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16 Some airport hubs have annual budgets set aside for repair and maintenance projects of their parking structures. Eight out of the 12 airports surveyed have established budgets for renewal ranging from $45,000 for cleaning, signage replace- ment, and minor repairs, to $5,000,000 for replacing deterio- rated caulk joints. However, all respondents with set aside renewal budgets only undertook work when there were reported issues or noted distress in the parking structures. Airport parking managers were queried regarding priori- tization of the following three factors in planning a renewal program: budget; level of service; and asset protection. Six of the 12 indicated that level of service was the most important factor, whereas the others identified asset protection as their priority. This reflects the peculiar characteristic of airport parking structuresâ being operated both as a customer-based service and as part of the airport infrastructure and major capital investment. Although budget appeared to be of lower priority at the surveyed hubs, the apparent low priority might be a result of the small survey sample size, and that only large and medium hubs were surveyed. According to Weant and Levinson 1990 (12), effective renewal planning would include both routine and preven- tive maintenance, and structural repair, rehabilitation, and restoration. ROUTINE AND PREVENTIVE MAINTENANCE Typical parking structures have expected service life of 40 to 50 years. Routine and preventive maintenance includes many activities that can be completed either quarterly or annually by in-house personnel. Resource materials have been pub- lished and are available from professional organizations such as International Parking Institute (IPI) on how to perform routine and preventive maintenance for airport parking struc- tures (7, 13â16). Sample annual checklists can be modified for specific airports. Such a structural checklist can be found as Appendix D. Survey respondents reported that airport parking opera- tors are aware of the benefits of performing routine and pre- ventive maintenance. For example, two respondents reported performing recommended regular wash-downs of the parking structures (13â15) at least every six weeks, and two others scheduled them semi-annually; whereas two more preformed them annually. This work item is especially necessary in northern climates where de-icing salts are brought into the facilities by vehicles with clinging snow. Table 2 shows the frequency of wash-downs among the survey participants. However, the level of maintenance was typically limited only to parking slab wash-downs and cleaning of drains. Only two airports reported programmatically addressing other maintenance items such as sealants, minor patches, or expansion joints. Other maintenance items are not regarded as unimportant, but are generally addressed on an as-needed basis. Budget A survey was conducted in 1990 of parking facility own- ers regarding costs of maintaining new and existing parking structures (7). The average annual maintenance costs for a new structure and a 20-year-old structure are shown in Fig- ures 13 and 14, respectively. Also listed in the tables are the common items that are included in the maintenance program. In addition to routine and preventive maintenance, the tables have a listing for âreplacement maintenance.â Replacement maintenance is defined as replacement costs of items that have reached their service life during the service life of the parking structures, such as revenue collection systems, drain- age systems, or lighting systems. The maintenance unit cost per area per year is useful in budgeting and developing the asset management plan for parking structures. Based on the information in Figures 13 and 14, the aver- age maintenance cost for a new parking structure is about $0.46/sq foot/year and the average maintenance cost for a 20-year old parking structure is about $0.58/sq foot/year in 1990 dollars. Although the data was collected in the 1990s, the tables provide a template of different items to be included in the maintenance program. With that template, the average annual unit maintenance cost can be developed for any spe- cific parking structure based on its historical cost data base. STRUCTURAL REPAIRS, REHABILITATION AND RESTORATION The selection of a renewal approach should take into consider- ation the structureâs deterioration history; and repair alterna- tives (7). The maintenance cost history of a parking structure chapter four REPAIR AND MAINTENANCE APPROACHES
17 allows a deterioration curve to be developed by plotting the annual renewal costs versus time. Knowing where the park- ing structure is on the deterioration curve helps the engineer to design and plan a proactive renewal program. The restoration industry for concrete structures has been evolving rapidly in recent years. In 1996, Vision 2020 (17) was established under the Strategic Development Council of ACI. One of its 13 goals was to develop a repair code (18) similar to the building code for new structures. Since 2006, the repair code (ACI 365) has been developed and is expected to be adopted by the concrete industry in 2013. Once it is adopted, concrete repair guidelines will result in repairs with higher quality and durability. Wash Down Frequency Number of Participants Every 6 weeks or less 2 Semi-annually 2 Annually 2 Every other year 2 Greater than 2 year intervals 1 As needed or not planned 3 TABLE 2 SLAB WASH-DOWN FREQUENCY FIGURE 13 1990 Annual maintenance cost (new structure) [Source: Chrest et al. 2000 (7)].
18 The repair industry is also becoming more adept at extend- ing the anticipated service life of structures. New methods such as passive cathodic protection for embedded reinforce- ment bars have become readily available and successfully implemented in large restoration projects (18, 19). Better repair alternatives are available for parking structures as well. For example, in addition to the removal and replacement of concrete spalls, the use of denser high performance concrete, application of epoxy coating on reinforcement bars, use of corrosion inhibitor in the repair concrete, and installation of passive cathodic protection anodes can extend the life of the repair patches. The more layers of protection that are used, the longer the expected service life of the repair patches will be. Although the unit costs may increase with each additional protection, the repair durability increases proportionally, reducing the need for more frequent repair. An example of choosing a repair approach was reported by Shiu and Stanish (18). A project field investigation of a dete- riorated parking structure indicated that, over time, the rein- forced concrete floor slabs had been saturated with chloride ions. As such, the embedded reinforcing bars of the floor slabs were expected to corrode at an accelerating rate in the coming years. Localized patches did not resolve the ongoing corrosion deterioration inside the floor slabs. Routine patching resulted in spalls repair every four to five years. A more in-depth evalua- FIGURE 14 1990 annual maintenance cost (20-year-old structure) [Source: Chrest et al. 2000 (7)].
19 tion indicated that the continual demand for concrete slab repair could be mitigated with full slab replacement. A 20-year cost analysis was performed comparing full slab replacement with the ongoing slab repair at five-year intervals. The conclusion was that full-depth floor slab replacement not only represented a more cost-effective solution to the corrosion deterioration of the parking facilities, but also generated a higher service level with much less nuisance to the parking patrons. There is ongoing research (20) to understand and predict the anticipated durability offered by different concrete protec- tion systems. Currently, there is no definitive model accepted by the restoration profession (5). Engineers are using empiri- cal data from past experience to guide their repair design. In summary, exploring different approaches can yield more effective repair methods of improving asset protection and minimizing disruption.
