Presentation on rating & strengthening of bridges @ jntu hyd by raghavendra

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Rating is evaluation of safe load carrying capacity of existing bridges. There are different systems for rating in the world. In India mainly analytical, load testing and correlation methods are followed. Rating has reduced economic burden on authorities for some time. Rating has provided people with direction for follow up actions such as repairs, strengthening rehabilitation. It is becoming preferable, both environmentally and economically to upgrade bridges rather than to demolish and rebuild them. Deterioration of bridges wear from environmental influences and from traffic loads require rehabilitation and renewal programs to maintain even current service levels on the bridge infrastructure network. Demands for high durability, longer service life, reduced maintenance cost and cost/performance optimized. This paper deals with the rating of bridges and different methods of strengthening with its world wide applications.

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Presentation on rating & strengthening of bridges @ jntu hyd by raghavendra

  1. 1. JNTU COLLEGE OF ENGINEERING, ANANTAPUR. PRESENTATION BY….R.RAGHAVENDRA K.MADHAVULUIII/IV B.Tech, Civil III/IV B.Tech, Civil
  2. 2. CONTENTS :1. SCOPE2. RATING METHODOLOGY3. PROCEDURE FOR RATING4. STRENGTHENING5. POSTING6. CONCLUSION7. REFERENCES
  3. 3. SCOPE : INTRODUCTION… RATING… NECESSITY OF RATING… LOADS FOR RATING… Poor quality * DEAD LOAD * LIVE LOAD * IMPACT
  4. 4. RATING METHODOLOGY: GLOBAL PRACTICES  LOADS  STRESSES  FATIGUE  DESIGN PHILOSOPHY RATIING SYSTEM  ANALYTICAL METHOD  CORRELATION METHOD  LOAD TEST METHOD
  5. 5. ANALYTICAL METHOD It is applicable when as built or contract drawings and specifications followed are available or when such drawings can be prepared by site measurements to an acceptable level of accuracy. CORRELATION METHOD This method is adopted when the safe carrying capacity of structure can be ascertained by correlating the sectional details of the DIFFERENT GRAPHS USED IN METHOD structure.
  6. 6. LOAD TEST METHOD It is applicable when no construction drawings and specification originally followed are available or when such details are not possible to be obtained an site.  PROOF TEST  FAILURE TEST VEHICLES FOR TESTING  Test vehicles are chosen such that they are the next heaviest vehicle than the predominant heavy load presently passing over the bridge.
  7. 7. Study all available data, Detailed field or Where drawing, etc. lab investigation • Mcap : Moment resistingCompute section capacity in moment and shear at selected location Assess capacity of selected section. reduction factor (η) • Vcap : Shear resisting Compute Mcap and Vcap capacity at selected section. Compute effect of all loads • MDL and VDL : Moment and other than live loads at selected shear of all loads other thanCompute MLL = ηMcap – MDLVLL = ηVcap – VDL At live loads at selected section. selected locations • MLL and VLL : Net resisting Compute maximum LL capacity minus effect due to moment and shear at selected locations all loads other than live loads. • MLL and VLL : maximum Compare Bridge rated For MLL ~ MLL corresponding IRC possible effect (moment and standard Live VLL ~ VLL Loading hear) including impact effect.
  8. 8. SPACING AND NUMBER OF VEHILES Closer spacing of vehicles in urban areas is a frequent possibility. Urban traffic is mixed and slow as against the heavy and fast traffic for which the rating is proposed and high impact percentage. SINGLE LANE BRIDGE SPACING Standard and heavy trucks 30 Mt Articulated vehicles 18.5Mt  DOUBLE LANE BRIDGE Double lane bridges are those with carriageway width above 5.5m and up to 7.5 m for all spans. Vehicle arrangement
  9. 9. PROCEDURE FOR RATING CALCULATION OF SAFE AXEL LOAD RATING OF BRIDGES (IRC S.P.67)CLASS FOUR SIX CLASS FOR MORE WHEELERS WHEELERS THAN 6 MAX. SINGLE MAX. WHEELERS AXLE LOAD SINGLE AXLE MAX. SINGLE LOAD AXLE LOAD 3R 1.1 t 1.0 t 30 R 14.0 t 5R 3.4 t 2.2 t 16.0 t 40 R 9R 5.8 t 3.5 t 17.5 t 50 R 12 R 7.5 t 4.8 t 19.0 t 60 R 18 R 10.0 t 7.6 t 20.0 t 70 R 24 R 12.0 t 8.5 t
  10. 10. STRENGTHENING :  ADDITION OF UNSTRESSED OR PRE-SRTESSED STEEL  INSTALLATION OF EXTERNAL PRE-STRESSED REINFORCEMENT  BONDED REINFORCEMENT  INCREASE OF THE CONCRETE CROSS-SECTIONCARBODUR CFRP PLATE SYSTEMS  IT CONSIST OF CARBON FIBER Material properties of carbodur CFRP plates E – Modulus Tensile Strength Elongation @ Break N/mm2 N/mm2 Carbodur S 165’000 2’800 > 1.7 Carbodur M 210’000 2’800 > 1.35 Carbodur H 300’000 1’350 > 0.45
  11. 11. BONDING OF CFRP PLATES : Test results Test Specimen Fbr [KN] Ybr [mm] Εbr Specimen 1 Curing 161 70 6.61 without oscillation Specimen 4 176 75 6.55Curing with oscillation
  12. 12. POSTING Posting is a method to restrict the loading on the existing bridge. CONDITION POSTING RATING > LOAD NOT REQUIRED RATING < LOAD REQUIRED TRAFFIC RESTRICTIONS 8 SPEED RESTRICTION 8 FOOT PATH LOADING 8 GEOMETRIC RESTRICTIION ALTERNATIVES TO POSTING 8 FRAME BARRIERS 8 FREQUENT INSPECTION 8 LANE LIMITS 8 REPAIR
  13. 13.  POSTING SIGN Regulatory signs are installed on either Side of bridge ENFORCEMENTRestrictions inrespect of Max.load, Geometricallimits, Speed forsafety of brides.
  14. 14. CONCLUSIO• N : Rating helps to determine the safe carrying capacity of bridges, thus the structure can be made safe for use.• Accidents can be avoided due to collapse of the old bridges which have undergone deterioration by posting.• Follow-up actions can be taken according the rating of bridge such as and this current or future loading on the bridge repairs strengthening or demolition of old bridge and construction of new bridge.
  15. 15. REFERENCES :* Bridge Engineering – D.R.Phatak* WWW.GOOGLE.COM* WWW.ALTAVISTA.COM* Public works department, Nasik* Indian Road congress, Special Publication 37
  16. 16. ?R.RAGHAVENDRA

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