Thomas Keller
École Polytechnique Fédérale de Lausanne
Composite numberUltimate tensile strengthGlass transitionEngineeringFinite element methodComposite materialEpoxyGlass fiberMaterials scienceGirderJoint (geology)DeckStiffnessFracture (geology)PolymerPultrusionFracture mechanicsStructural engineeringAdhesiveFibre-reinforced plasticForensic engineeringStress (mechanics)
332Publications
45H-index
4,885Citations
Publications 330
Newest
#1Anastasios Vasilopoulos (EPFL: École Polytechnique Fédérale de Lausanne)H-Index: 2
#2Moslem Shahverdi (EPFL: École Polytechnique Fédérale de Lausanne)H-Index: 15
Last. Thomas Keller (EPFL: École Polytechnique Fédérale de Lausanne)H-Index: 45
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The fatigue/fracture behavior of adhesively-bonded pultruded glass fiber-reinforced polymer (GFRP) joints is significantly affected by the loading ratio. This effect is analyzed in this chapter through a complete fatigue/fracture database, derived during recent years, and correlated with the exhibited failure processes of the examined joints. A phenomenologically based criterion is then used for the simulation of the exhibited behavior and the prediction of the fatigue/fracture behavior of the e...
2 CitationsSource
#1Myrsini AngelidiH-Index: 3
Last. Thomas KellerH-Index: 45
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#1Sonia Yanes-ArmasH-Index: 4
Last. Thomas KellerH-Index: 45
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The energy dissipation capacity resulting from progressive cracking of the web-flange junctions (WFJs) of a pultruded GFRP deck system was experimentally investigated. Web-cantilever bending experiments up to failure were performed on two WFJ types (IfO, IcO) with similar geometry and fiber architecture but different initial imperfections. The latter resulted in different load-displacement behaviors (linear and markedly nonlinear up to failure in IfO and IcO, respectively) and failure modes. Fai...
#2Steffen FrankeH-Index: 7
Last. Thomas Keller (EPFL: École Polytechnique Fédérale de Lausanne)H-Index: 45
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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 taken from the same species, and grown in the same geographical location and local growth conditions. Consequently, there is a high variability in the mechanical properties [1-2]. This variability is both spatial and random, and is sometimes referred to as ‘random spatial variability’ [3]. Four groups of specimens of dif...
1 Citations
#1Moslem Shahverdi (EPFL: École Polytechnique Fédérale de Lausanne)H-Index: 15
#2Anastasios P. Vassilopoulos (EPFL: École Polytechnique Fédérale de Lausanne)H-Index: 28
Last. Thomas Keller (EPFL: École Polytechnique Fédérale de Lausanne)H-Index: 45
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The fracture behavior of adhesively-bonded pultruded double cantilever beam specimens is studied in this chapter. The crack propagates along paths away from the symmetry plane and is accompanied by fiber bridging. Finite element models are developed to quantify the effects of asymmetry and fiber bridging on the fracture energy. The virtual crack closure technique can be used for calculation of the fracture components at the crack tip and an exponential traction–separation cohesive law can be app...
Source
#1Robert Koppitz (EPFL: École Polytechnique Fédérale de Lausanne)H-Index: 5
#2Albin KenelH-Index: 8
Last. Thomas Keller (EPFL: École Polytechnique Fédérale de Lausanne)H-Index: 45
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Punching shear resistance usually constitutes the decisive design criterion for reinforced concrete flat slabs supported by columns. Modeling approaches based on Kinnunen and Nylander's rotation-symmetric sector model, such as the Quadrilinear Sector Model (QSM), allow the prediction of the slab's load rotation behavior. To take into account an orthogonal reinforcement layout, the steel Young's Modulus is usually reduced. A mechanically better justified flexural stiffness reduction factor is der...
7 CitationsSource
#1Carlos Pascual (EPFL: École Polytechnique Fédérale de Lausanne)H-Index: 2
#2Julia de Castro (EPFL: École Polytechnique Fédérale de Lausanne)H-Index: 15
Last. Thomas Keller (EPFL: École Polytechnique Fédérale de Lausanne)H-Index: 45
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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 into glass fiber-reinforced polymer building skins of sandwich structures. Spectrophotometric experiments on unidirectional and cross-ply glass fiber-reinforced polymer specimens in the range from 0.20 to 0.45 fiber volume fraction and artifici...
7 CitationsSource
#1Michael Osei-Antwi (EPFL: École Polytechnique Fédérale de Lausanne)H-Index: 6
#2Julia de Castro (EPFL: École Polytechnique Fédérale de Lausanne)H-Index: 15
Last. Thomas Keller (EPFL: École Polytechnique Fédérale de Lausanne)H-Index: 45
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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 which consisted of balsa blocks adhesively bonded together. Failure in the beams was initiated by cracks propagating through the balsa core thickness. The crack locations could be predicted using the Tsai-Wu failure criterion. Cracks initiated i...
14 CitationsSource
#1Robert Koppitz (EPFL: École Polytechnique Fédérale de Lausanne)H-Index: 5
#2Albin KenelH-Index: 8
Last. Thomas Keller (EPFL: École Polytechnique Fédérale de Lausanne)H-Index: 45
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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 on punching behavior were compared. In one system the anchors were adhesively bonded to the concrete surface, while an external steel frame balanced the horizontal strap force components in the second system. Strap activation and thus strap for...
16 CitationsSource
#1Robert Koppitz (EPFL: École Polytechnique Fédérale de Lausanne)H-Index: 5
#2Albin KenelH-Index: 8
Last. Thomas Keller (EPFL: École Polytechnique Fédérale de Lausanne)H-Index: 45
view all 3 authors...
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 behavior and may be affected by load history because of unloading and reloading (UR) cycles. The bond stress-slip relationship of the original tension chord model was modified to make it applicable for general UR cycles in the elastic and plastic sta...
2 CitationsSource