Below are the first 10 and last 10 pages of uncorrected machine-read text (when available) of this chapter, followed by the top 30 algorithmically extracted key phrases from the chapter as a whole.
Intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text on the opening pages of each chapter.
Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.
Do not use for reproduction, copying, pasting, or reading; exclusively for search engines.
OCR for page 22
23
TABLE 7
EXAMPLE LEVELS OF SERVICE FOR A MEDIUM-SIZE GENERAL AVIATION AIRPORT
WITH AC PAVEMENTS
Level of Service Minimum Acceptable Level of
Average PCI for all Sections Service
Facility Type Target or desirable Minimum acceptable PCI for Individual Sections
Runway 80 65 55
Taxiway 70 60 45
Apron 70 60 40
of service can also be defined in terms of other pavement sur- ment M&R treatments is shown in Table 8. The relationship
face defects such as rutting depth. shown in this table, developed for all key pavement dis-
tresses, is called a maintenance policy in MicroPAVER.
Trigger Levels
IDENTIFICATION OF NEEDS
In addition to using levels of service to estimate the need for
pavement M&R, trigger levels provide timing guidance for Identification of needs on the network level consists of the
pavement M&R treatments. An example of levels of service following four steps:
and trigger values is provided in Figure 13. Trigger values
may be general or treatment specific. 1. Identification of pavement sections that require M&R
treatments because of the level-of-service require-
General Trigger Levels General trigger levels provide ments or because of trigger levels.
guidance on what types of M&R treatments are considered 2. Selection of M&R treatments for the sections identi-
for a given pavement condition. For example, MicroPAVER fied in step 1.
enables the user to specify the PCI levels that trigger a reha- 3. Estimation of the costs for the implementation of
bilitation treatment. M&R treatments selected in step 2.
4. Prioritization of projects if the cost of the treatments,
Treatment-Specific Trigger Levels These trigger levels are estimated in step 3, exceeds the available budget. The
related to the need to apply a preservation treatment at the selection and prioritization of projects is done system-
right time to be effective, before the pavement reaches a con- atically and objectively using the procedures described
dition where a different, more expensive treatment would be in the next chapter.
needed. For example, sealing of cracks in AC pavements is
most effective when the pavement is still in very good con- Identification of needs is discussed separately for two
dition. An example of a trigger level for crack sealing and for time horizons:
an overlay is shown in Figure 13.
· Short-term planning for time horizons of about 5 years
Closely related to the concept of trigger levels is the link- or less. For simplicity, it is also assumed that the ana-
age between specific pavement surface distresses and the rec- lytical procedures used for short-term planning do not
ommended pavement M&R treatments. An example of the include the generation and evaluation of alternative treat-
linkage between pavement cracking and recommended pave- ments in future years.
· Long-term planning for time horizons of more than 5
years. In this case, analytical procedures can include the
Performance curve
100 generation and evaluation of alternative treatments in
future years.
Pavement Condition Index, PCI
Trigger level for crack sealing
Target level of service for average network condition
Short-Term Planning
Trigger level for overlay (mill and fill)
Many airports use short-term planning to identify and prior-
Minimum acceptable level of
itize pavement M&R needs. The typical procedure consists
service for individual sections
of the following steps:
a) Updating Pavement Inventory--Pavement inventory,
0 including pavement condition, is updated. The update
Pavement age, years
includes results of all recent pavement-related projects
FIGURE 13 Example of levels of service and trigger levels. and other changes to the pavement infrastructure.
OCR for page 23
24
TABLE 8
EXAMPLE OF MAINTENANCE POLICY FOR CRACKING
Recommended Maintenance Treatment
Severity of Pavement
Cracking AC pavements PCC pavements
Low None--continue to monitor None--continue to monitor
Medium Crack routing and sealing Crack sealing
High Crack repairs Full-depth repairs
b) Defining Scope of Work--Pavement preservation the M&R treatment. Figure 14 provides a summary of
treatments that can be planned at least a year in advance survey responses regarding the methods used for the
are included, whether corrective maintenance, preven- selection of M&R treatments. For example, about 85%
tive maintenance, or rehabilitation treatments. The treat- of respondents use engineering judgment and 30% of
ments may include, for example, sealing of cracks and the respondents use computer-based tools. Decision
joints, AC overlays, full-depth repairs of PCC pave- trees were used by about 6% of the respondents. How-
ments, and installation of subdrains. ever, engineering judgment often includes reasoning
c) Reviewing Pavement Preservation Needs for Each Air- that has the structure of decision trees.
port Pavement Section--One of the reasons for dividing The need for maintenance treatments, particularly
a pavement network into sections is to create future preventive maintenance treatments, is determined using
pavement repair units. Each section is considered in turn trigger values for individual pavement surface dis-
to decide if the section is expected to require any M&R tresses. For example, using the PCI pavement distress
work during the next 5 years, or during the given plan- evaluation terminology, the occurrence of joint seal
ning horizon. Many sections may not require any treat- damage at the medium or high severity triggers the
ment during the planning horizon, whereas other sec- need for joint sealing, and the occurrence of corner
tions may require preventive maintenance or other types break at the medium or high severity levels triggers the
of treatments. The decisions are based on the mandated need for full-depth patching with PCC. An example of
levels of service (Table 7) and trigger values such as the network-level maintenance plan generated by
those shown in Figure 13. The needs take into account MicroPAVER for the small airport shown in Figure 7
expected pavement deterioration during the planning is shown in Table 10. The exact extent of maintenance
period. The identification of needs is documentation of work is determined on the project level. For example,
the needs that are necessary on the basis of the levels of the existence of the 11 corner breaks was estimated by
service. sampling (and not by an actual field count) and verified
An example of pavement preservation needs for a by a detailed survey on the project level. Similarly, the
small airport (shown in Figure 7) is given in Table 9. size of the full-depth patches to repair the cracks needs
Table 9 was generated by MicroPAVER. In this exam- to be determined individually for each crack repair.
ple, the costs of the major M&R treatments depend on For localized M&R treatments, MicroPAVER uses
the PCI levels. The actual type of M&R treatments is maintenance polices that match the distresses with
not defined. M&R treatments (Table 8). Major M&R treatments are
d) Selecting Treatment Types--To refine the cost esti- identified as a function of the PCI level in terms of costs
mates, airport pavement maintenance managers select only (Table 9). Other software packages identify generic
TABLE 9
EXAMPLE OF 2009 5-YEAR MAJOR M&R PLAN FOR UNLIMITED BUDGET
Plan Branch Section Section Major
Year Name Number Area, ft2 Maintenance, $ M&R, $ Cost, $
2009 A01 10 48,000 0 238,000 238,000
20 46,000 49,400 0 49,400
THEAST 10 17,800 0 97,100 97,000
RW1533 10 205,600 0 945,900 945,900
2010 No work identified
2010 No work identified
etc.
5-year plan total 49,400 1,794,700 1,844,100
Source: Michigan Airports Division (2007).
OCR for page 24
25
100 60
Percent of respondents
Percent of respondents 75 40
50 20
0
25
Yes Budget No Have dedicated
permitting preventive
0 maint. budget
s
Identification of preventive maintenance treatments
am
sts
ns
es
t
t
t
ie
irs
en
en
tre
rit
io
xi
gr
f
m
gm
io
at
e
on
ro
ve
on
r
rd
er
d
p
iti
rp
pa
FIGURE 15 Systematic identification of preventive
isi
ju
za
id
l
nd
na
te
ec
ns
g
ha
of
in
pu
co
tio
maintenance needs.
D
co
ge
n
er
m
he
st
ra
er
ne
A
Co
or
pe
W
th
gi
W
O
O
En
Selection of treatments
· What will be the condition of the pavement network
FIGURE 14 Methods used to select M&R treatments 10 years from now given the existing budget?
on the network level.
· What is the future funding to achieve a specified level
of service?
· How much additional funding will be needed in the
treatment types; for example, an AC overlay, and the future to compensate for reduced funding now?
corresponding cost of the generic treatment types. The · What would be the impact on the network condition of
actual treatment design, including the design of pre- diverting funds to preventive maintenance or lower-
overlay improvements, overlay thickness, and material cost treatments?
properties, is done on the project level. · What would be the impact of constructing new runways
e) Selection of Preventive Maintenance Treatments-- or taxiways on the pavement preservation budget?
About 56% of airports systematically identify pave-
ments that would benefit from preventive maintenance The accuracy of future funding requirements for airport
and 35% of airports do so when budget permits (Figure pavement maintenance depends on the reliability of long-
14). For comparison purposes, Figure 15 also shows that term prediction of pavement performance and the generation
33% of airports have dedicated budgets for preventive of feasible alternatives. Long-term planning and prioritiza-
maintenance. The existence of a dedicated budget for tion can consider, for each section, several treatment options
preventive maintenance is considered to be one of the in each analysis year. This results in a large number of pos-
prerequisites for timely, successful, and sustainable oper- sible combinations of program years and treatments for one
ation of preventive pavement maintenance programs. section alone.
Long-Term Planning The concept of generating alternative M&R treatments
for different years is illustrated for one pavement section in
Long-term planning for airport pavement maintenance needs Figure 16. For clarity, only two treatments (microsurfacing
can improve engineering and economic decision making by and overlay) and two analysis years (now-plus-3 years and
helping answer the following example questions: now-plus-9 years) are considered. Alternative 1 is microsur-
TABLE 10
EXAMPLE MAINTENANCE PLAN
Pavement Surface Distress
Branch Section
Name No. Type Severity Quantity Unit Maintenance Treatment Cost
A01 20 Corner High 11 Slab Full-depth patching with PCC $9,500
break
Linear Medium 150 Feet Crack sealing $400
cracking
Joint seal High 460 Slab Joint sealing $34,000
damage
Shattered High 4 Slab Full-depth patching with PCC $4,700
slab
Corner High 12 Slab Partial-depth patching with $800
spalling PCC
Total $49,400
OCR for page 25
26
Micro-surfacing Overlay
facing to be constructed 3 years from now. Alternative 2 is
100 an overlay to be constructed in year now plus 9 years, when
1 the existing pavement will reach the minimum acceptable
Pavement Condition Index
2
level of service.
Minimum acceptable service Sophisticated software generates and evaluates multiple
level treatment options. For the example shown in Figure 16 it
means generating the two alternative treatments (microsur-
facing and overlay) at two different years, and estimating
0 their life spans. The life spans of the alternatives and their
Now Now + 3 Now + 9 costs are used subsequently to select the most cost-effective
Pavement age, years alternative. This type of analysis has been carried out by
FIGURE 16 Pavement performance prediction for many highway agencies, but is not routinely done by airport
multi-year identification of needs. agencies.
