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Evaluation of Concrete Structures Figure 5 Principal drawing of tested concrete sleepers. In this paper results from strength capacity tests are presented along with possible failure mechanisms of the fastener when loaded horizontally. The purpose with the tests have been to get information on how the cracking influences the load carrying capacity compared to an un-cracked sleeper. 3.2 Visual inspection and Classification The first inspections led to a categorization of the sleepers depending on the cracking. They were divided into three classes by the Swedish National Rail Administration. The typical damages for each class are: Class 1. Acute / Red: The cracking is so severe that there is a considerable reduction of the load carrying capacity. There are typical longitudinal cracks in the middle part of the sleeper. There are also cracks at the end of the sleepers with a crackled pattern. The sleepers may have a crack from the fastener and downwards. The concrete surface is discoloured by yellow spots. A typical crack-pattern is shown in Figure 6. Class 2. Initial degradation / Yellow: Some cracks. The cracking is of the kind that the load carrying capacity is almost intact. There may be cracks with a crackled pattern at the end of the sleepers. The sleepers might have a crack from the fastener and downwards. There is presence of yellow spots. Typical crack-patterns are given in Figure 7. Class 3. OK / Green: No visible cracks. No visible tendencies to develop major faults. No change in colour. The load carrying capacity is intact. Figure 6 Characteristic crack patterns for sleepers of class 1 (red sleepers). - 12 -
Evaluation of Concrete Structures a) b) c) Figure 7 Typical cracks for sleepers of class 2 (yellow). a) Sleepers in group 3 i.e. no visible cracks on the upper side but there might be cracks on the side at the lower edge. b) Sleepers in group 2 i.e. only 1 or 2 visible cracks on the upper side. They have fewer cracks on the side towards the lower edge than the sleepers in group 1 (the crackled pattern is not yet as “developed” as for group 1 sleepers). c) Sleepers in group 1 i.e. cracks in a crackled pattern on the side as well as on the upper side. Since the yellow sleepers are so many (about 300 000 up to this date) and the variation in cracking is so large, they have been divided into subcategories in the hope of finding out if there is a variation in load carrying capacity among them. The criterion that has been used as a basis is what kind of cracks an inspector has a chance of discovering when he/she walks along the railway track. Since the sleepers are covered with macadam, it is only possible to notice damages that are on the upper side of the sleeper and 1 to 2 cm along the top parts of the sides. The cracks that have been used as target have a width larger than 0.05mm. These are possible to see with the naked eye and can be discovered without the need to get down on one’s knees. These cracks are in this paper called visible cracks. The area on the sleeper where the first visible cracks appear (when they lie in the track) seems to be on the upper side at the end, near the edge. This leads to a problem since most yellow sleepers also have cracks on the side towards the lower edge, see Figure 7. These cracks are not possible to detect at an inspection as long as the macadam is not removed. This might lead to the fact that a yellow sleeper is given the class green. The subdividing of the yellow sleepers is thus only based on visible cracks on the upper side of the sleeper, at the end. Worth pointing out is that not all sleepers have two ends with the same type of damages. Some sleepers have several cracks at one end but no cracks at the other. The yellow sleepers have therefore in turn been subdivided into three categories: Group 1 Several cracks on the upper side with a crackled pattern Figure 7 c). Group 2 One or two cracks on the upper side, see Figure 7 b). Group 3 No cracks on the upper side, see Figure 7 a). 3.3 Results The tests that have been performed are: (1) Bending capacity of the midsection. - 13 -
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
Page 19 and 20: Evaluation of Concrete Structures G
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
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Figure 1 Principal drawing of teste
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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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