Reconstruction as Deterioration Indicator for Operational Structural Performances of Bridge Materials

Abstract

This article presents analysis of deterioration indicators for a comparative quantification of the operational structural performances of bridge inventories. The analysis considers the various kinds of material in the entire database of the US National Bridge Inventory. The multi-criteria approach integrates the indicators of deterioration, considering diagnostic condition and life cycle to determine the equivalent operational structural performances. This study also uses reconstruction data to determine an additional deterioration indicator for performance. The proportional effort for reconstruction reflects the practical need to counter deterioration and preserve a required level of structural performance, under all circumstances. The presented addition of reconstruction performance provides a more comprehensive assessment of bridge performance. The results reveal the continuous efforts to maintain a relatively balanced performance adequacy at the national level within the prevailing funding constraints. Reconstruction performances are generally higher than deterioration trends (rate and pattern) performances, revealing that the constrained reconstruction efforts have difficulty to keep pace with the actual deterioration.

1. Introduction

US transportation legislations require an inclusion of national performance reporting in network management in order to secure proper performance [1,2,3]. Bridge investments also need to achieve performance targets that make progress toward the national goals of safety, structural condition, and system reliability [4]. While the legislation outlines a performance-based approach, the state of practice still lacks applicable measures on how to quantify, analyze, and control the structural performances of bridges and groups of bridges in a network [5].

To support the implementation of performance reporting, studies suggest quantitative evaluations of probabilistic satisfactory performance of bridge inventories [6,7,8,9,10,11,12]. To enable more objective decision-making in bridge design, construction, maintenance, renewal, and management studies suggest a comparative analysis of large populations of bridge categories [13,14,15,16,17,18]. Performance measures for prioritizing individual bridges were suggested as an improvement of the relative ranking of Federal Highway Administration’s (FHWA) sufficiency rating, based on safety (condition, live load, and special events) and functionality (geometry) [19]. Risk-based lifecycle engineering approaches also support structural performance analysis of deteriorating civil infrastructure systems under uncertainty [20,21,22,23]. Probabilistic approaches of bridge performance indicators consider the individual component and system levels for projecting statistically to the network level [6,7,8,9,10,11,12,13,14,15,16,17,18,24]. Generally, these suggestions consider the concept of performance as an improvement of condition assessment, structural evaluation, or sufficiency rating for individual components, bridges, materials, types, or due to the result of certain events, such as earthquakes.

Determination of performance indicators for bridge structures across European countries at the component, system, and network levels considered technical, sustainability, and socio-economic aspects [25,26]. Five groups of key performance indicators were identified: (1) safety, reliability, security; (2) availability, maintainability; (3) costs; (4) environment; (5) health, politics. These and other suggestions consider the concept of performance as an extension of existing evaluations to include additional aspects. Technical, environmental, social, and economic performance indicators in Bridge Management Systems (BMS) were identified and classified for use in the development of sustainable quality control plans [27]. Survival analysis was used to identify key performance indicators for network-wide structural health monitoring [28].

After nearly a decade since the legislation, these methodologies did not materialize into a complete, uniform, quantitative, and comparative evaluation for all bridges, categories, and any subsets. Therefore, these attempts are not ready for immediate implementation and do not comprehensively address the performance-based decision-making requirements.

The extreme diversity of bridge types and materials in a network yields a multitude of factors that require analyzing bridge performance by categories for decision making [29,30]. The US National Bridge Inventory (NBI) provides extensive data sets with the most appropriate diagnostic metric for assessing bridge performance indicators [31].

A series of studies on the NBI enabled a comprehensive and comparative operational structural performance evaluation of bridges at the national and state network levels and/or categories [32,33,34,35,36,37,38]. The approach considered the engineering diagnostic measures of structural deficiency and the objective of life-cycle expectancy [39]. The analysis considered the categories of kinds of material and types of structure in the NBI [40], using counts and deck areas of bridges, separately. The multi-criteria approach integrated the normalized performance indicators of condition, durability, longevity, and deterioration trends. As bridges become older, there is a backwards accumulation of proportional structural deficiency by bridge age. Therefore, the deterioration indicator considered the computational trends (rate and pattern) of this gradual accumulation of deterioration. Consistent with applied statistics, a sixth-order polynomial trendline averaged the known annual fluctuations in the NBI reporting. To determine the deterioration trends, the rate and pattern are measured on a straight line, yielding an overall average, while the accumulation over time is actually not linear. Thus, it is necessary to study and analyze simpler and more objective deterioration performance indicators.

2. Objective and Scope

This article presents a study on deterioration indicators for a comparative quantification of the operational structural performances of bridge networks by category. To improve deterioration evaluations of structural performance with additional diagnostic data, this study suggests an additional deterioration indicator based on NBI’s reconstruction report. The proportional and situational intervention effort for reconstruction reflects the practical need to counter deterioration and preserve a required level of structural performance, under all circumstances. The analysis evaluates and compares two deterioration indicators: (a) the accumulation of proportional structural deficiency by bridge age relative to the objective of life-cycle expectancy and (b) the proportional need for reconstruction. The multi-criteria diagnostic approach determines the overall equivalent structural performances, incorporating the deterioration performance indicators, using a balanced justification basis for weighting factors. The study considers the entire raw database of the US NBI to analyze all the kinds of bridge material by bridge counts and deck areas. Comparative and quantitative operational performances of bridge materials determine the relative need for improvements in order to increase the reliability and desirability. Long-term, continuous implementation of operational structural performance evaluation enables a comparative experience basis to forecast and improve structural performances with a predictive bridge management strategy and more sustainable bridges.

3. Reconstruction Performance

The NBI’s reconstructed bridge report provides empirical data for comparing the performances of bridge systems [41]. Basically, this data is qualitative, per se, since it is obviously affected by a series of local variables. Yet, from a comparative point of view, the behavior-based concept can compare network dependability for discrete bridge systems [42,43,44]. After all, any comparison of bridge network subsets, materials, or types is bound to include local and group-specific circumstances. Moreover, these variables are the comparative evaluation’s target for improvement. Thus, this data reflects the local qualities for multi-aspect comparative and quantitative analyses of performance. Ultimately, comparative characteristic data is the basis for the national performance evaluation required by the legislation with an intent to improve circumstantial aspects.

This operational data essentially reflects the actual situational capability and efforts to preserve bridges from deterioration, enables exploring an additional indicator for the overall deterioration, and thus provides a more comprehensive observation of structural performance. Although the reconstruction record is not directly diagnostic, it is the direct result of diagnostic engineering judgment of deterioration, while also reflecting comprehensively the financial and situational constraint realities. In addition to structural deficiency, some reconstruction projects occasionally include functional obsolescence. Yet, these cases are usually based on the financial justification to improve the deteriorating structure, as well.

The notion of bridge reconstruction can be associated to the comparative health performance assessment of diverse human populations by tracking their history of proportional need for medical (in this case, reconstructional) intervention to recover toward a required operational physical condition, following a critical level of health deterioration. Thus, the effort for reconstruction reflects the practical need to counter deterioration and preserve a required level of structural performance, extending the condition and life cycle. Even though health data is basically qualitative, comparative health performance assessment is effectively conducted to quantify, analyze, and identify local and group-specific variables for improvement. The reconstruction effort comprehensively includes the actual engineering, management, resourcing, and local realities, practices, capabilities, and the entire spectrum of circumstances along the way. Thus, multi-aspect comparative and quantitative analyses of performance can identify critical variables for improvement.

The NBI reconstruction report provides the separate counts and deck areas of bridges by year built, year reconstructed, and material type [41]. This reflects the proportional need for reconstructional intervention as a representation of deterioration and performance (

Table 1. Reconstruction performances of bridge materials by counts.

Kind Code	Material and/or Design	Reconstructed Count	Total Count	$\mathrm{Reconstruction} \mathrm{Performance}=1-\frac{\left(\begin{array}{c}reconstructed\\ count\end{array}\right)}{\left(total count\right)}$
1	Concrete simple	22,983	177,805	0.871
2	Concrete continuous	9067	75,531	0.880
1 + 2	Concrete	32,050	253,336	0.873
3	Steel simple	25,066	130,947	0.809
4	Steel continuous	12,049	50,148	0.760
3 + 4	Steel	37,115	181,095	0.795
5	Prestressed/post-tensioned concrete (PC) simple	11,961	124,248	0.904
6	Prestressed/post-tensioned concrete (PC) continuous	1651	24,085	0.931
5 + 6	Prestressed/post-tensioned concrete (PC)	13,612	148,333	0.908
7	Wood/timber	3408	21,469	0.841
8	Masonry	477	1699	0.719
9	Aluminum/iron (Al/iron)	159	1558	0.898
0	Other	57	261	0.782
All	All	86,878	607,751	0.857

for bridge counts and

Table 2. Reconstruction performances of bridge materials by areas.

Kind Code	Material and/or Design	Reconstructed Area	Total Area	$\mathrm{Reconstruction} \mathrm{Performance}=1-\frac{\left(\begin{array}{c}reconstructed\\ area\end{array}\right)}{\left(total area\right)}$
1	Concrete simple	7,337,678.09	35,883,038.47	0.796
2	Concrete continuous	6,688,016.15	32,619,135.96	0.795
1 + 2	Concrete	14,025,694.24	68,502,174.43	0.795
3	Steel simple	20,012,328.75	65,664,233.14	0.695
4	Steel continuous	22,032,169.24	89,982,218.12	0.755
3 + 4	Steel	42,044,497.99	155,646,451.26	0.730
5	Prestressed/post-tensioned concrete (PC) simple	10,226,667.08	93,143,438.92	0.890
6	Prestressed/post-tensioned concrete (PC) continuous	2,892,425.49	41,940,441.37	0.931
5 + 6	Prestressed/post-tensioned concrete (PC)	13,119,092.57	135,083,880.29	0.903
7	Wood/timber	441,002.73	2,654,957.68	0.834
8	Masonry	134,530.76	295,169.30	0.544
9	Aluminum/iron (Al/iron)	41,799.76	112,984.89	0.630
0	Other	23,848.79	128,447.07	0.814
All	All	69,830,466.84	362,424,064.92	0.807

for bridge deck areas). Considering the ratios of reconstructed count and area to the respective total count and area enables a comparison of the reconstruction performance. The ideal case of no reconstruction is identified with the value of 1.0, denoting satisfactory reconstruction performance. The worst-case scenario of reconstruction of all bridges is identified with the value of 0.0.

The reconstruction report reflects the reality of practically possible intervention efforts to preserve bridges from deterioration as operationally feasible within all the prevailing constraints, including local, temporary, and other situations. Thus, the reconstruction performance quantifies the extent of the applied annual effort—indicating the need, and thus, offers a comparative scale of the state of deterioration among the groups of a bridge network. Obviously, intervention efforts change over time and follow different patterns from the past. Therefore, long-term and continuous observation of the annual reconstruction provides a better overall comparative average of the deterioration over time.

4. Operational Structural Performance

Figure 1 shows the integrated indicators of operational structural performance. Representing the engineering diagnostic measure of structural condition, the condition performance considers the average percentage of structurally adequate (SA) bridges that are not classified as Poor (or structurally deficient—SD) from the total of bridges. Durability and longevity performances represent the objective of life-cycle expectancy for uninterrupted service life. The durability performance considers the average lifespan before a bridge becomes Poor (SD). The longevity performance considers the average lifespan potential through renewal(s) beyond routine interventions. The deterioration trends represent condition versus service life over time: the deterioration rate and deterioration pattern performances consider the respective rate and pattern (curvature) of accumulation of the deterioration by bridge age.

The multi-criteria performance approach [32,33,34,35,36,37,38] can integrate the measure of reconstruction performance as an additional indicator of deterioration using an applicable weighting factor:

structural performance = ∑ (weighting factor × performance indicator)

(1)

Thus, including the indicator of reconstructional intervention, the equivalent structural performance and the respective weighting factors are:

$$P=w_c P_c+w_d P_d+w_l P_l+w_{dr} P_{dr}+w_{dp} P_{dp}+w_r P_r$$

(2)

$$w_c+w_d+w_l+w_{dr}+w_{dp}+w_r=1.0$$

(3)

where P = equivalent structural performance; P_c = condition performance; P_d = durability performance; P_l = longevity performance; P_dr = deterioration rate performance; P_dp = deterioration pattern performance; P_r = reconstruction performance; w_c = condition weight; w_d = durability weight; w_l = longevity weight; w_dr = deterioration rate weight; w_dp = deterioration pattern weight; and w_r = reconstruction weight.

A justification basis determines the weighting factors that also normalize the equivalent structural performances. Thus, performance values are defined to range from 0.0 to 1.0 for satisfactory performance. This analysis considers the logical engineering design consensus that condition and life cycle (durability and longevity) are equally important. Considering a balance between the corresponding criteria of structural condition (w_c) and service life cycle (w_d and w_l), while deterioration rate (w_dr), deterioration pattern (w_dp) and reconstruction (w_r) reflect both condition and life cycle, at the same time (Figure 1):

$$w_c+w_d+w_l=w_{dr}+w_{dp}+w_r=0.5$$

(4)

Considering a balance between structural condition (w_c) and service life cycle (w_d and w_l):

$$w_c=w_d+w_l=0.25$$

(5)

Considering a balance between durability (w_d) and longevity (w_l):

$$w_d=w_l=0.125$$

(6)

To reflect a balance between the performances of the deterioration trends (rate [w_dr] and pattern [w_dp]) and reconstructional intervention to counter deterioration (w_r):

$$w_{dr}+w_{dp}=w_r=0.25$$

(7)

Considering that the rate and pattern both reflect the deterioration trends:

$$w_{dr}=w_{dp}=0.125$$

(8)

Consequently, the equivalent structural performance that also reflects reconstruction is:

$$P=0.25 P_c+0.125 P_d+0.125 P_l+0.125 P_{dr}+0.125 P_{dp}+0.25 P_r$$

(9)

The method can accommodate various scenarios of weighting factor justifications for different engineering or management observations of performance. Such modifications can shift the emphasis of the observation between condition and life cycle. Yet, deterioration indicators (deterioration rate, deterioration pattern, and reconstruction) reflect both condition and life cycle, at the same time. Therefore, it is recommended to consider the balanced justification between condition and life cycle, in addition to the engineering design consensus.

5. Operational Structural Performance Evaluation

5.1. Bridge Counts

Table 1 shows that the reconstruction performance of PC (prestressed/post-tensioned concrete) bridges is the highest (0.904 simple, 0.931 continuous, and 0.908 total), followed by Al/iron (aluminum/iron) bridges (0.898), and concrete bridges (0.871 simple, 0.880 continuous, and 0.873 total). The lowest reconstruction performance is for masonry bridges (0.719), followed by continuous steel bridges (0.760). Overall, the average reconstruction performance of all bridge materials is 0.857. Figure 2 and Figure 3 help interpret the results of reconstruction performance.

To observe the difference of the contribution of reconstruction, Figure 2 compares the overall equivalent structural performances of bridge counts without reconstruction data (denoted as Equivalent 0), as originally evaluated in prior research, and with reconstruction data (denoted as Equivalent), newly evaluated now. Overall, the equivalent structural performances with reconstruction data are slightly higher for all materials and/or designs, except for other bridge materials.

To observe the difference between the deterioration indicators, Figure 3 compares the different contributions of deterioration trends (rate and pattern) and reconstruction. As expected, the reconstruction performances are rather higher: 0.86 compared to 0.68 for all materials and/or designs, except other bridge materials. The higher overall results including reconstruction indicate that the reconstruction efforts are lower than needed to keep up with the actual deterioration due to the existing constraints. The reconstruction performance of wood bridges is considerably higher than their deterioration trends, due to a reconstruction ratio nearly aligned with the average of all materials (Table 1).

Finally, reflecting the reconstructional intervention, the equivalent structural performances (Equation (9)) of the various kinds of bridge material and/or design by counts are shown in Figure 4. This comparison is for the same year as the NBI reconstruction report for 2013 made available in 2019 [41]. The equivalent structural performances are shown as horizontal thick black lines. The highest equivalent structural performance is for Al/iron bridges (0.92), followed by other bridges (0.87). Al/iron bridges represent the diminishing iron bridges that are no longer being built and the somewhat increasing number of aluminum bridges since the mid-1970s [34]. The lowest equivalent performance is for wood bridges (0.62). Overall, the average equivalent structural performance of all bridge materials is 0.80.

Figure 4 also enables comparative observations of the different structural performance indicators. The durability performance of all bridges is quite low (0.64), followed by the deterioration rate performance (0.67). Comparing the most common bridge materials, concrete has the highest overall equivalent performance (0.83), followed by PC (0.79) and steel (0.75). Comparing their reconstruction performances, PC bridges have the highest value (0.91), followed by concrete (0.87) and steel (0.80). These comparisons show that PC bridges have higher reconstruction performance than concrete but lower overall equivalent performance. Thus, PC bridges require greater reconstruction efforts to increase their overall equivalent performance relative to concrete bridges.

5.2. Bridge Deck Areas

The analysis also considers the actual constructed capacity of bridge materials by using deck areas, as compared to plain bridge counts that are still common in bridge management. Bridge deck areas more objectively reflect the relative magnitude of deterioration, structural performance, and need for intervention resources.

Table 2 shows that the reconstruction performance of PC bridges is the highest (0.890 simple, 0.931 continuous, and 0.903 total), followed by wood bridges (0.834), other bridges (0.814), and concrete bridges (0.796 simple, 0.795 continuous, and 0.795 total). The lowest reconstruction performance is for masonry bridges (0.544), followed by Al/iron bridges (0.630). Hence, masonry bridges have most reconstruction. Overall, the average reconstruction performance of all bridge materials is 0.807. Figure 5 and Figure 6 help interpret the results of reconstruction performance.

Again, to observe the difference of the contribution of reconstruction, Figure 5 compares the overall equivalent structural performances of bridge areas without reconstruction data (denoted as Equivalent 0), as originally evaluated in prior research, and with reconstruction data (denoted as Equivalent), newly evaluated now. Overall, the equivalent structural performances with reconstruction data are slightly higher for most materials and/or designs.

To observe the difference between the deterioration indicators, Figure 6 compares the different contributions of deterioration trends (rate and pattern) and reconstruction. As expected, the reconstruction performances are typically higher: 0.81 compared to 0.68 for most materials and/or designs. The higher overall reconstruction results infer that the constrained reconstruction efforts are falling behind the pace of deterioration. Overall, the evaluation considering reconstruction data provides a complementary comparative insight reflecting all the actual circumstances.

Finally, reflecting the reconstructional intervention, the equivalent structural performances (Equation (9)) of the kinds of bridge material and/or design by deck areas are shown in Figure 7, for the 2013 NBI reconstruction report [41]. The highest equivalent structural performance is for other bridges (0.89), followed by Al/iron bridges (0.80). The lowest equivalent performance is for wood bridges (0.66). Overall, the average equivalent structural performance of all bridge materials is 0.77.

Considering areas, Figure 7 also enables more objective comparative observations of the different structural performance indicators. The durability performance of all bridges is quite low (0.59), followed by the deterioration pattern performance (0.64). A comparison of the most common bridge materials (96.1% in 2015) [44] shows more comparable overall equivalent performances with relatively subtle differences (concrete 0.77, PC 0.74, and steel 0.73). Moreover, their continuous designs have the same overall equivalent performances (0.75). This also reveals that the simple span designs of steel (0.72) and PC (0.75) bridges need somewhat more attention than concrete (0.79). These average results demonstrate the continuous efforts of bridge officials to keep up with an optimal balance of bridge performance adequacy for the most common bridge materials at the national level within the prevailing funding constraints.

Comparing the reconstruction performances, PC bridges have the highest value (0.90), followed by concrete (0.80) and steel (0.73). Hence, PC bridges have least reconstruction. Nevertheless, the overall equivalent performance of PC bridges (0.74) is lower than concrete (0.77). Therefore, these results indicate that PC bridges have greater reconstruction efforts to improve their overall equivalent performance relative to concrete bridges. Consequently, the reconstruction performance of PC bridges will decrease but the other performance indicators will increase accordingly. Moreover, it is necessary to note that reconstruction efforts of PC bridges need a long-term plan to focus on particularly improving the relatively low durability (0.39) and deterioration pattern (0.35) performances, even though the condition performance is highest (0.97).

To observe the correlation between deterioration and service life cycle, Figure 8 shows the average ages of SD, all, and structurally adequate (SA—not SD) bridge areas of each material for the same year [38]. Each all age average is the centroid between its SD and SA areas. The range to the centroid implies the ratio of SD and SA bridge areas and the comparative potential of durability. Further observation shows that PC bridges are younger (all age 24.95) by some 20 years than concrete bridges (all age 45.21). While PC bridges did not have a long enough service life as concrete bridges do to accrue longevity performance, it is apparent that increase in durability performance is necessary. Moreover, the relatively low average age of SD PC bridges (39.23) indicates the need to improve the design details and quality control of initial production and construction to become closer to the 75-year life expectancy before structural deficiency. Moreover, the SD age of continuous PC bridges (31.68) is lowest. To further narrow down on the critical bridges, it is possible to identify the particular age group(s) with early accumulation of deterioration by observing the distribution of SD bridge proportion over time [37].

Similarly, the reconstruction efforts of concrete and steel bridges (Figure 7) also need to focus on improving their relatively low durability performances (concrete 0.44, steel 0.52). Overall, the average of all bridges also shows the need for reconstruction efforts that focus on improving the relatively low durability (0.59) and deterioration pattern (0.64) performances, even though the condition performance is relatively higher (0.92).

6. Discussion

To sum up, using bridge counts, Figure 2 compares the overall equivalent structural performances without and with reconstruction data. Figure 3 compares the two deterioration indicators of deterioration trends and reconstruction. Figure 4 shows the final equivalent structural performances including the deterioration indicator of reconstruction. In comparison to the commonly used bridge counts, bridge deck areas provide more objective conclusions for improvement. Thus, Figure 5, Figure 6 and Figure 7 show the same comparisons using bridge areas. Comparison of the structural performances (Figure 4 by counts and Figure 7 by areas) shows that the performance indicators are distributed differently up to around 9% and the total equivalent structural performance is lower by nearly 10%, (0.80 and 0.77, respectively). Such differences are significant for improvement decisions. Lastly, using bridge areas, Figure 8 correlates between the diagnostic classification of structural deficiency and bridge age to provide operational conclusions on deterioration and service life cycle.

The presented approach enables a comparative quantification of the various structural performance indicators. The results enable a comprehensive analysis of specific bridge groups, ages, and other variables to help identify comparative needs for improvement of the particular performance indicators. Annual evaluations can reveal the comparative levels of improvement or worsening of the structural performances of bridge materials due to changes in design, construction, usage, deterioration, funding, maintenance, reconstruction, climate, etc. To support the performance-based investment approach required by the legislation [1,2,3], continuous long-term structural performance reports are necessary.

7. Conclusions

This study demonstrates the analysis of integrating the indicator of reconstruction into the structural performances of bridge materials in the US NBI. Reconstruction efforts reflect the actual situational need to counter deterioration and preserve required levels of structural performance. This conveys a more comprehensive comparative quantification of performance assessment, including the actual efforts to preserve bridges from deterioration under all circumstances. The results enable comparative analysis of operational performance indicators and support more objective opportunity assessment and risk-informed decision making based on better forecast.

Considering the more objective perspective of bridge deck areas, the most common bridge materials have shown comparable, equivalent structural performances with relatively subtle differences (concrete 0.77, PC 0.74, and steel 0.73), while their continuous designs have the same equivalent performances (0.75). Yet, the simple span designs of steel (0.72) and PC (0.75) bridges need some more attention compared to concrete (0.79). Overall, these average results reveal the continuous efforts to maintain a relatively balanced performance adequacy at the national level within the prevailing funding constraints.

The results show that reconstruction performances are generally higher than deterioration trends (rate and pattern) performances. This reveals that the constrained reconstruction efforts have difficulty in keeping pace with the actual deterioration. Considering bridge areas, PC bridges have the highest reconstruction performance (0.90), followed by concrete (0.80) and steel (0.73), which means PC bridges have least reconstruction. Yet, PC bridges have lower overall equivalent performance (0.74) than concrete (0.77). Hence, PC bridges require greater reconstruction efforts to improve their overall equivalent performance, particularly the relatively low durability (0.39) and deterioration pattern (0.35) performances. Moreover, the relatively low average age of SD PC bridges (39.23) indicates early accumulation of deterioration, albeit the condition performance is the highest (0.97). Concrete and steel bridges also need reconstruction efforts to improve relatively low durability performances (0.44 and 0.52, respectively). Overall, all bridges require reconstruction to improve durability (0.59) and deterioration pattern (0.64) performances, while the condition performance is relatively high (0.92). A proper observation of the presented results enables a comprehensive analysis of the various structural performance indicators of specific bridge groups and ages and indicates objectively their comparative needs for improvement.

The approach can also accommodate additional performance indicators with applicable criteria and justified weighting factors to explore further perspectives. The concept can be implemented for any relevant subsets in a network of bridges (nation, state, county, category, group, etc.) and incorporated in Bridge Management System (BMS) programs. The interconnected data sets can be readily combined across multiple agencies, ultimately resulting in a more meaningful and universal data basis for bridge performance. Thus, the practical results help address problems faced by bridge officials in quantifying comparative operational performance in order to improve or preserve. Long-term, continuous implementation of this approach enables a detection of the periodic variations and a prioritization of the relative needs more objectively within constraints. The comparative experience basis helps to optimize control of deterioration, improve structural performances, and forecast resource needs. Overall, the study helps incorporate performance concepts and strategies in planning more sustainable bridges.

Countries and/or localities that definitely do not have a comparable bridge inventory database obviously cannot use the suggested methodology to obtain such a comprehensive performance basis. Nevertheless, even a partial operational database that is only occasionally updated can still be used with the suggested methodology. This will enable a projection of a probabilistic estimate of the overall performances. The results can also guide the direction for continued efforts of the limited data collection options, in order to improve the statistical representation of the partial database for the next round.