interaction in composite materials

Thomas Keller, Anastasios Vassilopoulos, Abdolvahid Movahedirad

A novel phenomenological model taking into account the creep-fatigue interaction in composite materials’ fatigue performance is introduced in this paper. The model is based on the derivation of a master curve by using existing experimental fatigue data fro ...

2016

Post-wrinkling behavior of webs in GFRP cell-core sandwich structures

Thomas Keller, Behzad Dehghan Manshadi, Anastasios Vassilopoulos

Similarly to the post-buckling behavior of steel girder webs, the post-wrinkling behavior of glass fiber reinforced polymer (GFRP) cell-core sandwich webs can increase their ultimate shear strength. Post wrinkling is, however, different from post-buckling ...

Elsevier2016

Quantification of spatial variability for transverse elastic modulus of spruce wood

Thomas Keller, Anastasios Vassilopoulos, Alireza Farajzadeh Moshtaghin, Steffen Franke

Different factors such as age, location of timber within the tree, structural imperfections, load history such as wind and snow etc. can affect the material properties of timber. Consequently, there is a high variability in the mechanical properties which ...

2016

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