LICENTIATE THESIS - Luleå tekniska universitet

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Evaluation of Concrete Structures The material properties of the concrete in the tested sleepers were high. The mean value for 16 compression tests was 100.7 MPa and the mean value for 13 tensile tests was 3.9 MPa. The sleepers produced with inferior methods are now inspected annually in order to see at what rate the cracking is progressing. The big question is now how fast a green or yellow sleeper turns into a red one, i.e. how fast is the formation of ettringite? Probably weather conditions have an important role. If a sleeper will be exposed to cyclic frost erosion the process ought to accelerate considerably. An indication of that the weather conditions may play an important role has been discovered on one sleeper. The midsection of this sleeper had been covered with equipment for the signalling system a so-called “Balis” and this part seemed to be in better conditions (no visible cracks) in comparison with the ends where the crack system had developed quite a bit. - 16 -
Evaluation of Concrete Structures 4 Concrete fatigue capacity. A study of deformations at tensile forces – Paper C 4.1 Background. Aim and Scope In this paper results and analyses are presented from uniaxial cyclic tensile fatigue tests. The tests can be considered as pilot tests. The fatigue tests in this paper can be compared to a deformation criterion proposed by Daerga & Pöntinen (1993) based on an idea of Balázs (1991). The model has successfully been used to describe bond failure between rebars and the concrete. The growth in deformation during a fatigue test can according to the model be divided into three phases, see Figure 11. In the beginning of the first phase the deformation rate is high but stagnates after a while. The second phase is characterised by a constant deformation rate. These two phases can be described as stable. During the third phase, the failure phase, the deformation rate increases rapidly leading to failure within a short time. The strain criterion for fatigue failure is that the strain at peak load during a static test corresponds to the strain at the changeover between phases two and three during a fatigue failure, see Figure 11. Tensile strain (linear scale) phase 1 Fatigue load phase 2 Initiation of fatigue failure phase 3 Number of load cycles (linear scale) - 17 - ε(σu) Static load Stress (linear scale) Figure 11 Strain criterion for fatigue failure according to Balázs (1991). σu
Page 1: LICENTIATE THESIS Evaluation of Con
Page 5: Preface This licentiate thesis pres
Page 8 and 9: Evaluation of Concrete Structures I
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Page 14 and 15: A. Simplified check A1. In-situ ins
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Page 21 and 22: Lok-Strength & Capo-Strength F [kN]
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Page 41: 6 Outlook Evaluation of Concrete St
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Page 47: Paper A CONCRETE STRENGTH DEVELOPME
Page 50 and 51: determine the in-place strength of
Page 52 and 53: strength could be the fact for all
Page 54 and 55: German Petersen & Poulsen (1993), s
Page 56 and 57: Rebound test (Schmidt-hammer) The r
Page 58 and 59: expected (about 8 MPa). But for the
Page 60 and 61: Figure 8 shows the location where t
Page 62 and 63: Tensile strength [MPa] 6.0 5.0 4.0
Page 64 and 65: Table 4 Mean value and standard dev
Page 66 and 67: Lok-Strength & Capo-Strength F [kN]
Page 68 and 69: fcc fct concrete compression streng
Page 70 and 71: The values that have been used are:
Page 73 and 74: LOAD CARRYING CAPACITY OF CRACKED C
Page 75 and 76: Figure 1 Principal drawing of teste
Page 77 and 78: Class 3. OK / Green: No visible cra
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0.5 1.0 +15 kNm 0.5 0.5 1.0 0.5 -11
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Horizontal force [kN] 100 80 60 40
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TEST SET-UP AND RESULTS Bending cap
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The displacement was measured by fo
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Figure 18 Failure of sleeper no. 10
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Sleeper No. 17 looks more like the
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c2 75 á 100 where ψ ′ c = = = 0
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The obtained stress σ t = 4.45 MPa
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M f,rail moment bearing capacity at
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Paper C CONCRETE FATIGUE CAPACITY.
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FATIGUE OF CONCRETE A common way to
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notch is deep enough that is). When
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Figure 5 Test set-up uniaxial tensi
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Table 1 A summary of all uniaxial t
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Strain [‰] 0.8 0.6 0.4 0.2 0 Phas
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11) the start of phase 3 takes plac
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ACKNOWLEDGEMENTS The study has been
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APPENDIX A Evaluated data from the
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C = dε / dN [× 10 −6 ] 100 10 1
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Test series A: S min = σ min / f c
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Paper D SHEAR FATIGUE CAPACITY - A
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1 Introduction The codes that have
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Dead Loads: Slab: 0.320 m á 24 kN/
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the equations to calculate the desi
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where ηγm is 1.5 for concrete (co
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different besides the strength clas
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Table 4.2 Fatigue strength. Number
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The shear force capacity, V Rd1, fo
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σ cd,min,equ lower stresses of the
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6.2 Strength values at fatigue load
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6.3 Strength values at fatigue load
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1 − 0.7166 14 ⋅ = 4.71 < 6 ⇒T
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The “new” equation for the desi
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Appendix A. Concrete Codes Excerpt
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DOCTORAL AND LICENTIATE THESES Divi
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