1 Método de diseño de espesores para construcciones nuevas TALLER DE DISEÑO DE PAVIMENTOS DE CONCRETO November 7, 2014 Robert Rodden, P.E. Senior Director of Pavement Technology Design Methods Countries with Concrete Pavements Argentina Australia Austria Belgium Bolivia Brazil Canada Chile China Costa Rica Czech Republic Dominican Republic Ecuador El Salvador France Germany Ghana Guatemala Honduras India Indonesia Iran Italy Japan Kenya Kingdom of Bahrain Mexico Netherlands New Zealand Nicaragua Norway Pakistan Peru Poland Portugal Puerto Rico Russia South Africa South Korea Spain Sweden Switzerland Taiwan Thailand Turkey Uruguay United Kingdom USA … ACPA’s apps.acpa.org has been accessed in over 140 countries! Certainly we have many design methods!!! SOME of the Design Variety AASHTOWare Pavement ME USA, Canada AASHTO 93/WinPAS USA, Canada, most of South & Central America, etc. TCPavements OptiPave Chile, Guatemala, Peru cncPave South Africa VENCON2.0 Belgium, Netherlands Custom Catalog Germany, India, Poland ACPA StreetPave (previously the PCA Method) Australia, Portugal, USA (“approved” in MN and VA), Canada, Uruguay IP-07/2004 Brazil CHAUSSEE2 Canada FAARFIELD, AirPave, ACI 330, BCOA, CO 6x6x6, custom method, etc. USA US Practices are Changing Summary of State Agency practice in 2005: At the end of 2013, 41 state agencies had performed ME Design calibration and implementation efforts, indicating a relatively quick shift from AASHTO 93. Design Method Used Percent of Responding Agencies State Agency AASHTO 72/86/93 85% AR, AZ, DE, FL, ID, IN, IA, KS, MD, MI, NV, NC, OH, OK, SC, SD, TN, UT, VA, WA, WV, WI, WY AASHTO MEPDG 4% MO PCA Method 7% HI, IN, IA State-Developed 11% IL, MT U.S. Roadway Length (lane miles) State Agency, 19% County, 44% Town, 32% Other, 1% Federal, 3% Source: HM-10, 2012 FHWA Highway Statistics AASHTO tools are being developed for these owners… City, county, and other local engineers need to decide what to use locally because Pavement ME will not trickle down due to its cost and complexity!
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Método de diseño de espesores para construcciones nuevas
GuatemalaHondurasIndiaIndonesiaIranItalyJapanKenyaKingdom of BahrainMexicoNetherlandsNew ZealandNicaraguaNorwayPakistanPeruPoland
PortugalPuerto RicoRussiaSouth AfricaSouth KoreaSpainSwedenSwitzerlandTaiwanThailandTurkeyUruguayUnited KingdomUSA… ACPA’s apps.acpa.org has been accessed in over 140 countries!
Certainly we have many design methods!!!
SOME of the Design Variety
AASHTOWare Pavement ME USA, Canada
AASHTO 93/WinPASUSA, Canada, most of South & Central America, etc.
TCPavements OptiPave Chile, Guatemala, PerucncPave South Africa VENCON2.0 Belgium, NetherlandsCustom Catalog Germany, India, Poland
ACPA StreetPave (previously the PCA Method)
Australia, Portugal, USA (“approved” in MN and VA), Canada, Uruguay
IP-07/2004 BrazilCHAUSSEE2 CanadaFAARFIELD, AirPave, ACI 330, BCOA, CO 6x6x6, custom method, etc.
USA
US Practices are Changing
Summary of State Agency practice in 2005:
At the end of 2013, 41 state agencies had performed ME Design calibration and implementation efforts, indicating a relatively quick shift from AASHTO 93.
Design Method Used
Percent of Responding Agencies
State Agency
AASHTO 72/86/93
85%AR, AZ, DE, FL, ID, IN, IA, KS, MD, MI, NV, NC, OH, OK, SC, SD, TN, UT, VA, WA, WV, WI, WY
AASHTO MEPDG 4% MOPCA Method 7% HI, IN, IA
State-Developed 11% IL, MT
U.S. Roadway Length (lane miles)
State Agency,
19%
County, 44%
Town, 32%
Other, 1% Federal, 3%
Source: HM-10, 2012 FHWA Highway Statistics
AASHTO tools are being developed for these owners…
City, county, and other local engineers need
to decide what to use locally because
Pavement ME will not trickle down due to its
cost and complexity!
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Design Method Basis
Mechanistic – Purely scientific and based on measured, defendable scientific rules and laws
Empirical – Based on observations or experimentation and requires a lot of tests to connect all the relationships
/ ∆L α ∗ ∆ ∗
U.S. Design Standards for Roadways
AASHTOWarePavement ME (previously known as DARWin-ME and MEPDG)
AASHTO 93 (software as ACPA WinPAS)
ACPA StreetPave
325 & 330
AASHTO 93/WinPASacpa.org/winpas
AASHO Road Test (1958-1960)
Included 368 concrete and 468 asphalt sections | focus was highway pavement
Included a wide range of axle loads and pavement cross-sections
Design first introduced in 62, revised several times thereafter until 93 version
EMPIRICAL
Typical AASHO Loop LayoutTangent = 6,800ft (2km)
368 rigid sections
468 flexible sections
Subgrade = Clay Soil
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AASHO Test Traffic
Max Single Axle
Max Tandem Axle
Performance Metric
Some AASHO Results – Loop 2
…1,114,000 load applications to end
Some AASHO Results – Loop 2
Some AASHO Results – Loop 4 Some AASHO Results – Loop 4
4
Some AASHO Results – Loop 6 Some AASHO Results – Loop 6
Performance Estimated Subjectively
Present Serviceability Index (PSI)4.0 – 5.0 = Very Good
3.0 – 4.0 = Good2.0 – 3.0 = Fair
1.0 – 2.0 = Poor0.0 – 1.0 = Very Poor
“Failure” at the Road Test considered @ 1.5
Typical U.S. state agency terminal serviceability in practice = 2.5
Note on Inference Space of ‘93
Data Limits(AASHO Road Test)
CurrentDesigns>100 million
<2 million
AXLE LOAD REPETITIONS
PAVEM
ENT
THIC
KN
ESS
Current design traffic is far beyond AASHO road test limits
Don’t Just Take My Word…“The current design guide and its predecessors were largely based on design equations empirically derived from the observations AASHTO’s predecessor made during road performance tests completed in 1959-60. Several transportation experts have criticized the empirical data thus derived as outdated and inadequate for today’s highway system. In addition, a March 1994 DOT Office of Inspector General report concluded that the design guide was outdated and that pavement design information it relied on could not be supported and validated with systematic comparisons to actual experience or research.”
…this is why Pavement ME exists!
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Standard Normal Deviate
OverallStandard Deviation Thickness
Change in Serviceability
Terminal Serviceability
DrainageCoefficient
Load Transfer
Modulus ofRupture
Modulus of Elasticity
Modulus ofSubgrade Reaction
1986-93 Concrete Pavement Equation
10 Inputs.Solve for 11th
Traffic
Rigid Design Nomograph
WinPAS Makes it Easy
MEPDG / DARWin-ME /AASHTOWare Pavement ME
AASHTOWare Pavement ME Design
15+ years in the making
Design method and software not “perfect”; not intended to be a “final” product
Complex and relatively costly
Requires local calibration to work correctly
Models were not developed for street, road, parking lot, etc.
Just as rigid and flexible ESALs are different because of their different response…
Single, tandem and tridem axle groups (and at differing loads) cause differing relative damages
Single-axles usually cause more fatigue damage
Tandem and tridem axles usually cause more erosion damage
… so even within just rigid pavement design, ESAL count for same traffic spectrum and # of trucks in the design lane is really different for each distress type modeled!?!
OUTPUTS, OUTPUTS, OUTPUTS!!!
Simpler ME Option: MnDOT Drainage in ME Design
“The current state of the art is such that conclusive remarks regarding the effectiveness of pavement subsurface drainage or the need for subsurface drainage are not possible.”
… so we must rely on field studies:• Subbase stiffness matters more than
drainage for JPCP performance• Although excess moisture and poor
drainage was shown to be detrimental to pavement performance in the past, current designs are less susceptible to moisture damage (thicker sections, improved materials, widespread use of dowels, etc.)
Impact of Hurricane Katrina on Roadways in New Orleans
Louisiana DOT study looked at impact of flooding and overloads from relief effort on pavements
Used FWD, GPR, DCP, coring, etc. to assess structure“…asphalt pavements had strength loss equivalent to about two inches of new asphalt concrete…Very little relative damage was detected for the PCC pavements.”
Top 10 ME Design Most Sensitive
1. Concrete Flexural Strength at 28-Days
2. Concrete Thickness
3. Surface Shortwave Absorptivity (SSA)
4. Joint Spacing
5. Concrete Modulus of Elasticity at 28-Days
6. Design Lane Width with a 14 ft (4.3 m) Widened Slab
7. Edge Support via Widened Slab
8. Concrete Thermal Conductivity
9. Concrete Coefficient of Thermal Expansion (CTE)
10. Concrete Unit Weight
Red = only ME Design input… the VALUE of the software!Blue + Bold = common for all
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Implementation in the US @ Jan 2014
Implementation work underway
Nearing Implementation
No Plans / No information
Using Pavement-ME
AlaskaHawaii
8 states have either fully or partially implemented
StreetPave/PCA Methodacpa.org/streetpave
StreetPave’s Origins
PCA thickness design methodology for JPCPfirst published in 1966
used slab stress/fatigue asthe sole design criterionfor determining thickness
updated in 1984failure by erosion (pumping)
edge support
MECHANISTIC -EMPIRICAL From PCA Method to StreetPave
StreetPavereleased in 2005 by ACPA
tailored for streets and roads
improvements included:enhanced concrete fatigue model w/reliability component
ability to analyze tridem axles in the traffic spectrum
new recommendations for dowel bars, joint spacing, subgrade/subbase moduli, etc.
side-by-side design comparison to asphalt sections
StreetPave12
StreetPave12released in 2012 by ACPA
tailored for streets and roads
improvements included:compatibility with 64-bit processors
force undoweled design
overlay designs
improvement of subgrade/subbase characterization
inclusion of fibers in all concrete designs
improved traffic characterization; save custom traffic spectrum
ACI 330 traffic spectrums
clarified help screens
Failure Modes Considered
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Total trucks in design lane over the design life… calculated from trucks/day (2-way), traffic growth rate (%/yr), design life (yrs), directional distribution (%) and design lane distribution (%)
Traffic Spectrum + CountsSingle Axles
Axle Load (kip) Axles/1,000 Trucks
34 0.19
32 0.54
30 0.63
28 1.78
26 3.52
24 4.16
22 9.69
20 41.82
18 68.27
16 57.07
Tandem Axles
Axle Load (kip) Axles/1,000 Trucks
60 0.57
56 1.07
52 1.79
48 3.03
44 3.52
40 20.31
36 78.19
32 109.54
28 95.79
24 71.16
Equivalent stress at the slab edge:
Me = equivalent moment, psi; different for single, tandem, and tridem axles, with and without edge support - func on radius of relative stiffness, which depends on concrete modulus, Poisson’s ratio, and thickness and the k-value
hc = pavement thickness, in.
f1 = adjustment for the effect of axle loads and contact area
f2 = adjustment for a slab with no concrete shoulderf3 = adjustment to account for the effect of truck (wheel) placement at the slab edge
f4 = adjustment to account for approximately 23.5% increase in concrete strengthwith age after the 28th day and reduction of one coefficient of variation (COV) to account for materials variability
StreetPavemakes slab thicker to limit stress ratio low enough to achieve the design traffic repetitions
A Conservative Approach!
StreetPave fatigue calculation should be conservative relative to ME Design because:
Size Effects – Slabs have a greater fatigue capacity than beams
Support – The beam test has a k-value for support of 0 psi/in.!
L/3Span Length = L
d=L/3
…versus…
Faulting Design in StreetPave
If dowels used, faulting mitigated & fails by cracks
No faulting data collected at the AASHO road test so model developed in 1980s using field performance data from WI, MN, ND, GA, and CA
Similar to cracking models, the pavement is made thicker, as necessary, until faulting model predicts that the pavement will not fail by faulting during the design life
Also “approved” in VA and many other state, city, and county engineers are using it in the U.S.
StreetPave used in design tables in:ACI 325 and 330 documents
Dr. Norb Delatte’s textbook Concrete Pavement Design, Construction, and Performance
Internationally, used in Australia, Portugal, Mexico, Uruguay, Argentina, Chile, etc.
StreetPave – Asphalt Design
Per Asphalt Institute’s MS-1
Reliability considered as modifier of soil strength (see ACPA’s R&T Update 9.01, “StreetPave’s Equivalent Design of Asphalt – Proof of the Accuracy of StreetPave’s Asphalt Module”)Failure predefined according to Asphalt Institute at 20% cracking in the wheelpaths
Comparison of Software
Example with ME Design “defaults”
JPCP w/ 6 in. (150 mm) crushed stone on a A-7-6 subgrade with defaults except subbase thickness
All traffic @ default values
Weather @ Chicago (ORD)
@ Phoenix (PHX)
Passes with 1.5” (38 mm) dowels
Example with ME Design “defaults”
Conducted WinPAS/AASHTO 93 and StreetPave designs alongside for comparison
Used “default” values from ME Design as inputs where possible
If ME Design variable not available, used typical “default”
In ME, also turned “Sealant” on and Erodibility Index to 2
For k-value, used ½ dynamic k-value to get static k-value
Increasing k-value Doesn’t Greatly Decrease the Required Thickness
Concrete pavement design thickness is relatively insensitive to support stiffness (modulus of subgrade reaction), so it is improper engineering to make a subgrade/subbase stronger or thicker in an attempt to decrease concrete pavement thickness…
Analyses conducted in StreetPave
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275
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325
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0 100 200 300 400 500
Req
uired Thickn
ess (mm)
Req
uired
Thickn
ess (in.)
Static k‐value (psi)
AASHTO 93 (ACPA WinPAS)
AASHTOWare Pavement ME @ ORD
AASHTOWare Pavement ME @ PHX
ACPA StreetPave
k-value Sensitivity
Very few designed for < 100
psi/in. (27
MPa/m)?
(136 MPa/m)
Get Your Software Loaded Up!Thank you.
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