Long-term Maintenance of Culverts Jay N. Meegoda 1 1 Department of Civil & Environmental Engineering New Jersey Institute of Technology, Newark, NJ 07102 Tel: (973) 596-2464, Fax 973-596-5790, e-mail: [email protected]Key Words: Culverts, condition assessment, reliability, user cost, inspection, repair, rehabilitation, and maintenance Word Count=7395 Number of Words = 6145 Number of Tables and Figures = 5 Date of Submission: August 1, 2012 Reviewing Committee: AHD10 - Maintenance and Operations Management TRB Paper Number: 13-XXXX TRB 2013 Annual Meeting Paper revised from original submittal.
Transcript
Long-term Maintenance of Culverts
Jay N. Meegoda1 1 Department of Civil & Environmental Engineering New Jersey Institute of Technology, Newark, NJ 07102 Tel: (973) 596-2464, Fax 973-596-5790, e-mail: [email protected] Key Words: Culverts, condition assessment, reliability, user cost, inspection, repair, rehabilitation, and maintenance Word Count=7395 Number of Words = 6145 Number of Tables and Figures = 5
Date of Submission: August 1, 2012 Reviewing Committee: AHD10 - Maintenance and Operations Management TRB Paper Number: 13-XXXX
TRB 2013 Annual Meeting Paper revised from original submittal.
Long-term Maintenance of Culverts Abstract According to the American Society for Civil Engineers more than 1.6 trillion dollars are needed to update the nation's mostly aging infrastructure through various bonds and public funds. However, there was a significant dissatisfaction with the manner the last stimulus funds were spent. This is partially due to unavailability of rational methods to allocate precious resources. There are significant advances in health monitoring and rating of transportation infrastructure including culverts. However, rational connection of the transportation infrastructure to maintenance expenditure is lacking, especially the long-term maintenance expenditure. Any maintenance expenditure should be justified such that net increase in the asset value should be less than the cost of rehabilitation, where the net worth of an asset should be based on performance rather than on book value. Also the justification for rehabilitation or replacement of transportation infrastructure including culverts should occur only if user cost of failure is comparable to the rehabilitation or replacement cost. In order to perform such analysis, the user cost of failure should be incorporated into the above analysis and this analysis should be performed based on the available and accepted rehabilitation technologies. In this manuscript such analysis is performed to develop a methodology for optimum long-term allocation of funds to maintain culverts. This procedure may be used for other transportation infrastructure.
Introduction
Over a trillion dollars is invested in the nation's mostly aging infrastructure through various bonds and public funds. Most of that is spent on new construction and replacement of old infrastructure. It can be convincingly argued that it would be more cost effective over the long term to spend a good portion of these investments in taking a proactive course in managing the maintenance processes of the infrastructure rather than waiting and being forced to merely reacting to disruptive incidences. The importance of a proactive maintenance management policy becomes more pronounced when considering a vital transportation system such as that of highways networks and bridges. This importance emanates from the fact that an unexpected failure of a component of one of these complex systems usually creates disruptions which could have cascading effects leading not only to havoc and its consequences of inconveniencies, but also to major economic effects requiring colossal expenditure to contain the damages incurred from such premature failures. Various maintenance treatments are employed by transportation agencies to slow deterioration and restore condition of pavements, bridges, culverts, signs and other physical assets. However, budget constraints and other factors have often led to delaying or eliminating the application of these treatments. Such actions are expected to adversely influence the condition and performance and lead to a reduced level of service, to early deterioration, and eventually to the need for costly rehabilitation or replacement. Analytical tools are currently available to quantify the consequences of delayed application of maintenance treatments for highway pavements, bridges, and other assets. However, processes for using these tools to demonstrate the potential savings and performance enhancement resulting from applying maintenance treatments
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at the right time and also optimum allocation of funds are not readily available. Hence research is needed to develop such process. This information will help highway agencies better assess the economic benefits of maintenance actions and their role in enhancing the level of service of transportation infrastructure. In addition, incorporating these processes in asset management systems would provide a means for optimizing the allocation of resources. This is a requirement in Phase II of Governmental Accounting Standards Board, Statement No. 34 (GASB 34) where public agencies are required to maintain or improve the overall condition state of their infrastructure systems with annual funding, where the minimum amount needed is provided by a comprehensive asset management system. A framework is described in this manuscript and subsequent developments should help concerned agencies and asset owners to better assess the benefits of maintenance actions and their role in enhancing the level of service of infrastructure systems. Therefore, in this paper a methodology is developed for optimum time and also optimum allocation of funds to rehabilitate or replace culverts based on performance and user costs.
The Framework In order to connect communities and to get people, goods, and services to market, United States must have a robust transportation system to ensure the sustainability of the transportation network. This is also an essential part of the foundation for a strong and competitive economy. For this reason, the government and states should be committed to evaluate transportation infrastructure priorities and in particular, the improvement of highways that connect rural and urban areas to improve the flow of industrial goods. Recognizing that the roads and bridges are integral part of the transportation system, one of government’s commitments is to put in place a plan to ensure the sustainability of the transportation system well into the future. The basis for the development of any plan to specifically address the road and bridge infrastructure needs is an asset management business model that takes into consideration a number of factors such as the age and condition of the highway network, various options for rehabilitation, asset deterioration characteristics, and performance targets. An asset management system should be used to analyze these factors and to select project priorities based on the best time to apply the most cost effective economical treatments. Asset management identifies how assets deteriorate over time and when is the appropriate time to intervene (rehabilitate) in order to avoid costly reconstruction of the asset. If transportation assets are treated at the appropriate time, a larger volume of other assets can be maintained while at the same time achieving higher network level performance. The Damage Function Underlying all of the above is the fact that damage is a logistic function dependent on load and environment, meaning that there are, for all practical and modeling perspectives, three damage rates (zones in Figure 1, a deterioration curve developed for culverts based on Weibull model by Meegoda et al, 2008): (1) the “time to initiation” zone where condition state or classification is above 70%, sometimes referred to the
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zone of forgiveness, when the damage rate is slow and the indices of damage are almost imperceptible, and preventive maintenance is ignored where condition state or classification is above 70%; (2) the “accelerated damage” zone where condition state or classification is between 70% and 30%, when the damage rate accelerates, and during which time the structural distress indices not only become visible, but literally accelerate before our eyes; (3) the “consolidated damage” zone where condition state or classification is below 30%, when damage is so bad – cracks becoming potholes, etc. – that the damage index pretty much stays the same. This phenomenon is pretty much the same for bridges and roads, except that the threat of total collapse has orders of magnitude more negative consequences than for culverts along the highways. The unit costs of intervention from zone 1 to zone 3 increase exponentially. The consequences of delayed maintenance from zone 1 to zones 2 and 3 are budgetary catastrophic, increasing by orders of magnitude, for example, from 1:5:10 for rural roads, and 1:10:30 for urban/metropolitan streets because of underground utilities.
Many experts agree that a significant portion of US infrastructure is in the “accelerated damaged” zone. Therefore, at this stage of deterioration if there is no serious effort to rehabilitate these aging infrastructures, they will reach a point where colossal investments will be required to recover them. In addition inadequate culvert maintenance could result in temporary roadway closure and considerable rehabilitation/replacement costs or worse. The total collapse of a culvert could pose a major safety risk to motorists and flooding. Just such a catastrophic failure occurred on the New York State Thruway (I-88) near Unadilla, New York on June 28, 2006. The New York State Police photograph shown in Figure 2 illustrates the damage to I-88 resulting from a total culvert collapse. Two truck drivers were killed when their rigs fell into the washout caused by heavy rainfall. I-88 was closed in both directions from Schenectady to Syracuse. The washout of all four lanes and center median was a result of a failed 30-foot diameter culvert just beyond Exit 10 interchange. The typical deterioration and condition state curve (see Figure 1, where the tD the design life of different culvert materials is listed in Table 1) which describe the deterioration of culverts is usually a function of age, or time in service. Age is a composite surrogate for environment-related data and axle-load related data. While age is fairly well correlated with environmental variables such as freeze index, salting, etc., it is not sufficient to qualify the deterioration and hence regular inspections should be performed and condition state of the infrastructure should be known for the proposed analysis. Consequences of Delayed Maintenance The consequences of delayed maintenance may be categorized as societal costs, each of which has different modeling and quantification challenges. These societal costs may be identified as agency cost– the cost to provide and maintain the asset in a serviceable condition; user cost of failure– the consequential costs to the customer of the level of service provided; and the external cost– the overall environmental fallout, including noise, air quality, vehicle operating cost, etc. These costs can be related to the condition of the road/bridge/culvert assets, with summation of total societal costs indicating an optimum (sustainable) asset condition, below which the assets or
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individual assets should not be allowed to fall. Note the suggestion that the optimum sustainable condition is at a high level, consistent with GASB Statement 34 concerning perpetuation. Decision to Repair, Rehabilitate or Replace Decisions to repair, rehabilitate, replace or simply do nothing for a given culvert depends of the condition state of the culvert. Table 2 (Meegoda et al., 2005) lists the rehabilitation options for concrete culverts based on the five condition states. Table 2 also summarizes the recommendations for rehabilitation and replacement of concrete culverts that are identified with respect to the five condition states subjected to culvert size and length. The proposed rehabilitation technique would upgrade the Condition State, hence enhancing the service life. For instance, those culverts in Condition State 3 are upgraded by adding a liner to Condition States 2. The proposed rehabilitation methods shown in Table 2 are based on culvert length and size. Culverts that are small to medium size (i.e. 6-12 inches and 1-3 feet diameter) pose a challenge during inspection and rehabilitation, and may require the use of robots. The rehabilitation of small to medium sized culverts in Condition State 3 is identified based on culvert length (i.e. whether L<25ft. or L>25ft.). This differentiation is made considering the long-term effectiveness of the recommended technique. Use of this table is illustrated with an example in the following section. Culvert Management Meegoda et al, 2008 developed a deterioration curve for culverts based on Weibull model and it is shown in Figure 1. Please note that proposed curve shown in Figure 1 only accounts the environmental deterioration and does not account for the impact of traffic if similar analysis is used for pavements of bridges. However, to account for the traffic Weibull model parameter could be replaced by a new terms + where accounts for the environmental deterioration and account for deterioration due to traffic. Based on the above deterioration curve one can perform best way to allocate resources for maintenance and a brief description is given below. Once the Condition States of culverts in the network is known, usually after inspection, the following financial information is required for culverts management decisions, where the following is known for the ith culvert in the system. Please note that external cost is not included in this analysis.
Number of culverts in the network (n where i=1,2,…, n) Age or date of installation with years inspected and cleaned (Ti) Year to be considered (t, where t=0 for the current year, and t=1 for the next year) Condition State of some of the culverts based on prior inspection Expected life (td or i) and variance (i) for each culvert. Cost of installation for each culvert, it is also assumed to be the same as cost of
replacement (Ai,t) Current value of the culvert after do nothing/rehabilitation/replacement (Bi,t) Cost of Circuitry (Ci,t)
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Cost of inspection for each culvert (Ei,t) Cost of rehabilitation for each culvert (Fi,t) User cost of failure for each culvert (Gi,t) User cost for each culvert (Hi,t)
Please note that the agency cost would be either Ai,t (cost of replacement) or Fi,t (cost of repair or replacement). However, one may also include inspection cost, but inspection is considered as routine to comply with federal requirements. In order to perform a cost estimate (to obtain Ai,t [cost or replacement], Fi,t [cost of repair or replacement] or Ei,t [cost of inspection]), market value will provide the best available measure of value capital in terms of unit costs. Estimation of cost of new installation or rehabilitation incorporates unit costs based on 2010 RSMeans, a national U.S. yearly heavy construction cost estimating book and Bid Express, an online information service for bidding provided by BidX.com (Meegoda et al., 2012). These unit cost values (New Jersey Department of Transportation (NJDOT) 72-itemized drainage restoration and repair contract the bid) could be incorporated into asset management system in order to estimate capital costs, asset worth, maintenance, repair and new construction costs. Such system could also include the current inflation rate and/or discount rate to obtain the current cost value. Assessing the user cost or financial risk associated with failure is the most challenging issue in effective management of culverts. Though it can be argued that the cost or risk associated with failure is independent of culvert length, it may depend on culvert size, geographic location, whether it is laid along roadway or across roadway, and the proximity to critical structures such as subways, hospitals and hazardous waste sites. The user cost is usually associated with culvert failures, such as due to flooding, roadway collapses and ensuing traffic delays and expensive repairs. The flooding and associated detours and collateral damage are difficult to quantify. Besides, such damage claims can be paid by insurance, and hence not included in this analysis. Hence the methodology developed includes only the roadway collapses and ensuing traffic delays and expensive repairs, which is applicable only for the culverts crossing highways. The NJDOT user cost manual describes the methodology to compute the use cost associated with the traffic delay due to extra travel time and extra travel distance. In addition to the above, once the culvert is failed it should be replaced with a new culvert. Hence the user cost developed (Hi,t) will be the sum of the current cost of installation (Ai,t) plus the cost of detour during replacement if the culvert crosses main roads (Ci,t). Hence Hi,t=Ai,t +Ci,t * Ui,t where Ui,t is binary variable (0,1) such that Ui,t=1 if the culvert is
crossing the road. As per the NJDOT user cost manual, the Cost of Circuitry (Ci,t) has two components, i.e., circuitry delay and circuitry vehicle operating cost. Before computing the actual road user cost, the delay time through both the work zone and detour (if applicable) must be known. Although the number of vehicles delayed through the work zone and/or the detour has been determined, the amount of delay can only be computed after knowing
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the work zone and/or detour lengths and the times through them. The circuitry delay is only computed when a formal detour route has been established. The delay time through the work zone and through the detour are computed in the same manner. In each case, the delay is determined by subtracting the time it takes to travel either the work zone and/or detour when they are present, from the time it takes to travel the same distance when they are not present. The circuitry vehicle operating cost (VOC) is also only computed when a formal detour route has been established. At this point, an overall added travel length per vehicle has been determined. The circuitry VOC is computed by multiplying the number of vehicles that travel the detour, the overall added travel length per vehicle, and the current VOC cost rate associated with driving the added distance. Meegoda et al, 2006 provides an example showing how to compute the Cost of Circuitry (Ci,t). In estimating the user cost of failure one should take into account several aspects, starting from the probability of failure of the given culvert, its location, and the consequences of such failures. Estimating Gi,t is another challenge and requires a focused research effort. At this juncture, in order to develop the framework for analysis and without loss of generality it is assumed that Gi,t is calculated based on user cost and the probability of failure, where Gi,t =pfxHi,t and pf is equal to the probability of failure. Please note that in CIMS pf value is assumed as equal to (1.0- [Condition Classification is defined as shown in Figure 1]/100). The objective of this research is to a) determine the optimum allocation of the current maintenance budget of $Zt, by identifying the culverts that are to be inspected, and those that are to be repaired, b) to estimate the minimum annual budget needed over a given planning horizon, and c) to comply with GASB-34 requirements. Also this analysis should be capable of making project level decisions to repair, rehabilitate, replace, or do nothing for a given culvert. The following section lays the ground rules for project and network level decisions. Project Level Decisions to Repair, Rehabilitate, Replace or Do Nothing It is expected that the regional and/or field offices maintain culvert records requiring inspection and rehabilitation/replacement. As stated before, yearly maintenance and rehabilitation work to be carried out in the current year is based on condition state of the culvert during the previous year. The decision to inspect, repair, rehabilitate, replace or do nothing depends on the current Condition State determined from culverts inspection. If the current Condition State of a culvert is unknown due to budgetary constraints the selection is somewhat different. Meegoda et al., 2006 provides example of following situations to obtain project level decisions.
Do nothing Inspect a culvert Repair a culvert Rehabilitate a culvert Replace a culvert
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It was observed form the culvert data that most culverts in condition state 1 require no action, those in condition state 2 may require minor repair and painting, while those in condition state 3 would require either repair or rehabilitation, condition state 4 would definitely require major rehabilitation and condition state 5 is slated for replacement. For each choice one should calculate the difference between Bi,t and Gi,t and select the option with the least positive value as the selection. If a culvert is repaired, rehabilitated or replaced, the user failure cost value should be based on the improved performance value of the culvert and not based on the book value as accounted by most asset managers. This is a unique feature of the proposed method. Similarly the current value of the culvert is the improved performance value of the culvert and not based on the book value by most asset managers. Based on the above one can see that do nothing is not a choice for a culvert of condition state less than 3. However, due lack of funds some culverts with condition state higher than 3 may be left without any treatment. If such occurs, the overall value of the network reduces, which is the case for most of our transportation infrastructure. Also, current practice would be replacement if a culvert needs action. There are currently many inexpensive and effective rehabilitation methods that would bring back transportation assets to almost new or condition state 1, and hence should be considered instead of replacement. Also, it is very expensive to replace culverts and with the cost of one replacement several other culverts can be rehabilitated to almost perfect condition. Hence such decision should be based on network level analysis as described in the section entitled “Network Level Decisions to Repair, Rehabilitate, Replace or Do Nothing”. To illustrate the project level analysis one example form our culvert database is given below.
A 30 year old 18 inch diameter reinforced concrete pipe with a section length of 350 feet along the highway was inspected and found to have a condition state of 4 (pipe #28 in Table 3). Based on the unit cost estimate it can be replaced for $33,640. With condition state of 4, it has 30% of original value. Hence its performance value is 0.3x33640=$10,092, whereas the book value, assuming a service life of 75 years (see Table 1) and straight line depreciation would be 33640X(75-30)/75=$20,184. The probability of failure of this pipe is 70%. Hence the user cost of failure for this pipe which is along the highway would be either $10,092*0.7=$7,064 or $20,184*0.7=$14,129 based on performance or book value respectively. Now based on Table 3 this pipe can be rehabilitated by slip-lining at a cost of $15,753 (with condition state 4 this pipe cannot repair). Once it is rehabilitated its condition state becomes 1 (see Table 2). Hence the rehabilitated pipe has a performance value of $33640*0.9=$30,276 or a book value of 14,129+15,753= $29,882. Now the probability of failure of this pipe is 10%. Hence the user cost of failure for this pipe which is along the highway would be either $30276*0.1=$3,028 or $29,882*0.1=$2,988 based on performance or book value respectively. Instead of rehabilitation this pipe can be replaced at a cost of $33,640 and there is no user cost of failure as it is new. However, based on cost comparison using both costing methods of performance or based on book value, the best option for this pipe would be to rehabilitate. Here, since the performance and book values of the rehabilitated pipe are similar best choice is the same based on two costing methods.
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However, for other pipes it may be different and the choice made based on performance is always better. Now the above analysis is performed for 40 different culverts in the database (assumed as the network) and the projected level decisions are listed in Table 3. Please note that none of the culverts are listed as Condition State 1, hence do nothing is not an option. Also note that it is not possible to rehabilitation or repair culverts in Condition State 5, it is not possible to rehabilitate culverts in Condition State 2, and it is not possible to repair culverts in Condition State 4. Network Level Decisions to Repair, Rehabilitate, Replace or Do Nothing The state DOTs are generally responsible in assessing recommendations made by regional and field offices on culvert inspection and rehabilitation/replacement, and these are to be examined and prioritized while adhering to budgetary allocations. These decisions should best utilize the funds allocated for the planning horizon, thus resulting in a net improvement in total network asset value. The following section presents a model that meets the aforementioned objectives. For a given budget $Zt, the model optimizes the network performance based on the stipulated maintenance policies. These policies are associated with incurred costs. The decisions to be made depend on the state of deterioration of culvert pipe and can be identified as cost of inspection Ei,t, cost of rehabilitation/replacement Fi,t, current value of the culvert after do nothing/rehabilitation/replacement Bi,t, and cost of no-action leaving it to deteriorate Gi,t, where t is the year in consideration. Hence the objective is expressed mathematically as:
where Xi,t, Yi,t are binary variables (0,1) such that Xi,t=0 if there is inspection and Yi,t=0 if there is rehabilitation/replacement.
Meegoda et al, 2006 provides examples of network level actions. Please note that the result of the network analysis performed by Meegoda et al, 2006 do not consider the minimum budget to maintain the overall condition state of the system. In that regard, a long-term strategy should be implemented such that net worth of network is either maintained or increased (specifically do nothing should be considered in the above analysis so that system value is maintained or improved). Such analysis is provided in the following sections. The network level optimization was programmed and the logic of that programming is given below. The pipe financial analysis starts by grouping pipe segments into a particular project. Users have the option to select some of the segments to be included in the optimal solution no matter how much they cost. After a project has been defined the financial analysis module will allow users to review the project input data where users are allowed to make changes to the input data. The pipe project optimization consists of four major components. The system will evaluate the input data set and summarizes its major attributions; such as how many pipe segments are in the project, the total capital cost are required, and how many are pre-fixed jobs as well as the minimum required capitals for these pre-fixed jobs. The developed program has two
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optimization options solve equations 1 and 2, a heuristic procedure, such as ‘catch-the-big-fish’, or the 0-1 implicit enumeration algorithm that accounts for all possible combinations of the decision variables and compares their resulting objective function values to determine the real optimal solution. The reason for two algorithms is that the real optimal solution for the integer program problem has a 2^N computational complexity. When N>15, the enumeration will exceed 32768 combinations. In order for detailed illustration of the above, 40 culverts listed in Table 3 are used as the network. Please note that the following analysis is performed assuming the current cost remain the same over future years or there is no inflation and cost of borrowing. However, the analysis could be refined to include the inflation and cost of borrowing. Referring to the 40 pipes listed in Table 3, the calculated total current value is $186,284 and would require $327,065 to repair, rehabilitate or replace. If all culverts are replaced with new, the total installation cost is $581,646, which can be assumed as total maximum worth of culvert network. Different agencies allocate maintenance budgets based on agency constrain and can vary from 1% to 10% of the network worth. If 10% of the network worth is allocated, this would yield a yearly fixed budget of $58,000. With such budget the culvert network can be rehabilitated within 6 years. In order to determine which culvert is rehabilitated or repaired the following procedure is used. The total number of pipes, in this case 40, must be identified in the network group and the yearly budget of $58,000 must be entered before searching for the optimal solution. It should be noted here that project level action on any culvert listed in Table 3 can be treated with $58,000. For the first year, the program selects 8 culverts out of 40 to treat which are shown in the solution report. Once those eight jobs are completed, they must be unchecked in the network group before proceeding to optimize the budget for the following year. For each year, jobs that occurred in the previous year must be unchecked before optimizing the budget for the current year. For the second year, 5 culverts out of remaining 32 are selected, the third year 5 culverts out of remaining 27, the fourth year 4 culverts out of remaining 22, the fifth year 6 culver out of 18 and during the sixth year, the remaining twelve culverts are selected. With a yearly maintenance budget of $58,000 all 40 pipes can be treated within a period of six years. If 5% of the total installation cost is set as the yearly budget, then $29,000 is the fixed budget. This analysis is much complicated than that for the 10% yearly budget as the yearly budget is lower than the treatment cost of some pipes. Again all of the pipes, in this case 40, must be identified as the network. Once the budget of $29,000 is entered, the program selects 4 out of 40 pipes for the first year. The second year 4 out of 36 pipes are selected, the third 5 out of 32 pipes, the fourth 5 out of 27 pipes, the fifth 4 out of 22 pipes, the sixth 6 out of 18 pipes, and the seventh 9 out of 12 pipes. During the seventh year, the total budget of $29,000 is not used up entirely, resulting in $10,032 unused. If $1,000 or greater are left over in the budget, then it is added to the following year budget of $29,000. So, for the eighth year, $10,032 is added to $29,000, resulting in a budget of $39,032. The program chooses 1 out of 3 pipes and $4,785 is left over. For the ninth year, money left over from the previous year is added, resulting in a
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budget of $33,785. However the program does not select any pipes to work on since there is an insufficient amount of money, therefore, rehabilitation or replacement of pipes does not occur that year. Since $33,785 was not used the previous year, it can be added to the current year, resulting in a budget of $62,785 for the tenth year. The program selects 1 out of 2 pipes and $10,116 is left. For the eleventh year, a budget of $39,116 is insufficient for the program to select; the budget for this year is added to the following year. During the twelfth and final year, a budget of $68,116 is sufficient in order to treat the final pipe. With the above 5% or 10% of the network worth allocated to improve culverts the overall condition of the network substantially improves over very short time of 12 or 6 years. Specifically the overall condition state of the network listed in Table 3 is changed from condition state 4 to a condition state of 2 in very short 6 or 12 years with yearly 10% or 5% of the network worth allocated to improve culverts. Typically maintenance budget of transportation agencies are 1% or less. Assuming conservative 1% of the network worth allocated to improve culverts and also assuming that pipe condition states remain the same without further deterioration, above analysis shows that it would take 60 years to fix all 40 culverts. However, during this long 60 years culverts are deteriorated along the curve shown on Figure 1. For instance metal pipes have a design life of 30 years and hence they need to be replaced with much durable material types. Therefore, with a smaller maintenance budget, the above analysis should include the calculation of updated condition states of all 40 culverts due to aging. To demonstrate aging of culverts the calculation of updated Condition State is performed for culvert #25 as shown below. The culvert #25 is a 60” diameter and 184’ long corrugated metal pipe with condition classification 30%. Hence based on Figure 1 the t/tD value is 1.16. Therefore, one could estimate the age of the culvert as 34.8 (1.16X30) years. Now after say 5 years t/tD value is 1.33 ((34.8+5)/30). For this updated t/tD value the new condition classification value from Figure 1 would be 16%. The calculation of updated culvert condition state is computationally intensive. Hence in this research updated culvert condition state is computed every five years after the above network optimization and then project level decision are taken to develop a new table. Then the network level optimization is performed. This is repeated 12 times to spend a total budget of $348,000. Now with yearly 1% of the network worth allocated to improve culverts, based on the above analysis of updated condition state of the culverts due to aging and network optimization the overall condition state of the network will change from condition state 4 to a condition state of 5 due to the delay in maintenance. This should be compared with 5% or 10% of the network worth allocated to improve culverts where the overall condition state of the network listed in Table 3 changed from condition state 4 to a condition state of 2. Therefore, with yearly 1% of the network worth allocated to improve culverts, overall condition state of the network will change from condition state 4 to a condition state of 5 even with the same maintenance expenditure now spread over 60 years. This would violate the GASB -34 requirement of maintaining the overall condition state of the network. Hence the minimum yearly maintenance expenditure for the culvert network shown on Table 3 to maintain the overall network Condition State is over 2% of the
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network worth. Above computation could be easily programmed into an asset management information system so that transportation agencies can compute the minimum yearly maintenance expenditure to comply with GASB -34 requirement of maintaining the overall condition state of the network.
Summary and Conclusions
It is cost effective over the long term to spend a good portion of transportation investments in taking a proactive course in managing the maintenance processes of the infrastructure rather than waiting and being forced to merely reacting to disruptive incidences. The GASB -34 requires transportation agencies to maintaining the overall condition state of the network. In order to compute the desired maintenance budget to retain the overall Condition State of the network, a framework was developed. This procedure is initiated with the inspection of all culverts in the network and rating the condition state of each culvert. In this research, culvert deterioration is defined based on the Condition States, and the assumption that life added through rehabilitation results in an upgrade of the Condition State. The reliability of the culvert is the probability that it will operate for a specific period of time, e.g., its design life, under its design conditions without a failure. The reliability of the culvert is model based on Weibull distribution to develop the culvert deterioration curve, which is the basis for this analysis. Then project level decisions to inspect, rehabilitate/replace, or do nothing is calculated based on the user cost of failure. Then network level optimization is performed with allocated annual maintenance budget to determine culverts needing inspection, repair, rehabilitation, replacement or do nothing. Then the procedure was developed to compute the minimum yearly maintenance expenditure needed to comply with GASB -34 requirement of maintaining the overall condition state of the network at the current level.
Acknowledgements
This research was sponsored by research contract from the New Jersey Department of Transportation project titled “Drainage Information, Analysis and Mapping Project.” The contents of this paper reflect views of the author, who is responsible for the facts and the accuracy of the information presented herein. The contents do not necessarily reflect views or policies of NJIT, NJDOT, or FHWA. This paper does not constitute a standard, specification or regulation. The author wish to acknowledge the efforts NJIT project members, Drs. T. Juliano, C. Tang, L. Potts, T. Marhaba, Q. Guo, and A. Borgaonkar, Mr. S. Liu, Mr. C. Bell and Ms. M. Kahn and the NJDOT project customers, Ms. Nancy Ciaruffoli and Mr. Alkesh Desai, project managers Ms. Stefanie Potapa and Mr. Paul Thomas, and also the contributions of Ms. Camille Crichton-Sumners NJDOT and Mr. Hadi Pezeshki, of FHWA.
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McNamee, P., Dornan, D., Bajadek, D., and Chait, E. “Understanding GASB-34’s Infrastructure Reporting Requirement,” A paper written for state and local officials who will be involved in efforts to respond to, and comply with, the infrastructure reporting requirements of GASB 34. Price Waterhouse Coopers, LLP October 1999
Meegoda, J. N., Juliano, T. M., Ayoola, M. G. and Dhar, S. K. “Inspection, Cleaning, Condition Assessment and Prediction of Remaining Service Life of Culverts”. Paper #04-4426, Proceedings of the 83rd. Transportation Research Board Meeting, January 2004.
Meegoda, J. N., Juliano, T. M., Ratnaweera, P. and Abdel-Malek, L. "A Framework for Inspection, Maintenance and Replacement of Corrugated Steel Culvert Pipes," Journal of Transportation Research Board # 1911, 2005, pp.22-30,
Meegoda, J., Juliano, T. and Banerjee, A. “A Framework for Automatic Condition Assessment of Culverts,” Journal of Transportation Research Board, #1948, October 2006, pp. 26-36
Meegoda, J., Juliano, T. and Wadhawan, S., “Estimation of the Remaining Service Life of Culverts,” Transportation Research Board, January 2008, Washington DC, Paper # TRB 08-1523,
Meegoda, J., Juliano, T. and Tang, C. “A Culvert Information Management System,” Transportation Research Board, January 2009, Washington DC, Paper # TRB 09-2024, Accepted for publication in the Journal of Transportation Research Board
Meegoda, J. N. and Abdel-Malek, L., “A Stochastic Framework for Sustainable Infrastructure-Application to Pipes and Culverts,” Transportation Research Board, January 2011, Washington DC, Paper # TRB 11-2848, CD-ROM
Meegoda, J. N., Juliano, T. M., Potts, L., Tang, C., Liu, S., Bell, C. and Marhaba, T., "Implementation of a Drainage Information, Analysis and Management System" Transportation Research Board, January 2012, Washington DC, Paper # TRB 12-1605, CD-ROM
Mills, D, "Asset Management and Reporting Systems," EFC/AWWA GASB 34 Workshop, February 19, 2002.
New York State Police Photographs, posted June 28, 2006, http://surewhynotnow.blogspot.com/2006/06/two-dead-in-i-88-washout-ny-state.html
TRB 2013 Annual Meeting Paper revised from original submittal.
Sewerage rehabilitation manual (IV edition), Vol. I Rehabilitation Planning, 2001
Figure 1 Deterioration Curve for Culverts Based on Weibull model (Meegoda et al, 2008)
Figure 2 Collapse of New York State Thruway (I-88) (New York State Police Photo)
TRB 2013 Annual Meeting Paper revised from original submittal.
Table 1 Expected Service Life for Culvert Materials (Sewer Manual, 2001)
Material Expected Service Life (years) Brick/Clay 150 Concrete 75 Iron Pipes 75 Corrugated Steel 30 Corrugated Aluminum 75
Table 2 Recommended rehabilitation techniques based on condition state for Concrete culverts (Meegoda et al., 2005).
TRB 2013 Annual Meeting Paper revised from original submittal.
Table 3 Culvert Information Used in Project Level Decision # Route Mile Post Condition
