CE 563 Airport Design

Transcription

1 CE 563 Airport Design Reference: AC 150/5320-6E Pavement design life used Correct surface distress Correct surface condition Damage from overloading Serve heavier aircraft Assess existing pavement condition Thickness Condition Strength Subgrade soil classification Foundational strength Subsurface drainage condition Repair severe distress 1

2 Asphalt over existing flexible pavement Concrete over existing flexible pavement Asphalt over existing rigid pavement Concrete over existing rigid pavement HMA Base Course Tension Compression Subgrade Determine thickness and moduli of existing pavement layers Aircraft mixture Use FAARFIELD Trial overlay thickness Program iterates until CDF of 1 is obtained Minimum overlay of 2 inches for asphalt overlay of existing flexible pavement 2

3 Taxiway Asphalt surface, 4 inches P- 209, 10 inches P- 154, 6 inches Subgrade CBR = 10 Negligible frost action Aircraft mixture as shown Find necessary asphalt overlay thickness Aircraft Gross Weight, tons DC ,000 2,263 B B 873, B ER 634, Annual Departures! 3

4 Taxiway Asphalt surface, 4 inches P- 209, 12 inches Subgrade CBR = 10 (k = 141 pci) Negligible frost action Aircraft mixture as shown Find necessary PCC overlay thickness! Determine condition of existing rigid pavement Structural condition index (SCI) Cumulative damage factor used (CDFU) Determine thickness and moduli of existing pavement layers Aircraft mixture Use FAARFIELD Trial overlay thickness 4

5 Derived from pavement condition index (PCI) Uses only the structural components of PCI PCI has 15 different distress types SCI uses 6 of the 15 FAA defines rigid structural failure at SCI = percent of slabs exhibit structural crack Distress Corner break Longitudinal/transverse/ diagonal cracking Shattered slab Shrinkage cracks Spalling- joint Spalling- corner Severity Level Low, Medium, High Low, Medium, High Low, Medium, High Low Low, Medium, High Low, Medium, High +,!"# =!""!$" % #& ' $! ( $) '( % * ( # # '=! (=! a = adjustment factor m s = total number of distress types related to pavement structural failure n j = total number of severity levels for the ith distress f(t i, S j, D ij ) = deduct value for distress type T i, at the severity level S j, existing at density D ij 5

6 When SCI = 100, no visible distresses contributing to reduction in SCI Use the CDFU Defines existing pavement life that has been used up to the time of overlay CDFU = 100, existing pavement life has been used!"#$% & $ '()*& " ++,-./+& $ 0'()*& "!"#$% ,-./+& $ 2'()*& " L U = number of years of operation of the existing pavement until overlay L D = design life of the existing pavement in years FAARFIELD will calculate CDFU Enter the structure based on original design assumptions Enter estimated traffic applied to the pavement Set design life to number of years existing pavement has been in operation Run life CDFU is displayed 6

7 Taxiway PCC, 15.3 inches P- 306 Econocrete, 6 inches P- 209, 6 inches Subgrade CBR = 10 (k = 141 pci) Negligible frost action Aircraft mixture as shown, 12 year in- service life Find CDFU Aircraft Gross Weight, tons DC ,000 1,200 B B 873, B ER 634, Annual Departures! 7

8 SCI less than 100 Existing pavement has structural distress FAARFIELD assumes initial overlay thickness and iterates until reaching 20- year design life SCI equals 100 No structural distress CDFU is needed FAARFIELD assumes initial overlay thickness and iterates until reaching 20- year design life Taxiway PCC, 14 inches P- 304 CTB, 6 inches P- 209, 6 inches Subgrade CBR = 10 (k = 141 pci) Negligible frost action Aircraft mixture as shown Find required asphalt thickness Aircraft Gross Weight, tons DC ,000 2,263 B B 873, B ER 634, Annual Departures 8

9 ! Taxiway PCC, 14 inches P- 304 CTB, 6 inches P- 209, 6 inches Subgrade CBR = 10 (k = 141 pci) Negligible frost action Aircraft mixture as shown CDFU = 50 percent Find required asphalt thickness! 9

10 Reflection crack HMA PCC Load- induced movement Climate- induced movement PCC overlay is intentionally not bonded to existing PCC surface Typical for badly cracked pavements Thin layer of asphalt mixture used as bond breaker Determine SCI of existing pavement Determine thickness and moduli of existing pavement layers Aircraft mix Use FAARFIELD Trial overlay thickness Taxiway Debonding layer, 1 inch PCC, 14 inches P- 304 CTB, 6 inches P- 209, 6 inches Subgrade CBR = 10 (k = 141 pci) Negligible frost action Aircraft mixture as shown SCI = 40 percent 10

11 ! PCC overlay is bonded to existing PCC surface Typical for pavements in good to excellent condition Grout used to bond pavements Bonded pavement act as monolithic slab Determine thickness and moduli of existing pavement layers Aircraft mix Use FAARFIELD Design as new rigid pavement Existing PCC flexural strength! " #!$! % h c = PCC overlay thickness h = Required slab thickness h e = Existing pavement thickness 11

12 Asphalt over rubblized PCC Similar to an asphalt over flexible pavement overlay design Concrete over rubblized PCC Similar to design of a new PCC pavement FAARFIELD can accept a rubblized PCC layer It becomes very important to determine the correct modulus value for the rubblized PCC Slab thickness, inches Modulus, ksi >