Figure 5.3 Configuration of urban waste-water management system

Figure 5.3 Configuration of urban waste-water management system.

• Household drains for sanitary and storm-water sewage

• Street and common-area storm-water sewage collection (gutters, ponds, channels)

• Municipal sewer collector system for sanitary and storm sewage (sewer pipes or open channel ditches, manholes, pumps)

• Main sewers (pipes and ditches)

• Treatment plants

• Sludge facilities

• Disposal of treated water

Construction and M,R&R history should be included in the database starting with the original construction. This can be very efficiently achieved by establishing the following data pertaining to construction number (construction number 1 for original construction, construction number 2 and above for subsequent M,R&R work, etc.): construction type (original construction, M,R&R type); construction material (pri­mary materials used in the original construction and M,R&R work);

Construction number is used as a key identifier to represent any major work done that can significantly affect subsequent performance. All geometric data, structural data, materials data, and cost data should be linked to the specific construction number. Construction quality and variability affect the pavement condition; therefore, data variability should be recorded in the database if at all possible. The accumulation of all historical data, collected over time, provides the basis for assessing, developing, and calibrating performance models needed for life-cycle analysis.

The extent of geometry, structural, and material data can vary from a few mandatory items to many hundred items, depending on the infra­structure and the intended use of the data. These data items must refer to each construction number for a given section. The mandatory geometry data include overall dimensions, length, width, and thick­ness of primary components. Structural and material data should include, as a minimum, material type and dimensions of the primary load-bearing component, and a list of any other components and their material type. Project-level analysis may require more detailed data for each structural component. Examples of these data for a bridge, a road section, and a building are presented in Sees. 5.6, 5.7, and 5.8. Detailed examples of the scope of needed pavement structure and material data for pavements are available in many other references [Hudson 94. Uddin 93, Uddin 95, Zhang 94].

Cost history of new construction and M.R&R strategies is an impor­tant component of the inventory database. If a computerized mainte­nance bookkeeping procedure or maintenance management system already exists, then the past cost history can be electronically called up as needed. The cost history data can be used to develop average M,R&R unit-cost models for analyses ofM,R&R strategies. In addition, database files and subfiles should be developed to store unit costs of common M,R&R actions based on the past records and bid estimates, and other agency records or commercial sources, such as the Means cost estimate catalogues [Means 93]. The unit-cost database files should be updated periodically. These are primarily used to calculate agency costs for projecting the M,R&R budget of the owner agency.

User costs are also important, including costsof travel time, vehicle operation, traffic delay due to construction, user discomfort, accidents, excess costs due to disruptions and breaks in service, user fees and taxes. For road infrastructure, very comprehensive vehicle-operating costs models have been developed by the World Bank [Chesher 87, Paterson 92], Texas Research and Development Foundation (TRDF), and the "U.S. Federal Highway Administration [Zaniewski 82]. These are used in programs for network-level road-management systems, such as USER [Uddin 94]. Similarly, other examples of user costs can be cited for other types of facilities:

• Airports: Traveler's time cost and inconvenience due to inadequate auto parking, inefficient planning of ticket counters and gates, poor baggage-handling facilities; time cost to airlines because of delays to aircraft departures and arrivals to gates

• Water supply: Increased water bills to consumers because of unac­counted leakage; extra cost and inconvenience to consumers in case of loss of pressure and/or rationing of water supply

• Electric power supply: Consumer's lost productivity and loss to businesses due to outages and interruptions in power supply

• Buildings: Occupant's lost productivity and inconvenience due to inadequate lighting, inefficient air conditioning, poor air quality;

revenue losses to owners of rental properties

Environmental conditions generally affect the life and performance of infrastructure facilities. Environmentally induced stress can con­tribute to premature fracture of concrete and metal structures. These failures occur at stress levels considerably below design stresses and may cause serious property damage and threat to human life. According to Fitzgerald, the majority of water main breaks occur where the pipe wall has weakened, e.g., corrosion of cast-iron pipes [Fitzgerald 68]. Other examples of weakening and failures induced primarily by environmental factors are interruptions in water supply and loss of water due to leakage, frost heave of building and roads, and soil contamination due to leakage in underground fuel tanks. Corrosion-induced material degradation and reduced fatigue life are serious concerns for sewer mains and water mains [O'Day 84], cooling facilities at nuclear plants, steel and other industrial plants.

The conditions for environmentally assisted stress-corrosion crack­ing (SCC) and corrosion-fatigue cracking (CFC) are more probable in the case of heavy usage and in aging structures. Other forms of envi­ronmentally related cracking are hydrogen stress cracking and sulfide stress cracking.

These phenomena can drastically reduce the life of a structure, and reliable service-life predictions for susceptible materials are difficult to make, A common feature of each of these processes is subcritical crack growth, during which cracks grow from existing flaws or initiation locations and increase to a size at which catastrophic failure occurs [Sprowls 961. The fatigue strength of a given material may be significantly degraded in the presence of a harsh environment, as shown in Figure 5.4 [after Sprowls 96].

Seasonal variations of temperature and water can alter soil strength and surface or subsurface drainage characteristics and can have a direct impact on structure life and performance. It can also affect the selection and cost of M,R&R strategies. While there are many tech­niques for ensuring adequate or good drainage, the data characteriz­ing drainage is usually either in terms of a porosity or permeability value, or is subjectively recorded as good, fair, or poor [Haas 94].

Freeze-thaw conditions can significantly lower load-carrying capac­ity of pavements and break or disrupt water and sewer lines. For example, the appearance of potholes on roads and highways, a com­mon scene in the U.S. during the spring, is affected by freeze-thaw environmental action, as shown in Figure 5.5 [Minsk 84]. Occurrence of potholes on major roads in urban America is a hot news topic each spring because of thawing and weakening of pavement layers. An estimated 77,000 potholes in Baltimore and 125,000 in New York were repaired during the first four months of 1996 [CNN 96].

If the environmental conditions vary significantly across an agency's area of jurisdiction, a record of the local environmental con­ditions are needed to predict performance and aid in the selection of appropriate M,R&R strategies. Simple indexes of environmental con­ditions are often used, such as the maximum and minimum ambient temperatures, wind speed, Thomthwaite moisture index, freeze-thaw cycles, freezing index, seasonal rainfall, or an empirical "regional fac­tor" developed by the agency.

Performance of any facility is a function of its use, load history, or traffic. Information on usage and demand on the facility are required to predict performance and to assign priorities during the selection of M,R&R projects. For water and sewer facilities, the usual measure of usage is total quantity handled per day or year. Annual consumption of kilowatt-hours is a possible measure for an electric-power supply facility. For highway agencies, the average annual daily traffic (AADT), with a breakdown into percent passenger vehicles and per­cent trucks, is a common measure of the total traffic on the pavement section or bridge. Pavement performance modeling and bridge deteri­oration, on the other hand, require an estimate of the heavy vehicle traffic that generates the majority of the distress. For highway pave­ments, the total number of 80 kN (18 kip) equivalent single-axle loads (ESAL) can be used to estimate the vehicular load that the pavement or bridge has carried or is expected to carry.

Generally, usage data should be collected and recorded in the his­torical database using on-site instrumentation, such as flow meters, counters, scales at permanent weigh stations, weigh-in-motion equip­ment [TRB 86], and the application of appropriate demand-prediction models. Expected growth rates should also be included for such usage data. For airfield pavements, records should be maintained on the total numbers of movements of each aircraft type or class. Discharge flow of water or sewage should be recorded, if possible, on hydraulic facilities. In the case of bridges and buildings, volume usage and load­ing forces, such as dead and live loads, wind, and seismic forces, need to be considered.

5.3 Technologies for Inventory and Historic Data Collection

The technologies of data acquisition for infrastructure inventory items may be grouped into several classes:

• Transcription from "as-built" or "as-constructed" project records. The historical project record is the least expensive source of inven­tory information.

• Pedestrian observer visual survey, usually on a sampling basis. This is feasible for small-size facilities. It is also the best method to verity the information collected from other sources.

• Windshield surveys (moving observer visual survey). This method is relatively faster but yields only estimates; however, it enables greater coverage for a fixed budget.

• Photo or video logging has the advantage of permanent records. This method can be used for roads, airports, railroad tracks, sub­ways, sewers, large water lines, and other facilities. Subsequent data reduction by either manual or automated image-processing techniques is, however, required and costly.

• Automated measurements of geometrical and structural character­istics can be done efficiently on roads, railroad tracks, and pipelines and sewers.

• Weather records can provide simple, inexpensive environmental data.

" Nondestructive testing, such as ground-penetrating radar, magnet­ic resonance, acoustic emission, and wave-propagation methods, are sometimes useful.

Table 5.4 summarizes several methods and options. Table 5.5 iden­tifies methods available for field-inventory data collection on roads, parking facilities, railroads, and airports. The inventory data of phys­ical facilities are characteristics that generally do not change from year to year, and those items that do change are updated either on the completion of a project or on an annual basis. The major data col­lection effort is therefore the initial one, undertaken at the time of establishing the information system for the network.

fl) Transcription from '"as-built" or "as-constructed" engineering records, such as plans, quality-control documents, and accounting and project records. The infor­mation on costs and M,R&R history is always obtained from the past records.

(2)* Pedestrian observer visual survey, usually on a sampling basis, with manual

recording, audio or photographic recording, or electronic encoding (e.g., on a hand­held computer).

(3)* Windshield survey riding on a vehicle (moving observer visual survey) with manu­al recording, keyboard entry to computer-encoded memory, and audiorecording

(voice-recognition) to computer memory.

(4)* Video or 35-mm photo logging, with permanent recording on photographic film (usually 35 mm), cinematic film (usually 16 mm, sometimes 8 mm), video film, or optical disc. Subsequent data reduction is performed by either manual or auto­mated image-processing techniques.

(5) Automated on-hoard measurement of geometrical and structural characteristics.

(6) Weather records for environmental data gleaned from published data from local or national weather stations or on-line Internet sources, or site-specific instrumenta­tion and data loggers.

(7)* Nondestructive testing, such as ground-penetrating radar, magnetic resonance, infrared imaging, acoustic emission, deflection testing, and wave-propagation methods.

*May also be used for periodic condition surveys.

A more detailed inventory may be required at the project level for project design. Thus, the method selected for data acquisition depends on the purpose. Historical usage data is collected by in-ser­vice monitoring on a regular periodic basis. Well-organized environ­mental data with periodic updates are readily available from the National Oceanic and Atmospheric Administration [NOAA 94].

Once the section inventory and historical data elements are defined, the collection process begins. Depending on the sampling plan and the purpose, this task can be quick or time-consuming. Electronic data collection and transfer should be used. Agencies without a cen­tralized database may use hard-copy records and files of field-data collection. Much of the inventory information required is in historical records, but it must be automated.

Generally, the construction history begins with the as-built plans, which provide data on the layout, dimensions, and boundaries of the facility; materials used; and year of construction. In cases where the structure or facility has evolved over time or construction records are lost, such as old bridges, water and sewer facilities, and roads, it is necessary to rely on the recollection of experienced people to estimate the construction history. In some cases when the construction history is not available, physical measurements and a survey must be used to obtain information on dimensions and structure, including nonde­structive testing and coring or trenching to examine the underground structure. For about one-third of the bridges in the U.S. national bridge inventory, there is no information on foundation depth, but recently nondestructive wave propagation testing has been used to estimate this information [Aouad 96]. It is not necessary to have a separate field-investigation program to establish the construction his­tory. The data can be collected as part of a structural evaluation over time. For example, one agency worked with the utility company using a form that work crews filled in whenever they cut a trench across a pavement to capture the thickness and material type for each layer to feedback information [Haas 94].

Data should be collected and processed systematically using for­mats designed for ease of use and precise recording. Data processing in the office or the field should use a formatted data sheet or template to provide direct computer entry. A notebook computer carried into the field can provide a viable method of recording data. Procedures for quality control and quality assurance are needed to ensure data accuracy. Variability and accuracy should be estimated. For example, radar estimates of layer thickness are not nearly as accurate as actu­al measurements. On the other hand, a precise measurement at only one point is not an adequate sample to represent the time mean value for a large facility.

Dedicated staff are important for an IMS database development plan. To fully understand the capabilities/limitations of current technology, designated IMS engineers should have prior experience in related areas and/or should attend a short course on infrastructure manage­ment. Visits to and interaction with other agencies of comparable size can offer useful insight into system development. However, this can be a blind-leading-the-blind situation if the agency visited is not com­petent in IMS. On-going training of assigned IMS staff should be an integral part of any IMS development plan.

A bridge-inventory system diners from a linear facility, such as a road or a utility pipeline. A bridge can be considered to be one or more unique sections. It consists of several important groups of structural and func­tional or nonstructural components, as shown in Table 5.6 [Hudson 87]. In the structural bridge inventory, the three main data groups are deck, superstructure, and substructure. Figure 5.6 shows several major com­ponents of a typical bridge over a water crossing. The National Bridge Inspection Standards (NBIS) outlines a record of

Inventory data groups Number of data elements

Defense-importance ratings 7

Navigation and waterway 3

Safety inventory 8

Note: There are sixMJl&R historical variables in the NBIS database