Publication

Damage models for UHPFRC and R-UHPFRC tensile fatigue behaviour

Eugen Brühwiler, Tohru Makita
2015
Journal Articles

Abstract

Ultra-High Performance Fibre Reinforced Composites (UHPFRC) is a cementitious material showing relatively high tensile strength and significant tensile strain-hardening behaviour (given a certain volume of fibres). Adding a layer of UHPFRC or UHPFRC combined with steel rebars (R-UHPFRC) to structural members is an efficient method for strengthening of reinforced concrete structures. This paper presents empirical fatigue damage models for UHPFRC and R-UHPFRC. The tensile fatigue behaviour of UHPFRC is analysed based on elementary damage mechanics theory. Damage grows at a constant rate until fatigue fracture, which is considered to be due to the capacity of UHPFRC to redistribute local deformation increases. Difference in damage evolution between fatigue fracture tests and run-out fatigue tests is highlighted, and it is understood that when significant damage is caused in UHPFRC in the early stage of the fatigue life, UHPFRC fractures due to tensile fatigue. An average curve of damage evolution of fatigue fracture tests is proposed as a bi-linear damage evolution model of UHPFRC. The damage evolution model is used to determine the remaining fatigue life of UHPFRC by correlating the damage-fatigue strain relationship for UHPFRC. Considering that stress transfer from UHPFRC to steel rebars is characteristic of the R-UHPFRC tensile fatigue behaviour and is caused by fatigue damaging of the UHPFRC part, evolution of the modulus of deformation, i.e. the ratio of stress to strain of the UHPFRC part of the R-UHPFRC specimens is investigated. Among all the R-UHPFRC specimens similar behaviour is observed in the fatigue damaging curves of the deformation modulus of the UHPFRC part. An empirical relationship between the modulus of deformation of the UHPFRC part in the R-UHPFRC element and the number of fatigue cycles is proposed to characterise the R-UHPFRC tensile fatigue behaviour. (C) 2015 Elsevier Ltd. All rights reserved.

Official source

https://infoscience.epfl.ch/entities/publication/910acb66-9be5-42d5-a115-5872790e3d66

Eugen Brühwiler, Tohru Makita
2015
Journal Articles

Abstract

Official source

https://infoscience.epfl.ch/entities/publication/910acb66-9be5-42d5-a115-5872790e3d66

Ontological neighbourhood

Chemical engineering

Materials science: Deformation of materials

Related concepts (32)

Fatigue (material)

In materials science, fatigue is the initiation and propagation of cracks in a material due to cyclic loading. Once a fatigue crack has initiated, it grows a small amount with each loading cycle, typically producing striations on some parts of the fracture surface. The crack will continue to grow until it reaches a critical size, which occurs when the stress intensity factor of the crack exceeds the fracture toughness of the material, producing rapid propagation and typically complete fracture of the structure.

Reinforced concrete

Reinforced concrete, also called ferroconcrete, is a composite material in which concrete's relatively low tensile strength and ductility are compensated for by the inclusion of reinforcement having higher tensile strength or ductility. The reinforcement is usually, though not necessarily, steel bars (rebar) and is usually embedded passively in the concrete before the concrete sets. However, post-tensioning is also employed as a technique to reinforce the concrete. In terms of volume used annually, it is one of the most common engineering materials.

Ultimate tensile strength

Ultimate tensile strength (also called UTS, tensile strength, TS, ultimate strength or in notation) is the maximum stress that a material can withstand while being stretched or pulled before breaking. In brittle materials the ultimate tensile strength is close to the yield point, whereas in ductile materials the ultimate tensile strength can be higher. The ultimate tensile strength is usually found by performing a tensile test and recording the engineering stress versus strain.

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