CT4860 STRUCTURAL DESIGN OF PAVEMENTS

More documents

Recommendations

Info

Figure 8. Nomograph for the determination of the k-value on top of a (sub-)base layer (1). Figure 8 is the graphical representation of equation 12: k= 2.7145.10 -4 (C1 + C2.e C3 + C4.e C5 ) (12) with: C1 = 30 + 3360.ko C2 = 0.3778 (hf – 43.2) C3 = 0.5654 ln(ko) + 0.4139 ln(Ef) C4 = -283 C5 = 0.5654 ln(ko) ko = modulus of subgrade/substructure reaction at top of underlying layer (N/mm 3 ) hf = thickness of layer under consideration (mm) Ef = dynamic modulus of elasticity of layer under consideration (N/mm 2 ) k = modulus of substructure reaction at top of layer under consideration (N/mm 3 ) The boundary conditions for equation 12 are: - hf ≥ 150 mm (bound material) and hf ≥ 200 mm (unbound material) - every layer under consideration has an Ef-value that is greater than the Efvalue of the underlying layer - log k ≤ 0.73688 log(Ef) – 2.82055 - k ≤ 0.16 N/mm 3 22
Example Sand subgrade: ko = 0.045 N/mm 3 (i.e. Eo = 100 N/mm 2 ). Sand sub-base, hf = 500 mm, Ef = 100 N/mm²: at top of sub-base also k = 0.045 N/mm 3 (as Ef = Eo). Lean concrete base, hf = 150 mm, Ef = 7500 N/mm² (cracked): at top of base k = 0.112 N/mm 3 . In the structural design of concrete pavements for motorways the Dutch State Highway Authorities use a k-value of 0.105 N/mm 3 (9). This k-value is obtained for a 150 mm thick lean concrete base, with Ef = 6000 N/mm 2 , on a sand sub-base and sand subgrade. 3.3 Stresses due to temperature variations 3.3.1 General Temperature variations lead to stresses in the concrete top layer. These stresses can be distinguished into (figure 9): 1. stresses due to a temperature change ∆T which is constant over the thickness of the concrete layer 2. stresses due to a temperature gradient ∆t which is constant over the thickness of the concrete layer 3. stresses due to an irregular temperature over the thickness of the concrete layer. Figure 9. Temperature in the concrete top layer in case of heating at the surface. A regular temperature increase or decrease ∆T leads to compressive and tensile stresses respectively in the concrete top layer due to friction over the underlying layer. However, for plain concrete pavements (that generally consist of slabs with both a length and a width smaller than 5 m (roads) or 7.5 m (airports), and for reinforced concrete pavements (with a ‘slab’ length equal to the crack distance of 1.5 to 3 m and a ‘slab’ width of maximum 5 m) these stresses are such small that they can be neglected. 23
Page 1: CT4860 STRUCTURAL DESIGN OF PAVEMEN
Page 5 and 6: Table of Contents 1. INTRODUCTION 3
Page 7 and 8: 1. INTRODUCTION In many countries c
Page 9 and 10: main part of the traffic loading. T
Page 11 and 12: Well graded crusher run, (high qual
Page 13 and 14: Property Sandcement Lean concrete A
Page 15 and 16: In the Dutch design method for conc
Page 17 and 18: 2.6 Layout of concrete pavement str
Page 19 and 20: widened (e.g. to 8 mm) to a certain
Page 21 and 22: The pavement was constructed in two
Page 23 and 24: p = ground pressure (N/mm 2 ) on to
Page 25: Lightweight fill material Density (
Page 29 and 30: Figure 10. Mean distribution (%) of
Page 31 and 32: 2. Directly besides the central par
Page 33 and 34: where: h = thickness (mm) of the co
Page 35 and 36: Positive temperature gradient ∆t
Page 37 and 38: There exist a lot of (modified) Wes
Page 39 and 40: P = 50 kN = 50000 N p = 0.7 N/mm²
Page 41 and 42: Figure 15. Influence chart of Picke
Page 43 and 44: Figure 17. Influence chart of Picke
Page 45 and 46: 2 Ed I d S d = (36) 2 3 1 + ( 1 +
Page 47 and 48: slab wu = deflection (mm) at the jo
Page 49 and 50: Example L = 4.5 m = 4500 mm k = 0.1
Page 51 and 52: Figure 22. Factor F as a function o
Page 53 and 54: Example In this section an example
Page 55 and 56: Table 10 clearly shows that in the
Page 57 and 58: For instance, on the basis of numer
Page 59 and 60: Although the increase of the flexur
Page 61 and 62: 4. DESIGN METHODS FOR CONCRETE PAVE
Page 63 and 64: Figure 28. AASHTO design chart for
Page 65 and 66: 4.2.3 The BDS-method The British de
Page 67 and 68: Figure 32. Additional plain concret
Page 69 and 70: of the concrete layer. Figure 34 sh
Page 71 and 72: where: nij = predicted number of re
Page 73 and 74: 5. DUTCH DESIGN METHOD FOR CONCRETE
Page 75 and 76: Only the technical aspects of the o
Page 77 and 78:
2 ' ⎛ ⎞ L σ = 0.85 σ”t = 0.
Page 79 and 80:
5.3 Revised design method In the ea
Page 81 and 82:
Therefore in the revised method the
Page 83 and 84:
The tensile flexural stress at the
Page 85 and 86:
w l = 4.8 e -0.35.log Neq (74) The
Page 87 and 88:
Axle load group (kN) Number of carr
Page 89 and 90:
5.4.3 Climate In the years 2000 and
Page 91 and 92:
- W according to equation 81a at pr
Page 93 and 94:
5.4.8 Thickness plain/reinforced co
Page 95 and 96:
W = load transfer at longitudinal e
Page 97 and 98:
‘reference temperature’ at the
Page 99 and 100:
The central tensile force N in the
Page 101 and 102:
σs,cr = tensile stress in reinforc
Page 103 and 104:
In the Dutch design method for conc
Page 105 and 106:
10% 5% reference 5% 10% smaller sma
Page 107 and 108:
13. Houben, L.J.M. Finite element a
Page 109 and 110:
31. Guide for the Standardisation o
show all

CT4860 STRUCTURAL DESIGN OF PAVEMENTS

Create successful ePaper yourself

Delete template?

Save as template?