REHABILITATION OF AN EXSITING BRIDGE USING POST TENSIONING

REHABILITATION OF AN EXSITING BRIDGE USING POST TENSIONING METHOD By PARIKH KALPESH

Overview Introduction Structural evaluation of the bridge deck, girders, abutment, and piers Recommended non destructive tests Short term solution Long term solution Detailing of the retrofit system Construction Sequence Cost benefit study Summary and Conclusion

Introduction General description of the bridge Bridge location Structural systems Non-Structural systems

Introduction…. . ……. . continued General description of the bridge Ø Bridge consist of two simply supported span, each of 50 ft. in length. Bridge location Ø Tioughnioga River Bridge is located over the mouth of the river in the Cortland city.

Introduction…. . ……. . continued

Introduction…. . ……. . continued Structural systems Bridge deck Ø Concrete deck with 7” thick with ordinary reinforcement. Ø 3 -3/8”reinforced concrete layer at the top Steel girder and diaphragms Ø Steel Girder: A wide flange structural steel beam, W 36 x 150 Ø Diaphragms: A steel member of 15” U @ 33. 9” Next Slide Shows the figure ……….

Introduction…. . ……………. . . continued

Introduction…. . ……………. . . continued Pavement Concrete Deck Steel Girder Bridge Abutment Steel Girder Bridge Pier • Abutments • Piers Bridge Abutment

Introduction…. . …………. . . continued Non-Structural systems Asphalt- Placement of asphalt has increased the dead load on the structural systems. It does not increase the Moment Resistance Bridge Railings- Metal railings have been used at the sides of the bridge deck Bridge bearings-Hinged Bearing at Pier Sliding Hinged Bearing at Abutment Construction Joints

Structural Evaluation of the Bridge Deck, Girders, Abutment and Pier Rating of Elements Steel Railing Rating – (5) Minor deteriorated Reason: Corrosion result from the environment. Curbs Rating - (5) Minor deteriorated Vertical cracking is noted at random locations throughout

Structural Evaluation of the Bridge Deck, Girders, Abutment and Pier…………. continued Concrete Deck Rating - (3) Seriously deteriorated and not functioning as originally designed. Reason: Corrosion of the rebar. Ø Top surface multiple transverse cracks Ø Exposing the material of steel Ø We deny adding additional dead load onto the deck. Expansion Joints Rating - (5) Minor deteriorated Reason- Fatigue and dynamic loading

Structural Evaluation of the Bridge Deck, Girders, Abutment and Pier…………. continued Drainage Systems on Super Structures Rating- (5) Minor deteriorated Longitudinal Beams or Girders Rating- (5) Minor deteriorated but functioning as designed. Reason- Corrosion Bearing Assemblies (Include Misalignment) Rating - (3) Seriously deteriorated Reason – Corrosion of the plate

Structural Evaluation of the Bridge Deck, Girders, Abutment and Pier…………. continued Concrete Abutments Rating– (3) Reason- Seriously deteriorated. Bridge Pier Rating-(3) Reason – Corrosion & deteriorated bearings. Conclusion The bridge elements that received a “Poor” rating includ concrete deck, the concrete abutments, steel plate girder bearings and the bridge pier. The overall condition of the bridge was rated as “ Seriously Deteriorated”.

Decision Making Needs Rehabilitation!

Recommended Non Destructive tests Non destructive test : For Overall Load Rating Load test Ø Moving Load test Static Non destructive test for Steel girder Ø Magnetic-Particle testing Ø Dye Penetrant test

Recommended Non Destructive tests … continued Non destructive test for concrete deck ØSounding tests (Hammer tapping) ØCover meter and Rebar locator ØConcrete Hardness test ØPetro graphic Analysis- To Identify ASR

RECOMMENDED NON DISTRUCTIVE TESTING ………. . continued. Conclusion for Non Destructive Test: Existing Bridge condition & Inspection Reports suggest that non destructive test is not required.

Repair Solution In 2001 evaluation and Inspection was made Long term solution opted In 2004 it should have been repaired It was decided to repair in Oct. 2013. Can we keep the Bridge without short term solution as it is now? Answer is Definitely NO! Short Term Solution & Long Term Solution are Required

Short Term Repair Solutions Wrapping of Carbon Fiber Reinforced Polymer (CFRP)

Short Term Repair Solutions contd. . Patching to exposed rebar in the deck

Short Term Repair Solutions contd. . Providing Steel Column Support near the Abutment

Short Term Repair Solutions contd. . Galvanic protection for steel girder

Long Term Repair Solutions Analysis and Design of a Retrofit System 1) Check for the adequacy of the existing bridge deck It is safe 2) Check for the adequacy of the Existing Steel Girder Existing steel Girder is Grade 60 Mu = 3327. 75 Kips-ft Stress = 79. 23 Ksi. > Fu Not safe and needs strengthening

Long Term Repair Solutions ……… continued External Post tensioning System Tendons are placed on the outside the cross section The forces transferred at the anchorages and at deflectors No bond is present between the tendon and the structure, except at anchorage and deflector locations

Long Term Repair Solutions ……………. continued Analysis and Design of a Retrofit System a) Design of post tensioning system i) Assuming e = 12” Fu = M/S + P/A where, M = MDL + MLL – P*e We obtain, Pu = 16228. 432 Kips # Of Tendons = 197 ( 0. 6 in diam. with area 0. 153 in 2 & fpu =270 Ksi Too large and hence increase eccentricity of the tendons

Long Term Repair Solutions ……………. continued ii) Assuming e = 57. 95” Fu = M/S + P/A Pu = 208. 24 Kips # of tendons = 4

Long Term Repair Solutions ……………. continued iii) Check for axial compression and flexure Eccentricity = 57. 95 in A pre stressing force of Pu =208. 24 Kips The steel girder is adequate for the combined effects of flexure and axial compression

Long Term Repair Solutions ……………. continued Final profile of the post tensioning system

Long Term Repair Solutions ……………. continued

Long Term Repair Solutions ……………. continued b) Design of connection H= 208. 24 Cos 9. 86 = 205. 16 Kips V= 208. 24 Cos 9. 86 = 35. 66 Kips 10 Bolts of A 490 X, 7/8 in diameter and nominal tensile strength Fnt = 113 ksi and nominal shear strength Fnv = 75 ksi, are enough

Long Term Repair Solutions ……………. continued The plates used are checked for Yielding failure mode Fracture failure mode Block shear failure mode Smallest of these values governs. Design strength is Φt Pn =1044. 818 kips

Long Term Repair Solutions ……………. continued Design of the Bearings Elastomeric Laminated Bearing for Structural Movement Size: 406 mm × 27 mm× 43 mm Structural Resistance Maximum dead load + live load (zero rotation) Maximum dead load + live load (full rotation) Shear Movement Allowed Shear Stiffness KN/mm Rotation about longer axis (1 rad/100 KN)

Construction Sequence Bolts and Plate Fixing: Tightening, Can be Snug Tight or Fully Tight. Installation Dywidag Custom Make Holding Unit by welding. Installation of Dywidag System: Ducts Installation Stressing Grouting

Construction Sequence Installation of DYWIDAG system for Driscoll Bridge

Cost Benefit Study Alternate Solution Proposal: Deck Reconstruction Proposal Consist of: ü Construction Area : 6000 ft 2 ü List of Activates was Prepared ü Cost of Labor ü Cost of Equipment ü Cost of Engineers and Management

Cost Benefit Study……………. Continued Miscellaneous Charges Security Charges Temporary Construction office Charges Commissioning Cost- 0. 3% of the project Contingencies 3% of the project Small tools cost is 0. 5% of project Cost After Job cleaning up is 0. 3% of project Cost

Cost Benefit Study……………. Continued The cost involved in the deck reconstruction makes the post tensioning method preferable

Summary and conclusion The slab deck needs repair both for short term and long term The abutments require an immediate repair The bearings shall be replaced The Steel beam girder shall be post tensioned using 4 tendons Details and bill of quantities are included in the report

QUESTIONS?