SANRAL Overload Damage Quantification Louw Kannemeyer

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SANRAL Overload Damage Quantification Louw Kannemeyer Powered By Docstoc
					SANRAL Overload Damage Quantification
          Louw Kannemeyer
      Pavement Damage



          •   Non-Traffic Associated Damage
               • Rainfall (Moisture) – Materials Strength Reduced
               • Ultra Violet Radiation – Ageing of Surface Materials

          •   Traffic Associated Damage
               • Axle Loads - Overloading
               • Tire Pressure – New Tire Technology




Slide 2
                         TRAFFIC ASSOCIATED DAMAGE
                                 Axle Loads - Control


      •   Axle Loads
           • Legal Limits
           • Effective Enforcement                               7,7 Tons
              • Network of Traffic Control
                   Centers                                       9,0 Tons
               •   Operated 24 hours 365 days
                   a year
               •   Zero Tolerance to offenders
               •   RTMC




Slide 3
                                                 Mantsole TCC – N1 North of Pretoria
                            TRAFFIC ASSOCIATED DAMAGE
                                         Tire Pressure


          • Tire Pressure
             •   Not Practical to Specify Legal Limits
                   • Technology Improvements Driven by
                     Quest for Economic Efficiency
             •   Improved Design Procedures & Materials
                 Through Research
                   • Accelerated Pavement Testing
                     (APT)
                   • Stress-In-Motion (SIM)
                                                             HVS VI+




Slide 4
                                                          Stress In Motion
      Toll Concessions - Background


      •   The risk associated with the damage caused by overloaded
          axles remain with the Implementing Authority – SANRAL
      •   Additional damage caused by overloaded axles impacts the
          concessionaire as follow:
           • Time-shift Costs: planned maintenance and rehabilitation actions have
               to be performed earlier than originally planned due to the higher
               number of axles applied, this results in the concessionaire having to
               secure funding earlier, which results in interest payments over longer
               period than originally planned,
           •   Additional Strengthening Costs: the additional axles due to overloading
               consume pavement structural life, resulting in additional strengthening
               required to ensure pavement lasts for the concession period.




Slide 5
         Overload Damage - Cost Recovery

         Actual field       Damage                                  Cost
          condition
             Load P     Determined by P and                     Cost recovery
                        pavement sensitivity
Overloaded
  portion

Legal portion
                                                            d              Compensation
                                                   P
                                                    
                                                    80 




                                               d
                                      L
                                                                         Toll
                                       80 




   Slide 6
      Methodology


      •   The approach is based on comparing the without
          overloading to the with overloading scenario, taking into
          consideration the load sensitivity of the specific road
          pavement structures on these road sections – based on
          published results
             - field observations will introduced complex construction related
             variables,
      •   Based on collaboration between various parties
          involved:
           • Concessionaires with his Technical Specialists
           • CSIR
           • Africon
           • Prof Christo van As
           • SANRAL


Slide 7
      Equivalent Damage Calculation: With Overloading

                              Axle load histogram                            Load equivalency




                                                                                                        LEFk
                                               Legal axle load
                                          ni
                                                                               Legal axle load



                                                                 x
          Axle counts




                                                    nl
                             n2




                                                                     LEF




                                                                                                 LEFl
                        n1                                nk




                                                                                      LEFi
                                                                            LEF2
                                                                           LEF1
                                  Axle load interval                           Axle load interval


          •AASHTO METHOD: Published values of load sensitivity for generic road pavement types
          according the AASHTO procedure used internationally,
          • SOUTH AFRICAN MECHANISTIC DESIGN METHOD (SAMDM): Mechanistic-empirical
          modelling using the South African Mechanistic Design Method
Slide 8
      Equivalent Damage Calculation: Without Overloading


                              Axle load histogram                            Load equivalency




                                               Legal axle load
                                          ni
                                                                               Legal axle load



                                                                 x
          Axle counts




                                                    nl
                             n2




                                                                     LEF




                                                                                                 LEFl
                        n1                                nk




                                                                                      LEFi
                                                                            LEF2
                                                                           LEF1
                                  Axle load interval                           Axle load interval


          Axle Load Histogram: Based on the actual measured traffic axle load data obtained to date using Weigh–-
          In-Motion (WIM) technology.

Slide 9
      Time Shift Costs
      Cumulative E80                       Date of effective policing




                       Current date, Dc     Date of shifted          Date of planned
                                          1st intervention, Ds      1st intervention, Dp
                                                                                            Time


                                                             Time shift of
                                                       1st   intervention, Ts
      Real cost




                                          Real cost of shifted      Real cost of planned
Slide 10                                  1st intervention, Rs       1st intervention, Rp
                                                                                            Time
      Additional Strengthening Cost

                               CALCULATION OF ADDITIONAL COST
                  ESAL
                                          Anticipated revised work
                                                    OR
                                      Estimated by AASHTO procedure
       Add E80s
       from 1st to 2nd
       intervention




           SN
           calibration



              Design                                                                 Date
                                Overload control   First intervention
                     Opening                                            Second intervention


Slide 11
Slide 12
Slide 13
Slide 14
Slide 15
Slide 16

				
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