STUDY ON LIFE-CYCLE COST ANALYSIS BASED PAVEMENT

Transcription

1 Paper Nº ICMPA096 8th International Conference on Managing Pavement Assets STUDY ON LIFE-CYCLE COST ANALYSIS BASED PAVEMENT MAINTENANCE DESIGN METHODOLOGY Li Qiang 1*, Liu Gang 1 and Pan Yuli 1 1 Research Institute of Highway, MOT, P.R.China * Corresponding Author s li.qiang@rioh.cn ABSTRACT For many years in China, mainly due to the lack of relevant specifications, standards and practical technology for pavement maintenance design, the selection of maintenance treatments mainly relied on Engineers experience. To solve these problems, a research on maintenance design methodology for high-grade highways was carried out in 2007, sponsored by the Ministry of Transport of China. Since then, 250,000 km pavement condition data of country road network have been collected by use of self-developed high-speed road condition inspection system known as CiCS. Based on great amount of field survey data, systematic study and analysis were made of long-term pavement performance deterioration pattern and pavement distress diagnosis methodology. A life-cycle cost analysis based pavement maintenance design methodology, combined with a set of software (PORD) were developed, which including several pavement condition indexes, such as pavement distress, roughness, rutting, anti-skid resistance, and pavement structure strength. The newly developed methodology is characteristic of total process controlling of long term pavement performance through the pavement structural and functional design. Based on life-cycle costs analysis, it is also capable of selecting cost-effective maintenance treatments meeting with mechanical and service performance requirements. The pavement maintenance design methodology has been applied on practical engineering project with satisfactory results. KEY WORDS: pavement maintenance design, life-cycle cost analysis, pavement performance, pavement condition survey INTRODUCTION During the past 20 year s rapid development, there were great achievements of road infrastructure construction in China. Total length of the road network system reached 3.98 million km, including 73,000 km of expressway, playing an important role in the social economic development.

2 Li, Liu and Pan Construction & maintenance growth rate(1000km/year) More demand for maintenance work, priority being shift from construction to maintenance By the end of 2010, growth rate of pavement maintenance work became greater that that of construction First expressway built in 1988, construction speed up in 1998, reached peak time in 2006, to be completed in 2020, national expressway system Year FIGURE 1 Development trend of expressway construction and maintenance in China. The experience of developed countries has shown that when the peak time of road construction is over it will be certainly followed by a large scale road maintenance era, and road maintenance will be a long-term, continuous, never ending task (1). Now China is undergoing similar development pattern in its road system development, as shown in Figure 1. The year of 1988 saw the start of first expressway construction in the mainland, the expressway construction accelerated in 1998 under proactive financial policy, and the construction work reached to its peak time in It is expected that the national expressway network system will be completed in 2020, with total length of 85,000 km, which indicates a 30-year expressway development cycle. Meanwhile, the expressway maintenance work is increasing rapidly from scratch. According to average 5 10 year of major and moderate rehabilitation cycle, by the year of 2020, total major and moderate rehabilitation mileage will be up to 8000 km per year, and the maintenance work will be maintained over this level, reflecting a huge road maintenance market potential. There is no doubt that the priority of road development in China is shifting from large scale construction to ever growing maintenance. The Ministry of Transport attaches great importance to maintenance work, playing indispensable role to make sure safety, mobility of the road network system, with road maintenance R&D having been taken as part of sustainable transport development strategy. CURRENT STATUS OF MAINTENANCE TECHNOLOGY AND ITS APPLICATION Road maintenance technology in China is still at its initial development stage at the moment, with insufficient capacity to meet the demand, a bottle-neck for sustainable development. More efforts will need to be done to establish a complete, effective and efficient road maintenance system and some of the major issues will have to be addressed through systematic R&D to find out innovative solutions. Demand for Road Maintenance Technology According to the current status of road maintenance and management, the following four topic areas have been identified as major issues in need of solutions, based on comprehensive survey and study:

3 Paper Nº ICMPA096 8th International Conference on Managing Pavement Assets High-speed, accurate, and reliable road condition inspection and monitoring technology. Scientific road maintenance analysis and decision-making technology. Advanced pavement maintenance design technology. Energy saving and environmental friendly road maintenance materials and technology. The key technologies mentioned above are involved in the whole process of road maintenance and management. In this paper, we will present the current situations of the R&D in general and highlight the road maintenance design technology development in China. Existing Problems in Pavement Maintenance Design Compared with that in developed countries, the pavement condition deterioration rate in China is greater, with average pavement service life only about 35 50% of that in developed countries. In pavement maintenance design area, we still lack of specific practical technology and relevant specifications for asphalt pavement major and moderate maintenance design. At present the pavement maintenance design is based on the method under the design specifications for new asphalt pavement (2), which revealed a number of problems in technical and management aspect. Technical Aspect 1. Lack of clear maintenance design procedures. We have successfully developed a complete technology and equipment based on China Pavement Management System (CPMS). At present, however, we haven t established a complete technical system and design work procedures, from pavement condition inspection, distress diagnosis, maintenance decision-making to pavement maintenance design. 2. The pavement treatments selecting and maintenance design still relying on experience, usually would use two methods: a)restoration of original pavement structure; b)use of typical empirical structure. Maintenance design is lack of comprehensive recognition and knowledge of pavement damage mechanism and lack of pertinent selection of maintenance treatments. 3. Lack of pertinent indicators suitable for maintenance design. More rely on mechanical design method for major/moderate maintenance, the mechanical indicator of pavement deflection is in fact not suitable and the major acting force considered is too simple to be in line with actual complicated loading conditions. 4. Single pavement structure (semi-rigid base course and bitumen surface layer) would be adopted in maintenance design, lack of comprehensive considerations and quantitative assessment of multi-layered well matched pavement structure, drainage performance, subgrade condition and pavement performance such as distress, roughness, rutting, anti-skid performance etc. 5. Lack of long-term effectives and efficiency or life-cycle costs analysis based economic assessment for the maintenance design. Management Aspect 1. Two-stage design is usually used for maintenance engineering project: a) scheme design (preliminary design, at the inception stage to control funding and bill of quantities); b) construction plan design (detailed design, for engineering work). During the process of maintenance engineering project management, it is usually the case that the preliminary design is neglected.

4 Li, Liu and Pan 2. Lack of innovative design ideas, by following the specifications for newly built road, or even no design at all, simply meeting with the project owner s requirement and copy similar ones. Taking into consideration of the problems mentioned above, it is necessary and urgent to establish a complete set of design scheme, from objectives to final design scheme, plus effectiveness assessment, which is known as Pavement Maintenance Design and Comprehensive Assessment Technology System. Through the application of the complete set of maintenance design technology, it would be possible to extend the pavement service life-cycle, reduce life-cycle costs, reduce negative impact on road traffic caused by frequent road maintenance work, and to improve road service level. PAVEMENT MAINTENANCE DESIGN METHOD A rational road maintenance analysis procedure may be classified into two levels, i.e. network level and project level (3), with each level including major activities and relevant technical support as shown in Figure 2. The main objectives of network level analysis are to identify overall maintenance demand, to put forward project proposals, and to work out rational maintenance plan and program. And project level maintenance analysis is concerned with implementation of specific maintenance engineering work for particular road section, through detailed survey and analysis of pavement distress, pavement performance and life-cycle cost analysis to set forth a set of maintenance treatment options and to eventually complete the maintenance work plan. Network Survey Condition survey & assessment (network level) CiCS High speed network inspection Network Level Long Term Program Maintenance Plan Long-term demand (Length/cost) Annual plan (priority order) Select project location/cost Preliminary proposal NetPMS Network decision making CMAP Comprehensive analysis Platform Detailed Inspection Traffic, distress, deflection, skid resistance, rutting pavement structure strength ORDiS Inspection for designed road section Distress Diagnosis Mark maintenance design unit, identify distress causes, determine nature of work CMES Maintanance Expert System Project Level Maintenance Design Construction Plan Design Based on analysis of pavement performance and life-cycle cost Bills of quantity, cost estimation, construction plan PORD Pavement Maintenance Design MCAD Graphs &Tables output Post Assessment Project implementation, project monitoring, effectiveness assessment FIGURE 2 Road maintenance analysis and design flowchart. The new concept and new method for pavement maintenance design proposed in this paper are mainly refer to

5 Paper Nº ICMPA096 8th International Conference on Managing Pavement Assets the second stage (project level) activities, in which there are two key elements in the design process. Total Process Control of Pavement Performance The ultimate criterion used for assessing pavement quality is pavement performance, in terms of indicators such as pavement distress, roughness, rutting, anti-skid resistance, structure strength and etc. It seems an inevitable development trend that the design of pavement structure and materials should be based on pavement performance analysis. What does it mean by pavement performance (4)? Pavement performance: means effectiveness or adaptability of road pavement conditions to meet different driving requirements, including functional performance and structural performance. Functional performance: means driving comfortableness, safety, fuel economy, environmental effects, and etc. Structural performance: means susceptibility to various pavement distress or damage, load bearing capacity. Cost Effectiveness Assessment in the Maintenance Design In the process of maintenance design, it is necessary and imperative to do economic analysis of each of the maintenance treatment options, by use of scientific analysis method life cycle cost analysis method, based on available technology and resource condition. What does it mean by life cycle cost analysis (5)? Life Cycle Cost Analysis (LCCA) is a management concept and method with objective to select most cost effective scheme from a number of options to achieve the lowest long-term cost of owned project, taking into account of total cost of the project, including initial cost: project design, etc.; on-going recurred cost: operation, maintenance, reconstruction, replacement, or total cost from inception to disposal of a project. While determining the maintenance treatment scheme, it is necessary not only to take into account of initial performance and costs, but also various costs and benefits in the life cycle period, so as to find out optimal investment scheme. To sum up, the maintenance design method based on pavement performance and life cycle cost analysis means to take into considerations of structure, materials, traffic loading, environment, and cost-effective, to achieve as far as possible the structural design integrated with materials design, the mechanical performance design integrated with pavement performance design, by use of the performance indicators combined with economic indicators. The economic indicator is taken as a condition for optimal solution, through life cycle cost analysis, to select not only technically feasible, to meet both mechanical and road use performance requirements, but also most cost-effective maintenance treatment scheme, including timing and treatment measures. Mechanical index is used to make sure that the whole structure will have sufficient strength. Performance index is used to make sure that pavement performance in the life cycle period will be maintained at or over the expected level, meeting with the design requirements for different class of road. Economic index is used to make sure that most cost-effective maintenance treatment scheme will be selected.

6 Li, Liu and Pan The above mentioned objectives will be eventually achieved by use of integrated pavement structure design and materials design, combined with scientific analysis method. KEY TECHNOLOGY RESEARCH AND APPLICATION To solve the problem in the maintenance design and to meet the urgent maintenance demand, the Ministry of Transport sponsored a R&D project of Study on Pavement Maintenance Design Technology for High-grade Highway in The project is to systematically study and analyze long-term pavement performance, pavement life cycle distribution pattern, pavement distress analysis and diagnosis, maintenance design method, and life cycle cost analysis method, aiming at establishment of a complete set of maintenance design technical system. So far a number of achievements have been gained, including practical maintenance design theory and method based on pavement performance and life cycle cost analysis having been put forward; and road condition inspection equipment, maintenance design software and guidance developed; all of which have been applied and tested in several actual engineering projects. Road Condition Inspection and Assessment Technology The first advanced multi-function road condition inspection equipment CiCS (Figure 3) has been developed and used in 18 provinces, collection road condition data with accumulated road mileage coverage over 250,000 km, playing important role in road maintenance design and management. Based on great amount of data collection, we have developed road condition assessment indicator system (Figure 4), put forward assessment method, assessment model and parameters suitable for each of the classified roads, which have been incorporated in Road Condition Assessment Standards issued by the Ministry of Transport, implemented across the country as of February 2008 (6). Based on the said standards, a guideline for road condition inspection for asphalt pavement maintenance design has been developed, including detailed design and inspection indicators suitable for project level maintenance design. FIGURE 3 CiCS Road Condition Inspection System.

7 Paper Nº ICMPA096 8th International Conference on Managing Pavement Assets PQI Pavement Quality Index PCI Pavement Condition Index RQI Riding Quality Index SCI Subgrade Condition Index MQI Maintenance Quality Index RDI Rutting Depth Index BCI Bridge Condition Index SRI Skidding Resistance Index TCI Facility Condition Index PSSI Structure Strength Index FIGURE 4 Road Condition Assessment Index. Long-Term Pavement Performance Tracking and Observation A long-term pavement performance tracking and observation program has been deployed in 18 provinces across the country (Figure 5), including road condition data collection, maintenance management and analysis, on the base of which a huge systematic network level time series pavement performance database (LTPP DataInfo) has been developed. Statistical analysis was made of the 4 years data from 250,000 km field survey, find the space-time distribution features of the performance data and the performance deterioration pattern of various typical pavement structures under different traffic conditions and different time span of the life cycle (Figure 6), with mathematic models having been developed to depict quantitative relations of various deterioration pattern. Through statistical analysis of historical pavement maintenance data of 92 expressways, 373 ordinary national and provincial trunk roads, we find various maintenance life cycle distribution patterns under different natural climate conditions, traffic volume and different maintenance treatment measures, on the base of which effective measures have been proposed to extend the maintenance life cycle. 18 Province,250,000 km 2007:11696 km 2008:56408 km 2009:77500 km 2010:98620 km JL HLJ NM BJ TJ LN SC NX SX HB SX HN HB SD AH JS ZJ GX GD FIGURE 5 LTPP Observation Coverage Areas.

8 Li, Liu and Pan FIGURE 6 Long-term Performance Tracking. Life Cycle Cost Analysis Based Pavement Maintenance Design Methodology The performance and life cycle cost analysis based pavement maintenance design methodology is characteristic of a complete set of design software (Figure 7), including life cycle cost analysis theory and relevant cost composition and forecast model, as well as comprehensive performance and structure indicators, such as pavement distress, roughness, rutting depth, skid-resistance, structural strength, and etc. The pavement maintenance design system based on pavement performance and life cycle cost analysis means to take into considerations of structure, materials, traffic loading, environment, and cost-effective, to achieve as far as possible the structural design integrated with materials design, the mechanical performance design integrated with pavement performance design, by use of the performance indicators combined with economic indicators. The economic indicator is taken as a condition for optimal solution, through life cycle cost analysis, to select not only technically feasible treatment schemes, to meet both mechanical and road use performance requirements, but also most cost-effective maintenance treatment scheme, including timing and treatment measures.

9 Paper Nº ICMPA096 8th International Conference on Managing Pavement Assets FIGURE 7 Pavement Maintenance Design System (PORD). Engineering Application To test the outcome achievements of the R&D project, two typical expressways (G035 Shi-Tai Expressway and G030 Jing-Shi Expressway) have been selected to demonstrate and test the design system, which has resulted in good effects. Figure 8 shows applications of the LCCA based pavement maintenance design methodology. ALT A ALT B LTPP Performance Criteria LCC (Millions )Analysis Period RSL Pavement Life(Year) FIGURE 8 Application of the Pavement Maintenance Design Methodology. CONCLUSIONS To some extent, pavement maintenance design is relatively complicated technical work, which would need strict specifications and requirements, from the design procedures and method to specific theoretical models and parameters. The RIOH has gained some initial achievements in this topic area, but more efforts will need to be made to further understand the current status and actual demand, through in-depth learning from international experience in developing more advanced maintenance design technology. We will continue to

10 Li, Liu and Pan work hard not only to meet the current demand but also to promote technological advancement in pavement maintenance design theory and practice to lead innovation and development in this topic area. REFERENCES 1. Haas Ralph, Hudson W R, and Zaniewski John. Modern Pavement Management. Krieger Publishing Company, Malabar, Florida, USA, Specifications for Design of Highway Asphalt Pavement. The Ministry of Transport, China, Kathleen T. Hall, Carlos E. Correa, and Samuel H. Carpenter. Rehabilitation Strategies for Highway Pavements. NCHRP Project C1-38, National Research Council, Washington, D.C., USA, Huang Y H. Pavement Analysis and Design. Prentice-Hall Inc, New Jersey, James Walls III, and Michael R. Smith. Life-Cycle Cost Analysis in Pavement Design. Publication FHWA-SA Federal Highway Administration, Washington, D.C., USA, Road Condition Assessment Standards. The Ministry of Transport, China, 2007.